net/quic/crypto/aes_128_gcm_12_decrypter_nss.cc

   1 // Copyright (c) 2013 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.
   4
   5 #include "net/quic/crypto/aes_128_gcm_12_decrypter.h"
   6
   7 #include <pk11pub.h>
   8 #include <secerr.h>
   9
  10 #include "base/lazy_instance.h"
  11 #include "crypto/ghash.h"
  12 #include "crypto/scoped_nss_types.h"
  13
  14 #if defined(USE_NSS_CERTS)
  15 #include <dlfcn.h>
  16 #endif
  17
  18 using base::StringPiece;
  19
  20 namespace net {
  21
  22 namespace {
  23
  24 const size_t kKeySize = 16;
  25 const size_t kNoncePrefixSize = 4;
  26
  27 // On Linux, dynamically link against the system version of libnss3.so. In
  28 // order to continue working on systems without up-to-date versions of NSS,
  29 // lookup PK11_Decrypt with dlsym.
  30
  31 // GcmSupportChecker is a singleton which caches the results of runtime symbol
  32 // resolution of PK11_Decrypt.
  33 class GcmSupportChecker {
  34  public:
  35   static PK11_DecryptFunction pk11_decrypt_func() {
  36     return pk11_decrypt_func_;
  37   }
  38
  39  private:
  40   friend struct base::DefaultLazyInstanceTraits<GcmSupportChecker>;
  41
  42   GcmSupportChecker() {
  43 #if !defined(USE_NSS_CERTS)
  44     // Using a bundled version of NSS that is guaranteed to have this symbol.
  45     pk11_decrypt_func_ = PK11_Decrypt;
  46 #else
  47     // Using system NSS libraries and PCKS #11 modules, which may not have the
  48     // necessary function (PK11_Decrypt) or mechanism support (CKM_AES_GCM).
  49
  50     // If PK11_Decrypt() was successfully resolved, then NSS will support
  51     // AES-GCM directly. This was introduced in NSS 3.15.
  52     pk11_decrypt_func_ = (PK11_DecryptFunction)dlsym(RTLD_DEFAULT,
  53                                                      "PK11_Decrypt");
  54 #endif
  55   }
  56
  57   // |pk11_decrypt_func_| stores the runtime symbol resolution of PK11_Decrypt.
  58   static PK11_DecryptFunction pk11_decrypt_func_;
  59 };
  60
  61 // static
  62 PK11_DecryptFunction GcmSupportChecker::pk11_decrypt_func_ = nullptr;
  63
  64 base::LazyInstance<GcmSupportChecker>::Leaky g_gcm_support_checker =
  65     LAZY_INSTANCE_INITIALIZER;
  66
  67 // Calls PK11_Decrypt if it's available.  Otherwise, emulates CKM_AES_GCM using
  68 // CKM_AES_CTR and the GaloisHash class.
  69 SECStatus My_Decrypt(PK11SymKey* key,
  70                      CK_MECHANISM_TYPE mechanism,
  71                      SECItem* param,
  72                      unsigned char* out,
  73                      unsigned int* out_len,
  74                      unsigned int max_len,
  75                      const unsigned char* enc,
  76                      unsigned int enc_len) {
  77   // If PK11_Decrypt() was successfully resolved or if bundled version of NSS is
  78   // being used, then NSS will support AES-GCM directly.
  79   PK11_DecryptFunction pk11_decrypt_func =
  80       GcmSupportChecker::pk11_decrypt_func();
  81   if (pk11_decrypt_func != nullptr) {
  82     return pk11_decrypt_func(key, mechanism, param, out, out_len, max_len, enc,
  83                              enc_len);
  84   }
  85
  86   // Otherwise, the user has an older version of NSS. Regrettably, NSS 3.14.x
  87   // has a bug in the AES GCM code
  88   // (https://bugzilla.mozilla.org/show_bug.cgi?id=853285), as well as missing
  89   // the PK11_Decrypt function
  90   // (https://bugzilla.mozilla.org/show_bug.cgi?id=854063), both of which are
  91   // resolved in NSS 3.15.
  92
  93   DCHECK_EQ(mechanism, static_cast<CK_MECHANISM_TYPE>(CKM_AES_GCM));
  94   DCHECK_EQ(param->len, sizeof(CK_GCM_PARAMS));
  95
  96   const CK_GCM_PARAMS* gcm_params =
  97       reinterpret_cast<CK_GCM_PARAMS*>(param->data);
  98
  99   DCHECK_EQ(gcm_params->ulTagBits,
 100             static_cast<CK_ULONG>(Aes128Gcm12Decrypter::kAuthTagSize * 8));
 101   if (gcm_params->ulIvLen != 12u) {
 102     DVLOG(1) << "ulIvLen is not equal to 12";
 103     PORT_SetError(SEC_ERROR_INPUT_LEN);
 104     return SECFailure;
 105   }
 106
 107   SECItem my_param = { siBuffer, nullptr, 0 };
 108
 109   // Step 2. Let H = CIPH_K(128 '0' bits).
 110   unsigned char ghash_key[16] = {0};
 111   crypto::ScopedPK11Context ctx(PK11_CreateContextBySymKey(
 112       CKM_AES_ECB, CKA_ENCRYPT, key, &my_param));
 113   if (!ctx) {
 114     DVLOG(1) << "PK11_CreateContextBySymKey failed";
 115     return SECFailure;
 116   }
 117   int output_len;
 118   if (PK11_CipherOp(ctx.get(), ghash_key, &output_len, sizeof(ghash_key),
 119                     ghash_key, sizeof(ghash_key)) != SECSuccess) {
 120     DVLOG(1) << "PK11_CipherOp failed";
 121     return SECFailure;
 122   }
 123
 124   PK11_Finalize(ctx.get());
 125
 126   if (output_len != sizeof(ghash_key)) {
 127     DVLOG(1) << "Wrong output length";
 128     PORT_SetError(SEC_ERROR_LIBRARY_FAILURE);
 129     return SECFailure;
 130   }
 131
 132   // Step 3. If len(IV)=96, then let J0 = IV || 31 '0' bits || 1.
