Bug 71538 - libwrap causes unexpected failures / denial of service
libwrap causes unexpected failures / denial of service
Product: Red Hat Linux
Classification: Retired
Component: xinetd (Show other bugs)
All Linux
medium Severity high
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Assigned To: Trond Eivind Glomsrxd
Brock Organ
Depends On:
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Reported: 2002-08-14 17:26 EDT by ae
Modified: 2007-04-18 12:45 EDT (History)
0 users

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Doc Type: Bug Fix
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Last Closed: 2002-08-14 17:30:18 EDT
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RHEL 7.3 requirements from Atomic Host:
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Description ae 2002-08-14 17:26:35 EDT
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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 17:30:12 EDT
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 15:46:21 EDT
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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