Problem in gitweb.cgi

Hi,

I have recently run into a problem with gitweb that was triggered by my distribution, OpenSUSE Tumbleweed. Due to a misconfiguration of the application AppArmour, "git instaweb" was having problems in accessing the configuration file "/etc/gitweb-common.conf". That was half of the problem and has been reported downstream here: https://bugzilla.suse.com/show_bug.cgi?id=1218664

The other half of the problem is in gitweb.cgi itself. There is a logic to select which configuration file is going to be used. That logic is ok, although a bit unclear from the documentation. Reading the code I understood that $GITWEB_CONFIG_COMMON (usually /etc/gitweb-common.conf) should always be read if it exists, and $GITWEB_CONFIG_SYSTEM (usually /etc/gitweb.conf) will never be read if $GITWEB_CONFIG has been read before.

The problem is that $GITWEB_CONFIG_COMMON was never read, even though the code that reads it was being called before the code that reads the other two files. As I said before, the problem was caused by a lack of permission in AppArmour, but gitweb should have been able to catch the error. By not signaling it properly, users get lost because the problem is a little tricky to debug.

After some "printf" debugging, I converged to this routine, line 728 of gitweb.cgi:

# read and parse gitweb config file given by its parameter.
# returns true on success, false on recoverable error, allowing
# to chain this subroutine, using first file that exists.
# dies on errors during parsing config file, as it is unrecoverable.
sub read_config_file {
        my $filename = shift;
        return unless defined $filename;
        # die if there are errors parsing config file
        if (-e $filename) {
                do $filename;
                die $@ if $@;
                return 1;
        }
        return;
}

Perl uses two different variables to manage errors from a "do". One is "$@", which is set in this case when do is unable to compile the file. The other is $!, which is set in case "do" cannot read the file. By printing the value of $! I found out that it was set to "Permission denied". Since the script does not currently test for $!, the error goes unnoticed.

I suppose a proper fix would be to put a line before the test for $@, like "die $! if $!".

For the curious, I have a report explaining the full problem here, but the part relevant to gitweb is in this e-mail: https://stackoverflow.com/questions/77789216/problem-with-git-instaweb-on-opensuse-tumbleweed-etc-gitweb-common-conf-is-n

Best regards, Marcelo.