Finish up server side SRP support, a little ugly but it works.

Add SRP hooks in the examples

Fix next protocol support in the tls_server example.

7 files changed, 75 insertions, 36 deletions

diff --git a/src/tls/c_kex.cpp b/src/tls/c_kex.cpp
index 16c02e2b8..13925a482 100644
--- a/src/tls/c_kex.cpp
+++ b/src/tls/c_kex.cpp
@@ -332,7 +332,9 @@ Client_Key_Exchange::Client_Key_Exchange(const MemoryRegion<byte>& contents,
          }
       else if(kex_algo == "SRP_SHA")
          {
-         throw Internal_Error("SRP_SHA server side not done");
+         SRP6_Server_Session& srp = state->server_kex->server_srp_params();
+
+         pre_master = srp.step2(BigInt::decode(reader.get_range<byte>(2, 0, 65535))).bits_of();
          }
       else if(kex_algo == "DH" || kex_algo == "DHE_PSK" ||
               kex_algo == "ECDH" || kex_algo == "ECDHE_PSK")
diff --git a/src/tls/s_kex.cpp b/src/tls/s_kex.cpp
index 24bc6ecaa..68a5c16db 100644
--- a/src/tls/s_kex.cpp
+++ b/src/tls/s_kex.cpp
@@ -33,7 +33,7 @@ Server_Key_Exchange::Server_Key_Exchange(Record_Writer& writer,
                                          Credentials_Manager& creds,
                                          RandomNumberGenerator& rng,
                                          const Private_Key* signing_key) :
-   m_kex_key(0)
+   m_kex_key(0), m_srp_params(0)
    {
    const std::string hostname = state->client_hello->sni_hostname();
    const std::string kex_algo = state->suite.kex_algo();
@@ -93,34 +93,30 @@ Server_Key_Exchange::Server_Key_Exchange(Record_Writer& writer,
       {
       const std::string srp_identifier = state->client_hello->srp_identifier();
 
-      BigInt N, g, v;
+      std::string group_id;
+      BigInt v;
       MemoryVector<byte> salt;
 
       const bool found = creds.srp_verifier("tls-server", hostname,
                                             srp_identifier,
-                                            N, g, v, salt,
+                                            group_id, v, salt,
                                             policy.hide_unknown_users());
 
       if(!found)
          throw TLS_Exception(Alert::UNKNOWN_PSK_IDENTITY,
                              "Unknown SRP user " + srp_identifier);
 
-#if 0
-      BigInt B = srp6_server_step1(v, srp6_group_identifier(N, g),
-                                   "SHA-1", rng);
-#else
-      BigInt B = 0;
-#endif
+      m_srp_params = new SRP6_Server_Session;
 
-      append_tls_length_value(m_params, BigInt::encode(N), 2);
-      append_tls_length_value(m_params, BigInt::encode(g), 2);
+      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);
-
-      /*
-      * To finish, client key exchange needs to know
-      *   group_id, v, b, B
-      */
       }
    else if(kex_algo != "PSK")
       throw Internal_Error("Server_Key_Exchange: Unknown kex type " + kex_algo);
@@ -150,7 +146,7 @@ Server_Key_Exchange::Server_Key_Exchange(const MemoryRegion<byte>& buf,
                                          const std::string& kex_algo,
                                          const std::string& sig_algo,
                                          Protocol_Version version) :
-   m_kex_key(0)
+   m_kex_key(0), m_srp_params(0)
    {
    if(buf.size() < 6)
       throw Decoding_Error("Server_Key_Exchange: Packet corrupted");
@@ -230,6 +226,11 @@ Server_Key_Exchange::Server_Key_Exchange(const MemoryRegion<byte>& buf,
       }
    }
 
+Server_Key_Exchange::~Server_Key_Exchange()
+   {
+   delete m_kex_key;
+   delete m_srp_params;
+   }
 
