net/cert/ct_log_verifier_openssl.cc

   1 // Copyright 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/cert/ct_log_verifier.h"
   6
   7 #include <openssl/evp.h>
   8 #include <openssl/x509.h>
   9
  10 #include "base/logging.h"
  11 #include "crypto/openssl_util.h"
  12 #include "crypto/scoped_openssl_types.h"
  13 #include "crypto/sha2.h"
  14 #include "net/cert/signed_tree_head.h"
  15
  16 namespace net {
  17
  18 namespace {
  19
  20 const EVP_MD* GetEvpAlg(ct::DigitallySigned::HashAlgorithm alg) {
  21   switch (alg) {
  22     case ct::DigitallySigned::HASH_ALGO_MD5:
  23       return EVP_md5();
  24     case ct::DigitallySigned::HASH_ALGO_SHA1:
  25       return EVP_sha1();
  26     case ct::DigitallySigned::HASH_ALGO_SHA224:
  27       return EVP_sha224();
  28     case ct::DigitallySigned::HASH_ALGO_SHA256:
  29       return EVP_sha256();
  30     case ct::DigitallySigned::HASH_ALGO_SHA384:
  31       return EVP_sha384();
  32     case ct::DigitallySigned::HASH_ALGO_SHA512:
  33       return EVP_sha512();
  34     case ct::DigitallySigned::HASH_ALGO_NONE:
  35     default:
  36       NOTREACHED();
  37       return NULL;
  38   }
  39 }
  40
  41 }  // namespace
  42
  43 CTLogVerifier::~CTLogVerifier() {
  44   crypto::OpenSSLErrStackTracer err_tracer(FROM_HERE);
  45
  46   if (public_key_)
  47     EVP_PKEY_free(public_key_);
  48 }
  49
  50 CTLogVerifier::CTLogVerifier()
  51     : hash_algorithm_(ct::DigitallySigned::HASH_ALGO_NONE),
  52       signature_algorithm_(ct::DigitallySigned::SIG_ALGO_ANONYMOUS),
  53       public_key_(NULL) {}
  54
  55 bool CTLogVerifier::Init(const base::StringPiece& public_key,
  56                          const base::StringPiece& description) {
  57   crypto::OpenSSLErrStackTracer err_tracer(FROM_HERE);
  58
  59   crypto::ScopedBIO bio(
  60       BIO_new_mem_buf(const_cast<char*>(public_key.data()), public_key.size()));
  61   if (!bio.get())
  62     return false;
  63
  64   public_key_ = d2i_PUBKEY_bio(bio.get(), NULL);
  65   if (!public_key_)
  66     return false;
  67
  68   key_id_ = crypto::SHA256HashString(public_key);
  69   description_ = description.as_string();
  70
  71   // Right now, only RSASSA-PKCS1v15 with SHA-256 and ECDSA with SHA-256 are
  72   // supported.
  73   switch (EVP_PKEY_type(public_key_->type)) {
  74     case EVP_PKEY_RSA:
  75       hash_algorithm_ = ct::DigitallySigned::HASH_ALGO_SHA256;
  76       signature_algorithm_ = ct::DigitallySigned::SIG_ALGO_RSA;
  77       break;
  78     case EVP_PKEY_EC:
  79       hash_algorithm_ = ct::DigitallySigned::HASH_ALGO_SHA256;
  80       signature_algorithm_ = ct::DigitallySigned::SIG_ALGO_ECDSA;
  81       break;
  82     default:
  83       DVLOG(1) << "Unsupported key type: " << EVP_PKEY_type(public_key_->type);
  84       return false;
  85   }
  86
  87   // Extra sanity check: Require RSA keys of at least 2048 bits.
  88   // EVP_PKEY_size returns the size in bytes. 256 = 2048-bit RSA key.
  89   if (signature_algorithm_ == ct::DigitallySigned::SIG_ALGO_RSA &&
  90       EVP_PKEY_size(public_key_) < 256) {
  91     DVLOG(1) << "Too small a public key.";
  92     return false;
  93   }
  94
  95   return true;
  96 }
  97
  98 bool CTLogVerifier::VerifySignature(const base::StringPiece& data_to_sign,
  99                                     const base::StringPiece& signature) {
 100   crypto::OpenSSLErrStackTracer err_tracer(FROM_HERE);
 101
 102   const EVP_MD* hash_alg = GetEvpAlg(hash_algorithm_);
 103   if (hash_alg == NULL)
 104     return false;
 105
 106   EVP_MD_CTX ctx;
 107   EVP_MD_CTX_init(&ctx);
 108
 109   bool ok = (
 110       1 == EVP_DigestVerifyInit(&ctx, NULL, hash_alg, NULL, public_key_) &&
 111       1 == EVP_DigestVerifyUpdate(
 112           &ctx, data_to_sign.data(), data_to_sign.size()) &&
 113       1 == EVP_DigestVerifyFinal(
 114           &ctx,
 115           reinterpret_cast<const uint8_t*>(signature.data()),
 116           signature.size()));
 117
 118   EVP_MD_CTX_cleanup(&ctx);
 119   return ok;
 120 }
 121
 122 }  // namespace net