Re: Git + mod_auth_kerb

[Jean-Francois Bouchard <jfbouchard@accedian.com>]

Hello,

Thanks for this info. This make a lot of sense system wise. For a user
point of view, it is a nightmare. Also, this break a lot of tools that
are waiting username/password authentication via HTTPS. (I name
Eclipse).

Also, I m not able to reproduce the kerberos login on Ubuntu 14.04. I
m asked to enter password even if a kerberos ticket is present and
this even when I've embedded the username in the URI.

Is there a better way to integrate Kerberos via HTTPS for git ?

Thanks,
JF

On Mon, Jul 21, 2014 at 7:17 PM, brian m. carlson
<sandals@crustytoothpaste.net> wrote:
> On Mon, Jul 21, 2014 at 05:06:50PM -0400, Jean-Francois Bouchard wrote:
>> Hello,
>>
>> We are currently working on a single sign on setup for our git install. We are
>> using git 2.0.2 (ubuntu) plus apache/2.2.22 mod_auth_kerb on the
>> server side. Here some scenario we are trying to accomplish :
>>
>> -Without Kerberos ticket stored.
>> Git ask for username/password.
>> Result = Authentication failed
>>
>> -Kerberos ticket in store and BAD password :
>> Git ask for username/password.
>> Result = Authentication failed
>>
>> -Kerberos ticket in Store entering good password :
>> Git ask for username/password.
>> Result = Authentication failed on some host, other works
>>
>> -Kerberos ticket in Store and embedding the username in the URI (aka
>> https://username@repo)
>> Git don't ask for anything or ask for password
>> Result = Works on some host, other request the password. (Will fail if
>> the kerberos ticket not in store)
>
> So git uses libcurl with CURLAUTH_ANY.  In order for authentication to
> work with libcurl, you have to supply a username.  If you specify it in
> the URL, the libcurl realizes that it can use Kerberos, and goes on its
> merry way.
>
> If you don't specify the username in the URL, git notices that
> authentication has failed, and asks the credential store for a username
> and password.  git does not know that a password is not needed, so the
> credential subsystem prompts for one anyway.
>
> I have mod_auth_kerb set up against Apache 2.4.9 at the moment, although
> I've used 2.2 before.  I always use a username in the URL, and if I get
> prompted for the password, I just Ctrl-C out and run kinit before
> pushing again.
>
> I don't have mod_auth_kerb set up to fall back to basic auth, but if you
> do, using a username and password should work properly.  You can use
> set the environment variable GIT_CURL_VERBOSE to 1 to see more
> information about what's actually going over the wire.
>
>> This is a very strange behaviour. It seems to be cause by the way
>> libcurl and git interact and the way the authentication goes
>> (Negociate first, then basic auth). I have tried to use the helper to
>> store invalid authentication information. With not much success.
>
> libcurl will always prefer something (anything) over basic auth, since
> basic auth is completely insecure unless you're using HTTPS.
>
> --
> brian m. carlson / brian with sandals: Houston, Texas, US
> +1 832 623 2791 | http://www.crustytoothpaste.net/~bmc | My opinion only
> OpenPGP: RSA v4 4096b: 88AC E9B2 9196 305B A994 7552 F1BA 225C 0223 B187

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