cvsserver: anonymous cvs via pserver support

git-cvsserver now knows how to do the pserver auth chat when the user
is anonymous. To get it to work, add a line to your inetd.conf like

  cvspserver stream tcp nowait nobody git-cvsserver pserver

(On some inetd implementations you may have to put the pserver parameter twice.)

Commits are blocked. Naively, git-cvsserver assumes non-malicious users. Please
review the code before setting this up on an internet-accessible server.

NOTE: the <nobody> user above will need write access to the .git directory
to maintain the sqlite database. Updating of the sqlite database should be
put in an update hook to avoid this problem, so that it is maintained by
users with write access.

git-cvsserver.perl

@@ -87,6 +87,31 @@ $log->info("--------------- STARTING -----------------");
 my $TEMP_DIR = tempdir( CLEANUP => 1 );
 $log->debug("Temporary directory is '$TEMP_DIR'");
 
+# if we are called with a pserver argument,
+# deal with the authentication cat before entereing the
+# main loop
+if (@ARGV && $ARGV[0] eq 'pserver') {
+    my $line = <STDIN>; chomp $line;
+    unless( $line eq 'BEGIN AUTH REQUEST') {
+       die "E Do not understand $line - expecting BEGIN AUTH REQUEST\n";
+    }
+    $line = <STDIN>; chomp $line;
+    req_Root('root', $line) # reuse Root
+       or die "E Invalid root $line \n";
+    $line = <STDIN>; chomp $line;
+    unless ($line eq 'anonymous') {
+       print "E Only anonymous user allowed via pserver\n";
+       print "I HATE YOU\n";
+    }
+    $line = <STDIN>; chomp $line;    # validate the password?
+    $line = <STDIN>; chomp $line;
+    unless ($line eq 'END AUTH REQUEST') {
+       die "E Do not understand $line -- expecting END AUTH REQUEST\n";
+    }
+    print "I LOVE YOU\n";
+    # and now back to our regular programme...
+}
+
 # Keep going until the client closes the connection
 while (<STDIN>)
 {
@@ -165,6 +190,7 @@ sub req_Root
         print "E the repo config file needs a [gitcvs] section added, and the parameter 'enabled' set to 1\n";
         print "E \n";
         print "error 1 GITCVS emulation disabled\n";
+        return 0;
     }
 
     if ( defined ( $cfg->{gitcvs}{logfile} ) )
@@ -173,6 +199,8 @@ sub req_Root
     } else {
         $log->nofile();
     }
+
+    return 1;
 }
 
 # Global_option option \n
@@ -914,6 +942,12 @@ sub req_ci
 
     $log->info("req_ci : " . ( defined($data) ? $data : "[NULL]" ));
 
+    if ( @ARGV && $ARGV[0] eq 'pserver')
+    {
+        print "error 1 pserver access cannot commit\n";
+        exit;
+    }
+
     if ( -e $state->{CVSROOT} . "/index" )
     {
         print "error 1 Index already exists in git repo\n";