Fix kex methods

src/_locales/en/messages.json

@@ -189,6 +189,10 @@
     "message": "Initialization of SSH2 session failed",
     "description": "libssh2_session_init() failed"
   },
+  "sftpThreadError_sshKEXMethodPrefsFailed" : {
+    "message": "Couldn't set key exchange method preferences",
+    "description": "libssh_session_method_prefs() failed"
+  },
   "sftpThreadError_sshSessionHandshakeFailed" : {
     "message": "Finishing SSH2 session failed",
     "description": "Error when starting up SSH session"

src/_locales/nl/messages.json

@@ -185,6 +185,9 @@
   "sftpThreadError_sshInitSessionFailed" : {
     "message": "Initialiseren van een SSH2-sessie is mislukt"
   },
+  "sftpThreadError_sshKEXMethodPrefsFailed" : {
+    "message": "Kan de voorkeuren voor de sleuteluitwisseling methode niet instellen"
+  },
   "sftpThreaderror_sshSessionHandshakeFailed" : {
     "message": "Voltooien van een SSH2-sessie is mislukt"
   },

src/nacl_src/sftp_thread.cc

@@ -300,6 +300,7 @@ void SftpThread::ConnectAndHandshakeImpl()
     InitializeLibssh2();
     sock = ConnectToSshServer(server_hostname_, server_port_);
     session = InitializeSession();
+    SetKEXMethodPrefs(session);
     HandshakeSession(session, sock);
     std::string fingerprint;
     fingerprint = GetHostKeyHash(session);
@@ -374,6 +375,20 @@ LIBSSH2_SESSION* SftpThread::InitializeSession() throw(CommunicationException)
   return session;
 }
 
+void SftpThread::SetKEXMethodPrefs(LIBSSH2_SESSION *session)
+  throw(CommunicationException)
+{
+  fprintf(stderr, "SftpThread::SetKEXMethodPrefs\n");
+  const char *methods;
+  methods = "curve25519-sha256,curve25519-sha256@libssh.org,ecdh-sha2-nistp256,ecdh-sha2-nistp384,ecdh-sha2-nistp521,diffie-hellman-group-exchange-sha256,diffie-hellman-group16-sha512,diffie-hellman-group18-sha512,diffie-hellman-group14-sha256";
+  int rc;
+  while ((rc = libssh2_session_method_pref(session, LIBSSH2_METHOD_HOSTKEY, methods)) == LIBSSH2_ERROR_EAGAIN);
+  fprintf(stderr, "SftpThread::SetKEXMethodPrefs rc=%d\n", rc);
+  if (rc) {
+    THROW_COMMUNICATION_EXCEPTION("sftpThreadError_sshKEXMethodPrefsFailed", rc);
+  }
+}
+
 void SftpThread::HandshakeSession(LIBSSH2_SESSION *session, int sock)
   throw(CommunicationException)
 {

src/nacl_src/sftp_thread.h

@@ -71,6 +71,7 @@ class SftpThread
   void InitializeLibssh2() throw(CommunicationException);
   int ConnectToSshServer(const std::string &hostname, const int port) throw(CommunicationException);
   LIBSSH2_SESSION* InitializeSession() throw(CommunicationException);
+  void SetKEXMethodPrefs(LIBSSH2_SESSION *session) throw(CommunicationException);
   void HandshakeSession(LIBSSH2_SESSION *session,
                         int sock) throw(CommunicationException);
   std::string GetHostKeyHash(LIBSSH2_SESSION *session);