Parameterise the sockdir with the UID of the user

The top level socket directory is now called XRDP_SOCKET_ROOT_PATH.
Below that are user-specific directories referred to with the
XRDP_SOCKET_PATH macro - this name is hard-coded into xorgxrdp and
the audio modules as an environment variable.

XRDP_SOCKET_PATH now looks like $XRDP_SOCKET_ROOT_PATH/<uid>

XRDP_SOCKET_PATH is only writeable by the user, and readable by the user
and the xrdp process.

common/xrdp_sockets.h

@@ -21,16 +21,31 @@
 #if !defined(XRDP_SOCKETS_H)
 #define XRDP_SOCKETS_H
 
-/* basename of socket files */
+/* Buffer size for code for fullpath declarations
+ *
+ * This needs to fit in the sun_path field of a sockaddr_un. POSIX
+ * does not define this size, so the value below is the lower of
+ * the FreeBSD/OpenBSD/NetBSD(104) and Linux(108) values */
+#define XRDP_SOCKETS_MAXPATH 104
+
+/* The socketdir is rooted at XRDP_SOCKET_ROOT_PATH. User-specific
+ * sockets live in a user-specific sub-directory of this called
+ * XRDP_SOCKET_PATH. The sub-directory is the UID of the user */
+#define XRDP_SOCKET_PATH      XRDP_SOCKET_ROOT_PATH "/%d"
+
+/* Sockets in XRDP_SOCKET_ROOT_PATH */
+#define SCP_LISTEN_PORT_BASE_STR   "sesman.socket"
+
+/* names of socket files within XRDP_SOCKET_PATH, qualified by
+ * display number */
 #define XRDP_CHANSRV_BASE_STR      "xrdp_chansrv_socket_%d"
 #define CHANSRV_PORT_OUT_BASE_STR  "xrdp_chansrv_audio_out_socket_%d"
 #define CHANSRV_PORT_IN_BASE_STR   "xrdp_chansrv_audio_in_socket_%d"
 #define CHANSRV_API_BASE_STR       "xrdpapi_%d"
 #define XRDP_X11RDP_BASE_STR       "xrdp_display_%d"
 #define XRDP_DISCONNECT_BASE_STR   "xrdp_disconnect_display_%d"
-#define SCP_LISTEN_PORT_BASE_STR   "sesman.socket"
 
-/* fullpath of sockets */
+/* fullpath declarations */
 #define XRDP_CHANSRV_STR      XRDP_SOCKET_PATH "/" XRDP_CHANSRV_BASE_STR
 #define CHANSRV_PORT_OUT_STR  XRDP_SOCKET_PATH "/" CHANSRV_PORT_OUT_BASE_STR
 #define CHANSRV_PORT_IN_STR   XRDP_SOCKET_PATH "/" CHANSRV_PORT_IN_BASE_STR

docs/man/sesman.ini.5.in

@@ -312,6 +312,11 @@ to a setuid Xorg executable. However, if a kernel security module (such as
 AppArmor) is used to confine xrdp, \fIno_new_privs\fR may interfere with
 transitions between confinement domains.
 
+.TP
+\fBSessionSockdirGroup\fR=\fIgroup\fR
+Sets the group owner of the directories containing session sockets. This
+is normally the GID of the xrdp process so xrdp can connect to user sessions.
+
 .SH "X11 SERVER"
 Following parameters can be used in the \fB[Xvnc]\fR and
 \fB[Xorg]\fR sections.

libipm/scp.c

@@ -332,37 +332,50 @@ scp_get_sys_login_request(struct trans *trans,
 int
 scp_send_login_response(struct trans *trans,
                         enum scp_login_status login_result,
-                        int server_closed)
+                        int server_closed,
+                        int uid)
 {
     return libipm_msg_out_simple_send(
                trans,
                (int)E_SCP_LOGIN_RESPONSE,
-               "ib",
+               "ibi",
                login_result,
-               (server_closed != 0)); /* Convert to 0/1 */
+               (server_closed != 0), /* Convert to 0/1 */
+               uid);
 }
 
