creds/aws: Add support for DSA signature verification for EC2 (#12340)

* creds/aws: import pkcs7 verification package

* Add DSA support

* changelog

* Add DSA to correct verify function

* Remove unneeded tests

* Fix backend test

* Update builtin/credential/aws/pkcs7/README.md

Co-authored-by: Calvin Leung Huang <1883212+calvn@users.noreply.github.com>

* Update builtin/credential/aws/path_login.go

Co-authored-by: Calvin Leung Huang <1883212+calvn@users.noreply.github.com>

Co-authored-by: Calvin Leung Huang <1883212+calvn@users.noreply.github.com>

builtin/credential/aws/backend_test.go

@@ -1129,6 +1129,22 @@ func TestBackendAcc_LoginWithInstanceIdentityDocAndAccessListIdentity(t *testing
 			}
 		}
 
+		// Configure additional metadata to be returned for ec2 logins.
+		identity := map[string]interface{}{
+			"ec2_metadata": []string{"instance_id", "region", "ami_id"},
+		}
+
+		// store the identity
+		_, err = b.HandleRequest(context.Background(), &logical.Request{
+			Operation: logical.UpdateOperation,
+			Storage:   storage,
+			Path:      "config/identity",
+			Data:      identity,
+		})
+		if err != nil {
+			t.Fatal(err)
+		}
+
 		loginInput := map[string]interface{}{
 			"pkcs7": pkcs7,
 			"nonce": "vault-client-nonce",
@@ -1241,6 +1257,7 @@ func TestBackendAcc_LoginWithInstanceIdentityDocAndAccessListIdentity(t *testing
 		delete(loginInput, "pkcs7")
 		loginInput["identity"] = identityDoc
 		loginInput["signature"] = identityDocSig
+
 		resp, err = b.HandleRequest(context.Background(), loginRequest)
 		if err != nil {
 			t.Fatal(err)

builtin/credential/aws/path_login.go

@@ -20,13 +20,13 @@ import (
 	awsClient "github.com/aws/aws-sdk-go/aws/client"
 	"github.com/aws/aws-sdk-go/service/ec2"
 	"github.com/aws/aws-sdk-go/service/iam"
-	"github.com/fullsailor/pkcs7"
 	"github.com/hashicorp/errwrap"
 	cleanhttp "github.com/hashicorp/go-cleanhttp"
 	"github.com/hashicorp/go-retryablehttp"
 	"github.com/hashicorp/go-secure-stdlib/awsutil"
 	"github.com/hashicorp/go-secure-stdlib/strutil"
 	uuid "github.com/hashicorp/go-uuid"
+	"github.com/hashicorp/vault/builtin/credential/aws/pkcs7"
 	"github.com/hashicorp/vault/sdk/framework"
 	"github.com/hashicorp/vault/sdk/helper/cidrutil"
 	"github.com/hashicorp/vault/sdk/helper/jsonutil"
@@ -348,8 +348,8 @@ func (b *backend) parseIdentityDocument(ctx context.Context, s logical.Storage,
 
 	// Verify extracts the authenticated attributes in the PKCS#7 signature, and verifies
 	// the authenticity of the content using 'dsa.PublicKey' embedded in the public certificate.
-	if pkcs7Data.Verify() != nil {
+	if err := pkcs7Data.Verify(); err != nil {
-		return nil, fmt.Errorf("failed to verify the signature")
+		return nil, fmt.Errorf("failed to verify the signature: %w", err)
 	}
 
 	// Check if the signature has content inside of it

builtin/credential/aws/pkcs7/README.md

@@ -0,0 +1,5 @@
+# PKCS7
+
+This code is used to verify PKCS7 signatures for the EC2 auth method. The code 
+was forked from [mozilla-services/pkcs7](https://github.com/mozilla-services/pkcs7) 
+and modified for Vault.

builtin/credential/aws/pkcs7/ber.go

@@ -0,0 +1,251 @@
+package pkcs7
+
+import (
+	"bytes"
+	"errors"
+)
+
+var encodeIndent = 0
+
+type asn1Object interface {
+	EncodeTo(writer *bytes.Buffer) error
+}
+
+type asn1Structured struct {
+	tagBytes []byte
+	content  []asn1Object
+}
+
+func (s asn1Structured) EncodeTo(out *bytes.Buffer) error {
+	//fmt.Printf("%s--> tag: % X\n", strings.Repeat("| ", encodeIndent), s.tagBytes)
+	encodeIndent++
+	inner := new(bytes.Buffer)
+	for _, obj := range s.content {
+		err := obj.EncodeTo(inner)
+		if err != nil {
+			return err
+		}
+	}
+	encodeIndent--
+	out.Write(s.tagBytes)
+	encodeLength(out, inner.Len())
+	out.Write(inner.Bytes())
+	return nil
+}
+
+type asn1Primitive struct {
+	tagBytes []byte
+	length   int
+	content  []byte
+}
+
+func (p asn1Primitive) EncodeTo(out *bytes.Buffer) error {
+	_, err := out.Write(p.tagBytes)
+	if err != nil {
+		return err
+	}
+	if err = encodeLength(out, p.length); err != nil {
+		return err
+	}
+	//fmt.Printf("%s--> tag: % X length: %d\n", strings.Repeat("| ", encodeIndent), p.tagBytes, p.length)
+	//fmt.Printf("%s--> content length: %d\n", strings.Repeat("| ", encodeIndent), len(p.content))
+	out.Write(p.content)
+
+	return nil
+}
+
+func ber2der(ber []byte) ([]byte, error) {
+	if len(ber) == 0 {
+		return nil, errors.New("ber2der: input ber is empty")
+	}
+	//fmt.Printf("--> ber2der: Transcoding %d bytes\n", len(ber))
+	out := new(bytes.Buffer)
+
+	obj, _, err := readObject(ber, 0)
+	if err != nil {
+		return nil, err
+	}
+	obj.EncodeTo(out)
+
+	// if offset < len(ber) {
+	//	return nil, fmt.Errorf("ber2der: Content longer than expected. Got %d, expected %d", offset, len(ber))
+	//}
+
+	return out.Bytes(), nil
+}
+
+// encodes lengths that are longer than 127 into string of bytes
+func marshalLongLength(out *bytes.Buffer, i int) (err error) {
+	n := lengthLength(i)
+
+	for ; n > 0; n-- {
+		err = out.WriteByte(byte(i >> uint((n-1)*8)))
+		if err != nil {
+			return
+		}
+	}
+
+	return nil
+}
+
+// computes the byte length of an encoded length value
+func lengthLength(i int) (numBytes int) {
+	numBytes = 1
+	for i > 255 {
+		numBytes++
+		i >>= 8
+	}
+	return
+}
+
+// encodes the length in DER format
+// If the length fits in 7 bits, the value is encoded directly.
+//
+// Otherwise, the number of bytes to encode the length is first determined.
+// This number is likely to be 4 or less for a 32bit length. This number is
+// added to 0x80. The length is encoded in big endian encoding follow after
+//
+// Examples:
+//  length | byte 1 | bytes n
+//  0      | 0x00   | -
+//  120    | 0x78   | -
+//  200    | 0x81   | 0xC8
+//  500    | 0x82   | 0x01 0xF4
+//
+func encodeLength(out *bytes.Buffer, length int) (err error) {
+	if length >= 128 {
+		l := lengthLength(length)
+		err = out.WriteByte(0x80 | byte(l))
+		if err != nil {
+			return
+		}
+		err = marshalLongLength(out, length)
+		if err != nil {
+			return
+		}
+	} else {
+		err = out.WriteByte(byte(length))
+		if err != nil {
+			return
+		}
+	}
+	return
+}
+
+func readObject(ber []byte, offset int) (asn1Object, int, error) {
+	berLen := len(ber)
+	if offset >= berLen {
+		return nil, 0, errors.New("ber2der: offset is after end of ber data")
+	}
+	tagStart := offset
+	b := ber[offset]
+	offset++
+	if offset >= berLen {
+		return nil, 0, errors.New("ber2der: cannot move offset forward, end of ber data reached")
+	}
+	tag := b & 0x1F // last 5 bits
+	if tag == 0x1F {
+		tag = 0
+		for ber[offset] >= 0x80 {
+			tag = tag*128 + ber[offset] - 0x80
+			offset++
+			if offset > berLen {
+				return nil, 0, errors.New("ber2der: cannot move offset forward, end of ber data reached")
+			}
+		}
+		// jvehent 20170227: this doesn't appear to be used anywhere...
+		//tag = tag*128 + ber[offset] - 0x80
+		offset++
+		if offset > berLen {
+			return nil, 0, errors.New("ber2der: cannot move offset forward, end of ber data reached")
+		}
+	}
+	tagEnd := offset
+
+	kind := b & 0x20
+	if kind == 0 {
+		debugprint("--> Primitive\n")
+	} else {
+		debugprint("--> Constructed\n")
+	}
+	// read length
+	var length int
+	l := ber[offset]
+	offset++
+	if offset > berLen {
+		return nil, 0, errors.New("ber2der: cannot move offset forward, end of ber data reached")
+	}
+	hack := 0
+	if l > 0x80 {
+		numberOfBytes := (int)(l & 0x7F)
+		if numberOfBytes > 4 { // int is only guaranteed to be 32bit
+			return nil, 0, errors.New("ber2der: BER tag length too long")
+		}
+		if numberOfBytes == 4 && (int)(ber[offset]) > 0x7F {
+			return nil, 0, errors.New("ber2der: BER tag length is negative")
+		}
+		if (int)(ber[offset]) == 0x0 {
+			return nil, 0, errors.New("ber2der: BER tag length has leading zero")
+		}
+		debugprint("--> (compute length) indicator byte: %x\n", l)
+		debugprint("--> (compute length) length bytes: % X\n", ber[offset:offset+numberOfBytes])
+		for i := 0; i < numberOfBytes; i++ {
+			length = length*256 + (int)(ber[offset])
+			offset++
+			if offset > berLen {
+				return nil, 0, errors.New("ber2der: cannot move offset forward, end of ber data reached")
+			}
+		}
+	} else if l == 0x80 {
+		// find length by searching content
+		markerIndex := bytes.LastIndex(ber[offset:], []byte{0x0, 0x0})
+		if markerIndex == -1 {
+			return nil, 0, errors.New("ber2der: Invalid BER format")
+		}
+		length = markerIndex
+		hack = 2
+		debugprint("--> (compute length) marker found at offset: %d\n", markerIndex+offset)
+	} else {
+		length = (int)(l)
+	}
+	if length < 0 {
+		return nil, 0, errors.New("ber2der: invalid negative value found in BER tag length")
+	}
+	//fmt.Printf("--> length        : %d\n", length)
+	contentEnd := offset + length
+	if contentEnd > len(ber) {
+		return nil, 0, errors.New("ber2der: BER tag length is more than available data")
+	}
+	debugprint("--> content start : %d\n", offset)
+	debugprint("--> content end   : %d\n", contentEnd)
+	debugprint("--> content       : % X\n", ber[offset:contentEnd])
+	var obj asn1Object
+	if kind == 0 {
+		obj = asn1Primitive{
+			tagBytes: ber[tagStart:tagEnd],
+			length:   length,
+			content:  ber[offset:contentEnd],
+		}
+	} else {
+		var subObjects []asn1Object
+		for offset < contentEnd {
+			var subObj asn1Object
+			var err error
+			subObj, offset, err = readObject(ber[:contentEnd], offset)
+			if err != nil {
+				return nil, 0, err
+			}
+			subObjects = append(subObjects, subObj)
+		}
+		obj = asn1Structured{
+			tagBytes: ber[tagStart:tagEnd],
+			content:  subObjects,
+		}
+	}
+
+	return obj, contentEnd + hack, nil
+}
+
+func debugprint(format string, a ...interface{}) {
+	//fmt.Printf(format, a)
+}

builtin/credential/aws/pkcs7/ber_test.go

@@ -0,0 +1,62 @@
+package pkcs7
+
+import (
+	"bytes"
+	"encoding/asn1"
+	"strings"
+	"testing"
+)
+
+func TestBer2Der(t *testing.T) {
+	// indefinite length fixture
+	ber := []byte{0x30, 0x80, 0x02, 0x01, 0x01, 0x00, 0x00}
+	expected := []byte{0x30, 0x03, 0x02, 0x01, 0x01}
+	der, err := ber2der(ber)
+	if err != nil {
+		t.Fatalf("ber2der failed with error: %v", err)
+	}
+	if !bytes.Equal(der, expected) {
+		t.Errorf("ber2der result did not match.\n\tExpected: % X\n\tActual: % X", expected, der)
+	}
+
+	if der2, err := ber2der(der); err != nil {
+		t.Errorf("ber2der on DER bytes failed with error: %v", err)
+	} else {
+		if !bytes.Equal(der, der2) {
+			t.Error("ber2der is not idempotent")
+		}
+	}
+	var thing struct {
+		Number int
+	}
+	rest, err := asn1.Unmarshal(der, &thing)
+	if err != nil {
+		t.Errorf("Cannot parse resulting DER because: %v", err)
+	} else if len(rest) > 0 {
+		t.Errorf("Resulting DER has trailing data: % X", rest)
+	}
+}
+
+func TestBer2Der_Negatives(t *testing.T) {
+	fixtures := []struct {
+		Input         []byte
+		ErrorContains string
+	}{
+		{[]byte{0x30, 0x85}, "tag length too long"},
+		{[]byte{0x30, 0x84, 0x80, 0x0, 0x0, 0x0}, "length is negative"},
+		{[]byte{0x30, 0x82, 0x0, 0x1}, "length has leading zero"},
+		{[]byte{0x30, 0x80, 0x1, 0x2}, "Invalid BER format"},
+		{[]byte{0x30, 0x03, 0x01, 0x02}, "length is more than available data"},
+		{[]byte{0x30}, "end of ber data reached"},
+	}
+
+	for _, fixture := range fixtures {
+		_, err := ber2der(fixture.Input)
+		if err == nil {
+			t.Errorf("No error thrown. Expected: %s", fixture.ErrorContains)
+		}
+		if !strings.Contains(err.Error(), fixture.ErrorContains) {
+			t.Errorf("Unexpected error thrown.\n\tExpected: /%s/\n\tActual: %s", fixture.ErrorContains, err.Error())
+		}
+	}
+}

