/** * FreeRDP: A Remote Desktop Protocol Client * RDP Protocol Security Negotiation * * Copyright 2011 Marc-Andre Moreau * * Licensed under the Apache License, Version 2.0 (the "License"); * you may not use this file except in compliance with the License. * You may obtain a copy of the License at * * http://www.apache.org/licenses/LICENSE-2.0 * * Unless required by applicable law or agreed to in writing, software * distributed under the License is distributed on an "AS IS" BASIS, * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. * See the License for the specific language governing permissions and * limitations under the License. */ #include #include #include #include #include "tpkt.h" #include "nego.h" #include "transport.h" static const char* const NEGO_STATE_STRINGS[] = { "NEGO_STATE_INITIAL", "NEGO_STATE_NLA", "NEGO_STATE_TLS", "NEGO_STATE_RDP", "NEGO_STATE_FAIL", "NEGO_STATE_FINAL" }; static const char PROTOCOL_SECURITY_STRINGS[3][4] = { "RDP", "TLS", "NLA" }; boolean nego_security_connect(rdpNego* nego); /** * Negotiate protocol security and connect. * @param nego * @return */ boolean nego_connect(rdpNego* nego) { if (nego->state == NEGO_STATE_INITIAL) { if (nego->enabled_protocols[PROTOCOL_NLA] > 0) nego->state = NEGO_STATE_NLA; else if (nego->enabled_protocols[PROTOCOL_TLS] > 0) nego->state = NEGO_STATE_TLS; else if (nego->enabled_protocols[PROTOCOL_RDP] > 0) nego->state = NEGO_STATE_RDP; else { DEBUG_NEGO("No security protocol is enabled"); nego->state = NEGO_STATE_FAIL; } if (!nego->security_layer_negotiation_enabled) { DEBUG_NEGO("Security Layer Negotiation is disabled"); /* attempt only the highest enabled protocol (see nego_attempt_*) */ nego->enabled_protocols[PROTOCOL_NLA] = 0; nego->enabled_protocols[PROTOCOL_TLS] = 0; nego->enabled_protocols[PROTOCOL_RDP] = 0; if(nego->state == NEGO_STATE_NLA) { nego->enabled_protocols[PROTOCOL_NLA] = 1; nego->selected_protocol = PROTOCOL_NLA; } else if (nego->state == NEGO_STATE_TLS) { nego->enabled_protocols[PROTOCOL_TLS] = 1; nego->selected_protocol = PROTOCOL_TLS; } else if (nego->state == NEGO_STATE_RDP) { nego->enabled_protocols[PROTOCOL_RDP] = 1; nego->selected_protocol = PROTOCOL_RDP; } } if(!nego_send_preconnection_pdu(nego)) { DEBUG_NEGO("Failed to send preconnection information"); nego->state = NEGO_STATE_FINAL; return false; } } do { DEBUG_NEGO("state: %s", NEGO_STATE_STRINGS[nego->state]); nego_send(nego); if (nego->state == NEGO_STATE_FAIL) { DEBUG_NEGO("Protocol Security Negotiation Failure"); nego->state = NEGO_STATE_FINAL; return false; } } while (nego->state != NEGO_STATE_FINAL); DEBUG_NEGO("Negotiated %s security", PROTOCOL_SECURITY_STRINGS[nego->selected_protocol]); /* update settings with negotiated protocol security */ nego->transport->settings->requested_protocols = nego->requested_protocols; nego->transport->settings->selected_protocol = nego->selected_protocol; nego->transport->settings->negotiationFlags = nego->flags; if(nego->selected_protocol == PROTOCOL_RDP) { nego->transport->settings->encryption = true; nego->transport->settings->encryption_method = ENCRYPTION_METHOD_40BIT | ENCRYPTION_METHOD_128BIT | ENCRYPTION_METHOD_FIPS; nego->transport->settings->encryption_level = ENCRYPTION_LEVEL_CLIENT_COMPATIBLE; } /* finally connect security layer (if not already