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0edde4c0901b359a788590a5f4d28670cc3f0829
xrdp/sesman/scp_process.c
T
Leonard Nielsen 0edde4c090 Introduce instance_name field into xrdp.ini and xrdp-sesrun, along with 
the N policy in sesman.ini, allowing xrdp sessions to be tagged with an
instance name to enable persistent association with a specific
xrdp instance, to allow experiences where users reconnect to specific
sessions based on e.g. the xrdp listening port used.
2026-01-20 12:03:15 +01:00

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/**
* xrdp: A Remote Desktop Protocol server.
*
* Copyright (C) Jay Sorg 2004-2015
*
* 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.
*/
/**
*
* @file scp.c
* @brief scp (sesman control protocol) handler function
* @author Jay Sorg, Simone Fedele
*
*/
#if defined(HAVE_CONFIG_H)
#include <config_ac.h>
#endif
#include "trans.h"
#include "os_calls.h"
#include "eicp.h"
#include "ercp.h"
#include "scp.h"
#include "display_utils.h"
#include "scp_process.h"
#include "sesman.h"
#include "sesman_access.h"
#include "sesman_auth.h"
#include "sesman_config.h"
#include "os_calls.h"
#include "set_int.h"
#include "scp_list.h"
#include "session_list.h"
#include "sesexec_control.h"
#include "string_calls.h"
#include "xrdp_sockets.h"
/******************************************************************************/
static int
process_set_peername_request(struct scp_list_item *sli)
{
int rv;
const char *peername;
rv = scp_get_set_peername_request(sli->client_trans, &peername);
if (rv == 0)
{
if (scp_list_set_peername(sli, peername) != 0)
{
LOG(LOG_LEVEL_WARNING,
"Failed to set connection peername from %s to %s",
sli->peername, peername);
}
}
return rv;
}
/******************************************************************************/
static int
process_sys_login_request(struct scp_list_item *sli)
{
int rv;
const char *username;
const char *password;
const char *ip_addr;
int send_client_reply = 1;
rv = scp_get_sys_login_request(sli->client_trans, &username,
&password, &ip_addr);
if (rv == 0)
{
enum scp_login_status errorcode;
LOG(LOG_LEVEL_INFO,
"Received system login request from %s for user: %s IP: %s",
sli->peername, username, ip_addr);
if (sli->login_state != E_SLI_LOGIN_NOT_LOGGED_IN)
{
errorcode = E_SCP_LOGIN_ALREADY_LOGGED_IN;
LOG(LOG_LEVEL_ERROR, "Connection is already logged in for %s",
sli->username);
}
else if ((sli->username = g_strdup(username)) == NULL)
{
errorcode = E_SCP_LOGIN_NO_MEMORY;
LOG(LOG_LEVEL_ERROR, "Memory allocation failure logging in %s",
username);
}
else
{
/*
* Copy the IP address of the requesting user, anticipating a
* successful login. We need this so we can search for a session
* with a matching IP address if required.
*/
g_snprintf(sli->start_ip_addr, sizeof(sli->start_ip_addr),
"%s", ip_addr);
/* Create a sesexec process to handle the login
*
* We won't check for the user being valid here, as this might
* lead to information leakage */
if (sesexec_start(sli) != 0)
{
LOG(LOG_LEVEL_ERROR,
"Can't start sesexec to authenticate user");
errorcode = E_SCP_LOGIN_GENERAL_ERROR;
}
else
{
int eicp_stat;
eicp_stat = eicp_send_sys_login_request(sli->sesexec_trans,
username,
password,
ip_addr,
sli->client_trans->sck);
if (eicp_stat != 0)
{
LOG(LOG_LEVEL_ERROR,
"Can't ask sesexec to authenticate user");
errorcode = E_SCP_LOGIN_GENERAL_ERROR;
}
else
{
/* We've handed over responsibility for the
* SCP communication */
send_client_reply = 0;
sli->dispatcher_action = E_SLD_REMOVE_CLIENT_TRANS;
}
}
}
if (send_client_reply)
{
/* We only get here if something has gone
* wrong with the handover to sesexec */
rv = scp_send_login_response(sli->client_trans, errorcode, 1, -1);
sli->dispatcher_action = E_SLD_TERMINATE_SCP_CONN;
}
}
return rv;
}
/******************************************************************************/
/**
* Authenticate and authorize a UDS connection
*
* @param sli Connection to sesman
* @param uid UID for user
