Botan  2.7.0
Crypto and TLS for C++11
msg_client_kex.cpp
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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 #if defined(BOTAN_HAS_SRP6)
27  #include <botan/srp6.h>
28 #endif
29 
30 namespace Botan {
31 
32 namespace TLS {
33 
34 /*
35 * Create a new Client Key Exchange message
36 */
38  Handshake_State& state,
39  const Policy& policy,
40  Credentials_Manager& creds,
42  const std::string& hostname,
44  {
45  const Kex_Algo kex_algo = state.ciphersuite().kex_method();
46 
47  if(kex_algo == Kex_Algo::PSK)
48  {
49  std::string identity_hint = "";
50 
51  if(state.server_kex())
52  {
53  TLS_Data_Reader reader("ClientKeyExchange", state.server_kex()->params());
54  identity_hint = reader.get_string(2, 0, 65535);
55  }
56 
57  const std::string psk_identity =
58  creds.psk_identity("tls-client", hostname, identity_hint);
59 
60  append_tls_length_value(m_key_material, psk_identity, 2);
61 
62  SymmetricKey psk = creds.psk("tls-client", hostname, psk_identity);
63 
64  std::vector<uint8_t> zeros(psk.length());
65 
66  append_tls_length_value(m_pre_master, zeros, 2);
67  append_tls_length_value(m_pre_master, psk.bits_of(), 2);
68  }
69  else if(state.server_kex())
70  {
71  TLS_Data_Reader reader("ClientKeyExchange", state.server_kex()->params());
72 
73  SymmetricKey psk;
74 
75  if(kex_algo == Kex_Algo::DHE_PSK ||
76  kex_algo == Kex_Algo::ECDHE_PSK)
77  {
78  std::string identity_hint = reader.get_string(2, 0, 65535);
79 
80  const std::string psk_identity =
81  creds.psk_identity("tls-client", hostname, identity_hint);
82 
83  append_tls_length_value(m_key_material, psk_identity, 2);
84 
85  psk = creds.psk("tls-client", hostname, psk_identity);
86  }
87 
88  if(kex_algo == Kex_Algo::DH ||
89  kex_algo == Kex_Algo::DHE_PSK)
90  {
91  const std::vector<uint8_t> modulus = reader.get_range<uint8_t>(2, 1, 65535);
92  const std::vector<uint8_t> generator = reader.get_range<uint8_t>(2, 1, 65535);
93  const std::vector<uint8_t> peer_public_value = reader.get_range<uint8_t>(2, 1, 65535);
94 
95  if(reader.remaining_bytes())
96  throw Decoding_Error("Bad params size for DH key exchange");
97 
98  const std::pair<secure_vector<uint8_t>, std::vector<uint8_t>> dh_result =
99  state.callbacks().tls_dh_agree(modulus, generator, peer_public_value, policy, rng);
100 
101  if(kex_algo == Kex_Algo::DH)
102  m_pre_master = dh_result.first;
103  else
104  {
105  append_tls_length_value(m_pre_master, dh_result.first, 2);
106  append_tls_length_value(m_pre_master, psk.bits_of(), 2);
107  }
108 
109  append_tls_length_value(m_key_material, dh_result.second, 2);
110  }
111  else if(kex_algo == Kex_Algo::ECDH ||
112  kex_algo == Kex_Algo::ECDHE_PSK)
113  {
114  const uint8_t curve_type = reader.get_byte();
115  if(curve_type != 3)
116  throw Decoding_Error("Server sent non-named ECC curve");
117 
118  const Group_Params curve_id = static_cast<Group_Params>(reader.get_uint16_t());
119  const std::vector<uint8_t> peer_public_value = reader.get_range<uint8_t>(1, 1, 255);
120 
121  if(policy.choose_key_exchange_group({curve_id}) != curve_id)
122  {
124  "Server sent ECC curve prohibited by policy");
125  }
126 
127  const std::string curve_name = state.callbacks().tls_decode_group_param(curve_id);