 /**
 * Serialize a Server Key Exchange message
@@ -278,6 +279,14 @@ const Private_Key& Server_Key_Exchange::server_kex_key() const
    BOTAN_ASSERT(m_kex_key, "Key is non-NULL");
    return *m_kex_key;
    }
+
+// Only valid for SRP negotiation
+SRP6_Server_Session& Server_Key_Exchange::server_srp_params()
+   {
+   BOTAN_ASSERT(m_srp_params, "SRP params are non-NULL");
+   return *m_srp_params;
+   }
+
 }
 
 }
diff --git a/src/tls/tls_handshake_state.cpp b/src/tls/tls_handshake_state.cpp
index 48d9abbeb..8e9003108 100644
--- a/src/tls/tls_handshake_state.cpp
+++ b/src/tls/tls_handshake_state.cpp
@@ -143,6 +143,14 @@ bool Handshake_State::received_handshake_msg(Handshake_Type handshake_msg) const
    return (hand_received_mask & mask);
    }
 
+std::string Handshake_State::srp_identifier() const
+   {
+   if(suite.valid() && suite.kex_algo() == "SRP_SHA")
+      return client_hello->srp_identifier();
+
+   return "";
+   }
+
 const MemoryRegion<byte>& Handshake_State::session_ticket() const
    {
    if(new_session_ticket && !new_session_ticket->ticket().empty())
diff --git a/src/tls/tls_handshake_state.h b/src/tls/tls_handshake_state.h
index 2a78d1d1e..c347c4574 100644
--- a/src/tls/tls_handshake_state.h
+++ b/src/tls/tls_handshake_state.h
@@ -64,6 +64,8 @@ class Handshake_State
                            std::string& sig_algo,
                            bool for_client_auth);
 
+      std::string srp_identifier() const;
+
       KDF* protocol_specific_prf();
 
       Protocol_Version version() const { return m_version; }
diff --git a/src/tls/tls_messages.h b/src/tls/tls_messages.h
index ff6ebda4d..c8a9382d6 100644
--- a/src/tls/tls_messages.h
+++ b/src/tls/tls_messages.h
@@ -21,6 +21,7 @@
 namespace Botan {
 
 class Credentials_Manager;
+class SRP6_Server_Session;
 
 namespace TLS {
 
@@ -396,6 +397,9 @@ class Server_Key_Exchange : public Handshake_Message
       // Only valid for certain kex types
       const Private_Key& server_kex_key() const;
 
+      // Only valid for SRP negotiation
+      SRP6_Server_Session& server_srp_params();
+
       Server_Key_Exchange(Record_Writer& writer,
                           Handshake_State* state,
                           const Policy& policy,
@@ -408,11 +412,12 @@ class Server_Key_Exchange : public Handshake_Message
                           const std::string& sig_alg,
                           Protocol_Version version);
 
-      ~Server_Key_Exchange() { delete m_kex_key; }
+      ~Server_Key_Exchange();
    private:
       MemoryVector<byte> serialize() const;
 
       Private_Key* m_kex_key;
+      SRP6_Server_Session* m_srp_params;
 
       MemoryVector<byte> m_params;
 
diff --git a/src/tls/tls_policy.cpp b/src/tls/tls_policy.cpp
index de3c6f674..c42a6904c 100644
--- a/src/tls/tls_policy.cpp
+++ b/src/tls/tls_policy.cpp
@@ -47,7 +47,7 @@ std::vector<std::string> Policy::allowed_key_exchange_methods() const
    {
    std::vector<std::string> allowed;
 