* @param username Name for user
* @return Status for the operation
*
* @post If E_SCP_LOGIN_OK is returned, sli->username is non-NULL
*/
static enum scp_login_status
authenticate_and_authorize_uds_connection(struct scp_list_item *sli,
int uid,
const char *username)
{
enum scp_login_status status = E_SCP_LOGIN_GENERAL_ERROR;
struct auth_info *auth_info = auth_uds(username, &status);
if (auth_info != NULL)
{
if (status != E_SCP_LOGIN_OK)
{
/* This shouldn't happen */
LOG(LOG_LEVEL_ERROR,
"Unexpected status return %d from auth_uds call",
(int)status);
}
else if (!access_login_allowed(&g_cfg->sec, username))
{
status = E_SCP_LOGIN_NOT_AUTHORIZED;
LOG(LOG_LEVEL_INFO, "Username okay but group problem for "
"user: %s", username);
}
/* If all is well, add info to the sesman connection for later use */
if (status == E_SCP_LOGIN_OK)
{
if ((sli->username = g_strdup(username)) == NULL)
{
LOG(LOG_LEVEL_ERROR, "%s : Memory allocation failed",
__func__);
g_free(sli->username);
sli->username = NULL;
status = E_SCP_LOGIN_NO_MEMORY;
}
else
{
sli->login_state = E_SLI_LOGIN_UDS;
sli->uid = uid;
sli->start_ip_addr[0] = '\0';
sli->is_admin = access_login_is_admin(&g_cfg->sec,
sli->username);
if (sli->is_admin)
{
LOG(LOG_LEVEL_INFO, "Admin access permitted for user: %s",
username);
}
else
{
LOG(LOG_LEVEL_INFO, "Normal access permitted for user: %s",
username);
}
}
}
auth_end(auth_info);
}
return status;
}
/******************************************************************************/
static int
process_uds_login_request(struct scp_list_item *sli)
{
enum scp_login_status errorcode;
int rv;
int uid;
int pid;
char *username = NULL;
int server_closed;
rv = g_sck_get_peer_cred(sli->client_trans->sck, &pid, &uid, NULL);
if (rv != 0)
{
errorcode = E_SCP_LOGIN_GENERAL_ERROR;
LOG(LOG_LEVEL_INFO,
"Unable to get peer credentials for socket %d",
(int)sli->client_trans->sck);
}
else
{
LOG(LOG_LEVEL_INFO,
"Received UDS login request from %s for UID: %d from PID: %d",
sli->peername, uid, pid);
if (sli->login_state != E_SLI_LOGIN_NOT_LOGGED_IN)
{
errorcode = E_SCP_LOGIN_ALREADY_LOGGED_IN;
LOG(LOG_LEVEL_ERROR, "Connection is already logged in for %s",
sli->username);
}
else if (g_getuser_info_by_uid(uid, &username,
NULL, NULL, NULL, NULL) != 0)
{
errorcode = E_SCP_LOGIN_GENERAL_ERROR;
LOG(LOG_LEVEL_ERROR, "Can't reverse lookup UID %d", uid);
}
else
{
errorcode = authenticate_and_authorize_uds_connection(
sli, uid, username);
g_free(username);
}
}
if (errorcode == E_SCP_LOGIN_OK)
{
server_closed = 0;
}
else
{
server_closed = 1;
/* Close the connection after returning from this callback */
sli->dispatcher_action = E_SLD_TERMINATE_SCP_CONN;
/* Never return the UID if the server is closing */
uid = -1;
}
return scp_send_login_response(sli->client_trans, errorcode,
server_closed, uid);
}
/******************************************************************************/
static void
logout_scp_list_item(struct scp_list_item *sli)
{
if (sli->login_state != E_SLI_LOGIN_NOT_LOGGED_IN)
{
if (sli->sesexec_trans != NULL)
{
(void)eicp_send_logout_request(sli->sesexec_trans);
trans_delete(sli->sesexec_trans);
sli->sesexec_trans = NULL;
}
sli->uid = (uid_t) -1;
g_free(sli->username);
sli->username = NULL;
sli->start_ip_addr[0] = '\0';
sli->login_state = E_SLI_LOGIN_NOT_LOGGED_IN;
}
}
/******************************************************************************/
static int
process_logout_request(struct scp_list_item *sli)
{
if (sli->login_state != E_SLI_LOGIN_NOT_LOGGED_IN)
{
LOG(LOG_LEVEL_INFO, "Logging out %s from sesman", sli->username);
logout_scp_list_item(sli);
}
return 0;
}
/******************************************************************************/
/**
* Create xrdp socket path for the user
*
* We do this here rather than in sesexec as we're single-threaded here
* and so don't have to worry about race conditions
*
* Directory is owned by UID of session, but can be accessed by
* the group specified in the config.
