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Category:   Application (Security)  >   OpenSSH Vendors:   OpenSSH.org
(Red Hat Issues Fix) OpenSSH's Sftp-server Subsystem Lets Authorized Remote Users with Restricted Keypairs Obtain Additional Access on the Server
SecurityTracker Alert ID:  1002870
SecurityTracker URL:  http://securitytracker.com/id/1002870
CVE Reference:   GENERIC-MAP-NOMATCH   (Links to External Site)
Date:  Nov 30 2001
Impact:   Disclosure of system information, Disclosure of user information, Modification of system information, Modification of user information
Fix Available:  Yes  Vendor Confirmed:  Yes  
Version(s): 2.9, 2.9p2
Description:   A vulnerability was reported in OpenSSH's sftp-server subsystem. Under certain configuration conditions, an authorized remote user can gain additional access on the server.

It is reported that when keypairs and the ~/.ssh/authorized_keys2 file are used to enable remote execution of commands via OpenSSH's sshd and sshd is configured to provide sftp service via the sftp-server subsystem, this vulnerability can be triggered. Authorized remote users with access permitted via "restricted" keypairs can apparently gain additional access on the server side. The report notes that, in most cases, sftp can be used, regardless of various restrictions. An authorized remote user can circumvent the authorized_keys2 command= restriction and other restrictions (e.g., obtaining the regular shell access that the server was configured to deny it).

OpenSSH's sftp implementation includes commands to get, replace, delete, change permissions, and change ownership of files/directories.

It is reported that OpenSSH 2.9 and 2.9p2 have the sftp subsystem enabled by default.

Impact:   An authorized remote user with access permitted via 'restricted' keypairs can use the sftp subsystem, regardless of various restrictions. This allows the remote user to access the server and view, replace, and delete files and change permissions and ownership of files and directories on the server.
Solution:   The vendor has released a fix:

Red Hat Linux 7.0:

SRPMS:
ftp://updates.redhat.com/7.0/en/os/SRPMS/openssh-2.9p2-10.7.src.rpm

alpha:
ftp://updates.redhat.com/7.0/en/os/alpha/openssh-2.9p2-10.7.alpha.rpm
ftp://updates.redhat.com/7.0/en/os/alpha/openssh-askpass-2.9p2-10.7.alpha.rpm
ftp://updates.redhat.com/7.0/en/os/alpha/openssh-askpass-gnome-2.9p2-10.7.alpha.rpm
ftp://updates.redhat.com/7.0/en/os/alpha/openssh-clients-2.9p2-10.7.alpha.rpm
ftp://updates.redhat.com/7.0/en/os/alpha/openssh-server-2.9p2-10.7.alpha.rpm

i386:
ftp://updates.redhat.com/7.0/en/os/i386/openssh-2.9p2-10.7.i386.rpm
ftp://updates.redhat.com/7.0/en/os/i386/openssh-askpass-2.9p2-10.7.i386.rpm
ftp://updates.redhat.com/7.0/en/os/i386/openssh-askpass-gnome-2.9p2-10.7.i386.rpm
ftp://updates.redhat.com/7.0/en/os/i386/openssh-clients-2.9p2-10.7.i386.rpm
ftp://updates.redhat.com/7.0/en/os/i386/openssh-server-2.9p2-10.7.i386.rpm

Red Hat Linux 7.1:

SRPMS:
ftp://updates.redhat.com/7.1/en/os/SRPMS/openssh-2.9p2-10.7.src.rpm

alpha:
ftp://updates.redhat.com/7.1/en/os/alpha/openssh-2.9p2-10.7.alpha.rpm
ftp://updates.redhat.com/7.1/en/os/alpha/openssh-askpass-2.9p2-10.7.alpha.rpm
ftp://updates.redhat.com/7.1/en/os/alpha/openssh-askpass-gnome-2.9p2-10.7.alpha.rpm
ftp://updates.redhat.com/7.1/en/os/alpha/openssh-clients-2.9p2-10.7.alpha.rpm
ftp://updates.redhat.com/7.1/en/os/alpha/openssh-server-2.9p2-10.7.alpha.rpm

