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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"
"gopkg.in/square/go-jose.v2/json"
)
// 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)
Options() EncrypterOptions
}
// 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
extraHeaders map[HeaderKey]interface{}
}
type recipientKeyInfo struct {
keyID string
keyAlg KeyAlgorithm
keyEncrypter keyEncrypter
}
// EncrypterOptions represents options that can be set on new encrypters.
type EncrypterOptions struct {
Compression CompressionAlgorithm
// Optional map of additional keys to be inserted into the protected header
// of a JWS object. Some specifications which make use of JWS like to insert
// additional values here. All values must be JSON-serializable.
ExtraHeaders map[HeaderKey]interface{}
}
// WithHeader adds an arbitrary value to the ExtraHeaders map, initializing it
// if necessary. It returns itself and so can be used in a fluent style.
func (eo *EncrypterOptions) WithHeader(k HeaderKey, v interface{}) *EncrypterOptions {
if eo.ExtraHeaders == nil {
eo.ExtraHeaders = map[HeaderKey]interface{}{}
}
eo.ExtraHeaders[k] = v
return eo
}
// WithContentType adds a content type ("cty") header and returns the updated
// EncrypterOptions.
func (eo *EncrypterOptions) WithContentType(contentType ContentType) *EncrypterOptions {
return eo.WithHeader(HeaderContentType, contentType)
}
// WithType adds a type ("typ") header and returns the updated EncrypterOptions.
func (eo *EncrypterOptions) WithType(typ ContentType) *EncrypterOptions {
return eo.WithHeader(HeaderType, typ)
}
// Recipient represents an algorithm/key to encrypt messages to.
//
// PBES2Count and PBES2Salt correspond with the "p2c" and "p2s" headers used
// on the password-based encryption algorithms PBES2-HS256+A128KW,
// PBES2-HS384+A192KW, and PBES2-HS512+A256KW. If they are not provided a safe
// default of 100000 will be used for the count and a 128-bit random salt will
// be generated.
type Recipient struct {
Algorithm KeyAlgorithm
Key interface{}
KeyID string
PBES2Count int
PBES2Salt []byte
}
// NewEncrypter creates an appropriate encrypter based on the key type
func NewEncrypter(enc ContentEncryption, rcpt Recipient, opts *EncrypterOptions) (Encrypter, error) {
encrypter := &genericEncrypter{
contentAlg: enc,
recipients: []recipientKeyInfo{},
cipher: getContentCipher(enc),
}
if opts != nil {
encrypter.compressionAlg = opts.Compression
encrypter.extraHeaders = opts.ExtraHeaders
}
if encrypter.cipher == nil {
return nil, ErrUnsupportedAlgorithm
}
var keyID string
var rawKey interface{}
switch encryptionKey := rcpt.Key.(type) {
case JSONWebKey:
keyID, rawKey = encryptionKey.KeyID, encryptionKey.Key
case *JSONWebKey:
keyID, rawKey = encryptionKey.KeyID, encryptionKey.Key
case OpaqueKeyEncrypter:
keyID, rawKey = encryptionKey.KeyID(), encryptionKey
default:
rawKey = encryptionKey
}
switch rcpt.Algorithm {
case DIRECT:
// Direct encryption mode must be treated differently
if reflect.TypeOf(rawKey) != reflect.TypeOf([]byte{}) {
return nil, ErrUnsupportedKeyType
}
if encrypter.cipher.keySize() != len(rawKey.([]byte)) {
return nil, ErrInvalidKeySize
}
encrypter.keyGenerator = staticKeyGenerator{
key: rawKey.([]byte),
}
recipientInfo, _ := newSymmetricRecipient(rcpt.Algorithm, rawKey.([]byte))
recipientInfo.keyID = keyID
if rcpt.KeyID != "" {
recipientInfo.keyID = rcpt.KeyID
}
encrypter.recipients = []recipientKeyInfo{recipientInfo}
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),
}
recipientInfo, _ := newECDHRecipient(rcpt.Algorithm, rawKey.(*ecdsa.PublicKey))
recipientInfo.keyID = keyID
if rcpt.KeyID != "" {
recipientInfo.keyID = rcpt.KeyID
}
encrypter.recipients = []recipientKeyInfo{recipientInfo}
return encrypter, nil
default:
// Can just add a standard recipient
encrypter.keyGenerator = randomKeyGenerator{
size: encrypter.cipher.keySize(),
}
err := encrypter.addRecipient(rcpt)
return encrypter, err
}
}
// NewMultiEncrypter creates a multi-encrypter based on the given parameters
func NewMultiEncrypter(enc ContentEncryption, rcpts []Recipient, opts *EncrypterOptions) (Encrypter, error) {
cipher := getContentCipher(enc)
if cipher == nil {
return nil, ErrUnsupportedAlgorithm
}
if rcpts == nil || len(rcpts) == 0 {
return nil, fmt.Errorf("square/go-jose: recipients is nil or empty")
}
encrypter := &genericEncrypter{
contentAlg: enc,
recipients: []recipientKeyInfo{},
cipher: cipher,
