Coverage Report

Created: 2022-06-23 06:44

/src/botan/src/lib/tls/tls12/msg_client_kex.cpp
Line
Count
Source (jump to first uncovered line)
1
/*
2
* Client Key Exchange Message
3
* (C) 2004-2010,2016 Jack Lloyd
4
*     2017 Harry Reimann, Rohde & Schwarz Cybersecurity
5
*
6
* Botan is released under the Simplified BSD License (see license.txt)
7
*/
8
9
#include <botan/tls_messages.h>
10
#include <botan/tls_extensions.h>
11
#include <botan/rng.h>
12
13
#include <botan/internal/tls_reader.h>
14
#include <botan/internal/tls_handshake_io.h>
15
#include <botan/internal/tls_handshake_state.h>
16
#include <botan/internal/tls_handshake_hash.h>
17
#include <botan/credentials_manager.h>
18
#include <botan/internal/ct_utils.h>
19
20
#include <botan/rsa.h>
21
22
#if defined(BOTAN_HAS_CECPQ1)
23
  #include <botan/cecpq1.h>
24
#endif
25
26
namespace Botan::TLS {
27
28
/*
29
* Create a new Client Key Exchange message
30
*/
31
Client_Key_Exchange::Client_Key_Exchange(Handshake_IO& io,
32
                                         Handshake_State& state,
33
                                         const Policy& policy,
34
                                         Credentials_Manager& creds,
35
                                         const Public_Key* server_public_key,
36
                                         const std::string& hostname,
37
                                         RandomNumberGenerator& rng)
38
0
   {
39
0
   const Kex_Algo kex_algo = state.ciphersuite().kex_method();
40
41
0
   if(kex_algo == Kex_Algo::PSK)
42
0
      {
43
0
      std::string identity_hint = "";
44
45
0
      if(state.server_kex())
46
0
         {
47
0
         TLS_Data_Reader reader("ClientKeyExchange", state.server_kex()->params());
48
0
         identity_hint = reader.get_string(2, 0, 65535);
49
0
         }
50
51
0
      const std::string psk_identity =
52
0
         creds.psk_identity("tls-client", hostname, identity_hint);
53
54
0
      append_tls_length_value(m_key_material, psk_identity, 2);
55
56
0
      SymmetricKey psk = creds.psk("tls-client", hostname, psk_identity);
57
58
0
      std::vector<uint8_t> zeros(psk.length());
59
60
0
      append_tls_length_value(m_pre_master, zeros, 2);
61
0
      append_tls_length_value(m_pre_master, psk.bits_of(), 2);
62
0
      }
63
0
   else if(state.server_kex())
64
0
      {
65
0
      TLS_Data_Reader reader("ClientKeyExchange", state.server_kex()->params());
66
67
0
      SymmetricKey psk;
68
69
0
      if(kex_algo == Kex_Algo::ECDHE_PSK)
70
0
         {
71
0
         std::string identity_hint = reader.get_string(2, 0, 65535);
72
73
0
         const std::string psk_identity =
74
0
            creds.psk_identity("tls-client", hostname, identity_hint);
75
76
0
         append_tls_length_value(m_key_material, psk_identity, 2);
77
78
0
         psk = creds.psk("tls-client", hostname, psk_identity);
79
0
         }
80
81
0
      if(kex_algo == Kex_Algo::DH)
82
0
         {
83
0
         const std::vector<uint8_t> modulus = reader.get_range<uint8_t>(2, 1, 65535);
84
0
         const std::vector<uint8_t> generator = reader.get_range<uint8_t>(2, 1, 65535);
85
0
         const std::vector<uint8_t> peer_public_value = reader.get_range<uint8_t>(2, 1, 65535);
86
87
0
         if(reader.remaining_bytes())
88
0
            throw Decoding_Error("Bad params size for DH key exchange");
89
90
0
         const std::pair<secure_vector<uint8_t>, std::vector<uint8_t>> dh_result =
91
0
            state.callbacks().tls_dh_agree(modulus, generator, peer_public_value, policy, rng);
92
93
0
         if(kex_algo == Kex_Algo::DH)
94
0
            m_pre_master = dh_result.first;
95
0
         else
96
0
            {
97
0
            append_tls_length_value(m_pre_master, dh_result.first, 2);
98
0
            append_tls_length_value(m_pre_master, psk.bits_of(), 2);