i386:
ftp://updates.redhat.com/7.1/en/os/i386/openssh-2.9p2-10.7.i386.rpm
ftp://updates.redhat.com/7.1/en/os/i386/openssh-askpass-2.9p2-10.7.i386.rpm
ftp://updates.redhat.com/7.1/en/os/i386/openssh-askpass-gnome-2.9p2-10.7.i386.rpm
ftp://updates.redhat.com/7.1/en/os/i386/openssh-clients-2.9p2-10.7.i386.rpm
ftp://updates.redhat.com/7.1/en/os/i386/openssh-server-2.9p2-10.7.i386.rpm

ia64:
ftp://updates.redhat.com/7.1/en/os/ia64/openssh-2.9p2-10.7.ia64.rpm
ftp://updates.redhat.com/7.1/en/os/ia64/openssh-askpass-2.9p2-10.7.ia64.rpm
ftp://updates.redhat.com/7.1/en/os/ia64/openssh-askpass-gnome-2.9p2-10.7.ia64.rpm
ftp://updates.redhat.com/7.1/en/os/ia64/openssh-clients-2.9p2-10.7.ia64.rpm
ftp://updates.redhat.com/7.1/en/os/ia64/openssh-server-2.9p2-10.7.ia64.rpm

Red Hat Linux 7.2:

SRPMS:
ftp://updates.redhat.com/7.2/en/os/SRPMS/openssh-2.9p2-11.src.rpm

i386:
ftp://updates.redhat.com/7.2/en/os/i386/openssh-2.9p2-11.i386.rpm
ftp://updates.redhat.com/7.2/en/os/i386/openssh-askpass-2.9p2-11.i386.rpm
ftp://updates.redhat.com/7.2/en/os/i386/openssh-askpass-gnome-2.9p2-11.i386.rpm
ftp://updates.redhat.com/7.2/en/os/i386/openssh-clients-2.9p2-11.i386.rpm
ftp://updates.redhat.com/7.2/en/os/i386/openssh-server-2.9p2-11.i386.rpm

The verification checksums are:

