Revert "Revert "mg.c, Cwd.pm - Empty path is the same as "." which is forbidden under taint""

This reverts commit 9eb153ffbbde62558146e8f9b837034f42878e13.

The patch this unreverts was accidentally pushed to blead without going
through PR or smoke process which it really needs. This patch exists so
it can go through that process.

15 files changed, 54 insertions, 16 deletions

diff --git a/dist/PathTools/Changes b/dist/PathTools/Changes
index 1e65e9c4e2..99e0fe3cfb 100644
--- a/dist/PathTools/Changes
+++ b/dist/PathTools/Changes
@@ -1,5 +1,9 @@
 Revision history for Perl distribution PathTools.
 
+3.85
+
+- Fix issue related to tainting empty PATH
+
 3.84
 
 - Add PerlIO_readlink backcompat defines to Cws.xs
diff --git a/dist/PathTools/Cwd.pm b/dist/PathTools/Cwd.pm
index 06835833e6..6fb135ce63 100644
--- a/dist/PathTools/Cwd.pm
+++ b/dist/PathTools/Cwd.pm
@@ -3,7 +3,7 @@ use strict;
 use Exporter;
 
 
-our $VERSION = '3.84';
+our $VERSION = '3.85';
 my $xs_version = $VERSION;
 $VERSION =~ tr/_//d;
 
@@ -192,8 +192,14 @@ sub _backtick_pwd {
     # Localize %ENV entries in a way that won't create new hash keys.
     # Under AmigaOS we don't want to localize as it stops perl from
     # finding 'sh' in the PATH.
-    my @localize = grep exists $ENV{$_}, qw(PATH IFS CDPATH ENV BASH_ENV) if $^O ne "amigaos";
+    my @localize = grep exists $ENV{$_}, qw(IFS CDPATH ENV BASH_ENV) if $^O ne "amigaos";
     local @ENV{@localize} if @localize;
+    # empty PATH is the same as "." on *nix, so localize it to /something/
+    # we won't *use* the path as code above turns $pwd_cmd into a specific
+    # executable, but it will blow up anyway under taint. We could set it to
+    # anything absolute. Perhaps "/" would be better.
+    local $ENV{PATH}= "/usr/bin"
+        if $^O ne "vms" and $^O ne "amigaos";
     
     my $cwd = `$pwd_cmd`;
     # Belt-and-suspenders in case someone said "undef $/".
diff --git a/dist/PathTools/lib/File/Spec.pm b/dist/PathTools/lib/File/Spec.pm
index e0a49edb83..da3c544b84 100644
--- a/dist/PathTools/lib/File/Spec.pm
+++ b/dist/PathTools/lib/File/Spec.pm
@@ -2,7 +2,7 @@ package File::Spec;
 
 use strict;
 
-our $VERSION = '3.84';
+our $VERSION = '3.85';
 $VERSION =~ tr/_//d;
 
 my %module = (
diff --git a/dist/PathTools/lib/File/Spec/AmigaOS.pm b/dist/PathTools/lib/File/Spec/AmigaOS.pm
index a29617c7bd..0bb2d261cc 100644
--- a/dist/PathTools/lib/File/Spec/AmigaOS.pm
+++ b/dist/PathTools/lib/File/Spec/AmigaOS.pm
@@ -3,7 +3,7 @@ package File::Spec::AmigaOS;
 use strict;
 require File::Spec::Unix;
 
-our $VERSION = '3.84';
+our $VERSION = '3.85';
 $VERSION =~ tr/_//d;
 
 our @ISA = qw(File::Spec::Unix);
diff --git a/dist/PathTools/lib/File/Spec/Cygwin.pm b/dist/PathTools/lib/File/Spec/Cygwin.pm
index e21c0bb550..aadc7c6009 100644
--- a/dist/PathTools/lib/File/Spec/Cygwin.pm
+++ b/dist/PathTools/lib/File/Spec/Cygwin.pm
@@ -3,7 +3,7 @@ package File::Spec::Cygwin;
 use strict;
 require File::Spec::Unix;
 
