Propust je posljedica pogreške u DES implementaciji korištenoj u crypt() funkciji. Točnije, propust se očituje pri obradi lozinki koje sadrže znakove koji se nemogu prikazati kao 7-bit ASCII. Ako lozinka sadrži znak čiji je najznačajniji bit postavljen na (0x80), taj znak i svi znakovi iza njega se ignoriraju.
Posljedica:
Nedostatak je moguće iskoristiti za utjecaj na integritet podataka.
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FreeBSD-SA-12:02.crypt Security Advisory
The FreeBSD Project
Topic: Incorrect crypt() hashing
Category: core
Module: libcrypt
Announced: 2012-05-30
Credits: Rubin Xu, Joseph Bonneau, Donting Yu
Affects: All supported versions of FreeBSD.
Corrected: 2012-05-30 12:01:28 UTC (RELENG_7, 7.4-STABLE)
2012-05-30 12:01:28 UTC (RELENG_7_4, 7.4-RELEASE-p8)
2012-05-30 12:01:28 UTC (RELENG_8, 8.3-STABLE)
2012-05-30 12:01:28 UTC (RELENG_8_3, 8.3-RELEASE-p2)
2012-05-30 12:01:28 UTC (RELENG_8_2, 8.2-RELEASE-p8)
2012-05-30 12:01:28 UTC (RELENG_8_1, 8.1-RELEASE-p10)
2012-05-30 12:01:28 UTC (RELENG_9, 9.0-STABLE)
2012-05-30 12:01:28 UTC (RELENG_9_0, 9.0-RELEASE-p2)
CVE Name: CVE-2012-2143
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
The crypt(3) function performs password hashing with additional code added
to deter key search attempts.
II. Problem Description
There is a programming error in the DES implementation used in crypt()
when handling input which contains characters that can not be represented
with 7-bit ASCII.
III. Impact
When the input contains characters with only the most significant bit set
(0x80), that character and all characters after it will be ignored.
IV. Workaround
No workaround is available, but systems not using crypt(), or which only
use it to handle 7-bit ASCII are not vulnerable. Note that, because
DES does not have the computational complexity to defeat brute force
search on modern computers, it is not recommended for new applications.
V. Solution
Perform one of the following:
1) Upgrade your vulnerable system to 7-STABLE, 8-STABLE, or 9-STABLE,
or to the RELENG_7_4, RELENG_8_3, RELENG_8_2, RELENG_8_1, or RELENG_9_0
security branch dated after the correction date.
2) To update your vulnerable system via a source code patch:
The following patches have been verified to apply to FreeBSD 7.4,
8.3, 8.2, 8.1 and 9.0 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-12:02/crypt.patch
# fetch http://security.FreeBSD.org/patches/SA-12:02/crypt.patch.asc
# cd /usr/src
# patch < /path/to/patch
# cd /usr/src/lib/libcrypt
# make obj && make depend && make && make install
NOTE: On the amd64 platform, the above procedure will not update the
lib32 (i386 compatibility) libraries. On amd64 systems where the i386
compatibility libraries are used, the operating system should instead
be recompiled as described in
<URL:http://www.FreeBSD.org/handbook/makeworld.html>
3) To update your vulnerable system via a binary patch:
Systems running 7.4-RELEASE, 8.3-RELEASE, 8.2-RELEASE, 8.1-RELEASE,
or 9.0-RELEASE on the i386 or amd64 platforms can be updated via the
freebsd-update(8) utility:
# freebsd-update fetch
# freebsd-update install
VI. Correction details
The following list contains the revision numbers of each file that was
corrected in FreeBSD.
CVS:
Branch Revision
Path
- -------------------------------------------------------------------------
RELENG_7
src/secure/lib/libcrypt/crypt-des.c 1.16.24.1
RELENG_7_4
src/UPDATING 1.507.2.36.2.10
src/sys/conf/newvers.sh 1.72.2.18.2.13
src/secure/lib/libcrypt/crypt-des.c 1.16.40.2
RELENG_8
src/secure/lib/libcrypt/crypt-des.c 1.16.36.2
RELENG_8_3
src/UPDATING 1.632.2.26.2.4
src/sys/conf/newvers.sh 1.83.2.15.2.6
src/secure/lib/libcrypt/crypt-des.c 1.16.36.1.8.2
RELENG_8_2
src/UPDATING 1.632.2.19.2.10
src/sys/conf/newvers.sh 1.83.2.12.2.13
src/secure/lib/libcrypt/crypt-des.c 1.16.36.1.6.2
RELENG_8_1
src/UPDATING 1.632.2.14.2.13
src/sys/conf/newvers.sh 1.83.2.10.2.14
src/secure/lib/libcrypt/crypt-des.c 1.16.36.1.4.2
RELENG_9
src/secure/lib/libcrypt/crypt-des.c 1.16.42.2
RELENG_9_0
src/UPDATING 1.702.2.4.2.4
src/sys/conf/newvers.sh 1.95.2.4.2.6
src/secure/lib/libcrypt/crypt-des.c 1.16.42.1.2.2
- -------------------------------------------------------------------------
Subversion:
Branch/path Revision
- -------------------------------------------------------------------------
stable/7/ r236304
releng/7.4/ r236304
stable/8/ r236304
releng/8.3/ r236304
releng/8.2/ r236304
releng/8.1/ r236304
stable/9/ r236304
releng/9.0/ r236304
- -------------------------------------------------------------------------
VII. References
http://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2012-2143
The latest revision of this advisory is available at
http://security.FreeBSD.org/advisories/FreeBSD-SA-12:02.crypt.asc
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