1 // Copyright 2014 The Chromium Authors. All rights reserved.
2 // Use of this source code is governed by a BSD-style license that can be
3 // found in the LICENSE file.
7 #include "base/numerics/safe_math.h"
8 #include "content/child/webcrypto/crypto_data.h"
9 #include "content/child/webcrypto/nss/aes_key_nss.h"
10 #include "content/child/webcrypto/nss/key_nss.h"
11 #include "content/child/webcrypto/nss/sym_key_nss.h"
12 #include "content/child/webcrypto/nss/util_nss.h"
13 #include "content/child/webcrypto/status.h"
14 #include "content/child/webcrypto/webcrypto_util.h"
15 #include "crypto/scoped_nss_types.h"
16 #include "third_party/WebKit/public/platform/WebCryptoAlgorithmParams.h"
17 #include "third_party/WebKit/public/platform/WebCryptoKeyAlgorithm.h"
25 // The Default IV for AES-KW. See http://www.ietf.org/rfc/rfc3394.txt
27 const unsigned char kAesIv[] = {0xA6, 0xA6, 0xA6, 0xA6, 0xA6, 0xA6, 0xA6, 0xA6};
29 // The result of unwrapping is a SymKey rather than a buffer. This is a
30 // consequence of how NSS exposes AES-KW. Subsequent code can extract the value
31 // of the sym key to interpret it as key bytes in another format.
32 Status DoUnwrapSymKeyAesKw(const CryptoData& wrapped_key_data,
33 PK11SymKey* wrapping_key,
34 CK_MECHANISM_TYPE mechanism,
36 crypto::ScopedPK11SymKey* unwrapped_key) {
37 DCHECK_GE(wrapped_key_data.byte_length(), 24u);
38 DCHECK_EQ(wrapped_key_data.byte_length() % 8, 0u);
40 SECItem iv_item = MakeSECItemForBuffer(CryptoData(kAesIv, sizeof(kAesIv)));
41 crypto::ScopedSECItem param_item(
42 PK11_ParamFromIV(CKM_NSS_AES_KEY_WRAP, &iv_item));
44 return Status::ErrorUnexpected();
46 SECItem cipher_text = MakeSECItemForBuffer(wrapped_key_data);
48 // The plaintext length is always 64 bits less than the data size.
49 const unsigned int plaintext_length = wrapped_key_data.byte_length() - 8;
52 // Part of workaround for
53 // https://bugzilla.mozilla.org/show_bug.cgi?id=981170. See the explanation
54 // later in this function.
58 crypto::ScopedPK11SymKey new_key(
59 PK11_UnwrapSymKeyWithFlags(wrapping_key,
68 // TODO(padolph): Use NSS PORT_GetError() and friends to report a more
69 // accurate error, providing if doesn't leak any information to web pages
70 // about other web crypto users, key details, etc.
72 return Status::OperationError();
75 // Workaround for https://bugzilla.mozilla.org/show_bug.cgi?id=981170
76 // which was fixed in NSS 3.16.0.
77 // If unwrap fails, NSS nevertheless returns a valid-looking PK11SymKey,
78 // with a reasonable length but with key data pointing to uninitialized
80 // To understand this workaround see the fix for 981170:
81 // https://hg.mozilla.org/projects/nss/rev/753bb69e543c
82 if (!NSS_VersionCheck("3.16") && PORT_GetError() == SEC_ERROR_BAD_DATA)
83 return Status::OperationError();
86 *unwrapped_key = new_key.Pass();
87 return Status::Success();
90 Status WrapSymKeyAesKw(PK11SymKey* key,
91 PK11SymKey* wrapping_key,
92 std::vector<uint8_t>* buffer) {
93 // The data size must be at least 16 bytes and a multiple of 8 bytes.
94 // RFC 3394 does not specify a maximum allowed data length, but since only
95 // keys are being wrapped in this application (which are small), a reasonable
96 // max limit is whatever will fit into an unsigned. For the max size test,
97 // note that AES Key Wrap always adds 8 bytes to the input data size.