builtin/credential/aws/pkcs7/decrypt.go

@@ -0,0 +1,177 @@
+package pkcs7
+
+import (
+	"bytes"
+	"crypto"
+	"crypto/aes"
+	"crypto/cipher"
+	"crypto/des"
+	"crypto/rand"
+	"crypto/rsa"
+	"crypto/x509"
+	"encoding/asn1"
+	"errors"
+	"fmt"
+)
+
+// ErrUnsupportedAlgorithm tells you when our quick dev assumptions have failed
+var ErrUnsupportedAlgorithm = errors.New("pkcs7: cannot decrypt data: only RSA, DES, DES-EDE3, AES-256-CBC and AES-128-GCM supported")
+
+// ErrNotEncryptedContent is returned when attempting to Decrypt data that is not encrypted data
+var ErrNotEncryptedContent = errors.New("pkcs7: content data is a decryptable data type")
+
+// Decrypt decrypts encrypted content info for recipient cert and private key
+func (p7 *PKCS7) Decrypt(cert *x509.Certificate, pkey crypto.PrivateKey) ([]byte, error) {
+	data, ok := p7.raw.(envelopedData)
+	if !ok {
+		return nil, ErrNotEncryptedContent
+	}
+	recipient := selectRecipientForCertificate(data.RecipientInfos, cert)
+	if recipient.EncryptedKey == nil {
+		return nil, errors.New("pkcs7: no enveloped recipient for provided certificate")
+	}
+	switch pkey := pkey.(type) {
+	case *rsa.PrivateKey:
+		var contentKey []byte
+		contentKey, err := rsa.DecryptPKCS1v15(rand.Reader, pkey, recipient.EncryptedKey)
+		if err != nil {
+			return nil, err
+		}
+		return data.EncryptedContentInfo.decrypt(contentKey)
+	}
+	return nil, ErrUnsupportedAlgorithm
+}
+
+// DecryptUsingPSK decrypts encrypted data using caller provided
+// pre-shared secret
+func (p7 *PKCS7) DecryptUsingPSK(key []byte) ([]byte, error) {
+	data, ok := p7.raw.(encryptedData)
+	if !ok {
+		return nil, ErrNotEncryptedContent
+	}
+	return data.EncryptedContentInfo.decrypt(key)
+}
+
+func (eci encryptedContentInfo) decrypt(key []byte) ([]byte, error) {
+	alg := eci.ContentEncryptionAlgorithm.Algorithm
+	if !alg.Equal(OIDEncryptionAlgorithmDESCBC) &&
+		!alg.Equal(OIDEncryptionAlgorithmDESEDE3CBC) &&
+		!alg.Equal(OIDEncryptionAlgorithmAES256CBC) &&
+		!alg.Equal(OIDEncryptionAlgorithmAES128CBC) &&
+		!alg.Equal(OIDEncryptionAlgorithmAES128GCM) &&
+		!alg.Equal(OIDEncryptionAlgorithmAES256GCM) {
+		fmt.Printf("Unsupported Content Encryption Algorithm: %s\n", alg)
+		return nil, ErrUnsupportedAlgorithm
+	}
+
+	// EncryptedContent can either be constructed of multple OCTET STRINGs
+	// or _be_ a tagged OCTET STRING
+	var cyphertext []byte
+	if eci.EncryptedContent.IsCompound {
+		// Complex case to concat all of the children OCTET STRINGs
+		var buf bytes.Buffer
+		cypherbytes := eci.EncryptedContent.Bytes
+		for {
+			var part []byte
+			cypherbytes, _ = asn1.Unmarshal(cypherbytes, &part)
+			buf.Write(part)
+			if cypherbytes == nil {
+				break
+			}
+		}
+		cyphertext = buf.Bytes()
+	} else {
+		// Simple case, the bytes _are_ the cyphertext
+		cyphertext = eci.EncryptedContent.Bytes
+	}
+
+	var block cipher.Block
+	var err error
+
+	switch {
+	case alg.Equal(OIDEncryptionAlgorithmDESCBC):
+		block, err = des.NewCipher(key)
+	case alg.Equal(OIDEncryptionAlgorithmDESEDE3CBC):
+		block, err = des.NewTripleDESCipher(key)
+	case alg.Equal(OIDEncryptionAlgorithmAES256CBC), alg.Equal(OIDEncryptionAlgorithmAES256GCM):
+		fallthrough
+	case alg.Equal(OIDEncryptionAlgorithmAES128GCM), alg.Equal(OIDEncryptionAlgorithmAES128CBC):
+		block, err = aes.NewCipher(key)
+	}
+
+	if err != nil {
+		return nil, err
+	}
+
+	if alg.Equal(OIDEncryptionAlgorithmAES128GCM) || alg.Equal(OIDEncryptionAlgorithmAES256GCM) {
+		params := aesGCMParameters{}
+		paramBytes := eci.ContentEncryptionAlgorithm.Parameters.Bytes
+
+		_, err := asn1.Unmarshal(paramBytes, &params)
+		if err != nil {
+			return nil, err
+		}
+
+		gcm, err := cipher.NewGCM(block)
+		if err != nil {
+			return nil, err
+		}
+
+		if len(params.Nonce) != gcm.NonceSize() {
+			return nil, errors.New("pkcs7: encryption algorithm parameters are incorrect")
+		}
+		if params.ICVLen != gcm.Overhead() {
+			return nil, errors.New("pkcs7: encryption algorithm parameters are incorrect")
+		}
+
+		plaintext, err := gcm.Open(nil, params.Nonce, cyphertext, nil)
+		if err != nil {
+			return nil, err
+		}
+
+		return plaintext, nil
+	}
+
+	iv := eci.ContentEncryptionAlgorithm.Parameters.Bytes
+	if len(iv) != block.BlockSize() {
+		return nil, errors.New("pkcs7: encryption algorithm parameters are malformed")
+	}
+	mode := cipher.NewCBCDecrypter(block, iv)
+	plaintext := make([]byte, len(cyphertext))
+	mode.CryptBlocks(plaintext, cyphertext)
+	if plaintext, err = unpad(plaintext, mode.BlockSize()); err != nil {
+		return nil, err
+	}
+	return plaintext, nil
+}
+
+func unpad(data []byte, blocklen int) ([]byte, error) {
+	if blocklen < 1 {
+		return nil, fmt.Errorf("invalid blocklen %d", blocklen)
+	}
+	if len(data)%blocklen != 0 || len(data) == 0 {
+		return nil, fmt.Errorf("invalid data len %d", len(data))
+	}
+
+	// the last byte is the length of padding
+	padlen := int(data[len(data)-1])
+
+	// check padding integrity, all bytes should be the same
+	pad := data[len(data)-padlen:]
+	for _, padbyte := range pad {
+		if padbyte != byte(padlen) {
+			return nil, errors.New("invalid padding")
+		}
+	}
+
+	return data[:len(data)-padlen], nil
+}
+
+func selectRecipientForCertificate(recipients []recipientInfo, cert *x509.Certificate) recipientInfo {
+	for _, recp := range recipients {
+		if isCertMatchForIssuerAndSerial(cert, recp.IssuerAndSerialNumber) {
+			return recp
+		}
+	}
+	return recipientInfo{}
+}

builtin/credential/aws/pkcs7/decrypt_test.go

@@ -0,0 +1,61 @@
+package pkcs7
+
+import (
+	"bytes"
+	"testing"
+)
+
+func TestDecrypt(t *testing.T) {
+	fixture := UnmarshalTestFixture(EncryptedTestFixture)
+	p7, err := Parse(fixture.Input)
+	if err != nil {
+		t.Fatal(err)
+	}
+	content, err := p7.Decrypt(fixture.Certificate, fixture.PrivateKey)
+	if err != nil {
+		t.Errorf("Cannot Decrypt with error: %v", err)
+	}
+	expected := []byte("This is a test")
+	if !bytes.Equal(content, expected) {
+		t.Errorf("Decrypted result does not match.\n\tExpected:%s\n\tActual:%s", expected, content)
+	}
+}
+
+// echo -n "This is a test" > test.txt
+// openssl cms -encrypt -in test.txt cert.pem
+var EncryptedTestFixture = `
+-----BEGIN PKCS7-----
+MIIBGgYJKoZIhvcNAQcDoIIBCzCCAQcCAQAxgcwwgckCAQAwMjApMRAwDgYDVQQK
+EwdBY21lIENvMRUwEwYDVQQDEwxFZGRhcmQgU3RhcmsCBQDL+CvWMA0GCSqGSIb3
+DQEBAQUABIGAyFz7bfI2noUs4FpmYfztm1pVjGyB00p9x0H3gGHEYNXdqlq8VG8d
+iq36poWtEkatnwsOlURWZYECSi0g5IAL0U9sj82EN0xssZNaK0S5FTGnB3DPvYgt
+HJvcKq7YvNLKMh4oqd17C6GB4oXyEBDj0vZnL7SUoCAOAWELPeC8CTUwMwYJKoZI
+hvcNAQcBMBQGCCqGSIb3DQMHBAhEowTkot3a7oAQFD//J/IhFnk+JbkH7HZQFA==
+-----END PKCS7-----
+-----BEGIN CERTIFICATE-----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+-----END CERTIFICATE-----
+-----BEGIN PRIVATE KEY-----
+MIICXgIBAAKBgQDK6NU0R0eiCYVquU4RcjKcLzGfx0aa1lMr2TnLQUSeLFZHFxsy
+yMXXuMPig3HK4A7SGFHupO+/1H/sL4xpH5zg8+Zg2r8xnnney7abxcuv0uATWSIe
+KlNnb1ZO1BAxFnESc3GtyOCr2dUwZHX5mRVP+Zxp2ni5qHNraf3wE2VPIQIDAQAB
+AoGBALyvnSt7KUquDen7nXQtvJBudnf9KFPt//OjkdHHxNZNpoF/JCSqfQeoYkeu
+MdAVYNLQGMiRifzZz4dDhA9xfUAuy7lcGQcMCxEQ1dwwuFaYkawbS0Tvy2PFlq2d
+H5/HeDXU4EDJ3BZg0eYj2Bnkt1sJI35UKQSxblQ0MY2q0uFBAkEA5MMOogkgUx1C
+67S1tFqMUSM8D0mZB0O5vOJZC5Gtt2Urju6vywge2ArExWRXlM2qGl8afFy2SgSv
+Xk5eybcEiQJBAOMRwwbEoW5NYHuFFbSJyWll4n71CYuWuQOCzehDPyTb80WFZGLV
+i91kFIjeERyq88eDE5xVB3ZuRiXqaShO/9kCQQCKOEkpInaDgZSjskZvuJ47kByD
+6CYsO4GIXQMMeHML8ncFH7bb6AYq5ybJVb2NTU7QLFJmfeYuhvIm+xdOreRxAkEA
+o5FC5Jg2FUfFzZSDmyZ6IONUsdF/i78KDV5nRv1R+hI6/oRlWNCtTNBv/lvBBd6b
+dseUE9QoaQZsn5lpILEvmQJAZ0B+Or1rAYjnbjnUhdVZoy9kC4Zov+4UH3N/BtSy
+KJRWUR0wTWfZBPZ5hAYZjTBEAFULaYCXlQKsODSp0M1aQA==
+-----END PRIVATE KEY-----`

builtin/credential/aws/pkcs7/encrypt.go

@@ -0,0 +1,399 @@
+package pkcs7
+
+import (
+	"bytes"
+	"crypto/aes"
+	"crypto/cipher"
+	"crypto/des"
+	"crypto/rand"
+	"crypto/rsa"
+	"crypto/x509"
+	"crypto/x509/pkix"
+	"encoding/asn1"
+	"errors"
+	"fmt"
+)
+
+type envelopedData struct {
+	Version              int
+	RecipientInfos       []recipientInfo `asn1:"set"`
+	EncryptedContentInfo encryptedContentInfo
+}
+
+type encryptedData struct {
+	Version              int
+	EncryptedContentInfo encryptedContentInfo
+}
+
+type recipientInfo struct {
+	Version                int
+	IssuerAndSerialNumber  issuerAndSerial
+	KeyEncryptionAlgorithm pkix.AlgorithmIdentifier
+	EncryptedKey           []byte
+}
+
+type encryptedContentInfo struct {
+	ContentType                asn1.ObjectIdentifier
+	ContentEncryptionAlgorithm pkix.AlgorithmIdentifier
+	EncryptedContent           asn1.RawValue `asn1:"tag:0,optional"`
+}
+
+const (
+	// EncryptionAlgorithmDESCBC is the DES CBC encryption algorithm
+	EncryptionAlgorithmDESCBC = iota
+
+	// EncryptionAlgorithmAES128CBC is the AES 128 bits with CBC encryption algorithm
+	// Avoid this algorithm unless required for interoperability; use AES GCM instead.
+	EncryptionAlgorithmAES128CBC
+
+	// EncryptionAlgorithmAES256CBC is the AES 256 bits with CBC encryption algorithm
+	// Avoid this algorithm unless required for interoperability; use AES GCM instead.
+	EncryptionAlgorithmAES256CBC
+
+	// EncryptionAlgorithmAES128GCM is the AES 128 bits with GCM encryption algorithm
+	EncryptionAlgorithmAES128GCM
+
+	// EncryptionAlgorithmAES256GCM is the AES 256 bits with GCM encryption algorithm
+	EncryptionAlgorithmAES256GCM
+)
+
+// ContentEncryptionAlgorithm determines the algorithm used to encrypt the
+// plaintext message. Change the value of this variable to change which
+// algorithm is used in the Encrypt() function.
+var ContentEncryptionAlgorithm = EncryptionAlgorithmDESCBC
+
+// ErrUnsupportedEncryptionAlgorithm is returned when attempting to encrypt
+// content with an unsupported algorithm.
+var ErrUnsupportedEncryptionAlgorithm = errors.New("pkcs7: cannot encrypt content: only DES-CBC, AES-CBC, and AES-GCM supported")
+
+// ErrPSKNotProvided is returned when attempting to encrypt
+// using a PSK without actually providing the PSK.
+var ErrPSKNotProvided = errors.New("pkcs7: cannot encrypt content: PSK not provided")
+
+const nonceSize = 12
+
+type aesGCMParameters struct {
+	Nonce  []byte `asn1:"tag:4"`
+	ICVLen int
+}
+
+func encryptAESGCM(content []byte, key []byte) ([]byte, *encryptedContentInfo, error) {
+	var keyLen int
+	var algID asn1.ObjectIdentifier
+	switch ContentEncryptionAlgorithm {
+	case EncryptionAlgorithmAES128GCM:
+		keyLen = 16
+		algID = OIDEncryptionAlgorithmAES128GCM
+	case EncryptionAlgorithmAES256GCM:
+		keyLen = 32
+		algID = OIDEncryptionAlgorithmAES256GCM
+	default:
+		return nil, nil, fmt.Errorf("invalid ContentEncryptionAlgorithm in encryptAESGCM: %d", ContentEncryptionAlgorithm)
+	}
+	if key == nil {
+		// Create AES key
+		key = make([]byte, keyLen)
+
+		_, err := rand.Read(key)
+		if err != nil {
+			return nil, nil, err
+		}
+	}
+
+	// Create nonce
+	nonce := make([]byte, nonceSize)
+
+	_, err := rand.Read(nonce)
+	if err != nil {
+		return nil, nil, err
+	}
+
+	// Encrypt content
+	block, err := aes.NewCipher(key)
+	if err != nil {
+		return nil, nil, err
+	}
+
+	gcm, err := cipher.NewGCM(block)
+	if err != nil {
+		return nil, nil, err
+	}
+
+	ciphertext := gcm.Seal(nil, nonce, content, nil)
+
+	// Prepare ASN.1 Encrypted Content Info
+	paramSeq := aesGCMParameters{
+		Nonce:  nonce,
+		ICVLen: gcm.Overhead(),
+	}
+
+	paramBytes, err := asn1.Marshal(paramSeq)
+	if err != nil {
+		return nil, nil, err
+	}
+
+	eci := encryptedContentInfo{
+		ContentType: OIDData,
+		ContentEncryptionAlgorithm: pkix.AlgorithmIdentifier{
+			Algorithm: algID,
+			Parameters: asn1.RawValue{
+				Tag:   asn1.TagSequence,
+				Bytes: paramBytes,
+			},
+		},
+		EncryptedContent: marshalEncryptedContent(ciphertext),
+	}
+
+	return key, &eci, nil
+}
+
+func encryptDESCBC(content []byte, key []byte) ([]byte, *encryptedContentInfo, error) {
+	if key == nil {
+		// Create DES key
+		key = make([]byte, 8)
+
+		_, err := rand.Read(key)
+		if err != nil {
+			return nil, nil, err
+		}
+	}
+
+	// Create CBC IV
+	iv := make([]byte, des.BlockSize)
+	_, err := rand.Read(iv)
+	if err != nil {
+		return nil, nil, err
+	}
+
+	// Encrypt padded content
+	block, err := des.NewCipher(key)
+	if err != nil {
+		return nil, nil, err
+	}
+	mode := cipher.NewCBCEncrypter(block, iv)
+	plaintext, err := pad(content, mode.BlockSize())
+	if err != nil {
+		return nil, nil, err
+	}
+	cyphertext := make([]byte, len(plaintext))
+	mode.CryptBlocks(cyphertext, plaintext)
+
+	// Prepare ASN.1 Encrypted Content Info
+	eci := encryptedContentInfo{
+		ContentType: OIDData,
+		ContentEncryptionAlgorithm: pkix.AlgorithmIdentifier{
+			Algorithm:  OIDEncryptionAlgorithmDESCBC,
+			Parameters: asn1.RawValue{Tag: 4, Bytes: iv},
+		},
+		EncryptedContent: marshalEncryptedContent(cyphertext),
+	}
+
+	return key, &eci, nil
+}
+
+func encryptAESCBC(content []byte, key []byte) ([]byte, *encryptedContentInfo, error) {
+	var keyLen int
+	var algID asn1.ObjectIdentifier
+	switch ContentEncryptionAlgorithm {
+	case EncryptionAlgorithmAES128CBC:
+		keyLen = 16
+		algID = OIDEncryptionAlgorithmAES128CBC
+	case EncryptionAlgorithmAES256CBC:
+		keyLen = 32
+		algID = OIDEncryptionAlgorithmAES256CBC
+	default:
+		return nil, nil, fmt.Errorf("invalid ContentEncryptionAlgorithm in encryptAESCBC: %d", ContentEncryptionAlgorithm)
+	}
+
+	if key == nil {
+		// Create AES key
+		key = make([]byte, keyLen)
+
+		_, err := rand.Read(key)
+		if err != nil {
+			return nil, nil, err
+		}
+	}
+
+	// Create CBC IV
+	iv := make([]byte, aes.BlockSize)
+	_, err := rand.Read(iv)
+	if err != nil {
+		return nil, nil, err
+	}
+
+	// Encrypt padded content
+	block, err := aes.NewCipher(key)
+	if err != nil {
+		return nil, nil, err
+	}
+	mode := cipher.NewCBCEncrypter(block, iv)
+	plaintext, err := pad(content, mode.BlockSize())
+	if err != nil {
+		return nil, nil, err
+	}
+	cyphertext := make([]byte, len(plaintext))
+	mode.CryptBlocks(cyphertext, plaintext)
+
+	// Prepare ASN.1 Encrypted Content Info
+	eci := encryptedContentInfo{
+		ContentType: OIDData,
+		ContentEncryptionAlgorithm: pkix.AlgorithmIdentifier{
+			Algorithm:  algID,
+			Parameters: asn1.RawValue{Tag: 4, Bytes: iv},
+		},
+		EncryptedContent: marshalEncryptedContent(cyphertext),
+	}
+
+	return key, &eci, nil
+}
+
+// Encrypt creates and returns an envelope data PKCS7 structure with encrypted
+// recipient keys for each recipient public key.
+//
+// The algorithm used to perform encryption is determined by the current value
+// of the global ContentEncryptionAlgorithm package variable. By default, the
+// value is EncryptionAlgorithmDESCBC. To use a different algorithm, change the
+// value before calling Encrypt(). For example:
+//
+//     ContentEncryptionAlgorithm = EncryptionAlgorithmAES128GCM
+//
+// TODO(fullsailor): Add support for encrypting content with other algorithms
+func Encrypt(content []byte, recipients []*x509.Certificate) ([]byte, error) {
+	var eci *encryptedContentInfo
+	var key []byte
+	var err error
+
+	// Apply chosen symmetric encryption method
+	switch ContentEncryptionAlgorithm {
+	case EncryptionAlgorithmDESCBC:
+		key, eci, err = encryptDESCBC(content, nil)
+	case EncryptionAlgorithmAES128CBC:
+		fallthrough
+	case EncryptionAlgorithmAES256CBC:
+		key, eci, err = encryptAESCBC(content, nil)
+	case EncryptionAlgorithmAES128GCM:
+		fallthrough
+	case EncryptionAlgorithmAES256GCM:
+		key, eci, err = encryptAESGCM(content, nil)
+
+	default:
+		return nil, ErrUnsupportedEncryptionAlgorithm
+	}
+
+	if err != nil {
+		return nil, err
+	}
+
+	// Prepare each recipient's encrypted cipher key
+	recipientInfos := make([]recipientInfo, len(recipients))
+	for i, recipient := range recipients {
+		encrypted, err := encryptKey(key, recipient)
+		if err != nil {
+			return nil, err
+		}
+		ias, err := cert2issuerAndSerial(recipient)
+		if err != nil {
+			return nil, err
+		}
+		info := recipientInfo{
+			Version:               0,
+			IssuerAndSerialNumber: ias,
+			KeyEncryptionAlgorithm: pkix.AlgorithmIdentifier{
+				Algorithm: OIDEncryptionAlgorithmRSA,
+			},
+			EncryptedKey: encrypted,
+		}
+		recipientInfos[i] = info
+	}
+
+	// Prepare envelope content
+	envelope := envelopedData{
+		EncryptedContentInfo: *eci,
+		Version:              0,
+		RecipientInfos:       recipientInfos,
+	}
+	innerContent, err := asn1.Marshal(envelope)
+	if err != nil {
+		return nil, err
+	}
+
+	// Prepare outer payload structure
+	wrapper := contentInfo{
+		ContentType: OIDEnvelopedData,
+		Content:     asn1.RawValue{Class: 2, Tag: 0, IsCompound: true, Bytes: innerContent},
+	}
+
+	return asn1.Marshal(wrapper)
+}
+
+// EncryptUsingPSK creates and returns an encrypted data PKCS7 structure,
+// encrypted using caller provided pre-shared secret.
+func EncryptUsingPSK(content []byte, key []byte) ([]byte, error) {
+	var eci *encryptedContentInfo
+	var err error
+
+	if key == nil {
+		return nil, ErrPSKNotProvided
+	}
+
+	// Apply chosen symmetric encryption method
+	switch ContentEncryptionAlgorithm {
+	case EncryptionAlgorithmDESCBC:
+		_, eci, err = encryptDESCBC(content, key)
+
+	case EncryptionAlgorithmAES128GCM:
+		fallthrough
+	case EncryptionAlgorithmAES256GCM:
+		_, eci, err = encryptAESGCM(content, key)
+
+	default:
+		return nil, ErrUnsupportedEncryptionAlgorithm
+	}
+
+	if err != nil {
+		return nil, err
+	}
+
+	// Prepare encrypted-data content
+	ed := encryptedData{
+		Version:              0,
+		EncryptedContentInfo: *eci,
+	}
+	innerContent, err := asn1.Marshal(ed)
+	if err != nil {
+		return nil, err
+	}
+
+	// Prepare outer payload structure
+	wrapper := contentInfo{
+		ContentType: OIDEncryptedData,
+		Content:     asn1.RawValue{Class: 2, Tag: 0, IsCompound: true, Bytes: innerContent},
+	}
+
+	return asn1.Marshal(wrapper)
+}
+
+func marshalEncryptedContent(content []byte) asn1.RawValue {
+	asn1Content, _ := asn1.Marshal(content)
+	return asn1.RawValue{Tag: 0, Class: 2, Bytes: asn1Content, IsCompound: true}
+}
+
+func encryptKey(key []byte, recipient *x509.Certificate) ([]byte, error) {
+	if pub := recipient.PublicKey.(*rsa.PublicKey); pub != nil {
+		return rsa.EncryptPKCS1v15(rand.Reader, pub, key)
+	}
+	return nil, ErrUnsupportedAlgorithm
+}
+
+func pad(data []byte, blocklen int) ([]byte, error) {
+	if blocklen < 1 {
+		return nil, fmt.Errorf("invalid blocklen %d", blocklen)
+	}
+	padlen := blocklen - (len(data) % blocklen)
+	if padlen == 0 {
+		padlen = blocklen
+	}
+	pad := bytes.Repeat([]byte{byte(padlen)}, padlen)
+	return append(data, pad...), nil
+}

