[PATCH 1/3] telnet: Abort subnegotiation of XDISPLOC on error.

[Erik Auerswald]

Subnegotiation of the X Display Location option needs to be
aborted when it cannot be completed.

* NEWS: Mention fix.
* telnet/telnet.c (suboption): Call send_wont() to abort when
DISPLAY value does not fit into temporary buffer.
---
 NEWS            | 4 ++++
 telnet/telnet.c | 6 ++++--
 2 files changed, 8 insertions(+), 2 deletions(-)

diff --git a/NEWS b/NEWS
index 78e9ca9a..166ca457 100644
--- a/NEWS
+++ b/NEWS
@@ -7,6 +7,10 @@ GNU inetutils NEWS -- history of user-visible changes.
 Don't infloop when (malicious) server sends too large terminal value,
 see: https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=945861
 
+Abort subnegotiation of X Display Location Option with WON'T when DISPLAY
+value is too large for buffer.  Reported by Joerg Mayer in
+<https://lists.gnu.org/archive/html/bug-inetutils/2022-01/msg00010.html>.
+
 ** Various bugs fixes, internal improvements and clean ups.
 
 Further cleanup of configure.ac, updates to modern autoconf releases,
diff --git a/telnet/telnet.c b/telnet/telnet.c
index c5b18c14..62c79653 100644
--- a/telnet/telnet.c
+++ b/telnet/telnet.c
@@ -1008,11 +1008,13 @@ suboption (void)
          /* Remote host, and display server must not be corrupted
           * by truncation.  In addition, every character of telnet
           * protocol must remain unsevered.  Check that DP fits in
-          * full within TEMP.  Otherwise report buffer error.
+          * full within TEMP.  Otherwise report buffer error and
+          * turn off the option.
           */
          if (strlen ((char *) dp) >= sizeof (temp) - 4 - 2)
            {
-             printf ("lm_will: not enough room in buffer\n");
+             printf ("lm_will: not enough room in buffer for DISPLAY\n");
+             send_wont (TELOPT_XDISPLOC, 1);
              break;
            }
 
-- 
It's impossible to learn very much by simply sitting in a lecture,
or even by simply doing problems that are assigned.
                        -- Richard P. Feynman