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(FreeBSD Issues Fix) OpenSSL RSA Signatures Can Be Forged
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SecurityTracker Alert ID: 1016801 |
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SecurityTracker URL: http://securitytracker.com/id/1016801
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CVE Reference:
CVE-2006-4339
(Links to External Site)
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Date: Sep 7 2006
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Impact:
Modification of user information
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Fix Available: Yes Vendor Confirmed: Yes
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Version(s): 0.9.7j and prior versions, 0.9.8 - 0.9.8b
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Description:
A vulnerability was reported in OpenSSL. A remote user may be able to forge certain digital signatures.
If an RSA key with exponent 3 is used, a remote user may be able to forge a PKCS #1 v1.5 signature for that key.
Software that uses PKCS #1 v1.5 may be affected. Software that uses OpenSSL to verify X.509 certificates may also be affected.
Daniel Bleichenbacher reported the type of attack that is possible against PKCS #1 v1.5 signatures.
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Impact:
A remote user may be able to forge signatures (and certificates).
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Solution:
FreeBSD has released a fix and has provided the following solution information [quoted]:
Perform one of the following:
1) Upgrade your vulnerable system to 4-STABLE, 5-STABLE, or 6-STABLE,
or to the RELENG_6_1, RELENG_6_0, RELENG_5_5, RELENG_5_4, RELENG_5_3,
or RELENG_4_11 security branch dated after the correction date.
2) To patch your present system:
The following patches have been verified to apply to FreeBSD 4.11, 5.3,
5.4, 5.5, 6.0, and 6.1 systems.
a) Download the relevant patch from the location below, and verify the
detached PGP signature using your PGP utility.
# fetch http://security.FreeBSD.org/patches/SA-06:19/openssl.patch
# fetch http://security.FreeBSD.org/patches/SA-06:19/openssl.patch.asc
b) Execute the following commands as root:
# cd /usr/src
# patch < /path/to/patch
c) Recompile the operating system as described in
<URL: http://www.freebsd.org/handbook/makeworld.html> and reboot the
system.
NOTE: Any third-party applications, including those installed from the
FreeBSD ports collection, which are statically linked to libcrypto(3)
should be recompiled in order to use the corrected code.
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Vendor URL: www.openssl.org/news/secadv_20060905.txt (Links to External Site)
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Cause:
Authentication error
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Underlying OS:
UNIX (FreeBSD)
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Message History:
This archive entry is a follow-up to the message listed below.
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Source Message Contents
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Date: Wed, 06 Sep 2006 21:59:34 +0000 (GMT)
Subject: FreeBSD Security Advisory FreeBSD-SA-06:19.openssl
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-----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA1
=============================================================================
FreeBSD-SA-06:19.openssl Security Advisory
The FreeBSD Project
Topic: Incorrect PKCS#1 v1.5 padding validation in crypto(3)
Category: contrib
Module: openssl
Announced: 2006-09-06
Affects: All FreeBSD releases.
Corrected: 2006-09-06 21:18:26 UTC (RELENG_6, 6.1-STABLE)
2006-09-06 21:19:21 UTC (RELENG_6_1, 6.1-RELEASE-p6)
2006-09-06 21:20:08 UTC (RELENG_6_0, 6.0-RELEASE-p11)
2006-09-06 21:20:54 UTC (RELENG_5, 5.5-STABLE)
2006-09-06 21:21:50 UTC (RELENG_5_5, 5.5-RELEASE-p4)
2006-09-06 21:22:39 UTC (RELENG_5_4, 5.4-RELEASE-p18)
2006-09-06 21:23:16 UTC (RELENG_5_3, 5.3-RELEASE-p33)
2006-09-06 21:24:04 UTC (RELENG_4, 4.11-STABLE)
2006-09-06 21:24:54 UTC (RELENG_4_11, 4.11-RELEASE-p21)
CVE Name: CVE-2006-4339
For general information regarding FreeBSD Security Advisories,
including descriptions of the fields above, security branches, and the
following sections, please visit
<URL:http://security.freebsd.org/>.
I. Background
FreeBSD includes software from the OpenSSL Project. The OpenSSL Project is
a collaborative effort to develop a robust, commercial-grade, full-featured,
and Open Source toolkit implementing the Secure Sockets Layer (SSL v2/v3)
and Transport Layer Security (TLS v1) protocols as well as a full-strength
general purpose cryptography library.