128 
129  if(curve_name == "")
130  throw Decoding_Error("Server sent unknown named curve " +
131  std::to_string(static_cast<uint16_t>(curve_id)));
132 
133  const std::pair<secure_vector<uint8_t>, std::vector<uint8_t>> ecdh_result =
134  state.callbacks().tls_ecdh_agree(curve_name, peer_public_value, policy, rng,
135  state.server_hello()->prefers_compressed_ec_points());
136 
137  if(kex_algo == Kex_Algo::ECDH)
138  {
139  m_pre_master = ecdh_result.first;
140  }
141  else
142  {
143  append_tls_length_value(m_pre_master, ecdh_result.first, 2);
144  append_tls_length_value(m_pre_master, psk.bits_of(), 2);
145  }
146 
147  append_tls_length_value(m_key_material, ecdh_result.second, 1);
148  }
149 #if defined(BOTAN_HAS_SRP6)
150  else if(kex_algo == Kex_Algo::SRP_SHA)
151  {
152  const BigInt N = BigInt::decode(reader.get_range<uint8_t>(2, 1, 65535));
153  const BigInt g = BigInt::decode(reader.get_range<uint8_t>(2, 1, 65535));
154  std::vector<uint8_t> salt = reader.get_range<uint8_t>(1, 1, 255);
155  const BigInt B = BigInt::decode(reader.get_range<uint8_t>(2, 1, 65535));
156 
157  const std::string srp_group = srp6_group_identifier(N, g);
158 
159  const std::string srp_identifier =
160  creds.srp_identifier("tls-client", hostname);
161 
162  const std::string srp_password =
163  creds.srp_password("tls-client", hostname, srp_identifier);
164 
165  std::pair<BigInt, SymmetricKey> srp_vals =
166  srp6_client_agree(srp_identifier,
167  srp_password,
168  srp_group,
169  "SHA-1",
170  salt,
171  B,
172  rng);
173 
174  append_tls_length_value(m_key_material, BigInt::encode(srp_vals.first), 2);
175  m_pre_master = srp_vals.second.bits_of();
176  }
177 #endif
178 
179 #if defined(BOTAN_HAS_CECPQ1)
180  else if(kex_algo == Kex_Algo::CECPQ1)
181  {
182  const std::vector<uint8_t> cecpq1_offer = reader.get_range<uint8_t>(2, 1, 65535);
183 
184  if(cecpq1_offer.size() != CECPQ1_OFFER_BYTES)
185  throw TLS_Exception(Alert::HANDSHAKE_FAILURE, "Invalid CECPQ1 key size");
186 
187  std::vector<uint8_t> newhope_accept(CECPQ1_ACCEPT_BYTES);
189  CECPQ1_accept(shared_secret.data(), newhope_accept.data(), cecpq1_offer.data(), rng);
190  append_tls_length_value(m_key_material, newhope_accept, 2);
191  m_pre_master = shared_secret;
192  }
193 #endif
194  else
195  {
196  throw Internal_Error("Client_Key_Exchange: Unknown key exchange method was negotiated");
197  }
198 
199  reader.assert_done();
200  }
201  else
202  {
203  // No server key exchange msg better mean RSA kex + RSA key in cert
204 
205  if(kex_algo != Kex_Algo::STATIC_RSA)
206  throw Unexpected_Message("No server kex message, but negotiated a key exchange that required it");
207 
208  if(!server_public_key)
209  throw Internal_Error("No server public key for RSA exchange");
210 
211  if(auto rsa_pub = dynamic_cast<const RSA_PublicKey*>(server_public_key))
212  {
213  const Protocol_Version offered_version = state.client_hello()->version();
214 
215  m_pre_master = rng.random_vec(48);
216  m_pre_master[0] = offered_version.major_version();
217  m_pre_master[1] = offered_version.minor_version();
218 
219  PK_Encryptor_EME encryptor(*rsa_pub, rng, "PKCS1v15");
220 
221  const std::vector<uint8_t> encrypted_key = encryptor.encrypt(m_pre_master, rng);
222 
