Add DISPLAY(n) ass a valid form of chansrvport

docs/man/xrdp.ini.5.in

@@ -232,7 +232,7 @@ This option can have one of the following values:
 
 \fBINFO\fR or \fB3\fR \- Logs errors, warnings and informational messages
 
-\fBDEBUG\fR or \fB4\fR \- Log everything. If \fBsesman\fR is compiled in debug mode, this options will output many more low\-level message, useful for developers
+\fBDEBUG\fR or \fB4\fR \- Log everything. If \fBxrdp-sesman\fR is compiled in debug mode, this options will output many more low\-level message, useful for developers
 
 .TP
 \fBEnableSyslog\fR=\fI[true|false]\fR
@@ -338,6 +338,16 @@ values supported for a particular release of \fBxrdp\fR(8) are documented in
 Specifies the session type. The default, \fI0\fR, is Xvnc, \fI10\fR is
 X11rdp, and \fI20\fR is Xorg with xorgxrdp modules.
 
+.TP
+\fBchansrvport\fR=\fBDISPLAY(\fR\fIn\fR\fB)\fR|\fI/path/to/domain-socket\fR
+Asks xrdp to connect to a manually started \fBxrdp-chansrv\fR instance.
+This can be useful if you wish to use to use xrdp to connect to a VNC session
+which has been started other than by \fBxrdp-sesman\fR, as you can then make
+use of \fBxrdp\-chansrv\fR facilities in the VNC session.
+
+The first form of this setting is recommended, replacing \fIn\fR with the
+X11 display number of the session.
+
 .SH "EXAMPLES"
 This is an example \fBxrdp.ini\fR:
 
@@ -369,8 +379,9 @@ password={base64}cGFzc3dvcmQhCg==
 
 .SH "SEE ALSO"
 .BR xrdp (8),
-.BR sesman (8),
-.BR sesrun (8),
+.BR xrdp\-chansrv (8),
+.BR xrdp\-sesman (8),
+.BR xrdp\-sesrun (8),
 .BR sesman.ini (5)
 
 For more info on \fBxrdp\fR see

xrdp/xrdp.ini.in

@@ -182,9 +182,6 @@ tcutils=true
 ; for debugging xrdp, in section xrdp1, change port=-1 to this:
 #port=/tmp/.xrdp/xrdp_display_10
 
-; for debugging xrdp, add following line to section xrdp1
-#chansrvport=/tmp/.xrdp/xrdp_chansrv_socket_7210
-
 
 ;
 ; Session types
@@ -214,7 +211,10 @@ port=-1
 ; Disable requested encodings to support buggy VNC servers
 ; (1 = ExtendedDesktopSize)
 #disabled_encodings_mask=0
-
+; Use this to connect to a chansrv instance created outside of sesman
+; (e.g. as part of an x11vnc console session). Replace '0' with the
+; display number of the session
+#chansrvport=DISPLAY(0)
 
 [vnc-any]
 name=vnc-any

xrdp/xrdp_mm.c

@@ -34,6 +34,7 @@
 #include <security/pam_constants.h>
 #endif
 #endif /* USE_PAM */
+#include <ctype.h>
 
 #include "xrdp_encoder.h"
 #include "xrdp_sockets.h"
@@ -2160,6 +2161,54 @@ getPAMAdditionalErrorInfo(const int pamError, struct xrdp_mm *self)
 }
 #endif
 
+/*************************************************************************//**
+ * Parses a chansrvport string
+ *
+ * This will be in one of the following formats:-
+ * <path>         UNIX path to a domain socket
+ * DISPLAY(<num>) Use chansrv on X Display <num>
+ *
+ * @param value assigned to chansrvport
+ * @param dest Output buffer
+ * @param dest_size Total size of output buffer, including terminator space
+ * @return 0 for success
+ */
+
+static int
+parse_chansrvport(const char *value, char *dest, int dest_size)
+{
+    int rv = 0;
+
+    if (g_strncmp(value, "DISPLAY(", 8) == 0)
+    {
+        const char *p = value + 8;
+        const char *end = p;
+
+        /* Check next chars are digits followed by ')' */
+        while (isdigit(*end))
+        {
+            ++end;
+        }
+
+        if (end == p || *end != ')')
+        {
+            LOG(LOG_LEVEL_WARNING, "Ignoring invalid chansrvport string '%s'",
+                value);
+            rv = -1;
+        }
+        else
+        {
+            g_snprintf(dest, dest_size, XRDP_CHANSRV_STR, g_atoi(p));
+        }
+    }
+    else
+    {
+        g_strncpy(dest, value, dest_size - 1);
+    }
+
+    return rv;
+}
+
 /*****************************************************************************/
 int
 xrdp_mm_connect(struct xrdp_mm *self)
@@ -2238,10 +2287,12 @@ xrdp_mm_connect(struct xrdp_mm *self)
         }
         else if (g_strcasecmp(name, "chansrvport") == 0)
         {
-            g_strncpy(chansrvport, value, 255);
+            if (parse_chansrvport(value, chansrvport, sizeof(chansrvport)) == 0)
+            {
                 self->usechansrv = 1;
             }
         }
+    }
 
 #ifdef USE_PAM
     if (use_pam_auth)