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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/ecdsa"
"crypto/rsa"
"errors"
"fmt"
"reflect"
)
// Encrypter represents an encrypter which produces an encrypted JWE object.
type Encrypter interface {
Encrypt(plaintext []byte) (*JsonWebEncryption, error)
EncryptWithAuthData(plaintext []byte, aad []byte) (*JsonWebEncryption, error)
SetCompression(alg CompressionAlgorithm)
}
// MultiEncrypter represents an encrypter which supports multiple recipients.
type MultiEncrypter interface {
Encrypt(plaintext []byte) (*JsonWebEncryption, error)
EncryptWithAuthData(plaintext []byte, aad []byte) (*JsonWebEncryption, error)
SetCompression(alg CompressionAlgorithm)
AddRecipient(alg KeyAlgorithm, encryptionKey interface{}) error
}
// A generic content cipher
type contentCipher interface {
keySize() int
encrypt(cek []byte, aad, plaintext []byte) (*aeadParts, error)
decrypt(cek []byte, aad []byte, parts *aeadParts) ([]byte, error)
}
// A key generator (for generating/getting a CEK)
type keyGenerator interface {
keySize() int
genKey() ([]byte, rawHeader, error)
}
// A generic key encrypter
type keyEncrypter interface {
encryptKey(cek []byte, alg KeyAlgorithm) (recipientInfo, error) // Encrypt a key
}
// A generic key decrypter
type keyDecrypter interface {
decryptKey(headers rawHeader, recipient *recipientInfo, generator keyGenerator) ([]byte, error) // Decrypt a key
}
// A generic encrypter based on the given key encrypter and content cipher.
type genericEncrypter struct {
contentAlg ContentEncryption
compressionAlg CompressionAlgorithm
cipher contentCipher
recipients []recipientKeyInfo
keyGenerator keyGenerator
}
type recipientKeyInfo struct {
keyID string
keyAlg KeyAlgorithm
keyEncrypter keyEncrypter
}
// SetCompression sets a compression algorithm to be applied before encryption.
func (ctx *genericEncrypter) SetCompression(compressionAlg CompressionAlgorithm) {
ctx.compressionAlg = compressionAlg
}
// NewEncrypter creates an appropriate encrypter based on the key type
func NewEncrypter(alg KeyAlgorithm, enc ContentEncryption, encryptionKey interface{}) (Encrypter, error) {
encrypter := &genericEncrypter{
contentAlg: enc,
compressionAlg: NONE,
recipients: []recipientKeyInfo{},
cipher: getContentCipher(enc),
}
if encrypter.cipher == nil {
return nil, ErrUnsupportedAlgorithm
}
var keyID string
var rawKey interface{}
switch encryptionKey := encryptionKey.(type) {
case *JsonWebKey:
keyID = encryptionKey.KeyID
rawKey = encryptionKey.Key
default:
rawKey = encryptionKey
}
switch alg {
case DIRECT:
// Direct encryption mode must be treated differently
if reflect.TypeOf(rawKey) != reflect.TypeOf([]byte{}) {
return nil, ErrUnsupportedKeyType
}
encrypter.keyGenerator = staticKeyGenerator{
key: rawKey.([]byte),
}
recipient, _ := newSymmetricRecipient(alg, rawKey.([]byte))
if keyID != "" {
recipient.keyID = keyID
}
encrypter.recipients = []recipientKeyInfo{recipient}
return encrypter, nil
case ECDH_ES:
// ECDH-ES (w/o key wrapping) is similar to DIRECT mode
typeOf := reflect.TypeOf(rawKey)
if typeOf != reflect.TypeOf(&ecdsa.PublicKey{}) {
return nil, ErrUnsupportedKeyType
}
encrypter.keyGenerator = ecKeyGenerator{
size: encrypter.cipher.keySize(),
algID: string(enc),
publicKey: rawKey.(*ecdsa.PublicKey),
}
recipient, _ := newECDHRecipient(alg, rawKey.(*ecdsa.PublicKey))
if keyID != "" {
