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FreeBSD inetd ident Server Vulnerability

FreeBSD inetd ident Server Vulnerability Privacy and Legal Notice CIAC INFORMATION BULLETIN L-038: FreeBSD inetd ident Server Vulnerability February 1, 2001 17:00 GMT


PROBLEM:	During internal auditing, the internal ident server in identd was found to incorrectly set group privileges according to the user. Due to ident using root's group permissions, users may read the first 16 (excluding initial whitespace) bytes of wheel-accessible files.
PLATFORM:	FreeBSD 3.x (all releases) and FressBSD 4.x (all releases).
DAMAGE:	Users could read the first 16 bytes of wheel-accessible files.
SOLUTION:	Upgrade the vulnerable FreeBSD system to 3.5-STABLE or 4.2-STABLE after the correction date or patch your present system. Refer to section V. of this bulletin for additional information.

VULNERABILITY ASSESSMENT:	The risk is LOW. Users can read the first 16 bytes of wheel-accessible files only if the inetd internal ident server is enabled.


[****** Start FreeBSD Advisory ******]


=============================================================================
FreeBSD-SA-01:11                                            Security Advisory
                                                                FreeBSD, Inc.

Topic: inetd ident server allows remote users to partially
       read arbitrary wheel-accessible files [REVISED]

Category:     core
Module:       inetd
Announced:    2001-01-29
Revised:      2001-01-29
Credits:      dynamo 
Affects:      FreeBSD 3.x (all releases)
              FreeBSD 4.x (all releases)
Corrected:    2000-11-25 (FreeBSD 4.2-STABLE)
              2001-01-26 (FreeBSD 3.5-STABLE)
FreeBSD only: Yes

0. Revision History

v1.0 2001-01-29 Initial release
v1.1 2001-01-29 Correctly credit original problem reporter

I. Background

The inetd ident server is an implementation of the RFC1413
identification server which returns the local username of the
user connecting to a remote service.

II. Problem Description

During internal auditing, the internal ident server in inetd was found
to incorrectly set group privileges according to the user. Due to
ident using root's group permissions, users may read the first 16
(excluding initial whitespace) bytes of wheel-accessible files.

All released versions of FreeBSD prior to the correction date
including FreeBSD 3.5.1 and FreeBSD 4.2 are vulnerable.

III. Impact

Users can read the first 16 bytes of wheel-accessible files.
To determine which may be potentially read, execute the following
command as root:

# find / -group wheel \( -perm -40 -a \! -perm +4 \) -ls

The inetd internal ident server is not enabled by default. If you
have not enabled the ident portion of inetd, you are not vulnerable.

IV. Workaround

Disable the internal ident server, if enabled: comment out all lines
beginning with "auth" in /etc/inetd.conf, then restart inetd by
sending it a SIGHUP:

# killall -HUP inetd

V. Solution

One of the following:

Upgrade the vulnerable FreeBSD system to 3.5-STABLE or 4.2-STABLE
after the correction date.

To patch your present system: download the relevant patch from the
below location, and execute the following commands as root:

[FreeBSD 4.2 base system]

# fetch ftp://ftp.FreeBSD.org/pub/FreeBSD/CERT/patches/SA-01:11/inetd-4.2.patch
# fetch ftp://ftp.FreeBSD.org/pub/FreeBSD/CERT/patches/SA-01:11/inetd-4.2.patch.asc

Verify the detached PGP signature using your PGP utility.

# cd /usr/src/usr.sbin/inetd
# patch -p < /path/to/patch
# make depend && make all install
# killall -HUP inetd

[FreeBSD 3.5.1 base system]

# fetch ftp://ftp.FreeBSD.org/pub/FreeBSD/CERT/patches/SA-01:11/inetd-3.5.1.patch
# fetch ftp://ftp.FreeBSD.org/pub/FreeBSD/CERT/patches/SA-01:11/inetd-3.5.1.patch.asc

Verify the detached PGP signature using your PGP utility.

# cd /usr/src/usr.sbin/inetd
# patch -p < /path/to/patch
# make depend && make all install
# killall -HUP inetd


[****** End FreeBSD Advisory ******]

CIAC wishes to acknowledge the contributions of FreeBSD for the information contained in this bulletin.

CIAC services are available to DOE, DOE Contractors, and the NIH. CIAC can be contacted at:

    Voice:          +1 925-422-8193 (7 x 24)
    FAX:            +1 925-423-8002
    STU-III:        +1 925-423-2604
    E-mail:          ciac@llnl.gov
    World Wide Web:  http://www.ciac.org/
                     http://ciac.llnl.gov
                     (same machine -- either one will work)
    Anonymous FTP:   ftp.ciac.org
                     ciac.llnl.gov
                     (same machine -- either one will work)

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