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Dip Your Toes inthe Sea of Security
James TitcumbInternational PHP Conference 2017
$ whoami
James Titcumb
www.jamestitcumb.com
www.roave.com
@asgrim
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@asgrim
Some simple PHP 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);
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The Golden Rules
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The Golden Rules(my made up golden rules)
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1. Keep it simple
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2. Know the risks
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3. Fail securely
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4. Don’t reinvent the wheel
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5. Never trust anything
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Application Security(mainly PHP applications)
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Always remember…
Filter InputEscape Output
@asgrim© 2003 Disney/Pixar. All Rights Reserved.
SQL Injection (#1)
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SQL Injection (#1)
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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); ✘
@asgrim
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);
$stmt->execute();✓
@asgrim© 2003 Disney/Pixar. All Rights Reserved.
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exec($_GET)
https://github.com/search?q=exec%28%24_GET&ref=cmdform&type=Code
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eval()
https://github.com/search?q=eval%28%24_GET&type=Code&ref=searchresults
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Cross-Site Scripting / XSS (#3)
© 2003 Disney/Pixar. All Rights Reserved.
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Cross-Site Scripting / XSS (#3)
<?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');
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Cross-Site Request Forgery / CSRF (#8)http://www.factzoo.com/invertebrates/cuttlefish-chameleon-of-the-sea.html
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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'], $_POST['csrf_token'])) {
die("Token invalid...");
}
// ... handle the form ...
}
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<?php
if (!$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'], $_POST['csrf_token'])) {
die("Token invalid...");
}
// ... handle the form ...
}
Cross-Site Request Forgery / CSRF (#8)
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Cross-Site Request Forgery / CSRF (#8)
<?php
if (!$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'], $_POST['csrf_token'])) {
die("Token invalid...");
}
// ... handle the form ...
}
@asgrim
Timing attacks
// From zend_is_identical:
return (Z_STR_P(op1) == Z_STR_P(op2) ||
(Z_STRLEN_P(op1) == Z_STRLEN_P(op2) &&
memcmp(Z_STRVAL_P(op1), Z_STRVAL_P(op2), Z_STRLEN_P(op1)) == 0));
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Timing attacks
Actual string: “foobar”
● a (0.00001)● aa (0.00001)● aaa (0.00001)● aaaa (0.00001)● aaaaa (0.00001)● aaaaaa (0.00002) ← success!● aaaaaaa (0.00001)
● aaaaaaaa (0.00001)
● aaaaaaaaa (0.00001)
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Timing attacks
1 int memcmp(const void* s1, const void* s2,size_t n)
2 {
3 const unsigned char *p1 = s1, *p2 = s2;
4 while(n--)
5 if( *p1 != *p2 )
6 return *p1 - *p2;
7 else
8 p1++,p2++;
9 return 0;
10 }
http://clc-wiki.net/wiki/C_standard_library:string.h:memcmp#Implementation
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Timing attacks
Actual string: “foobar”
● “aaaaaa” (0.00001)● “baaaaa” (0.00001) ● …● “faaaaa” (0.00002) ← success!● “fbaaaa” (0.00002)● “fcaaaa” (0.00002)● …● “foaaaa” (0.00003) ← success!
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Sensitive Data Exposure (#6)© 2003 Disney/Pixar. All Rights Reserved.
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Sensitive Data Exposure (#6)
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curl + https
<?php
curl_setopt($ch, CURLOPT_SSL_VERIFYHOST, false);
curl_setopt($ch, CURLOPT_SSL_VERIFYPEER, false);
✘
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curl + https
<?php
curl_setopt($ch, CURLOPT_SSL_VERIFYHOST, 2);
curl_setopt($ch, CURLOPT_SSL_VERIFYPEER, true);
curl_setopt($ch, CURLOPT_CAINFO, "/path/to/certificate");
✓
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Third Party Code
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Third Party Code!!! WARNING !!
!
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Third Party Code github.com/ /SecurityAdvisories
!!! WARNING !!!
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Dependencies Disappearing
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composer.lock(and other stuff in web root)
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We are not allsecurity experts!
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We are not allsecurity experts!
… but we CAN write secure code
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Hack your own system!
© 2003 Disney/Pixar. All Rights Reserved.
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What do you want?
Think like a hacker
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How do you get it?
Think Differently
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Threat ModellingD.R.E.A.D.
© Buena Vista Pictures
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Threat Modelling
Damage
R
E
A
D
© Buena Vista Pictures
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Threat Modelling
Damage
Reproducibility
E
A
D
© Buena Vista Pictures
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Threat Modelling
Damage
Reproducibility
Exploitability
A
D
© Buena Vista Pictures
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Threat Modelling
Damage
Reproducibility
Exploitability
Affected users
D
© Buena Vista Pictures
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Threat Modelling
Damage
Reproducibility
Exploitability
Affected users
Discoverability
© Buena Vista Pictures
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Rank them in orderAnd fix them!
© Buena Vista Pictures
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Authentication& Authorization
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AuthenticationVerifying Identity
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Case Study: Custom Authentication
We thought about doing this…
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Case Study: Custom Authentication
We thought about doing this…
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Case Study: Custom Authentication
We thought about doing this…
✘
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Password Hashingpassword_hash()
(basically, bcrypt with proper salt)
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Two Factor Authentication
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AuthorizationVerifying Access
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CRYPTOGRAPHYIS
HARD
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CRYPTOGRAPHYIS
HARDNEVER EVER “ROLL YOUR OWN”
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CRYPTOGRAPHYIS
HARDNEVER EVER “ROLL YOUR OWN”
EVER!!!
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How to encrypt then?
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I’ve got some great ideas for encryption...
Image: IBTimes (http://goo.gl/zPVeo0)
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How to encrypt then?sodium+halite or Defuse php-encryption
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Linux Server Security
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Create an SSH Fortress
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Firewalls
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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
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iptables
https://twitter.com/sadserver/status/615988393198026752
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ufw
sudo ufw enable
sudo ufw allow 22
sudo ufw allow 80
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Mitigate Brute Force Attacks
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Install Only What You Need
@asgrim© 2003 Disney/Pixar. All Rights Reserved.
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+
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Case Study: Be Minimal
Internets
Postfix
Squid Proxy(badly configured)
hacker
spam
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Resources
● http://securingphp.com/● https://www.owasp.org/● http://blog.ircmaxell.com/● https://github.com/paragonie/random_compat● https://github.com/paragonie/sodium_compat● https://github.com/ircmaxell/password_compat● https://paragonie.com/blog● https://websec.io/resources.php● https://www.digitalocean.com/community/tutorials/initial-server-setup-with-ubuntu-16-04● https://www.kali.org/
@asgrim
The Golden Rules
1. Keep it simple2. Know the risks3. Fail securely4. Don’t reinvent the wheel5. Never trust anything / anyone
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If you follow all this, you get...
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If you follow all this, you get...
Any questions?
...James Titcumb@asgrim