223  append_tls_length_value(m_key_material, encrypted_key, 2);
224  }
225  else
227  "Expected a RSA key in server cert but got " +
228  server_public_key->algo_name());
229  }
230 
231  state.hash().update(io.send(*this));
232  }
233 
234 /*
235 * Read a Client Key Exchange message
236 */
237 Client_Key_Exchange::Client_Key_Exchange(const std::vector<uint8_t>& contents,
238  const Handshake_State& state,
239  const Private_Key* server_rsa_kex_key,
240  Credentials_Manager& creds,
241  const Policy& policy,
243  {
244  const Kex_Algo kex_algo = state.ciphersuite().kex_method();
245 
246  if(kex_algo == Kex_Algo::STATIC_RSA)
247  {
248  BOTAN_ASSERT(state.server_certs() && !state.server_certs()->cert_chain().empty(),
249  "RSA key exchange negotiated so server sent a certificate");
250 
251  if(!server_rsa_kex_key)
252  throw Internal_Error("Expected RSA kex but no server kex key set");
253 
254  if(!dynamic_cast<const RSA_PrivateKey*>(server_rsa_kex_key))
255  throw Internal_Error("Expected RSA key but got " + server_rsa_kex_key->algo_name());
256 
257  TLS_Data_Reader reader("ClientKeyExchange", contents);
258  const std::vector<uint8_t> encrypted_pre_master = reader.get_range<uint8_t>(2, 0, 65535);
259 
260  PK_Decryptor_EME decryptor(*server_rsa_kex_key, rng, "PKCS1v15");
261 
262  const uint8_t client_major = state.client_hello()->version().major_version();
263  const uint8_t client_minor = state.client_hello()->version().minor_version();
264 
265  /*
266  * PK_Decryptor::decrypt_or_random will return a random value if
267  * either the length does not match the expected value or if the
268  * version number embedded in the PMS does not match the one sent
269  * in the client hello.
270  */
271  const size_t expected_plaintext_size = 48;
272  const size_t expected_content_size = 2;
273  const uint8_t expected_content_bytes[expected_content_size] = { client_major, client_minor };
274  const uint8_t expected_content_pos[expected_content_size] = { 0, 1 };
275 
276  m_pre_master =
277  decryptor.decrypt_or_random(encrypted_pre_master.data(),
278  encrypted_pre_master.size(),
279  expected_plaintext_size,
280  rng,
281  expected_content_bytes,
282  expected_content_pos,
283  expected_content_size);
284  }
285  else
286  {
287  TLS_Data_Reader reader("ClientKeyExchange", contents);
288 
289  SymmetricKey psk;
290 
291  if(key_exchange_is_psk(kex_algo))
292  {
293  const std::string psk_identity = reader.get_string(2, 0, 65535);
294 
295  psk = creds.psk("tls-server",
296  state.client_hello()->sni_hostname(),
297  psk_identity);
298 
299  if(psk.length() == 0)
300  {
301  if(policy.hide_unknown_users())
302  psk = SymmetricKey(rng, 16);
303  else
305  "No PSK for identifier " + psk_identity);
306  }
307  }
308 
309  if(kex_algo == Kex_Algo::PSK)
310  {
311  std::vector<uint8_t> zeros(psk.length());
312  append_tls_length_value(m_pre_master, zeros, 2);
313  append_tls_length_value(m_pre_master, psk.bits_of(), 2);
314  }
315 #if defined(BOTAN_HAS_SRP6)
316  else if(kex_algo == Kex_Algo::SRP_SHA)
317  {
318  SRP6_Server_Session& srp = state.server_kex()->server_srp_params();
319 
320  m_pre_master = srp.step2(BigInt::decode(reader.get_range<uint8_t>(2, 0, 65535))).bits_of();
321  }
322 #endif
323 #if defined(BOTAN_HAS_CECPQ1)
