🔐 Perl Security Essentials

Writing secure Perl code is a must, especially for web applications where user input is king. Always assume that input can be malicious, so sanitize, validate, and escape everything. Perl has built-in pragmas and modules that help keep your code clean and safe.

Some common security pitfalls in Perl include injection attacks (SQL injection, command injection), cross-site scripting (XSS), and unsafe file handling. Understanding and mitigating these risks will save your apps from getting pwned.

🛡️ Use strict and warnings

Start every Perl script with these pragmas to catch errors early and avoid sloppy code that could lead to security holes.

use strict;
use warnings;

🔍 Validate and Sanitize User Input

Never trust user input! Use regex or modules like Scalar::Util to verify input matches expected patterns.

my $username = param('username');
if ($username =~ /^[a-zA-Z0-9_]{3,20}$/) {
  # safe to use
} else {
  die "Invalid username!";
}

🛠️ Avoid Shell Injection

When calling external programs, use the list form of system or exec to avoid shell interpolation.

# BAD: vulnerable to injection
system("rm -rf $user_input");

# GOOD: safer approach
system('rm', '-rf', $user_input);

🗄️ Use Placeholders for Database Queries

Never directly interpolate variables into SQL statements. Use DBI’s placeholders to prevent SQL injection.

my $sth = $dbh->prepare("SELECT * FROM users WHERE username = ?");
$sth->execute($username);

🌐 Prevent Cross-Site Scripting (XSS)

Escape HTML output using modules like HTML::Entities before displaying user data in web pages.

use HTML::Entities;
my $safe_output = encode_entities($user_input);
print "<p>$safe_output</p>";
💡 Tip: Always keep your Perl modules up to date, and monitor CPAN security advisories for patches and vulnerabilities.

🔗 Helpful Modules