builtin/credential/aws/pkcs7/encrypt_test.go

@@ -0,0 +1,102 @@
+package pkcs7
+
+import (
+	"bytes"
+	"crypto/x509"
+	"testing"
+)
+
+func TestEncrypt(t *testing.T) {
+	modes := []int{
+		EncryptionAlgorithmDESCBC,
+		EncryptionAlgorithmAES128CBC,
+		EncryptionAlgorithmAES256CBC,
+		EncryptionAlgorithmAES128GCM,
+		EncryptionAlgorithmAES256GCM,
+	}
+	sigalgs := []x509.SignatureAlgorithm{
+		x509.SHA1WithRSA,
+		x509.SHA256WithRSA,
+		x509.SHA512WithRSA,
+	}
+	for _, mode := range modes {
+		for _, sigalg := range sigalgs {
+			ContentEncryptionAlgorithm = mode
+
+			plaintext := []byte("Hello Secret World!")
+			cert, err := createTestCertificate(sigalg)
+			if err != nil {
+				t.Fatal(err)
+			}
+			encrypted, err := Encrypt(plaintext, []*x509.Certificate{cert.Certificate})
+			if err != nil {
+				t.Fatal(err)
+			}
+			p7, err := Parse(encrypted)
+			if err != nil {
+				t.Fatalf("cannot Parse encrypted result: %s", err)
+			}
+			result, err := p7.Decrypt(cert.Certificate, *cert.PrivateKey)
+			if err != nil {
+				t.Fatalf("cannot Decrypt encrypted result: %s", err)
+			}
+			if !bytes.Equal(plaintext, result) {
+				t.Errorf("encrypted data does not match plaintext:\n\tExpected: %s\n\tActual: %s", plaintext, result)
+			}
+		}
+	}
+}
+
+func TestEncryptUsingPSK(t *testing.T) {
+	modes := []int{
+		EncryptionAlgorithmDESCBC,
+		EncryptionAlgorithmAES128GCM,
+	}
+
+	for _, mode := range modes {
+		ContentEncryptionAlgorithm = mode
+		plaintext := []byte("Hello Secret World!")
+		var key []byte
+
+		switch mode {
+		case EncryptionAlgorithmDESCBC:
+			key = []byte("64BitKey")
+		case EncryptionAlgorithmAES128GCM:
+			key = []byte("128BitKey4AESGCM")
+		}
+		ciphertext, err := EncryptUsingPSK(plaintext, key)
+		if err != nil {
+			t.Fatal(err)
+		}
+
+		p7, _ := Parse(ciphertext)
+		result, err := p7.DecryptUsingPSK(key)
+		if err != nil {
+			t.Fatalf("cannot Decrypt encrypted result: %s", err)
+		}
+		if !bytes.Equal(plaintext, result) {
+			t.Errorf("encrypted data does not match plaintext:\n\tExpected: %s\n\tActual: %s", plaintext, result)
+		}
+	}
+}
+
+func TestPad(t *testing.T) {
+	tests := []struct {
+		Original  []byte
+		Expected  []byte
+		BlockSize int
+	}{
+		{[]byte{0x1, 0x2, 0x3, 0x10}, []byte{0x1, 0x2, 0x3, 0x10, 0x4, 0x4, 0x4, 0x4}, 8},
+		{[]byte{0x1, 0x2, 0x3, 0x0, 0x0, 0x0, 0x0, 0x0}, []byte{0x1, 0x2, 0x3, 0x0, 0x0, 0x0, 0x0, 0x0, 0x8, 0x8, 0x8, 0x8, 0x8, 0x8, 0x8, 0x8}, 8},
+	}
+	for _, test := range tests {
+		padded, err := pad(test.Original, test.BlockSize)
+		if err != nil {
+			t.Errorf("pad encountered error: %s", err)
+			continue
+		}
+		if !bytes.Equal(test.Expected, padded) {
+			t.Errorf("pad results mismatch:\n\tExpected: %X\n\tActual: %X", test.Expected, padded)
+		}
+	}
+}