recipient.keyID = keyID
}
encrypter.recipients = []recipientKeyInfo{recipient}
return encrypter, nil
default:
// Can just add a standard recipient
encrypter.keyGenerator = randomKeyGenerator{
size: encrypter.cipher.keySize(),
}
err := encrypter.AddRecipient(alg, encryptionKey)
return encrypter, err
}
}
// NewMultiEncrypter creates a multi-encrypter based on the given parameters
func NewMultiEncrypter(enc ContentEncryption) (MultiEncrypter, error) {
cipher := getContentCipher(enc)
if cipher == nil {
return nil, ErrUnsupportedAlgorithm
}
encrypter := &genericEncrypter{
contentAlg: enc,
compressionAlg: NONE,
recipients: []recipientKeyInfo{},
cipher: cipher,
keyGenerator: randomKeyGenerator{
size: cipher.keySize(),
},
}
return encrypter, nil
}
func (ctx *genericEncrypter) AddRecipient(alg KeyAlgorithm, encryptionKey interface{}) (err error) {
var recipient recipientKeyInfo
switch alg {
case DIRECT, ECDH_ES:
return fmt.Errorf("square/go-jose: key algorithm '%s' not supported in multi-recipient mode", alg)
}
recipient, err = makeJWERecipient(alg, encryptionKey)
if err == nil {
ctx.recipients = append(ctx.recipients, recipient)
}
return err
}
func makeJWERecipient(alg KeyAlgorithm, encryptionKey interface{}) (recipientKeyInfo, error) {
switch encryptionKey := encryptionKey.(type) {
case *rsa.PublicKey:
return newRSARecipient(alg, encryptionKey)
case *ecdsa.PublicKey:
return newECDHRecipient(alg, encryptionKey)
case []byte:
return newSymmetricRecipient(alg, encryptionKey)
case *JsonWebKey:
recipient, err := makeJWERecipient(alg, encryptionKey.Key)
if err == nil && encryptionKey.KeyID != "" {
recipient.keyID = encryptionKey.KeyID
}
return recipient, err
default:
return recipientKeyInfo{}, ErrUnsupportedKeyType
}
}
// newDecrypter creates an appropriate decrypter based on the key type
func newDecrypter(decryptionKey interface{}) (keyDecrypter, error) {
switch decryptionKey := decryptionKey.(type) {
case *rsa.PrivateKey:
return &rsaDecrypterSigner{
privateKey: decryptionKey,
}, nil
case *ecdsa.PrivateKey:
return &ecDecrypterSigner{
privateKey: decryptionKey,
}, nil
case []byte:
return &symmetricKeyCipher{
key: decryptionKey,
}, nil
case *JsonWebKey:
return newDecrypter(decryptionKey.Key)
default:
return nil, ErrUnsupportedKeyType
}
}
// Implementation of encrypt method producing a JWE object.
func (ctx *genericEncrypter) Encrypt(plaintext []byte) (*JsonWebEncryption, error) {
return ctx.EncryptWithAuthData(plaintext, nil)
}
// Implementation of encrypt method producing a JWE object.
func (ctx *genericEncrypter) EncryptWithAuthData(plaintext, aad []byte) (*JsonWebEncryption, error) {
obj := &JsonWebEncryption{}
obj.aad = aad
obj.protected = &rawHeader{
Enc: ctx.contentAlg,
}
obj.recipients = make([]recipientInfo, len(ctx.recipients))
if len(ctx.recipients) == 0 {
return nil, fmt.Errorf("square/go-jose: no recipients to encrypt to")
}
cek, headers, err := ctx.keyGenerator.genKey()
if err != nil {
return nil, err
}
obj.protected.merge(&headers)
for i, info := range ctx.recipients {
recipient, err := info.keyEncrypter.encryptKey(cek, info.keyAlg)
if err != nil {
return nil, err
}
recipient.header.Alg = string(info.keyAlg)
if info.keyID != "" {
recipient.header.Kid = info.keyID
}
obj.recipients[i] = recipient
}
if len(ctx.recipients) == 1 {
// Move per-recipient headers into main protected header if there's
// only a single recipient.