MD5 sum Package Name
--------------------------------------------------------------------------
6aaf629a210dea1988e7631e60072681 7.0/en/os/SRPMS/openssh-2.9p2-10.7.src.rpm
340e97c4aa1b88cb83b29929d2031a8b 7.0/en/os/alpha/openssh-2.9p2-10.7.alpha.rpm
833c1efcc3f0b501b2f95dc0225a1110 7.0/en/os/alpha/openssh-askpass-2.9p2-10.7.alpha.rpm
6afbdb015d3ae72cf34c5005212ce14d 7.0/en/os/alpha/openssh-askpass-gnome-2.9p2-10.7.alpha.rpm
890b6a4623bd251cbb509e0f52976aa8 7.0/en/os/alpha/openssh-clients-2.9p2-10.7.alpha.rpm
38dcfb8105a2585eb66166509ffb8ec3 7.0/en/os/alpha/openssh-server-2.9p2-10.7.alpha.rpm
206678dd9fed4e895282fdf944026fd5 7.0/en/os/i386/openssh-2.9p2-10.7.i386.rpm
932b8383849cd3c72575026873e04b2a 7.0/en/os/i386/openssh-askpass-2.9p2-10.7.i386.rpm
451ad9f475a4816b7def9f4737a2910f 7.0/en/os/i386/openssh-askpass-gnome-2.9p2-10.7.i386.rpm
e6aaa5454932133eb5140d5aa8694c23 7.0/en/os/i386/openssh-clients-2.9p2-10.7.i386.rpm
2e2c50953866c77510e320587b2b763a 7.0/en/os/i386/openssh-server-2.9p2-10.7.i386.rpm
6aaf629a210dea1988e7631e60072681 7.1/en/os/SRPMS/openssh-2.9p2-10.7.src.rpm
340e97c4aa1b88cb83b29929d2031a8b 7.1/en/os/alpha/openssh-2.9p2-10.7.alpha.rpm
833c1efcc3f0b501b2f95dc0225a1110 7.1/en/os/alpha/openssh-askpass-2.9p2-10.7.alpha.rpm
6afbdb015d3ae72cf34c5005212ce14d 7.1/en/os/alpha/openssh-askpass-gnome-2.9p2-10.7.alpha.rpm
890b6a4623bd251cbb509e0f52976aa8 7.1/en/os/alpha/openssh-clients-2.9p2-10.7.alpha.rpm
38dcfb8105a2585eb66166509ffb8ec3 7.1/en/os/alpha/openssh-server-2.9p2-10.7.alpha.rpm
206678dd9fed4e895282fdf944026fd5 7.1/en/os/i386/openssh-2.9p2-10.7.i386.rpm
932b8383849cd3c72575026873e04b2a 7.1/en/os/i386/openssh-askpass-2.9p2-10.7.i386.rpm
451ad9f475a4816b7def9f4737a2910f 7.1/en/os/i386/openssh-askpass-gnome-2.9p2-10.7.i386.rpm
e6aaa5454932133eb5140d5aa8694c23 7.1/en/os/i386/openssh-clients-2.9p2-10.7.i386.rpm
2e2c50953866c77510e320587b2b763a 7.1/en/os/i386/openssh-server-2.9p2-10.7.i386.rpm
40f477635b6440dfd46afe59e28bf8f9 7.1/en/os/ia64/openssh-2.9p2-10.7.ia64.rpm
702b0a6703da90a7cca6037f6947794f 7.1/en/os/ia64/openssh-askpass-2.9p2-10.7.ia64.rpm
60f72ff95c7c3d41b56b3cb969e6494e 7.1/en/os/ia64/openssh-askpass-gnome-2.9p2-10.7.ia64.rpm
5c4e3ae0ce17e742b8dc3acd807246ec 7.1/en/os/ia64/openssh-clients-2.9p2-10.7.ia64.rpm
3400b7fb0337971f652a1e6403fb234d 7.1/en/os/ia64/openssh-server-2.9p2-10.7.ia64.rpm
90ce862375e8410ed5c5a29d9f23ed63 7.2/en/os/SRPMS/openssh-2.9p2-11.src.rpm
ee061bdb5d9907ae65259c60823545db 7.2/en/os/i386/openssh-2.9p2-11.i386.rpm
8f589e90d818865053666bcfeed32bdb 7.2/en/os/i386/openssh-askpass-2.9p2-11.i386.rpm
3233cdafc1f62b926414b05445415548 7.2/en/os/i386/openssh-askpass-gnome-2.9p2-11.i386.rpm
3b7ef488182ae3afbd639e74e7eed8cc 7.2/en/os/i386/openssh-clients-2.9p2-11.i386.rpm
3358900ffa3d3327c9cfe79b365c1464 7.2/en/os/i386/openssh-server-2.9p2-11.i386.rpm

See the Source Message for the vendor's advisory containing directions on how to apply the appropriate fix.

Vendor URL:  www.openssh.org/ (Links to External Site)
Cause:   Access control error
Underlying OS:  Linux (Red Hat Linux)

Message History:   This archive entry is a follow-up to the message listed below.
Sep 20 2001 OpenSSH's Sftp-server Subsystem Lets Authorized Remote Users with Restricted Keypairs Obtain Additional Access on the Server



 Source Message Contents

Subject:  [RHSA-2001:154-06] Updated OpenSSH packages available


---------------------------------------------------------------------
                   Red Hat, Inc. Red Hat Security Advisory

Synopsis:          Updated OpenSSH packages available
Advisory ID:       RHSA-2001:154-06
Issue date:        2001-11-13
Updated on:        2001-11-30
Product:           Red Hat Linux
Keywords:          openssh restricted commands echo
Cross references:  
Obsoletes:         RHSA-2001:114
---------------------------------------------------------------------

1. Topic:

Updated OpenSSH packages are now available for Red Hat Linux 7, 7.1, and
7.2.  These updates fix a bug in handling of restricted keys which may
allow users to bypass command restrictions by using subsystems and a subtle
bug which might aid a passive analysis attack.

