From 06580ec448ca9ed543699d85afc4e4b97ec75b65 Mon Sep 17 00:00:00 2001
From: matt335672 <30179339+matt335672@users.noreply.github.com>
Date: Mon, 6 Feb 2023 16:14:36 +0000
Subject: [PATCH] sesman config: Add MaxDisplayNumber

When allocating a display number, we should be aware that
IANA only allow TCP displays up to :63. This PR adds that restriction in
to sesman.ini as a default, to prevent us allocating unavailable TCP
ports.

By default TCP ports are not enabled for X servers, but users can easily
change this if they wish to access X displays directly over the network.

This restriction is in addition to the MaxSessions limit already present
in sesman.ini
---
 docs/man/sesman.ini.5.in         |  7 +++++++
 sesman/libsesman/sesman_config.c | 12 ++++++++++++
 sesman/libsesman/sesman_config.h |  5 +++++
 sesman/sesman.ini.in             |  9 +++++++++
 4 files changed, 33 insertions(+)

diff --git a/docs/man/sesman.ini.5.in b/docs/man/sesman.ini.5.in
index 45c256f9..474591c0 100644
--- a/docs/man/sesman.ini.5.in
+++ b/docs/man/sesman.ini.5.in
@@ -155,6 +155,13 @@ defaults to \fI10\fR.
 Sets the maximum number of simultaneous sessions. If not set or set to
 \fI0\fR, unlimited session are allowed.
 
+.TP
+\fBMaxDisplayNumber\fR=\fInumber\fR
+Sets the maximum number which can be assigned to an X11 $DISPLAY. The
+default is compatible with IANA TCP port allocations. If you are not
+allowing TCP connections to your X servers you may safely increase this
+number.
+
 .TP
 \fBKillDisconnected\fR=\fI[true|false]\fR
 If set to \fB1\fR, \fBtrue\fR or \fByes\fR, every session will be killed
diff --git a/sesman/libsesman/sesman_config.c b/sesman/libsesman/sesman_config.c
index 2c545a1e..0568a25f 100644
--- a/sesman/libsesman/sesman_config.c
+++ b/sesman/libsesman/sesman_config.c
@@ -77,6 +77,7 @@
 #define SESMAN_CFG_SESS_IDLE_LIMIT   "IdleTimeLimit"
 #define SESMAN_CFG_SESS_DISC_LIMIT   "DisconnectedTimeLimit"
 #define SESMAN_CFG_SESS_X11DISPLAYOFFSET "X11DisplayOffset"
+#define SESMAN_CFG_SESS_MAX_DISPLAY  "MaxDisplayNumber"
 
 #define SESMAN_CFG_SESS_POLICY_S "Policy"
 #define SESMAN_CFG_SESS_POLICY_DFLT_S "Default"
@@ -410,6 +411,8 @@ config_read_sessions(int file, struct config_sessions *se, struct list *param_n,
 
     /* setting defaults */
     se->x11_display_offset = 10;
+    // https://www.iana.org/assignments/service-names-port-numbers/service-names-port-numbers.xhtml`
+    se->max_display_number = 63;
     se->max_sessions = 0;
     se->max_idle_time = 0;
     se->max_disc_time = 0;
@@ -428,6 +431,15 @@ config_read_sessions(int file, struct config_sessions *se, struct list *param_n,
             se->x11_display_offset = g_atoi(value);
         }
 
+        else if (0 == g_strcasecmp(buf, SESMAN_CFG_SESS_MAX_DISPLAY))
+        {
+            int mdn = g_atoi(value);
+            if (mdn > 0)
+            {
+                se->max_display_number = mdn;
+            }
+        }
+
         else if (0 == g_strcasecmp(buf, SESMAN_CFG_SESS_MAX))
         {
             se->max_sessions = g_atoi(value);
diff --git a/sesman/libsesman/sesman_config.h b/sesman/libsesman/sesman_config.h
index ea6cf2be..545728a2 100644
--- a/sesman/libsesman/sesman_config.h
+++ b/sesman/libsesman/sesman_config.h
@@ -118,6 +118,11 @@ struct config_sessions
      * @brief X11 TCP port offset. default value: 10
      */
     int x11_display_offset;
+    /**
+     * @var max_display_number
+     * @brief Highest X11 display number considered for allocation
+     */
+    unsigned int max_display_number;
     /**
      * @var max_sessions
      * @brief maximum number of allowed sessions. 0 for unlimited
diff --git a/sesman/sesman.ini.in b/sesman/sesman.ini.in
index f2ce82c1..dd615858 100644
--- a/sesman/sesman.ini.in
+++ b/sesman/sesman.ini.in
@@ -51,6 +51,15 @@ X11DisplayOffset=10
 ; Default: 0
 MaxSessions=50
 
+;; MaxDisplayNumer - maximum number considered for an X display
+; Type: integer
+; Default: 63
+;
+; IANA only allocates TCP ports up to 6063 for X servers. If you are not
+; allowing TCP connections to your X servers you may safely increase this
+; number.
+#MaxDisplayNumber=63
+
 ;; KillDisconnected - kill disconnected sessions
 ; Type: boolean
 ; Default: false