We are pleased to announce a new stable GnuTLS release: Version 2.2.4. This release fixes three serious bugs that can crash the GnuTLS library. We invite more detailed analysis of the problem, following our general security advisory approach explained on:
http://www.gnu.org/software/gnutls/security.html Particularly, it would be useful to answer the question of whether these bugs can be exploited remotely to execute arbitrary code. It is certainly possible to cause the server to crash. We don't have resources to investigate this problem more ourselves currently. Please send your analysis to [EMAIL PROTECTED] and I'll update the security advisory web page pointing to it. Be sure to check the web page first to get updates on what has been done so far. Below is attached our own security advisory and patch. The 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. 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: http://www.gnutls.org/ http://www.gnu.org/software/gnutls/ http://josefsson.org/gnutls/ What's New ========== * Version 2.2.4 (released 2008-05-19) ** Fix three security vulnerabilities. [GNUTLS-SA-2008-1] Thanks to CERT-FI for finding the bugs and providing detailed reports, which allowed the bugs to be reproduced and fixed easily. Patches developed by Simon Josefsson and Nikos Mavrogiannopoulos. Any updates with more details about these vulnerabilities will be added to <http://www.gnu.org/software/gnutls/security.html> *** [GNUTLS-SA-2008-1-1] *** libgnutls: Fix crash when sending invalid server name. The crash can be triggered remotely before authentication, which can lead to a Daniel 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. *** [GNUTLS-SA-2008-1-2] *** libgnutls: Fix crash when sending repeated client hellos. The crash can be triggered remotely before authentication, which can lead to a Daniel of Service attack to disable the server. The bug triggers a null-pointer dereference. *** [GNUTLS-SA-2008-1-3] *** libgnutls: Fix crash in cipher padding decoding for invalid record lengths. The crash can be triggered remotely before authentication, which can lead to a Daniel of Service attack to disable the server. The bug cause gnutls to read memory beyond the end of the received record. ** 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 <ftp://ftp.gnutls.org/pub/gnutls/>. The list of mirrors can be found at <http://www.gnu.org/software/gnutls/download.html>. Note, that GnuTLS is not available at ftp.gnu.org. Here are the BZIP2 compressed sources (4.8MB): ftp://ftp.gnu.org/pub/gnutls/gnutls-2.2.4.tar.bz2 http://josefsson.org/gnutls/releases/gnutls-2.2.4.tar.bz2 Here are OpenPGP detached signatures signed using key 0xB565716F: ftp://ftp.gnu.org/pub/gnutls/gnutls-2.2.4.tar.bz2.sig http://josefsson.org/gnutls/releases/gnutls-2.2.4.tar.bz2.sig 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-2.2.4.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 <[EMAIL PROTECTED]> uid Simon Josefsson <[EMAIL PROTECTED]> The key is available from: http://josefsson.org/key.txt dns:b565716f.josefsson.org?TYPE=CERT 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: 3b5d8138e3ce78b3a25f8d0491da438bb8ef6a4e gnutls-2.2.4.tar.bz2 85b29eab286bb55d48d1454bfcf5bebba63581159c9dd0850a32a4c3 gnutls-2.2.4.tar.bz2 Documentation ============= The manual is available online at: http://www.gnu.org/software/gnutls/documentation.html In particular the following formats are available: HTML: http://www.gnu.org/software/gnutls/manual/html_node/index.html PDF: http://www.gnu.org/software/gnutls/manual/gnutls.pdf For developers there is a GnuTLS API reference manual formatted using the GTK-DOC tools: http://www.gnu.org/software/gnutls/reference/gnutls-gnutls.html Community ========= If you need help to use GnuTLS, or want to help others, you are invited to join our help-gnutls mailing list, see: <http://lists.gnu.org/mailman/listinfo/help-gnutls>. If you wish to participate in the development of GnuTLS, you are invited to join our gnutls-devel mailing list, see: <http://lists.gnu.org/mailman/listinfo/gnutls-devel>. 