1 files changed, 349 insertions, 0 deletions
diff --git a/vendor/github.com/rsc/letsencrypt/vendor/gopkg.in/square/go-jose.v1/symmetric.go b/vendor/github.com/rsc/letsencrypt/vendor/gopkg.in/square/go-jose.v1/symmetric.go
new file mode 100644
index 000000000..51f8cb394
--- /dev/null
+++ b/vendor/github.com/rsc/letsencrypt/vendor/gopkg.in/square/go-jose.v1/symmetric.go
@@ -0,0 +1,349 @@
+/*-
+ * 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/aes"
+	"crypto/cipher"
+	"crypto/hmac"
+	"crypto/rand"
+	"crypto/sha256"
+	"crypto/sha512"
+	"crypto/subtle"
+	"errors"
+	"hash"
+	"io"
+
+	"gopkg.in/square/go-jose.v1/cipher"
+)
+
+// Random reader (stubbed out in tests)
+var randReader = rand.Reader
+
+// Dummy key cipher for shared symmetric key mode
+type symmetricKeyCipher struct {
+	key []byte // Pre-shared content-encryption key
+}
+
+// Signer/verifier for MAC modes
+type symmetricMac struct {
+	key []byte
+}
+
+// Input/output from an AEAD operation
+type aeadParts struct {
+	iv, ciphertext, tag []byte
+}
+
+// A content cipher based on an AEAD construction
+type aeadContentCipher struct {
+	keyBytes     int
+	authtagBytes int
+	getAead      func(key []byte) (cipher.AEAD, error)
+}
+
+// Random key generator
+type randomKeyGenerator struct {
+	size int
+}
+
+// Static key generator
+type staticKeyGenerator struct {
+	key []byte
+}
+
+// Create a new content cipher based on AES-GCM
+func newAESGCM(keySize int) contentCipher {
+	return &aeadContentCipher{
+		keyBytes:     keySize,
+		authtagBytes: 16,
+		getAead: func(key []byte) (cipher.AEAD, error) {
+			aes, err := aes.NewCipher(key)
+			if err != nil {
+				return nil, err
+			}
+
+			return cipher.NewGCM(aes)
+		},
+	}
+}
+
+// Create a new content cipher based on AES-CBC+HMAC
+func newAESCBC(keySize int) contentCipher {
+	return &aeadContentCipher{
+		keyBytes:     keySize * 2,
+		authtagBytes: 16,
+		getAead: func(key []byte) (cipher.AEAD, error) {
+			return josecipher.NewCBCHMAC(key, aes.NewCipher)
+		},
+	}
+}
+
+// Get an AEAD cipher object for the given content encryption algorithm
+func getContentCipher(alg ContentEncryption) contentCipher {
+	switch alg {
+	case A128GCM:
+		return newAESGCM(16)
+	case A192GCM:
+		return newAESGCM(24)
+	case A256GCM:
+		return newAESGCM(32)
+	case A128CBC_HS256:
+		return newAESCBC(16)
+	case A192CBC_HS384:
+		return newAESCBC(24)
+	case A256CBC_HS512:
+		return newAESCBC(32)
+	default:
+		return nil
+	}
+}
+
+// newSymmetricRecipient creates a JWE encrypter based on AES-GCM key wrap.
+func newSymmetricRecipient(keyAlg KeyAlgorithm, key []byte) (recipientKeyInfo, error) {
+	switch keyAlg {
+	case DIRECT, A128GCMKW, A192GCMKW, A256GCMKW, A128KW, A192KW, A256KW:
+	default:
+		return recipientKeyInfo{}, ErrUnsupportedAlgorithm
+	}
+
+	return recipientKeyInfo{
+		keyAlg: keyAlg,
+		keyEncrypter: &symmetricKeyCipher{
+			key: key,
+		},
+	}, nil
+}
+
+// newSymmetricSigner creates a recipientSigInfo based on the given key.
+func newSymmetricSigner(sigAlg SignatureAlgorithm, key []byte) (recipientSigInfo, error) {
+	// Verify that key management algorithm is supported by this encrypter
+	switch sigAlg {
+	case HS256, HS384, HS512:
+	default:
+		return recipientSigInfo{}, ErrUnsupportedAlgorithm
+	}
+
+	return recipientSigInfo{
+		sigAlg: sigAlg,
+		signer: &symmetricMac{
+			key: key,
+		},
+	}, nil
+}
+
+// Generate a random key for the given content cipher
+func (ctx randomKeyGenerator) genKey() ([]byte, rawHeader, error) {
+	key := make([]byte, ctx.size)
+	_, err := io.ReadFull(randReader, key)
+	if err != nil {
+		return nil, rawHeader{}, err
+	}
+
+	return key, rawHeader{}, nil
+}
+
+// Key size for random generator
+func (ctx randomKeyGenerator) keySize() int {
+	return ctx.size
+}
+
+// Generate a static key (for direct mode)
+func (ctx staticKeyGenerator) genKey() ([]byte, rawHeader, error) {
+	cek := make([]byte, len(ctx.key))
+	copy(cek, ctx.key)
+	return cek, rawHeader{}, nil
+}
+
+// Key size for static generator
+func (ctx staticKeyGenerator) keySize() int {
+	return len(ctx.key)
+}
+
+// Get key size for this cipher
+func (ctx aeadContentCipher) keySize() int {
+	return ctx.keyBytes
+}
+
+// Encrypt some data
+func (ctx aeadContentCipher) encrypt(key, aad, pt []byte) (*aeadParts, error) {
+	// Get a new AEAD instance
+	aead, err := ctx.getAead(key)
+	if err != nil {
+		return nil, err
+	}
+
+	// Initialize a new nonce
+	iv := make([]byte, aead.NonceSize())
+	_, err = io.ReadFull(randReader, iv)
+	if err != nil {
+		return nil, err
+	}
+
+	ciphertextAndTag := aead.Seal(nil, iv, pt, aad)
+	offset := len(ciphertextAndTag) - ctx.authtagBytes
+
+	return &aeadParts{
+		iv:         iv,
+		ciphertext: ciphertextAndTag[:offset],
+		tag:        ciphertextAndTag[offset:],
+	}, nil
+}
+
+// Decrypt some data
+func (ctx aeadContentCipher) decrypt(key, aad []byte, parts *aeadParts) ([]byte, error) {
+	aead, err := ctx.getAead(key)
+	if err != nil {
+		return nil, err
+	}
+
+	return aead.Open(nil, parts.iv, append(parts.ciphertext, parts.tag...), aad)
+}
+
+// Encrypt the content encryption key.
