Bug 71538 - libwrap causes unexpected failures / denial of service
Summary: libwrap causes unexpected failures / denial of service
Alias: None
Product: Red Hat Linux
Classification: Retired
Component: xinetd (Show other bugs)
(Show other bugs)
Version: 7.2
Hardware: All Linux
Target Milestone: ---
Assignee: Trond Eivind Glomsrxd
QA Contact: Brock Organ
Depends On:
TreeView+ depends on / blocked
Reported: 2002-08-14 21:26 UTC by ae
Modified: 2007-04-18 16:45 UTC (History)
0 users

Fixed In Version:
Doc Type: Bug Fix
Doc Text:
Story Points: ---
Clone Of:
Last Closed: 2002-08-14 21:30:18 UTC
Type: ---
Regression: ---
Mount Type: ---
Documentation: ---
Verified Versions:
Category: ---
oVirt Team: ---
RHEL 7.3 requirements from Atomic Host:
Cloudforms Team: ---

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Description ae 2002-08-14 21:26:35 UTC
From Bugzilla Helper:
User-Agent: Mozilla/5.0 Galeon/1.2.5 (X11; Linux i686; U;) Gecko/0

Description of problem:
I worked with tftp but this seems general.
If a client's ip does not resolve, then tftp does not start.
Error text is "libwrap refused connection to tftp from ...."
If "instances = UNLIMITED" and/or "per_source = UNLIMITED"
are ineffective (and they are in xinetd from 7.2 but seem
correct in xinetd-2.3.7-1), then the tftp service is lost.
Error text is "tftp service was deactivated because of looping".
If they ARE effective, then still no joy, and you pound syslogd.

Removing "only_from" expressions did not help.

Version-Release number of selected component (if applicable):

How reproducible:

Steps to Reproduce:
1.have on hand a tftp client whose ip does not resolve.
2.arrange for a dhcpd.conf entry for it, so that it will then
  attempt a tftp from linux box.
3.activate tftp on linux
4.connect the client machine to the net let it boot.

Actual Results:  tftp service is disrupted.

Additional info:

This likely of high interest to LTSP project.

Comment 1 ae 2002-08-14 21:30:12 UTC
As a workaround (tested in xinetd-2.3.7-1) say
     flags = NOLIBWRAP
which I suppose makes your "only_from" lines useless,
and access control becomes an ipchains problem.

Comment 2 Trond Eivind Glomsrxd 2002-08-15 19:46:21 UTC
No, NOLIBWRAP deals with /etc/hosts.{allow,deny}, not only_from.

Anyway, 2.3.7 is what is in rawhide currently..

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