98 const unsigned int input_length = PK11_GetKeyLength(key);
99 DCHECK_GE(input_length, 16u);
100 DCHECK((input_length % 8) == 0);
102 SECItem iv_item = MakeSECItemForBuffer(CryptoData(kAesIv, sizeof(kAesIv)));
103 crypto::ScopedSECItem param_item(
104 PK11_ParamFromIV(CKM_NSS_AES_KEY_WRAP, &iv_item));
106 return Status::ErrorUnexpected();
108 base::CheckedNumeric<unsigned int> output_length = input_length;
110 if (!output_length.IsValid())
111 return Status::ErrorDataTooLarge();
113 buffer->resize(output_length.ValueOrDie());
114 SECItem wrapped_key_item = MakeSECItemForBuffer(CryptoData(*buffer));
116 if (SECSuccess != PK11_WrapSymKey(CKM_NSS_AES_KEY_WRAP,
120 &wrapped_key_item)) {
121 return Status::OperationError();
123 if (output_length.ValueOrDie() != wrapped_key_item.len)
124 return Status::ErrorUnexpected();
126 return Status::Success();
129 class AesKwCryptoAlgorithmNss : public AesAlgorithm {
131 AesKwCryptoAlgorithmNss()
133 CKM_NSS_AES_KEY_WRAP,
135 blink::WebCryptoKeyUsageWrapKey | blink::WebCryptoKeyUsageUnwrapKey,
138 Status Encrypt(const blink::WebCryptoAlgorithm& algorithm,
139 const blink::WebCryptoKey& wrapping_key,
140 const CryptoData& data,
141 std::vector<uint8_t>* buffer) const override {
142 if (data.byte_length() < 16)
143 return Status::ErrorDataTooSmall();
144 if (data.byte_length() % 8)
145 return Status::ErrorInvalidAesKwDataLength();
147 // Due to limitations in the NSS API for the AES-KW algorithm, |data| must
148 // be temporarily viewed as a symmetric key to be wrapped (encrypted).
149 SECItem data_item = MakeSECItemForBuffer(data);
150 crypto::ScopedPK11Slot slot(PK11_GetInternalSlot());
151 crypto::ScopedPK11SymKey data_as_sym_key(
152 PK11_ImportSymKey(slot.get(),
158 if (!data_as_sym_key)
159 return Status::OperationError();
161 return WrapSymKeyAesKw(
162 data_as_sym_key.get(), SymKeyNss::Cast(wrapping_key)->key(), buffer);
165 Status Decrypt(const blink::WebCryptoAlgorithm& algorithm,
166 const blink::WebCryptoKey& wrapping_key,
167 const CryptoData& data,
168 std::vector<uint8_t>* buffer) const override {
169 if (data.byte_length() < 24)
170 return Status::ErrorDataTooSmall();
171 if (data.byte_length() % 8)
172 return Status::ErrorInvalidAesKwDataLength();
174 // Due to limitations in the NSS API for the AES-KW algorithm, |data| must
175 // be temporarily viewed as a symmetric key to be unwrapped (decrypted).
176 crypto::ScopedPK11SymKey decrypted;
177 Status status = DoUnwrapSymKeyAesKw(data,
178 SymKeyNss::Cast(wrapping_key)->key(),
182 if (status.IsError())
185 // Once the decrypt is complete, extract the resultant raw bytes from NSS
186 // and return them to the caller.
187 if (PK11_ExtractKeyValue(decrypted.get()) != SECSuccess)
188 return Status::OperationError();
189 const SECItem* const key_data = PK11_GetKeyData(decrypted.get());
191 return Status::OperationError();
192 buffer->assign(key_data->data, key_data->data + key_data->len);
194 return Status::Success();
200 AlgorithmImplementation* CreatePlatformAesKwImplementation() {
201 return new AesKwCryptoAlgorithmNss;
204 } // namespace webcrypto
206 } // namespace content