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xrdp/sesman/scp_process.c

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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 "scp_process.h"
#include "sesman.h"
#include "sesman_access.h"
#include "sesman_auth.h"
#include "sesman_config.h"
#include "os_calls.h"
#include "pre_session_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 pre_session_item *psi)
{
int rv;
const char *peername;
rv = scp_get_set_peername_request(psi->client_trans, &peername);
if (rv == 0)
{
if (pre_session_list_set_peername(psi, peername) != 0)
{
LOG(LOG_LEVEL_WARNING,
"Failed to set connection peername from %s to %s",
psi->peername, peername);
}
}
return rv;
}
/******************************************************************************/
static int
process_sys_login_request(struct pre_session_item *psi)
{
int rv;
const char *username;
const char *password;
const char *ip_addr;
int send_client_reply = 1;
rv = scp_get_sys_login_request(psi->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",
psi->peername, username, ip_addr);
if (psi->login_state != E_PS_LOGIN_NOT_LOGGED_IN)
{
errorcode = E_SCP_LOGIN_ALREADY_LOGGED_IN;
LOG(LOG_LEVEL_ERROR, "Connection is already logged in for %s",
psi->username);
}
else if ((psi->username = g_strdup(username)) == NULL)
{
errorcode = E_SCP_LOGIN_NO_MEMORY;
LOG(LOG_LEVEL_ERROR, "Memory allocation failure logging in %s",
username);
}
else
{
/* 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(psi) != 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(psi->sesexec_trans,
username,
password,
ip_addr,
psi->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;
psi->dispatcher_action = E_PSD_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(psi->client_trans, errorcode, 1, -1);
psi->dispatcher_action = E_PSD_TERMINATE_PRE_SESSION;
}
}
return rv;
}
/******************************************************************************/
/**
* Authenticate and authorize a UDS connection
*
* @param psi 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, psi->username is non-NULL
*/
static enum scp_login_status
authenticate_and_authorize_uds_connection(struct pre_session_item *psi,
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 ((psi->username = g_strdup(username)) == NULL)
{
LOG(LOG_LEVEL_ERROR, "%s : Memory allocation failed",
__func__);
g_free(psi->username);
psi->username = NULL;
status = E_SCP_LOGIN_NO_MEMORY;
}
else
{
LOG(LOG_LEVEL_INFO, "Access permitted for user: %s",
username);
psi->login_state = E_PS_LOGIN_UDS;
psi->uid = uid;
psi->start_ip_addr[0] = '\0';
}
}
auth_end(auth_info);
}
return status;
}
/******************************************************************************/
static int
process_uds_login_request(struct pre_session_item *psi)
{
enum scp_login_status errorcode;
int rv;
int uid;
int pid;
char *username = NULL;
int server_closed;
rv = g_sck_get_peer_cred(psi->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)psi->client_trans->sck);
}
else
{
LOG(LOG_LEVEL_INFO,
"Received UDS login request from %s for UID: %d from PID: %d",
psi->peername, uid, pid);
if (psi->login_state != E_PS_LOGIN_NOT_LOGGED_IN)
{
errorcode = E_SCP_LOGIN_ALREADY_LOGGED_IN;
LOG(LOG_LEVEL_ERROR, "Connection is already logged in for %s",
psi->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(
psi, 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 */
psi->dispatcher_action = E_PSD_TERMINATE_PRE_SESSION;
/* Never return the UID if the server is closing */
uid = -1;
}
return scp_send_login_response(psi->client_trans, errorcode,
server_closed, uid);
}
/******************************************************************************/
static void
logout_pre_session(struct pre_session_item *psi)
{
if (psi->login_state != E_PS_LOGIN_NOT_LOGGED_IN)
{
(void)eicp_send_logout_request(psi->sesexec_trans);
trans_delete(psi->sesexec_trans);
psi->sesexec_trans = NULL;
psi->uid = (uid_t) -1;
g_free(psi->username);
psi->username = NULL;
psi->start_ip_addr[0] = '\0';
psi->login_state = E_PS_LOGIN_NOT_LOGGED_IN;
}
}
/******************************************************************************/
static int
process_logout_request(struct pre_session_item *psi)
{
if (psi->login_state != E_PS_LOGIN_NOT_LOGGED_IN)
{
LOG(LOG_LEVEL_INFO, "Logging out %s from sesman", psi->username);
logout_pre_session(psi);
}
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
}
/******************************************************************************/
static int
process_create_session_request(struct pre_session_item *psi)
{
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;
struct guid guid;
int display = 0;
struct session_item *s_item = NULL;
int send_client_reply = 1;
enum scp_screate_status status = E_SCP_SCREATE_OK;
rv = scp_get_create_session_request(psi->client_trans,
&type, &width, &height,
&bpp, &shell, &directory);
if (rv == 0)
{
if (psi->login_state == E_PS_LOGIN_NOT_LOGGED_IN)
{
status = E_SCP_SCREATE_NOT_LOGGED_IN;
}
else
{
LOG(LOG_LEVEL_INFO,
"Received request from %s to create a session for user %s",
psi->peername, psi->username);
s_item = session_list_get_bydata(psi->uid, type, width, height,
bpp, psi->start_ip_addr);
if (s_item != NULL)
{
// Found an existing session
display = s_item->display;
guid = s_item->guid;
// Tell the existing session to run the reconnect script.
