cvsserver: Make req_Root more critical of its input data

The path submitted with the Root request has to be absolute
(cvs does it this way and it may save us some sanity checks
later)

If multiple roots are specified (e.g. because we use
pserver authentication which will already include the
root), ensure that they say all the same.

Probably neither is a security risk, and neither should ever
be triggered by a sane client, but when validating
input data, it's better to be save than sorry.
Signed-off-by: NFrank Lichtenheld <frank@lichtenheld.de>
Signed-off-by: NJunio C Hamano <gitster@pobox.com>

git-cvsserver.perl

@@ -167,6 +167,17 @@ sub req_Root
     my ( $cmd, $data ) = @_;
     $log->debug("req_Root : $data");
 
+    unless ($data =~ m#^/#) {
+	print "error 1 Root must be an absolute pathname\n";
+	return 0;
+    }
+
+    if ($state->{CVSROOT}
+	&& ($state->{CVSROOT} ne $data)) {
+	print "error 1 Conflicting roots specified\n";
+	return 0;
+    }
+
     $state->{CVSROOT} = $data;
 
     $ENV{GIT_DIR} = $state->{CVSROOT} . "/";

t/t9400-git-cvsserver-server.sh

@@ -110,6 +110,40 @@ test_expect_success 'pserver authentication failure (login/non-anonymous user)'
    tail -n1 log | grep -q "^I HATE YOU$"'
 
 
+# misuse pserver authentication for testing of req_Root
+
+cat >request-relative  <<EOF
+BEGIN AUTH REQUEST
+gitcvs.git
+anonymous
+
+END AUTH REQUEST
+EOF
+
+cat >request-conflict  <<EOF
+BEGIN AUTH REQUEST
+$SERVERDIR
+anonymous
+
+END AUTH REQUEST
+Root $WORKDIR
+EOF
+
+test_expect_success 'req_Root failure (relative pathname)' \
+  'if cat request-relative | git-cvsserver pserver >log 2>&1
+   then
+       echo unexpected success
+       false
+   else
+       true
+   fi &&
+   tail log | grep -q "^error 1 Root must be an absolute pathname$"'
+
+test_expect_success 'req_Root failure (conflicting roots)' \
+  'cat request-conflict | git-cvsserver pserver >log 2>&1 &&
+   tail log | grep -q "^error 1 Conflicting roots specified$"'
+
+
 #--------------
 # CONFIG TESTS
 #--------------