Chapter 10 Web Hacking Revised 10-29-12. Web Server Hacking.

Chapter 10Chapter 10

Web HackingWeb Hacking

Revised 10-29-12

Web Server Hacking Web Server Hacking

Popular Web ServersPopular Web Servers

Microsoft IIS/ASP/ASP.NETMicrosoft IIS/ASP/ASP.NET

LAMP (Linux/Apache/MySQL/PHP)LAMP (Linux/Apache/MySQL/PHP)

Oracle WebLogicOracle WebLogic– Link Ch 10jLink Ch 10j

IBM WebSphereIBM WebSphere– Link Ch 10kLink Ch 10k

IISIISPopularPopularat Bigat Big

CompaniesCompanies

– Link Ch 10lLink Ch 10l

Link Ch 10mLink Ch 10m

Attacking Web Server Attacking Web Server VulnerabilitiesVulnerabilities

An attacker with the right set of tools and An attacker with the right set of tools and ready-made exploits can bring down a ready-made exploits can bring down a vulnerable web server in minutesvulnerable web server in minutes

Some of the most devastating Internet Some of the most devastating Internet worms have historically exploited these worms have historically exploited these kinds of vulnerabilities kinds of vulnerabilities – Code Red and Nimda attacked IIS Code Red and Nimda attacked IIS

vulnerabilitiesvulnerabilities

Why the Risk is DecreasingWhy the Risk is Decreasing

The risk of such attacks is decreasing, The risk of such attacks is decreasing, because:because:– Newer versions of Web servers are less Newer versions of Web servers are less

vulnerablevulnerable– System administrators are better at System administrators are better at

configuring the platformsconfiguring the platforms– Vendor's "best practices" documents are Vendor's "best practices" documents are

betterbetter– Patches come out more rapidlyPatches come out more rapidly

Why the Risk is DecreasingWhy the Risk is Decreasing

Countermeasures are available, such as:Countermeasures are available, such as:– Sanctum/Watchfire's AppShield Sanctum/Watchfire's AppShield

A Web application firewall (link Ch_12n)A Web application firewall (link Ch_12n)

Microsoft's URLScan Microsoft's URLScan – Built in to IIS 6 and IIS 7Built in to IIS 6 and IIS 7

Link Ch_12oLink Ch_12o

Automated vulnerability-scanning products Automated vulnerability-scanning products and tools are availableand tools are available

Web Server Vulnerabilities Web Server Vulnerabilities

Sample filesSample files

Source code disclosureSource code disclosure

CanonicalizationCanonicalization

Server extensionsServer extensions

Input validation (for example, buffer Input validation (for example, buffer overflows)overflows)

Denial od ServiceDenial od Service

Sample filesSample files

Sample scripts and code snippets to illustrate creative Sample scripts and code snippets to illustrate creative use of a platformuse of a platformIn Microsoft's IIS 4.0 In Microsoft's IIS 4.0 – Sample code was installed by default Sample code was installed by default – showcode. asp and codebrews.asp showcode. asp and codebrews.asp – These files enabled an attacker to view almost any file on the These files enabled an attacker to view almost any file on the

server like this:server like this:

http://192.168.51.101/msadc/Samples/http://192.168.51.101/msadc/Samples/SELECTOR/showcode.asp?SELECTOR/showcode.asp?source=/../.. /../../../boot.ini source=/../.. /../../../boot.ini

http://192.168.51.101/iissamples/exair/http://192.168.51.101/iissamples/exair/howitworks/codebrws.asp?howitworks/codebrws.asp?source= source= /../../../../../winnt/repair/setup.log/../../../../../winnt/repair/setup.log

Sample Files CountermeasureSample Files Countermeasure

Remove sample files from production Remove sample files from production webserverswebservers

If you need the sample files, you can get If you need the sample files, you can get patches to improve thempatches to improve them– ColdFusion Expression Evaluator patchColdFusion Expression Evaluator patch– Link Ch 10pLink Ch 10p

Source Code Disclosure Source Code Disclosure

IIS 4 and 5 could reveal portions of source code IIS 4 and 5 could reveal portions of source code through the HTR vulnerability (Link Ch 10q)through the HTR vulnerability (Link Ch 10q)

