net/cert/sha256_legacy_support_openssl_win.cc

   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.
   4
   5 #include <openssl/asn1.h>
   6 #include <openssl/bytestring.h>
   7 #include <openssl/evp.h>
   8 #include <openssl/obj.h>
   9 #include <openssl/x509.h>
  10
  11 #include "base/logging.h"
  12 #include "crypto/scoped_openssl_types.h"
  13 #include "net/cert/sha256_legacy_support_win.h"
  14
  15 namespace net {
  16
  17 namespace sha256_interception {
  18
  19 namespace {
  20
  21 using ScopedX509_ALGOR = crypto::ScopedOpenSSL<X509_ALGOR, X509_ALGOR_free>;
  22
  23 // Parses |subject_signature| and writes the components into |*out_tbs_data|,
  24 // |*out_algor|, and |*out_signature|. The BIT STRING in the signature must be
  25 // a multiple of 8 bits. |*out_signature| will have the padding byte removed.
  26 // It returns true on success and false on failure.
  27 bool ParseSubjectSignature(const base::StringPiece& subject_signature,
  28                            CBS* out_tbs_data,
  29                            ScopedX509_ALGOR* out_algor,
  30                            CBS* out_signature) {
  31   CBS cbs, sequence, tbs_data, algorithm, signature;
  32   CBS_init(&cbs, reinterpret_cast<const uint8_t*>(subject_signature.data()),
  33            subject_signature.size());
  34   if (!CBS_get_asn1(&cbs, &sequence, CBS_ASN1_SEQUENCE) ||
  35       CBS_len(&cbs) != 0 ||
  36       !CBS_get_any_asn1_element(&sequence, &tbs_data, nullptr, nullptr) ||
  37       !CBS_get_asn1_element(&sequence, &algorithm,
  38                             CBS_ASN1_SEQUENCE) ||
  39       !CBS_get_asn1(&sequence, &signature, CBS_ASN1_BITSTRING) ||
  40       CBS_len(&sequence) != 0) {
  41     return false;
  42   }
  43
  44   // Decode the algorithm.
  45   const uint8_t* ptr = CBS_data(&algorithm);
  46   ScopedX509_ALGOR algor(d2i_X509_ALGOR(NULL, &ptr, CBS_len(&algorithm)));
  47   if (!algor || ptr != CBS_data(&algorithm) + CBS_len(&algorithm))
  48     return false;
  49
  50   // An ASN.1 BIT STRING is encoded with a leading byte denoting the number of
  51   // padding bits. All supported signature algorithms output octets, so the
  52   // leading byte must be zero.
  53   uint8_t padding;
  54   if (!CBS_get_u8(&signature, &padding) || padding != 0)
  55     return false;
  56
  57   *out_tbs_data = tbs_data;
  58   *out_algor = algor.Pass();
  59   *out_signature = signature;
  60   return true;
  61 }
  62
  63 }  // namespace
  64
  65 BOOL CryptVerifyCertificateSignatureExHook(
  66     CryptVerifyCertificateSignatureExFunc original_func,
  67     HCRYPTPROV_LEGACY provider,
  68     DWORD encoding_type,
  69     DWORD subject_type,
  70     void* subject_data,
  71     DWORD issuer_type,
  72     void* issuer_data,
  73     DWORD flags,
  74     void* extra) {
  75   CHECK(original_func);
  76
  77   // Only intercept if the arguments are supported.
  78   if (provider != NULL || (encoding_type != X509_ASN_ENCODING) ||
  79       !IsSupportedSubjectType(subject_type) || subject_data == NULL ||
  80       !IsSupportedIssuerType(issuer_type) || issuer_data == NULL) {
  81     return original_func(provider, encoding_type, subject_type, subject_data,
  82                          issuer_type, issuer_data, flags, extra);
  83   }
  84
  85   base::StringPiece subject_signature =
  86       GetSubjectSignature(subject_type, subject_data);
  87   bool should_intercept = false;
  88
  89   // Parse out the data, AlgorithmIdentifier, and signature.
  90   CBS tbs_data, signature;
  91   ScopedX509_ALGOR algor;
  92   if (ParseSubjectSignature(subject_signature, &tbs_data, &algor,
  93                             &signature)) {
  94     // If the signature algorithm is RSA with one of the SHA-2 algorithms
  95     // supported by BoringSSL (excluding SHA-224, which is pointless), then
  96     // defer to the BoringSSL implementation. Otherwise, fall back and let the
  97     // OS handle it (e.g. in case there are any algorithm policies in effect).
  98     int nid = OBJ_obj2nid(algor->algorithm);
  99     if (nid == NID_sha256WithRSAEncryption ||
 100         nid == NID_sha384WithRSAEncryption ||
 101         nid == NID_sha512WithRSAEncryption) {
 102       should_intercept = true;
 103     }
 104   }
 105
 106   if (!should_intercept) {
 107     return original_func(provider, encoding_type, subject_type, subject_data,
 108                          issuer_type, issuer_data, flags, extra);
 109   }
 110
 111   // Rather than attempting to synthesize an EVP_PKEY by hand, just force the
 112   // OS to do an ASN.1 encoding and then decode it back into BoringSSL. This
 113   // is silly for performance, but safest for consistency.
 114   PCERT_PUBLIC_KEY_INFO issuer_public_key =
 115       GetIssuerPublicKey(issuer_type, issuer_data);
 116   if (!issuer_public_key) {
 117     SetLastError(static_cast<DWORD>(NTE_BAD_ALGID));
 118     return FALSE;
 119   }
 120
 121   uint8_t* issuer_spki_data = NULL;
 122   DWORD issuer_spki_len = 0;
 123   if (!CryptEncodeObjectEx(X509_ASN_ENCODING, X509_PUBLIC_KEY_INFO,
 124                            issuer_public_key, CRYPT_ENCODE_ALLOC_FLAG, NULL,
 125                            &issuer_spki_data, &issuer_spki_len)) {
 126     return FALSE;
 127   }
 128
 129   const uint8_t* ptr = issuer_spki_data;
 130   crypto::ScopedEVP_PKEY pubkey(d2i_PUBKEY(NULL, &ptr, issuer_spki_len));
 131   if (!pubkey.get() || ptr != issuer_spki_data + issuer_spki_len) {
 132     ::LocalFree(issuer_spki_data);
 133     SetLastError(static_cast<DWORD>(NTE_BAD_ALGID));
 134     return FALSE;
 135   }
 136   ::LocalFree(issuer_spki_data);
 137
 138   crypto::ScopedEVP_MD_CTX md_ctx(EVP_MD_CTX_create());
 139   if (!EVP_DigestVerifyInitFromAlgorithm(md_ctx.get(), algor.get(),
 140                                          pubkey.get()) ||
 141       !EVP_DigestVerifyUpdate(md_ctx.get(), CBS_data(&tbs_data),
 142                               CBS_len(&tbs_data)) ||
 143       !EVP_DigestVerifyFinal(md_ctx.get(), CBS_data(&signature),
 144                             CBS_len(&signature))) {
 145     SetLastError(static_cast<DWORD>(NTE_BAD_SIGNATURE));
 146     return FALSE;
 147   }
 148   return TRUE;
 149 }
 150
 151 }  // namespace sha256_interception
 152
 153 }  // namespace net