+func (ctx *symmetricKeyCipher) encryptKey(cek []byte, alg KeyAlgorithm) (recipientInfo, error) {
+	switch alg {
+	case DIRECT:
+		return recipientInfo{
+			header: &rawHeader{},
+		}, nil
+	case A128GCMKW, A192GCMKW, A256GCMKW:
+		aead := newAESGCM(len(ctx.key))
+
+		parts, err := aead.encrypt(ctx.key, []byte{}, cek)
+		if err != nil {
+			return recipientInfo{}, err
+		}
+
+		return recipientInfo{
+			header: &rawHeader{
+				Iv:  newBuffer(parts.iv),
+				Tag: newBuffer(parts.tag),
+			},
+			encryptedKey: parts.ciphertext,
+		}, nil
+	case A128KW, A192KW, A256KW:
+		block, err := aes.NewCipher(ctx.key)
+		if err != nil {
+			return recipientInfo{}, err
+		}
+
+		jek, err := josecipher.KeyWrap(block, cek)
+		if err != nil {
+			return recipientInfo{}, err
+		}
+
+		return recipientInfo{
+			encryptedKey: jek,
+			header:       &rawHeader{},
+		}, nil
+	}
+
+	return recipientInfo{}, ErrUnsupportedAlgorithm
+}
+
+// Decrypt the content encryption key.
+func (ctx *symmetricKeyCipher) decryptKey(headers rawHeader, recipient *recipientInfo, generator keyGenerator) ([]byte, error) {
+	switch KeyAlgorithm(headers.Alg) {
+	case DIRECT:
+		cek := make([]byte, len(ctx.key))
+		copy(cek, ctx.key)
+		return cek, nil
+	case A128GCMKW, A192GCMKW, A256GCMKW:
+		aead := newAESGCM(len(ctx.key))
+
+		parts := &aeadParts{
+			iv:         headers.Iv.bytes(),
+			ciphertext: recipient.encryptedKey,
+			tag:        headers.Tag.bytes(),
+		}
+
+		cek, err := aead.decrypt(ctx.key, []byte{}, parts)
+		if err != nil {
+			return nil, err
+		}
+
+		return cek, nil
+	case A128KW, A192KW, A256KW:
+		block, err := aes.NewCipher(ctx.key)
+		if err != nil {
+			return nil, err
+		}
+
+		cek, err := josecipher.KeyUnwrap(block, recipient.encryptedKey)
+		if err != nil {
+			return nil, err
+		}
+		return cek, nil
+	}
+
+	return nil, ErrUnsupportedAlgorithm
+}
+
+// Sign the given payload
+func (ctx symmetricMac) signPayload(payload []byte, alg SignatureAlgorithm) (Signature, error) {
+	mac, err := ctx.hmac(payload, alg)
+	if err != nil {
+		return Signature{}, errors.New("square/go-jose: failed to compute hmac")
+	}
+
+	return Signature{
+		Signature: mac,
+		protected: &rawHeader{},
+	}, nil
+}
+
+// Verify the given payload
+func (ctx symmetricMac) verifyPayload(payload []byte, mac []byte, alg SignatureAlgorithm) error {
+	expected, err := ctx.hmac(payload, alg)
+	if err != nil {
+		return errors.New("square/go-jose: failed to compute hmac")
+	}
+
+	if len(mac) != len(expected) {
+		return errors.New("square/go-jose: invalid hmac")
+	}
+
+	match := subtle.ConstantTimeCompare(mac, expected)
+	if match != 1 {
+		return errors.New("square/go-jose: invalid hmac")
+	}
+
+	return nil
+}
+
+// Compute the HMAC based on the given alg value
+func (ctx symmetricMac) hmac(payload []byte, alg SignatureAlgorithm) ([]byte, error) {
+	var hash func() hash.Hash
+
+	switch alg {
+	case HS256:
+		hash = sha256.New
+	case HS384:
+		hash = sha512.New384
+	case HS512:
+		hash = sha512.New
+	default:
+		return nil, ErrUnsupportedAlgorithm
+	}
+
+	hmac := hmac.New(hash, ctx.key)
+
+	// According to documentation, Write() on hash never fails
+	_, _ = hmac.Write(payload)
+	return hmac.Sum(nil), nil
+}