2. Relevant releases/architectures:

Red Hat Linux 7.0 - alpha, i386

Red Hat Linux 7.1 - alpha, i386, ia64

Red Hat Linux 7.2 - i386

3. Problem description:

OpenSSH versions prior to 2.9.9, when configured to provide sftp access
using the subsystem feature, allows remote authenticated users to bypass
authorized_keys2 "command=" restrictions by using sftp commands.

The Common Vulnerabilities and Exposures project (cve.mitre.org) has
assigned the name CAN-2001-0816 to this issue.

OpenSSH 2.9 also contained a subtle bug in the routines which attempt to
confound an attacker using passive analysis, which would cause it to send
two confounding packets instead of one when a client finished sending it a
password.

Red Hat would like to thank Solar Designer and Markus Friedl for assisting
with the patches.

4. Solution:

Before applying this update, make sure all previously released errata
relevant to your system have been applied.

To update all RPMs for your particular architecture, run:

rpm -Fvh [filenames]

where [filenames] is a list of the RPMs you wish to upgrade.  Only those
RPMs which are currently installed will be updated.  Those RPMs which are
not installed but included in the list will not be updated.  Note that you
can also use wildcards (*.rpm) if your current directory *only* contains the
desired RPMs.

Please note that this update is also available via Red Hat Network.  Many
people find this an easier way to apply updates.  To use Red Hat Network,
launch the Red Hat Update Agent with the following command:

up2date

This will start an interactive process that will result in the appropriate
RPMs being upgraded on your system.

5. Bug IDs fixed (http://bugzilla.redhat.com/bugzilla for more info):



6. RPMs required:

Red Hat Linux 7.0:

SRPMS:
ftp://updates.redhat.com/7.0/en/os/SRPMS/openssh-2.9p2-10.7.src.rpm

alpha:
ftp://updates.redhat.com/7.0/en/os/alpha/openssh-2.9p2-10.7.alpha.rpm
ftp://updates.redhat.com/7.0/en/os/alpha/openssh-askpass-2.9p2-10.7.alpha.rpm
ftp://updates.redhat.com/7.0/en/os/alpha/openssh-askpass-gnome-2.9p2-10.7.alpha.rpm
ftp://updates.redhat.com/7.0/en/os/alpha/openssh-clients-2.9p2-10.7.alpha.rpm
ftp://updates.redhat.com/7.0/en/os/alpha/openssh-server-2.9p2-10.7.alpha.rpm

i386:
ftp://updates.redhat.com/7.0/en/os/i386/openssh-2.9p2-10.7.i386.rpm
ftp://updates.redhat.com/7.0/en/os/i386/openssh-askpass-2.9p2-10.7.i386.rpm
ftp://updates.redhat.com/7.0/en/os/i386/openssh-askpass-gnome-2.9p2-10.7.i386.rpm
ftp://updates.redhat.com/7.0/en/os/i386/openssh-clients-2.9p2-10.7.i386.rpm
ftp://updates.redhat.com/7.0/en/os/i386/openssh-server-2.9p2-10.7.i386.rpm

Red Hat Linux 7.1:

SRPMS:
ftp://updates.redhat.com/7.1/en/os/SRPMS/openssh-2.9p2-10.7.src.rpm

alpha:
ftp://updates.redhat.com/7.1/en/os/alpha/openssh-2.9p2-10.7.alpha.rpm
ftp://updates.redhat.com/7.1/en/os/alpha/openssh-askpass-2.9p2-10.7.alpha.rpm
ftp://updates.redhat.com/7.1/en/os/alpha/openssh-askpass-gnome-2.9p2-10.7.alpha.rpm
ftp://updates.redhat.com/7.1/en/os/alpha/openssh-clients-2.9p2-10.7.alpha.rpm
ftp://updates.redhat.com/7.1/en/os/alpha/openssh-server-2.9p2-10.7.alpha.rpm

i386:
ftp://updates.redhat.com/7.1/en/os/i386/openssh-2.9p2-10.7.i386.rpm
ftp://updates.redhat.com/7.1/en/os/i386/openssh-askpass-2.9p2-10.7.i386.rpm
ftp://updates.redhat.com/7.1/en/os/i386/openssh-askpass-gnome-2.9p2-10.7.i386.rpm
ftp://updates.redhat.com/7.1/en/os/i386/openssh-clients-2.9p2-10.7.i386.rpm
ftp://updates.redhat.com/7.1/en/os/i386/openssh-server-2.9p2-10.7.i386.rpm

ia64:
ftp://updates.redhat.com/7.1/en/os/ia64/openssh-2.9p2-10.7.ia64.rpm
ftp://updates.redhat.com/7.1/en/os/ia64/openssh-askpass-2.9p2-10.7.ia64.rpm
ftp://updates.redhat.com/7.1/en/os/ia64/openssh-askpass-gnome-2.9p2-10.7.ia64.rpm
ftp://updates.redhat.com/7.1/en/os/ia64/openssh-clients-2.9p2-10.7.ia64.rpm
ftp://updates.redhat.com/7.1/en/os/ia64/openssh-server-2.9p2-10.7.ia64.rpm

Red Hat Linux 7.2:

SRPMS:
ftp://updates.redhat.com/7.2/en/os/SRPMS/openssh-2.9p2-11.src.rpm

i386:
ftp://updates.redhat.com/7.2/en/os/i386/openssh-2.9p2-11.i386.rpm
ftp://updates.redhat.com/7.2/en/os/i386/openssh-askpass-2.9p2-11.i386.rpm
ftp://updates.redhat.com/7.2/en/os/i386/openssh-askpass-gnome-2.9p2-11.i386.rpm
ftp://updates.redhat.com/7.2/en/os/i386/openssh-clients-2.9p2-11.i386.rpm
ftp://updates.redhat.com/7.2/en/os/i386/openssh-server-2.9p2-11.i386.rpm