 /*****************************************************************************/
 
 int
 scp_get_login_response(struct trans *trans,
                        enum scp_login_status *login_result,
-                       int *server_closed)
+                       int *server_closed,
+                       int *uid)
 {
     int32_t i_login_result = 0;
+    int32_t i_uid = 0;
     int dummy;
+
     /* User can pass in NULL for server_closed if they're trying an
-     * login method like UDS for which all fails are fatal */
+     * login method like UDS for which all fails are fatal. Likewise
+     * they may be uninterested in the uid */
     if (server_closed == NULL)
     {
         server_closed = &dummy;
     }
+    if (uid == NULL)
+    {
+        uid = &dummy;
+    }
 
-    int rv = libipm_msg_in_parse(trans, "ib", &i_login_result, server_closed);
+    int rv = libipm_msg_in_parse(trans, "ibi",
+                                 &i_login_result, server_closed, &i_uid);
     if (rv == 0)
     {
         *login_result = (enum scp_login_status)i_login_result;
+        *uid = i_uid;
     }
+
     return rv;
 }
 

libipm/scp.h

@@ -284,12 +284,14 @@ scp_get_sys_login_request(struct trans *trans,
  * @param login_result What happened to the login
  * @param server_closed If login fails, whether server has closed connection.
  *        If not, a retry can be made.
+ * @param uid UID for a successful login
  * @return != 0 for error
  */
 int
 scp_send_login_response(struct trans *trans,
                         enum scp_login_status login_result,
-                        int server_closed);
+                        int server_closed,
+                        int uid);
 
 /**
  * Parses an incoming E_SCP_LOGIN_RESPONSE (SCP client)
@@ -298,12 +300,17 @@ scp_send_login_response(struct trans *trans,
  * @param[out] login_result 0 for success, PAM error code otherwise
  * @param[out] server_closed If login fails, whether server has closed
  *             connection. If not a retry can be made.
+ * @param[out] uid UID for a successful login
+ *
+ * server_closed and uid can be passed NULL if the caller isn't interested.
+ *
  * @return != 0 for error
  */
 int
 scp_get_login_response(struct trans *trans,
                        enum scp_login_status *login_result,
-                       int *server_closed);
+                       int *server_closed,
+                       int *uid);
 
 /**
  * Send an E_SCP_LOGOUT_REQUEST (SCP client)

sesman/chansrv/Makefile.am

@@ -8,7 +8,7 @@ AM_CPPFLAGS = \
   -DXRDP_SBIN_PATH=\"${sbindir}\" \
   -DXRDP_SHARE_PATH=\"${datadir}/xrdp\" \
   -DXRDP_PID_PATH=\"${localstatedir}/run\" \
-  -DXRDP_SOCKET_PATH=\"${socketdir}\" \
+  -DXRDP_SOCKET_ROOT_PATH=\"${socketdir}\" \
   -I$(top_srcdir)/sesman/libsesman \
   -I$(top_srcdir)/common
 

sesman/chansrv/chansrv.c

@@ -1238,7 +1238,7 @@ my_api_trans_conn_in(struct trans *trans, struct trans *new_trans)
 static int
 setup_listen(void)
 {
-    char port[256];
+    char port[XRDP_SOCKETS_MAXPATH];
     int error = 0;
 
     if (g_lis_trans != 0)
@@ -1248,7 +1248,7 @@ setup_listen(void)
 
     g_lis_trans = trans_create(TRANS_MODE_UNIX, 8192, 8192);
     g_lis_trans->is_term = g_is_term;
-    g_snprintf(port, 255, XRDP_CHANSRV_STR, g_display_num);
+    g_snprintf(port, sizeof(port), XRDP_CHANSRV_STR, g_getuid(), g_display_num);
 
     g_lis_trans->trans_conn_in = my_trans_conn_in;
     error = trans_listen(g_lis_trans, port);
@@ -1267,12 +1267,12 @@ setup_listen(void)
 static int
 setup_api_listen(void)
 {
-    char port[256];
+    char port[XRDP_SOCKETS_MAXPATH];
     int error = 0;
 
