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/*-
* Copyright 2014 Square Inc.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package jose
import (
"crypto"
"crypto/aes"
"crypto/ecdsa"
"crypto/rand"
"crypto/rsa"
"crypto/sha1"
"crypto/sha256"
"errors"
"fmt"
"math/big"
"gopkg.in/square/go-jose.v1/cipher"
)
// A generic RSA-based encrypter/verifier
type rsaEncrypterVerifier struct {
publicKey *rsa.PublicKey
}
// A generic RSA-based decrypter/signer
type rsaDecrypterSigner struct {
privateKey *rsa.PrivateKey
}
// A generic EC-based encrypter/verifier
type ecEncrypterVerifier struct {
publicKey *ecdsa.PublicKey
}
// A key generator for ECDH-ES
type ecKeyGenerator struct {
size int
algID string
publicKey *ecdsa.PublicKey
}
// A generic EC-based decrypter/signer
type ecDecrypterSigner struct {
privateKey *ecdsa.PrivateKey
}
// newRSARecipient creates recipientKeyInfo based on the given key.
func newRSARecipient(keyAlg KeyAlgorithm, publicKey *rsa.PublicKey) (recipientKeyInfo, error) {
// Verify that key management algorithm is supported by this encrypter
switch keyAlg {
case RSA1_5, RSA_OAEP, RSA_OAEP_256:
default:
return recipientKeyInfo{}, ErrUnsupportedAlgorithm
}
if publicKey == nil {
return recipientKeyInfo{}, errors.New("invalid public key")
}
return recipientKeyInfo{
keyAlg: keyAlg,
keyEncrypter: &rsaEncrypterVerifier{
publicKey: publicKey,
},
}, nil
}
// newRSASigner creates a recipientSigInfo based on the given key.
func newRSASigner(sigAlg SignatureAlgorithm, privateKey *rsa.PrivateKey) (recipientSigInfo, error) {
// Verify that key management algorithm is supported by this encrypter
switch sigAlg {
case RS256, RS384, RS512, PS256, PS384, PS512:
default:
return recipientSigInfo{}, ErrUnsupportedAlgorithm
}
if privateKey == nil {
return recipientSigInfo{}, errors.New("invalid private key")
}
return recipientSigInfo{
sigAlg: sigAlg,
publicKey: &JsonWebKey{
Key: &privateKey.PublicKey,
},
signer: &rsaDecrypterSigner{
privateKey: privateKey,
},
}, nil
}
// newECDHRecipient creates recipientKeyInfo based on the given key.
func newECDHRecipient(keyAlg KeyAlgorithm, publicKey *ecdsa.PublicKey) (recipientKeyInfo, error) {
// Verify that key management algorithm is supported by this encrypter
switch keyAlg {
case ECDH_ES, ECDH_ES_A128KW, ECDH_ES_A192KW, ECDH_ES_A256KW:
default:
return recipientKeyInfo{}, ErrUnsupportedAlgorithm
}
if publicKey == nil || !publicKey.Curve.IsOnCurve(publicKey.X, publicKey.Y) {
return recipientKeyInfo{}, errors.New("invalid public key")
}
return recipientKeyInfo{
keyAlg: keyAlg,
keyEncrypter: &ecEncrypterVerifier{
publicKey: publicKey,
},
}, nil
}
// newECDSASigner creates a recipientSigInfo based on the given key.
func newECDSASigner(sigAlg SignatureAlgorithm, privateKey *ecdsa.PrivateKey) (recipientSigInfo, error) {
// Verify that key management algorithm is supported by this encrypter
switch sigAlg {
case ES256, ES384, ES512:
default:
return recipientSigInfo{}, ErrUnsupportedAlgorithm
}
if privateKey == nil {
return recipientSigInfo{}, errors.New("invalid private key")
}
return recipientSigInfo{
sigAlg: sigAlg,
publicKey: &JsonWebKey{
Key: &privateKey.PublicKey,
},
signer: &ecDecrypterSigner{
privateKey: privateKey,
},
}, nil
}
// Encrypt the given payload and update the object.