-our $VERSION = '3.84';
+our $VERSION = '3.85';
 $VERSION =~ tr/_//d;
 
 our @ISA = qw(File::Spec::Unix);
diff --git a/dist/PathTools/lib/File/Spec/Epoc.pm b/dist/PathTools/lib/File/Spec/Epoc.pm
index 2429bb2925..4b9389a0ff 100644
--- a/dist/PathTools/lib/File/Spec/Epoc.pm
+++ b/dist/PathTools/lib/File/Spec/Epoc.pm
@@ -2,7 +2,7 @@ package File::Spec::Epoc;
 
 use strict;
 
-our $VERSION = '3.84';
+our $VERSION = '3.85';
 $VERSION =~ tr/_//d;
 
 require File::Spec::Unix;
diff --git a/dist/PathTools/lib/File/Spec/Functions.pm b/dist/PathTools/lib/File/Spec/Functions.pm
index a09150cfdf..1513715a9a 100644
--- a/dist/PathTools/lib/File/Spec/Functions.pm
+++ b/dist/PathTools/lib/File/Spec/Functions.pm
@@ -3,7 +3,7 @@ package File::Spec::Functions;
 use File::Spec;
 use strict;
 
-our $VERSION = '3.84';
+our $VERSION = '3.85';
 $VERSION =~ tr/_//d;
 
 require Exporter;
diff --git a/dist/PathTools/lib/File/Spec/Mac.pm b/dist/PathTools/lib/File/Spec/Mac.pm
index 369d1f02ca..34dc67c47b 100644
--- a/dist/PathTools/lib/File/Spec/Mac.pm
+++ b/dist/PathTools/lib/File/Spec/Mac.pm
@@ -4,7 +4,7 @@ use strict;
 use Cwd ();
 require File::Spec::Unix;
 
-our $VERSION = '3.84';
+our $VERSION = '3.85';
 $VERSION =~ tr/_//d;
 
 our @ISA = qw(File::Spec::Unix);
diff --git a/dist/PathTools/lib/File/Spec/OS2.pm b/dist/PathTools/lib/File/Spec/OS2.pm
index 604e2e30e9..5fe1751149 100644
--- a/dist/PathTools/lib/File/Spec/OS2.pm
+++ b/dist/PathTools/lib/File/Spec/OS2.pm
@@ -4,7 +4,7 @@ use strict;
 use Cwd ();
 require File::Spec::Unix;
 
-our $VERSION = '3.84';
+our $VERSION = '3.85';
 $VERSION =~ tr/_//d;
 
 our @ISA = qw(File::Spec::Unix);
diff --git a/dist/PathTools/lib/File/Spec/Unix.pm b/dist/PathTools/lib/File/Spec/Unix.pm
index 52904b4857..77d5303809 100644
--- a/dist/PathTools/lib/File/Spec/Unix.pm
+++ b/dist/PathTools/lib/File/Spec/Unix.pm
@@ -3,7 +3,7 @@ package File::Spec::Unix;
 use strict;
 use Cwd ();
 
-our $VERSION = '3.84';
+our $VERSION = '3.85';
 $VERSION =~ tr/_//d;
 
 =head1 NAME
diff --git a/dist/PathTools/lib/File/Spec/VMS.pm b/dist/PathTools/lib/File/Spec/VMS.pm
index 69a39bb5ff..eadea51a99 100644
--- a/dist/PathTools/lib/File/Spec/VMS.pm
+++ b/dist/PathTools/lib/File/Spec/VMS.pm
@@ -4,7 +4,7 @@ use strict;
 use Cwd ();
 require File::Spec::Unix;
 
-our $VERSION = '3.84';
+our $VERSION = '3.85';
 $VERSION =~ tr/_//d;
 
 our @ISA = qw(File::Spec::Unix);
diff --git a/dist/PathTools/lib/File/Spec/Win32.pm b/dist/PathTools/lib/File/Spec/Win32.pm
index b05b535ebb..56c1ba900c 100644
--- a/dist/PathTools/lib/File/Spec/Win32.pm
+++ b/dist/PathTools/lib/File/Spec/Win32.pm
@@ -5,7 +5,7 @@ use strict;
 use Cwd ();
 require File::Spec::Unix;
 