-   //allowed.push_back("SRP_SHA");
+   allowed.push_back("SRP_SHA");
    //allowed.push_back("ECDHE_PSK");
    //allowed.push_back("DHE_PSK");
    //allowed.push_back("PSK");
@@ -204,19 +204,10 @@ class Ciphersuite_Preference_Ordering
 std::vector<u16bit> ciphersuite_list(const Policy& policy,
                                      bool have_srp)
    {
-   std::vector<std::string> ciphers = policy.allowed_ciphers();
-   std::vector<std::string> hashes = policy.allowed_hashes();
-   std::vector<std::string> kex = policy.allowed_key_exchange_methods();
-   std::vector<std::string> sigs = policy.allowed_signature_methods();
-
-   if(!have_srp)
-      {
-      std::vector<std::string>::iterator i =
-         std::find(kex.begin(), kex.end(), "SRP_SHA");
-
-      if(i != kex.end())
-         kex.erase(i);
-      }
+   const std::vector<std::string> ciphers = policy.allowed_ciphers();
+   const std::vector<std::string> hashes = policy.allowed_hashes();
+   const std::vector<std::string> kex = policy.allowed_key_exchange_methods();
+   const std::vector<std::string> sigs = policy.allowed_signature_methods();
 
    Ciphersuite_Preference_Ordering order(ciphers, hashes, kex, sigs);
 
@@ -230,6 +221,9 @@ std::vector<u16bit> ciphersuite_list(const Policy& policy,
       if(!suite.valid())
          continue; // not a ciphersuite we know, skip
 
+      if(!have_srp && suite.kex_algo() == "SRP_SHA")
+         continue;
+
       if(!value_exists(kex, suite.kex_algo()))
          continue; // unsupported key exchange
 
diff --git a/src/tls/tls_server.cpp b/src/tls/tls_server.cpp
index f5b4efc30..10872a825 100644
--- a/src/tls/tls_server.cpp
+++ b/src/tls/tls_server.cpp
@@ -91,11 +91,18 @@ bool check_for_resume(Session& session_info,
 */
 u16bit choose_ciphersuite(
    const Policy& policy,
+   Credentials_Manager& creds,
    const std::map<std::string, std::vector<X509_Certificate> >& cert_chains,
    const Client_Hello* client_hello)
    {
+   const bool have_srp = creds.attempt_srp("tls-server",
+                                           client_hello->sni_hostname());
+
    const std::vector<u16bit> client_suites = client_hello->ciphersuites();
-   const std::vector<u16bit> server_suites = ciphersuite_list(policy, false);
+   const std::vector<u16bit> server_suites = ciphersuite_list(policy, have_srp);
+
+   if(server_suites.empty())
+      throw Internal_Error("Policy forbids us from negotiating any ciphersuite");
 
    const bool have_shared_ecc_curve =
       (policy.choose_curve(client_hello->supported_ecc_curves()) != "");
@@ -116,6 +123,18 @@ u16bit choose_ciphersuite(
       if(cert_chains.count(suite.sig_algo()) == 0)
          continue;
 
+      /*
+      The client may offer SRP cipher suites in the hello message but
+      omit the SRP extension.  If the server would like to select an
+      SRP cipher suite in this case, the server SHOULD return a fatal
+      "unknown_psk_identity" alert immediately after processing the
+      client hello message.
+       - RFC 5054 section 2.5.1.2
+      */
+      if(suite.kex_algo() == "SRP_SHA" && client_hello->srp_identifier() == "")
+         throw TLS_Exception(Alert::UNKNOWN_PSK_IDENTITY,
+                             "Client wanted SRP but did not send username");
+
       return suite_id;
       }
 
@@ -368,7 +387,7 @@ void Server::process_handshake_msg(Handshake_Type type,
             state->hash,
             rng.random_vec(32), // new session ID
             state->version(),
-            choose_ciphersuite(policy, cert_chains, state->client_hello),
+            choose_ciphersuite(policy, creds, cert_chains, state->client_hello),
             choose_compression(policy, state->client_hello->compression_methods()),
             state->client_hello->fragment_size(),
             secure_renegotiation.supported(),
@@ -546,7 +565,7 @@ void Server::process_handshake_msg(Handshake_Type type,
             peer_certs,
             MemoryVector<byte>(),
             m_hostname,
-            ""
+            state->srp_identifier()
             );
 
          if(handshake_fn(session_info))