func (ctx rsaEncrypterVerifier) encryptKey(cek []byte, alg KeyAlgorithm) (recipientInfo, error) {
encryptedKey, err := ctx.encrypt(cek, alg)
if err != nil {
return recipientInfo{}, err
}
return recipientInfo{
encryptedKey: encryptedKey,
header: &rawHeader{},
}, nil
}
// Encrypt the given payload. Based on the key encryption algorithm,
// this will either use RSA-PKCS1v1.5 or RSA-OAEP (with SHA-1 or SHA-256).
func (ctx rsaEncrypterVerifier) encrypt(cek []byte, alg KeyAlgorithm) ([]byte, error) {
switch alg {
case RSA1_5:
return rsa.EncryptPKCS1v15(randReader, ctx.publicKey, cek)
case RSA_OAEP:
return rsa.EncryptOAEP(sha1.New(), randReader, ctx.publicKey, cek, []byte{})
case RSA_OAEP_256:
return rsa.EncryptOAEP(sha256.New(), randReader, ctx.publicKey, cek, []byte{})
}
return nil, ErrUnsupportedAlgorithm
}
// Decrypt the given payload and return the content encryption key.
func (ctx rsaDecrypterSigner) decryptKey(headers rawHeader, recipient *recipientInfo, generator keyGenerator) ([]byte, error) {
return ctx.decrypt(recipient.encryptedKey, KeyAlgorithm(headers.Alg), generator)
}
// Decrypt the given payload. Based on the key encryption algorithm,
// this will either use RSA-PKCS1v1.5 or RSA-OAEP (with SHA-1 or SHA-256).
func (ctx rsaDecrypterSigner) decrypt(jek []byte, alg KeyAlgorithm, generator keyGenerator) ([]byte, error) {
// Note: The random reader on decrypt operations is only used for blinding,
// so stubbing is meanlingless (hence the direct use of rand.Reader).
switch alg {
case RSA1_5:
defer func() {
// DecryptPKCS1v15SessionKey sometimes panics on an invalid payload
// because of an index out of bounds error, which we want to ignore.
// This has been fixed in Go 1.3.1 (released 2014/08/13), the recover()
// only exists for preventing crashes with unpatched versions.
// See: https://groups.google.com/forum/#!topic/golang-dev/7ihX6Y6kx9k
// See: https://code.google.com/p/go/source/detail?r=58ee390ff31602edb66af41ed10901ec95904d33
_ = recover()
}()
// Perform some input validation.
keyBytes := ctx.privateKey.PublicKey.N.BitLen() / 8
if keyBytes != len(jek) {
// Input size is incorrect, the encrypted payload should always match
// the size of the public modulus (e.g. using a 2048 bit key will
// produce 256 bytes of output). Reject this since it's invalid input.
return nil, ErrCryptoFailure
}
cek, _, err := generator.genKey()
if err != nil {
return nil, ErrCryptoFailure
}
// When decrypting an RSA-PKCS1v1.5 payload, we must take precautions to
// prevent chosen-ciphertext attacks as described in RFC 3218, "Preventing
// the Million Message Attack on Cryptographic Message Syntax". We are
// therefore deliberately ignoring errors here.
