net/base/keygen_handler_win.cc

   1 // Copyright (c) 2011 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/base/keygen_handler.h"
   6
   7 #include <windows.h>
   8 #include <wincrypt.h>
   9 #pragma comment(lib, "crypt32.lib")
  10 #include <rpc.h>
  11 #pragma comment(lib, "rpcrt4.lib")
  12
  13 #include <list>
  14 #include <string>
  15 #include <vector>
  16
  17 #include "base/base64.h"
  18 #include "base/basictypes.h"
  19 #include "base/logging.h"
  20 #include "base/strings/string_piece.h"
  21 #include "base/strings/string_util.h"
  22 #include "base/strings/utf_string_conversions.h"
  23 #include "crypto/capi_util.h"
  24 #include "crypto/scoped_capi_types.h"
  25
  26
  27 namespace net {
  28
  29 // Assigns the contents of a CERT_PUBLIC_KEY_INFO structure for the signing
  30 // key in |prov| to |output|. Returns true if encoding was successful.
  31 bool GetSubjectPublicKeyInfo(HCRYPTPROV prov, std::vector<BYTE>* output) {
  32   BOOL ok;
  33   DWORD size = 0;
  34
  35   // From the private key stored in HCRYPTPROV, obtain the public key, stored
  36   // as a CERT_PUBLIC_KEY_INFO structure. Currently, only RSA public keys are
  37   // supported.
  38   ok = CryptExportPublicKeyInfoEx(prov, AT_KEYEXCHANGE, X509_ASN_ENCODING,
  39                                   szOID_RSA_RSA, 0, NULL, NULL, &size);
  40   DCHECK(ok);
  41   if (!ok)
  42     return false;
  43
  44   output->resize(size);
  45
  46   PCERT_PUBLIC_KEY_INFO public_key_casted =
  47       reinterpret_cast<PCERT_PUBLIC_KEY_INFO>(&(*output)[0]);
  48   ok = CryptExportPublicKeyInfoEx(prov, AT_KEYEXCHANGE, X509_ASN_ENCODING,
  49                                   szOID_RSA_RSA, 0, NULL, public_key_casted,
  50                                   &size);
  51   DCHECK(ok);
  52   if (!ok)
  53     return false;
  54
  55   output->resize(size);
  56
  57   return true;
  58 }
  59
  60 // Generates a DER encoded SignedPublicKeyAndChallenge structure from the
  61 // signing key of |prov| and the specified ASCII |challenge| string and
  62 // appends it to |output|.
  63 // True if the encoding was successfully generated.
  64 bool GetSignedPublicKeyAndChallenge(HCRYPTPROV prov,
  65                                     const std::string& challenge,
  66                                     std::string* output) {
  67   std::wstring wide_challenge = base::ASCIIToWide(challenge);
  68   std::vector<BYTE> spki;
  69
  70   if (!GetSubjectPublicKeyInfo(prov, &spki))
  71     return false;
  72
  73   // PublicKeyAndChallenge ::= SEQUENCE {
  74   //     spki SubjectPublicKeyInfo,
  75   //     challenge IA5STRING
  76   // }
  77   CERT_KEYGEN_REQUEST_INFO pkac;
  78   pkac.dwVersion = CERT_KEYGEN_REQUEST_V1;
  79   pkac.SubjectPublicKeyInfo =
  80       *reinterpret_cast<PCERT_PUBLIC_KEY_INFO>(&spki[0]);
  81   pkac.pwszChallengeString = const_cast<wchar_t*>(wide_challenge.c_str());
  82
  83   CRYPT_ALGORITHM_IDENTIFIER sig_alg;
  84   memset(&sig_alg, 0, sizeof(sig_alg));
  85   sig_alg.pszObjId = szOID_RSA_MD5RSA;
  86
  87   BOOL ok;
  88   DWORD size = 0;
  89   std::vector<BYTE> signed_pkac;
  90   ok = CryptSignAndEncodeCertificate(prov, AT_KEYEXCHANGE, X509_ASN_ENCODING,
  91                                      X509_KEYGEN_REQUEST_TO_BE_SIGNED,
  92                                      &pkac, &sig_alg, NULL,
  93                                      NULL, &size);
  94   DCHECK(ok);
  95   if (!ok)
  96     return false;
  97
  98   signed_pkac.resize(size);
  99   ok = CryptSignAndEncodeCertificate(prov, AT_KEYEXCHANGE, X509_ASN_ENCODING,
 100                                      X509_KEYGEN_REQUEST_TO_BE_SIGNED,
 101                                      &pkac, &sig_alg, NULL,
 102                                      &signed_pkac[0], &size);
 103   DCHECK(ok);
 104   if (!ok)
 105     return false;
 106
 107   output->assign(reinterpret_cast<char*>(&signed_pkac[0]), size);
 108   return true;
 109 }
 110
 111 // Generates a unique name for the container which will store the key that is
 112 // generated. The traditional Windows approach is to use a GUID here.
