GnuPG 1.4 and 2.0 buffer overflow
While fixing a bug reported by Hugh Warrington, a buffer overflow has
been identified in all released GnuPG versions. The current versions
1.4.5 and 2.0.0 are affected. A small patch is provided.
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When running GnuPG interactively, special crafted messages may be used
to crash gpg or gpg2. Running gpg in batch mode, as done by all
software using gpg as a backend (e.g. mailers), is not affected by
Exploiting this overflow seems to be possible.
gpg-agent, gpgsm, gpgv or other tools from the GnuPG suite are not
Apply the following patch to GnuPG. It should apply cleanly to
current versions (1.4.5 as well as 2.0.0) but might also work for
2006-11-27 Werner Koch <wk (at) g10code (dot) com [email concealed]>
* openfile.c (ask_outfile_name): Fixed buffer overflow occurring
if make_printable_string returns a longer string. Fixes bug 728.
--- g10/openfile.c (revision 4348)
+++ g10/openfile.c (working copy)
@@ -144,8 +144,8 @@
s = _("Enter new filename");
- n = strlen(s) + namelen + 10;
defname = name && namelen? make_printable_string( name, namelen, 0): NULL;
+ n = strlen(s) + (defname?strlen (defname):0) + 10;
prompt = xmalloc(n);
if( defname )
sprintf(prompt, "%s [%s]: ", s, defname );
The code in question has been introduced on July 1, 1999 and is a
pretty obvious bug. make_printable_string is supposed to replace
possible dangerous characters from a prompt and returns a malloced
string. Thus this string may be longer than the orginal one; the
buffer for the prompt has only be allocated at the size of the original
string - oops. Note, that using snprintf would not have helped in
this case. How I wish C-90 had introduced asprintf or at least it
would be available on more platforms.
The original bug report is at https://bugs.g10code.com/gnupg/issue728 .
 See http://lists.gnupg.org/mailman/listinfo/gnupg-devel .
Werner Koch <wk (at) gnupg (dot) org [email concealed]>
The GnuPG Experts http://g10code.com
Join the Fellowship and protect your Freedom! http://www.fsfe.org
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