Subject: Re: [PATCH v3] gitweb: redacted e-mail addresses feature.

From: Ævar Arnfjörð Bjarmason <[email-masked]>
Date: Sun, 21 Mar 2021 19:26:08 +0100

On Sun, Mar 21 2021, Georgios Kontaxis via GitGitGadget wrote:

> From: Georgios Kontaxis <[email-masked]>
>
> Gitweb extracts content from the Git log and makes it accessible
> over HTTP. As a result, e-mail addresses found in commits are
> exposed to web crawlers and they may not respect robots.txt.
> This may result in unsolicited messages.
> This is a feature for redacting e-mail addresses
> from the generated HTML, etc. content.
>
> This feature does not prevent someone from downloading the
> unredacted commit log, e.g., by cloning the repository, and
> extracting information from it.
> It aims to hinder the low-effort bulk collection of e-mail
> addresses by web crawlers.
>
> Changes since v1:
> - Turned off the feature by default.
> - Removed duplicate code.
> - Added note about Gitweb consumers receiving redacted logs.
>
> Changes since v2:
> - The feature can be set on a per-project basis. ('override' => 1)
>
> Signed-off-by: Georgios Kontaxis <[email-masked]>
> ---
>     gitweb: Redacted e-mail addresses feature.
>     
>     Gitweb extracts content from the Git log and makes it accessible over
>     HTTP. As a result, e-mail addresses found in commits are exposed to web
>     crawlers. This may result in unsolicited messages. This is a feature for
>     redacting e-mail addresses from the generated HTML content.
>     
>     This feature does not prevent someone from downloading the unredacted
>     commit log and extracting information from it. It aims to hinder the
>     low-effort bulk collection of e-mail addresses by web crawlers.
>     
>     Signed-off-by: Georgios Kontaxis [email-masked]
>
> Published-As: https://github.com/gitgitgadget/git/releases/tag/pr-910%2Fkontaxis%2Fkontaxis%2Femail_privacy-v3
> Fetch-It-Via: git fetch https://github.com/gitgitgadget/git pr-910/kontaxis/kontaxis/email_privacy-v3
> Pull-Request: https://github.com/gitgitgadget/git/pull/910
>
> Range-diff vs v2:
>
>  1:  74af11ca8bf2 ! 1:  930cdefe7ee0 gitweb: redacted e-mail addresses feature.
>      @@ Commit message
>           - Removed duplicate code.
>           - Added note about Gitweb consumers receiving redacted logs.
>       
>      +    Changes since v2:
>      +    - The feature can be set on a per-project basis. ('override' => 1)
>      +
>           Signed-off-by: Georgios Kontaxis <[email-masked]>
>       
>        ## Documentation/gitweb.conf.txt ##
>      @@ gitweb/gitweb.perl: sub evaluate_uri {
>       +	# $feature{'email_privacy'}{'default'} = [1];
>       +	'email_privacy' => {
>       +		'sub' => sub { feature_bool('email_privacy', @_) },
>      -+		'override' => 0,
>      ++		'override' => 1,
>       +		'default' => [0]},
>        );
>        
>
>
>  Documentation/gitweb.conf.txt | 16 +++++++++++++
>  gitweb/gitweb.perl            | 42 ++++++++++++++++++++++++++++++++---
>  2 files changed, 55 insertions(+), 3 deletions(-)
>
> diff --git a/Documentation/gitweb.conf.txt b/Documentation/gitweb.conf.txt
> index 7963a79ba98b..b7af3240177d 100644
> --- a/Documentation/gitweb.conf.txt
> +++ b/Documentation/gitweb.conf.txt
> @@ -896,6 +896,22 @@ same as of the snippet above:
>  It is an error to specify a ref that does not pass "git check-ref-format"
>  scrutiny. Duplicated values are filtered.
>  
> +email_privacy::
> +    Redact e-mail addresses from the generated HTML, etc. content.
> +    This hides e-mail addresses found in the commit log from web crawlers.
> +    Disabled by default.
> ++
> +It is highly recommended to enable this feature unless web crawlers are
> +hindered in some other way. Note that crawlers intent on harvesting e-mail
> +addresses may disregard robots.txt. You can enable this feature like so:
> ++
> +---------------------------------------------------------------------------
> +$feature{'email_privacy'}{'default'} = [1];
> +---------------------------------------------------------------------------
> ++
> +Note that if Gitweb is not the final step in a workflow then subsequent
> +steps may misbehave because of the redacted information they receive.
> +
>  
>  EXAMPLES
>  --------
> diff --git a/gitweb/gitweb.perl b/gitweb/gitweb.perl
> index 0959a782eccb..174cc566d97d 100755
> --- a/gitweb/gitweb.perl
> +++ b/gitweb/gitweb.perl
> @@ -569,6 +569,15 @@ sub evaluate_uri {
>  		'sub' => \&feature_extra_branch_refs,
>  		'override' => 0,
>  		'default' => []},
> +
> +	# Redact e-mail addresses.
> +
> +	# To enable system wide have in $GITWEB_CONFIG
> +	# $feature{'email_privacy'}{'default'} = [1];
> +	'email_privacy' => {
> +		'sub' => sub { feature_bool('email_privacy', @_) },
> +		'override' => 1,
> +		'default' => [0]},
>  );
>  
>  sub gitweb_get_feature {
> @@ -3449,6 +3458,19 @@ sub parse_date {
>  	return %date;
>  }
>  
> [snip]