99
0
            }
100
101
0
         append_tls_length_value(m_key_material, dh_result.second, 2);
102
0
         }
103
0
      else if(kex_algo == Kex_Algo::ECDH ||
104
0
              kex_algo == Kex_Algo::ECDHE_PSK)
105
0
         {
106
0
         const uint8_t curve_type = reader.get_byte();
107
0
         if(curve_type != 3)
108
0
            throw Decoding_Error("Server sent non-named ECC curve");
109
110
0
         const Group_Params curve_id = static_cast<Group_Params>(reader.get_uint16_t());
111
0
         const std::vector<uint8_t> peer_public_value = reader.get_range<uint8_t>(1, 1, 255);
112
113
0
         if(policy.choose_key_exchange_group({curve_id}) != curve_id)
114
0
            {
115
0
            throw TLS_Exception(Alert::HANDSHAKE_FAILURE,
116
0
                                "Server sent ECC curve prohibited by policy");
117
0
            }
118
119
0
         const std::string curve_name = state.callbacks().tls_decode_group_param(curve_id);
120
121
0
         if(curve_name.empty())
122
0
            throw Decoding_Error("Server sent unknown named curve " +
123
0
                                 std::to_string(static_cast<uint16_t>(curve_id)));
124
125
0
         const std::pair<secure_vector<uint8_t>, std::vector<uint8_t>> ecdh_result =
126
0
            state.callbacks().tls_ecdh_agree(curve_name, peer_public_value, policy, rng,
127
0
                                             state.server_hello()->prefers_compressed_ec_points());
128
129
0
         if(kex_algo == Kex_Algo::ECDH)
130
0
            {
131
0
            m_pre_master = ecdh_result.first;
132
0
            }
133
0
         else
134
0
            {
135
0
            append_tls_length_value(m_pre_master, ecdh_result.first, 2);
136
0
            append_tls_length_value(m_pre_master, psk.bits_of(), 2);
137
0
            }
138
139
0
         append_tls_length_value(m_key_material, ecdh_result.second, 1);
140
0
         }
141
0
#if defined(BOTAN_HAS_CECPQ1)
142
0
      else if(kex_algo == Kex_Algo::CECPQ1)
143
0
         {
144
0
         const std::vector<uint8_t> cecpq1_offer = reader.get_range<uint8_t>(2, 1, 65535);
145
146
0
         if(cecpq1_offer.size() != CECPQ1_OFFER_BYTES)
147
0
            throw TLS_Exception(Alert::HANDSHAKE_FAILURE, "Invalid CECPQ1 key size");
148
149
0
         std::vector<uint8_t> newhope_accept(CECPQ1_ACCEPT_BYTES);
150
0
         secure_vector<uint8_t> shared_secret(CECPQ1_SHARED_KEY_BYTES);
151
0
         CECPQ1_accept(shared_secret.data(), newhope_accept.data(), cecpq1_offer.data(), rng);
152
0
         append_tls_length_value(m_key_material, newhope_accept, 2);
153
0
         m_pre_master = shared_secret;
154
0
         }
155
0
#endif
156
0
      else
157
0
         {
158
0
         throw Internal_Error("Client_Key_Exchange: Unknown key exchange method was negotiated");
159
0
         }
160
161
0
      reader.assert_done();
162
0
      }
163
0
   else
164
0
      {
165
      // No server key exchange msg better mean RSA kex + RSA key in cert
166
167
0
      if(kex_algo != Kex_Algo::STATIC_RSA)
168
0
         throw Unexpected_Message("No server kex message, but negotiated a key exchange that required it");
169
170
0
      if(!server_public_key)
171
0
         throw Internal_Error("No server public key for RSA exchange");
172
173
0
      if(auto rsa_pub = dynamic_cast<const RSA_PublicKey*>(server_public_key))
174
0
         {
175
0
         const Protocol_Version offered_version = state.client_hello()->legacy_version();
176
177
0
         rng.random_vec(m_pre_master, 48);
178
0
         m_pre_master[0] = offered_version.major_version();
179
0
         m_pre_master[1] = offered_version.minor_version();
180
181
0
         PK_Encryptor_EME encryptor(*rsa_pub, rng, "PKCS1v15");
182
183
0
