Re: [PATCH v7 4/4] transport: add from_user parameter to is_transport_allowed

[Jeff King <peff@peff.net>]

On Thu, Dec 01, 2016 at 12:25:59PM -0800, Brandon Williams wrote:

> Add the from_user parameter to the 'is_transport_allowed' function.
> This allows callers to query if a transport protocol is allowed, given
> that the caller knows that the protocol is coming from the user (1) or
> not from the user (0), such as redirects in libcurl.  If unknown, a -1
> should be provided which falls back to reading `GIT_PROTOCOL_FROM_USER`
> to determine if the protocol came from the user.

Patches 3 and 4 look good to me (1 and 2 are unchanged, right? They are
already in 'next' anyway, though I guess we are due for a post-release
reset of 'next').

> diff --git a/http.c b/http.c
> index fee128b..e74c0f0 100644
> --- a/http.c
> +++ b/http.c
> @@ -725,13 +725,13 @@ static CURL *get_curl_handle(void)
>  	curl_easy_setopt(result, CURLOPT_POST301, 1);
>  #endif
>  #if LIBCURL_VERSION_NUM >= 0x071304
> -	if (is_transport_allowed("http"))
> +	if (is_transport_allowed("http", 0))
>  		allowed_protocols |= CURLPROTO_HTTP;
> -	if (is_transport_allowed("https"))
> +	if (is_transport_allowed("https", 0))
>  		allowed_protocols |= CURLPROTO_HTTPS;
> -	if (is_transport_allowed("ftp"))
> +	if (is_transport_allowed("ftp", 0))
>  		allowed_protocols |= CURLPROTO_FTP;
> -	if (is_transport_allowed("ftps"))
> +	if (is_transport_allowed("ftps", 0))
>  		allowed_protocols |= CURLPROTO_FTPS;
>  	curl_easy_setopt(result, CURLOPT_REDIR_PROTOCOLS, allowed_protocols);
>  #else

This is better, but I think we still need to deal with http-alternates
on top.

I think we'd need to move this allowed_protocols setup into a function
like:

  int generate_allowed_protocols(int from_user)
  {
	int ret;
	if (is_transport_allowed("http", from_user))
		ret |= CURLPROTO_HTTP;
	... etc ...
	return ret;
  }

and then create a protocol list for each situation:

  allowed_protocols = generate_allowed_protocols(-1);
  allowed_redir_protocols = generate_allowed_protocols(0);

and then we know we can always set up the redir protocols:

  curl_easy_setopt(result, CURLOPT_REDIR_PROTOCOLS, allowed_redir_protocols);

and which we feed for CURLOPT_PROTOCOLS depends on whether we are
following an http-alternates redirect or not. But I suspect it will be a
nasty change to plumb through the idea of "this request is on behalf of
an http-alternates redirect".

Given how few people probably care, I'm tempted to document it as a
quirk and direct people to the upcoming http.followRedirects. The newly
proposed default value of that disables http-alternates entirely anyway.

-Peff