builtin/credential/aws/pkcs7/pkcs7.go

@@ -0,0 +1,291 @@
+// Package pkcs7 implements parsing and generation of some PKCS#7 structures.
+package pkcs7
+
+import (
+	"bytes"
+	"crypto"
+	"crypto/dsa"
+	"crypto/ecdsa"
+	"crypto/rsa"
+	"crypto/x509"
+	"crypto/x509/pkix"
+	"encoding/asn1"
+	"errors"
+	"fmt"
+	"sort"
+
+	_ "crypto/sha1" // for crypto.SHA1
+)
+
+// PKCS7 Represents a PKCS7 structure
+type PKCS7 struct {
+	Content      []byte
+	Certificates []*x509.Certificate
+	CRLs         []pkix.CertificateList
+	Signers      []signerInfo
+	raw          interface{}
+}
+
+type contentInfo struct {
+	ContentType asn1.ObjectIdentifier
+	Content     asn1.RawValue `asn1:"explicit,optional,tag:0"`
+}
+
+// ErrUnsupportedContentType is returned when a PKCS7 content is not supported.
+// Currently only Data (1.2.840.113549.1.7.1), Signed Data (1.2.840.113549.1.7.2),
+// and Enveloped Data are supported (1.2.840.113549.1.7.3)
+var ErrUnsupportedContentType = errors.New("pkcs7: cannot parse data: unimplemented content type")
+
+type unsignedData []byte
+
+var (
+	// Signed Data OIDs
+	OIDData                   = asn1.ObjectIdentifier{1, 2, 840, 113549, 1, 7, 1}
+	OIDSignedData             = asn1.ObjectIdentifier{1, 2, 840, 113549, 1, 7, 2}
+	OIDEnvelopedData          = asn1.ObjectIdentifier{1, 2, 840, 113549, 1, 7, 3}
+	OIDEncryptedData          = asn1.ObjectIdentifier{1, 2, 840, 113549, 1, 7, 6}
+	OIDAttributeContentType   = asn1.ObjectIdentifier{1, 2, 840, 113549, 1, 9, 3}
+	OIDAttributeMessageDigest = asn1.ObjectIdentifier{1, 2, 840, 113549, 1, 9, 4}
+	OIDAttributeSigningTime   = asn1.ObjectIdentifier{1, 2, 840, 113549, 1, 9, 5}
+
+	// Digest Algorithms
+	OIDDigestAlgorithmSHA1   = asn1.ObjectIdentifier{1, 3, 14, 3, 2, 26}
+	OIDDigestAlgorithmSHA256 = asn1.ObjectIdentifier{2, 16, 840, 1, 101, 3, 4, 2, 1}
+	OIDDigestAlgorithmSHA384 = asn1.ObjectIdentifier{2, 16, 840, 1, 101, 3, 4, 2, 2}
+	OIDDigestAlgorithmSHA512 = asn1.ObjectIdentifier{2, 16, 840, 1, 101, 3, 4, 2, 3}
+
+	OIDDigestAlgorithmDSA     = asn1.ObjectIdentifier{1, 2, 840, 10040, 4, 1}
+	OIDDigestAlgorithmDSASHA1 = asn1.ObjectIdentifier{1, 2, 840, 10040, 4, 3}
+
+	OIDDigestAlgorithmECDSASHA1   = asn1.ObjectIdentifier{1, 2, 840, 10045, 4, 1}
+	OIDDigestAlgorithmECDSASHA256 = asn1.ObjectIdentifier{1, 2, 840, 10045, 4, 3, 2}
+	OIDDigestAlgorithmECDSASHA384 = asn1.ObjectIdentifier{1, 2, 840, 10045, 4, 3, 3}
+	OIDDigestAlgorithmECDSASHA512 = asn1.ObjectIdentifier{1, 2, 840, 10045, 4, 3, 4}
+
+	// Signature Algorithms
+	OIDEncryptionAlgorithmRSA       = asn1.ObjectIdentifier{1, 2, 840, 113549, 1, 1, 1}
+	OIDEncryptionAlgorithmRSASHA1   = asn1.ObjectIdentifier{1, 2, 840, 113549, 1, 1, 5}
+	OIDEncryptionAlgorithmRSASHA256 = asn1.ObjectIdentifier{1, 2, 840, 113549, 1, 1, 11}
+	OIDEncryptionAlgorithmRSASHA384 = asn1.ObjectIdentifier{1, 2, 840, 113549, 1, 1, 12}
+	OIDEncryptionAlgorithmRSASHA512 = asn1.ObjectIdentifier{1, 2, 840, 113549, 1, 1, 13}
+
+	OIDEncryptionAlgorithmECDSAP256 = asn1.ObjectIdentifier{1, 2, 840, 10045, 3, 1, 7}
+	OIDEncryptionAlgorithmECDSAP384 = asn1.ObjectIdentifier{1, 3, 132, 0, 34}
+	OIDEncryptionAlgorithmECDSAP521 = asn1.ObjectIdentifier{1, 3, 132, 0, 35}
+
+	// Encryption Algorithms
+	OIDEncryptionAlgorithmDESCBC     = asn1.ObjectIdentifier{1, 3, 14, 3, 2, 7}
+	OIDEncryptionAlgorithmDESEDE3CBC = asn1.ObjectIdentifier{1, 2, 840, 113549, 3, 7}
+	OIDEncryptionAlgorithmAES256CBC  = asn1.ObjectIdentifier{2, 16, 840, 1, 101, 3, 4, 1, 42}
+	OIDEncryptionAlgorithmAES128GCM  = asn1.ObjectIdentifier{2, 16, 840, 1, 101, 3, 4, 1, 6}
+	OIDEncryptionAlgorithmAES128CBC  = asn1.ObjectIdentifier{2, 16, 840, 1, 101, 3, 4, 1, 2}
+	OIDEncryptionAlgorithmAES256GCM  = asn1.ObjectIdentifier{2, 16, 840, 1, 101, 3, 4, 1, 46}
+)
+
+func getHashForOID(oid asn1.ObjectIdentifier) (crypto.Hash, error) {
+	switch {
+	case oid.Equal(OIDDigestAlgorithmSHA1), oid.Equal(OIDDigestAlgorithmECDSASHA1),
+		oid.Equal(OIDDigestAlgorithmDSA), oid.Equal(OIDDigestAlgorithmDSASHA1),
+		oid.Equal(OIDEncryptionAlgorithmRSA):
+		return crypto.SHA1, nil
+	case oid.Equal(OIDDigestAlgorithmSHA256), oid.Equal(OIDDigestAlgorithmECDSASHA256):
+		return crypto.SHA256, nil
+	case oid.Equal(OIDDigestAlgorithmSHA384), oid.Equal(OIDDigestAlgorithmECDSASHA384):
+		return crypto.SHA384, nil
+	case oid.Equal(OIDDigestAlgorithmSHA512), oid.Equal(OIDDigestAlgorithmECDSASHA512):
+		return crypto.SHA512, nil
+	}
+	return crypto.Hash(0), ErrUnsupportedAlgorithm
+}
+
+// getDigestOIDForSignatureAlgorithm takes an x509.SignatureAlgorithm
+// and returns the corresponding OID digest algorithm
+func getDigestOIDForSignatureAlgorithm(digestAlg x509.SignatureAlgorithm) (asn1.ObjectIdentifier, error) {
+	switch digestAlg {
+	case x509.SHA1WithRSA, x509.ECDSAWithSHA1:
+		return OIDDigestAlgorithmSHA1, nil
+	case x509.SHA256WithRSA, x509.ECDSAWithSHA256:
+		return OIDDigestAlgorithmSHA256, nil
+	case x509.SHA384WithRSA, x509.ECDSAWithSHA384:
+		return OIDDigestAlgorithmSHA384, nil
+	case x509.SHA512WithRSA, x509.ECDSAWithSHA512:
+		return OIDDigestAlgorithmSHA512, nil
+	}
+	return nil, fmt.Errorf("pkcs7: cannot convert hash to oid, unknown hash algorithm")
+}
+
+// getOIDForEncryptionAlgorithm takes the private key type of the signer and
+// the OID of a digest algorithm to return the appropriate signerInfo.DigestEncryptionAlgorithm
+func getOIDForEncryptionAlgorithm(pkey crypto.PrivateKey, OIDDigestAlg asn1.ObjectIdentifier) (asn1.ObjectIdentifier, error) {
+	switch pkey.(type) {
+	case *rsa.PrivateKey:
+		switch {
+		default:
+			return OIDEncryptionAlgorithmRSA, nil
+		case OIDDigestAlg.Equal(OIDEncryptionAlgorithmRSA):
+			return OIDEncryptionAlgorithmRSA, nil
+		case OIDDigestAlg.Equal(OIDDigestAlgorithmSHA1):
+			return OIDEncryptionAlgorithmRSASHA1, nil
+		case OIDDigestAlg.Equal(OIDDigestAlgorithmSHA256):
+			return OIDEncryptionAlgorithmRSASHA256, nil
+		case OIDDigestAlg.Equal(OIDDigestAlgorithmSHA384):
+			return OIDEncryptionAlgorithmRSASHA384, nil
+		case OIDDigestAlg.Equal(OIDDigestAlgorithmSHA512):
+			return OIDEncryptionAlgorithmRSASHA512, nil
+		}
+	case *ecdsa.PrivateKey:
+		switch {
+		case OIDDigestAlg.Equal(OIDDigestAlgorithmSHA1):
+			return OIDDigestAlgorithmECDSASHA1, nil
+		case OIDDigestAlg.Equal(OIDDigestAlgorithmSHA256):
+			return OIDDigestAlgorithmECDSASHA256, nil
+		case OIDDigestAlg.Equal(OIDDigestAlgorithmSHA384):
+			return OIDDigestAlgorithmECDSASHA384, nil
+		case OIDDigestAlg.Equal(OIDDigestAlgorithmSHA512):
+			return OIDDigestAlgorithmECDSASHA512, nil
+		}
+	case *dsa.PrivateKey:
+		return OIDDigestAlgorithmDSA, nil
+	}
+	return nil, fmt.Errorf("pkcs7: cannot convert encryption algorithm to oid, unknown private key type %T", pkey)
+
+}
+
+// Parse decodes a DER encoded PKCS7 package
+func Parse(data []byte) (p7 *PKCS7, err error) {
+	if len(data) == 0 {
+		return nil, errors.New("pkcs7: input data is empty")
+	}
+	var info contentInfo
+	der, err := ber2der(data)
+	if err != nil {
+		return nil, err
+	}
+	rest, err := asn1.Unmarshal(der, &info)
+	if len(rest) > 0 {
+		err = asn1.SyntaxError{Msg: "trailing data"}
+		return
+	}
+	if err != nil {
+		return
+	}
+
+	// fmt.Printf("--> Content Type: %s", info.ContentType)
+	switch {
+	case info.ContentType.Equal(OIDSignedData):
+		return parseSignedData(info.Content.Bytes)
+	case info.ContentType.Equal(OIDEnvelopedData):
+		return parseEnvelopedData(info.Content.Bytes)
+	case info.ContentType.Equal(OIDEncryptedData):
+		return parseEncryptedData(info.Content.Bytes)
+	}
+	return nil, ErrUnsupportedContentType
+}
+
+func parseEnvelopedData(data []byte) (*PKCS7, error) {
+	var ed envelopedData
+	if _, err := asn1.Unmarshal(data, &ed); err != nil {
+		return nil, err
+	}
+	return &PKCS7{
+		raw: ed,
+	}, nil
+}
+
+func parseEncryptedData(data []byte) (*PKCS7, error) {
+	var ed encryptedData
+	if _, err := asn1.Unmarshal(data, &ed); err != nil {
+		return nil, err
+	}
+	return &PKCS7{
+		raw: ed,
+	}, nil
+}
+
+func (raw rawCertificates) Parse() ([]*x509.Certificate, error) {
+	if len(raw.Raw) == 0 {
+		return nil, nil
+	}
+
+	var val asn1.RawValue
+	if _, err := asn1.Unmarshal(raw.Raw, &val); err != nil {
+		return nil, err
+	}
+
+	return x509.ParseCertificates(val.Bytes)
+}
+
+func isCertMatchForIssuerAndSerial(cert *x509.Certificate, ias issuerAndSerial) bool {
+	return cert.SerialNumber.Cmp(ias.SerialNumber) == 0 && bytes.Equal(cert.RawIssuer, ias.IssuerName.FullBytes)
+}
+
+// Attribute represents a key value pair attribute. Value must be marshalable byte
+// `encoding/asn1`
+type Attribute struct {
+	Type  asn1.ObjectIdentifier
+	Value interface{}
+}
+
+type attributes struct {
+	types  []asn1.ObjectIdentifier
+	values []interface{}
+}
+
+// Add adds the attribute, maintaining insertion order
+func (attrs *attributes) Add(attrType asn1.ObjectIdentifier, value interface{}) {
+	attrs.types = append(attrs.types, attrType)
+	attrs.values = append(attrs.values, value)
+}
+
+type sortableAttribute struct {
+	SortKey   []byte
+	Attribute attribute
+}
+
+type attributeSet []sortableAttribute
+
+func (sa attributeSet) Len() int {
+	return len(sa)
+}
+
+func (sa attributeSet) Less(i, j int) bool {
+	return bytes.Compare(sa[i].SortKey, sa[j].SortKey) < 0
+}
+
+func (sa attributeSet) Swap(i, j int) {
+	sa[i], sa[j] = sa[j], sa[i]
+}
+
+func (sa attributeSet) Attributes() []attribute {
+	attrs := make([]attribute, len(sa))
+	for i, attr := range sa {
+		attrs[i] = attr.Attribute
+	}
+	return attrs
+}
+
+func (attrs *attributes) ForMarshalling() ([]attribute, error) {
+	sortables := make(attributeSet, len(attrs.types))
+	for i := range sortables {
+		attrType := attrs.types[i]
+		attrValue := attrs.values[i]
+		asn1Value, err := asn1.Marshal(attrValue)
+		if err != nil {
+			return nil, err
+		}
+		attr := attribute{
+			Type:  attrType,
+			Value: asn1.RawValue{Tag: 17, IsCompound: true, Bytes: asn1Value}, // 17 == SET tag
+		}
+		encoded, err := asn1.Marshal(attr)
+		if err != nil {
+			return nil, err
+		}
+		sortables[i] = sortableAttribute{
+			SortKey:   encoded,
+			Attribute: attr,
+		}
+	}
+	sort.Sort(sortables)
+	return sortables.Attributes(), nil
+}