_ = rsa.DecryptPKCS1v15SessionKey(rand.Reader, ctx.privateKey, jek, cek)
return cek, nil
case RSA_OAEP:
// Use rand.Reader for RSA blinding
return rsa.DecryptOAEP(sha1.New(), rand.Reader, ctx.privateKey, jek, []byte{})
case RSA_OAEP_256:
// Use rand.Reader for RSA blinding
return rsa.DecryptOAEP(sha256.New(), rand.Reader, ctx.privateKey, jek, []byte{})
}
return nil, ErrUnsupportedAlgorithm
}
// Sign the given payload
func (ctx rsaDecrypterSigner) signPayload(payload []byte, alg SignatureAlgorithm) (Signature, error) {
var hash crypto.Hash
switch alg {
case RS256, PS256:
hash = crypto.SHA256
case RS384, PS384:
hash = crypto.SHA384
case RS512, PS512:
hash = crypto.SHA512
default:
return Signature{}, ErrUnsupportedAlgorithm
}
hasher := hash.New()
// According to documentation, Write() on hash never fails
_, _ = hasher.Write(payload)
hashed := hasher.Sum(nil)
var out []byte
var err error
switch alg {
case RS256, RS384, RS512:
out, err = rsa.SignPKCS1v15(randReader, ctx.privateKey, hash, hashed)
case PS256, PS384, PS512:
out, err = rsa.SignPSS(randReader, ctx.privateKey, hash, hashed, &rsa.PSSOptions{
SaltLength: rsa.PSSSaltLengthAuto,
})
}
if err != nil {
return Signature{}, err
}
return Signature{
Signature: out,
protected: &rawHeader{},
}, nil
}
// Verify the given payload
func (ctx rsaEncrypterVerifier) verifyPayload(payload []byte, signature []byte, alg SignatureAlgorithm) error {
var hash crypto.Hash
switch alg {
case RS256, PS256:
hash = crypto.SHA256
case RS384, PS384:
hash = crypto.SHA384
case RS512, PS512:
hash = crypto.SHA512
default:
return ErrUnsupportedAlgorithm
}
hasher := hash.New()
// According to documentation, Write() on hash never fails
_, _ = hasher.Write(payload)
hashed := hasher.Sum(nil)
switch alg {
case RS256, RS384, RS512:
return rsa.VerifyPKCS1v15(ctx.publicKey, hash, hashed, signature)
case PS256, PS384, PS512:
return rsa.VerifyPSS(ctx.publicKey, hash, hashed, signature, nil)
}
return ErrUnsupportedAlgorithm
}
// Encrypt the given payload and update the object.
func (ctx ecEncrypterVerifier) encryptKey(cek []byte, alg KeyAlgorithm) (recipientInfo, error) {
switch alg {
case ECDH_ES:
// ECDH-ES mode doesn't wrap a key, the shared secret is used directly as the key.
return recipientInfo{
header: &rawHeader{},
}, nil
case ECDH_ES_A128KW, ECDH_ES_A192KW, ECDH_ES_A256KW:
default:
return recipientInfo{}, ErrUnsupportedAlgorithm
}
generator := ecKeyGenerator{
algID: string(alg),
publicKey: ctx.publicKey,
}
switch alg {
case ECDH_ES_A128KW:
generator.size = 16
case ECDH_ES_A192KW:
generator.size = 24
case ECDH_ES_A256KW:
generator.size = 32
}
kek, header, err := generator.genKey()
if err != nil {
return recipientInfo{}, err
}
block, err := aes.NewCipher(kek)
if err != nil {
return recipientInfo{}, err
}
jek, err := josecipher.KeyWrap(block, cek)
if err != nil {
return recipientInfo{}, err
}
return recipientInfo{
encryptedKey: jek,
header: &header,
}, nil
}
// Get key size for EC key generator
func (ctx ecKeyGenerator) keySize() int {
return ctx.size
}
// Get a content encryption key for ECDH-ES
func (ctx ecKeyGenerator) genKey() ([]byte, rawHeader, error) {
priv, err := ecdsa.GenerateKey(ctx.publicKey.Curve, randReader)
if err != nil {
return nil, rawHeader{}, err
}
out := josecipher.DeriveECDHES(ctx.algID, []byte{}, []byte{}, priv, ctx.publicKey, ctx.size)
headers := rawHeader{
Epk: &JsonWebKey{
Key: &priv.PublicKey,
},
}
return out, headers, nil
}
// Decrypt the given payload and return the content encryption key.