done) */ if(!nego_security_connect(nego)) { DEBUG_NEGO("Failed to connect with %s security", PROTOCOL_SECURITY_STRINGS[nego->selected_protocol]); return false; } return true; } /* connect to selected security layer */ boolean nego_security_connect(rdpNego* nego) { if(!nego->tcp_connected) { nego->security_connected = false; } else if (!nego->security_connected) { if (nego->selected_protocol == PROTOCOL_NLA) { DEBUG_NEGO("nego_security_connect with PROTOCOL_NLA"); nego->security_connected = transport_connect_nla(nego->transport); } else if (nego->selected_protocol == PROTOCOL_TLS ) { DEBUG_NEGO("nego_security_connect with PROTOCOL_TLS"); nego->security_connected = transport_connect_tls(nego->transport); } else if (nego->selected_protocol == PROTOCOL_RDP) { DEBUG_NEGO("nego_security_connect with PROTOCOL_RDP"); nego->security_connected = transport_connect_rdp(nego->transport); } else { DEBUG_NEGO("cannot connect security layer because no protocol has been selected yet."); } } return nego->security_connected; } /** * Connect TCP layer. * @param nego * @return */ boolean nego_tcp_connect(rdpNego* nego) { if (!nego->tcp_connected) nego->tcp_connected = transport_connect(nego->transport, nego->hostname, nego->port); return nego->tcp_connected; } /** * Connect TCP layer. For direct approach, connect security layer as well. * @param nego * @return */ boolean nego_transport_connect(rdpNego* nego) { nego_tcp_connect(nego); if (nego->tcp_connected && !nego->security_layer_negotiation_enabled) return nego_security_connect(nego); return nego->tcp_connected; } /** * Disconnect TCP layer. * @param nego * @return */ int nego_transport_disconnect(rdpNego* nego) { if (nego->tcp_connected) transport_disconnect(nego->transport); nego->tcp_connected = 0; nego->security_connected = 0; return 1; } /** * Send preconnection information if enabled. * @param nego * @return */ boolean nego_send_preconnection_pdu(rdpNego* nego) { STREAM* s; uint32 cbSize; UNICONV* uniconv; uint16 cchPCB_times2 = 0; char* wszPCB = NULL; if (!nego->send_preconnection_pdu) return true; DEBUG_NEGO("Sending preconnection PDU"); if (!nego_tcp_connect(nego)) return false; /* it's easier to always send the version 2 PDU, and it's just 2 bytes overhead */ cbSize = PRECONNECTION_PDU_V2_MIN_SIZE; if (nego->preconnection_blob) { size_t size; uniconv = freerdp_uniconv_new(); wszPCB = freerdp_uniconv_out(uniconv, nego->preconnection_blob, &size); cchPCB_times2 = (uint16) size; freerdp_uniconv_free(uniconv); cchPCB_times2 += 2; /* zero-termination */ cbSize += cchPCB_times2; } s = transport_send_stream_init(nego->transport, cbSize); stream_write_uint32(s, cbSize); /* cbSize */ stream_write_uint32(s, 0); /* Flags */ stream_write_uint32(s, PRECONNECTION_PDU_V2); /* Version */ stream_write_uint32(s, nego->preconnection_id); /* Id */ stream_write_uint16(s, cchPCB_times2 / 2); /* cchPCB */ if (wszPCB) { stream_write(s, wszPCB, cchPCB_times2); /* wszPCB */ xfree(wszPCB); } if (transport_write(nego->transport, s) < 0) return false; return true; } /** * Attempt negotiating NLA + TLS security. * @param nego */ void nego_attempt_nla(rdpNego* nego) { nego->requested_protocols = PROTOCOL_NLA | PROTOCOL_TLS; DEBUG_NEGO("Attempting NLA security"); if (!nego_transport_connect(nego)) { nego->state = NEGO_STATE_FAIL; return; } if (!nego_send_negotiation_request(nego)) { nego->state = NEGO_STATE_FAIL; return; } if (!nego_recv_response(nego)) { nego->state = NEGO_STATE_FAIL; return; } DEBUG_NEGO("state: %s", NEGO_STATE_STRINGS[nego->state]); if (nego->state != NEGO_STATE_FINAL) { nego_transport_disconnect(nego); if (nego->enabled_protocols[PROTOCOL_TLS] > 0) nego->state = NEGO_STATE_TLS; else if (nego->enabled_protocols[PROTOCOL_RDP] > 0) nego->state = NEGO_STATE_RDP; else nego->state = NEGO_STATE_FAIL; } } /** * Attempt negotiating TLS security. * @param nego */ void nego_attempt_tls(rdpNego* nego) { nego->requested_protocols = PROTOCOL_TLS; DEBUG_NEGO("Attempting TLS security"); if (!nego_transport_connect(nego)) { nego->state = NEGO_STATE_FAIL; return; } if (!nego_send_negotiation_request(nego)) { nego->state = NEGO_STATE_FAIL; return; } if (!nego_recv_response(nego)) { nego->state = NEGO_STATE_FAIL; return; } if (nego->state != NEGO_STATE_FINAL) { nego_transport_disconnect(nego); if (nego->enabled_protocols[PROTOCOL_RDP] > 0) nego->state = NEGO_STATE_RDP; else nego->state = NEGO_STATE_FAIL; } } /** * Attempt negotiating standard RDP security. * @param nego */ void nego_attempt_rdp(rdpNego* nego) { nego->requested_protocols = PROTOCOL_RDP; DEBUG_NEGO("Attempting RDP security"); if (!nego_transport_connect(nego)) { nego->state = NEGO_STATE_FAIL; return; } if (!nego_send_negotiation_request(nego)) { nego->state = NEGO_STATE_FAIL; return; } if (!nego_recv_response(nego)) { nego->state = NEGO_STATE_FAIL; return; } } /** * Wait to receive a negotiation response * @param nego */ boolean nego_recv_response(rdpNego* nego) { STREAM* s = transport_recv_stream_init(nego->transport, 1024); if (transport_read(nego->transport, s) < 0) return false; return nego_recv(nego->transport, s, nego); } /** * Receive protocol security negotiation message.\n * @msdn{cc240501} * @param transport transport * @param s stream * @param extra nego pointer */ boolean nego_recv(rdpTransport* transport, STREAM* s, void* extra) { uint8 li; uint8 type; rdpNego* nego = (rdpNego*) extra; if (tpkt_read_header(s) == 0) return false; li = tpdu_read_connection_confirm(s); if (li > 6) { /* rdpNegData (optional) */ stream_read_uint8(s, type); /* Type */ switch (type) { case TYPE_RDP_NEG_RSP: nego_process_negotiation_response(nego, s); DEBUG_NEGO("selected_protocol: %d", nego->selected_protocol); /* enhanced security selected ? */ if (nego->selected_protocol) { if ((nego->selected_protocol == PROTOCOL_NLA) && (!nego->enabled_protocols[PROTOCOL_NLA])) { nego->state = NEGO_STATE_FAIL; } if ((nego->selected_protocol == PROTOCOL_TLS) && (!nego->enabled_protocols[PROTOCOL_TLS])) { nego->state = NEGO_STATE_FAIL; } } else if (!nego->enabled_protocols[PROTOCOL_RDP]) { nego->state = NEGO_STATE_FAIL; } break; case TYPE_RDP_NEG_FAILURE: nego_process_negotiation_failure(nego, s); break; } } else { DEBUG_NEGO("no rdpNegData"); if (!nego->enabled_protocols[PROTOCOL_RDP]) nego->state = NEGO_STATE_FAIL; else nego->state = NEGO_STATE_FINAL; } return true; } /** * Read protocol security negotiation request message.\n * @param nego * @param s stream */ boolean nego_read_request(rdpNego* nego, STREAM* s) { uint8 li; uint8 c; uint8 type; tpkt_read_header(s); li = tpdu_read_connection_request(s); if (li != stream_get_left(s) + 6) { printf("Incorrect TPDU length indicator.