summaryrefslogtreecommitdiffstats
path: root/crypto/aes_128_gcm_helpers_nss.cc
blob: 621f28b586f181c9bcc37ea9e4b162639fc6849c (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
// Copyright 2015 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#include "crypto/aes_128_gcm_helpers_nss.h"

#include <pkcs11t.h>
#include <seccomon.h>

#include "base/lazy_instance.h"
#include "base/macros.h"
#include "crypto/ghash.h"
#include "crypto/scoped_nss_types.h"

#if defined(USE_NSS_CERTS)
#include <dlfcn.h>
#endif

namespace crypto {
namespace {

// Declaration of the prototype both PK11_Decrypt and PK11_Encrypt follow.
using PK11_TransformFunction = SECStatus(PK11SymKey* symKey,
                                         CK_MECHANISM_TYPE mechanism,
                                         SECItem* param,
                                         unsigned char* out,
                                         unsigned int* outLen,
                                         unsigned int maxLen,
                                         const unsigned char* data,
                                         unsigned int dataLen);

// On Linux, dynamically link against the system version of libnss3.so. In
// order to continue working on systems without up-to-date versions of NSS,
// lookup PK11_Decrypt and PK11_Encrypt with dlsym.
//
// GcmSupportChecker is a singleton which caches the results of runtime symbol
// resolution of these symbols.
class GcmSupportChecker {
 public:
  PK11_TransformFunction* pk11_decrypt_func() { return pk11_decrypt_func_; }

  PK11_TransformFunction* pk11_encrypt_func() { return pk11_encrypt_func_; }

 private:
  friend struct base::DefaultLazyInstanceTraits<GcmSupportChecker>;

  GcmSupportChecker() {
#if !defined(USE_NSS_CERTS)
    // Using a bundled version of NSS that is guaranteed to have these symbols.
    pk11_decrypt_func_ = PK11_Decrypt;
    pk11_encrypt_func_ = PK11_Encrypt;
#else
    // Using system NSS libraries and PCKS #11 modules, which may not have the
    // necessary functions (PK11_Decrypt and PK11_Encrypt) or mechanism support
    // (CKM_AES_GCM).

    // If PK11_Decrypt() and PK11_Encrypt() were successfully resolved, then NSS
    // will support AES-GCM directly. This was introduced in NSS 3.15.
    pk11_decrypt_func_ = reinterpret_cast<PK11_TransformFunction*>(
        dlsym(RTLD_DEFAULT, "PK11_Decrypt"));
    pk11_encrypt_func_ = reinterpret_cast<PK11_TransformFunction*>(
        dlsym(RTLD_DEFAULT, "PK11_Encrypt"));
#endif
  }

  ~GcmSupportChecker() {}

  // |pk11_decrypt_func_| stores the runtime symbol resolution of PK11_Decrypt.
  PK11_TransformFunction* pk11_decrypt_func_;

  // |pk11_encrypt_func_| stores the runtime symbol resolution of PK11_Encrypt.
  PK11_TransformFunction* pk11_encrypt_func_;

  DISALLOW_COPY_AND_ASSIGN(GcmSupportChecker);
};

base::LazyInstance<GcmSupportChecker>::Leaky g_gcm_support_checker =
    LAZY_INSTANCE_INITIALIZER;

}  // namespace

// Calls PK11_Decrypt if it's available. Otherwise, emulates CKM_AES_GCM using
// CKM_AES_CTR and the GaloisHash class.
SECStatus PK11DecryptHelper(PK11SymKey* key,
                            CK_MECHANISM_TYPE mechanism,
                            SECItem* param,
                            unsigned char* out,
                            unsigned int* out_len,
                            unsigned int max_len,
                            const unsigned char* data,
                            unsigned int data_len) {
  // If PK11_Decrypt() was successfully resolved or if bundled version of NSS is
  // being used, then NSS will support AES-GCM directly.
  PK11_TransformFunction* pk11_decrypt_func =
      g_gcm_support_checker.Get().pk11_decrypt_func();

  if (pk11_decrypt_func != nullptr) {
    return pk11_decrypt_func(key, mechanism, param, out, out_len, max_len, data,
                             data_len);
  }

  // Otherwise, the user has an older version of NSS. Regrettably, NSS 3.14.x
  // has a bug in the AES GCM code
  // (https://bugzilla.mozilla.org/show_bug.cgi?id=853285), as well as missing
  // the PK11_Decrypt function
  // (https://bugzilla.mozilla.org/show_bug.cgi?id=854063), both of which are
  // resolved in NSS 3.15.