builtin/credential/aws/pkcs7/pkcs7_test.go

@@ -0,0 +1,326 @@
+package pkcs7
+
+import (
+	"crypto"
+	"crypto/dsa"
+	"crypto/ecdsa"
+	"crypto/elliptic"
+	"crypto/rand"
+	"crypto/rsa"
+	"crypto/x509"
+	"crypto/x509/pkix"
+	"encoding/pem"
+	"fmt"
+	"log"
+	"math/big"
+	"os"
+	"time"
+)
+
+var test1024Key, test2048Key, test3072Key, test4096Key *rsa.PrivateKey
+
+func init() {
+	test1024Key = &rsa.PrivateKey{
+		PublicKey: rsa.PublicKey{
+			N: fromBase10("123024078101403810516614073341068864574068590522569345017786163424062310013967742924377390210586226651760719671658568413826602264886073432535341149584680111145880576802262550990305759285883150470245429547886689754596541046564560506544976611114898883158121012232676781340602508151730773214407220733898059285561"),
+			E: 65537,
+		},
+		D: fromBase10("118892427340746627750435157989073921703209000249285930635312944544706203626114423392257295670807166199489096863209592887347935991101581502404113203993092422730000157893515953622392722273095289787303943046491132467130346663160540744582438810535626328230098940583296878135092036661410664695896115177534496784545"),
+		Primes: []*big.Int{
+			fromBase10("12172745919282672373981903347443034348576729562395784527365032103134165674508405592530417723266847908118361582847315228810176708212888860333051929276459099"),
+			fromBase10("10106518193772789699356660087736308350857919389391620140340519320928952625438936098550728858345355053201610649202713962702543058578827268756755006576249339"),
+		},
+	}
+	test1024Key.Precompute()
+	test2048Key = &rsa.PrivateKey{
+		PublicKey: rsa.PublicKey{
+			N: fromBase10("14314132931241006650998084889274020608918049032671858325988396851334124245188214251956198731333464217832226406088020736932173064754214329009979944037640912127943488972644697423190955557435910767690712778463524983667852819010259499695177313115447116110358524558307947613422897787329221478860907963827160223559690523660574329011927531289655711860504630573766609239332569210831325633840174683944553667352219670930408593321661375473885147973879086994006440025257225431977751512374815915392249179976902953721486040787792801849818254465486633791826766873076617116727073077821584676715609985777563958286637185868165868520557"),
+			E: 3,
+		},
+		D: fromBase10("9542755287494004433998723259516013739278699355114572217325597900889416163458809501304132487555642811888150937392013824621448709836142886006653296025093941418628992648429798282127303704957273845127141852309016655778568546006839666463451542076964744073572349705538631742281931858219480985907271975884773482372966847639853897890615456605598071088189838676728836833012254065983259638538107719766738032720239892094196108713378822882383694456030043492571063441943847195939549773271694647657549658603365629458610273821292232646334717612674519997533901052790334279661754176490593041941863932308687197618671528035670452762731"),
+		Primes: []*big.Int{
+			fromBase10("130903255182996722426771613606077755295583329135067340152947172868415809027537376306193179624298874215608270802054347609836776473930072411958753044562214537013874103802006369634761074377213995983876788718033850153719421695468704276694983032644416930879093914927146648402139231293035971427838068945045019075433"),
+			fromBase10("109348945610485453577574767652527472924289229538286649661240938988020367005475727988253438647560958573506159449538793540472829815903949343191091817779240101054552748665267574271163617694640513549693841337820602726596756351006149518830932261246698766355347898158548465400674856021497190430791824869615170301029"),
+		},
+	}
+	test2048Key.Precompute()
+	test3072Key = &rsa.PrivateKey{
+		PublicKey: rsa.PublicKey{
+			N: fromBase10("4799422180968749215324244710281712119910779465109490663934897082847293004098645365195947978124390029272750644394844443980065532911010718425428791498896288210928474905407341584968381379157418577471272697781778686372450913810019702928839200328075568223462554606149618941566459398862673532997592879359280754226882565483298027678735544377401276021471356093819491755877827249763065753555051973844057308627201762456191918852016986546071426986328720794061622370410645440235373576002278045257207695462423797272017386006110722769072206022723167102083033531426777518054025826800254337147514768377949097720074878744769255210076910190151785807232805749219196645305822228090875616900385866236956058984170647782567907618713309775105943700661530312800231153745705977436176908325539234432407050398510090070342851489496464612052853185583222422124535243967989533830816012180864309784486694786581956050902756173889941244024888811572094961378021"),
+			E: 65537,
+		},
+		D: fromBase10("4068124900056380177006532461065648259352178312499768312132802353620854992915205894105621345694615110794369150964768050224096623567443679436821868510233726084582567244003894477723706516831312989564775159596496449435830457803384416702014837685962523313266832032687145914871879794104404800823188153886925022171560391765913739346955738372354826804228989767120353182641396181570533678315099748218734875742705419933837638038793286534641711407564379950728858267828581787483317040753987167237461567332386718574803231955771633274184646232632371006762852623964054645811527580417392163873708539175349637050049959954373319861427407953413018816604365474462455009323937599275324390953644555294418021286807661559165324810415569396577697316798600308544755741549699523972971375304826663847015905713096287495342701286542193782001358775773848824496321550110946106870685499577993864871847542645561943034990484973293461948058147956373115641615329"),
+		Primes: []*big.Int{
+			fromBase10("2378529069722721185825622840841310902793949682948530343491428052737890236476884657507685118578733560141370511507721598189068683665232991988491561624429938984370132428230072355214627085652359350722926394699707232921674771664421591347888367477300909202851476404132163673865768760147403525700174918450753162242834161458300343282159799476695001920226357456953682236859505243928716782707623075239350380352265954107362618991716602898266999700316937680986690964564264877"),
+			fromBase10("2017811025336026464312837780072272578817919741496395062543647660689775637351085991504709917848745137013798005682591633910555599626950744674459976829106750083386168859581016361317479081273480343110649405858059581933773354781034946787147300862495438979895430001323443224335618577322449133208754541656374335100929456885995320929464029817626916719434010943205170760536768893924932021302887114400922813817969176636993508191950649313115712159241971065134077636674146073"),
+		},
+	}
+	test3072Key.Precompute()
+	test4096Key = &rsa.PrivateKey{
+		PublicKey: rsa.PublicKey{
+			N: fromBase10("633335480064287130853997429184971616419051348693342219741748040433588285601270210251206421401040394238592139790962887290698043839174341843721930134010306454716566698330215646704263665452264344664385995704186692432827662862845900348526672531755932642433662686500295989783595767573119607065791980381547677840410600100715146047382485989885183858757974681241303484641390718944520330953604501686666386926996348457928415093305041429178744778762826377713889019740060910363468343855830206640274442887621960581569183233822878661711798998132931623726434336448716605363514220760343097572198620479297583609779817750646169845195672483600293522186340560792255595411601450766002877850696008003794520089358819042318331840490155176019070646738739580486357084733208876620846449161909966690602374519398451042362690200166144326179405976024265116931974936425064291406950542193873313447617169603706868220189295654943247311295475722243471700112334609817776430552541319671117235957754556272646031356496763094955985615723596562217985372503002989591679252640940571608314743271809251568670314461039035793703429977801961867815257832671786542212589906513979094156334941265621017752516999186481477500481433634914622735206243841674973785078408289183000133399026553"),
+			E: 65537,
+		},
+		D: fromBase10("439373650557744155078930178606343279553665694488479749802070836418412881168612407941793966086633543867614175621952769177088930851151267623886678906158545451731745754402575409204816390946376103491325109185445659065122640946673660760274557781540431107937331701243915001777636528502669576801704352961341634812275635811512806966908648671988644114352046582195051714797831307925775689566757438907578527366568747104508496278929566712224252103563340770696548181508180254674236716995730292431858611476396845443056967589437890065663497768422598977743046882539288481002449571403783500529740184608873520856954837631427724158592309018382711485601884461168736465751756282510065053161144027097169985941910909130083273691945578478173708396726266170473745329617793866669307716920992380350270584929908460462802627239204245339385636926433446418108504614031393494119344916828744888432279343816084433424594432427362258172264834429525166677273382617457205387388293888430391895615438030066428745187333897518037597413369705720436392869403948934993623418405908467147848576977008003556716087129242155836114780890054057743164411952731290520995017097151300091841286806603044227906213832083363876549637037625314539090155417589796428888619937329669464810549362433"),
+		Primes: []*big.Int{
+			fromBase10("25745433817240673759910623230144796182285844101796353869339294232644316274580053211056707671663014355388701931204078502829809738396303142990312095225333440050808647355535878394534263839500592870406002873182360027755750148248672968563366185348499498613479490545488025779331426515670185366021612402246813511722553210128074701620113404560399242413747318161403908617342170447610792422053460359960010544593668037305465806912471260799852789913123044326555978680190904164976511331681163576833618899773550873682147782263100803907156362439021929408298804955194748640633152519828940133338948391986823456836070708197320166146761"),
+			fromBase10("24599914864909676687852658457515103765368967514652318497893275892114442089314173678877914038802355565271545910572804267918959612739009937926962653912943833939518967731764560204997062096919833970670512726396663920955497151415639902788974842698619579886297871162402643104696160155894685518587660015182381685605752989716946154299190561137541792784125356553411300817844325739404126956793095254412123887617931225840421856505925283322918693259047428656823141903489964287619982295891439430302405252447010728112098326033634688757933930065610737780413018498561434074501822951716586796047404555397992425143397497639322075233073"),
+		},
+	}
+	test4096Key.Precompute()
+}
+
+func fromBase10(base10 string) *big.Int {
+	i, ok := new(big.Int).SetString(base10, 10)
+	if !ok {
+		panic("bad number: " + base10)
+	}
+	return i
+}
+
+type certKeyPair struct {
+	Certificate *x509.Certificate
+	PrivateKey  *crypto.PrivateKey
+}
+
+func createTestCertificate(sigAlg x509.SignatureAlgorithm) (certKeyPair, error) {
+	signer, err := createTestCertificateByIssuer("Eddard Stark", nil, sigAlg, true)
+	if err != nil {
+		return certKeyPair{}, err
+	}
+	pair, err := createTestCertificateByIssuer("Jon Snow", signer, sigAlg, false)
+	if err != nil {
+		return certKeyPair{}, err
+	}
+	return *pair, nil
+}
+
+func createTestCertificateByIssuer(name string, issuer *certKeyPair, sigAlg x509.SignatureAlgorithm, isCA bool) (*certKeyPair, error) {
+	var (
+		err        error
+		priv       crypto.PrivateKey
+		derCert    []byte
+		issuerCert *x509.Certificate
+		issuerKey  crypto.PrivateKey
+	)
+	serialNumberLimit := new(big.Int).Lsh(big.NewInt(1), 32)
+	serialNumber, err := rand.Int(rand.Reader, serialNumberLimit)
+	if err != nil {
+		return nil, err
+	}
+
+	template := x509.Certificate{
+		SerialNumber: serialNumber,
+		Subject: pkix.Name{
+			CommonName:   name,
+			Organization: []string{"Acme Co"},
+		},
+		NotBefore:   time.Now().Add(-1 * time.Second),
+		NotAfter:    time.Now().AddDate(1, 0, 0),
+		KeyUsage:    x509.KeyUsageKeyEncipherment | x509.KeyUsageDigitalSignature,
+		ExtKeyUsage: []x509.ExtKeyUsage{x509.ExtKeyUsageEmailProtection},
+	}
+	if issuer != nil {
+		issuerCert = issuer.Certificate
+		issuerKey = *issuer.PrivateKey
+	}
+	switch sigAlg {
+	case x509.SHA1WithRSA:
+		priv = test1024Key
+		switch issuerKey.(type) {
+		case *rsa.PrivateKey:
+			template.SignatureAlgorithm = x509.SHA1WithRSA
+		case *ecdsa.PrivateKey:
+			template.SignatureAlgorithm = x509.ECDSAWithSHA1
+		case *dsa.PrivateKey:
+			template.SignatureAlgorithm = x509.DSAWithSHA1
+		}
+	case x509.SHA256WithRSA:
+		priv = test2048Key
+		switch issuerKey.(type) {
+		case *rsa.PrivateKey:
+			template.SignatureAlgorithm = x509.SHA256WithRSA
+		case *ecdsa.PrivateKey:
+			template.SignatureAlgorithm = x509.ECDSAWithSHA256
+		case *dsa.PrivateKey:
+			template.SignatureAlgorithm = x509.DSAWithSHA256
+		}
+	case x509.SHA384WithRSA:
+		priv = test3072Key
+		switch issuerKey.(type) {
+		case *rsa.PrivateKey:
+			template.SignatureAlgorithm = x509.SHA384WithRSA
+		case *ecdsa.PrivateKey:
+			template.SignatureAlgorithm = x509.ECDSAWithSHA384
+		case *dsa.PrivateKey:
+			template.SignatureAlgorithm = x509.DSAWithSHA256
+		}
+	case x509.SHA512WithRSA:
+		priv = test4096Key
+		switch issuerKey.(type) {
+		case *rsa.PrivateKey:
+			template.SignatureAlgorithm = x509.SHA512WithRSA
+		case *ecdsa.PrivateKey:
+			template.SignatureAlgorithm = x509.ECDSAWithSHA512
+		case *dsa.PrivateKey:
+			template.SignatureAlgorithm = x509.DSAWithSHA256
+		}
+	case x509.ECDSAWithSHA1:
+		priv, err = ecdsa.GenerateKey(elliptic.P256(), rand.Reader)
+		if err != nil {
+			return nil, err
+		}
+		switch issuerKey.(type) {
+		case *rsa.PrivateKey:
+			template.SignatureAlgorithm = x509.SHA1WithRSA
+		case *ecdsa.PrivateKey:
+			template.SignatureAlgorithm = x509.ECDSAWithSHA1
+		case *dsa.PrivateKey:
+			template.SignatureAlgorithm = x509.DSAWithSHA1
+		}
+	case x509.ECDSAWithSHA256:
+		priv, err = ecdsa.GenerateKey(elliptic.P256(), rand.Reader)
+		if err != nil {
+			return nil, err
+		}
+		switch issuerKey.(type) {
+		case *rsa.PrivateKey:
+			template.SignatureAlgorithm = x509.SHA256WithRSA
+		case *ecdsa.PrivateKey:
+			template.SignatureAlgorithm = x509.ECDSAWithSHA256
+		case *dsa.PrivateKey:
+			template.SignatureAlgorithm = x509.DSAWithSHA256
+		}
+	case x509.ECDSAWithSHA384:
+		priv, err = ecdsa.GenerateKey(elliptic.P384(), rand.Reader)
+		if err != nil {
+			return nil, err
+		}
+		switch issuerKey.(type) {
+		case *rsa.PrivateKey:
+			template.SignatureAlgorithm = x509.SHA384WithRSA
+		case *ecdsa.PrivateKey:
+			template.SignatureAlgorithm = x509.ECDSAWithSHA384
+		case *dsa.PrivateKey:
+			template.SignatureAlgorithm = x509.DSAWithSHA256
+		}
+	case x509.ECDSAWithSHA512:
+		priv, err = ecdsa.GenerateKey(elliptic.P521(), rand.Reader)
+		if err != nil {
+			return nil, err
+		}
+		switch issuerKey.(type) {
+		case *rsa.PrivateKey:
+			template.SignatureAlgorithm = x509.SHA512WithRSA
+		case *ecdsa.PrivateKey:
+			template.SignatureAlgorithm = x509.ECDSAWithSHA512
+		case *dsa.PrivateKey:
+			template.SignatureAlgorithm = x509.DSAWithSHA256
+		}
+	case x509.DSAWithSHA1:
+		var dsaPriv dsa.PrivateKey
+		params := &dsaPriv.Parameters
+		err = dsa.GenerateParameters(params, rand.Reader, dsa.L1024N160)
+		if err != nil {
+			return nil, err
+		}
+		err = dsa.GenerateKey(&dsaPriv, rand.Reader)
+		if err != nil {
+			return nil, err
+		}
+		switch issuerKey.(type) {
+		case *rsa.PrivateKey:
+			template.SignatureAlgorithm = x509.SHA1WithRSA
+		case *ecdsa.PrivateKey:
+			template.SignatureAlgorithm = x509.ECDSAWithSHA1
+		case *dsa.PrivateKey:
+			template.SignatureAlgorithm = x509.DSAWithSHA1
+		}
+		priv = &dsaPriv
+	}
+	if isCA {
+		template.IsCA = true
+		template.KeyUsage |= x509.KeyUsageCertSign
+		template.BasicConstraintsValid = true
+	}
+	if issuer == nil {
+		// no issuer given,make this a self-signed root cert
+		issuerCert = &template
+		issuerKey = priv
+	}
+
+	log.Println("creating cert", name, "issued by", issuerCert.Subject.CommonName, "with sigalg", sigAlg)
+	switch priv.(type) {
+	case *rsa.PrivateKey:
+		switch issuerKey.(type) {
+		case *rsa.PrivateKey:
+			derCert, err = x509.CreateCertificate(rand.Reader, &template, issuerCert, priv.(*rsa.PrivateKey).Public(), issuerKey.(*rsa.PrivateKey))
+		case *ecdsa.PrivateKey:
+			derCert, err = x509.CreateCertificate(rand.Reader, &template, issuerCert, priv.(*rsa.PrivateKey).Public(), issuerKey.(*ecdsa.PrivateKey))
+		case *dsa.PrivateKey:
+			derCert, err = x509.CreateCertificate(rand.Reader, &template, issuerCert, priv.(*rsa.PrivateKey).Public(), issuerKey.(*dsa.PrivateKey))
+		}
+	case *ecdsa.PrivateKey:
+		switch issuerKey.(type) {
+		case *rsa.PrivateKey:
+			derCert, err = x509.CreateCertificate(rand.Reader, &template, issuerCert, priv.(*ecdsa.PrivateKey).Public(), issuerKey.(*rsa.PrivateKey))
+		case *ecdsa.PrivateKey:
+			derCert, err = x509.CreateCertificate(rand.Reader, &template, issuerCert, priv.(*ecdsa.PrivateKey).Public(), issuerKey.(*ecdsa.PrivateKey))
+		case *dsa.PrivateKey:
+			derCert, err = x509.CreateCertificate(rand.Reader, &template, issuerCert, priv.(*ecdsa.PrivateKey).Public(), issuerKey.(*dsa.PrivateKey))
+		}
+	case *dsa.PrivateKey:
+		pub := &priv.(*dsa.PrivateKey).PublicKey
+		switch issuerKey := issuerKey.(type) {
+		case *rsa.PrivateKey:
+			derCert, err = x509.CreateCertificate(rand.Reader, &template, issuerCert, pub, issuerKey)
+		case *ecdsa.PrivateKey:
+			derCert, err = x509.CreateCertificate(rand.Reader, &template, issuerCert, priv.(*dsa.PublicKey), issuerKey)
+		case *dsa.PrivateKey:
+			derCert, err = x509.CreateCertificate(rand.Reader, &template, issuerCert, priv.(*dsa.PublicKey), issuerKey)
+		}
+	}
+	if err != nil {
+		return nil, err
+	}
+	if len(derCert) == 0 {
+		return nil, fmt.Errorf("no certificate created, probably due to wrong keys. types were %T and %T", priv, issuerKey)
+	}
+	cert, err := x509.ParseCertificate(derCert)
+	if err != nil {
+		return nil, err
+	}
+	pem.Encode(os.Stdout, &pem.Block{Type: "CERTIFICATE", Bytes: cert.Raw})
+	return &certKeyPair{
+		Certificate: cert,
+		PrivateKey:  &priv,
+	}, nil
+}
+
+type TestFixture struct {
+	Input       []byte
+	Certificate *x509.Certificate
+	PrivateKey  *rsa.PrivateKey
+}
+
+func UnmarshalTestFixture(testPEMBlock string) TestFixture {
+	var result TestFixture
+	var derBlock *pem.Block
+	var pemBlock = []byte(testPEMBlock)
+	for {
+		derBlock, pemBlock = pem.Decode(pemBlock)
+		if derBlock == nil {
+			break
+		}
+		switch derBlock.Type {
+		case "PKCS7":
+			result.Input = derBlock.Bytes
+		case "CERTIFICATE":
+			result.Certificate, _ = x509.ParseCertificate(derBlock.Bytes)
+		case "PRIVATE KEY":
+			result.PrivateKey, _ = x509.ParsePKCS1PrivateKey(derBlock.Bytes)
+		}
+	}
+
+	return result
+}