*
* Errors are logged so the caller doesn't have to
*/
static int
create_xrdp_socket_path(uid_t uid)
{
// Owner all permissions, group read+execute
#define RWX_PERMS 0x750
int rv = 1;
const char *sockdir_group = g_cfg->sec.session_sockdir_group;
int gid = 0; // Default if no group specified
char sockdir[XRDP_SOCKETS_MAXPATH];
g_snprintf(sockdir, sizeof(sockdir), XRDP_SOCKET_PATH, (int)uid);
// Create directory permissions RWX_PERMS, if it doesn't exist already
// (our os_calls layer doesn't allow us to set the SGID bit here)
int old_umask = g_umask_hex(RWX_PERMS ^ 0x777);
if (!g_directory_exist(sockdir) && !g_create_dir(sockdir))
{
LOG(LOG_LEVEL_ERROR,
"create_xrdp_socket_path: Can't create %s [%s]",
sockdir, g_get_strerror());
}
else if (g_chmod_hex(sockdir, RWX_PERMS | 0x2000) != 0)
{
LOG(LOG_LEVEL_ERROR,
"create_xrdp_socket_path: Can't set SGID bit on %s [%s]",
sockdir, g_get_strerror());
}
else if (sockdir_group != NULL && sockdir_group[0] != '\0' &&
g_getgroup_info(sockdir_group, &gid) != 0)
{
LOG(LOG_LEVEL_ERROR,
"create_xrdp_socket_path: Can't get GID of group %s [%s]",
sockdir_group, g_get_strerror());
}
else if (g_chown(sockdir, uid, gid) != 0)
{
LOG(LOG_LEVEL_ERROR,
"create_xrdp_socket_path: Can't set owner of %s to %d:%d [%s]",
sockdir, uid, gid, g_get_strerror());
}
else
{
rv = 0;
}
(void)g_umask_hex(old_umask);
return rv;
#undef RWX_PERMS
}
/******************************************************************************/
/*
* Gets a free display number
*
* We can't use displays either allocated to sessions, or being used to
* create sessions
*/
static int
get_free_display(void)
{
int result = -1;
struct set_int *alloc_displays;
alloc_displays = set_int_init(g_cfg->sess.x11_display_offset,
g_cfg->sess.max_display_number);
if (alloc_displays != NULL)
{
// Get all the displays either allocated to sessions, or
// potentially assigned to sessions on the SCP list
session_list_get_session_displays(alloc_displays);
scp_list_get_create_session_displays(alloc_displays);
// Find a free display, taking the allocated ones into account
result = display_utils_get_free_display(alloc_displays);
set_int_delete(alloc_displays);
}
return result;
}
/******************************************************************************/
static int
process_create_session_request(struct scp_list_item *sli)
{
int rv;
/* Client parameters describing new session */
enum scp_session_type type;
unsigned short width;
unsigned short height;
unsigned char bpp;
const char *shell;
const char *directory;
const char *instance_name;
struct guid guid;
int display = -1;
struct session_item *s_item = NULL;
int start_sesexec = (sli->sesexec_trans == NULL);
int send_client_reply = 1;
enum scp_screate_status status = E_SCP_SCREATE_OK;
rv = scp_get_create_session_request(sli->client_trans,
&type, &width, &height,
&bpp, &shell, &directory,
&instance_name);
if (rv == 0)
{
if (sli->login_state == E_SLI_LOGIN_NOT_LOGGED_IN)
{
status = E_SCP_SCREATE_NOT_LOGGED_IN;
}
else if (sli->create_session_in_progress)
{
status = E_SCP_SCREATE_IN_PROGRESS;
}
else
{
LOG(LOG_LEVEL_INFO,
"Received request from %s to create a session for user %s",
sli->peername, sli->username);
s_item = session_list_get_bydata(sli->uid, type, width, height,
bpp, sli->start_ip_addr, instance_name);
if (s_item != NULL)
{
// Found an existing session
LOG(LOG_LEVEL_INFO,
"A suitable session on display :%d is already active",
s_item->display);
display = s_item->display;