         const std::vector<uint8_t> encrypted_key = encryptor.encrypt(m_pre_master, rng);
184
185
0
         append_tls_length_value(m_key_material, encrypted_key, 2);
186
0
         }
187
0
      else
188
0
         throw TLS_Exception(Alert::HANDSHAKE_FAILURE,
189
0
                             "Expected a RSA key in server cert but got " +
190
0
                             server_public_key->algo_name());
191
0
      }
192
193
0
   state.hash().update(io.send(*this));
194
0
   }
195
196
/*
197
* Read a Client Key Exchange message
198
*/
199
Client_Key_Exchange::Client_Key_Exchange(const std::vector<uint8_t>& contents,
200
                                         const Handshake_State& state,
201
                                         const Private_Key* server_rsa_kex_key,
202
                                         Credentials_Manager& creds,
203
                                         const Policy& policy,
204
                                         RandomNumberGenerator& rng)
205
14.1k
   {
206
14.1k
   const Kex_Algo kex_algo = state.ciphersuite().kex_method();
207
208
14.1k
   if(kex_algo == Kex_Algo::STATIC_RSA)
209
0
      {
210
0
      BOTAN_ASSERT(state.server_certs() && !state.server_certs()->cert_chain().empty(),
211
0
                   "RSA key exchange negotiated so server sent a certificate");
212
213
0
      if(!server_rsa_kex_key)
214
0
         throw Internal_Error("Expected RSA kex but no server kex key set");
215
216
0
      if(server_rsa_kex_key->algo_name() != "RSA")
217
0
         throw Internal_Error("Expected RSA key but got " + server_rsa_kex_key->algo_name());
218
219
0
      TLS_Data_Reader reader("ClientKeyExchange", contents);
220
0
      const std::vector<uint8_t> encrypted_pre_master = reader.get_range<uint8_t>(2, 0, 65535);
221
0
      reader.assert_done();
222
223
0
      PK_Decryptor_EME decryptor(*server_rsa_kex_key, rng, "PKCS1v15");
224
225
0
      const uint8_t client_major = state.client_hello()->legacy_version().major_version();
226
0
      const uint8_t client_minor = state.client_hello()->legacy_version().minor_version();
227
228
      /*
229
      * PK_Decryptor::decrypt_or_random will return a random value if
230
      * either the length does not match the expected value or if the
231
      * version number embedded in the PMS does not match the one sent
232
      * in the client hello.
233
      */
234
0
      const size_t expected_plaintext_size = 48;
235
0
      const size_t expected_content_size = 2;
236
0
      const uint8_t expected_content_bytes[expected_content_size] = { client_major, client_minor };
237
0
      const uint8_t expected_content_pos[expected_content_size] = { 0, 1 };
238
239
0
      m_pre_master =
240
0
         decryptor.decrypt_or_random(encrypted_pre_master.data(),
241
0
                                     encrypted_pre_master.size(),
242
0
                                     expected_plaintext_size,
243
0
                                     rng,
244
0
                                     expected_content_bytes,
245
0
                                     expected_content_pos,
246
0
                                     expected_content_size);
247
0
      }
248
14.1k
   else
249
14.1k
      {
250
14.1k
      TLS_Data_Reader reader("ClientKeyExchange", contents);
251
252
14.1k
      SymmetricKey psk;
253
254
14.1k
      if(key_exchange_is_psk(kex_algo))
255
14.1k
         {
256
14.1k
         const std::string psk_identity = reader.get_string(2, 0, 65535);
257
258
14.1k
         psk = creds.psk("tls-server",
259
14.1k
                         state.client_hello()->sni_hostname(),
260
14.1k
                         psk_identity);
261
262
14.1k
         if(psk.length() == 0)
263
0
            {
264
0
            if(policy.hide_unknown_users())
265
0