builtin/credential/aws/pkcs7/sign.go

@@ -0,0 +1,429 @@
+package pkcs7
+
+import (
+	"bytes"
+	"crypto"
+	"crypto/dsa"
+	"crypto/rand"
+	"crypto/x509"
+	"crypto/x509/pkix"
+	"encoding/asn1"
+	"errors"
+	"fmt"
+	"math/big"
+	"time"
+)
+
+// SignedData is an opaque data structure for creating signed data payloads
+type SignedData struct {
+	sd                  signedData
+	certs               []*x509.Certificate
+	data, messageDigest []byte
+	digestOid           asn1.ObjectIdentifier
+	encryptionOid       asn1.ObjectIdentifier
+}
+
+// NewSignedData takes data and initializes a PKCS7 SignedData struct that is
+// ready to be signed via AddSigner. The digest algorithm is set to SHA1 by default
+// and can be changed by calling SetDigestAlgorithm.
+func NewSignedData(data []byte) (*SignedData, error) {
+	content, err := asn1.Marshal(data)
+	if err != nil {
+		return nil, err
+	}
+	ci := contentInfo{
+		ContentType: OIDData,
+		Content:     asn1.RawValue{Class: 2, Tag: 0, Bytes: content, IsCompound: true},
+	}
+	sd := signedData{
+		ContentInfo: ci,
+		Version:     1,
+	}
+	return &SignedData{sd: sd, data: data, digestOid: OIDDigestAlgorithmSHA1}, nil
+}
+
+// SignerInfoConfig are optional values to include when adding a signer
+type SignerInfoConfig struct {
+	ExtraSignedAttributes   []Attribute
+	ExtraUnsignedAttributes []Attribute
+}
+
+type signedData struct {
+	Version                    int                        `asn1:"default:1"`
+	DigestAlgorithmIdentifiers []pkix.AlgorithmIdentifier `asn1:"set"`
+	ContentInfo                contentInfo
+	Certificates               rawCertificates        `asn1:"optional,tag:0"`
+	CRLs                       []pkix.CertificateList `asn1:"optional,tag:1"`
+	SignerInfos                []signerInfo           `asn1:"set"`
+}
+
+type signerInfo struct {
+	Version                   int `asn1:"default:1"`
+	IssuerAndSerialNumber     issuerAndSerial
+	DigestAlgorithm           pkix.AlgorithmIdentifier
+	AuthenticatedAttributes   []attribute `asn1:"optional,omitempty,tag:0"`
+	DigestEncryptionAlgorithm pkix.AlgorithmIdentifier
+	EncryptedDigest           []byte
+	UnauthenticatedAttributes []attribute `asn1:"optional,omitempty,tag:1"`
+}
+
+type attribute struct {
+	Type  asn1.ObjectIdentifier
+	Value asn1.RawValue `asn1:"set"`
+}
+
+func marshalAttributes(attrs []attribute) ([]byte, error) {
+	encodedAttributes, err := asn1.Marshal(struct {
+		A []attribute `asn1:"set"`
+	}{A: attrs})
+	if err != nil {
+		return nil, err
+	}
+
+	// Remove the leading sequence octets
+	var raw asn1.RawValue
+	asn1.Unmarshal(encodedAttributes, &raw)
+	return raw.Bytes, nil
+}
+
+type rawCertificates struct {
+	Raw asn1.RawContent
+}
+
+type issuerAndSerial struct {
+	IssuerName   asn1.RawValue
+	SerialNumber *big.Int
+}
+
+// SetDigestAlgorithm sets the digest algorithm to be used in the signing process.
+//
+// This should be called before adding signers
+func (sd *SignedData) SetDigestAlgorithm(d asn1.ObjectIdentifier) {
+	sd.digestOid = d
+}
+
+// SetEncryptionAlgorithm sets the encryption algorithm to be used in the signing process.
+//
+// This should be called before adding signers
+func (sd *SignedData) SetEncryptionAlgorithm(d asn1.ObjectIdentifier) {
+	sd.encryptionOid = d
+}
+
+// AddSigner is a wrapper around AddSignerChain() that adds a signer without any parent.
+func (sd *SignedData) AddSigner(ee *x509.Certificate, pkey crypto.PrivateKey, config SignerInfoConfig) error {
+	var parents []*x509.Certificate
+	return sd.AddSignerChain(ee, pkey, parents, config)
+}
+
+// AddSignerChain signs attributes about the content and adds certificates
+// and signers infos to the Signed Data. The certificate and private key
+// of the end-entity signer are used to issue the signature, and any
+// parent of that end-entity that need to be added to the list of
+// certifications can be specified in the parents slice.
+//
+// The signature algorithm used to hash the data is the one of the end-entity
+// certificate.
+func (sd *SignedData) AddSignerChain(ee *x509.Certificate, pkey crypto.PrivateKey, parents []*x509.Certificate, config SignerInfoConfig) error {
+	// Following RFC 2315, 9.2 SignerInfo type, the distinguished name of
+	// the issuer of the end-entity signer is stored in the issuerAndSerialNumber
+	// section of the SignedData.SignerInfo, alongside the serial number of
+	// the end-entity.
+	var ias issuerAndSerial
+	ias.SerialNumber = ee.SerialNumber
+	if len(parents) == 0 {
+		// no parent, the issuer is the end-entity cert itself
+		ias.IssuerName = asn1.RawValue{FullBytes: ee.RawIssuer}
+	} else {
+		err := verifyPartialChain(ee, parents)
+		if err != nil {
+			return err
+		}
+		// the first parent is the issuer
+		ias.IssuerName = asn1.RawValue{FullBytes: parents[0].RawSubject}
+	}
+	sd.sd.DigestAlgorithmIdentifiers = append(sd.sd.DigestAlgorithmIdentifiers,
+		pkix.AlgorithmIdentifier{Algorithm: sd.digestOid},
+	)
+	hash, err := getHashForOID(sd.digestOid)
+	if err != nil {
+		return err
+	}
+	h := hash.New()
+	h.Write(sd.data)
+	sd.messageDigest = h.Sum(nil)
+	encryptionOid, err := getOIDForEncryptionAlgorithm(pkey, sd.digestOid)
+	if err != nil {
+		return err
+	}
+	attrs := &attributes{}
+	attrs.Add(OIDAttributeContentType, sd.sd.ContentInfo.ContentType)
+	attrs.Add(OIDAttributeMessageDigest, sd.messageDigest)
+	attrs.Add(OIDAttributeSigningTime, time.Now().UTC())
+	for _, attr := range config.ExtraSignedAttributes {
+		attrs.Add(attr.Type, attr.Value)
+	}
+	finalAttrs, err := attrs.ForMarshalling()
+	if err != nil {
+		return err
+	}
+	unsignedAttrs := &attributes{}
+	for _, attr := range config.ExtraUnsignedAttributes {
+		unsignedAttrs.Add(attr.Type, attr.Value)
+	}
+	finalUnsignedAttrs, err := unsignedAttrs.ForMarshalling()
+	if err != nil {
+		return err
+	}
+	// create signature of signed attributes
+	signature, err := signAttributes(finalAttrs, pkey, hash)
+	if err != nil {
+		return err
+	}
+	signer := signerInfo{
+		AuthenticatedAttributes:   finalAttrs,
+		UnauthenticatedAttributes: finalUnsignedAttrs,
+		DigestAlgorithm:           pkix.AlgorithmIdentifier{Algorithm: sd.digestOid},
+		DigestEncryptionAlgorithm: pkix.AlgorithmIdentifier{Algorithm: encryptionOid},
+		IssuerAndSerialNumber:     ias,
+		EncryptedDigest:           signature,
+		Version:                   1,
+	}
+	sd.certs = append(sd.certs, ee)
+	if len(parents) > 0 {
+		sd.certs = append(sd.certs, parents...)
+	}
+	sd.sd.SignerInfos = append(sd.sd.SignerInfos, signer)
+	return nil
+}
+
+// SignWithoutAttr issues a signature on the content of the pkcs7 SignedData.
+// Unlike AddSigner/AddSignerChain, it calculates the digest on the data alone
+// and does not include any signed attributes like timestamp and so on.
+//
+// This function is needed to sign old Android APKs, something you probably
+// shouldn't do unless you're maintaining backward compatibility for old
+// applications.
+func (sd *SignedData) SignWithoutAttr(ee *x509.Certificate, pkey crypto.PrivateKey, config SignerInfoConfig) error {
+	var signature []byte
+	sd.sd.DigestAlgorithmIdentifiers = append(sd.sd.DigestAlgorithmIdentifiers, pkix.AlgorithmIdentifier{Algorithm: sd.digestOid})
+	hash, err := getHashForOID(sd.digestOid)
+	if err != nil {
+		return err
+	}
+	h := hash.New()
+	h.Write(sd.data)
+	sd.messageDigest = h.Sum(nil)
+	switch pkey := pkey.(type) {
+	case *dsa.PrivateKey:
+		// dsa doesn't implement crypto.Signer so we make a special case
+		// https://github.com/golang/go/issues/27889
+		r, s, err := dsa.Sign(rand.Reader, pkey, sd.messageDigest)
+		if err != nil {
+			return err
+		}
+		signature, err = asn1.Marshal(dsaSignature{r, s})
+		if err != nil {
+			return err
+		}
+	default:
+		key, ok := pkey.(crypto.Signer)
+		if !ok {
+			return errors.New("pkcs7: private key does not implement crypto.Signer")
+		}
+		signature, err = key.Sign(rand.Reader, sd.messageDigest, hash)
+		if err != nil {
+			return err
+		}
+	}
+	var ias issuerAndSerial
+	ias.SerialNumber = ee.SerialNumber
+	// no parent, the issue is the end-entity cert itself
+	ias.IssuerName = asn1.RawValue{FullBytes: ee.RawIssuer}
+	if sd.encryptionOid == nil {
+		// if the encryption algorithm wasn't set by SetEncryptionAlgorithm,
+		// infer it from the digest algorithm
+		sd.encryptionOid, err = getOIDForEncryptionAlgorithm(pkey, sd.digestOid)
+	}
+	if err != nil {
+		return err
+	}
+	signer := signerInfo{
+		DigestAlgorithm:           pkix.AlgorithmIdentifier{Algorithm: sd.digestOid},
+		DigestEncryptionAlgorithm: pkix.AlgorithmIdentifier{Algorithm: sd.encryptionOid},
+		IssuerAndSerialNumber:     ias,
+		EncryptedDigest:           signature,
+		Version:                   1,
+	}
+	// create signature of signed attributes
+	sd.certs = append(sd.certs, ee)
+	sd.sd.SignerInfos = append(sd.sd.SignerInfos, signer)
+	return nil
+}
+
+func (si *signerInfo) SetUnauthenticatedAttributes(extraUnsignedAttrs []Attribute) error {
+	unsignedAttrs := &attributes{}
+	for _, attr := range extraUnsignedAttrs {
+		unsignedAttrs.Add(attr.Type, attr.Value)
+	}
+	finalUnsignedAttrs, err := unsignedAttrs.ForMarshalling()
+	if err != nil {
+		return err
+	}
+
+	si.UnauthenticatedAttributes = finalUnsignedAttrs
+
+	return nil
+}
+
+// AddCertificate adds the certificate to the payload. Useful for parent certificates
+func (sd *SignedData) AddCertificate(cert *x509.Certificate) {
+	sd.certs = append(sd.certs, cert)
+}
+
+// Detach removes content from the signed data struct to make it a detached signature.
+// This must be called right before Finish()
+func (sd *SignedData) Detach() {
+	sd.sd.ContentInfo = contentInfo{ContentType: OIDData}
+}
+
+// GetSignedData returns the private Signed Data
+func (sd *SignedData) GetSignedData() *signedData {
+	return &sd.sd
+}
+
+// Finish marshals the content and its signers
+func (sd *SignedData) Finish() ([]byte, error) {
+	sd.sd.Certificates = marshalCertificates(sd.certs)
+	inner, err := asn1.Marshal(sd.sd)
+	if err != nil {
+		return nil, err
+	}
+	outer := contentInfo{
+		ContentType: OIDSignedData,
+		Content:     asn1.RawValue{Class: 2, Tag: 0, Bytes: inner, IsCompound: true},
+	}
+	return asn1.Marshal(outer)
+}
+
+// RemoveAuthenticatedAttributes removes authenticated attributes from signedData
+// similar to OpenSSL's PKCS7_NOATTR or -noattr flags
+func (sd *SignedData) RemoveAuthenticatedAttributes() {
+	for i := range sd.sd.SignerInfos {
+		sd.sd.SignerInfos[i].AuthenticatedAttributes = nil
+	}
+}
+
+// RemoveUnauthenticatedAttributes removes unauthenticated attributes from signedData
+func (sd *SignedData) RemoveUnauthenticatedAttributes() {
+	for i := range sd.sd.SignerInfos {
+		sd.sd.SignerInfos[i].UnauthenticatedAttributes = nil
+	}
+}
+
+// verifyPartialChain checks that a given cert is issued by the first parent in the list,
+// then continue down the path. It doesn't require the last parent to be a root CA,
+// or to be trusted in any truststore. It simply verifies that the chain provided, albeit
+// partial, makes sense.
+func verifyPartialChain(cert *x509.Certificate, parents []*x509.Certificate) error {
+	if len(parents) == 0 {
+		return fmt.Errorf("pkcs7: zero parents provided to verify the signature of certificate %q", cert.Subject.CommonName)
+	}
+	err := cert.CheckSignatureFrom(parents[0])
+	if err != nil {
+		return fmt.Errorf("pkcs7: certificate signature from parent is invalid: %v", err)
+	}
+	if len(parents) == 1 {
+		// there is no more parent to check, return
+		return nil
+	}
+	return verifyPartialChain(parents[0], parents[1:])
+}
+
+func cert2issuerAndSerial(cert *x509.Certificate) (issuerAndSerial, error) {
+	var ias issuerAndSerial
+	// The issuer RDNSequence has to match exactly the sequence in the certificate
+	// We cannot use cert.Issuer.ToRDNSequence() here since it mangles the sequence
+	ias.IssuerName = asn1.RawValue{FullBytes: cert.RawIssuer}
+	ias.SerialNumber = cert.SerialNumber
+
+	return ias, nil
+}
+
+// signs the DER encoded form of the attributes with the private key
+func signAttributes(attrs []attribute, pkey crypto.PrivateKey, digestAlg crypto.Hash) ([]byte, error) {
+	attrBytes, err := marshalAttributes(attrs)
+	if err != nil {
+		return nil, err
+	}
+	h := digestAlg.New()
+	h.Write(attrBytes)
+	hash := h.Sum(nil)
+
+	// dsa doesn't implement crypto.Signer so we make a special case
+	// https://github.com/golang/go/issues/27889
+	switch pkey := pkey.(type) {
+	case *dsa.PrivateKey:
+		r, s, err := dsa.Sign(rand.Reader, pkey, hash)
+		if err != nil {
+			return nil, err
+		}
+		return asn1.Marshal(dsaSignature{r, s})
+	}
+
+	key, ok := pkey.(crypto.Signer)
+	if !ok {
+		return nil, errors.New("pkcs7: private key does not implement crypto.Signer")
+	}
+	return key.Sign(rand.Reader, hash, digestAlg)
+}
+
+type dsaSignature struct {
+	R, S *big.Int
+}
+
+// concats and wraps the certificates in the RawValue structure
+func marshalCertificates(certs []*x509.Certificate) rawCertificates {
+	var buf bytes.Buffer
+	for _, cert := range certs {
+		buf.Write(cert.Raw)
+	}
+	rawCerts, _ := marshalCertificateBytes(buf.Bytes())
+	return rawCerts
+}
+
+// Even though, the tag & length are stripped out during marshalling the
+// RawContent, we have to encode it into the RawContent. If its missing,
+// then `asn1.Marshal()` will strip out the certificate wrapper instead.
+func marshalCertificateBytes(certs []byte) (rawCertificates, error) {
+	var val = asn1.RawValue{Bytes: certs, Class: 2, Tag: 0, IsCompound: true}
+	b, err := asn1.Marshal(val)
+	if err != nil {
+		return rawCertificates{}, err
+	}
+	return rawCertificates{Raw: b}, nil
+}
+
+// DegenerateCertificate creates a signed data structure containing only the
+// provided certificate or certificate chain.
+func DegenerateCertificate(cert []byte) ([]byte, error) {
+	rawCert, err := marshalCertificateBytes(cert)
+	if err != nil {
+		return nil, err
+	}
+	emptyContent := contentInfo{ContentType: OIDData}
+	sd := signedData{
+		Version:      1,
+		ContentInfo:  emptyContent,
+		Certificates: rawCert,
+		CRLs:         []pkix.CertificateList{},
+	}
+	content, err := asn1.Marshal(sd)
+	if err != nil {
+		return nil, err
+	}
+	signedContent := contentInfo{
+		ContentType: OIDSignedData,
+		Content:     asn1.RawValue{Class: 2, Tag: 0, Bytes: content, IsCompound: true},
+	}
+	return asn1.Marshal(signedContent)
+}

