open-vault/helper/dhutil/dhutil.go
Hamid Ghaf 27bb03bbc0
adding copyright header (#19555)
* adding copyright header

* fix fmt and a test
2023-03-15 09:00:52 -07:00

165 lines
4.2 KiB
Go

// Copyright (c) HashiCorp, Inc.
// SPDX-License-Identifier: MPL-2.0
package dhutil
import (
"bytes"
"crypto/aes"
"crypto/cipher"
"crypto/rand"
"crypto/sha256"
"errors"
"fmt"
"io"
"golang.org/x/crypto/hkdf"
"golang.org/x/crypto/curve25519"
)
type PublicKeyInfo struct {
Curve25519PublicKey []byte `json:"curve25519_public_key"`
}
type Envelope struct {
Curve25519PublicKey []byte `json:"curve25519_public_key"`
Nonce []byte `json:"nonce"`
EncryptedPayload []byte `json:"encrypted_payload"`
}
// generatePublicPrivateKey uses curve25519 to generate a public and private key
// pair.
func GeneratePublicPrivateKey() ([]byte, []byte, error) {
var scalar, public [32]byte
if _, err := io.ReadFull(rand.Reader, scalar[:]); err != nil {
return nil, nil, err
}
curve25519.ScalarBaseMult(&public, &scalar)
return public[:], scalar[:], nil
}
// GenerateSharedSecret uses the private key and the other party's public key to
// generate the shared secret.
func GenerateSharedSecret(ourPrivate, theirPublic []byte) ([]byte, error) {
if len(ourPrivate) != 32 {
return nil, fmt.Errorf("invalid private key length: %d", len(ourPrivate))
}
if len(theirPublic) != 32 {
return nil, fmt.Errorf("invalid public key length: %d", len(theirPublic))
}
return curve25519.X25519(ourPrivate, theirPublic)
}
// DeriveSharedKey uses HKDF to derive a key from a shared secret and public keys
func DeriveSharedKey(secret, ourPublic, theirPublic []byte) ([]byte, error) {
// Derive the final key from the HKDF of the secret and public keys.
/*
Internally, HKDF hashes the secret and two public keys. If Alice and Bob are doing DH key exchange, Alice calculates:
HKDF(secret, A, B) since ourPublic is A.
Bob calculates HKDF(secret, B, A), since Bob's ours is B. That produces a different value. Now we only care
that both public keys participate in the derivation, so simply sorting them so they are in a consistent
numerical order (either one would do) arrives at an agreed value.
*/
var pub1 []byte
var pub2 []byte
switch bytes.Compare(ourPublic, theirPublic) {
case 0:
return nil, errors.New("same public key supplied for both participants")
case -1:
pub1 = ourPublic
pub2 = theirPublic
case 1:
pub1 = theirPublic
pub2 = ourPublic
}
kio := hkdf.New(sha256.New, secret, pub1, pub2)
var key [32]byte
n, err := io.ReadFull(kio, key[:])
if err != nil {
// Don't return the key along with the error to prevent misuse
return nil, err
}
if n != 32 {
return nil, errors.New("short read from hkdf")
}
return key[:], nil
}
// Use AES256-GCM to encrypt some plaintext with a provided key. The returned values are
// the ciphertext, the nonce, and error respectively.
func EncryptAES(key, plaintext, aad []byte) ([]byte, []byte, error) {
// We enforce AES-256, so check explicitly for 32 bytes on the key
if len(key) != 32 {
return nil, nil, fmt.Errorf("invalid key length: %d", len(key))
}
if len(plaintext) == 0 {
return nil, nil, errors.New("empty plaintext provided")
}
block, err := aes.NewCipher(key)
if err != nil {
return nil, nil, err
}
// Never use more than 2^32 random nonces with a given key because of the risk of a repeat.
nonce := make([]byte, 12)
if _, err := io.ReadFull(rand.Reader, nonce); err != nil {
return nil, nil, err
}
aesgcm, err := cipher.NewGCM(block)
if err != nil {
return nil, nil, err
}
ciphertext := aesgcm.Seal(nil, nonce, plaintext, aad)
return ciphertext, nonce, nil
}
// Use AES256-GCM to decrypt some ciphertext with a provided key and nonce. The
// returned values are the plaintext and error respectively.
func DecryptAES(key, ciphertext, nonce, aad []byte) ([]byte, error) {
// We enforce AES-256, so check explicitly for 32 bytes on the key
if len(key) != 32 {
return nil, fmt.Errorf("invalid key length: %d", len(key))
}
if len(ciphertext) == 0 {
return nil, errors.New("empty ciphertext provided")
}
if len(nonce) == 0 {
return nil, errors.New("empty nonce provided")
}
block, err := aes.NewCipher(key)
if err != nil {
return nil, err
}
aesgcm, err := cipher.NewGCM(block)
if err != nil {
return nil, err
}
plaintext, err := aesgcm.Open(nil, nonce, ciphertext, aad)
if err != nil {
return nil, err
}
return plaintext, nil
}