Re: [PATCH 1/3] transport_anonymize_url(): support retaining username

[Johannes Schindelin <Johannes.Schindelin@gmx.de>]

Hi Peff,

On Sun, 19 May 2019, Jeff King wrote:

> When we anonymize URLs to show in messages, we strip out both the
> username and password (if any). But there are also contexts where we
> should strip out the password (to avoid leaking it) but retain the
> username.
>
> Let's generalize transport_anonymize_url() to support both cases. We'll
> give it a new name since the password-only mode isn't really
> "anonymizing", but keep the old name as a synonym to avoid disrupting
> existing callers.
>
> Note that there are actually three places we parse URLs, and this
> functionality _could_ go into any of them:
>
>   - transport_anonymize_url(), which we modify here
>
>   - the urlmatch.c code parses a URL into its constituent parts, from
>     which we could easily remove the elements we want to drop and
>     re-format it as a single URL. But its parsing also normalizes
>     elements (e.g., downcasing hostnames).  This isn't wrong, but it's
>     more friendly if we can leave the rest of the URL untouched.

I have not looked into it at all, but I seem to vaguely remember that the
result of this code might be used to look up `url.<url>.insteadOf`
settings, where the middle part *is* case-sensitive.

>   - credential_form_url() parses a URL and decodes the specific
>     elements, but it's hard to convert it back into a regular URL. It
>     treats "host:port" as a single unit, meaning it needs to be
>     re-encoded specially (since a colon would otherwise end
>     percent-encoded).
>
> Since transport_anonymize_url() seemed closest to what we want here, I
> used that as the base.
>
> Signed-off-by: Jeff King <peff@peff.net>
> ---
> I think it would be beneficial to unify these three cases under a single
> parser, but it seemed like too big a rabbit hole for this topic. Of the
> three, the urlmatch one seems the most mature. I think if we could
> simply separate the normalization from the parsing/decoding, the others
> could build on top of it. It might also require some careful thinking
> about how pseudo-urls like ssh "host:path" interact.

In light of what I mentioned above, I am not sure that we should go there
in the first place...

Thanks,
Dscho

> I won't call that a #leftoverbits, because it's more of a feast. :)
>
>  transport.c | 21 ++++++++++++++-------
>  transport.h | 11 ++++++++++-
>  2 files changed, 24 insertions(+), 8 deletions(-)
>
> diff --git a/transport.c b/transport.c
> index f1fcd2c4b0..ba61e57295 100644
> --- a/transport.c
> +++ b/transport.c
> @@ -1335,11 +1335,7 @@ int transport_disconnect(struct transport *transport)
>  	return ret;
>  }
>
> -/*
> - * Strip username (and password) from a URL and return
> - * it in a newly allocated string.
> - */
> -char *transport_anonymize_url(const char *url)
> +char *transport_strip_url(const char *url, int strip_user)
>  {
>  	char *scheme_prefix, *anon_part;
>  	size_t anon_len, prefix_len = 0;
> @@ -1348,7 +1344,10 @@ char *transport_anonymize_url(const char *url)
>  	if (url_is_local_not_ssh(url) || !anon_part)
>  		goto literal_copy;
>
> -	anon_len = strlen(++anon_part);
> +	anon_len = strlen(anon_part);
> +	if (strip_user)
> +		anon_part++;
> +
>  	scheme_prefix = strstr(url, "://");
>  	if (!scheme_prefix) {
>  		if (!strchr(anon_part, ':'))
> @@ -1373,7 +1372,15 @@ char *transport_anonymize_url(const char *url)
>  		cp = strchr(scheme_prefix + 3, '/');
>  		if (cp && cp < anon_part)
>  			goto literal_copy;
> -		prefix_len = scheme_prefix - url + 3;
> +
> +		if (strip_user)
> +			prefix_len = scheme_prefix - url + 3;
> +		else {
> +			cp = strchr(scheme_prefix + 3, ':');
> +			if (cp && cp > anon_part)
> +				goto literal_copy; /* username only */
> +			prefix_len = cp - url;
> +		}
>  	}
>  	return xstrfmt("%.*s%.*s", (int)prefix_len, url,
>  		       (int)anon_len, anon_part);
> diff --git a/transport.h b/transport.h
> index 06e06d3d89..6d8c99ac91 100644
> --- a/transport.h
> +++ b/transport.h
> @@ -243,10 +243,19 @@ const struct ref *transport_get_remote_refs(struct transport *transport,
>  int transport_fetch_refs(struct transport *transport, struct ref *refs);
>  void transport_unlock_pack(struct transport *transport);
>  int transport_disconnect(struct transport *transport);
> -char *transport_anonymize_url(const char *url);
>  void transport_take_over(struct transport *transport,
>  			 struct child_process *child);
>
> +/*
> + * Strip password and optionally username from a URL and return
> + * it in a newly allocated string (even if nothing was stripped).
> + */
> +char *transport_strip_url(const char *url, int strip_username);
> +static inline char *transport_anonymize_url(const char *url)
> +{
> +	return transport_strip_url(url, 1);
> +}
> +
>  int transport_connect(struct transport *transport, const char *name,
>  		      const char *exec, int fd[2]);
>
> --
> 2.22.0.rc0.583.g23d90da2b3
>
>