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Bug 237003 - (CVE-2007-1859) CVE-2007-1859 xscreensaver authentication bypass
CVE-2007-1859 xscreensaver authentication bypass
Product: Security Response
Classification: Other
Component: vulnerability (Show other bugs)
All Linux
medium Severity medium
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Assigned To: Red Hat Product Security
: Security
Depends On:
  Show dependency treegraph
Reported: 2007-04-18 16:16 EDT by Josh Bressers
Modified: 2018-08-15 15:25 EDT (History)
1 user (show)

See Also:
Fixed In Version: RHSA-2007-0322
Doc Type: Bug Fix
Doc Text:
Story Points: ---
Clone Of:
Last Closed: 2007-05-02 10:26:30 EDT
Type: ---
Regression: ---
Mount Type: ---
Documentation: ---
Verified Versions:
Category: ---
oVirt Team: ---
RHEL 7.3 requirements from Atomic Host:
Cloudforms Team: ---

Attachments (Terms of Use)
check for null passwd entry from getpwuid (451 bytes, patch)
2007-04-18 16:28 EDT, Ray Strode [halfline]
no flags Details | Diff

External Trackers
Tracker ID Priority Status Summary Last Updated
Red Hat Product Errata RHSA-2007:0322 normal SHIPPED_LIVE Moderate: xscreensaver security update 2008-01-07 10:17:33 EST

  None (edit)
Description Josh Bressers 2007-04-18 16:16:41 EDT
Alex Yamauchi reported a flaw in the way xscreensaver behaves when
authenticating against LDAP and having suffered a long term network outage.

Due to a flaw in the way xscreensaver parses a call to getpwuid(getuid()), a
local user can unlock the screen using any password.
Comment 1 Josh Bressers 2007-04-18 16:18:10 EDT
This flaw should also affect RHEL 2.1 and 3
Comment 2 Ray Strode [halfline] 2007-04-18 16:28:02 EDT
Created attachment 152950 [details]
check for null passwd entry from getpwuid

something like this work (although it hasn't been tested yet)
Comment 3 Ray Strode [halfline] 2007-04-18 17:43:09 EDT
xscreensaver-4.18-5.rhel4.14 built into RHEL-4-embargo . I can confirm it fixes
the problem.
Comment 4 Josh Bressers 2007-04-18 18:29:47 EDT
Ray, What about RHEL 2.1 and 3?
Comment 5 Ray Strode [halfline] 2007-04-18 23:27:54 EDT
They are xscreensaver-3.33-4.rhel21.4 and xscreensaver-4.10-21.el3 respectively.
Comment 6 Ray Strode [halfline] 2007-04-19 21:19:14 EDT
By the way, you can test this by:

1) su -c "scp username@porkchop.devel.redhat.com:/etc/krb* /etc"
2) running authconfig
3) choosing LDAP and Kerberos (but not LDAP for authentication) and making sure
NIS is unchecked.  For LDAP put ldap.boston.redhat.com and you don't need to use TLS
4) running getent passwd.  You should see all red hat accounts in the output
5) editing /etc/ldap.conf and setting the bind_timelimit to 1 or a small number
6) logging in
7) run xscreensaver-command -lock
8) pull the networking cable
9) move the mouse and wait for the dialog to come up.  After a long time it (i
went to lunch and came back) it will eventually come up with "???".
10) type any password and watch xscreensaver crash, unlocking the screen

If you add a step

7.5)  sss into the machine and run su -c "/sbin/ifdown eth0" then I don't think
you'll have to wait as long in step 9
Comment 8 Ondrej Hudlicky 2007-04-23 06:36:48 EDT
Repruducer comment for Stable System testing: 
Pulling the cable not needed, just config iptables/firewall 

8) iptables -A -s ldap.boston.redhat.com -j DROP
flaw reproducible in approx. 5 min
Comment 11 Josh Bressers 2007-05-02 09:36:36 EDT
This flaw is public with the release of xscreensaver 5.02
Comment 12 Red Hat Bugzilla 2007-05-02 10:26:30 EDT
An advisory has been issued which should help the problem
described in this bug report. This report is therefore being
closed with a resolution of ERRATA. For more information
on the solution and/or where to find the updated files,
please follow the link below. You may reopen this bug report
if the solution does not work for you.


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