add perlcritic module to disallow system/exec

src/lib/Perl/Critic/Policy/Hydra/ProhibitShellInvokingSystemCalls.pm

@@ -0,0 +1,103 @@
+package Perl::Critic::Policy::Hydra::ProhibitShellInvokingSystemCalls;
+
+use strict;
+use warnings;
+use constant;
+
+use Perl::Critic::Utils qw{ :severities :classification :ppi };
+use base 'Perl::Critic::Policy';
+
+our $VERSION = '1.000';
+
+use constant DESC => q{Shell-invoking system calls are prohibited};
+use constant EXPL => q{Use list form system() or IPC::Run3 for better security. String form invokes shell and is vulnerable to injection};
+
+sub supported_parameters { return ()                         }
+sub default_severity     { return $SEVERITY_HIGHEST         }
+sub default_themes       { return qw( hydra security )       }
+sub applies_to           { return 'PPI::Token::Word'         }
+
+sub violates {
+    my ( $self, $elem, undef ) = @_;
+
+    # Only check system() and exec() calls
+    return () unless $elem->content() =~ /^(system|exec)$/;
+    return () unless is_function_call($elem);
+
+    # Skip method calls (->system or ->exec)
+    my $prev = $elem->sprevious_sibling();
+    return () if $prev && $prev->isa('PPI::Token::Operator') && $prev->content() eq '->';
+
+    # Get first argument after function name, skipping whitespace
+    my $args = $elem->snext_sibling();
+    return () unless $args;
+    $args = $args->snext_sibling() while $args && $args->isa('PPI::Token::Whitespace');
+
+    # For parenthesized calls, look inside
+    my $search_elem = $args;
+    if ($args && $args->isa('PPI::Structure::List')) {
+        $search_elem = $args->schild(0);
+        return () unless $search_elem;
+    }
+
+    # Check if it's list form (has comma)
+    my $current = $search_elem;
+    if ($current && $current->isa('PPI::Statement')) {
+        # Look through statement children
+        for my $child ($current->schildren()) {
+            return () if $child->isa('PPI::Token::Operator') && $child->content() eq ',';
+        }
+    } else {
+        # Look through siblings for non-parenthesized calls
+        while ($current) {
+            return () if $current->isa('PPI::Token::Operator') && $current->content() eq ',';
+            last if $current->isa('PPI::Token::Structure') && $current->content() eq ';';
+            $current = $current->snext_sibling();
+        }
+    }
+
+    # Check if first arg is array variable
+    my $first = $search_elem->isa('PPI::Statement') ?
+                $search_elem->schild(0) : $search_elem;
+    return () if $first && $first->isa('PPI::Token::Symbol') && $first->content() =~ /^[@]/;
+
+    # Check if it's a safe single-word command
+    if ($first && $first->isa('PPI::Token::Quote')) {
+        my $content = $first->string();
+        return () if $content =~ /^[a-zA-Z0-9_\-\.\/]+$/;
+    }
+
+    return $self->violation( DESC, EXPL, $elem );
+}
+
+1;
+
+__END__
+
+=pod
+
+=head1 NAME
+
+Perl::Critic::Policy::Hydra::ProhibitShellInvokingSystemCalls - Prohibit shell-invoking system() and exec() calls
+
+=head1 DESCRIPTION
+
+This policy prohibits the use of C<system()> and C<exec()> functions when called with a single string argument,
+which invokes the shell and is vulnerable to injection attacks.
+
+The list form (e.g., C<system('ls', '-la')>) is allowed as it executes directly without shell interpretation.
+For better error handling and output capture, consider using C<IPC::Run3>.
+
+=head1 CONFIGURATION
+
+This Policy is not configurable except for the standard options.
+
+=head1 AUTHOR
+
+Hydra Development Team
+
+=head1 COPYRIGHT
+
+Copyright (c) 2025 Hydra Development Team. All rights reserved.
+
+=cut