Package: inetutils-telnetd
Version: 2:1.9-2
Severity: normal
Tags: patch
Telnetd in inetutils-telnetd package lacks handling of some of
TIOCPKT control bytes. The most influential thing is a lack of
handling of TIOCPKT_DATA. TIOCPKT_DATAs i.e. '\0's frequently
appear in the stream of network side. TIOCPKT_FLUSHREAD,
TIOCPKT_STOP and TIOPKT_START leak out into network side too.
In most cases, '\0' is invisible on a terminal, therefore it is
hardly noticed. However, sometimes multibyte characters are
displayed incorrectly by interference of inserted '\0'.
To reproduce this problem:
1) Install intetutils-telnetd package.
2) Make a typescript file by:
script -qc 'telnet localhost'
3) Do something to produce some text outputs.
4) Logout from the telnet session.
5) Look into the typescript file, then you will find
many extra '\0's (^@) in it.
To fix this problem, I have made following patch.
In this patch, the first byte from read() is always treated as
a TIOCPKT control byte. Therefore, it is simply read out instead
of being peeked. This is based on description in man tty_ioctl,
which says the first byte returned by read() is always a TIOCPKT
control byte.
*** telnetd.c.orig 2012-01-01 00:02:32.000000000 +0900
--- telnetd.c 2015-02-15 14:42:29.353912672 +0900
***************
*** 601,611 ****
/* Something to read from the pty... */
if (pty_read () < 0)
break;
! c = pty_get_char (1);
#if defined TIOCPKT_IOCTL
if (c & TIOCPKT_IOCTL)
{
- pty_get_char (0);
copy_termbuf ();
localstat ();
}
--- 601,610 ----
/* Something to read from the pty... */
if (pty_read () < 0)
break;
! c = pty_get_char (0); /* read TIOCPKT control byte */
#if defined TIOCPKT_IOCTL
if (c & TIOCPKT_IOCTL)
{
copy_termbuf ();
localstat ();
}
***************
*** 613,619 ****
if (c & TIOCPKT_FLUSHWRITE)
{
static char flushdata[] = { IAC, DM };
- pty_get_char (0);
netclear (); /* clear buffer back */
net_output_datalen (flushdata, sizeof (flushdata));
set_neturg ();
--- 612,617 ----
***************
*** 630,636 ****
IAC, SB, TELOPT_LFLOW,
flowmode ? LFLOW_ON : LFLOW_OFF, IAC, SE);
}
- pty_get_char (0);
}
}
--- 628,633 ----
-- System Information:
Debian Release: 7.8
APT prefers stable-updates
APT policy: (500, 'stable-updates'), (500, 'stable')
Architecture: i386 (i686)
Kernel: Linux 3.2.0-4-486
Locale: LANG=en_US.UTF-8, LC_CTYPE=en_US.UTF-8 (charmap=UTF-8)
Shell: /bin/sh linked to /bin/dash
Versions of packages inetutils-telnetd depends on:
ii libc6 2.13-38+deb7u7
ii libshishi0 1.0.1-2
ii libtinfo5 5.9-10
ii netbase 5.0
ii openbsd-inetd [inet-superserver] 0.20091229-2
ii rsyslog [system-log-daemon] 5.8.11-3+deb7u2
inetutils-telnetd recommends no packages.
inetutils-telnetd suggests no packages.
-- no debconf information
--
Takashi Yano <takashi.y...@nifty.ne.jp>
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