Dip Your Toes in theSea of Security

James TitcumbPHP UK Conference 2016

James Titcumbwww.jamestitcumb.comwww.roave.comwww.phphants.co.ukwww.phpsouthcoast.co.uk

@asgrim

Who is this guy?

Use “phpuk16” discount code!

Some simple code...<?php

$a = (int)filter_var($_GET['a'], FILTER_SANITIZE_NUMBER_INT);

$b = (int)filter_var($_GET['b'], FILTER_SANITIZE_NUMBER_INT);

$result = $a + $b;

printf('The answer is %d', $result);

The Golden Rules

The Golden Rules(my made up golden rules)

1. Keep it simple

2. Know the risks

3. Fail securely

4. Don’t reinvent the wheel

5. Never trust anything

OWASP& the OWASP Top 10

https://www.owasp.org/

Application Security(mainly PHP applications)

Always remember…

Filter InputEscape Output

© 2003 Disney/Pixar. All Rights Reserved.

SQL Injection (#1)

SQL Injection (#1)

http://xkcd.com/327/

SQL Injection (#1)

1. Use PDO / mysqli2. Use prepared / parameterized statements

SQL Injection (#1)<?php

// user_id=1; DROP TABLE users; --

$user_id = $_GET['user_id'];

$sql = "

SELECT * FROM users

WHERE user_id = {$user_id}";

$db->execute($sql); ✘

SQL Injection (#1)<?php

$user_id = $_GET['user_id'];

$sql = "

SELECT * FROM users

WHERE user_id = :userid";

$stmt = $db->prepare($sql);

$stmt->bind('userid', $user_id);

$stmt->execute(); ✓

© 2003 Disney/Pixar. All Rights Reserved.

exec($_GET)https://github.com/search?q=exec%28%24_GET&ref=cmdform&type=Code

eval()https://github.com/search?q=eval%28%24_GET&type=Code&ref=searchresults

Cross-Site Scripting / XSS (#3)© 2003 Disney/Pixar. All Rights Reserved.

Cross-Site Scripting / XSS (#3)

● Escape output<?php

$unfilteredInput = '<script type="text/javascript">...</script>';

// Unescaped - JS will run :'(

echo $unfilteredInput;

// Escaped - JS will not run :)

echo htmlspecialchars($string, ENT_QUOTES, 'UTF-8');

Cross-Site Request Forgeryor CSRF (#8)

http://www.factzoo.com/invertebrates/cuttlefish-chameleon-of-the-sea.html

<?php

if (!$isPost) {

$csrfToken = base64_encode(random_bytes(32)));

$_SESSION['csrf_token'] = $csrfToken;

// ... output the form ...

echo '<input type="hidden" name="csrf_token" value="'.$csrfToken.'" />';

} else if ($isPost) {

if (hash_equals($_SESSION['csrf_token'], $_POST['csrf_token'])) {

die("Token invalid...");

}

// ... handle the form ...

}

Cross-Site Request Forgery / CSRF (#8)

<?php

if (!$isPost) {

$csrfToken = base64_encode(random_bytes(32)));

$_SESSION['csrf_token'] = $csrfToken;

// ... output the form ...

echo '<input type="hidden" name="csrf_token" value="'.$csrfToken.'" />';

} else if ($isPost) {

if (hash_equals($_SESSION['csrf_token'], $_POST['csrf_token'])) {

die("Token invalid...");

}

// ... handle the form ...

}

Cross-Site Request Forgery / CSRF (#8)

<?php

if (!$isPost) {

$csrfToken = base64_encode(random_bytes(32)));

$_SESSION['csrf_token'] = $csrfToken;

// ... output the form ...

echo '<input type="hidden" name="csrf_token" value="'.$csrfToken.'" />';

} else if ($isPost) {

if (hash_equals($_SESSION['csrf_token'], $_POST['csrf_token'])) {

die("Token invalid...");

}

// ... handle the form ...

}

Cross-Site Request Forgery / CSRF (#8)

Timing attacks

From zend_is_identical:return (Z_STR_P(op1) == Z_STR_P(op2) ||

(Z_STRLEN_P(op1) == Z_STRLEN_P(op2) &&

memcmp(Z_STRVAL_P(op1), Z_STRVAL_P(op2), Z_STRLEN_P(op1)) == 0));

Timing attacksActual string: “foobar”● a (0.00001)● aa (0.00001)● aaa (0.00001)● aaaa (0.00001)● aaaaa (0.00001)● aaaaaa (0.00002) ← success!● aaaaaaa (0.00001)● aaaaaaaa (0.00001)● aaaaaaaaa (0.00001)

Timing attacks 1 int memcmp(const void* s1, const void* s2,size_t n)

2 {

3 const unsigned char *p1 = s1, *p2 = s2;

4 while(n--)

5 if( *p1 != *p2 )

6 return *p1 - *p2;

7 else

8 p1++,p2++;

9 return 0;

10 }

http://clc-wiki.net/wiki/C_standard_library:string.h:memcmp#Implementation

Timing attacksActual string: “foobar”● “aaaaaa” (0.00001)● “baaaaa” (0.00001) ● …● “faaaaa” (0.00002) ← success!● “fbaaaa” (0.00002)● “fcaaaa” (0.00002)● …● “foaaaa” (0.00003) ← success!

