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GnuTLS 2.2.5 - Brown paper bag release

From: Simon Josefsson
Subject: GnuTLS 2.2.5 - Brown paper bag release
Date: Mon, 19 May 2008 22:54:43 +0200
User-agent: Gnus/5.110009 (No Gnus v0.9) Emacs/22.2 (gnu/linux)

We are embarrassed to announce a new stable GnuTLS release: Version 2.2.5.

This release fixes a flaw in the patch for one of the security problems
fixed by version 2.2.4.  The updated advisory is included below.  As
always, further updates will be posted on:

I'd also like to take the opportunity to correct another mistake made
the announcement for v2.2.4: please send security analysis to
address@hidden and not to any other address.

GnuTLS is a modern C library that implement the standard network
security protocol Transport Layer Security (TLS), for use by network
applications.  GnuTLS is developed for GNU/Linux, but works on many
Unix-like systems and comes with a binary installer for Windows.

The core GnuTLS library is distribute under the terms of the GNU Lesser
General Public License version 2.1 (or later).  The "extra" GnuTLS
libraries -- which contains OpenPGP and TLS/IA support, LZO compression,
the OpenSSL compatibility library -- and the self tests and command line
tools are distributed under the GNU General Public License version 3.0
(or later).  The manual is distributed under the GNU Free Documentation
License version 1.2 (or later).

The project page of the library is available at:

What's New

* Version 2.2.5 (released 2008-05-19)

** Fix flaw in fix for GNUTLS-SA-2008-1-3.
The flaw would result in incorrectly terminated sessions with the
error "Decryption has failed" when the server sends a small packet
(typically when the session is closed).  Reported by Andreas Metzler
<address@hidden> in

** API and ABI modifications:
No changes since last version.

Getting the Software

GnuTLS may be downloaded from one of the mirror sites or direct from
<>.  The list of mirrors can be found at

Here are the BZIP2 compressed sources (4.8MB):

Here are OpenPGP detached signatures signed using key 0xB565716F:

Note, that we don't distribute gzip compressed tarballs.

In order to check that the version of GnuTLS which you are going to
install is an original and unmodified one, you should verify the OpenPGP
signature.  You can use the command

     gpg --verify gnutls-2.2.5.tar.bz2.sig

This checks whether the signature file matches the source file.  You
should see a message indicating that the signature is good and made by
that signing key.  Make sure that you have the right key, either by
checking the fingerprint of that key with other sources or by checking
that the key has been signed by a trustworthy other key.  The signing
key can be identified with the following information:

pub   1280R/B565716F 2002-05-05 [expires: 2008-06-30]
      Key fingerprint = 0424 D4EE 81A0 E3D1 19C6  F835 EDA2 1E94 B565 716F
uid                  Simon Josefsson <address@hidden>
uid                  Simon Josefsson <address@hidden>

The key is available from:

Alternatively, after successfully verifying the OpenPGP signature of
this announcement, you could verify that the files match the following
checksum values.  The values are for SHA-1 and SHA-224 respectively:

7620d092c790f0a5ac5486c3563786ca8777083d  gnutls-2.2.5.tar.bz2

d1cee353902a404a4b02fd0da981e8164c8b60356917abfc781b066c  gnutls-2.2.5.tar.bz2


The manual is available online at:

In particular the following formats are available:


For developers there is a GnuTLS API reference manual formatted using
the GTK-DOC tools:


If you need help to use GnuTLS, or want to help others, you are invited
to join our help-gnutls mailing list, see:

If you wish to participate in the development of GnuTLS, you are invited
to join our gnutls-devel mailing list, see:

Windows installer

GnuTLS has been ported to the Windows operating system, and a binary
installer is available.  The installer contains DLLs for application
development, manuals, examples, and source code.  The installer consists
of libgpg-error 1.6, libgcrypt 1.4.1, libtasn1 1.4, and GnuTLS 2.2.5.

For more information about GnuTLS for Windows:

The Windows binary installer and OpenPGP signature: (13MB)

A ZIP file with the installed tree of binaries: (4.6MB)

The checksum values for SHA-1 and SHA-224 are:

02a84f3844b9376f65edfbb6f6cc377a239a6264  gnutls-2.2.5.exe

0a1b1687d7b542e3c41abaa9c321946db32487f936b45ec7bdb0d563  gnutls-2.2.5.exe


GnuTLS messages have been translated into Dutch, German, Malay, Polish
and Swedish.  We welcome the addition of more translations.


Improving GnuTLS is costly, but you can help!  We are looking for
organizations that find GnuTLS useful and wish to contribute back.  You
can contribute by reporting bugs, improve the software, or donate money
or equipment.

Commercial support contracts for GnuTLS are available, and they help
finance continued maintenance.  Simon Josefsson Datakonsult, a Stockholm
based privately held company, is currently funding GnuTLS maintenance.
We are always looking for interesting development projects.  See for more details.

The GnuTLS service directory is available at:

Happy Hacking,

Attachment: pgpEt2fonWGFn.pgp
Description: PGP signature

Hash: SHA1

Three security vulnerabilities in GnuTLS [GNUTLS-SA-2008-1]
- -----------------------------------------------------------

Released 2008-05-19 12:00:00 UTC.  Updated 2008-05-19 20:00.

Vulnerabilities were discovered by Ossi Herrala and Jukka Taimisto
from the CROSS project at Codenomicon Ltd., and reported directly to
the vendor through CERT-FI.  Problems reproduced and patches developed
by Simon Josefsson and Nikos Mavrogiannopoulos.  Flaw in the initial
advisory reported by Andreas Metzler.