 133   CK_AES_CTR_PARAMS ctr_params = {0};
 134   ctr_params.ulCounterBits = 32;
 135   memcpy(ctr_params.cb, gcm_params->pIv, gcm_params->ulIvLen);
 136   ctr_params.cb[12] = 0;
 137   ctr_params.cb[13] = 0;
 138   ctr_params.cb[14] = 0;
 139   ctr_params.cb[15] = 1;
 140
 141   my_param.type = siBuffer;
 142   my_param.data = reinterpret_cast<unsigned char*>(&ctr_params);
 143   my_param.len = sizeof(ctr_params);
 144
 145   ctx.reset(PK11_CreateContextBySymKey(CKM_AES_CTR, CKA_ENCRYPT, key,
 146                                        &my_param));
 147   if (!ctx) {
 148     DVLOG(1) << "PK11_CreateContextBySymKey failed";
 149     return SECFailure;
 150   }
 151
 152   // Step 6. Calculate the encryption mask of GCTR_K(J0, ...).
 153   unsigned char tag_mask[16] = {0};
 154   if (PK11_CipherOp(ctx.get(), tag_mask, &output_len, sizeof(tag_mask),
 155                     tag_mask, sizeof(tag_mask)) != SECSuccess) {
 156     DVLOG(1) << "PK11_CipherOp failed";
 157     return SECFailure;
 158   }
 159   if (output_len != sizeof(tag_mask)) {
 160     DVLOG(1) << "Wrong output length";
 161     PORT_SetError(SEC_ERROR_LIBRARY_FAILURE);
 162     return SECFailure;
 163   }
 164
 165   if (enc_len < Aes128Gcm12Decrypter::kAuthTagSize) {
 166     PORT_SetError(SEC_ERROR_INPUT_LEN);
 167     return SECFailure;
 168   }
 169
 170   // The const_cast for |enc| can be removed if system NSS libraries are
 171   // NSS 3.14.1 or later (NSS bug
 172   // https://bugzilla.mozilla.org/show_bug.cgi?id=808218).
 173   if (PK11_CipherOp(ctx.get(), out, &output_len, max_len,
 174           const_cast<unsigned char*>(enc),
 175           enc_len - Aes128Gcm12Decrypter::kAuthTagSize) != SECSuccess) {
 176     DVLOG(1) << "PK11_CipherOp failed";
 177     return SECFailure;
 178   }
 179
 180   PK11_Finalize(ctx.get());
 181
 182   if (static_cast<unsigned int>(output_len) !=
 183       enc_len - Aes128Gcm12Decrypter::kAuthTagSize) {
 184     DVLOG(1) << "Wrong output length";
 185     PORT_SetError(SEC_ERROR_LIBRARY_FAILURE);
 186     return SECFailure;
 187   }
 188
 189   crypto::GaloisHash ghash(ghash_key);
 190   ghash.UpdateAdditional(gcm_params->pAAD, gcm_params->ulAADLen);
 191   ghash.UpdateCiphertext(enc, output_len);
 192   unsigned char auth_tag[Aes128Gcm12Decrypter::kAuthTagSize];
 193   ghash.Finish(auth_tag, Aes128Gcm12Decrypter::kAuthTagSize);
 194   for (unsigned int i = 0; i < Aes128Gcm12Decrypter::kAuthTagSize; i++) {
 195     auth_tag[i] ^= tag_mask[i];
 196   }
 197
 198   if (NSS_SecureMemcmp(auth_tag, enc + output_len,
 199                        Aes128Gcm12Decrypter::kAuthTagSize) != 0) {
 200     PORT_SetError(SEC_ERROR_BAD_DATA);
 201     return SECFailure;
 202   }
 203
 204   *out_len = output_len;
 205   return SECSuccess;
 206 }
 207
 208 }  // namespace
 209
 210 Aes128Gcm12Decrypter::Aes128Gcm12Decrypter()
 211     : AeadBaseDecrypter(CKM_AES_GCM, My_Decrypt, kKeySize, kAuthTagSize,
 212                         kNoncePrefixSize) {
 213   static_assert(kKeySize <= kMaxKeySize, "key size too big");
 214   static_assert(kNoncePrefixSize <= kMaxNoncePrefixSize,
 215                 "nonce prefix size too big");
 216   ignore_result(g_gcm_support_checker.Get());
 217 }
 218
 219 Aes128Gcm12Decrypter::~Aes128Gcm12Decrypter() {}
 220
 221 void Aes128Gcm12Decrypter::FillAeadParams(StringPiece nonce,
 222                                           const StringPiece& associated_data,
 223                                           size_t auth_tag_size,
 224                                           AeadParams* aead_params) const {
 225   aead_params->len = sizeof(aead_params->data.gcm_params);
 226   CK_GCM_PARAMS* gcm_params = &aead_params->data.gcm_params;
 227   gcm_params->pIv =
 228       reinterpret_cast<CK_BYTE*>(const_cast<char*>(nonce.data()));
 229   gcm_params->ulIvLen = nonce.size();
 230   gcm_params->pAAD =
 231       reinterpret_cast<CK_BYTE*>(const_cast<char*>(associated_data.data()));
 232   gcm_params->ulAADLen = associated_data.size();
 233   gcm_params->ulTagBits = auth_tag_size * 8;
 234 }
 235
 236 }  // namespace net