  CHECK_EQ(mechanism, static_cast<CK_MECHANISM_TYPE>(CKM_AES_GCM));
  CHECK_EQ(param->len, sizeof(CK_GCM_PARAMS));

  const CK_GCM_PARAMS* gcm_params =
      reinterpret_cast<CK_GCM_PARAMS*>(param->data);

  const CK_ULONG auth_tag_size = gcm_params->ulTagBits / 8;

  if (gcm_params->ulIvLen != 12u) {
    DVLOG(1) << "ulIvLen is not equal to 12";
    PORT_SetError(SEC_ERROR_INPUT_LEN);
    return SECFailure;
  }

  SECItem my_param = {siBuffer, nullptr, 0};

  // Step 2. Let H = CIPH_K(128 '0' bits).
  unsigned char ghash_key[16] = {0};
  crypto::ScopedPK11Context ctx(
      PK11_CreateContextBySymKey(CKM_AES_ECB, CKA_ENCRYPT, key, &my_param));
  if (!ctx) {
    DVLOG(1) << "PK11_CreateContextBySymKey failed";
    return SECFailure;
  }
  int output_len;
  if (PK11_CipherOp(ctx.get(), ghash_key, &output_len, sizeof(ghash_key),
                    ghash_key, sizeof(ghash_key)) != SECSuccess) {
    DVLOG(1) << "PK11_CipherOp failed";
    return SECFailure;
  }

  if (PK11_Finalize(ctx.get()) != SECSuccess) {
    DVLOG(1) << "PK11_Finalize failed";
    return SECFailure;
  }

  if (output_len != sizeof(ghash_key)) {
    DVLOG(1) << "Wrong output length";
    PORT_SetError(SEC_ERROR_LIBRARY_FAILURE);
    return SECFailure;
  }

  // Step 3. If len(IV)=96, then let J0 = IV || 31 '0' bits || 1.
  CK_AES_CTR_PARAMS ctr_params = {0};
  ctr_params.ulCounterBits = 32;
  memcpy(ctr_params.cb, gcm_params->pIv, gcm_params->ulIvLen);
  ctr_params.cb[12] = 0;
  ctr_params.cb[13] = 0;
  ctr_params.cb[14] = 0;
  ctr_params.cb[15] = 1;

  my_param.type = siBuffer;
  my_param.data = reinterpret_cast<unsigned char*>(&ctr_params);
  my_param.len = sizeof(ctr_params);

  ctx.reset(
      PK11_CreateContextBySymKey(CKM_AES_CTR, CKA_ENCRYPT, key, &my_param));
  if (!ctx) {
    DVLOG(1) << "PK11_CreateContextBySymKey failed";
    return SECFailure;
  }

  // Step 6. Calculate the encryption mask of GCTR_K(J0, ...).
  unsigned char tag_mask[16] = {0};
  if (PK11_CipherOp(ctx.get(), tag_mask, &output_len, sizeof(tag_mask),
                    tag_mask, sizeof(tag_mask)) != SECSuccess) {
    DVLOG(1) << "PK11_CipherOp failed";
    return SECFailure;
  }
  if (output_len != sizeof(tag_mask)) {
    DVLOG(1) << "Wrong output length";
    PORT_SetError(SEC_ERROR_LIBRARY_FAILURE);
    return SECFailure;
  }

  if (data_len < auth_tag_size) {
    PORT_SetError(SEC_ERROR_INPUT_LEN);
    return SECFailure;
  }