func (ctx ecDecrypterSigner) decryptKey(headers rawHeader, recipient *recipientInfo, generator keyGenerator) ([]byte, error) {
if headers.Epk == nil {
return nil, errors.New("square/go-jose: missing epk header")
}
publicKey, ok := headers.Epk.Key.(*ecdsa.PublicKey)
if publicKey == nil || !ok {
return nil, errors.New("square/go-jose: invalid epk header")
}
if !ctx.privateKey.Curve.IsOnCurve(publicKey.X, publicKey.Y) {
return nil, errors.New("square/go-jose: invalid public key in epk header")
}
apuData := headers.Apu.bytes()
apvData := headers.Apv.bytes()
deriveKey := func(algID string, size int) []byte {
return josecipher.DeriveECDHES(algID, apuData, apvData, ctx.privateKey, publicKey, size)
}
var keySize int
switch KeyAlgorithm(headers.Alg) {
case ECDH_ES:
// ECDH-ES uses direct key agreement, no key unwrapping necessary.
return deriveKey(string(headers.Enc), generator.keySize()), nil
case ECDH_ES_A128KW:
keySize = 16
case ECDH_ES_A192KW:
keySize = 24
case ECDH_ES_A256KW:
keySize = 32
default:
return nil, ErrUnsupportedAlgorithm
}
key := deriveKey(headers.Alg, keySize)
block, err := aes.NewCipher(key)
if err != nil {
return nil, err
}
return josecipher.KeyUnwrap(block, recipient.encryptedKey)
}
// Sign the given payload
func (ctx ecDecrypterSigner) signPayload(payload []byte, alg SignatureAlgorithm) (Signature, error) {
var expectedBitSize int
var hash crypto.Hash
switch alg {
case ES256:
expectedBitSize = 256
hash = crypto.SHA256
case ES384:
expectedBitSize = 384
hash = crypto.SHA384
case ES512:
expectedBitSize = 521
hash = crypto.SHA512
}
curveBits := ctx.privateKey.Curve.Params().BitSize
if expectedBitSize != curveBits {
return Signature{}, fmt.Errorf("square/go-jose: expected %d bit key, got %d bits instead", expectedBitSize, curveBits)
}
hasher := hash.New()
// According to documentation, Write() on hash never fails
_, _ = hasher.Write(payload)
hashed := hasher.Sum(nil)
r, s, err := ecdsa.Sign(randReader, ctx.privateKey, hashed)
if err != nil {
return Signature{}, err
}
keyBytes := curveBits / 8
if curveBits%8 > 0 {
keyBytes += 1
}
// We serialize the outpus (r and s) into big-endian byte arrays and pad
// them with zeros on the left to make sure the sizes work out. Both arrays
// must be keyBytes long, and the output must be 2*keyBytes long.
rBytes := r.Bytes()
rBytesPadded := make([]byte, keyBytes)
copy(rBytesPadded[keyBytes-len(rBytes):], rBytes)
sBytes := s.Bytes()
sBytesPadded := make([]byte, keyBytes)
copy(sBytesPadded[keyBytes-len(sBytes):], sBytes)
out := append(rBytesPadded, sBytesPadded...)
return Signature{
Signature: out,
protected: &rawHeader{},
}, nil
}
// Verify the given payload
func (ctx ecEncrypterVerifier) verifyPayload(payload []byte, signature []byte, alg SignatureAlgorithm) error {
var keySize int
var hash crypto.Hash
switch alg {
case ES256:
keySize = 32
hash = crypto.SHA256
case ES384:
keySize = 48
hash = crypto.SHA384
case ES512:
keySize = 66
hash = crypto.SHA512
default:
return ErrUnsupportedAlgorithm
}
if len(signature) != 2*keySize {
return fmt.Errorf("square/go-jose: invalid signature size, have %d bytes, wanted %d", len(signature), 2*keySize)
}
hasher := hash.New()
// According to documentation, Write() on hash never fails
_, _ = hasher.Write(payload)
hashed := hasher.Sum(nil)
r := big.NewInt(0).SetBytes(signature[:keySize])
s := big.NewInt(0).SetBytes(signature[keySize:])
match := ecdsa.Verify(ctx.publicKey, hashed, r, s)
if !match {
return errors.New("square/go-jose: ecdsa signature failed to verify")
}
return nil
}
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