GNU bug report logs - #59544
[PATCH] Fixed lib-src/etags.c command execute vulnerability

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Message #5 received at submit <at> debbugs.gnu.org (full text, mbox):

From: "lux" <lx <at> shellcodes.org>
To: "bug-gnu-emacs" <bug-gnu-emacs <at> gnu.org>
Cc: lux <lx <at> shellcodes.org>
Subject: [PATCH] Fixed lib-src/etags.c command execute vulnerability
Date: Thu, 24 Nov 2022 23:27:13 +0800

[Message part 1 (text/plain, inline)]

Hi, In ctags (Emacs <= 28.2.50) has a command execute vulnerability.

When using the -u parameter, ctags will execute external shell commands by calling the system() function, if there are special file names, unexpected shell commands may be executed. The example is as follows:


$ ls
etags.c

$ /usr/local/bin/ctags *.c
$ touch "'| uname -a #.c"
$ /usr/local/bin/ctags -u *.c
Linux mypc 6.0.8-300.fc37.x86_64 #1 SMP PREEMPT_DYNAMIC Fri Nov 11 15:09:04 UTC 2022 x86_64 x86_64 x86_64 GNU/Linux


^C/usr/local/bin/ctags: failed to execute shell command


The vulnerability occurs in the following code:


char *z = stpcpy (cmd, "mv ");&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;
z = stpcpy (z, tagfile);&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;
z = stpcpy (z, " OTAGS;grep -Fv '\t");&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;
z = stpcpy (z, argbuffer[i].what);&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;
z = stpcpy (z, "\t' OTAGS &gt;");&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;
z = stpcpy (z, tagfile);&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;
strcpy (z, ";rm OTAGS");&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;
if (system (cmd) != EXIT_SUCCESS)&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; 
&nbsp; fatal ("failed to execute shell command");&nbsp; &nbsp; &nbsp;



Because the file name is not checked, the file name is used as a concatenated string:


mv tags OTAGS;grep -Fv '	'| uname -a #.c	' OTAGS &gt;tags;rm OTAGS


Email attachments are patches.

[Message part 2 (text/html, inline)]

[0001-lib-src-etags.c-Fix-ctags-command-execute-vulnerabil.patch (application/octet-stream, attachment)]

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