/* Establish a connection up to the ISO layer */
RD_BOOL
iso_connect(char *server, char *username, RD_BOOL reconnect, uint32 * selected_protocol)
{
STREAM s;
uint8 code;
g_negotiate_rdp_protocol = True;
retry:
*selected_protocol = PROTOCOL_RDP;
code = 0;
if (!tcp_connect(server))
return False;
if (reconnect)
{
iso_send_msg(ISO_PDU_CR);
}
else
{
iso_send_connection_request(username);
}
s = iso_recv_msg(&code, NULL);
if (s == NULL)
return False;
if (code != ISO_PDU_CC)
{
error("expected CC, got 0x%x\n", code);
tcp_disconnect();
return False;
}
if (g_rdp_version >= RDP_V5 && s_check_rem(s, 8))
{
/* handle RDP_NEG_REQ response */
const char *reason = NULL;
uint8 type = 0, flags = 0;
uint16 length = 0;
uint32 data = 0;
in_uint8(s, type);
in_uint8(s, flags);
in_uint16(s, length);
in_uint32(s, data);
if (type == RDP_NEG_FAILURE)
{
switch (data)
{
case SSL_REQUIRED_BY_SERVER:
reason = "SSL required by server";
break;
case SSL_WITH_USER_AUTH_REQUIRED_BY_SERVER:
reason = "SSL with user authentication required by server";
break;
case SSL_NOT_ALLOWED_BY_SERVER:
reason = "SSL not allowed by server";
break;
case SSL_CERT_NOT_ON_SERVER:
reason = "SSL certificated not on server";
break;
case INCONSISTENT_FLAGS:
reason = "inconsistent flags";
break;
case HYBRID_REQUIRED_BY_SERVER:
reason = "hybrid authentication (CredSSP) required by server";
break;
default:
reason = "unknown reason";
}
tcp_disconnect();
warning("RDP protocol negotiation failed with reason: %s (error 0x%x),\n",
reason, data);
warning("retrying without negotiation using plain RDP protocol.\n");
g_negotiate_rdp_protocol = False;
goto retry;
}
if (type != RDP_NEG_RSP)
{
tcp_disconnect();
error("expected RDP_NEG_RSP, got type = 0x%x\n", type);
warning("retrying without negotiation using plain RDP protocol.\n");
g_negotiate_rdp_protocol = False;
goto retry;
}
/* handle negotiation response */
if (data == PROTOCOL_SSL)
{
DEBUGMSG(1,(L"iso_connect: negotiation: PROTOCOL_SSL\n"));
if (!tcp_tls_connect())
{
tcp_disconnect();
DEBUGMSG(1,(L"iso_connect: negotiation: PROTOCOL_SSL FAILED\n"));
return False;
}
/* do not use encryption when using TLS */
g_encryption = False;
}
else if (data != PROTOCOL_RDP)
{
tcp_disconnect();
error("unexpected protocol in neqotiation response, got data = 0x%x.\n",
data);
return False;
}
*selected_protocol = data;
}
return True;
}
RD_BOOL
cssp_connect(char *server, char *user, char *domain, char *password, STREAM s)
{
OM_uint32 actual_time;
gss_cred_id_t cred;
gss_buffer_desc input_tok, output_tok;
gss_name_t target_name;
OM_uint32 major_status, minor_status;
int context_established = 0;
gss_ctx_id_t gss_ctx;
gss_OID desired_mech = &_gss_spnego_krb5_mechanism_oid_desc;
STREAM ts_creds;
struct stream token = { 0 };
struct stream pubkey = { 0 };
struct stream pubkey_cmp = { 0 };
// Verify that system gss support spnego
if (!cssp_gss_mech_available(desired_mech))
{
warning("CredSSP: System doesn't have support for desired authentication mechanism.\n");
return False;
}
// Get service name
if (!cssp_gss_get_service_name(server, &target_name))
{
warning("CredSSP: Failed to get target service name.\n");
return False;
}
// Establish tls connection to server
if (!tcp_tls_connect())
{
warning("CredSSP: Failed to establish TLS connection.\n");
return False;
}
tcp_tls_get_server_pubkey(&pubkey);
#ifdef WITH_DEBUG_CREDSSP
streamsave(&pubkey, "PubKey.raw");
#endif
// Enter the spnego loop
OM_uint32 actual_services;
gss_OID actual_mech;
struct stream blob = { 0 };
gss_ctx = GSS_C_NO_CONTEXT;
cred = GSS_C_NO_CREDENTIAL;
input_tok.length = 0;
output_tok.length = 0;
minor_status = 0;
int i = 0;
do
{
major_status = gss_init_sec_context(&minor_status,
cred,
&gss_ctx,
target_name,
desired_mech,
GSS_C_MUTUAL_FLAG | GSS_C_DELEG_FLAG,
GSS_C_INDEFINITE,
GSS_C_NO_CHANNEL_BINDINGS,
&input_tok,
&actual_mech,
&output_tok, &actual_services, &actual_time);
if (GSS_ERROR(major_status))
{
if (i == 0)
error("CredSSP: Initialize failed, do you have correct kerberos tgt initialized ?\n");
else
error("CredSSP: Negotiation failed.\n");
#ifdef WITH_DEBUG_CREDSSP
cssp_gss_report_error(GSS_C_GSS_CODE, "CredSSP: SPNEGO negotiation failed.",
major_status, minor_status);
#endif
goto bail_out;
}
// validate required services
if (!(actual_services & GSS_C_CONF_FLAG))
{
error("CredSSP: Confidiality service required but is not available.\n");
goto bail_out;
}
// Send token to server
if (output_tok.length != 0)
{
if (output_tok.length > token.size)
s_realloc(&token, output_tok.length);
s_reset(&token);