So in the v1 feedback I suggested:

BEGIN QUOTE
    sub maybe_hide_email {
        my $email = shift;
        return $email unless gitweb_check_feature('email_privacy');
        return hide_email($email);
    }

then:

    $tag{author_email} = maybe_hide_email($2);
END QUOTE

But:

>  sub parse_tag {
>  	my $tag_id = shift;
>  	my %tag;
> @@ -3471,6 +3493,10 @@ sub parse_tag {
>  			if ($tag{'author'} =~ m/^([^<]+) <([^>]*)>/) {
>  				$tag{'author_name'}  = $1;
>  				$tag{'author_email'} = $2;
> +				if (gitweb_check_feature('email_privacy')) {
> +					$tag{'author_email'} = "private";
> +					$tag{'author'} = hide_mailaddr($tag{'author'});
> +				}

This code seems quite awkward, we've already done the regex match, but
this code:

> [snip]
> +sub hide_mailaddr_if_private {
> +	my $line = shift;
> +	return $line unless (gitweb_check_feature('email_privacy') &&
> +						$line =~ m/^([^<]+) <([^>]*)>/);
> +	return hide_mailaddr($line)
> +}
> +
> +sub hide_mailaddr {
> +	my $mailaddr = shift;
> +	$mailaddr =~ s/<([^>]*)>/<private>/;
> +	return $mailaddr;
> +}

Is going to do it again incrementally, and then just act on a
search-replacement if we've got the feature enabled.

It seems much simpler to just turn your:

> +				if (gitweb_check_feature('email_privacy')) {
> +					$tag{'author_email'} = "private";
> +					$tag{'author'} = hide_mailaddr($tag{'author'});
> +				}

Into:

    $tag{'author'} = maybe_hide_mailaddr($tag{author}, \$tag{author_email});

Using:

    sub maybe_hide_email {
        my ($email, $ref) = shift;
        return $email unless gitweb_check_feature('email_privacy');
        $$ref = "private" if $ref;
        return hide_email($email);
    }

Which also works for the case where you don't have a "private" hash key
to assign to. But maybe it overcomplicates things...

>  			} else {
>  				$tag{'author_name'} = $tag{'author'};
>  			}
> @@ -3519,6 +3545,10 @@ sub parse_commit_text {
>  			if ($co{'author'} =~ m/^([^<]+) <([^>]*)>/) {
>  				$co{'author_name'}  = $1;
>  				$co{'author_email'} = $2;
> +				if (gitweb_check_feature('email_privacy')) {
> +					$co{'author_email'} = "private";
> +					$co{'author'} = hide_mailaddr($co{'author'});
> +				}
>  			} else {
>  				$co{'author_name'} = $co{'author'};
>  			}
> @@ -3529,6 +3559,10 @@ sub parse_commit_text {
>  			if ($co{'committer'} =~ m/^([^<]+) <([^>]*)>/) {
>  				$co{'committer_name'}  = $1;
>  				$co{'committer_email'} = $2;
> +				if (gitweb_check_feature('email_privacy')) {
> +					$co{'committer_email'} = "private";
> +					$co{'committer'} = hide_mailaddr($co{'committer'});
> +				}
> [...]
>  			} else {
>  				$co{'committer_name'} = $co{'committer'};
>  			}
> @@ -3568,9 +3602,10 @@ sub parse_commit_text {
>  	if (! defined $co{'title'} || $co{'title'} eq "") {
>  		$co{'title'} = $co{'title_short'} = '(no commit message)';
>  	}
> -	# remove added spaces
> +	# remove added spaces, redact e-mail addresses if applicable.
>  	foreach my $line (@commit_lines) {
>  		$line =~ s/^    //;
> +		$line = hide_mailaddr_if_private($line);
>  	}
>  	$co{'comment'} = \@commit_lines;
>  
> @@ -8060,8 +8095,9 @@ sub git_commitdiff {
>  		close $fd
>  			or print "Reading git-diff-tree failed\n";
>  	} elsif ($format eq 'patch') {
> -		local $/ = undef;
> -		print <$fd>;
> +		while (my $line = <$fd>) {
> +			print hide_mailaddr_if_private($line);
> +		}

Urm, have you tested this? How does a while loop over a <$fd> make sense
when $/ is undef, the readline() operator will always return just one
record, so having a while loop doesn't make sense.

I'm not sure of the input here, but given that if you're expecting to
replace all e-mail addresses on all lines with this function that's not
how it'll work, the s/// doesn't have a /g, so it'll stop at the first
replacement.

>  		close $fd
>  			or print "Reading git-format-patch failed\n";
>  	}
>
> base-commit: a5828ae6b52137b913b978e16cd2334482eb4c1f