1 files changed, 285 insertions, 0 deletions
diff --git a/src/lib/tls/msg_server_kex.cpp b/src/lib/tls/msg_server_kex.cpp
new file mode 100644
index 000000000..b8293d3e8
--- /dev/null
+++ b/src/lib/tls/msg_server_kex.cpp
@@ -0,0 +1,285 @@
+/*
+* Server Key Exchange Message
+* (C) 2004-2010,2012 Jack Lloyd
+*
+* Released under the terms of the Botan license
+*/
+
+#include <botan/internal/tls_messages.h>
+#include <botan/internal/tls_reader.h>
+#include <botan/internal/tls_extensions.h>
+#include <botan/internal/tls_handshake_io.h>
+#include <botan/credentials_manager.h>
+#include <botan/loadstor.h>
+#include <botan/pubkey.h>
+#include <botan/dh.h>
+#include <botan/ecdh.h>
+#include <botan/rsa.h>
+#include <botan/srp6.h>
+#include <botan/oids.h>
+#include <memory>
+
+namespace Botan {
+
+namespace TLS {
+
+/**
+* Create a new Server Key Exchange message
+*/
+Server_Key_Exchange::Server_Key_Exchange(Handshake_IO& io,
+                                         Handshake_State& state,
+                                         const Policy& policy,
+                                         Credentials_Manager& creds,
+                                         RandomNumberGenerator& rng,
+                                         const Private_Key* signing_key)
+   {
+   const std::string hostname = state.client_hello()->sni_hostname();
+   const std::string kex_algo = state.ciphersuite().kex_algo();
+
+   if(kex_algo == "PSK" || kex_algo == "DHE_PSK" || kex_algo == "ECDHE_PSK")
+      {
+      std::string identity_hint =
+         creds.psk_identity_hint("tls-server", hostname);
+
+      append_tls_length_value(m_params, identity_hint, 2);
+      }
+
+   if(kex_algo == "DH" || kex_algo == "DHE_PSK")
+      {
+      std::unique_ptr<DH_PrivateKey> dh(new DH_PrivateKey(rng, policy.dh_group()));
+
+      append_tls_length_value(m_params, BigInt::encode(dh->get_domain().get_p()), 2);
+      append_tls_length_value(m_params, BigInt::encode(dh->get_domain().get_g()), 2);
+      append_tls_length_value(m_params, dh->public_value(), 2);
+      m_kex_key.reset(dh.release());
+      }
+   else if(kex_algo == "ECDH" || kex_algo == "ECDHE_PSK")
+      {
+      const std::vector<std::string>& curves =
+         state.client_hello()->supported_ecc_curves();
+
+      if(curves.empty())
+         throw Internal_Error("Client sent no ECC extension but we negotiated ECDH");
+
+      const std::string curve_name = policy.choose_curve(curves);
+
+      if(curve_name == "")
+         throw TLS_Exception(Alert::HANDSHAKE_FAILURE,
+                             "Could not agree on an ECC curve with the client");
+
+      EC_Group ec_group(curve_name);
+
+      std::unique_ptr<ECDH_PrivateKey> ecdh(new ECDH_PrivateKey(rng, ec_group));
+
+      const std::string ecdh_domain_oid = ecdh->domain().get_oid();
+      const std::string domain = OIDS::lookup(OID(ecdh_domain_oid));
+
+      if(domain == "")
+         throw Internal_Error("Could not find name of ECDH domain " + ecdh_domain_oid);
+
+      const u16bit named_curve_id = Supported_Elliptic_Curves::name_to_curve_id(domain);
+
+      m_params.push_back(3); // named curve
+      m_params.push_back(get_byte(0, named_curve_id));
+      m_params.push_back(get_byte(1, named_curve_id));
+
+      append_tls_length_value(m_params, ecdh->public_value(), 1);
+
+      m_kex_key.reset(ecdh.release());
+      }
+   else if(kex_algo == "SRP_SHA")
+      {
+      const std::string srp_identifier = state.client_hello()->srp_identifier();
+
+      std::string group_id;
+      BigInt v;
+      std::vector<byte> salt;
+
+      const bool found = creds.srp_verifier("tls-server", hostname,
+                                            srp_identifier,
+                                            group_id, v, salt,
+                                            policy.hide_unknown_users());
+
+      if(!found)
+         throw TLS_Exception(Alert::UNKNOWN_PSK_IDENTITY,
+                             "Unknown SRP user " + srp_identifier);
+
+      m_srp_params.reset(new SRP6_Server_Session);
+
+      BigInt B = m_srp_params->step1(v, group_id,
+                                     "SHA-1", rng);
+
+      DL_Group group(group_id);
+
+      append_tls_length_value(m_params, BigInt::encode(group.get_p()), 2);
+      append_tls_length_value(m_params, BigInt::encode(group.get_g()), 2);
+      append_tls_length_value(m_params, salt, 1);
+      append_tls_length_value(m_params, BigInt::encode(B), 2);
+      }
+   else if(kex_algo != "PSK")
+      throw Internal_Error("Server_Key_Exchange: Unknown kex type " + kex_algo);
+
+   if(state.ciphersuite().sig_algo() != "")
+      {
+      BOTAN_ASSERT(signing_key, "Signing key was set");
+
+      std::pair<std::string, Signature_Format> format =
+         state.choose_sig_format(*signing_key, m_hash_algo, m_sig_algo, false, policy);
+
+      PK_Signer signer(*signing_key, format.first, format.second);
+
+      signer.update(state.client_hello()->random());
+      signer.update(state.server_hello()->random());
+      signer.update(params());
+      m_signature = signer.signature(rng);
+      }
+
+   state.hash().update(io.send(*this));
+   }
+
+/**
+* Deserialize a Server Key Exchange message
+*/
+Server_Key_Exchange::Server_Key_Exchange(const std::vector<byte>& buf,
+                                         const std::string& kex_algo,
+                                         const std::string& sig_algo,
+                                         Protocol_Version version) :
+   m_kex_key(nullptr), m_srp_params(nullptr)
+   {
+   if(buf.size() < 6)
+      throw Decoding_Error("Server_Key_Exchange: Packet corrupted");
+
+   TLS_Data_Reader reader(buf);
+
+   /*
+   * We really are just serializing things back to what they were
+   * before, but unfortunately to know where the signature is we need
+   * to be able to parse the whole thing anyway.
