mirror of
git://git.gnupg.org/gnupg.git
synced 2024-12-22 10:19:57 +01:00
95 lines
2.9 KiB
Plaintext
95 lines
2.9 KiB
Plaintext
Realloc Bug with X.509 certificates in GnuPG
|
|
==============================================
|
|
2010-07-23
|
|
|
|
|
|
Summary
|
|
=======
|
|
|
|
While trying to import a server certificate for a CDN service, a segv
|
|
bug was found in GnuPG's GPGSM tool. It is likely that this bug is
|
|
exploitable by sending a special crafted signed message and having a
|
|
user verify the signature.
|
|
|
|
[ Please do not send private mail in response to this message. The
|
|
mailing list gnupg-devel is the best place to discuss this problem
|
|
(please subscribe first so you don't need moderator approval [1]). ]
|
|
|
|
|
|
Impact
|
|
======
|
|
|
|
All applications using GnuPG's GPGSM tool to process S/MIME messages
|
|
or manage X.509 certificates are affected. The bug exists in all
|
|
versions of GnuPG including the recently released GnuPG 2.0.16.
|
|
|
|
GPG (i.e. OpenPGP) is NOT affected.
|
|
|
|
GnuPG 1.x is NOT affected because it does not come with the GPGSM
|
|
tool.
|
|
|
|
An exploit is not yet known but it can't be ruled out for sure that
|
|
the problem has not already been identified by some dark forces.
|
|
|
|
|
|
Description
|
|
===========
|
|
|
|
Importing a certificate with more than 98 Subject Alternate Names [2]
|
|
via GPGSM's import command or implicitly while verifying a signature
|
|
causes GPGSM to reallocate an array with the names. The bug is that
|
|
the reallocation code misses assigning the reallocated array to the
|
|
old array variable and thus the old and freed array will be used.
|
|
Usually this leads to a segv.
|
|
|
|
It might be possible to use one of the techniques to exploit
|
|
assignments to malloced and freed memory. Such an exploit won't be
|
|
easy to write because the attack vector must fit into a valid ASN.1
|
|
DER encoded DN. To further complicate the task, that DN is not used
|
|
directly but after a transformation to RFC-2253 format.
|
|
|
|
|
|
|
|
Solution
|
|
========
|
|
|
|
Apply the following patch. The patch is required for all GnuPG
|
|
versions < 2.0.17. It applies to 2.0.16 but should apply to many
|
|
older versions as well.
|
|
|
|
|
|
--- kbx/keybox-blob.c (revision 5367)
|
|
+++ kbx/keybox-blob.c (working copy)
|
|
@@ -898,6 +898,7 @@
|
|
rc = gpg_error_from_syserror ();
|
|
goto leave;
|
|
}
|
|
+ names = tmp;
|
|
}
|
|
names[blob->nuids++] = p;
|
|
if (!i && (p=x509_email_kludge (p)))
|
|
|
|
|
|
|
|
|
|
Support
|
|
=======
|
|
|
|
g10 Code GmbH [3], a Duesseldorf based company owned and headed by
|
|
GnuPG's principal author, is currently funding GnuPG development.
|
|
Support contracts or other financial backing will greatly help us to
|
|
improve the quality of GnuPG.
|
|
|
|
|
|
Thanks
|
|
======
|
|
|
|
Peter Gutmann for his "A mighty fortress is our PKI" mail to the
|
|
cryptography ML which contained a pointer to a certificate to exhibit
|
|
the problem. This bug was created, found and fixed by Werner Koch.
|
|
|
|
|
|
[1] See http://lists.gnupg.org/mailman/listinfo/gnupg-devel
|
|
[2] <http://cvs.gnupg.org/cgi-bin/viewcvs.cgi/*checkout*/trunk/tests/samplekeys/cert-with-117-akas.pem>
|
|
[3] See http://www.gnupg.org/service.html
|