  // The const_cast for |data| can be removed if system NSS libraries are
  // NSS 3.14.1 or later (NSS bug
  // https://bugzilla.mozilla.org/show_bug.cgi?id=808218).
  if (PK11_CipherOp(ctx.get(), out, &output_len, max_len,
                    const_cast<unsigned char*>(data),
                    data_len - auth_tag_size) != SECSuccess) {
    DVLOG(1) << "PK11_CipherOp failed";
    return SECFailure;
  }

  if (PK11_Finalize(ctx.get()) != SECSuccess) {
    DVLOG(1) << "PK11_Finalize failed";
    return SECFailure;
  }

  if (static_cast<unsigned int>(output_len) != data_len - auth_tag_size) {
    DVLOG(1) << "Wrong output length";
    PORT_SetError(SEC_ERROR_LIBRARY_FAILURE);
    return SECFailure;
  }

  crypto::GaloisHash ghash(ghash_key);
  ghash.UpdateAdditional(gcm_params->pAAD, gcm_params->ulAADLen);
  ghash.UpdateCiphertext(data, output_len);
  unsigned char auth_tag[auth_tag_size];
  ghash.Finish(auth_tag, auth_tag_size);
  for (unsigned int i = 0; i < auth_tag_size; i++) {
    auth_tag[i] ^= tag_mask[i];
  }

  if (NSS_SecureMemcmp(auth_tag, data + output_len, auth_tag_size) != 0) {
    PORT_SetError(SEC_ERROR_BAD_DATA);
    return SECFailure;
  }

  *out_len = output_len;
  return SECSuccess;
}

// Calls PK11_Encrypt if it's available. Otherwise, emulates CKM_AES_GCM using
// CKM_AES_CTR and the GaloisHash class.
SECStatus PK11EncryptHelper(PK11SymKey* key,
                            CK_MECHANISM_TYPE mechanism,
                            SECItem* param,
                            unsigned char* out,
                            unsigned int* out_len,
                            unsigned int max_len,
                            const unsigned char* data,
                            unsigned int data_len) {
  // If PK11_Encrypt() was successfully resolved or if bundled version of NSS is
  // being used, then NSS will support AES-GCM directly.
  PK11_TransformFunction* pk11_encrypt_func =
      g_gcm_support_checker.Get().pk11_encrypt_func();

  if (pk11_encrypt_func != nullptr) {
    return pk11_encrypt_func(key, mechanism, param, out, out_len, max_len, data,
                             data_len);
  }

  // Otherwise, the user has an older version of NSS. Regrettably, NSS 3.14.x
  // has a bug in the AES GCM code
  // (https://bugzilla.mozilla.org/show_bug.cgi?id=853285), as well as missing
  // the PK11_Encrypt function
  // (https://bugzilla.mozilla.org/show_bug.cgi?id=854063), both of which are
  // resolved in NSS 3.15.

  CHECK_EQ(mechanism, static_cast<CK_MECHANISM_TYPE>(CKM_AES_GCM));
  CHECK_EQ(param->len, sizeof(CK_GCM_PARAMS));

  const CK_GCM_PARAMS* gcm_params =
      reinterpret_cast<CK_GCM_PARAMS*>(param->data);

  const CK_ULONG auth_tag_size = gcm_params->ulTagBits / 8;

  if (max_len < auth_tag_size) {
    DVLOG(1) << "max_len is less than kAuthTagSize";
    PORT_SetError(SEC_ERROR_OUTPUT_LEN);
    return SECFailure;
  }

  if (gcm_params->ulIvLen != 12u) {
    DVLOG(1) << "ulIvLen is not equal to 12";
    PORT_SetError(SEC_ERROR_INPUT_LEN);
    return SECFailure;
  }

  SECItem my_param = {siBuffer, nullptr, 0};