// We ignore errors at this level, as any comms errors
// will be picked up in the main loop
(void)ercp_send_session_reconnect_event(s_item->sesexec_trans);
if (psi->start_ip_addr[0] != '\0')
{
LOG( LOG_LEVEL_INFO, "++ reconnected session: username %s, "
"display :%d.0, session_pid %d, ip %s",
psi->username, display,
s_item->sesexec_pid, psi->start_ip_addr);
}
else
{
LOG(LOG_LEVEL_INFO, "++ reconnected session: username %s, "
"display :%d.0, session_pid %d",
psi->username, display, s_item->sesexec_pid);
}
// If we created an authentication process for this SCP
// connection, close it gracefully
logout_pre_session(psi);
}
// Need to create a new session
else if (g_cfg->sess.max_sessions > 0 &&
session_list_get_count() >= g_cfg->sess.max_sessions)
{
status = E_SCP_SCREATE_MAX_REACHED;
}
else if ((display = session_list_get_available_display()) < 0)
{
status = E_SCP_SCREATE_NO_DISPLAY;
}
// Create an entry on the session list for the new session
else if ((s_item = session_list_new()) == NULL)
{
status = E_SCP_SCREATE_NO_MEMORY;
}
// Create a socket dir for this user
else if (create_xrdp_socket_path(psi->uid) != 0)
{
status = E_SCP_SCREATE_GENERAL_ERROR;
}
// Create a sesexec process if we don't have one (UDS login)
else if (psi->sesexec_trans == NULL && sesexec_start(psi) != 0)
{
LOG(LOG_LEVEL_ERROR,
"Can't start sesexec to manage session");
status = E_SCP_SCREATE_GENERAL_ERROR;
}
else
{
// Pass the session create request to sesexec
int eicp_stat;
eicp_stat = eicp_send_create_session_request(
psi->sesexec_trans,
psi->client_trans->sck,
display,
type, width, height,
bpp, shell, directory);
if (eicp_stat != 0)
{
LOG(LOG_LEVEL_ERROR,
"Can't ask sesexec to authenticate user");
status = E_SCP_SCREATE_GENERAL_ERROR;
}
else
{
// We've handed over responsibility for the
// SCP communication
send_client_reply = 0;
// Further comms from sesexec comes over the ERCP
// protocol
ercp_trans_from_eicp_trans(psi->sesexec_trans,
sesman_ercp_data_in,
(void *)s_item);
// Move the transport over to the session list item
s_item->sesexec_trans = psi->sesexec_trans;
s_item->sesexec_pid = psi->sesexec_pid;
psi->sesexec_trans = NULL;
psi->sesexec_pid = 0;
// Add the display to the session item so we don't try
// to allocate it to another session
s_item->display = display;
}
}
}
// Currently a create session request is the last thing on a
// connection, and results in automatic closure
//
// We may have passed the client_trans over to sesexec. If so,
// we can't send a reply here.
psi->dispatcher_action = E_PSD_TERMINATE_PRE_SESSION;
if (send_client_reply)
{
rv = scp_send_create_session_response(psi->client_trans,
status, display, &guid);
}
}
return rv;
}
/******************************************************************************/
static int
process_list_sessions_request(struct pre_session_item *psi)
{
int rv = 0;
struct scp_session_info *info = NULL;
unsigned int cnt = 0;
unsigned int i;
if (psi->login_state == E_PS_LOGIN_NOT_LOGGED_IN)
{
rv = scp_send_list_sessions_response(psi->client_trans,
E_SCP_LS_NOT_LOGGED_IN,
NULL);
}
else
{
LOG(LOG_LEVEL_INFO,
"Received request from %s to list sessions for user %s",
psi->peername, psi->username);
info = session_list_get_byuid(psi->uid, &cnt, 0);
for (i = 0; rv == 0 && i < cnt; ++i)
{
rv = scp_send_list_sessions_response(psi->client_trans,
E_SCP_LS_SESSION_INFO,
&info[i]);
}
free_session_info_list(info, cnt);
if (rv == 0)
{
rv = scp_send_list_sessions_response(psi->client_trans,
E_SCP_LS_END_OF_LIST,
NULL);
}
}
return rv;
}
/******************************************************************************/
static int
process_close_connection_request(struct pre_session_item *psi)
{
int rv = 0;
LOG(LOG_LEVEL_INFO, "Received request to close connection from %s",
psi->peername);
/* Expecting no more client messages. Close the connection
* after returning from this callback */
psi->dispatcher_action = E_PSD_TERMINATE_PRE_SESSION;
return rv;
}
/******************************************************************************/
int
scp_process(struct pre_session_item *psi)
{
enum scp_msg_code msgno;
int rv = 0;
switch ((msgno = scp_msg_in_get_msgno(psi->client_trans)))
{
case E_SCP_SET_PEERNAME_REQUEST:
rv = process_set_peername_request(psi);
break;
case E_SCP_SYS_LOGIN_REQUEST:
rv = process_sys_login_request(psi);
break;
case E_SCP_UDS_LOGIN_REQUEST:
rv = process_uds_login_request(psi);
break;
case E_SCP_LOGOUT_REQUEST:
rv = process_logout_request(psi);
break;
case E_SCP_CREATE_SESSION_REQUEST:
rv = process_create_session_request(psi);
break;
case E_SCP_LIST_SESSIONS_REQUEST:
rv = process_list_sessions_request(psi);
break;
case E_SCP_CLOSE_CONNECTION_REQUEST:
rv = process_close_connection_request(psi);
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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