[PATCH] gitweb: highlight: strip non-printable characters via col(1)

From: "Christopher M. Fuhrman" <redacted>

The current code, as is, passes control characters, such as form-feed
(^L) to highlight which then passes it through to the browser.  This
will cause the browser to display one of the following warnings:

Safari v5.1 (6534.50) & Google Chrome v13.0.782.112:

  This page contains the following errors:

  error on line 657 at column 38: PCDATA invalid Char value 12
  Below is a rendering of the page up to the first error.

Mozilla Firefox 3.6.19 & Mozilla Firefox 5.0:

   XML Parsing Error: not well-formed
   Location:
   http://path/to/git/repo/blah/blah

Both errors were generated by gitweb.perl v1.7.3.4 w/ highlight 2.7
using arch/ia64/kernel/unwind.c from the Linux kernel.

Strip non-printable control-characters by piping the output produced
by git-cat-file(1) to col(1) as follows:

  git cat-file blob deadbeef314159 | col -bx | highlight <args>

Note usage of the '-x' option which tells col(1) to output multiple
spaces instead of tabs.

Tested under OpenSuSE 11.4 & NetBSD 5.1 using perl 5.12.3 and perl
5.12.2 respectively using Safari, Firefox, and Google Chrome.

Signed-off-by: Christopher M. Fuhrman <redacted>
---
Howdy,

I haven't gotten any responses to my patch for a while, so I am now
submitting this for general inclusion into git.  Please note that this
is based off the "maint" branch per Documentation/SubmittingPatches

For an example of this bug in action, see:

* http://git.fuhrbear.com/~cfuhrman/?p=linux/.git;a=blob;f=arch/alpha/kernel/core_titan.c;h=219bf271c0ba2e5f2d668af707df57fbbd00ccfd;hb=HEAD
* http://git.fuhrbear.com/~cfuhrman/?p=linux/.git;a=blob;f=arch/ia64/kernel/unwind.c;h=fed6afa2e8a9014e65229e51e64fa4b1c13cc284;hb=HEAD

WRT the col(1) command, I've verified that the binary is installed in
/usr/bin on OpenSuSE, NetBSD, OpenBSD, Solaris 10, and AIX.  This
patch assumes that /usr/bin is in $PATH.

Cheers!

 gitweb/gitweb.perl |    1 +
 1 files changed, 1 insertions(+), 0 deletions(-)

diff --git a/gitweb/gitweb.perl b/gitweb/gitweb.perl
index 50a835a..4c68165 100755
--- a/gitweb/gitweb.perl
+++ b/gitweb/gitweb.perl

@@ -3656,6 +3656,7 @@ sub run_highlighter {
 
 	close $fd;
 	open $fd, quote_command(git_cmd(), "cat-file", "blob", $hash)." | ".
+	          "col -bx | ".
 	          quote_command($highlight_bin).
 	          " --replace-tabs=8 --fragment --syntax $syntax |"
 		or die_error(500, "Couldn't open file or run syntax highlighter");

-- 
1.7.5.4

On Tue, 23 Aug 2011, Christopher M. Fuhrman wrote:

The current code, as is, passes control characters, such as form-feed
(^L) to highlight which then passes it through to the browser.  This
will cause the browser to display one of the following warnings:

Safari v5.1 (6534.50) & Google Chrome v13.0.782.112:

  This page contains the following errors:

  error on line 657 at column 38: PCDATA invalid Char value 12
  Below is a rendering of the page up to the first error.

Mozilla Firefox 3.6.19 & Mozilla Firefox 5.0:

   XML Parsing Error: not well-formed
   Location:
   http://path/to/git/repo/blah/blah

Both errors were generated by gitweb.perl v1.7.3.4 w/ highlight 2.7
using arch/ia64/kernel/unwind.c from the Linux kernel.

Strip non-printable control-characters by piping the output produced
by git-cat-file(1) to col(1) as follows:

  git cat-file blob deadbeef314159 | col -bx | highlight <args>

Note usage of the '-x' option which tells col(1) to output multiple
spaces instead of tabs.

Why use external program (which ming be not installed, or might not
strip control-characters), instead of making gitweb sanitize highlighter
output itself.  Something like the patch below (which additionally
shows where there are control characters):

-- >8 --

diff --git i/gitweb/gitweb.perl w/gitweb/gitweb.perl
index 7cf12af..192db2c 100755
--- i/gitweb/gitweb.perl
+++ w/gitweb/gitweb.perl

@@ -1517,6 +1517,17 @@ sub esc_path {
 	return $str;
 }
 
+# Sanitize for use in XHTML + application/xml+xhtml
+sub sanitize {
+	my $str = shift;
+
+	return undef unless defined $str;
+
+	$str = to_utf8($str);
+	$str =~ s|([[:cntrl:]])|quot_cec($1)|eg;
+	return $str;
+}
+
 # Make control characters "printable", using character escape codes (CEC)
 sub quot_cec {
 	my $cntrl = shift;

@@ -6546,7 +6557,8 @@ sub git_blob {
 			$nr++;
 			$line = untabify($line);
 			printf qq!<div class="pre"><a id="l%i" href="%s#l%i" class="linenr">%4i</a> %s</div>\n!,
-			       $nr, esc_attr(href(-replay => 1)), $nr, $nr, $syntax ? to_utf8($line) : esc_html($line, -nbsp=>1);
+			       $nr, esc_attr(href(-replay => 1)), $nr, $nr,
+			       $syntax ? sanitize($line) : esc_html($line, -nbsp=>1);
 		}
 	}
 	close $fd

-- 8< --

-- 
Jakub Narebski
Poland