All updates with more details about these vulnerabilities will be
added to <>.

libgnutls: Fix crash when sending invalid server name
- -----------------------------------------------------

The crash can be triggered remotely before authentication, which can
lead to a Denial of Service attack to disable the server.  The bug
cause gnutls to store more session resumption data than what was
allocated for, thus overwriting unallocated memory.  The fix is to
patch ext_server_name.c as below.

libgnutls: Fix crash when sending repeated client hellos
- --------------------------------------------------------

The crash can be triggered remotely before authentication, which can
lead to a Denial of Service attack to disable the server.  The bug
triggers a null-pointer dereference.  The fix is to patch
gnutls_handshake.c as below.

libgnutls: Fix crash in cipher padding decoding for invalid record lengths
- --------------------------------------------------------------------------

The crash can be triggered remotely before authentication, which can
lead to a Denial of Service attack to disable the server.  The bug
cause gnutls to read memory beyond the end of the received record.
The fix is to patch gnutls_cipher.c as below.

How to Apply the Patch
- ----------------------

This file has been verified to apply to the latest stable release of
the recent stable branches: version 1.4.5, 1.6.3, 2.0.4, and 2.2.3.
The patch will also work with version 1.2.11 but you will need to
apply it manually.  The patch also apply to the latest development
version 2.3.9 but keep in mind that this version is not intended for
production systems.  (The patch will not work for the broken releases
version 2.2.4 and 2.3.10 since they contained an incorrect patch.)

The patch was created with 'git-diff', so you will need to use '-p 1'
when invoking patch.  The following illustrate how you apply the patch
against version 1.6.3.

address@hidden:~/src$ gpg gnutls-sa-2008-01.txt.asc 
gpg: Signature made Mon 19 May 2008 12:03:18 PM CEST using RSA key ID B565716F
gpg: Good signature from "Simon Josefsson <address@hidden>"
gpg:                 aka "Simon Josefsson <address@hidden>"
address@hidden:~/src$ tar xfj gnutls-1.6.3.tar.bz2
address@hidden:~/src$ cd gnutls-1.6.3/
address@hidden:~/src/gnutls-1.6.3$ patch -p 1 < ../gnutls-sa-2008-01.txt
patching file lib/ext_server_name.c
patching file lib/gnutls_cipher.c
Hunk #1 succeeded at 495 (offset -8 lines).
patching file lib/gnutls_handshake.c
Hunk #1 succeeded at 929 (offset -74 lines).

Then build the package as normal.

diff --git a/lib/ext_server_name.c b/lib/ext_server_name.c
index 72e42ff..a2db949 100644
- --- a/lib/ext_server_name.c
+++ b/lib/ext_server_name.c
@@ -74,10 +74,27 @@ _gnutls_server_name_recv_params (gnutls_session_t session,
          len = _gnutls_read_uint16 (p);
          p += 2;

- -       DECR_LENGTH_RET (data_size, len, 0);
- -       server_names++;
+         if (len > 0)
+           {
+             DECR_LENGTH_RET (data_size, len, 0);
+             server_names++;
+             p += len;
+           }
+         else
+           _gnutls_handshake_log
+             ("HSK[%x]: Received zero size server name (under attack?)\n",
+              session);

- -       p += len;
+       }
+      /* we cannot accept more server names.
+       */
+      if (server_names > MAX_SERVER_NAME_EXTENSIONS)
+       {
+         _gnutls_handshake_log
+           ("HSK[%x]: Too many server names received (under attack?)\n",
+            session);
+         server_names = MAX_SERVER_NAME_EXTENSIONS;

       session->security_parameters.extensions.server_names_size =
@@ -85,10 +102,6 @@ _gnutls_server_name_recv_params (gnutls_session_t session,
       if (server_names == 0)
        return 0;               /* no names found */

- -      /* we cannot accept more server names.
- -       */
- -      if (server_names > MAX_SERVER_NAME_EXTENSIONS)
- -     server_names = MAX_SERVER_NAME_EXTENSIONS;

       p = data + 2;
       for (i = 0; i < server_names; i++)
diff --git a/lib/gnutls_cipher.c b/lib/gnutls_cipher.c
index e930c1d..e16ad1f 100644
- --- a/lib/gnutls_cipher.c
+++ b/lib/gnutls_cipher.c
@@ -504,17 +503,20 @@ _gnutls_ciphertext2compressed (gnutls_session_t session,
       pad =[ciphertext.size - 1] + 1;  /* pad */
- -      length = ciphertext.size - hash_size - pad;
- -
- -      if (pad > ciphertext.size - hash_size)
+      if ((int)pad > (int)ciphertext.size - hash_size)
          gnutls_assert ();
+         _gnutls_record_log
+           ("REC[%x]: Short record length %d > %d - %d (under attack?)\n",
+            session, pad, ciphertext.size, hash_size);
          /* We do not fail here. We check below for the
           * the pad_failed. If zero means success.
          pad_failed = GNUTLS_E_DECRYPTION_FAILED;
+      length = ciphertext.size - hash_size - pad;
       /* Check the pading bytes (TLS 1.x)
       if (ver >= GNUTLS_TLS1 && pad_failed == 0)
diff --git a/lib/gnutls_handshake.c b/lib/gnutls_handshake.c
index 4ab6db6..d798180 100644
- --- a/lib/gnutls_handshake.c
+++ b/lib/gnutls_handshake.c
@@ -1003,6 +1003,14 @@ _gnutls_recv_handshake_header (gnutls_session_t session,

       *recv_type = session->internals.handshake_header_buffer.recv_type;

+      if (*recv_type != type)
+       {
+         gnutls_assert ();
+         _gnutls_handshake_log
+           ("HSK[%x]: Handshake type mismatch (under attack?)\n", session);
+       }
       return session->internals.handshake_header_buffer.packet_length;

Version: GnuPG v1.4.7 (GNU/Linux)


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