Sensitive Data Exposure (#6)© 2003 Disney/Pixar. All Rights Reserved.

Sensitive Data Exposure (#6)

© 2003 Disney/Pixar. All Rights Reserved.

curl + https<?php

curl_setopt($ch, CURLOPT_SSL_VERIFYHOST, false);

curl_setopt($ch, CURLOPT_SSL_VERIFYPEER, false);

✘

curl + https<?php

curl_setopt($ch, CURLOPT_SSL_VERIFYHOST, 2);

curl_setopt($ch, CURLOPT_SSL_VERIFYPEER, true);

curl_setopt($ch, CURLOPT_CAINFO, "/path/to/certificate");

✓

© 2003 Disney/Pixar. All Rights Reserved.

Third Party Code

Third Party Code!!! WARNING !!!

Third Party Code github.com/ /SecurityAdvisories

!!! WARNING !!!

We are not allsecurity experts!

We are not allsecurity experts!

… but we CAN write secure code

Hack your own system!

© 2003 Disney/Pixar. All Rights Reserved.

What do you want?

Think like a hacker

How do you get it?

Think Differently

Threat ModellingD.R.E.A.D.

© Buena Vista Pictures

Threat Modelling

DamageREAD

© Buena Vista Pictures

Threat Modelling

DamageReproducibilityEAD

© Buena Vista Pictures

Threat Modelling

DamageReproducibilityExploitabilityAD

© Buena Vista Pictures

Threat Modelling

DamageReproducibilityExploitabilityAffected usersD

© Buena Vista Pictures

Threat Modelling

DamageReproducibilityExploitabilityAffected usersDiscoverability

© Buena Vista Pictures

Put them in orderAnd fix them!

© Buena Vista Pictures

Authentication& Authorization

AuthenticationVerifying Identity

Case Study: Custom Authentication

We thought about doing this…

Case Study: Custom Authentication

We thought about doing this…

Case Study: Custom Authentication

We thought about doing this…

✘

Password Hashingpassword_hash()

AuthorizationVerifying Access

CRYPTOGRAPHYIS

HARD

CRYPTOGRAPHYIS

HARDNEVER EVER “ROLL YOUR OWN”

CRYPTOGRAPHYIS

HARDNEVER EVER “ROLL YOUR OWN”

EVER!!!

How to encrypt then?

I’ve got some great ideas for encryption...

Image: The Guardian (http://goo.gl/pUkyvO)

How to encrypt then?libsodium PECL package

Linux Server Security

Create an SSH Fortress

Firewalls

iptables#!/bin/bash

IPT="/sbin/iptables"

$IPT --flush

$IPT --delete-chain

$IPT -P INPUT DROP

$IPT -P FORWARD DROP

$IPT -P OUTPUT DROP

# Loopback

$IPT -A INPUT -i lo -j ACCEPT

$IPT -A OUTPUT -o lo -j ACCEPT

# Inbound traffic

$IPT -A INPUT -p tcp --dport ssh -j ACCEPT

$IPT -A INPUT -p tcp --dport 80 -j ACCEPT

$IPT -A INPUT -p tcp --dport 443 -j ACCEPT

# Outbound traffic

$IPT -A OUTPUT -p tcp --dport 80 -j ACCEPT

$IPT -A OUTPUT -p tcp --dport 443 -j ACCEPT

$IPT -A OUTPUT -p udp --dport 53 -m state --state NEW -j ACCEPT

ufwsudo ufw enable

sudo ufw allow 22

sudo ufw allow 80

Mitigate Brute Force Attacks

Install OnlyWhat You Need

© 2003 Disney/Pixar. All Rights Reserved.

+

Case Study: Be Minimal

Internets

Postfix

Squid Proxy(badly configured)

hacker

spam

Resources

● http://securingphp.com/● https://www.owasp.org/● http://blog.ircmaxell.com/● https://github.com/paragonie/random_compat● https://github.com/ircmaxell/password_compat● https://paragonie.com/blog● https://websec.io/resources.php

The Golden Rules

1. Keep it simple2. Know the risks3. Fail securely4. Don’t reinvent the wheel5. Never trust anything / anyone

If you follow all this, you get...

If you follow all this, you get...

Any questions? :)

https://joind.in/talk/c2bb0James Titcumb @asgrim