     g_api_lis_trans = trans_create(TRANS_MODE_UNIX, 8192 * 4, 8192 * 4);
     g_api_lis_trans->is_term = g_is_term;
-    g_snprintf(port, 255, CHANSRV_API_STR, g_display_num);
+    g_snprintf(port, sizeof(port), CHANSRV_API_STR, g_getuid(), g_display_num);
     g_api_lis_trans->trans_conn_in = my_api_trans_conn_in;
     error = trans_listen(g_api_lis_trans, port);
 

sesman/chansrv/sound.c

@@ -1894,11 +1894,11 @@ sound_sndsrvr_source_data_in(struct trans *trans)
 static int
 sound_start_source_listener(void)
 {
-    char port[1024];
+    char port[XRDP_SOCKETS_MAXPATH];
 
     g_audio_l_trans_in = trans_create(TRANS_MODE_UNIX, 128 * 1024, 8192);
     g_audio_l_trans_in->is_term = g_is_term;
-    g_snprintf(port, 255, CHANSRV_PORT_IN_STR, g_display_num);
+    g_snprintf(port, sizeof(port), CHANSRV_PORT_IN_STR, g_getuid(), g_display_num);
     g_audio_l_trans_in->trans_conn_in = sound_sndsrvr_source_conn_in;
     if (trans_listen(g_audio_l_trans_in, port) != 0)
     {
@@ -1913,11 +1913,11 @@ sound_start_source_listener(void)
 static int
 sound_start_sink_listener(void)
 {
-    char port[1024];
+    char port[XRDP_SOCKETS_MAXPATH];
 
     g_audio_l_trans_out = trans_create(TRANS_MODE_UNIX, 128 * 1024, 8192);
     g_audio_l_trans_out->is_term = g_is_term;
-    g_snprintf(port, 255, CHANSRV_PORT_OUT_STR, g_display_num);
+    g_snprintf(port, sizeof(port), CHANSRV_PORT_OUT_STR, g_getuid(), g_display_num);
     g_audio_l_trans_out->trans_conn_in = sound_sndsrvr_sink_conn_in;
     if (trans_listen(g_audio_l_trans_out, port) != 0)
     {

sesman/libsesman/sesman_config.c

@@ -71,6 +71,7 @@
 #define SESMAN_CFG_SEC_RESTRICT_INBOUND_CLIPBOARD  "RestrictInboundClipboard"
 #define SESMAN_CFG_SEC_ALLOW_ALTERNATE_SHELL       "AllowAlternateShell"
 #define SESMAN_CFG_SEC_XORG_NO_NEW_PRIVILEGES      "XorgNoNewPrivileges"
+#define SESMAN_CFG_SEC_SESSION_SOCKDIR_GROUP       "SessionSockdirGroup"
 
 #define SESMAN_CFG_SESSIONS          "Sessions"
 #define SESMAN_CFG_SESS_MAX          "MaxSessions"
@@ -298,7 +299,6 @@ config_read_security(int file, struct config_security *sc,
 {
     int i;
     int gid;
-    char *buf;
 
     list_clear(param_v);
     list_clear(param_n);
@@ -312,46 +312,44 @@ config_read_security(int file, struct config_security *sc,
     sc->restrict_inbound_clipboard = 0;
     sc->allow_alternate_shell = 1;
     sc->xorg_no_new_privileges = 1;
+    sc->session_sockdir_group = 0;
 
     file_read_section(file, SESMAN_CFG_SECURITY, param_n, param_v);
 
     for (i = 0; i < param_n->count; i++)
     {
-        buf = (char *)list_get_item(param_n, i);
+        const char *param = (const char *)list_get_item(param_n, i);
+        const char *val = (const char *)list_get_item(param_v, i);
 