 113 std::wstring GetNewKeyContainerId() {
 114   RPC_STATUS status = RPC_S_OK;
 115   std::wstring result;
 116
 117   UUID id = { 0 };
 118   status = UuidCreateSequential(&id);
 119   if (status != RPC_S_OK && status != RPC_S_UUID_LOCAL_ONLY)
 120     return result;
 121
 122   RPC_WSTR rpc_string = NULL;
 123   status = UuidToString(&id, &rpc_string);
 124   if (status != RPC_S_OK)
 125     return result;
 126
 127   // RPC_WSTR is unsigned short*.  wchar_t is a built-in type of Visual C++,
 128   // so the type cast is necessary.
 129   result.assign(reinterpret_cast<wchar_t*>(rpc_string));
 130   RpcStringFree(&rpc_string);
 131
 132   return result;
 133 }
 134
 135 // This is a helper struct designed to optionally delete a key after releasing
 136 // the associated provider.
 137 struct KeyContainer {
 138  public:
 139   explicit KeyContainer(bool delete_keyset)
 140       : delete_keyset_(delete_keyset) {}
 141
 142   ~KeyContainer() {
 143     if (provider_) {
 144       provider_.reset();
 145       if (delete_keyset_ && !key_id_.empty()) {
 146         HCRYPTPROV provider;
 147         crypto::CryptAcquireContextLocked(&provider, key_id_.c_str(), NULL,
 148             PROV_RSA_FULL, CRYPT_SILENT | CRYPT_DELETEKEYSET);
 149       }
 150     }
 151   }
 152
 153   crypto::ScopedHCRYPTPROV provider_;
 154   std::wstring key_id_;
 155
 156  private:
 157   bool delete_keyset_;
 158 };
 159
 160 std::string KeygenHandler::GenKeyAndSignChallenge() {
 161   KeyContainer key_container(!stores_key_);
 162
 163   // TODO(rsleevi): Have the user choose which provider they should use, which
 164   // needs to be filtered by those providers which can provide the key type
 165   // requested or the key size requested. This is especially important for
 166   // generating certificates that will be stored on smart cards.
 167   const int kMaxAttempts = 5;
 168   int attempt;
 169   for (attempt = 0; attempt < kMaxAttempts; ++attempt) {
 170     // Per MSDN documentation for CryptAcquireContext, if applications will be
 171     // creating their own keys, they should ensure unique naming schemes to
 172     // prevent overlap with any other applications or consumers of CSPs, and
 173     // *should not* store new keys within the default, NULL key container.
 174     key_container.key_id_ = GetNewKeyContainerId();
 175     if (key_container.key_id_.empty())
 176       return std::string();
 177
 178     // Only create new key containers, so that existing key containers are not
 179     // overwritten.
 180     if (crypto::CryptAcquireContextLocked(key_container.provider_.receive(),
 181             key_container.key_id_.c_str(), NULL, PROV_RSA_FULL,
 182             CRYPT_SILENT | CRYPT_NEWKEYSET))
 183       break;
 184
 185     if (GetLastError() != NTE_BAD_KEYSET) {
 186       LOG(ERROR) << "Keygen failed: Couldn't acquire a CryptoAPI provider "
 187                     "context: " << GetLastError();
 188       return std::string();
 189     }
 190   }
 191   if (attempt == kMaxAttempts) {
 192     LOG(ERROR) << "Keygen failed: Couldn't acquire a CryptoAPI provider "
 193                   "context: Max retries exceeded";
 194     return std::string();
 195   }
 196
 197   {
 198     crypto::ScopedHCRYPTKEY key;
 199     if (!CryptGenKey(key_container.provider_, CALG_RSA_KEYX,
 200         (key_size_in_bits_ << 16) | CRYPT_EXPORTABLE, key.receive())) {
 201       LOG(ERROR) << "Keygen failed: Couldn't generate an RSA key";
 202       return std::string();
 203     }
 204
 205     std::string spkac;
 206     if (!GetSignedPublicKeyAndChallenge(key_container.provider_, challenge_,
 207                                         &spkac)) {
 208       LOG(ERROR) << "Keygen failed: Couldn't generate the signed public key "
 209                     "and challenge";
 210       return std::string();
 211     }
 212
 213     std::string result;
 214     base::Base64Encode(spkac, &result);
 215
 216     VLOG(1) << "Keygen succeeded";
 217     return result;
 218   }
 219 }
 220
 221 }  // namespace net