obj.protected.merge(obj.recipients[0].header)
obj.recipients[0].header = nil
}
if ctx.compressionAlg != NONE {
plaintext, err = compress(ctx.compressionAlg, plaintext)
if err != nil {
return nil, err
}
obj.protected.Zip = ctx.compressionAlg
}
authData := obj.computeAuthData()
parts, err := ctx.cipher.encrypt(cek, authData, plaintext)
if err != nil {
return nil, err
}
obj.iv = parts.iv
obj.ciphertext = parts.ciphertext
obj.tag = parts.tag
return obj, nil
}
// Decrypt and validate the object and return the plaintext. Note that this
// function does not support multi-recipient, if you desire multi-recipient
// decryption use DecryptMulti instead.
func (obj JsonWebEncryption) Decrypt(decryptionKey interface{}) ([]byte, error) {
headers := obj.mergedHeaders(nil)
if len(obj.recipients) > 1 {
return nil, errors.New("square/go-jose: too many recipients in payload; expecting only one")
}
if len(headers.Crit) > 0 {
return nil, fmt.Errorf("square/go-jose: unsupported crit header")
}
decrypter, err := newDecrypter(decryptionKey)
if err != nil {
return nil, err
}
cipher := getContentCipher(headers.Enc)
if cipher == nil {
return nil, fmt.Errorf("square/go-jose: unsupported enc value '%s'", string(headers.Enc))
}
generator := randomKeyGenerator{
size: cipher.keySize(),
}
parts := &aeadParts{
iv: obj.iv,
ciphertext: obj.ciphertext,
tag: obj.tag,
}
authData := obj.computeAuthData()
var plaintext []byte
recipient := obj.recipients[0]
recipientHeaders := obj.mergedHeaders(&recipient)
cek, err := decrypter.decryptKey(recipientHeaders, &recipient, generator)
if err == nil {
// Found a valid CEK -- let's try to decrypt.
plaintext, err = cipher.decrypt(cek, authData, parts)
}
if plaintext == nil {
return nil, ErrCryptoFailure
}
// The "zip" header parameter may only be present in the protected header.
if obj.protected.Zip != "" {
plaintext, err = decompress(obj.protected.Zip, plaintext)
}
return plaintext, err
}
// DecryptMulti decrypts and validates the object and returns the plaintexts,
// with support for multiple recipients. It returns the index of the recipient
// for which the decryption was successful, the merged headers for that recipient,
// and the plaintext.
func (obj JsonWebEncryption) DecryptMulti(decryptionKey interface{}) (int, JoseHeader, []byte, error) {
globalHeaders := obj.mergedHeaders(nil)
if len(globalHeaders.Crit) > 0 {
return -1, JoseHeader{}, nil, fmt.Errorf("square/go-jose: unsupported crit header")
}
decrypter, err := newDecrypter(decryptionKey)
if err != nil {
return -1, JoseHeader{}, nil, err
}
cipher := getContentCipher(globalHeaders.Enc)
if cipher == nil {
return -1, JoseHeader{}, nil, fmt.Errorf("square/go-jose: unsupported enc value '%s'", string(globalHeaders.Enc))
}
generator := randomKeyGenerator{
size: cipher.keySize(),
}
parts := &aeadParts{
iv: obj.iv,
ciphertext: obj.ciphertext,
tag: obj.tag,
}
authData := obj.computeAuthData()
index := -1
var plaintext []byte
var headers rawHeader
for i, recipient := range obj.recipients {
recipientHeaders := obj.mergedHeaders(&recipient)
cek, err := decrypter.decryptKey(recipientHeaders, &recipient, generator)
if err == nil {
// Found a valid CEK -- let's try to decrypt.
plaintext, err = cipher.decrypt(cek, authData, parts)
if err == nil {
index = i
headers = recipientHeaders
break
}
}
}
if plaintext == nil || err != nil {
return -1, JoseHeader{}, nil, ErrCryptoFailure
}
// The "zip" header parameter may only be present in the protected header.
if obj.protected.Zip != "" {
plaintext, err = decompress(obj.protected.Zip, plaintext)
}
return index, headers.sanitized(), plaintext, err
}
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