Re: [PATCH 2/2] http: use credential API to handle proxy authentication

> Currently, the only way to pass proxy credentials to curl is by including them
> in the proxy URL. Usually, this means they will end up on disk unencrypted, one
> way or another (by inclusion in ~/.gitconfig, shell profile or history). Since
> proxy authentication often uses a domain user, credentials can be security
> sensitive; therefore, a safer way of passing credentials is desirable.
>
> If the configured proxy contains a username but not a password, query the
> credential API for one. Also, make sure we approve/reject proxy credentials
> properly.
>
> For consistency reasons, add parsing of http_proxy/https_proxy/all_proxy
> environment variables, which would otherwise be evaluated as a fallback by curl.
> Without this, we would have different semantics for git configuration and
> environment variables.
>
> Signed-off-by: Knut Franke <k.franke@science-computing.de>
> Helped-by: Junio C Hamano <gitster@pobox.com>
> Helped-by: Eric Sunshine <sunshine@sunshineco.com>
> ---
> diff --git a/Documentation/config.txt b/Documentation/config.txt
> @@ -1593,9 +1593,13 @@ help.htmlPath::
>
>  http.proxy::
>         Override the HTTP proxy, normally configured using the 'http_proxy',
> -       'https_proxy', and 'all_proxy' environment variables (see
> -       `curl(1)`).  This can be overridden on a per-remote basis; see
> -       remote.<name>.proxy
> +       'https_proxy', and 'all_proxy' environment variables (see `curl(1)`). In
> +       addition to the syntax understood by curl, it is possible to specify a
> +       proxy string with a user name but no password, in which case git will
> +       attempt to acquire one in the same way it does for other credentials. See
> +       linkgit:gitcredentials[7] for more information. The syntax thus is
> +       '[protocol://][user[:password]@]proxyhost[:port]'. This can be overridden
> +       on a per-remote basis; see remote.<name>.proxy

>  http.proxyAuthMethod::
>         Set the method with which to authenticate against the HTTP proxy. This
> diff --git a/http.c b/http.c
> @@ -337,6 +342,24 @@ static void var_override(const char **var, char *value)
>
>  static void init_curl_proxy_auth(CURL *result)
>  {
> +       if (proxy_auth.username) {
> +               struct strbuf s = STRBUF_INIT;
> +               if (!proxy_auth.password)
> +                       credential_fill(&proxy_auth);
> +#if LIBCURL_VERSION_NUM >= 0x071301
> +               curl_easy_setopt(result, CURLOPT_PROXYUSERNAME,
> +                       proxy_auth.username);
> +               curl_easy_setopt(result, CURLOPT_PROXYPASSWORD,
> +                       proxy_auth.password);

> +#else
> +               strbuf_addstr_urlencode(&s, proxy_auth.username, 1);
> +               strbuf_addch(&s, ':');
> +               strbuf_addstr_urlencode(&s, proxy_auth.password, 1);
> +               curl_proxyuserpwd = strbuf_detach(&s, NULL);
> +               curl_easy_setopt(result, CURLOPT_PROXYUSERPWD, curl_proxyuserpwd);

> +#endif
> +       }
> +
>         var_override(&http_proxy_authmethod, getenv("GIT_HTTP_PROXY_AUTHMETHOD"));
>
>  #if LIBCURL_VERSION_NUM >= 0x070a07 /* CURLOPT_PROXYAUTH and CURLAUTH_ANY */