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 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 std::wstring wide_challenge = base::ASCIIToWide(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<wchar_t*>(wide_challenge.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 223