324  else if(kex_algo == Kex_Algo::CECPQ1)
325  {
326  const CECPQ1_key& cecpq1_offer = state.server_kex()->cecpq1_key();
327 
328  const std::vector<uint8_t> cecpq1_accept = reader.get_range<uint8_t>(2, 0, 65535);
329  if(cecpq1_accept.size() != CECPQ1_ACCEPT_BYTES)
330  throw Decoding_Error("Invalid size for CECPQ1 accept message");
331 
332  m_pre_master.resize(CECPQ1_SHARED_KEY_BYTES);
333  CECPQ1_finish(m_pre_master.data(), cecpq1_offer, cecpq1_accept.data());
334  }
335 #endif
336  else if(kex_algo == Kex_Algo::DH ||
337  kex_algo == Kex_Algo::DHE_PSK ||
338  kex_algo == Kex_Algo::ECDH ||
339  kex_algo == Kex_Algo::ECDHE_PSK)
340  {
341  const Private_Key& private_key = state.server_kex()->server_kex_key();
342 
343  const PK_Key_Agreement_Key* ka_key =
344  dynamic_cast<const PK_Key_Agreement_Key*>(&private_key);
345 
346  if(!ka_key)
347  throw Internal_Error("Expected key agreement key type but got " +
348  private_key.algo_name());
349 
350  std::vector<uint8_t> client_pubkey;
351 
352  if(ka_key->algo_name() == "DH")
353  {
354  client_pubkey = reader.get_range<uint8_t>(2, 0, 65535);
355  }
356  else
357  {
358  client_pubkey = reader.get_range<uint8_t>(1, 1, 255);
359  }
360 
361  try
362  {
363  PK_Key_Agreement ka(*ka_key, rng, "Raw");
364 
365  secure_vector<uint8_t> shared_secret = ka.derive_key(0, client_pubkey).bits_of();
366 
367  if(ka_key->algo_name() == "DH")
368  shared_secret = CT::strip_leading_zeros(shared_secret);
369 
370  if(kex_algo == Kex_Algo::DHE_PSK ||
371  kex_algo == Kex_Algo::ECDHE_PSK)
372  {
373  append_tls_length_value(m_pre_master, shared_secret, 2);
374  append_tls_length_value(m_pre_master, psk.bits_of(), 2);
375  }
376  else
377  m_pre_master = shared_secret;
378  }
379  catch(std::exception &)
380  {
381  /*
382  * Something failed in the DH computation. To avoid possible
383  * timing attacks, randomize the pre-master output and carry
384  * on, allowing the protocol to fail later in the finished
385  * checks.
386  */
387  m_pre_master = rng.random_vec(ka_key->public_value().size());
388  }
389  }
390  else
391  throw Internal_Error("Client_Key_Exchange: Unknown key exchange negotiated");
392  }
393  }
394 
395 }
396 
397 }
std::vector< uint8_t > encrypt(const uint8_t in[], size_t length, RandomNumberGenerator &rng) const
Definition: pubkey.h:44
virtual std::string tls_decode_group_param(Group_Params group_param)
virtual std::vector< uint8_t > send(const Handshake_Message &msg)=0
void CECPQ1_finish(uint8_t shared_key[CECPQ1_SHARED_KEY_BYTES], const CECPQ1_key &offer_key, const uint8_t received[CECPQ1_ACCEPT_BYTES])
Definition: cecpq1.cpp:41
void server_hello(Server_Hello *server_hello)
virtual std::pair< secure_vector< uint8_t >, std::vector< uint8_t > > tls_dh_agree(const std::vector< uint8_t > &modulus, const std::vector< uint8_t > &generator, const std::vector< uint8_t > &peer_public_value, const Policy &policy, RandomNumberGenerator &rng)
virtual std::pair< secure_vector< uint8_t >, std::vector< uint8_t > > tls_ecdh_agree(const std::string &curve_name, const std::vector< uint8_t > &peer_public_value, const Policy &policy, RandomNumberGenerator &rng, bool compressed)
secure_vector< uint8_t > random_vec(size_t bytes)
Definition: rng.h:132
uint8_t minor_version() const