out_uint8p(&token, output_tok.value, output_tok.length);
s_mark_end(&token);
if (!cssp_send_tsrequest(&token, NULL, NULL))
goto bail_out;
(void) gss_release_buffer(&minor_status, &output_tok);
}
// Read token from server
if (major_status & GSS_S_CONTINUE_NEEDED)
{
(void) gss_release_buffer(&minor_status, &input_tok);
if (!cssp_read_tsrequest(&token, NULL))
goto bail_out;
input_tok.value = token.data;
input_tok.length = s_length(&token);
}
else
{
// Send encrypted pubkey for verification to server
context_established = 1;
if (!cssp_gss_wrap(gss_ctx, &pubkey, &blob))
goto bail_out;
if (!cssp_send_tsrequest(NULL, NULL, &blob))
goto bail_out;
context_established = 1;
}
i++;
}
while (!context_established);
// read tsrequest response and decrypt for public key validation
if (!cssp_read_tsrequest(NULL, &blob))
goto bail_out;
if (!cssp_gss_unwrap(gss_ctx, &blob, &pubkey_cmp))
goto bail_out;
pubkey_cmp.data[0] -= 1;
// validate public key
if (memcmp(pubkey.data, pubkey_cmp.data, s_length(&pubkey)) != 0)
{
error("CredSSP: Cannot guarantee integrity of server connection, MITM ? "
"(public key data mismatch)\n");
goto bail_out;
}
// Send TSCredentials
ts_creds = cssp_encode_tscredentials(user, password, domain);
if (!cssp_gss_wrap(gss_ctx, ts_creds, &blob))
goto bail_out;
s_free(ts_creds);
if (!cssp_send_tsrequest(NULL, &blob, NULL))
goto bail_out;
return True;
bail_out:
xfree(token.data);
return False;
}
/* Establish a connection up to the ISO layer */
RD_BOOL
iso_connect(char *server, char *username, char *domain, char *password,
RD_BOOL reconnect, uint32 * selected_protocol)
{
STREAM s;
uint8 code;
uint32 neg_proto;
g_negotiate_rdp_protocol = True;
neg_proto = PROTOCOL_SSL;
#ifdef WITH_CREDSSP
if (!g_use_password_as_pin)
neg_proto |= PROTOCOL_HYBRID;
else if (g_sc_csp_name || g_sc_reader_name || g_sc_card_name || g_sc_container_name)
neg_proto |= PROTOCOL_HYBRID;
else
warning("Disables CredSSP due to missing smartcard information for SSO.\n");
#endif
retry:
*selected_protocol = PROTOCOL_RDP;
code = 0;
if (!tcp_connect(server))
return False;
iso_send_connection_request(username, neg_proto);
s = iso_recv_msg(&code, NULL);
if (s == NULL)
return False;
if (code != ISO_PDU_CC)
{
error("expected CC, got 0x%x\n", code);
tcp_disconnect();
return False;
}
if (g_rdp_version >= RDP_V5 && s_check_rem(s, 8))
{
/* handle RDP_NEG_REQ response */
const char *reason = NULL;
uint8 type = 0, flags = 0;
uint16 length = 0;
uint32 data = 0;
in_uint8(s, type);
in_uint8(s, flags);
in_uint16(s, length);
in_uint32(s, data);
if (type == RDP_NEG_FAILURE)
{
RD_BOOL retry_without_neg = False;
switch (data)
{
case SSL_WITH_USER_AUTH_REQUIRED_BY_SERVER:
reason = "SSL with user authentication required by server";
break;
case SSL_NOT_ALLOWED_BY_SERVER:
reason = "SSL not allowed by server";
retry_without_neg = True;
break;
case SSL_CERT_NOT_ON_SERVER:
reason = "no valid authentication certificate on server";
retry_without_neg = True;
break;
case INCONSISTENT_FLAGS:
reason = "inconsistent negotiation flags";
break;
case SSL_REQUIRED_BY_SERVER:
reason = "SSL required by server";
break;
case HYBRID_REQUIRED_BY_SERVER:
reason = "CredSSP required by server";
break;
default:
reason = "unknown reason";
}
tcp_disconnect();
if (retry_without_neg)
{
fprintf(stderr,
"Failed to negotiate protocol, retrying with plain RDP.\n");
g_negotiate_rdp_protocol = False;
goto retry;
}
fprintf(stderr, "Failed to connect, %s.\n", reason);
return False;
}
if (type != RDP_NEG_RSP)
{
tcp_disconnect();
error("Expected RDP_NEG_RSP, got type = 0x%x\n", type);
return False;
}
/* handle negotiation response */
if (data == PROTOCOL_SSL)
{
if (!tcp_tls_connect())
{
/* failed to connect using cssp, let retry with plain TLS */
tcp_disconnect();
neg_proto = PROTOCOL_RDP;
goto retry;
}
/* do not use encryption when using TLS */
g_encryption = False;
fprintf(stderr, "Connection established using SSL.\n");
}
#ifdef WITH_CREDSSP
else if (data == PROTOCOL_HYBRID)
{
if (!cssp_connect(server, username, domain, password, s))
{
/* failed to connect using cssp, let retry with plain TLS */
tcp_disconnect();
neg_proto = PROTOCOL_SSL;
goto retry;
}
/* do not use encryption when using TLS */
fprintf(stderr, "Connection established using CredSSP.\n");
g_encryption = False;
}
#endif
else if (data == PROTOCOL_RDP)
{
fprintf(stderr, "Connection established using plain RDP.\n");
}
else if (data != PROTOCOL_RDP)
{
tcp_disconnect();
error("Unexpected protocol in negotiation response, got data = 0x%x.\n",
data);
return False;
}
*selected_protocol = data;
}
return True;
}