builtin/credential/aws/pkcs7/sign_test.go

@@ -0,0 +1,266 @@
+package pkcs7
+
+import (
+	"bytes"
+	"crypto/dsa"
+	"crypto/x509"
+	"encoding/asn1"
+	"encoding/pem"
+	"fmt"
+	"io/ioutil"
+	"log"
+	"math/big"
+	"os"
+	"os/exec"
+	"testing"
+)
+
+func TestSign(t *testing.T) {
+	content := []byte("Hello World")
+	sigalgs := []x509.SignatureAlgorithm{
+		x509.SHA1WithRSA,
+		x509.SHA256WithRSA,
+		x509.SHA512WithRSA,
+		x509.ECDSAWithSHA1,
+		x509.ECDSAWithSHA256,
+		x509.ECDSAWithSHA384,
+		x509.ECDSAWithSHA512,
+	}
+	for _, sigalgroot := range sigalgs {
+		rootCert, err := createTestCertificateByIssuer("PKCS7 Test Root CA", nil, sigalgroot, true)
+		if err != nil {
+			t.Fatalf("test %s: cannot generate root cert: %s", sigalgroot, err)
+		}
+		truststore := x509.NewCertPool()
+		truststore.AddCert(rootCert.Certificate)
+		for _, sigalginter := range sigalgs {
+			interCert, err := createTestCertificateByIssuer("PKCS7 Test Intermediate Cert", rootCert, sigalginter, true)
+			if err != nil {
+				t.Fatalf("test %s/%s: cannot generate intermediate cert: %s", sigalgroot, sigalginter, err)
+			}
+			var parents []*x509.Certificate
+			parents = append(parents, interCert.Certificate)
+			for _, sigalgsigner := range sigalgs {
+				signerCert, err := createTestCertificateByIssuer("PKCS7 Test Signer Cert", interCert, sigalgsigner, false)
+				if err != nil {
+					t.Fatalf("test %s/%s/%s: cannot generate signer cert: %s", sigalgroot, sigalginter, sigalgsigner, err)
+				}
+				for _, testDetach := range []bool{false, true} {
+					log.Printf("test %s/%s/%s detached %t\n", sigalgroot, sigalginter, sigalgsigner, testDetach)
+					toBeSigned, err := NewSignedData(content)
+					if err != nil {
+						t.Fatalf("test %s/%s/%s: cannot initialize signed data: %s", sigalgroot, sigalginter, sigalgsigner, err)
+					}
+
+					// Set the digest to match the end entity cert
+					signerDigest, _ := getDigestOIDForSignatureAlgorithm(signerCert.Certificate.SignatureAlgorithm)
+					toBeSigned.SetDigestAlgorithm(signerDigest)
+
+					if err := toBeSigned.AddSignerChain(signerCert.Certificate, *signerCert.PrivateKey, parents, SignerInfoConfig{}); err != nil {
+						t.Fatalf("test %s/%s/%s: cannot add signer: %s", sigalgroot, sigalginter, sigalgsigner, err)
+					}
+					if testDetach {
+						toBeSigned.Detach()
+					}
+					signed, err := toBeSigned.Finish()
+					if err != nil {
+						t.Fatalf("test %s/%s/%s: cannot finish signing data: %s", sigalgroot, sigalginter, sigalgsigner, err)
+					}
+					pem.Encode(os.Stdout, &pem.Block{Type: "PKCS7", Bytes: signed})
+					p7, err := Parse(signed)
+					if err != nil {
+						t.Fatalf("test %s/%s/%s: cannot parse signed data: %s", sigalgroot, sigalginter, sigalgsigner, err)
+					}
+					if testDetach {
+						p7.Content = content
+					}
+					if !bytes.Equal(content, p7.Content) {
+						t.Errorf("test %s/%s/%s: content was not found in the parsed data:\n\tExpected: %s\n\tActual: %s", sigalgroot, sigalginter, sigalgsigner, content, p7.Content)
+					}
+					if err := p7.VerifyWithChain(truststore); err != nil {
+						t.Errorf("test %s/%s/%s: cannot verify signed data: %s", sigalgroot, sigalginter, sigalgsigner, err)
+					}
+					if !signerDigest.Equal(p7.Signers[0].DigestAlgorithm.Algorithm) {
+						t.Errorf("test %s/%s/%s: expected digest algorithm %q but got %q",
+							sigalgroot, sigalginter, sigalgsigner, signerDigest, p7.Signers[0].DigestAlgorithm.Algorithm)
+					}
+				}
+			}
+		}
+	}
+}
+
+func TestDSASignAndVerifyWithOpenSSL(t *testing.T) {
+	content := []byte("Hello World")
+	// write the content to a temp file
+	tmpContentFile, err := ioutil.TempFile("", "TestDSASignAndVerifyWithOpenSSL_content")
+	if err != nil {
+		t.Fatal(err)
+	}
+	ioutil.WriteFile(tmpContentFile.Name(), content, 0755)
+
+	block, _ := pem.Decode([]byte(dsaPublicCert))
+	if block == nil {
+		t.Fatal("failed to parse certificate PEM")
+	}
+	signerCert, err := x509.ParseCertificate(block.Bytes)
+	if err != nil {
+		t.Fatal("failed to parse certificate: " + err.Error())
+	}
+
+	// write the signer cert to a temp file
+	tmpSignerCertFile, err := ioutil.TempFile("", "TestDSASignAndVerifyWithOpenSSL_signer")
+	if err != nil {
+		t.Fatal(err)
+	}
+	ioutil.WriteFile(tmpSignerCertFile.Name(), dsaPublicCert, 0755)
+
+	priv := dsa.PrivateKey{
+		PublicKey: dsa.PublicKey{Parameters: dsa.Parameters{P: fromHex("fd7f53811d75122952df4a9c2eece4e7f611b7523cef4400c31e3f80b6512669455d402251fb593d8d58fabfc5f5ba30f6cb9b556cd7813b801d346ff26660b76b9950a5a49f9fe8047b1022c24fbba9d7feb7c61bf83b57e7c6a8a6150f04fb83f6d3c51ec3023554135a169132f675f3ae2b61d72aeff22203199dd14801c7"),
+			Q: fromHex("9760508F15230BCCB292B982A2EB840BF0581CF5"),
+			G: fromHex("F7E1A085D69B3DDECBBCAB5C36B857B97994AFBBFA3AEA82F9574C0B3D0782675159578EBAD4594FE67107108180B449167123E84C281613B7CF09328CC8A6E13C167A8B547C8D28E0A3AE1E2BB3A675916EA37F0BFA213562F1FB627A01243BCCA4F1BEA8519089A883DFE15AE59F06928B665E807B552564014C3BFECF492A"),
+		},
+		},
+		X: fromHex("7D6E1A3DD4019FD809669D8AB8DA73807CEF7EC1"),
+	}
+	toBeSigned, err := NewSignedData(content)
+	if err != nil {
+		t.Fatalf("test case: cannot initialize signed data: %s", err)
+	}
+	if err := toBeSigned.SignWithoutAttr(signerCert, &priv, SignerInfoConfig{}); err != nil {
+		t.Fatalf("Cannot add signer: %s", err)
+	}
+	toBeSigned.Detach()
+	signed, err := toBeSigned.Finish()
+	if err != nil {
+		t.Fatalf("test case: cannot finish signing data: %s", err)
+	}
+
+	// write the signature to a temp file
+	tmpSignatureFile, err := ioutil.TempFile("", "TestDSASignAndVerifyWithOpenSSL_signature")
+	if err != nil {
+		t.Fatal(err)
+	}
+	ioutil.WriteFile(tmpSignatureFile.Name(), pem.EncodeToMemory(&pem.Block{Type: "PKCS7", Bytes: signed}), 0755)
+
+	// call openssl to verify the signature on the content using the root
+	opensslCMD := exec.Command("openssl", "smime", "-verify", "-noverify",
+		"-in", tmpSignatureFile.Name(), "-inform", "PEM",
+		"-content", tmpContentFile.Name())
+	out, err := opensslCMD.CombinedOutput()
+	if err != nil {
+		t.Fatalf("test case: openssl command failed with %s: %s", err, out)
+	}
+	os.Remove(tmpSignatureFile.Name())  // clean up
+	os.Remove(tmpContentFile.Name())    // clean up
+	os.Remove(tmpSignerCertFile.Name()) // clean up
+}
+
+func ExampleSignedData() {
+	// generate a signing cert or load a key pair
+	cert, err := createTestCertificate(x509.SHA256WithRSA)
+	if err != nil {
+		fmt.Printf("Cannot create test certificates: %s", err)
+	}
+
+	// Initialize a SignedData struct with content to be signed
+	signedData, err := NewSignedData([]byte("Example data to be signed"))
+	if err != nil {
+		fmt.Printf("Cannot initialize signed data: %s", err)
+	}
+
+	// Add the signing cert and private key
+	if err := signedData.AddSigner(cert.Certificate, cert.PrivateKey, SignerInfoConfig{}); err != nil {
+		fmt.Printf("Cannot add signer: %s", err)
+	}
+
+	// Call Detach() is you want to remove content from the signature
+	// and generate an S/MIME detached signature
+	signedData.Detach()
+
+	// Finish() to obtain the signature bytes
+	detachedSignature, err := signedData.Finish()
+	if err != nil {
+		fmt.Printf("Cannot finish signing data: %s", err)
+	}
+	pem.Encode(os.Stdout, &pem.Block{Type: "PKCS7", Bytes: detachedSignature})
+}
+
+func TestUnmarshalSignedAttribute(t *testing.T) {
+	cert, err := createTestCertificate(x509.SHA512WithRSA)
+	if err != nil {
+		t.Fatal(err)
+	}
+	content := []byte("Hello World")
+	toBeSigned, err := NewSignedData(content)
+	if err != nil {
+		t.Fatalf("Cannot initialize signed data: %s", err)
+	}
+	oidTest := asn1.ObjectIdentifier{2, 3, 4, 5, 6, 7}
+	testValue := "TestValue"
+	if err := toBeSigned.AddSigner(cert.Certificate, *cert.PrivateKey, SignerInfoConfig{
+		ExtraSignedAttributes: []Attribute{Attribute{Type: oidTest, Value: testValue}},
+	}); err != nil {
+		t.Fatalf("Cannot add signer: %s", err)
+	}
+	signed, err := toBeSigned.Finish()
+	if err != nil {
+		t.Fatalf("Cannot finish signing data: %s", err)
+	}
+	p7, err := Parse(signed)
+	if err != nil {
+		t.Fatalf("Cannot parse signed data: %v", err)
+	}
+	var actual string
+	err = p7.UnmarshalSignedAttribute(oidTest, &actual)
+	if err != nil {
+		t.Fatalf("Cannot unmarshal test value: %s", err)
+	}
+	if testValue != actual {
+		t.Errorf("Attribute does not match test value\n\tExpected: %s\n\tActual: %s", testValue, actual)
+	}
+}
+
+func TestDegenerateCertificate(t *testing.T) {
+	cert, err := createTestCertificate(x509.SHA1WithRSA)
+	if err != nil {
+		t.Fatal(err)
+	}
+	deg, err := DegenerateCertificate(cert.Certificate.Raw)
+	if err != nil {
+		t.Fatal(err)
+	}
+	testOpenSSLParse(t, deg)
+	pem.Encode(os.Stdout, &pem.Block{Type: "PKCS7", Bytes: deg})
+}
+
+// writes the cert to a temporary file and tests that openssl can read it.
+func testOpenSSLParse(t *testing.T, certBytes []byte) {
+	tmpCertFile, err := ioutil.TempFile("", "testCertificate")
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer os.Remove(tmpCertFile.Name()) // clean up
+
+	if _, err := tmpCertFile.Write(certBytes); err != nil {
+		t.Fatal(err)
+	}
+
+	opensslCMD := exec.Command("openssl", "pkcs7", "-inform", "der", "-in", tmpCertFile.Name())
+	_, err = opensslCMD.Output()
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	if err := tmpCertFile.Close(); err != nil {
+		t.Fatal(err)
+	}
+
+}
+func fromHex(s string) *big.Int {
+	result, ok := new(big.Int).SetString(s, 16)
+	if !ok {
+		panic(s)
+	}
+	return result
+}

builtin/credential/aws/pkcs7/verify.go

@@ -0,0 +1,399 @@
+package pkcs7
+
+import (
+	"crypto"
+	"crypto/dsa"
+	"crypto/subtle"
+	"crypto/x509"
+	"crypto/x509/pkix"
+	"encoding/asn1"
+	"errors"
+	"fmt"
+	"time"
+)
+
+// Verify is a wrapper around VerifyWithChain() that initializes an empty
+// trust store, effectively disabling certificate verification when validating
+// a signature.
+func (p7 *PKCS7) Verify() (err error) {
+	return p7.VerifyWithChain(nil)
+}
+
+// VerifyWithChain checks the signatures of a PKCS7 object.
+//
+// If truststore is not nil, it also verifies the chain of trust of
+// the end-entity signer cert to one of the roots in the
+// truststore. When the PKCS7 object includes the signing time
+// authenticated attr verifies the chain at that time and UTC now
+// otherwise.
+func (p7 *PKCS7) VerifyWithChain(truststore *x509.CertPool) (err error) {
+	if len(p7.Signers) == 0 {
+		return errors.New("pkcs7: Message has no signers")
+	}
+	for _, signer := range p7.Signers {
+		if err := verifySignature(p7, signer, truststore); err != nil {
+			return err
+		}
+	}
+	return nil
+}
+
+// VerifyWithChainAtTime checks the signatures of a PKCS7 object.
+//
+// If truststore is not nil, it also verifies the chain of trust of
+// the end-entity signer cert to a root in the truststore at
+// currentTime. It does not use the signing time authenticated
+// attribute.
+func (p7 *PKCS7) VerifyWithChainAtTime(truststore *x509.CertPool, currentTime time.Time) (err error) {
+	if len(p7.Signers) == 0 {
+		return errors.New("pkcs7: Message has no signers")
+	}
+	for _, signer := range p7.Signers {
+		if err := verifySignatureAtTime(p7, signer, truststore, currentTime); err != nil {
+			return err
+		}
+	}
+	return nil
+}
+
+func verifySignatureAtTime(p7 *PKCS7, signer signerInfo, truststore *x509.CertPool, currentTime time.Time) (err error) {
+	signedData := p7.Content
+	ee := getCertFromCertsByIssuerAndSerial(p7.Certificates, signer.IssuerAndSerialNumber)
+	if ee == nil {
+		return errors.New("pkcs7: No certificate for signer")
+	}
+	if len(signer.AuthenticatedAttributes) > 0 {
+		// TODO(fullsailor): First check the content type match
+		var (
+			digest      []byte
+			signingTime time.Time
+		)
+		err := unmarshalAttribute(signer.AuthenticatedAttributes, OIDAttributeMessageDigest, &digest)
+		if err != nil {
+			return err
+		}
+		hash, err := getHashForOID(signer.DigestAlgorithm.Algorithm)
+		if err != nil {
+			return err
+		}
+		h := hash.New()
+		h.Write(p7.Content)
+		computed := h.Sum(nil)
+		if subtle.ConstantTimeCompare(digest, computed) != 1 {
+			return &MessageDigestMismatchError{
+				ExpectedDigest: digest,
+				ActualDigest:   computed,
+			}
+		}
+		signedData, err = marshalAttributes(signer.AuthenticatedAttributes)
+		if err != nil {
+			return err
+		}
+		err = unmarshalAttribute(signer.AuthenticatedAttributes, OIDAttributeSigningTime, &signingTime)
+		if err == nil {
+			// signing time found, performing validity check
+			if signingTime.After(ee.NotAfter) || signingTime.Before(ee.NotBefore) {
+				return fmt.Errorf("pkcs7: signing time %q is outside of certificate validity %q to %q",
+					signingTime.Format(time.RFC3339),
+					ee.NotBefore.Format(time.RFC3339),
+					ee.NotAfter.Format(time.RFC3339))
+			}
+		}
+	}
+	if truststore != nil {
+		_, err = verifyCertChain(ee, p7.Certificates, truststore, currentTime)
+		if err != nil {
+			return err
+		}
+	}
+	sigalg, err := getSignatureAlgorithm(signer.DigestEncryptionAlgorithm, signer.DigestAlgorithm)
+	if err != nil {
+		return err
+	}
+	switch sigalg {
+	case x509.DSAWithSHA1, x509.DSAWithSHA256:
+		return dsaCheckSignature(sigalg, signedData, signer.EncryptedDigest, ee.PublicKey)
+	default:
+		return ee.CheckSignature(sigalg, signedData, signer.EncryptedDigest)
+	}
+}
+
+// dsaSignature verifies the DSA signature on a PKCS7 document. DSA support was
+// removed from Go's crypto/x509 support prior to Go 1.16. This allows
+// verifying legacy signatures until affected applications can be migrated off
+// of DSA.
+func dsaCheckSignature(algo x509.SignatureAlgorithm, signed, signature []byte, publicKey crypto.PublicKey) error {
+	dsaKey, ok := publicKey.(*dsa.PublicKey)
+	if !ok {
+		return ErrUnsupportedAlgorithm
+	}
+
+	var hashType crypto.Hash
+	switch algo {
+	case x509.DSAWithSHA1:
+		hashType = crypto.SHA1
+	case x509.DSAWithSHA256:
+		hashType = crypto.SHA256
+	default:
+		return ErrUnsupportedAlgorithm
+	}
+	h := hashType.New()
+	h.Write(signed)
+	signed = h.Sum(nil)
+
+	dsaSig := new(dsaSignature)
+	if rest, err := asn1.Unmarshal(signature, dsaSig); err != nil {
+		return err
+	} else if len(rest) != 0 {
+		return errors.New("x509: trailing data after DSA signature")
+	}
+	if dsaSig.R.Sign() <= 0 || dsaSig.S.Sign() <= 0 {
+		return errors.New("x509: DSA signature contained zero or negative values")
+	}
+	// According to FIPS 186-3, section 4.6, the hash must be truncated if it is longer
+	// than the key length, but crypto/dsa doesn't do it automatically.
+	if maxHashLen := dsaKey.Q.BitLen() / 8; maxHashLen < len(signed) {
+		signed = signed[:maxHashLen]
+	}
+	if !dsa.Verify(dsaKey, signed, dsaSig.R, dsaSig.S) {
+		return errors.New("x509: DSA verification failure")
+	}
+	return nil
+}
+
+func verifySignature(p7 *PKCS7, signer signerInfo, truststore *x509.CertPool) (err error) {
+	signedData := p7.Content
+	ee := getCertFromCertsByIssuerAndSerial(p7.Certificates, signer.IssuerAndSerialNumber)
+	if ee == nil {
+		return errors.New("pkcs7: No certificate for signer")
+	}
+	signingTime := time.Now().UTC()
+	if len(signer.AuthenticatedAttributes) > 0 {
+		// TODO(fullsailor): First check the content type match
+		var digest []byte
+		err := unmarshalAttribute(signer.AuthenticatedAttributes, OIDAttributeMessageDigest, &digest)
+		if err != nil {
+			return err
+		}
+		hash, err := getHashForOID(signer.DigestAlgorithm.Algorithm)
+		if err != nil {
+			return err
+		}
+		h := hash.New()
+		h.Write(p7.Content)
+		computed := h.Sum(nil)
+		if subtle.ConstantTimeCompare(digest, computed) != 1 {
+			return &MessageDigestMismatchError{
+				ExpectedDigest: digest,
+				ActualDigest:   computed,
+			}
+		}
+		signedData, err = marshalAttributes(signer.AuthenticatedAttributes)
+		if err != nil {
+			return err
+		}
+		err = unmarshalAttribute(signer.AuthenticatedAttributes, OIDAttributeSigningTime, &signingTime)
+		if err == nil {
+			// signing time found, performing validity check
+			if signingTime.After(ee.NotAfter) || signingTime.Before(ee.NotBefore) {
+				return fmt.Errorf("pkcs7: signing time %q is outside of certificate validity %q to %q",
+					signingTime.Format(time.RFC3339),
+					ee.NotBefore.Format(time.RFC3339),
+					ee.NotAfter.Format(time.RFC3339))
+			}
+		}
+	}
+	if truststore != nil {
+		_, err = verifyCertChain(ee, p7.Certificates, truststore, signingTime)
+		if err != nil {
+			return err
+		}
+	}
+	sigalg, err := getSignatureAlgorithm(signer.DigestEncryptionAlgorithm, signer.DigestAlgorithm)
+	if err != nil {
+		return err
+	}
+
+	switch sigalg {
+	case x509.DSAWithSHA1, x509.DSAWithSHA256:
+		return dsaCheckSignature(sigalg, signedData, signer.EncryptedDigest, ee.PublicKey)
+	default:
+		return ee.CheckSignature(sigalg, signedData, signer.EncryptedDigest)
+	}
+}
+
+// GetOnlySigner returns an x509.Certificate for the first signer of the signed
+// data payload. If there are more or less than one signer, nil is returned
+func (p7 *PKCS7) GetOnlySigner() *x509.Certificate {
+	if len(p7.Signers) != 1 {
+		return nil
+	}
+	signer := p7.Signers[0]
+	return getCertFromCertsByIssuerAndSerial(p7.Certificates, signer.IssuerAndSerialNumber)
+}
+
+// UnmarshalSignedAttribute decodes a single attribute from the signer info
+func (p7 *PKCS7) UnmarshalSignedAttribute(attributeType asn1.ObjectIdentifier, out interface{}) error {
+	sd, ok := p7.raw.(signedData)
+	if !ok {
+		return errors.New("pkcs7: payload is not signedData content")
+	}
+	if len(sd.SignerInfos) < 1 {
+		return errors.New("pkcs7: payload has no signers")
+	}
+	attributes := sd.SignerInfos[0].AuthenticatedAttributes
+	return unmarshalAttribute(attributes, attributeType, out)
+}
+
+func parseSignedData(data []byte) (*PKCS7, error) {
+	var sd signedData
+	asn1.Unmarshal(data, &sd)
+	certs, err := sd.Certificates.Parse()
+	if err != nil {
+		return nil, err
+	}
+	// fmt.Printf("--> Signed Data Version %d\n", sd.Version)
+
+	var compound asn1.RawValue
+	var content unsignedData
+
+	// The Content.Bytes maybe empty on PKI responses.
+	if len(sd.ContentInfo.Content.Bytes) > 0 {
+		if _, err := asn1.Unmarshal(sd.ContentInfo.Content.Bytes, &compound); err != nil {
+			return nil, err
+		}
+	}
+	// Compound octet string
+	if compound.IsCompound {
+		if compound.Tag == 4 {
+			if _, err = asn1.Unmarshal(compound.Bytes, &content); err != nil {
+				return nil, err
+			}
+		} else {
+			content = compound.Bytes
+		}
+	} else {
+		// assuming this is tag 04
+		content = compound.Bytes
+	}
+	return &PKCS7{
+		Content:      content,
+		Certificates: certs,
+		CRLs:         sd.CRLs,
+		Signers:      sd.SignerInfos,
+		raw:          sd}, nil
+}
+
+// verifyCertChain takes an end-entity certs, a list of potential intermediates and a
+// truststore, and built all potential chains between the EE and a trusted root.
+//
+// When verifying chains that may have expired, currentTime can be set to a past date
+// to allow the verification to pass. If unset, currentTime is set to the current UTC time.
+func verifyCertChain(ee *x509.Certificate, certs []*x509.Certificate, truststore *x509.CertPool, currentTime time.Time) (chains [][]*x509.Certificate, err error) {
+	intermediates := x509.NewCertPool()
+	for _, intermediate := range certs {
+		intermediates.AddCert(intermediate)
+	}
+	verifyOptions := x509.VerifyOptions{
+		Roots:         truststore,
+		Intermediates: intermediates,
+		KeyUsages:     []x509.ExtKeyUsage{x509.ExtKeyUsageAny},
+		CurrentTime:   currentTime,
+	}
+	chains, err = ee.Verify(verifyOptions)
+	if err != nil {
+		return chains, fmt.Errorf("pkcs7: failed to verify certificate chain: %v", err)
+	}
+	return
+}
+
+// MessageDigestMismatchError is returned when the signer data digest does not
+// match the computed digest for the contained content
+type MessageDigestMismatchError struct {
+	ExpectedDigest []byte
+	ActualDigest   []byte
+}
+
+func (err *MessageDigestMismatchError) Error() string {
+	return fmt.Sprintf("pkcs7: Message digest mismatch\n\tExpected: %X\n\tActual  : %X", err.ExpectedDigest, err.ActualDigest)
+}
+
+func getSignatureAlgorithm(digestEncryption, digest pkix.AlgorithmIdentifier) (x509.SignatureAlgorithm, error) {
+	switch {
+	case digestEncryption.Algorithm.Equal(OIDDigestAlgorithmECDSASHA1):
+		return x509.ECDSAWithSHA1, nil
+	case digestEncryption.Algorithm.Equal(OIDDigestAlgorithmECDSASHA256):
+		return x509.ECDSAWithSHA256, nil
+	case digestEncryption.Algorithm.Equal(OIDDigestAlgorithmECDSASHA384):
+		return x509.ECDSAWithSHA384, nil
+	case digestEncryption.Algorithm.Equal(OIDDigestAlgorithmECDSASHA512):
+		return x509.ECDSAWithSHA512, nil
+	case digestEncryption.Algorithm.Equal(OIDEncryptionAlgorithmRSA),
+		digestEncryption.Algorithm.Equal(OIDEncryptionAlgorithmRSASHA1),
+		digestEncryption.Algorithm.Equal(OIDEncryptionAlgorithmRSASHA256),
+		digestEncryption.Algorithm.Equal(OIDEncryptionAlgorithmRSASHA384),
+		digestEncryption.Algorithm.Equal(OIDEncryptionAlgorithmRSASHA512):
+		switch {
+		case digest.Algorithm.Equal(OIDDigestAlgorithmSHA1):
+			return x509.SHA1WithRSA, nil
+		case digest.Algorithm.Equal(OIDDigestAlgorithmSHA256):
+			return x509.SHA256WithRSA, nil
+		case digest.Algorithm.Equal(OIDDigestAlgorithmSHA384):
+			return x509.SHA384WithRSA, nil
+		case digest.Algorithm.Equal(OIDDigestAlgorithmSHA512):
+			return x509.SHA512WithRSA, nil
+		default:
+			return -1, fmt.Errorf("pkcs7: unsupported digest %q for encryption algorithm %q",
+				digest.Algorithm.String(), digestEncryption.Algorithm.String())
+		}
+	case digestEncryption.Algorithm.Equal(OIDDigestAlgorithmDSA),
+		digestEncryption.Algorithm.Equal(OIDDigestAlgorithmDSASHA1):
+		switch {
+		case digest.Algorithm.Equal(OIDDigestAlgorithmSHA1):
+			return x509.DSAWithSHA1, nil
+		case digest.Algorithm.Equal(OIDDigestAlgorithmSHA256):
+			return x509.DSAWithSHA256, nil
+		default:
+			return -1, fmt.Errorf("pkcs7: unsupported digest %q for encryption algorithm %q",
+				digest.Algorithm.String(), digestEncryption.Algorithm.String())
+		}
+	case digestEncryption.Algorithm.Equal(OIDEncryptionAlgorithmECDSAP256),
+		digestEncryption.Algorithm.Equal(OIDEncryptionAlgorithmECDSAP384),
+		digestEncryption.Algorithm.Equal(OIDEncryptionAlgorithmECDSAP521):
+		switch {
+		case digest.Algorithm.Equal(OIDDigestAlgorithmSHA1):
+			return x509.ECDSAWithSHA1, nil
+		case digest.Algorithm.Equal(OIDDigestAlgorithmSHA256):
+			return x509.ECDSAWithSHA256, nil
+		case digest.Algorithm.Equal(OIDDigestAlgorithmSHA384):
+			return x509.ECDSAWithSHA384, nil
+		case digest.Algorithm.Equal(OIDDigestAlgorithmSHA512):
+			return x509.ECDSAWithSHA512, nil
+		default:
+			return -1, fmt.Errorf("pkcs7: unsupported digest %q for encryption algorithm %q",
+				digest.Algorithm.String(), digestEncryption.Algorithm.String())
+		}
+	default:
+		return -1, fmt.Errorf("pkcs7: unsupported algorithm %q",
+			digestEncryption.Algorithm.String())
+	}
+}
+
+func getCertFromCertsByIssuerAndSerial(certs []*x509.Certificate, ias issuerAndSerial) *x509.Certificate {
+	for _, cert := range certs {
+		if isCertMatchForIssuerAndSerial(cert, ias) {
+			return cert
+		}
+	}
+	return nil
+}
+
+func unmarshalAttribute(attrs []attribute, attributeType asn1.ObjectIdentifier, out interface{}) error {
+	for _, attr := range attrs {
+		if attr.Type.Equal(attributeType) {
+			_, err := asn1.Unmarshal(attr.Value.Bytes, out)
+			return err
+		}
+	}
+	return errors.New("pkcs7: attribute type not in attributes")
+}

