STG Security Advisory: [SSA-20041122-09] cscope insecure temp file creation

vulnerability

Revision 1.2

Date Published: 2004-11-22 (KST)

Last Update: 2004-11-22

Disclosed by SSR Team (advisory (at) stgsecurity (dot) com [email concealed])

Summary

========

cscope is an interactive, screen-oriented tool that allows users to

browse through C source files for specified elements of code.

It is vulnerable to symlink attacks, potentially allowing a local user to

overwrite arbitrary files with the right of the user running them, which

could be root.

Vulnerability Class

===================

Design error: insecure temp file handling

Details

=======

cscope was not designed to handle temp file securely.

main.c 332 line

/* create the temporary file names */

pid = getpid();

(void) sprintf(temp1, "%s/cscope%d.1", tmpdir, pid);

(void) sprintf(temp2, "%s/cscope%d.2", tmpdir, pid);

temporary files created with predictable names.

/tmp/cscope[pid].1

/tmp/cscope[pid].2

If temp1, temp2 are assigned once, they aren't changed until cscope is

terminated. Because cscope uses temp1, temp2 values repeatedly whenever user

searches specified element of code, it's trivial to guess the names of temp

files.

Impact

======

Medium: System file corruption.

Workaround

==========

Do *NOT* run cscope as the right of root.

rexolab's patch isn't the correct patch to this problem.

cscope is made with C language, not PHP language, fopen() doesn't support

mode 'x' in C library.

Affected Products

================

cscope 15.5 and prior

Vendor Status: NOT FIXED

=======================

2003-04-03 Vulnerability found by Jeremy Bae(aka opt, *^^*)

(http://xsdeny.net/kweblog/stories.php?story=03/04/03/9181080)

2004-11-08 cscope developer notified.

2004-11-17 rexolab released the advisory irresponsibly and incorrectly.

2004-11-22 Official release.

Credits

======

Jeremy Bae at STG Security

[ reply ]