Initial client-side support for SRP (finally!). Tested against OpenSSL

1.0.1, only the certificate versions tested currently as OpenSSL
doesn't support anon SRP.

4 files changed, 45 insertions, 0 deletions

diff --git a/src/tls/c_kex.cpp b/src/tls/c_kex.cpp
index ed571852c..0a6339bd0 100644
--- a/src/tls/c_kex.cpp
+++ b/src/tls/c_kex.cpp
@@ -15,6 +15,7 @@
 #include <botan/dh.h>
 #include <botan/ecdh.h>
 #include <botan/rsa.h>
+#include <botan/srp6.h>
 #include <botan/rng.h>
 #include <botan/loadstor.h>
 #include <memory>
@@ -50,6 +51,7 @@ Client_Key_Exchange::Client_Key_Exchange(Record_Writer& writer,
                                          Handshake_State* state,
                                          Credentials_Manager& creds,
                                          const std::vector<X509_Certificate>& peer_certs,
+                                         const std::string& hostname,
                                          RandomNumberGenerator& rng)
    {
    const std::string kex_algo = state->suite.kex_algo();
@@ -171,6 +173,33 @@ Client_Key_Exchange::Client_Key_Exchange(Record_Writer& writer,
 
          append_tls_length_value(key_material, priv_key.public_value(), 1);
          }
+      else if(kex_algo == "SRP_SHA")
+         {
+         const BigInt N = BigInt::decode(reader.get_range<byte>(2, 1, 65535));
+         const BigInt g = BigInt::decode(reader.get_range<byte>(2, 1, 65535));
+         MemoryVector<byte> salt = reader.get_range<byte>(1, 1, 255);
+         const BigInt B = BigInt::decode(reader.get_range<byte>(2, 1, 65535));
+
+         const std::string srp_group = srp6_group_identifier(N, g);
+
+         const std::string srp_identifier =
+            creds.srp_identifier("tls-client", hostname);
+
+         const std::string srp_password =
+            creds.srp_password("tls-client", hostname, srp_identifier);
+
+         std::pair<BigInt, SymmetricKey> srp_vals =
+            srp6_client_agree(srp_identifier,
+                              srp_password,
+                              srp_group,
+                              "SHA-1",
+                              salt,
+                              B,
+                              rng);
+
+         append_tls_length_value(key_material, BigInt::encode(srp_vals.first), 2);
+         pre_master = srp_vals.second.bits_of();
+         }
       else
          {
          throw Internal_Error("Client_Key_Exchange: Unknown kex " +
diff --git a/src/tls/s_kex.cpp b/src/tls/s_kex.cpp
index 6707d2611..a5c8ff8d7 100644
--- a/src/tls/s_kex.cpp
+++ b/src/tls/s_kex.cpp
@@ -167,6 +167,20 @@ Server_Key_Exchange::Server_Key_Exchange(const MemoryRegion<byte>& buf,
       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));
+      MemoryVector<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);
 
diff --git a/src/tls/tls_client.cpp b/src/tls/tls_client.cpp
index 2ec7eec2e..850d053a2 100644
--- a/src/tls/tls_client.cpp
+++ b/src/tls/tls_client.cpp
@@ -342,6 +342,7 @@ void Client::process_handshake_msg(Handshake_Type type,
                                  state,
                                  creds,
                                  peer_certs,
+                                 state->client_hello->sni_hostname(),
                                  rng);
 
       state->keys = Session_Keys(state,
diff --git a/src/tls/tls_messages.h b/src/tls/tls_messages.h
index 920a1c7a7..ff6ebda4d 100644
--- a/src/tls/tls_messages.h
+++ b/src/tls/tls_messages.h
@@ -238,6 +238,7 @@ class Client_Key_Exchange : public Handshake_Message
                           Handshake_State* state,
                           Credentials_Manager& creds,
                           const std::vector<X509_Certificate>& peer_certs,
+                          const std::string& hostname,
                           RandomNumberGenerator& rng);
 
       Client_Key_Exchange(const MemoryRegion<byte>& buf,