Werner Koch
2018-Jun-08 13:40 UTC
[Announce] [security fix] GnuPG 2.2.8 released (CVE-2018-12020)
Hello!
We are pleased to announce the availability of a new GnuPG release:
version 2.2.8. This version fixes a critical security bug and comes
with some other minor changes.
Impact
=====
All current GnuPG versions are affected on all platforms.
All mail clients and other applications which make use of GPG but are
not utilizing the GPGME library might be affected.
The OpenPGP protocol allows to include the file name of the original
input file into a signed or encrypted message. During decryption and
verification the GPG tool can display a notice with that file name. The
displayed file name is not sanitized and as such may include line feeds
or other control characters. This can be used inject terminal control
sequences into the out and, worse, to fake the so-called status
messages. These status messages are parsed by programs to get
information from gpg about the validity of a signature and an other
parameters. Status messages are created with the option "--status-fd
N"
where N is a file descriptor. Now if N is 2 the status messages and the
regular diagnostic messages share the stderr output channel. By using a
made up file name in the message it is possible to fake status messages.
Using this technique it is for example possible to fake the verification
status of a signed mail.
Although GnuPG takes great care to sanitize all diagnostic and status
output, the case at hand was missed but finally found and reported by
Marcus Brinkmann. CVE-2018-12020 was assigned to this bug; GnuPG tracks
it at <https://dev/gnupg.org/T4012>.
Solution
=======
If your application uses GPGME your application is safe. Fortunately
most modern mail readers use GPGME, including GpgOL and KMail. Mutt
users should make sure to use "set crypt_use_gpgme".
If you are parsing GnuPG status output and you use a dedicated file
descriptor with --status-fd you are safe. A dedicated file descriptor
is one that is not shared with the log output. The log output defaults
to stderr (2) but may be a different if the option --logger-fd is used.
If you are not using --verbose you are safe. But take care: --verbose
might be specified in the config file. As a short term mitigation or if
you can't immediately upgrade to the latest versions, you can add
--no-verbose to the invocation of gpg.
Another short term mitigation is to redirect the log output to a
different file: For example "--log-file /dev/null".
The suggested solution is to update to GnuPG 2.2.8 or a vendor provided
update of their GnuPG version.
To check whether the bug has been fixed you may use the simple test at
the end of this mail [1].
About GnuPG
==========
The GNU Privacy Guard (GnuPG) is a complete and free implementation
of the OpenPGP standard which is commonly abbreviated as PGP.
GnuPG allows to encrypt and sign data and communication, features a
versatile key management system as well as access modules for public key
directories. GnuPG itself is a command line tool with features for easy
integration with other applications. A wealth of frontend applications
and libraries making use of GnuPG are available. As an Universal Crypto
Engine GnuPG provides support for S/MIME and Secure Shell in addition to
OpenPGP.
GnuPG is Free Software (meaning that it respects your freedom). It can
be freely used, modified and distributed under the terms of the GNU
General Public License.
Noteworthy changes in version 2.2.8
==================================
* gpg: Decryption of messages not using the MDC mode will now lead
to a hard failure even if a legacy cipher algorithm was used. The
option --ignore-mdc-error can be used to turn this failure into a
warning. Take care: Never use that option unconditionally or
without a prior warning.
* gpg: The MDC encryption mode is now always used regardless of the
cipher algorithm or any preferences. For testing --rfc2440 can be
used to create a message without an MDC.
* gpg: Sanitize the diagnostic output of the original file name in
verbose mode. [#4012,CVE-2018-12020]
* gpg: Detect suspicious multiple plaintext packets in a more
reliable way. [#4000]
* gpg: Fix the duplicate key signature detection code. [#3994]
* gpg: The options --no-mdc-warn, --force-mdc, --no-force-mdc,
--disable-mdc and --no-disable-mdc have no more effect.
* agent: Add DBUS_SESSION_BUS_ADDRESS and a few other envvars to the
list of startup environment variables. [#3947]
Getting the Software
===================
Please follow the instructions found at <https://gnupg.org/download/> or
read on:
GnuPG 2.2.8 may be downloaded from one of the GnuPG mirror sites or
direct from its primary FTP server. The list of mirrors can be found at
<https://gnupg.org/download/mirrors.html>. Note that GnuPG is not
available at ftp.gnu.org.
The GnuPG source code compressed using BZIP2 and its OpenPGP signature
are available here:
https://gnupg.org/ftp/gcrypt/gnupg/gnupg-2.2.8.tar.bz2 (6477k)
https://gnupg.org/ftp/gcrypt/gnupg/gnupg-2.2.8.tar.bz2.sig
An installer for Windows without any graphical frontend except for a
very minimal Pinentry tool is available here:
https://gnupg.org/ftp/gcrypt/binary/gnupg-w32-2.2.8_20180608.exe (3916k)
https://gnupg.org/ftp/gcrypt/binary/gnupg-w32-2.2.8_20180608.exe.sig
The source used to build the Windows installer can be found in the same
directory with a ".tar.xz" suffix. A new Gpg4win installer featuring
this version of GnuPG will be available soon.
Checking the Integrity
=====================
In order to check that the version of GnuPG which you are going to
install is an original and unmodified one, you can do it in one of
the following ways:
* If you already have a version of GnuPG installed, you can simply
verify the supplied signature. For example to verify the signature
of the file gnupg-2.2.8.tar.bz2 you would use this command:
gpg --verify gnupg-2.2.8.tar.bz2.sig gnupg-2.2.8.tar.bz2
This checks whether the signature file matches the source file.