-our $VERSION = '3.84';
+our $VERSION = '3.85';
 $VERSION =~ tr/_//d;
 
 our @ISA = qw(File::Spec::Unix);
diff --git a/mg.c b/mg.c
index 7a4727cedf..831e25117f 100644
--- a/mg.c
+++ b/mg.c
@@ -1356,6 +1356,15 @@ Perl_magic_setenv(pTHX_ SV *sv, MAGIC *mg)
             const char path_sep = ':';
 #endif
 
+#ifndef __VMS
+            /* Does this apply for VMS?
+             * Empty PATH on linux is treated same as ".", which is forbidden
+             * under taint. So check if the PATH variable is empty. */
+            if (!len) {
+                MgTAINTEDDIR_on(mg);
+                return 0;
+            }
+#endif
             /* set MGf_TAINTEDDIR if any component of the new path is
              * relative or world-writeable */
             while (s < strend) {
@@ -1372,7 +1381,8 @@ Perl_magic_setenv(pTHX_ SV *sv, MAGIC *mg)
                       /* Using Unix separator, e.g. under bash, so act line Unix */
                       || (PL_perllib_sep == ':' && *tmpbuf != '/')
 #else
-                      || *tmpbuf != '/'       /* no starting slash -- assume relative path */
+                      || *tmpbuf != '/' /* no starting slash -- assume relative path */
+                      || s == strend    /* trailing empty component -- same as "." */
 #endif
                       || (PerlLIO_stat(tmpbuf, &st) == 0 && (st.st_mode & 2)) ) {
                     MgTAINTEDDIR_on(mg);
diff --git a/t/op/taint.t b/t/op/taint.t
index f4f06f7461..8e81894e2d 100644
--- a/t/op/taint.t
+++ b/t/op/taint.t
@@ -25,7 +25,7 @@ if ($NoTaintSupport) {
     exit 0;
 }
 
-plan tests => 1054;
+plan tests => 1061;
 
 $| = 1;
 
@@ -145,14 +145,17 @@ my $TEST = 'TEST';
 {
     $ENV{'DCL$PATH'} = '' if $Is_VMS;
 
-    $ENV{PATH} = ($Is_Cygwin) ? '/usr/bin' : '';
+    # Empty path is the same as "." on *nix, so we have to set it
+    # to something or we will fail taint tests. perhaps setting it
+    # to "/" would be better. Anything absolute will do.
+    $ENV{PATH} = '/usr/bin';
     delete @ENV{@MoreEnv};
     $ENV{TERM} = 'dumb';
 
     is(eval { `$echo 1` }, "1\n");
 
     SKIP: {
-        skip "Environment tainting tests skipped", 4
+        skip "Environment tainting tests skipped", 11
           if $Is_MSWin32 || $Is_VMS;
 
 	my @vars = ('PATH', @MoreEnv);
@@ -164,6 +167,16 @@ my $TEST = 'TEST';
 	}
 	is("@vars", "");
 
+        # make sure that the empty path or empty path components
+        # trigger an "Insecure directory in $ENV{PATH}" error.
+        for my $path ("", ".", "/:", ":/", "/::/", ".:/", "/:.") {
+            local $ENV{PATH} = $path;
+            eval {`$echo 1`};
+            ok($@ =~ /Insecure directory in \$ENV\{PATH\}/,
+                "path '$path' is insecure as expected")
+                or diag "$@";
+        }
+
 	# tainted $TERM is unsafe only if it contains metachars
 	local $ENV{TERM};
 	$ENV{TERM} = 'e=mc2';
diff --git a/t/test.pl b/t/test.pl
index d92f28f8f2..5062ece575 100644
--- a/t/test.pl
+++ b/t/test.pl
@@ -776,6 +776,11 @@ sub untaint_path {
             $path = $path . $sep;
         }
         $path = $path . '/bin';
+    } elsif (!$is_vms and !length $path) {
+        # empty PATH is the same as a path of "." on *nix so to prevent
+        # tests from dieing under taint we need to return something
+        # absolute. Perhaps "/" would be better? Anything absolute will do.
+        $path = "/usr/bin";
     }
 
     $path;