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 2.2.4. For more information about GnuTLS for Windows: http://josefsson.org/gnutls4win/ The Windows binary installer and OpenPGP signature: http://josefsson.org/gnutls4win/gnutls-2.2.4.exe (13MB) http://josefsson.org/gnutls4win/gnutls-2.2.4.exe.sig A ZIP file with the installed tree of binaries: http://josefsson.org/gnutls4win/gnutls-2.2.4.zip (4.6MB) http://josefsson.org/gnutls4win/gnutls-2.2.4.zip.sig The checksum values for SHA-1 and SHA-224 are: 331a70b9cb64954d3187c880c1bb6994b4511775 gnutls-2.2.4.exe 9d1a58db1683673f92d1ed1611b4dfd416b0d447a1d393993cf4b494 gnutls-2.2.4.exe df7478d51ce338844496b2bb1a888c4931e3e88f gnutls-2.2.4.zip c7c4bf3ea70ab24c070ee50a4497d403a44dada2b52b80d6bb413b49 gnutls-2.2.4.zip Internationalization ==================== GnuTLS messages have been translated into Dutch, German, Malay, Polish and Swedish. We welcome the addition of more translations. Support ======= 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 http://josefsson.org/ for more details. The GnuTLS service directory is available at: http://www.gnu.org/software/gnutls/commercial.html Happy Hacking, Simon
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-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 Three security vulnerabilities in GnuTLS [GNUTLS-SA-2008-1] - ----------------------------------------------------------- Released 2008-05-19 12:00:00 UTC. 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. All updates with more details about these vulnerabilities will be added to <http://www.gnu.org/software/gnutls/security.html>. libgnutls: Fix crash when sending invalid server name - ----------------------------------------------------- [GNUTLS-SA-2008-1-1] The crash can be triggered remotely before authentication, which can lead to a Daniel 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 - -------------------------------------------------------- [GNUTLS-SA-2008-1-2] The crash can be triggered remotely before authentication, which can lead to a Daniel 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 - -------------------------------------------------------------------------- [GNUTLS-SA-2008-1-3] The crash can be triggered remotely before authentication, which can lead to a Daniel 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 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. [EMAIL PROTECTED]:~/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 <[EMAIL PROTECTED]>" gpg: aka "Simon Josefsson <[EMAIL PROTECTED]>" [EMAIL PROTECTED]:~/src$ tar xfj gnutls-1.6.3.tar.bz2 [EMAIL PROTECTED]:~/src$ cd gnutls-1.6.3/ [EMAIL PROTECTED]:~/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 445 (offset -14 lines). Hunk #2 succeeded at 504 (offset -14 lines). Hunk #3 succeeded at 513 (offset -14 lines). patching file lib/gnutls_handshake.c Hunk #1 succeeded at 929 (offset -74 lines). [EMAIL PROTECTED]:~/src/gnutls-1.6.3$ 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 ad192f4..942fe9f 100644 - --- a/lib/gnutls_cipher.c +++ b/lib/gnutls_cipher.c @@ -459,6 +459,14 @@ _gnutls_ciphertext2compressed (gnutls_session_t session, return GNUTLS_E_INTERNAL_ERROR; } + if (ciphertext.size < (unsigned) blocksize + hash_size) + { + _gnutls_record_log + ("REC[%x]: Short record length %d < %d + %d (under attack?)\n", + session, ciphertext.size, blocksize, hash_size); + gnutls_assert (); + return GNUTLS_E_DECRYPTION_FAILED; + } /* actual decryption (inplace) */ @@ -510,9 +518,7 @@ _gnutls_ciphertext2compressed (gnutls_session_t session, pad = ciphertext.data[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 (); /* We do not fail here. We check below for the @@ -521,6 +527,8 @@ _gnutls_ciphertext2compressed (gnutls_session_t session, 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 GNUTLS_E_UNEXPECTED_HANDSHAKE_PACKET; + } + return session->internals.handshake_header_buffer.packet_length; } -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.7 (GNU/Linux) iOoEAQECADQFAkgxasctFIAAAAAAFQAPcGthLWFkZHJlc3NAZ251cGcub3JnamFz QGV4dHVuZG8uY29tAAoJEO2iHpS1ZXFv3vYFAIc6Ptw8tpSpqKFbCZPX+EwIcRJ1 njhhKXJb7TRU04a4102t+DlP2Tua3yCrd7wFx6yVc0sleXmE8DqtuWNrA1rCXH4u INMYmfYEBxSBVYIzr1G6VxcU2c36q9kaIct831kjTTNgOQTH9xuD0kf5Rwe4abB3 io9Q1tmK7SHl4ix4Mqg37+tzy6ZCqHMKrP1ls7FyYxpdBNvbZT6THi9zZNI= =R87n -----END PGP SIGNATURE-----
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