[Patch] Subversion 1.5 SASL doesn't work correctly with Kerberos cross-realm authentication

I once pined:

On 2008-08-12 14:00, Alec Kloss wrote:
> First off, Subversion's code is lovely to read.
>
> The subject pretty much says it all. The SASL support in
> Subversion 1.5 blindly removes realm specifiers from the user's
> authentication.
>
> There's a seatbelt early in cyrus_auth.c which protects against
> security problems associated with removing the realm as described
> by this comment:
>
> /* The only valid realm is user_realm (i.e. the repository's realm).
> If the user gave us another realm, complain. */
>
> Later, at the end of cyrus_auth_request() the realm is yanked off
> of the authenticated user, which creates the potential security
> issue that the seatbelt in cyrus_auth.c is protecting against:
>
> if ((p = strchr(user, '@')) != NULL)
> /* Drop the realm part. */
> b->user = apr_pstrndup(b->pool, user, p - (char *)user);
> else
>
> I guess I'd propose changing the default behavior to allow
> cross-realm and strip the realm part off in cyrus_auth_request()
> if-and-only-if it matches the configured "user_realm". I'd like to
> see a flag to disable the stripping of the realm entirely, as
> people with lots of cross-realm will almost certainly prefer that.
>
> (And while I'm commenting, has no one looked into logging in
> svnserve since 2005? It's kinda a big thing to be missing, at
> least among the paranoid.)

Please see attached patch. It works against 1.6.0 and trunk r36738.

-- 
Alec Kloss  alec_at_SetFilePointer.com   IM: daemonalec_at_gmail.com
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