+   */
+
+   if(kex_algo == "PSK" || kex_algo == "DHE_PSK" || kex_algo == "ECDHE_PSK")
+      {
+      const std::string identity_hint = reader.get_string(2, 0, 65535);
+      append_tls_length_value(m_params, identity_hint, 2);
+      }
+
+   if(kex_algo == "DH" || kex_algo == "DHE_PSK")
+      {
+      // 3 bigints, DH p, g, Y
+
+      for(size_t i = 0; i != 3; ++i)
+         {
+         BigInt v = BigInt::decode(reader.get_range<byte>(2, 1, 65535));
+         append_tls_length_value(m_params, BigInt::encode(v), 2);
+         }
+      }
+   else if(kex_algo == "ECDH" || kex_algo == "ECDHE_PSK")
+      {
+      const byte curve_type = reader.get_byte();
+
+      if(curve_type != 3)
+         throw Decoding_Error("Server_Key_Exchange: Server sent non-named ECC curve");
+
+      const u16bit curve_id = reader.get_u16bit();
+
+      const std::string name = Supported_Elliptic_Curves::curve_id_to_name(curve_id);
+
+      std::vector<byte> ecdh_key = reader.get_range<byte>(1, 1, 255);
+
+      if(name == "")
+         throw Decoding_Error("Server_Key_Exchange: Server sent unknown named curve " +
+                              std::to_string(curve_id));
+
+      m_params.push_back(curve_type);
+      m_params.push_back(get_byte(0, curve_id));
+      m_params.push_back(get_byte(1, curve_id));
+      append_tls_length_value(m_params, ecdh_key, 1);
+      }
+   else if(kex_algo == "SRP_SHA")
+      {
+      // 2 bigints (N,g) then salt, then server B
+
+      const BigInt N = BigInt::decode(reader.get_range<byte>(2, 1, 65535));
+      const BigInt g = BigInt::decode(reader.get_range<byte>(2, 1, 65535));
+      std::vector<byte> salt = reader.get_range<byte>(1, 1, 255);
+      const BigInt B = BigInt::decode(reader.get_range<byte>(2, 1, 65535));
+
+      append_tls_length_value(m_params, BigInt::encode(N), 2);
+      append_tls_length_value(m_params, BigInt::encode(g), 2);
+      append_tls_length_value(m_params, salt, 1);
+      append_tls_length_value(m_params, BigInt::encode(B), 2);
+      }
+   else if(kex_algo != "PSK")
+      throw Decoding_Error("Server_Key_Exchange: Unsupported kex type " + kex_algo);
+
+   if(sig_algo != "")
+      {
+      if(version.supports_negotiable_signature_algorithms())
+         {
+         m_hash_algo = Signature_Algorithms::hash_algo_name(reader.get_byte());
+         m_sig_algo = Signature_Algorithms::sig_algo_name(reader.get_byte());
+         }
+
+      m_signature = reader.get_range<byte>(2, 0, 65535);
+      }
+
+   reader.assert_done();
+   }
+
+Server_Key_Exchange::~Server_Key_Exchange() {}
+
+/**
+* Serialize a Server Key Exchange message
+*/
+std::vector<byte> Server_Key_Exchange::serialize() const
+   {
+   std::vector<byte> buf = params();
+
+   if(m_signature.size())
+      {
+      // This should be an explicit version check
+      if(m_hash_algo != "" && m_sig_algo != "")
+         {
+         buf.push_back(Signature_Algorithms::hash_algo_code(m_hash_algo));
+         buf.push_back(Signature_Algorithms::sig_algo_code(m_sig_algo));
+         }
+
+      append_tls_length_value(buf, m_signature, 2);
+      }
+
+   return buf;
+   }
+
+/**
+* Verify a Server Key Exchange message
+*/
+bool Server_Key_Exchange::verify(const Public_Key& server_key,
+                                 const Handshake_State& state) const
+   {
+   std::pair<std::string, Signature_Format> format =
+      state.understand_sig_format(server_key, m_hash_algo, m_sig_algo, false);
+
+   PK_Verifier verifier(server_key, format.first, format.second);
+
+   verifier.update(state.client_hello()->random());
+   verifier.update(state.server_hello()->random());
+   verifier.update(params());
+
+   return verifier.check_signature(m_signature);
+   }
+
+const Private_Key& Server_Key_Exchange::server_kex_key() const
+   {
+   BOTAN_ASSERT_NONNULL(m_kex_key);
+   return *m_kex_key;
+   }
+
+// Only valid for SRP negotiation
+SRP6_Server_Session& Server_Key_Exchange::server_srp_params() const
+   {
+   BOTAN_ASSERT_NONNULL(m_srp_params);
+   return *m_srp_params;
+   }
+}
+
+}