e6fb16be9c
And add a semgrep for fmt.Printf/Println.
177 lines
5 KiB
Go
177 lines
5 KiB
Go
package pkcs7
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import (
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"bytes"
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"crypto"
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"crypto/aes"
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"crypto/cipher"
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"crypto/des"
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"crypto/rand"
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"crypto/rsa"
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"crypto/x509"
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"encoding/asn1"
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"errors"
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"fmt"
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)
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// ErrUnsupportedAlgorithm tells you when our quick dev assumptions have failed
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var ErrUnsupportedAlgorithm = errors.New("pkcs7: cannot decrypt data: only RSA, DES, DES-EDE3, AES-256-CBC and AES-128-GCM supported")
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// ErrNotEncryptedContent is returned when attempting to Decrypt data that is not encrypted data
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var ErrNotEncryptedContent = errors.New("pkcs7: content data is a decryptable data type")
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// Decrypt decrypts encrypted content info for recipient cert and private key
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func (p7 *PKCS7) Decrypt(cert *x509.Certificate, pkey crypto.PrivateKey) ([]byte, error) {
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data, ok := p7.raw.(envelopedData)
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if !ok {
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return nil, ErrNotEncryptedContent
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}
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recipient := selectRecipientForCertificate(data.RecipientInfos, cert)
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if recipient.EncryptedKey == nil {
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return nil, errors.New("pkcs7: no enveloped recipient for provided certificate")
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}
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switch pkey := pkey.(type) {
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case *rsa.PrivateKey:
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var contentKey []byte
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contentKey, err := rsa.DecryptPKCS1v15(rand.Reader, pkey, recipient.EncryptedKey)
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if err != nil {
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return nil, err
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}
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return data.EncryptedContentInfo.decrypt(contentKey)
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}
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return nil, ErrUnsupportedAlgorithm
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}
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// DecryptUsingPSK decrypts encrypted data using caller provided
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// pre-shared secret
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func (p7 *PKCS7) DecryptUsingPSK(key []byte) ([]byte, error) {
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data, ok := p7.raw.(encryptedData)
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if !ok {
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return nil, ErrNotEncryptedContent
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}
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return data.EncryptedContentInfo.decrypt(key)
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}
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func (eci encryptedContentInfo) decrypt(key []byte) ([]byte, error) {
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alg := eci.ContentEncryptionAlgorithm.Algorithm
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if !alg.Equal(OIDEncryptionAlgorithmDESCBC) &&
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!alg.Equal(OIDEncryptionAlgorithmDESEDE3CBC) &&
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!alg.Equal(OIDEncryptionAlgorithmAES256CBC) &&
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!alg.Equal(OIDEncryptionAlgorithmAES128CBC) &&
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!alg.Equal(OIDEncryptionAlgorithmAES128GCM) &&
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!alg.Equal(OIDEncryptionAlgorithmAES256GCM) {
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return nil, ErrUnsupportedAlgorithm
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}
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// EncryptedContent can either be constructed of multple OCTET STRINGs
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// or _be_ a tagged OCTET STRING
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var cyphertext []byte
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if eci.EncryptedContent.IsCompound {
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// Complex case to concat all of the children OCTET STRINGs
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var buf bytes.Buffer
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cypherbytes := eci.EncryptedContent.Bytes
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for {
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var part []byte
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cypherbytes, _ = asn1.Unmarshal(cypherbytes, &part)
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buf.Write(part)
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if cypherbytes == nil {
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break
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}
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}
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cyphertext = buf.Bytes()
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} else {
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// Simple case, the bytes _are_ the cyphertext
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cyphertext = eci.EncryptedContent.Bytes
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}
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var block cipher.Block
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var err error
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switch {
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case alg.Equal(OIDEncryptionAlgorithmDESCBC):
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block, err = des.NewCipher(key)
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case alg.Equal(OIDEncryptionAlgorithmDESEDE3CBC):
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block, err = des.NewTripleDESCipher(key)
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case alg.Equal(OIDEncryptionAlgorithmAES256CBC), alg.Equal(OIDEncryptionAlgorithmAES256GCM):
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fallthrough
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case alg.Equal(OIDEncryptionAlgorithmAES128GCM), alg.Equal(OIDEncryptionAlgorithmAES128CBC):
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block, err = aes.NewCipher(key)
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}
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if err != nil {
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return nil, err
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}
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if alg.Equal(OIDEncryptionAlgorithmAES128GCM) || alg.Equal(OIDEncryptionAlgorithmAES256GCM) {
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params := aesGCMParameters{}
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paramBytes := eci.ContentEncryptionAlgorithm.Parameters.Bytes
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_, err := asn1.Unmarshal(paramBytes, ¶ms)
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if err != nil {
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return nil, err
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}
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gcm, err := cipher.NewGCM(block)
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if err != nil {
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return nil, err
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}
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if len(params.Nonce) != gcm.NonceSize() {
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return nil, errors.New("pkcs7: encryption algorithm parameters are incorrect")
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}
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if params.ICVLen != gcm.Overhead() {
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return nil, errors.New("pkcs7: encryption algorithm parameters are incorrect")
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}
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plaintext, err := gcm.Open(nil, params.Nonce, cyphertext, nil)
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if err != nil {
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return nil, err
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}
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return plaintext, nil
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}
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iv := eci.ContentEncryptionAlgorithm.Parameters.Bytes
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if len(iv) != block.BlockSize() {
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return nil, errors.New("pkcs7: encryption algorithm parameters are malformed")
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}
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mode := cipher.NewCBCDecrypter(block, iv)
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plaintext := make([]byte, len(cyphertext))
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mode.CryptBlocks(plaintext, cyphertext)
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if plaintext, err = unpad(plaintext, mode.BlockSize()); err != nil {
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return nil, err
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}
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return plaintext, nil
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}
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func unpad(data []byte, blocklen int) ([]byte, error) {
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if blocklen < 1 {
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return nil, fmt.Errorf("invalid blocklen %d", blocklen)
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}
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if len(data)%blocklen != 0 || len(data) == 0 {
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return nil, fmt.Errorf("invalid data len %d", len(data))
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}
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// the last byte is the length of padding
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padlen := int(data[len(data)-1])
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// check padding integrity, all bytes should be the same
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pad := data[len(data)-padlen:]
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for _, padbyte := range pad {
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if padbyte != byte(padlen) {
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return nil, errors.New("invalid padding")
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}
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}
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return data[:len(data)-padlen], nil
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}
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func selectRecipientForCertificate(recipients []recipientInfo, cert *x509.Certificate) recipientInfo {
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for _, recp := range recipients {
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if isCertMatchForIssuerAndSerial(cert, recp.IssuerAndSerialNumber) {
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return recp
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}
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}
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return recipientInfo{}
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}
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