  // Step 1. Let H = CIPH_K(128 '0' bits).
  unsigned char ghash_key[16] = {0};
  crypto::ScopedPK11Context ctx(
      PK11_CreateContextBySymKey(CKM_AES_ECB, CKA_ENCRYPT, key, &my_param));
  if (!ctx) {
    DVLOG(1) << "PK11_CreateContextBySymKey failed";
    return SECFailure;
  }
  int output_len;
  if (PK11_CipherOp(ctx.get(), ghash_key, &output_len, sizeof(ghash_key),
                    ghash_key, sizeof(ghash_key)) != SECSuccess) {
    DVLOG(1) << "PK11_CipherOp failed";
    return SECFailure;
  }

  if (PK11_Finalize(ctx.get()) != SECSuccess) {
    DVLOG(1) << "PK11_Finalize failed";
    return SECFailure;
  }

  if (output_len != sizeof(ghash_key)) {
    DVLOG(1) << "Wrong output length";
    PORT_SetError(SEC_ERROR_LIBRARY_FAILURE);
    return SECFailure;
  }

  // Step 2. If len(IV)=96, then let J0 = IV || 31 '0' bits || 1.
  CK_AES_CTR_PARAMS ctr_params = {0};
  ctr_params.ulCounterBits = 32;
  memcpy(ctr_params.cb, gcm_params->pIv, gcm_params->ulIvLen);
  ctr_params.cb[12] = 0;
  ctr_params.cb[13] = 0;
  ctr_params.cb[14] = 0;
  ctr_params.cb[15] = 1;

  my_param.type = siBuffer;
  my_param.data = reinterpret_cast<unsigned char*>(&ctr_params);
  my_param.len = sizeof(ctr_params);

  ctx.reset(
      PK11_CreateContextBySymKey(CKM_AES_CTR, CKA_ENCRYPT, key, &my_param));
  if (!ctx) {
    DVLOG(1) << "PK11_CreateContextBySymKey failed";
    return SECFailure;
  }

  // Step 6. Calculate the encryption mask of GCTR_K(J0, ...).
  unsigned char tag_mask[16] = {0};
  if (PK11_CipherOp(ctx.get(), tag_mask, &output_len, sizeof(tag_mask),
                    tag_mask, sizeof(tag_mask)) != SECSuccess) {
    DVLOG(1) << "PK11_CipherOp failed";
    return SECFailure;
  }
  if (output_len != sizeof(tag_mask)) {
    DVLOG(1) << "Wrong output length";
    PORT_SetError(SEC_ERROR_LIBRARY_FAILURE);
    return SECFailure;
  }

  // The const_cast for |data| can be removed if system NSS libraries are
  // NSS 3.14.1 or later (NSS bug
  // https://bugzilla.mozilla.org/show_bug.cgi?id=808218).
  if (PK11_CipherOp(ctx.get(), out, &output_len, max_len,
                    const_cast<unsigned char*>(data), data_len) != SECSuccess) {
    DVLOG(1) << "PK11_CipherOp failed";
    return SECFailure;
  }

  if (PK11_Finalize(ctx.get()) != SECSuccess) {
    DVLOG(1) << "PK11_Finalize failed";
    return SECFailure;
  }

  if (static_cast<unsigned int>(output_len) != data_len) {
    DVLOG(1) << "Wrong output length";
    PORT_SetError(SEC_ERROR_LIBRARY_FAILURE);
    return SECFailure;
  }

  if ((max_len - auth_tag_size) < static_cast<unsigned int>(output_len)) {
    DVLOG(1) << "(max_len - kAuthTagSize) is less than output_len";
    PORT_SetError(SEC_ERROR_OUTPUT_LEN);
    return SECFailure;
  }

  crypto::GaloisHash ghash(ghash_key);
  ghash.UpdateAdditional(gcm_params->pAAD, gcm_params->ulAADLen);
  ghash.UpdateCiphertext(out, output_len);
  ghash.Finish(out + output_len, auth_tag_size);
  for (unsigned int i = 0; i < auth_tag_size; i++) {
    out[output_len + i] ^= tag_mask[i];
  }

  *out_len = output_len + auth_tag_size;
  return SECSuccess;
}

}  // namespace crypto