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HMS-2695 feat: JWK encryption with AES-GCM
Implement helpers to encrypt and decrypt a JWK with AES-GCM AEAD. `EncryptJWK()` takes a raw AES encryption key plus `jwk.Key` and returns the encrypted key. The key is encrypted and protected with AES-GCM. The random nonce is pre-pended to the output stream. `DecryptJWK()` is the reverse operation. It takes a raw AES key and cipher text with nonce pre-pended. On success, it returns a `jwk.Key`. Invalid key and tampering are detected by AEAD. Also pulls the latest `lestrrat-go/jwx@v2` go module. Signed-off-by: Christian Heimes <[email protected]>
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,67 @@ | ||
| package token | ||
|
|
||
| import ( | ||
| "crypto/aes" | ||
| "crypto/cipher" | ||
| "crypto/rand" | ||
| "encoding/json" | ||
| "errors" | ||
| "io" | ||
|
|
||
| "github.com/lestrrat-go/jwx/v2/jwk" | ||
| ) | ||
|
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| // Encrypt a JWK Key with encryption key | ||
| // Uses AES-GCM with a random nonce. The nonce is pre-pended to ciphertext. | ||
| func EncryptJWK(aeskey []byte, jwkey jwk.Key) (enc []byte, err error) { | ||
| // create AES-GCM AEAD and nonce | ||
| block, err := aes.NewCipher(aeskey) | ||
| if err != nil { | ||
| return nil, err | ||
| } | ||
| aesgcm, err := cipher.NewGCM(block) | ||
| if err != nil { | ||
| return nil, err | ||
| } | ||
| nonce := make([]byte, aesgcm.NonceSize()) | ||
| if _, err := io.ReadFull(rand.Reader, nonce); err != nil { | ||
| return nil, err | ||
| } | ||
|
|
||
| // serialize JWK to JSON bytes | ||
| jwkbuf, err := json.Marshal(jwkey) | ||
| if err != nil { | ||
| return nil, err | ||
| } | ||
|
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||
| // encrypt and seal | ||
| ciphertext := aesgcm.Seal(nil, nonce, jwkbuf, nil) | ||
| // combine nonce, ciphertext + tag | ||
| return append(nonce, ciphertext...), nil | ||
| } | ||
|
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||
| // Decrypt an AES-GCM encrypted JWK | ||
| func DecryptJWK(aeskey []byte, encrypted []byte) (jwkey jwk.Key, err error) { | ||
| // create AES-GCM AEAD and get nonce | ||
| block, err := aes.NewCipher(aeskey) | ||
| if err != nil { | ||
| return nil, err | ||
| } | ||
| aesgcm, err := cipher.NewGCM(block) | ||
| if err != nil { | ||
| return nil, err | ||
| } | ||
| if len(encrypted) < (aesgcm.NonceSize() + aesgcm.Overhead()) { | ||
| return nil, errors.New("encrypted blob is too short") | ||
| } | ||
| nonce := encrypted[:aesgcm.NonceSize()] | ||
| ciphertext := encrypted[aesgcm.NonceSize():] | ||
|
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||
| // unseal and decrypt | ||
| plaintext, err := aesgcm.Open(nil, nonce, ciphertext, nil) | ||
| if err != nil { | ||
| return nil, err | ||
| } | ||
|
|
||
| return jwk.ParseKey(plaintext) | ||
| } |
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,34 @@ | ||
| package token | ||
|
|
||
| import ( | ||
| "crypto/ecdsa" | ||
| "crypto/elliptic" | ||
| "crypto/rand" | ||
| "testing" | ||
|
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| "github.com/lestrrat-go/jwx/v2/jwk" | ||
| "github.com/stretchr/testify/assert" | ||
| ) | ||
|
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| func TestJWKEncryption(t *testing.T) { | ||
| raw, err := ecdsa.GenerateKey(elliptic.P256(), rand.Reader) | ||
| assert.NoError(t, err) | ||
| jwkey, err := jwk.FromRaw(raw) | ||
| assert.NoError(t, err) | ||
|
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| aeskey1 := make([]byte, 16) | ||
| _, err = rand.Reader.Read(aeskey1) | ||
| assert.NoError(t, err) | ||
|
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| encrypted, err := EncryptJWK(aeskey1, jwkey) | ||
| assert.NoError(t, err) | ||
|
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| decrypted, err := DecryptJWK(aeskey1, encrypted) | ||
| assert.NoError(t, err) | ||
| assert.Equal(t, decrypted, jwkey) | ||
|
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| aeskey2 := make([]byte, 16) | ||
| decrypted, err = DecryptJWK(aeskey2, encrypted) | ||
| assert.Nil(t, decrypted) | ||
| assert.EqualError(t, err, "cipher: message authentication failed") | ||
| } |