guid = s_item->guid;
}
// Need to create a new session
else if (g_cfg->sess.max_sessions > 0 &&
session_list_get_count() >= g_cfg->sess.max_sessions)
{
LOG(LOG_LEVEL_ERROR,
"The maximum number of sessions has been reached");
status = E_SCP_SCREATE_MAX_REACHED;
}
else if ((display = get_free_display()) < 0)
{
LOG(LOG_LEVEL_ERROR,
"No free display can be found for a new session");
status = E_SCP_SCREATE_NO_DISPLAY;
}
// Create a socket dir for this user
else if (create_xrdp_socket_path(sli->uid) != 0)
{
LOG(LOG_LEVEL_ERROR,
"Can't create a socket directory for UID %d",
(int)sli->uid);
status = E_SCP_SCREATE_GENERAL_ERROR;
}
// Create a sesexec process if we don't have one (UDS login)
else if (start_sesexec && sesexec_start(sli) != 0)
{
LOG(LOG_LEVEL_ERROR,
"Can't start sesexec to manage session");
status = E_SCP_SCREATE_GENERAL_ERROR;
}
else if (start_sesexec &&
eicp_send_uds_login_request(
sli->sesexec_trans, sli->client_trans->sck) != 0)
{
// Because we started sesexec late, we needed to log it in.
// That hasn't gone too well.
LOG(LOG_LEVEL_ERROR,
"Can't set UID for sesexec process");
status = E_SCP_SCREATE_GENERAL_ERROR;
// Looks like sesexec is broken...
trans_delete(sli->sesexec_trans);
sli->sesexec_trans = NULL;
}
else
{
// Pass the session create request to sesexec
LOG(LOG_LEVEL_INFO,
"Passing session creation request to sesexec");
int eicp_stat;
eicp_stat = eicp_send_create_session_request(
sli->sesexec_trans,
display,
type, width, height,
bpp, shell, directory,
instance_name);
if (eicp_stat != 0)
{
LOG(LOG_LEVEL_ERROR,
"Can't ask sesexec to create a session");
status = E_SCP_SCREATE_GENERAL_ERROR;
// Looks like sesexec is broken...
trans_delete(sli->sesexec_trans);
sli->sesexec_trans = NULL;
}
else
{
// We're not sending a reply yet
send_client_reply = 0;
sli->create_session_in_progress = 1;
sli->session_display = display; // Reserve display
}
}
}
if (send_client_reply)
{
if (status != E_SCP_SCREATE_OK)
{
display = -1;
guid_clear(&guid);
}
rv = scp_send_create_session_response(sli->client_trans,
status, display, &guid);
}
}
return rv;
}
/******************************************************************************/
static int
process_connect_session_request(struct scp_list_item *sli)
{
int rv;
/* Client parameters describing new session */
struct guid guid;
const char *client_ip;
const char *client_name;
unsigned int flags;
enum scp_sconnect_status status = E_SCP_SCONNECT_OK;
rv = scp_get_connect_session_request(sli->client_trans, &guid,
&client_ip, &client_name, &flags);
if (rv == 0)
{
if (sli->login_state == E_SLI_LOGIN_NOT_LOGGED_IN)
{
status = E_SCP_SCONNECT_NOT_LOGGED_IN;
}
else
{
struct session_item *s_item = session_list_get_byguid(&guid);
if (s_item == NULL)
{
LOG(LOG_LEVEL_ERROR,
"User %s tried to connect to non-existent session",
sli->username);
status = E_SCP_SCONNECT_NO_SUCH_GUID;
}
else if (s_item->uid != sli->uid)
{
LOG(LOG_LEVEL_ERROR,
"User %s (UID %d) denied access to session for UID %d",
sli->username, sli->uid, s_item->uid);
status = E_SCP_SCONNECT_NO_SUCH_GUID;
}
else
{
// Don't log the GUID
LOG(LOG_LEVEL_INFO,
"Forwarding request from %s to connect to a session",
sli->username);
// Pass the session create request to sesexec
int ercp_stat;
ercp_stat = ercp_send_connect_session_request(
s_item->sesexec_trans,
sli->client_trans->sck,
client_ip,
client_name,
flags);
if (ercp_stat != 0)
{
// The sesexec transport is broken. That's dealt with
// elsewhere.