\n"); return false; } if (stream_get_left(s) > 8) { /* Optional routingToken or cookie, ending with CR+LF */ while (stream_get_left(s) > 0) { stream_read_uint8(s, c); if (c != '\x0D') continue; stream_peek_uint8(s, c); if (c != '\x0A') continue; stream_seek_uint8(s); break; } } if (stream_get_left(s) >= 8) { /* rdpNegData (optional) */ stream_read_uint8(s, type); /* Type */ if (type != TYPE_RDP_NEG_REQ) { printf("Incorrect negotiation request type %d\n", type); return false; } nego_process_negotiation_request(nego, s); } return true; } /** * Send protocol security negotiation message. * @param nego */ void nego_send(rdpNego* nego) { if (nego->state == NEGO_STATE_NLA) nego_attempt_nla(nego); else if (nego->state == NEGO_STATE_TLS) nego_attempt_tls(nego); else if (nego->state == NEGO_STATE_RDP) nego_attempt_rdp(nego); else DEBUG_NEGO("invalid negotiation state for sending"); } /** * Send RDP Negotiation Request (RDP_NEG_REQ).\n * @msdn{cc240500}\n * @msdn{cc240470} * @param nego */ boolean nego_send_negotiation_request(rdpNego* nego) { STREAM* s; int length; uint8 *bm, *em; s = transport_send_stream_init(nego->transport, 256); length = TPDU_CONNECTION_REQUEST_LENGTH; stream_get_mark(s, bm); stream_seek(s, length); if (nego->routing_token != NULL) { stream_write(s, nego->routing_token->data, nego->routing_token->length); length += nego->routing_token->length; } else if (nego->cookie != NULL) { int cookie_length = strlen(nego->cookie); stream_write(s, "Cookie: mstshash=", 17); stream_write(s, (uint8*) nego->cookie, cookie_length); stream_write_uint8(s, 0x0D); /* CR */ stream_write_uint8(s, 0x0A); /* LF */ length += cookie_length + 19; } DEBUG_NEGO("requested_protocols: %d", nego->requested_protocols); if (nego->requested_protocols > PROTOCOL_RDP) { /* RDP_NEG_DATA must be present for TLS and NLA */ stream_write_uint8(s, TYPE_RDP_NEG_REQ); stream_write_uint8(s, 0); /* flags, must be set to zero */ stream_write_uint16(s, 8); /* RDP_NEG_DATA length (8) */ stream_write_uint32(s, nego->requested_protocols); /* requestedProtocols */ length += 8; } stream_get_mark(s, em); stream_set_mark(s, bm); tpkt_write_header(s, length); tpdu_write_connection_request(s, length - 5); stream_set_mark(s, em); if (transport_write(nego->transport, s) < 0) return false; return true; } /** * Process Negotiation Request from Connection Request message. * @param nego * @param s */ void nego_process_negotiation_request(rdpNego* nego, STREAM* s) { uint8 flags; uint16 length; DEBUG_NEGO("RDP_NEG_REQ"); stream_read_uint8(s, flags); stream_read_uint16(s, length); stream_read_uint32(s, nego->requested_protocols); DEBUG_NEGO("requested_protocols: %d", nego->requested_protocols); nego->state = NEGO_STATE_FINAL; } /** * Process Negotiation Response from Connection Confirm message. * @param nego * @param s */ void nego_process_negotiation_response(rdpNego* nego, STREAM* s) { uint16 length; DEBUG_NEGO("RDP_NEG_RSP"); stream_read_uint8(s, nego->flags); stream_read_uint16(s, length); stream_read_uint32(s, nego->selected_protocol); nego->state = NEGO_STATE_FINAL; } /** * Process Negotiation Failure from Connection Confirm message. * @param nego * @param s */ void nego_process_negotiation_failure(rdpNego* nego, STREAM* s) { uint8 flags; uint16 