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 <rpc.h>
   9
  10 #include <list>
  11 #include <string>
  12 #include <vector>
  13
  14 #include "base/base64.h"
  15 #include "base/basictypes.h"
  16 #include "base/logging.h"
  17 #include "base/strings/string_piece.h"
  18 #include "base/strings/string_util.h"
  19 #include "base/strings/utf_string_conversions.h"
  20 #include "crypto/capi_util.h"
  21 #include "crypto/scoped_capi_types.h"
  22 #include "crypto/wincrypt_shim.h"
  23
  24 #pragma comment(lib, "crypt32.lib")
  25 #pragma comment(lib, "rpcrt4.lib")
  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                                   const_cast<char*>(szOID_RSA_RSA), 0, NULL,
  40                                   NULL, &size);
  41   DCHECK(ok);
  42   if (!ok)
  43     return false;
  44
  45   output->resize(size);
  46
  47   PCERT_PUBLIC_KEY_INFO public_key_casted =
  48       reinterpret_cast<PCERT_PUBLIC_KEY_INFO>(&(*output)[0]);
  49   ok = CryptExportPublicKeyInfoEx(prov, AT_KEYEXCHANGE, X509_ASN_ENCODING,
  50                                   const_cast<char*>(szOID_RSA_RSA), 0, NULL,
  51                                   public_key_casted, &size);
  52   DCHECK(ok);
  53   if (!ok)
  54     return false;
  55
  56   output->resize(size);
  57
  58   return true;
  59 }
  60
  61 // Generates a DER encoded SignedPublicKeyAndChallenge structure from the
  62 // signing key of |prov| and the specified ASCII |challenge| string and
  63 // appends it to |output|.
  64 // True if the encoding was successfully generated.
  65 bool GetSignedPublicKeyAndChallenge(HCRYPTPROV prov,
  66                                     const std::string& challenge,
  67                                     std::string* output) {
  68   base::string16 challenge16 = base::ASCIIToUTF16(challenge);
  69   std::vector<BYTE> spki;
  70
  71   if (!GetSubjectPublicKeyInfo(prov, &spki))
  72     return false;
  73
  74   // PublicKeyAndChallenge ::= SEQUENCE {
  75   //     spki SubjectPublicKeyInfo,
  76   //     challenge IA5STRING
  77   // }
  78   CERT_KEYGEN_REQUEST_INFO pkac;
  79   pkac.dwVersion = CERT_KEYGEN_REQUEST_V1;
  80   pkac.SubjectPublicKeyInfo =
  81       *reinterpret_cast<PCERT_PUBLIC_KEY_INFO>(&spki[0]);
  82   pkac.pwszChallengeString = const_cast<base::char16*>(challenge16.c_str());
  83
  84   CRYPT_ALGORITHM_IDENTIFIER sig_alg;
  85   memset(&sig_alg, 0, sizeof(sig_alg));
  86   sig_alg.pszObjId = const_cast<char*>(szOID_RSA_MD5RSA);
  87
  88   BOOL ok;
  89   DWORD size = 0;
  90   std::vector<BYTE> signed_pkac;
  91   ok = CryptSignAndEncodeCertificate(prov, AT_KEYEXCHANGE, X509_ASN_ENCODING,
  92                                      X509_KEYGEN_REQUEST_TO_BE_SIGNED,
  93                                      &pkac, &sig_alg, NULL,
  94                                      NULL, &size);
  95   DCHECK(ok);
  96   if (!ok)
  97     return false;
  98
  99   signed_pkac.resize(size);
 100   ok = CryptSignAndEncodeCertificate(prov, AT_KEYEXCHANGE, X509_ASN_ENCODING,
 101                                      X509_KEYGEN_REQUEST_TO_BE_SIGNED,
 102                                      &pkac, &sig_alg, NULL,
 103                                      &signed_pkac[0], &size);
 104   DCHECK(ok);
 105   if (!ok)
 106     return false;
 107
 108   output->assign(reinterpret_cast<char*>(&signed_pkac[0]), size);
 109   return true;
 110 }
 111
 112 // Generates a unique name for the container which will store the key that is
 113 // generated. The traditional Windows approach is to use a GUID here.