LOG(LOG_LEVEL_ERROR,
"Can't ask sesexec to connect to a session");
status = E_SCP_SCONNECT_GENERAL_ERROR;
}
else
{
status = E_SCP_SCONNECT_OK;
}
}
}
// Send anything other than a successful connection request
// back to the client
if (status != E_SCP_SCONNECT_OK)
{
rv = scp_send_connect_session_response(sli->client_trans,
status, -1, -1);
}
}
// This call is always the last thing on the SCP connection.
logout_scp_list_item(sli); // Remove any sesexec process used for auth
sli->dispatcher_action = E_SLD_TERMINATE_SCP_CONN;
return rv;
}
/******************************************************************************/
static int
process_list_sessions_request(struct scp_list_item *sli)
{
int rv = 0;
struct scp_session_info *info = NULL;
unsigned int cnt = 0;
unsigned int i;
if (sli->login_state == E_SLI_LOGIN_NOT_LOGGED_IN)
{
rv = scp_send_list_sessions_response(sli->client_trans,
E_SCP_LS_NOT_LOGGED_IN,
NULL);
}
else
{
LOG(LOG_LEVEL_INFO,
"Received request from %s to list sessions for user %s",
sli->peername, sli->username);
if (sli->is_admin)
{
info = session_list_get_byuid(NULL, &cnt, 0);
}
else
{
info = session_list_get_byuid(&sli->uid, &cnt, 0);
}
for (i = 0; rv == 0 && i < cnt; ++i)
{
rv = scp_send_list_sessions_response(sli->client_trans,
E_SCP_LS_SESSION_INFO,
&info[i]);
}
free_session_info_list(info, cnt);
if (rv == 0)
{
rv = scp_send_list_sessions_response(sli->client_trans,
E_SCP_LS_END_OF_LIST,
NULL);
}
}
return rv;
}
/******************************************************************************/
static int
process_create_sockdir_request(struct scp_list_item *sli)
{
enum scp_create_sockdir_status status = E_SCP_CS_OTHER_ERROR;
if (sli->login_state == E_SLI_LOGIN_NOT_LOGGED_IN)
{
status = E_SCP_CS_NOT_LOGGED_IN;
}
else
{
LOG(LOG_LEVEL_INFO,
"Received request from %s to create sockdir for user %s",
sli->peername, sli->username);
if (create_xrdp_socket_path(sli->uid) == 0)
{
status = E_SCP_CS_OK;
}
}
return scp_send_create_sockdir_response(sli->client_trans, status);
}
/******************************************************************************/
static int
process_close_connection_request(struct scp_list_item *sli)
{
int rv = 0;
LOG(LOG_LEVEL_INFO, "Received request to close connection from %s",
sli->peername);
/* Make sure we're logged out */
if (sli->login_state != E_SLI_LOGIN_NOT_LOGGED_IN)
{
logout_scp_list_item(sli);
}
/* Expecting no more client messages. Close the connection
* after returning from this callback */
sli->dispatcher_action = E_SLD_TERMINATE_SCP_CONN;
return rv;
}
/******************************************************************************/
int
scp_process(struct scp_list_item *sli)
{
enum scp_msg_code msgno;
int rv = 0;
switch ((msgno = scp_msg_in_get_msgno(sli->client_trans)))
{
case E_SCP_SET_PEERNAME_REQUEST:
rv = process_set_peername_request(sli);
break;
case E_SCP_SYS_LOGIN_REQUEST:
rv = process_sys_login_request(sli);
break;
case E_SCP_UDS_LOGIN_REQUEST:
rv = process_uds_login_request(sli);
break;
case E_SCP_LOGOUT_REQUEST:
rv = process_logout_request(sli);
break;
case E_SCP_CREATE_SESSION_REQUEST:
rv = process_create_session_request(sli);
break;
case E_SCP_CONNECT_SESSION_REQUEST:
rv = process_connect_session_request(sli);
break;
case E_SCP_LIST_SESSIONS_REQUEST:
rv = process_list_sessions_request(sli);
break;
case E_SCP_CREATE_SOCKDIR_REQUEST:
rv = process_create_sockdir_request(sli);
break;
case E_SCP_CLOSE_CONNECTION_REQUEST:
rv = process_close_connection_request(sli);
break;
default:
{
char buff[64];
scp_msgno_to_str(msgno, buff, sizeof(buff));
LOG(LOG_LEVEL_ERROR, "Ignored SCP message %s", buff);
}
}
return rv;
}
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