PKCS#1 v1.5 is a standard for "padding" data before performing a
cryptographic operation using the RSA algorithm. PKCS#1 v1.5 signatures
are for example used in X.509 certificates.
RSA public keys may use a variety of public exponents, of which 3, 17, and
65537 are most common. As a result of a number of known attacks, most keys
generated recently use a public exponent of at least 65537.
II. Problem Description
When verifying a PKCS#1 v1.5 signature, OpenSSL ignores any bytes which
follow the cryptographic hash being signed. In a valid signature there
will be no such bytes.
III. Impact
OpenSSL will incorrectly report some invalid signatures as valid. When
an RSA public exponent of 3 is used, or more generally when a small public
exponent is used with a relatively large modulus (e.g., a public exponent
of 17 with a 4096-bit modulus), an attacker can construct a signature which
OpenSSL will accept as a valid PKCS#1 v1.5 signature.
IV. Workaround
No workaround is available.
V. Solution
Perform one of the following:
1) Upgrade your vulnerable system to 4-STABLE, 5-STABLE, or 6-STABLE,
or to the RELENG_6_1, RELENG_6_0, RELENG_5_5, RELENG_5_4, RELENG_5_3,
or RELENG_4_11 security branch dated after the correction date.
2) To patch your present system:
The following patches have been verified to apply to FreeBSD 4.11, 5.3,
5.4, 5.5, 6.0, and 6.1 systems.
a) Download the relevant patch from the location below, and verify the
detached PGP signature using your PGP utility.
# fetch http://security.FreeBSD.org/patches/SA-06:19/openssl.patch
# fetch http://security.FreeBSD.org/patches/SA-06:19/openssl.patch.asc
b) Execute the following commands as root:
# cd /usr/src
# patch < /path/to/patch
c) Recompile the operating system as described in
<URL: http://www.freebsd.org/handbook/makeworld.html> and reboot the
system.
NOTE: Any third-party applications, including those installed from the
FreeBSD ports collection, which are statically linked to libcrypto(3)
should be recompiled in order to use the corrected code.
VI. Correction details
The following list contains the revision numbers of each file that was
corrected in FreeBSD.
Branch Revision
Path
- -------------------------------------------------------------------------
RELENG_4
src/crypto/openssl/crypto/rsa/rsa_sign.c 1.1.1.1.2.6
RELENG_4_11
src/UPDATING 1.73.2.91.2.22
src/sys/conf/newvers.sh 1.44.2.39.2.25
src/crypto/openssl/crypto/rsa/rsa_sign.c 1.1.1.1.2.5.6.1
RELENG_5
src/crypto/openssl/crypto/rsa/rsa_sign.c 1.1.1.6.4.1
RELENG_5_5
src/UPDATING 1.342.2.35.2.4
src/sys/conf/newvers.sh 1.62.2.21.2.6
src/crypto/openssl/crypto/rsa/rsa_sign.c 1.1.1.6.16.1
RELENG_5_4
src/UPDATING 1.342.2.24.2.27
src/sys/conf/newvers.sh 1.62.2.18.2.23
src/crypto/openssl/crypto/rsa/rsa_sign.c 1.1.1.6.8.1
RELENG_5_3
src/UPDATING 1.342.2.13.2.36
src/sys/conf/newvers.sh 1.62.2.15.2.38
src/crypto/openssl/crypto/rsa/rsa_sign.c 1.1.1.6.6.1
RELENG_6
src/crypto/openssl/crypto/rsa/rsa_sign.c 1.1.1.6.10.1
RELENG_6_1
src/UPDATING 1.416.2.22.2.8
src/sys/conf/newvers.sh 1.69.2.11.2.8
src/crypto/openssl/crypto/rsa/rsa_sign.c 1.1.1.6.14.1
RELENG_6_0
src/UPDATING 1.416.2.3.2.16
src/sys/conf/newvers.sh 1.69.2.8.2.12
src/crypto/openssl/crypto/rsa/rsa_sign.c 1.1.1.6.12.1
- -------------------------------------------------------------------------
VII. References
http://www.openssl.org/news/secadv_20060905.txt
http://www.imc.org/ietf-openpgp/mail-archive/msg14307.html
http://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2006-4339
The latest revision of this advisory is available at
http://security.FreeBSD.org/advisories/FreeBSD-SA-06:19.openssl.asc
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