Bug 165432 - 'Request is a replay' error at SVN operations
'Request is a replay' error at SVN operations
Product: Fedora
Classification: Fedora
Component: mod_auth_kerb (Show other bugs)
All Linux
medium Severity medium
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Assigned To: Joe Orton
Depends On:
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Reported: 2005-08-09 05:55 EDT by Enrico Scholz
Modified: 2008-02-28 05:00 EST (History)
1 user (show)

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Fixed In Version:
Doc Type: Bug Fix
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Last Closed: 2008-02-28 05:00:37 EST
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Attachments (Terms of Use)
Quick'n dirty hack with sleep and retry-as-long-we-get-errors loop (871 bytes, patch)
2005-08-10 08:14 EDT, Enrico Scholz
no flags Details | Diff

  None (edit)
Description Enrico Scholz 2005-08-09 05:55:54 EDT
Description of problem:

When doing basic-auth style authentication (using login + password
instead of krb5 ticket) with mod_auth_kerb'erized SVN server, the
svn operations will fail randomly because the krb5 server detects

E.g. apache log shows

| [Tue Aug 09 11:23:15 2005] [error] [client] failed to verify krb5 credentials: Request is a replay

and the kdc log

| Aug  9 11:23:15 kerberos@rochester krb5kdc[17936]: TGS_REQ (3 etypes {16 1 3}) PROCESS_TGS: authtime 0,  <unknown client> for HTTP/XXXX, Request is a replay

I never saw these problems with GSSAPI based auth.

mod_auth_kerb seems to try to workaround the replay-cache problem and
makes some assumptions regarding krb5 internals. Can RH patches on
krb5 cause conflicts there?

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


How reproducible:


Additional info:

As both mod_auth_kerb and krb5 is heavily patched by RH, I do not want
to make upstream bugreports.

Apache was setup as

| <IfModule mod_auth_kerb.c>
|         <Directory />
|                 Krb5Keytab      /etc/httpd/conf/krb5.keytab
|                 KrbAuthRealms   ....
|         </Directory>
| </IfModule>
| <Location /development>
| 	DAV             svn
|         SVNPath         ....
|         SSLRequireSSL
|         AuthType        Kerberos
|         AuthGroupFile   /etc/httpd/conf/default-groups
|         Require group   ....
|         </LimitExcept>
| </Location>
Comment 1 Joe Orton 2005-08-09 06:03:45 EDT
We've been able to reproduce these with unpatched mod_auth_kerb too (see bug
157328) - I think it's a fundamental problem with how the Basic auth mode works.
Comment 2 Enrico Scholz 2005-08-09 06:14:58 EDT
(the mentioned bug seems to be unrelated ;))

http://comments.gmane.org/gmane.comp.apache.mod-auth-kerb.general/614 discusses
the same problem (but is a little bit out-of-context for me). They mention usage
of sizeof(k5_mutex_t) which depends on used krb5-lib and compiler flags.
Comment 3 Joe Orton 2005-08-09 06:27:30 EDT
Sorry, bug 157238.

Re: the thread you reference.  I hadn't realised that hack was actually enabled,
eww.  But I saw the replay errors when I was testing with the RHEL4 krb5-1.3.4.  

My understanding was that the error is being issued by the KDC on attempts to
verify the credentials several times very frequently - this seems to really be
an inevitable failure.
Comment 4 Enrico Scholz 2005-08-10 08:14:07 EDT
Created attachment 117599 [details]
Quick'n dirty hack with sleep and retry-as-long-we-get-errors loop

Description says it; it's a dirty hack which allows non-gssapi aware SVN
clients to work with my server.

Right fix would be probably something like using the same ccache for the same
connection/principal or even a mod_auth_kerb session. Currently it uses MEMORY:
which gets destroyed at each new authentication.

I am unexperienced in krb5 programming, so perhaps a better way is possible.
Comment 5 Christian Iseli 2007-01-22 06:09:42 EST
This report targets the FC3 or FC4 products, which have now been EOL'd.

Could you please check that it still applies to a current Fedora release, and
either update the target product or close it ?

Comment 6 petrosyan 2008-02-28 05:00:37 EST
Fedora Core 4 is no longer maintained.

Setting status to "INSUFFICIENT_DATA". If you can reproduce this bug in the
current Fedora release, please reopen this bug and assign it to the
corresponding Fedora version.

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