Re: [PATCH 1/2] doc/http-backend: clarify "half-auth" repo configuration

> When the http-backend is set up to allow anonymous read but
> authenticated write, the http-backend manual suggests
> catching only the "/git-receive-pack" POST of the packfile,
> not the initial "info/refs?service=git-receive-pack" GET in
> which we advertise refs.
>
> This does work and is secure, as we do not allow any write
> during the info/refs request, and the information in the ref
> advertisement is the same that you would get from a fetch.
>
> However, the configuration required by the server is
> slightly more complex. The default `http.receivepack`
> setting is to allow pushes if the webserver tells us that
> the user authenticated, and otherwise to return a 403
> ("Forbidden"). That works fine if authentication is turned
> on completely; the initial request requires authentication,
> and http-backend realizes it is OK to do a push.
>
> But for this "half-auth" state, no authentication has
> occurred during the initial ref advertisement. The
> http-backend CGI therefore does not think that pushing
> should be enabled, and responds with a 403. The client
> cannot continue, even though the server would have allowed
> it to run if it had provided credentials.
>
> It would be much better if the server responded with a 401,
> asking for credentials during the initial contact. But
> git-http-backend does not know about the server's auth
> configuration (so a 401 would be confusing in the case of a
> true anonymous server). Unfortunately, configuring Apache to
> recognize the query string and apply the auth appropriately
> to receive-pack (but not upload-pack) initial requests is
> non-trivial.
>
> The site admin can work around this by just turning on
> http.receivepack explicitly in its repositories. Let's
> document this workaround.
>
> Signed-off-by: Jeff King <peff@peff.net>
> ---
> My understanding is that you can do query-string matching through a
> clever use of mod-rewrite. I am not nearly clever nor interested in
> Apache enough to figure it out, but if somebody does, it would be nice
> to put the recipe here.
>
>  Documentation/git-http-backend.txt | 9 +++++++++
>  1 file changed, 9 insertions(+)
>
> diff --git a/Documentation/git-http-backend.txt b/Documentation/git-http-backend.txt
> index 7b1e85c..f43980f 100644
> --- a/Documentation/git-http-backend.txt
> +++ b/Documentation/git-http-backend.txt
> @@ -91,6 +91,15 @@ require authorization with a LocationMatch directive:
>  </LocationMatch>
>  ----------------------------------------------------------------
>  +
> +In this mode, the server will not request authentication until the
> +client actually starts the object negotiation phase of the push, rather
> +than during the initial contact.  For this reason, you must also enable
> +the `http.receivepack` config option in any repositories that should
> +accept a push. The default behavior, if `http.receivepack` is not set,
> +is to reject any pushes by unauthenticated users; the initial request
> +will therefore report `403 Forbidden` to the client, without even giving
> +an opportunity for authentication.
> ++
>  To require authentication for both reads and writes, use a Location
>  directive around the repository, or one of its parent directories:
>  +
> --
> 1.8.2.rc0.33.gd915649
>