-        if (0 == g_strcasecmp(buf, SESMAN_CFG_SEC_ALLOW_ROOT))
+        if (0 == g_strcasecmp(param, SESMAN_CFG_SEC_ALLOW_ROOT))
         {
-            sc->allow_root = g_text2bool((char *)list_get_item(param_v, i));
+            sc->allow_root = g_text2bool(val);
         }
-
-        if (0 == g_strcasecmp(buf, SESMAN_CFG_SEC_LOGIN_RETRY))
+        else if (0 == g_strcasecmp(param, SESMAN_CFG_SEC_LOGIN_RETRY))
         {
-            sc->login_retry = g_atoi((char *)list_get_item(param_v, i));
+            sc->login_retry = g_atoi(val);
         }
-
-        if (0 == g_strcasecmp(buf, SESMAN_CFG_SEC_USR_GROUP))
+        else if (0 == g_strcasecmp(param, SESMAN_CFG_SEC_USR_GROUP))
         {
-            if (g_getgroup_info((char *)list_get_item(param_v, i), &gid) == 0)
+            if (g_getgroup_info(val, &gid) == 0)
             {
                 sc->ts_users_enable = 1;
                 sc->ts_users = gid;
             }
         }
-
-        if (0 == g_strcasecmp(buf, SESMAN_CFG_SEC_ADM_GROUP))
+        else if (0 == g_strcasecmp(param, SESMAN_CFG_SEC_ADM_GROUP))
         {
-            if (g_getgroup_info((char *)list_get_item(param_v, i), &gid) == 0)
+            if (g_getgroup_info(val, &gid) == 0)
             {
                 sc->ts_admins_enable = 1;
                 sc->ts_admins = gid;
             }
         }
-        if (0 == g_strcasecmp(buf, SESMAN_CFG_SEC_ALWAYSGROUPCHECK))
+        else if (0 == g_strcasecmp(param, SESMAN_CFG_SEC_ALWAYSGROUPCHECK))
         {
-            sc->ts_always_group_check = g_text2bool((char *)list_get_item(param_v, i));
+            sc->ts_always_group_check = g_text2bool(val);
         }
-
-        if (0 == g_strcasecmp(buf, SESMAN_CFG_SEC_RESTRICT_OUTBOUND_CLIPBOARD))
+        else if (0 == g_strcasecmp(param, SESMAN_CFG_SEC_RESTRICT_OUTBOUND_CLIPBOARD))
         {
             char unrecognised[256];
             sc->restrict_outbound_clipboard =
@@ -365,7 +363,7 @@ config_read_security(int file, struct config_security *sc,
                     unrecognised);
             }
         }
-        if (0 == g_strcasecmp(buf, SESMAN_CFG_SEC_RESTRICT_INBOUND_CLIPBOARD))
+        else if (0 == g_strcasecmp(param, SESMAN_CFG_SEC_RESTRICT_INBOUND_CLIPBOARD))
         {
             char unrecognised[256];
             sc->restrict_inbound_clipboard =
@@ -379,16 +377,26 @@ config_read_security(int file, struct config_security *sc,
                     unrecognised);
             }
         }
-        if (0 == g_strcasecmp(buf, SESMAN_CFG_SEC_ALLOW_ALTERNATE_SHELL))
+        else if (0 == g_strcasecmp(param, SESMAN_CFG_SEC_ALLOW_ALTERNATE_SHELL))
         {
-            sc->allow_alternate_shell =
-                g_text2bool((char *)list_get_item(param_v, i));
+            sc->allow_alternate_shell = g_text2bool(val);
         }
-
-        if (0 == g_strcasecmp(buf, SESMAN_CFG_SEC_XORG_NO_NEW_PRIVILEGES))
+        else if (0 == g_strcasecmp(param, SESMAN_CFG_SEC_XORG_NO_NEW_PRIVILEGES))
         {
-            sc->xorg_no_new_privileges =
-                g_text2bool((char *)list_get_item(param_v, i));
+            sc->xorg_no_new_privileges = g_text2bool(val);
+        }
+        else if (0 == g_strcasecmp(param, SESMAN_CFG_SEC_SESSION_SOCKDIR_GROUP))
+        {
+            if (g_getgroup_info(val, &gid) == 0)
+            {
+                sc->session_sockdir_group = gid;
+            }
+            else
+            {
+                LOG(LOG_LEVEL_WARNING,
+                    "Group '%s' is not recognised - using group %d",
+                    val, sc->session_sockdir_group);
+            }
         }
     }
 

sesman/libsesman/sesman_config.h

@@ -109,6 +109,12 @@ struct config_security
      * @brief if the Xorg X11 server should be started with no_new_privs (Linux only)
      */
     int xorg_no_new_privileges;
+
+    /*
+     * @var session_sockdir_group
+     * @brief Group to have read access to the session sockdirs
+     */
+    int session_sockdir_group;
 };
 
 /**