length; uint32 failureCode; DEBUG_NEGO("RDP_NEG_FAILURE"); stream_read_uint8(s, flags); stream_read_uint16(s, length); stream_read_uint32(s, failureCode); switch (failureCode) { case SSL_REQUIRED_BY_SERVER: DEBUG_NEGO("Error: SSL_REQUIRED_BY_SERVER"); break; case SSL_NOT_ALLOWED_BY_SERVER: DEBUG_NEGO("Error: SSL_NOT_ALLOWED_BY_SERVER"); break; case SSL_CERT_NOT_ON_SERVER: DEBUG_NEGO("Error: SSL_CERT_NOT_ON_SERVER"); break; case INCONSISTENT_FLAGS: DEBUG_NEGO("Error: INCONSISTENT_FLAGS"); break; case HYBRID_REQUIRED_BY_SERVER: DEBUG_NEGO("Error: HYBRID_REQUIRED_BY_SERVER"); break; default: DEBUG_NEGO("Error: Unknown protocol security error %d", failureCode); break; } nego->state = NEGO_STATE_FAIL; } /** * Send RDP Negotiation Response (RDP_NEG_RSP).\n * @param nego */ boolean nego_send_negotiation_response(rdpNego* nego) { STREAM* s; uint8* bm; uint8* em; int length; boolean status; rdpSettings* settings; status = true; settings = nego->transport->settings; s = transport_send_stream_init(nego->transport, 256); length = TPDU_CONNECTION_CONFIRM_LENGTH; stream_get_mark(s, bm); stream_seek(s, length); if (nego->selected_protocol > PROTOCOL_RDP) { /* RDP_NEG_DATA must be present for TLS and NLA */ stream_write_uint8(s, TYPE_RDP_NEG_RSP); stream_write_uint8(s, EXTENDED_CLIENT_DATA_SUPPORTED); /* flags */ stream_write_uint16(s, 8); /* RDP_NEG_DATA length (8) */ stream_write_uint32(s, nego->selected_protocol); /* selectedProtocol */ length += 8; } else if (!settings->rdp_security) { stream_write_uint8(s, TYPE_RDP_NEG_FAILURE); stream_write_uint8(s, 0); /* flags */ stream_write_uint16(s, 8); /* RDP_NEG_DATA length (8) */ /* * TODO: Check for other possibilities, * like SSL_NOT_ALLOWED_BY_SERVER. */ printf("nego_send_negotiation_response: client supports only Standard RDP Security\n"); stream_write_uint32(s, SSL_REQUIRED_BY_SERVER); length += 8; status = false; } stream_get_mark(s, em); stream_set_mark(s, bm); tpkt_write_header(s, length); tpdu_write_connection_confirm(s, length - 5); stream_set_mark(s, em); if (transport_write(nego->transport, s) < 0) return false; if (status) { /* update settings with negotiated protocol security */ settings->requested_protocols = nego->requested_protocols; settings->selected_protocol = nego->selected_protocol; if (settings->selected_protocol == PROTOCOL_RDP) { settings->tls_security = false; settings->nla_security = false; settings->rdp_security = true; if (!settings->local) { settings->encryption = true; settings->encryption_method = ENCRYPTION_METHOD_40BIT | ENCRYPTION_METHOD_128BIT | ENCRYPTION_METHOD_FIPS; settings->encryption_level = ENCRYPTION_LEVEL_CLIENT_COMPATIBLE; } if (settings->encryption && settings->server_key == NULL && settings->rdp_key_file == NULL) return false; } else if (settings->selected_protocol == PROTOCOL_TLS) { settings->tls_security = true; settings->nla_security = false; settings->rdp_security = false; settings->encryption = false; settings->encryption_method = ENCRYPTION_METHOD_NONE; settings->encryption_level = ENCRYPTION_LEVEL_NONE; } else if (settings->selected_protocol == PROTOCOL_NLA) { settings->tls_security = true; settings->nla_security = true; settings->rdp_security = false; settings->encryption = false; settings->encryption_method = ENCRYPTION_METHOD_NONE; settings->encryption_level = ENCRYPTION_LEVEL_NONE; } } return status; } /** * Initialize NEGO state machine. * @param nego */ void nego_init(rdpNego* nego) { nego->state = NEGO_STATE_INITIAL; nego->requested_protocols = PROTOCOL_RDP; nego->transport->recv_callback = nego_recv; nego->transport->recv_extra = (void*) nego; nego->flags = 0; } /** * Create a new NEGO state machine instance. * @param transport * @return */ rdpNego* nego_new(struct rdp_transport * transport) { rdpNego* nego = (rdpNego*) xzalloc(sizeof(rdpNego)); if (nego != NULL) { nego->transport = transport; nego_init(nego); } return nego; } /** * Free NEGO state machine. * @param nego */ void nego_free(rdpNego* nego) { xfree(nego); } /** * Set target hostname and port. * @param nego * @param hostname * @param port */ void nego_set_target(rdpNego* nego, char* hostname, int port) { nego->hostname = hostname; nego->port = port; } /** * Enable security layer negotiation. * @param nego pointer to the negotiation structure * @param enable_rdp whether to enable security layer negotiation (true for enabled, false for disabled) */ void nego_set_negotiation_enabled(rdpNego* nego, boolean security_layer_negotiation_enabled) { DEBUG_NEGO("Enabling security layer negotiation: %s", security_layer_negotiation_enabled ? "true" : "false"); nego->security_layer_negotiation_enabled = security_layer_negotiation_enabled; } /** * Enable RDP security protocol. * @param nego pointer to the negotiation structure * @param enable_rdp whether to enable normal RDP protocol (true for enabled, false for disabled) */ void nego_enable_rdp(rdpNego* nego, boolean enable_rdp) { DEBUG_NEGO("Enabling RDP security: %s", enable_rdp ? "true" : "false"); nego->enabled_protocols[PROTOCOL_RDP] = enable_rdp; } /** * Enable TLS security protocol. * @param nego pointer to the negotiation structure * @param enable_tls whether to enable TLS + RDP protocol (true for enabled, false for disabled) */ void nego_enable_tls(rdpNego* nego, boolean enable_tls) { DEBUG_NEGO("Enabling TLS security: %s", enable_tls ? "true" : "false"); nego->enabled_protocols[PROTOCOL_TLS] = enable_tls; } /** * Enable NLA security protocol. * @param nego pointer to the negotiation structure * @param enable_nla whether to enable network level authentication protocol (true for enabled, false for disabled) */ void nego_enable_nla(rdpNego* nego, boolean enable_nla) { DEBUG_NEGO("Enabling NLA security: %s", enable_nla ? "true" : "false"); nego->enabled_protocols[PROTOCOL_NLA] = enable_nla; } /** * Set routing token. * @param nego * @param routing_token */ void nego_set_routing_token(rdpNego* nego, rdpBlob* routing_token) { nego->routing_token = routing_token; } /** * Set cookie. * @param nego * @param cookie */ void nego_set_cookie(rdpNego* nego, char* cookie) { nego->cookie = cookie; } /** * Enable / disable preconnection PDU. * @param nego * @param send_pcpdu */ void nego_set_send_preconnection_pdu(rdpNego* nego, boolean send_pcpdu) { nego->send_preconnection_pdu = send_pcpdu; } /** * Set preconnection id. * @param nego * @param id */ void nego_set_preconnection_id(rdpNego* nego, uint32 id) { nego->preconnection_id = id; } /** * Set preconnection blob. * @param nego * @param blob */ void nego_set_preconnection_blob(rdpNego* nego, char* blob) { nego->preconnection_blob = blob; }