 114 std::wstring GetNewKeyContainerId() {
 115   RPC_STATUS status = RPC_S_OK;
 116   std::wstring result;
 117
 118   UUID id = { 0 };
 119   status = UuidCreateSequential(&id);
 120   if (status != RPC_S_OK && status != RPC_S_UUID_LOCAL_ONLY)
 121     return result;
 122
 123   RPC_WSTR rpc_string = NULL;
 124   status = UuidToString(&id, &rpc_string);
 125   if (status != RPC_S_OK)
 126     return result;
 127
 128   // RPC_WSTR is unsigned short*.  wchar_t is a built-in type of Visual C++,
 129   // so the type cast is necessary.
 130   result.assign(reinterpret_cast<wchar_t*>(rpc_string));
 131   RpcStringFree(&rpc_string);
 132
 133   return result;
 134 }
 135
 136 // This is a helper struct designed to optionally delete a key after releasing
 137 // the associated provider.
 138 struct KeyContainer {
 139  public:
 140   explicit KeyContainer(bool delete_keyset)
 141       : delete_keyset_(delete_keyset) {}
 142
 143   ~KeyContainer() {
 144     if (provider_) {
 145       provider_.reset();
 146       if (delete_keyset_ && !key_id_.empty()) {
 147         HCRYPTPROV provider;
 148         crypto::CryptAcquireContextLocked(&provider, key_id_.c_str(), NULL,
 149             PROV_RSA_FULL, CRYPT_SILENT | CRYPT_DELETEKEYSET);
 150       }
 151     }
 152   }
 153
 154   crypto::ScopedHCRYPTPROV provider_;
 155   std::wstring key_id_;
 156
 157  private:
 158   bool delete_keyset_;
 159 };
 160
 161 std::string KeygenHandler::GenKeyAndSignChallenge() {
 162   KeyContainer key_container(!stores_key_);
 163
 164   // TODO(rsleevi): Have the user choose which provider they should use, which
 165   // needs to be filtered by those providers which can provide the key type
 166   // requested or the key size requested. This is especially important for
 167   // generating certificates that will be stored on smart cards.
 168   const int kMaxAttempts = 5;
 169   int attempt;
 170   for (attempt = 0; attempt < kMaxAttempts; ++attempt) {
 171     // Per MSDN documentation for CryptAcquireContext, if applications will be
 172     // creating their own keys, they should ensure unique naming schemes to
 173     // prevent overlap with any other applications or consumers of CSPs, and
 174     // *should not* store new keys within the default, NULL key container.
 175     key_container.key_id_ = GetNewKeyContainerId();
 176     if (key_container.key_id_.empty())
 177       return std::string();
 178
 179     // Only create new key containers, so that existing key containers are not
 180     // overwritten.
 181     if (crypto::CryptAcquireContextLocked(key_container.provider_.receive(),
 182             key_container.key_id_.c_str(), NULL, PROV_RSA_FULL,
 183             CRYPT_SILENT | CRYPT_NEWKEYSET))
 184       break;
 185
 186     if (GetLastError() != NTE_BAD_KEYSET) {
 187       LOG(ERROR) << "Keygen failed: Couldn't acquire a CryptoAPI provider "
 188                     "context: " << GetLastError();
 189       return std::string();
 190     }
 191   }
 192   if (attempt == kMaxAttempts) {
 193     LOG(ERROR) << "Keygen failed: Couldn't acquire a CryptoAPI provider "
 194                   "context: Max retries exceeded";
 195     return std::string();
 196   }
 197
 198   {
 199     crypto::ScopedHCRYPTKEY key;
 200     if (!CryptGenKey(key_container.provider_, CALG_RSA_KEYX,
 201         (key_size_in_bits_ << 16) | CRYPT_EXPORTABLE, key.receive())) {
 202       LOG(ERROR) << "Keygen failed: Couldn't generate an RSA key";
 203       return std::string();
 204     }
 205
 206     std::string spkac;
 207     if (!GetSignedPublicKeyAndChallenge(key_container.provider_, challenge_,
 208                                         &spkac)) {
 209       LOG(ERROR) << "Keygen failed: Couldn't generate the signed public key "
 210                     "and challenge";
 211       return std::string();
 212     }
 213
 214     std::string result;
 215     base::Base64Encode(spkac, &result);
 216
 217     VLOG(1) << "Keygen succeeded";
 218     return result;
 219   }
 220 }
 221
 222 }  // namespace net