builtin/credential/aws/pkcs7/verify_test_dsa.go

@@ -0,0 +1,182 @@
+// +build go1.11 go1.12 go1.13 go1.14 go1.15
+
+package pkcs7
+
+import (
+	"crypto/x509"
+	"encoding/pem"
+	"fmt"
+	"io/ioutil"
+	"os"
+	"os/exec"
+	"testing"
+)
+
+func TestVerifyEC2(t *testing.T) {
+	fixture := UnmarshalDSATestFixture(EC2IdentityDocumentFixture)
+	p7, err := Parse(fixture.Input)
+	if err != nil {
+		t.Errorf("Parse encountered unexpected error: %v", err)
+	}
+	p7.Certificates = []*x509.Certificate{fixture.Certificate}
+	if err := p7.Verify(); err != nil {
+		t.Errorf("Verify failed with error: %v", err)
+	}
+}
+
+var EC2IdentityDocumentFixture = `
+-----BEGIN PKCS7-----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+-----END PKCS7-----
+-----BEGIN CERTIFICATE-----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+-----END CERTIFICATE-----`
+
+func TestDSASignWithOpenSSLAndVerify(t *testing.T) {
+	content := []byte(`
+A ship in port is safe,
+but that's not what ships are built for.
+-- Grace Hopper`)
+	// write the content to a temp file
+	tmpContentFile, err := ioutil.TempFile("", "TestDSASignWithOpenSSLAndVerify_content")
+	if err != nil {
+		t.Fatal(err)
+	}
+	ioutil.WriteFile(tmpContentFile.Name(), content, 0755)
+
+	// write the signer cert to a temp file
+	tmpSignerCertFile, err := ioutil.TempFile("", "TestDSASignWithOpenSSLAndVerify_signer")
+	if err != nil {
+		t.Fatal(err)
+	}
+	ioutil.WriteFile(tmpSignerCertFile.Name(), dsaPublicCert, 0755)
+
+	// write the signer key to a temp file
+	tmpSignerKeyFile, err := ioutil.TempFile("", "TestDSASignWithOpenSSLAndVerify_key")
+	if err != nil {
+		t.Fatal(err)
+	}
+	ioutil.WriteFile(tmpSignerKeyFile.Name(), dsaPrivateKey, 0755)
+
+	tmpSignedFile, err := ioutil.TempFile("", "TestDSASignWithOpenSSLAndVerify_signature")
+	if err != nil {
+		t.Fatal(err)
+	}
+	// call openssl to sign the content
+	opensslCMD := exec.Command("openssl", "smime", "-sign", "-nodetach", "-md", "sha1",
+		"-in", tmpContentFile.Name(), "-out", tmpSignedFile.Name(),
+		"-signer", tmpSignerCertFile.Name(), "-inkey", tmpSignerKeyFile.Name(),
+		"-certfile", tmpSignerCertFile.Name(), "-outform", "PEM")
+	out, err := opensslCMD.CombinedOutput()
+	if err != nil {
+		t.Fatalf("openssl command failed with %s: %s", err, out)
+	}
+
+	// verify the signed content
+	pemSignature, err := ioutil.ReadFile(tmpSignedFile.Name())
+	if err != nil {
+		t.Fatal(err)
+	}
+	fmt.Printf("%s\n", pemSignature)
+	derBlock, _ := pem.Decode(pemSignature)
+	if derBlock == nil {
+		t.Fatalf("failed to read DER block from signature PEM %s", tmpSignedFile.Name())
+	}
+	p7, err := Parse(derBlock.Bytes)
+	if err != nil {
+		t.Fatalf("Parse encountered unexpected error: %v", err)
+	}
+	if err := p7.Verify(); err != nil {
+		t.Fatalf("Verify failed with error: %v", err)
+	}
+	os.Remove(tmpSignerCertFile.Name()) // clean up
+	os.Remove(tmpSignerKeyFile.Name())  // clean up
+	os.Remove(tmpContentFile.Name())    // clean up
+}
+
+var dsaPrivateKey = []byte(`-----BEGIN PRIVATE KEY-----
+MIIBSwIBADCCASwGByqGSM44BAEwggEfAoGBAP1/U4EddRIpUt9KnC7s5Of2EbdS
+PO9EAMMeP4C2USZpRV1AIlH7WT2NWPq/xfW6MPbLm1Vs14E7gB00b/JmYLdrmVCl
+pJ+f6AR7ECLCT7up1/63xhv4O1fnxqimFQ8E+4P208UewwI1VBNaFpEy9nXzrith
+1yrv8iIDGZ3RSAHHAhUAl2BQjxUjC8yykrmCouuEC/BYHPUCgYEA9+GghdabPd7L
+vKtcNrhXuXmUr7v6OuqC+VdMCz0HgmdRWVeOutRZT+ZxBxCBgLRJFnEj6EwoFhO3
+zwkyjMim4TwWeotUfI0o4KOuHiuzpnWRbqN/C/ohNWLx+2J6ASQ7zKTxvqhRkImo
+g9/hWuWfBpKLZl6Ae1UlZAFMO/7PSSoEFgIUfW4aPdQBn9gJZp2KuNpzgHzvfsE=
+-----END PRIVATE KEY-----`)
+
+var dsaPublicCert = []byte(`-----BEGIN CERTIFICATE-----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+-----END CERTIFICATE-----`)
+
+type DSATestFixture struct {
+	Input       []byte
+	Certificate *x509.Certificate
+}
+
+func UnmarshalDSATestFixture(testPEMBlock string) DSATestFixture {
+	var result DSATestFixture
+	var derBlock *pem.Block
+	var pemBlock = []byte(testPEMBlock)
+	for {
+		derBlock, pemBlock = pem.Decode(pemBlock)
+		if derBlock == nil {
+			break
+		}
+		switch derBlock.Type {
+		case "PKCS7":
+			result.Input = derBlock.Bytes
+		case "CERTIFICATE":
+			result.Certificate, _ = x509.ParseCertificate(derBlock.Bytes)
+		}
+	}
+
+	return result
+}

changelog/12340.txt

@@ -0,0 +1,3 @@
+```release-note: bug
+auth/aws: Fixes ec2 login no longer supporting DSA signature verification
+```

go.mod

@@ -44,7 +44,6 @@ require (
 	github.com/dustin/go-humanize v1.0.0
 	github.com/fatih/color v1.11.0
 	github.com/fatih/structs v1.1.0
-	github.com/fullsailor/pkcs7 v0.0.0-20190404230743-d7302db945fa
 	github.com/ghodss/yaml v1.0.1-0.20190212211648-25d852aebe32
 	github.com/go-errors/errors v1.0.1
 	github.com/go-ldap/ldap/v3 v3.2.4

go.sum

@@ -352,8 +352,6 @@ github.com/frankban/quicktest v1.10.0/go.mod h1:ui7WezCLWMWxVWr1GETZY3smRy0G4KWq
 github.com/frankban/quicktest v1.13.0 h1:yNZif1OkDfNoDfb9zZa9aXIpejNR4F23Wely0c+Qdqk=
 github.com/frankban/quicktest v1.13.0/go.mod h1:qLE0fzW0VuyUAJgPU19zByoIr0HtCHN/r/VLSOOIySU=
 github.com/fsnotify/fsnotify v1.4.7/go.mod h1:jwhsz4b93w/PPRr/qN1Yymfu8t87LnFCMoQvtojpjFo=
-github.com/fullsailor/pkcs7 v0.0.0-20190404230743-d7302db945fa h1:RDBNVkRviHZtvDvId8XSGPu3rmpmSe+wKRcEWNgsfWU=
-github.com/fullsailor/pkcs7 v0.0.0-20190404230743-d7302db945fa/go.mod h1:KnogPXtdwXqoenmZCw6S+25EAm2MkxbG0deNDu4cbSA=
 github.com/gammazero/deque v0.0.0-20190130191400-2afb3858e9c7 h1:D2LrfOPgGHQprIxmsTpxtzhpmF66HoM6rXSmcqaX7h8=
 github.com/gammazero/deque v0.0.0-20190130191400-2afb3858e9c7/go.mod h1:GeIq9qoE43YdGnDXURnmKTnGg15pQz4mYkXSTChbneI=
 github.com/gammazero/workerpool v0.0.0-20190406235159-88d534f22b56 h1:VzbudKn/nvxYKOdzgkEBS6SSreRjAgoJ+ZeS4wPFkgc=