7. Verification:

MD5 sum                          Package Name
--------------------------------------------------------------------------
6aaf629a210dea1988e7631e60072681 7.0/en/os/SRPMS/openssh-2.9p2-10.7.src.rpm
340e97c4aa1b88cb83b29929d2031a8b 7.0/en/os/alpha/openssh-2.9p2-10.7.alpha.rpm
833c1efcc3f0b501b2f95dc0225a1110 7.0/en/os/alpha/openssh-askpass-2.9p2-10.7.alpha.rpm
6afbdb015d3ae72cf34c5005212ce14d 7.0/en/os/alpha/openssh-askpass-gnome-2.9p2-10.7.alpha.rpm
890b6a4623bd251cbb509e0f52976aa8 7.0/en/os/alpha/openssh-clients-2.9p2-10.7.alpha.rpm
38dcfb8105a2585eb66166509ffb8ec3 7.0/en/os/alpha/openssh-server-2.9p2-10.7.alpha.rpm
206678dd9fed4e895282fdf944026fd5 7.0/en/os/i386/openssh-2.9p2-10.7.i386.rpm
932b8383849cd3c72575026873e04b2a 7.0/en/os/i386/openssh-askpass-2.9p2-10.7.i386.rpm
451ad9f475a4816b7def9f4737a2910f 7.0/en/os/i386/openssh-askpass-gnome-2.9p2-10.7.i386.rpm
e6aaa5454932133eb5140d5aa8694c23 7.0/en/os/i386/openssh-clients-2.9p2-10.7.i386.rpm
2e2c50953866c77510e320587b2b763a 7.0/en/os/i386/openssh-server-2.9p2-10.7.i386.rpm
6aaf629a210dea1988e7631e60072681 7.1/en/os/SRPMS/openssh-2.9p2-10.7.src.rpm
340e97c4aa1b88cb83b29929d2031a8b 7.1/en/os/alpha/openssh-2.9p2-10.7.alpha.rpm
833c1efcc3f0b501b2f95dc0225a1110 7.1/en/os/alpha/openssh-askpass-2.9p2-10.7.alpha.rpm
6afbdb015d3ae72cf34c5005212ce14d 7.1/en/os/alpha/openssh-askpass-gnome-2.9p2-10.7.alpha.rpm
890b6a4623bd251cbb509e0f52976aa8 7.1/en/os/alpha/openssh-clients-2.9p2-10.7.alpha.rpm
38dcfb8105a2585eb66166509ffb8ec3 7.1/en/os/alpha/openssh-server-2.9p2-10.7.alpha.rpm
206678dd9fed4e895282fdf944026fd5 7.1/en/os/i386/openssh-2.9p2-10.7.i386.rpm
932b8383849cd3c72575026873e04b2a 7.1/en/os/i386/openssh-askpass-2.9p2-10.7.i386.rpm
451ad9f475a4816b7def9f4737a2910f 7.1/en/os/i386/openssh-askpass-gnome-2.9p2-10.7.i386.rpm
e6aaa5454932133eb5140d5aa8694c23 7.1/en/os/i386/openssh-clients-2.9p2-10.7.i386.rpm
2e2c50953866c77510e320587b2b763a 7.1/en/os/i386/openssh-server-2.9p2-10.7.i386.rpm
40f477635b6440dfd46afe59e28bf8f9 7.1/en/os/ia64/openssh-2.9p2-10.7.ia64.rpm
702b0a6703da90a7cca6037f6947794f 7.1/en/os/ia64/openssh-askpass-2.9p2-10.7.ia64.rpm
60f72ff95c7c3d41b56b3cb969e6494e 7.1/en/os/ia64/openssh-askpass-gnome-2.9p2-10.7.ia64.rpm
5c4e3ae0ce17e742b8dc3acd807246ec 7.1/en/os/ia64/openssh-clients-2.9p2-10.7.ia64.rpm
3400b7fb0337971f652a1e6403fb234d 7.1/en/os/ia64/openssh-server-2.9p2-10.7.ia64.rpm
90ce862375e8410ed5c5a29d9f23ed63 7.2/en/os/SRPMS/openssh-2.9p2-11.src.rpm
ee061bdb5d9907ae65259c60823545db 7.2/en/os/i386/openssh-2.9p2-11.i386.rpm
8f589e90d818865053666bcfeed32bdb 7.2/en/os/i386/openssh-askpass-2.9p2-11.i386.rpm
3233cdafc1f62b926414b05445415548 7.2/en/os/i386/openssh-askpass-gnome-2.9p2-11.i386.rpm
3b7ef488182ae3afbd639e74e7eed8cc 7.2/en/os/i386/openssh-clients-2.9p2-11.i386.rpm
3358900ffa3d3327c9cfe79b365c1464 7.2/en/os/i386/openssh-server-2.9p2-11.i386.rpm
 

These packages are GPG signed by Red Hat, Inc. for security.  Our key
is available at:
    http://www.redhat.com/about/contact/pgpkey.html

You can verify each package with the following command:
    rpm --checksig  <filename>

If you only wish to verify that each package has not been corrupted or
tampered with, examine only the md5sum with the following command:
    rpm --checksig --nogpg <filename>

8. References:

http://cve.mitre.org/cgi-bin/cvename.cgi?name=CAN-2001-0816
http://marc.theaimsgroup.com/?l=openssh-unix-dev&m=100156674610824&w=2


Copyright(c) 2000, 2001 Red Hat, Inc.



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