You should see a message indicating that the signature is good and
made by one or more of the release signing keys. Make sure that
this is a valid key, either by matching the shown fingerprint
against a trustworthy list of valid release signing keys or by
checking that the key has been signed by trustworthy other keys.
See the end of this mail for information on the signing keys.
* If you are not able to use an existing version of GnuPG, you have
to verify the SHA-1 checksum. On Unix systems the command to do
this is either "sha1sum" or "shasum". Assuming you
downloaded the
file gnupg-2.2.8.tar.bz2, you run the command like this:
sha1sum gnupg-2.2.8.tar.bz2
and check that the output matches the next line:
d87553a125832ea90e8aeb3ceeecf24f88de56fb gnupg-2.2.8.tar.bz2
3126ec2b7005063cbff95792208796dfa42c2a22 gnupg-w32-2.2.8_20180608.tar.xz
231b29631647328934a35f8c6baa483e7594e26a gnupg-w32-2.2.8_20180608.exe
Internationalization
===================
This version of GnuPG has support for 26 languages with Chinese, Czech,
French, German, Japanese, Norwegian, Russian, and Ukrainian being almost
completely translated.
Documentation and Support
========================
If you used GnuPG in the past you should read the description of
changes and new features at doc/whats-new-in-2.1.txt or online at
https://gnupg.org/faq/whats-new-in-2.1.html
The file gnupg.info has the complete reference manual of the system.
Separate man pages are included as well but they miss some of the
details availabale only in thee manual. The manual is also available
online at
https://gnupg.org/documentation/manuals/gnupg/
or can be downloaded as PDF at
https://gnupg.org/documentation/manuals/gnupg.pdf .
The chapters on gpg-agent, gpg and gpgsm include information on how to
set up the whole thing. You may also want to search the GnuPG mailing
list archives or ask on the gnupg-users mailing list for advise on how
to solve problems. Most of the new features are around for several
years and thus enough public experience is available.
Please consult the archive of the gnupg-users mailing list before
reporting a bug: <https://gnupg.org/documentation/mailing-lists.html>.
We suggest to send bug reports for a new release to this list in favor
of filing a bug at <https://bugs.gnupg.org>. If you need commercial
support check out <https://gnupg.org/service.html>.
If you are a developer and you need a certain feature for your project,
please do not hesitate to bring it to the gnupg-devel mailing list for
discussion.
Thanks
=====
Maintenance and development of GnuPG is mostly financed by donations.
The GnuPG project currently employs one full-time developer and one
contractor. Both work exclusively on GnuPG and closely related software
like Libgcrypt, GPGME, and GPA. We are planning to extend our team
again and to help developers to improve integration of crypto in their
applications.
We have to thank all the people who helped the GnuPG project, be it
testing, coding, translating, suggesting, auditing, administering the
servers, spreading the word, and answering questions on the mailing
lists.
Many thanks to our numerous financial supporters, both corporate and
individuals. Without you it would not be possible to keep GnuPG in a
good shape and address all the small and larger requests made by our
users. Thanks.
Happy hacking,
Your GnuPG hackers
p.s.
This is an announcement only mailing list. Please send replies only to
the gnupg-users'at'gnupg.org mailing list.
p.p.s
List of Release Signing Keys:
To guarantee that a downloaded GnuPG version has not been tampered by
malicious entities we provide signature files for all tarballs and
binary versions. The keys are also signed by the long term keys of
their respective owners. Current releases are signed by one or more
of these four keys:
rsa2048 2011-01-12 [expires: 2019-12-31]
Key fingerprint = D869 2123 C406 5DEA 5E0F 3AB5 249B 39D2 4F25 E3B6
Werner Koch (dist sig)
rsa2048 2014-10-29 [expires: 2019-12-31]
Key fingerprint = 46CC 7308 65BB 5C78 EBAB ADCF 0437 6F3E E085 6959
David Shaw (GnuPG Release Signing Key) <dshaw 'at'
jabberwocky.com>
rsa2048 2014-10-29 [expires: 2020-10-30]
Key fingerprint = 031E C253 6E58 0D8E A286 A9F2 2071 B08A 33BD 3F06
NIIBE Yutaka (GnuPG Release Key) <gniibe 'at' fsij.org>
rsa3072 2017-03-17 [expires: 2027-03-15]
Key fingerprint = 5B80 C575 4298 F0CB 55D8 ED6A BCEF 7E29 4B09 2E28
Andre Heinecke (Release Signing Key)
The keys are available at <https://gnupg.org/signature_key.html> and
in any recently released GnuPG tarball in the file g10/distsigkey.gpg .
Note that this mail has been signed by a different key.
==========
[1] If you want to test whether you are affected by this bug, remove the
indentation from the following block
-----BEGIN PGP MESSAGE-----
jA0EBwMC1pW2pqoYvbXl0p4Bo5z/v7PXy7T1BY/KQxWaE9uTBRbf4no64/+5YYzX
+BVNqP+82aBFYXEsD9x1vGuYwofQ4m/q/WcQDEPXhRyzU+4yiT3EOuG7sTTaQR3b
8xAn2Qtpyq5tO7k9CN6dasaXKSduXVmFUqzgU+W9WaTLOKNDFw6FYV3lnOoPtFcX
rzhh2opkX9Oh/5DUkZ6YmUIX3j/A0z+59/qNO1i2hQ= =zswl
-----END PGP MESSAGE-----
and pass to this pipeline
gpg --no-options -vd 2>&1 | grep '^\[GNUPG:] INJECTED'
If you get some output you are using a non-fixed version.
--
# Please read: Daniel Ellsberg - The Doomsday Machine #
Die Gedanken sind frei. Ausnahmen regelt ein Bundesgesetz.
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