[Security] gitweb local privilege escalation (fix)

[Junio C Hamano]

Current gitweb has a possible local privilege escalation bug that allows a
malicious repository owner to run a command of his choice by specifying
diff.external configuration variable in his repository and running a
crafted gitweb query.

Recent (post 1.4.3) gitweb itself never generates a link that would result
in such a query, and the safest and cleanest fix to this issue is to
simply drop the support for it.  Maintenance release v1.6.0.6, v1.5.6.6,
v1.5.5.6 and v1.5.4.7 are already available at k.org (see the announcement
for v1.6.0.6 I sent out a few minutes ago), and the master branch and
others pushed out tonight have the same fix.

This message contains two patches (credits go to Matt McCutchen, Jeff King
and Jakub Narebski) to do the fix yourself:

 (1) for Git 1.5.4.X, 1.5.5.X, and 1.5.6.X, and

 (2) for Git 1.6.0.X.

Distro packagers and people on the vendor security list have been notified
about this fix earlier this week; people running gitweb from vendor
supplied binaries should be able to get updates from them as well.

>From dfff4b7aa42de7e7d58caeebe2c6128449f09b76 Mon Sep 17 00:00:00 2001
From: Junio C Hamano <gitster@xxxxxxxxx>
Date: Tue, 16 Dec 2008 19:42:02 -0800
Subject: [PATCH] gitweb: do not run "git diff" that is Porcelain

Jakub says that legacy-style URI to view two blob differences are never
generated since 1.4.3.  This codepath runs "git diff" Porcelain from the
gitweb, which is a no-no.  It can trigger diff.external command that is
specified in the configuration file of the repository being viewed.

This patch applies to v1.5.4 and later.

Signed-off-by: Junio C Hamano <gitster@xxxxxxxxx>
---
 gitweb/gitweb.perl |   38 ++------------------------------------
 1 files changed, 2 insertions(+), 36 deletions(-)

diff --git a/gitweb/gitweb.perl b/gitweb/gitweb.perl
index b582332..86a6ced 100755
--- a/gitweb/gitweb.perl
+++ b/gitweb/gitweb.perl
@@ -4809,43 +4809,9 @@ sub git_blobdiff {
 			or die_error(undef, "Open git-diff-tree failed");
 	}
 
-	# old/legacy style URI
-	if (!%diffinfo && # if new style URI failed
-	    defined $hash && defined $hash_parent) {
-		# fake git-diff-tree raw output
-		$diffinfo{'from_mode'} = $diffinfo{'to_mode'} = "blob";
-		$diffinfo{'from_id'} = $hash_parent;
-		$diffinfo{'to_id'}   = $hash;
-		if (defined $file_name) {
-			if (defined $file_parent) {
-				$diffinfo{'status'} = '2';
-				$diffinfo{'from_file'} = $file_parent;
-				$diffinfo{'to_file'}   = $file_name;
-			} else { # assume not renamed
-				$diffinfo{'status'} = '1';
-				$diffinfo{'from_file'} = $file_name;
-				$diffinfo{'to_file'}   = $file_name;
-			}
-		} else { # no filename given
-			$diffinfo{'status'} = '2';
-			$diffinfo{'from_file'} = $hash_parent;
-			$diffinfo{'to_file'}   = $hash;
-		}
-
-		# non-textual hash id's can be cached
-		if ($hash =~ m/^[0-9a-fA-F]{40}$/ &&
-		    $hash_parent =~ m/^[0-9a-fA-F]{40}$/) {
-			$expires = '+1d';
-		}
-
-		# open patch output
-		open $fd, "-|", git_cmd(), "diff", @diff_opts,
-			'-p', ($format eq 'html' ? "--full-index" : ()),
-			$hash_parent, $hash, "--"
-			or die_error(undef, "Open git-diff failed");
-	} else  {
+	# old/legacy style URI -- not generated anymore since 1.4.3.
+	if (!%diffinfo) {
 		die_error('404 Not Found', "Missing one of the blob diff parameters")
-			unless %diffinfo;
 	}
 
 	# header
-- 
1.6.1.rc3.19.g66a9

diff --git a/gitweb/gitweb.perl b/gitweb/gitweb.perl
index ced7bb7..804670c 100755
--- a/gitweb/gitweb.perl
+++ b/gitweb/gitweb.perl
@@ -4863,43 +4863,9 @@ sub git_blobdiff {
 			or die_error(500, "Open git-diff-tree failed");
 	}
 
-	# old/legacy style URI
-	if (!%diffinfo && # if new style URI failed
-	    defined $hash && defined $hash_parent) {
-		# fake git-diff-tree raw output
-		$diffinfo{'from_mode'} = $diffinfo{'to_mode'} = "blob";
-		$diffinfo{'from_id'} = $hash_parent;
-		$diffinfo{'to_id'}   = $hash;
-		if (defined $file_name) {
-			if (defined $file_parent) {
-				$diffinfo{'status'} = '2';
-				$diffinfo{'from_file'} = $file_parent;
-				$diffinfo{'to_file'}   = $file_name;
-			} else { # assume not renamed
-				$diffinfo{'status'} = '1';
-				$diffinfo{'from_file'} = $file_name;
-				$diffinfo{'to_file'}   = $file_name;
-			}
-		} else { # no filename given
-			$diffinfo{'status'} = '2';
-			$diffinfo{'from_file'} = $hash_parent;
-			$diffinfo{'to_file'}   = $hash;
-		}
-
-		# non-textual hash id's can be cached
-		if ($hash =~ m/^[0-9a-fA-F]{40}$/ &&
-		    $hash_parent =~ m/^[0-9a-fA-F]{40}$/) {
-			$expires = '+1d';
-		}
-
-		# open patch output
-		open $fd, "-|", git_cmd(), "diff", @diff_opts,
-			'-p', ($format eq 'html' ? "--full-index" : ()),
-			$hash_parent, $hash, "--"
-			or die_error(500, "Open git-diff failed");
-	} else  {
-		die_error(400, "Missing one of the blob diff parameters")
-			unless %diffinfo;
+	# old/legacy style URI -- not generated anymore since 1.4.3.
+	if (!%diffinfo) {
+		die_error('404 Not Found', "Missing one of the blob diff parameters")
 	}
 
 	# header