               psk = SymmetricKey(rng, 16);
266
0
            else
267
0
               throw TLS_Exception(Alert::UNKNOWN_PSK_IDENTITY,
268
0
                                   "No PSK for identifier " + psk_identity);
269
0
            }
270
14.1k
         }
271
272
14.1k
      if(kex_algo == Kex_Algo::PSK)
273
460
         {
274
460
         std::vector<uint8_t> zeros(psk.length());
275
460
         append_tls_length_value(m_pre_master, zeros, 2);
276
460
         append_tls_length_value(m_pre_master, psk.bits_of(), 2);
277
460
         }
278
13.6k
#if defined(BOTAN_HAS_CECPQ1)
279
13.6k
      else if(kex_algo == Kex_Algo::CECPQ1)
280
0
         {
281
0
         const CECPQ1_key& cecpq1_offer = state.server_kex()->cecpq1_key();
282
283
0
         const std::vector<uint8_t> cecpq1_accept = reader.get_range<uint8_t>(2, 0, 65535);
284
0
         if(cecpq1_accept.size() != CECPQ1_ACCEPT_BYTES)
285
0
            throw Decoding_Error("Invalid size for CECPQ1 accept message");
286
287
0
         m_pre_master.resize(CECPQ1_SHARED_KEY_BYTES);
288
0
         CECPQ1_finish(m_pre_master.data(), cecpq1_offer, cecpq1_accept.data());
289
0
         }
290
13.6k
#endif
291
13.6k
      else if(kex_algo == Kex_Algo::DH ||
292
13.6k
              kex_algo == Kex_Algo::ECDH ||
293
13.6k
              kex_algo == Kex_Algo::ECDHE_PSK)
294
13.6k
         {
295
13.6k
         const Private_Key& private_key = state.server_kex()->server_kex_key();
296
297
13.6k
         const PK_Key_Agreement_Key* ka_key =
298
13.6k
            dynamic_cast<const PK_Key_Agreement_Key*>(&private_key);
299
300
13.6k
         if(!ka_key)
301
0
            throw Internal_Error("Expected key agreement key type but got " +
302
0
                                 private_key.algo_name());
303
304
13.6k
         std::vector<uint8_t> client_pubkey;
305
306
13.6k
         if(ka_key->algo_name() == "DH")
307
0
            {
308
0
            client_pubkey = reader.get_range<uint8_t>(2, 0, 65535);
309
0
            }
310
13.6k
         else
311
13.6k
            {
312
13.6k
            client_pubkey = reader.get_range<uint8_t>(1, 1, 255);
313
13.6k
            }
314
315
13.6k
         try
316
13.6k
            {
317
13.6k
            PK_Key_Agreement ka(*ka_key, rng, "Raw");
318
319
13.6k
            secure_vector<uint8_t> shared_secret = ka.derive_key(0, client_pubkey).bits_of();
320
321
13.6k
            if(ka_key->algo_name() == "DH")
322
0
               shared_secret = CT::strip_leading_zeros(shared_secret);
323
324
13.6k
            if(kex_algo == Kex_Algo::ECDHE_PSK)
325
6.95k
               {
326
6.95k
               append_tls_length_value(m_pre_master, shared_secret, 2);
327
6.95k
               append_tls_length_value(m_pre_master, psk.bits_of(), 2);
328
6.95k
               }
329
6.71k
            else
330
6.71k
               m_pre_master = shared_secret;
331
13.6k
            }
332
13.6k
         catch(Invalid_Argument& e)
333
13.6k
            {
334
127
            throw TLS_Exception(Alert::ILLEGAL_PARAMETER, e.what());
335
127
            }
336
13.6k
         catch(std::exception&)
337
13.6k
            {
338
            /*
339
            * Something failed in the DH/ECDH computation. To avoid possible
340
            * attacks which are based on triggering and detecting some edge
341
            * failure condition, randomize the pre-master output and carry on,
342
            * allowing the protocol to fail later in the finished checks.
343
            */
344
6.58k
            rng.random_vec(m_pre_master, ka_key->public_value().size());
345
6.58k
            }
346
347
13.5k
         reader.assert_done();
348
13.5k
         }
349
5
      else
350
5
         throw Internal_Error("Client_Key_Exchange: Unknown key exchange negotiated");
351
14.1k
      }
352
14.1k
   }
353
354
}