Definition: tls_version.h:82
virtual std::string srp_identifier(const std::string &type, const std::string &context)
virtual std::string srp_password(const std::string &type, const std::string &context, const std::string &identifier)
std::pair< BigInt, SymmetricKey > srp6_client_agree(const std::string &identifier, const std::string &password, const std::string &group_id, const std::string &hash_id, const std::vector< uint8_t > &salt, const BigInt &B, RandomNumberGenerator &rng)
Definition: srp6.cpp:77
bool key_exchange_is_psk(Kex_Algo m)
Definition: tls_algos.h:158
void server_kex(Server_Key_Exchange *server_kex)
virtual std::string algo_name() const =0
virtual std::vector< uint8_t > public_value() const =0
virtual Group_Params choose_key_exchange_group(const std::vector< Group_Params > &peer_groups) const
Definition: tls_policy.cpp:130
Kex_Algo kex_method() const
std::string to_string(const BER_Object &obj)
Definition: asn1_obj.cpp:210
SymmetricKey step2(const BigInt &A)
Definition: srp6.cpp:150
const Ciphersuite & ciphersuite() const
#define BOTAN_ASSERT(expr, assertion_made)
Definition: assert.h:43
std::string get_string(size_t len_bytes, size_t min_bytes, size_t max_bytes)
Definition: tls_reader.h:115
void client_hello(Client_Hello *client_hello)
virtual std::string psk_identity(const std::string &type, const std::string &context, const std::string &identity_hint)
std::vector< T > get_range(size_t len_bytes, size_t min_elems, size_t max_elems)
Definition: tls_reader.h:94
void update(const uint8_t in[], size_t length)
void CECPQ1_accept(uint8_t shared_key[CECPQ1_SHARED_KEY_BYTES], uint8_t send[CECPQ1_ACCEPT_BYTES], const uint8_t received[CECPQ1_OFFER_BYTES], RandomNumberGenerator &rng)
Definition: cecpq1.cpp:26
SymmetricKey derive_key(size_t key_len, const uint8_t in[], size_t in_len, const uint8_t params[], size_t params_len) const
Definition: pubkey.cpp:203
Definition: alg_id.cpp:13
Client_Key_Exchange(Handshake_IO &io, Handshake_State &state, const Policy &policy, Credentials_Manager &creds, const Public_Key *server_public_key, const std::string &hostname, RandomNumberGenerator &rng)
OctetString SymmetricKey
Definition: symkey.h:136
size_t length() const
Definition: symkey.h:25
virtual SymmetricKey psk(const std::string &type, const std::string &context, const std::string &identity)
std::unique_ptr< Public_Key > server_public_key
Definition: tls_client.cpp:38
void server_certs(Certificate *server_certs)
uint8_t major_version() const
Definition: tls_version.h:77
std::vector< T, secure_allocator< T > > secure_vector
Definition: secmem.h:88
virtual bool hide_unknown_users() const
Definition: tls_policy.cpp:328
static std::vector< uint8_t > encode(const BigInt &n, Base base=Binary)
Definition: big_code.cpp:54
secure_vector< uint8_t > bits_of() const
Definition: symkey.h:31
std::string srp6_group_identifier(const BigInt &N, const BigInt &g)
Definition: srp6.cpp:53
static BigInt decode(const uint8_t buf[], size_t length, Base base=Binary)
Definition: big_code.cpp:114
secure_vector< uint8_t > strip_leading_zeros(const uint8_t in[], size_t length)
Definition: ct_utils.h:184
void append_tls_length_value(std::vector< uint8_t, Alloc > &buf, const T *vals, size_t vals_size, size_t tag_size)
Definition: tls_reader.h:185