keyGenerator: randomKeyGenerator{
size: cipher.keySize(),
},
}
if opts != nil {
encrypter.compressionAlg = opts.Compression
encrypter.extraHeaders = opts.ExtraHeaders
}
for _, recipient := range rcpts {
err := encrypter.addRecipient(recipient)
if err != nil {
return nil, err
}
}
return encrypter, nil
}
func (ctx *genericEncrypter) addRecipient(recipient Recipient) (err error) {
var recipientInfo recipientKeyInfo
switch recipient.Algorithm {
case DIRECT, ECDH_ES:
return fmt.Errorf("square/go-jose: key algorithm '%s' not supported in multi-recipient mode", recipient.Algorithm)
}
recipientInfo, err = makeJWERecipient(recipient.Algorithm, recipient.Key)
if recipient.KeyID != "" {
recipientInfo.keyID = recipient.KeyID
}
switch recipient.Algorithm {
case PBES2_HS256_A128KW, PBES2_HS384_A192KW, PBES2_HS512_A256KW:
if sr, ok := recipientInfo.keyEncrypter.(*symmetricKeyCipher); ok {
sr.p2c = recipient.PBES2Count
sr.p2s = recipient.PBES2Salt
}
}
if err == nil {
ctx.recipients = append(ctx.recipients, recipientInfo)
}
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 string:
return newSymmetricRecipient(alg, []byte(encryptionKey))
case *JSONWebKey:
recipient, err := makeJWERecipient(alg, encryptionKey.Key)
recipient.keyID = encryptionKey.KeyID
return recipient, err
}
if encrypter, ok := encryptionKey.(OpaqueKeyEncrypter); ok {
return newOpaqueKeyEncrypter(alg, encrypter)
}
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 string:
return &symmetricKeyCipher{
key: []byte(decryptionKey),
}, nil
case JSONWebKey:
return newDecrypter(decryptionKey.Key)
case *JSONWebKey:
return newDecrypter(decryptionKey.Key)
}
if okd, ok := decryptionKey.(OpaqueKeyDecrypter); ok {
return &opaqueKeyDecrypter{decrypter: okd}, nil
}
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{}
err := obj.protected.set(headerEncryption, ctx.contentAlg)
if err != nil {
return nil, err
}
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
}
err = recipient.header.set(headerAlgorithm, info.keyAlg)
if err != nil {
return nil, err
}
if info.keyID != "" {
err = recipient.header.set(headerKeyID, info.keyID)
if err != nil {
return nil, err
}
}
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
}
err = obj.protected.set(headerCompression, ctx.compressionAlg)
if err != nil {
return nil, err
}
}
for k, v := range ctx.extraHeaders {
b, err := json.Marshal(v)
if err != nil {
return nil, err
}
(*obj.protected)[k] = makeRawMessage(b)
}
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
}
func (ctx *genericEncrypter) Options() EncrypterOptions {
return EncrypterOptions{
Compression: ctx.compressionAlg,
ExtraHeaders: ctx.extraHeaders,
}
}
// 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")
}
critical, err := headers.getCritical()
if err != nil {
return nil, fmt.Errorf("square/go-jose: invalid crit header")
}
if len(critical) > 0 {
return nil, fmt.Errorf("square/go-jose: unsupported crit header")
}
decrypter, err := newDecrypter(decryptionKey)
if err != nil {
return nil, err
}
cipher := getContentCipher(headers.getEncryption())
if cipher == nil {
return nil, fmt.Errorf("square/go-jose: unsupported enc value '%s'", string(headers.getEncryption()))
}
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 comp := obj.protected.getCompression(); comp != "" {
plaintext, err = decompress(comp, 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, Header, []byte, error) {
globalHeaders := obj.mergedHeaders(nil)
critical, err := globalHeaders.getCritical()
if err != nil {
return -1, Header{}, nil, fmt.Errorf("square/go-jose: invalid crit header")
}
if len(critical) > 0 {
return -1, Header{}, nil, fmt.Errorf("square/go-jose: unsupported crit header")
}
decrypter, err := newDecrypter(decryptionKey)
if err != nil {
return -1, Header{}, nil, err
}
encryption := globalHeaders.getEncryption()
cipher := getContentCipher(encryption)
if cipher == nil {
return -1, Header{}, nil, fmt.Errorf("square/go-jose: unsupported enc value '%s'", string(encryption))
}
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, Header{}, nil, ErrCryptoFailure
}
// The "zip" header parameter may only be present in the protected header.
if comp := obj.protected.getCompression(); comp != "" {
plaintext, err = decompress(comp, plaintext)
}
sanitized, err := headers.sanitized()
if err != nil {
return -1, Header{}, nil, fmt.Errorf("square/go-jose: failed to sanitize header: %v", err)
}
return index, sanitized, plaintext, err
}