Apache Tomcat and Oracle WebLogic had Apache Tomcat and Oracle WebLogic had similar issuessimilar issues

Attack URLs:Attack URLs:http://www.iisvictim.example/global.asa+.htrhttp://www.iisvictim.example/global.asa+.htr

http://www.weblogicserver.example/index.js%70http://www.weblogicserver.example/index.js%70

http://www.tomcatserver.example/examples/jsp/num/http://www.tomcatserver.example/examples/jsp/num/

numguess.js%70numguess.js%70

Source Code Disclosure Source Code Disclosure CountermeasuresCountermeasures

Apply patches (these vulnerabilities were Apply patches (these vulnerabilities were patched long ago)patched long ago)

Remove unneeded sample filesRemove unneeded sample files

Never put sensitive data in source code of Never put sensitive data in source code of filesfiles– You can never be sure source code is hidden You can never be sure source code is hidden

Canonicalization Attacks Canonicalization Attacks

There are many ways to refer to the same There are many ways to refer to the same filefile

C:\text.txtC:\text.txt

..\text.txt ..\text.txt

\\computer\C$\text.txt\\computer\C$\text.txt

The process of resolving a resource to The process of resolving a resource to a standard (canonical) name is called a standard (canonical) name is called canonicalizationcanonicalization

ASP::$DATA VulnerabilityASP::$DATA Vulnerability

Affected IIS 4 and earlier versionsAffected IIS 4 and earlier versions

Just adding ::$DATA to the end of an ASP Just adding ::$DATA to the end of an ASP page's URL revealed the source codepage's URL revealed the source codehttp://xyz.com/myasp.asp::$DATA http://xyz.com/myasp.asp::$DATA

Link Ch 10rLink Ch 10r

Apache Canonicalization Apache Canonicalization Vulnerability (from 2006)Vulnerability (from 2006)

When installed on Windows, capitalizing When installed on Windows, capitalizing CGI-BIN revealed source code for scriptsCGI-BIN revealed source code for scripts– http://target.com/CGI-BIN/script.plhttp://target.com/CGI-BIN/script.pl

CountermeasureCountermeasure– Store scripts in a directory outside the Store scripts in a directory outside the

document treedocument tree

Link Ch 10z10Link Ch 10z10

Unicode/Double Decode Unicode/Double Decode Vulnerabilities (from 2000)Vulnerabilities (from 2000)

Strings like %c0%af could be used to Strings like %c0%af could be used to sneak characters like \ past URL filterssneak characters like \ past URL filters

Attack URL example:Attack URL example:

http://10.1.1.3/scripts/http://10.1.1.3/scripts/..%c0%af..%c0%af..%c0%af....%c0%af..%c0%af..%c0%af../winnt/system32/cmd.exe?/c+dir/winnt/system32/cmd.exe?/c+dir

Exploited by the Nimda wormExploited by the Nimda worm

Image from Link Ch 10z11 Image from Link Ch 10z11 (http://webhacking.org.ua/042.htm)(http://webhacking.org.ua/042.htm)

Canonicalization Attack Canonicalization Attack CountermeasuresCountermeasures

Patch your Web platformPatch your Web platformCompartmentalize your application Compartmentalize your application directory structure directory structure – Limit access of Web Application user to Limit access of Web Application user to

minimal requiredminimal required

Clean URLs with URLScan and similar Clean URLs with URLScan and similar productsproducts– Remove Unicode or double-hex-encoded Remove Unicode or double-hex-encoded

characters before they reach the servercharacters before they reach the server

Server Extensions Server Extensions

Code libraries tacked on to the core HTTP Code libraries tacked on to the core HTTP engine to provide extra featuresengine to provide extra features– Dynamic script execution (for example, Dynamic script execution (for example,

Microsoft ASP)Microsoft ASP)– Site indexingSite indexing– Internet Printing Protocol Internet Printing Protocol – Web Distributed Authoring and Versioning Web Distributed Authoring and Versioning

(WebDAV)(WebDAV)– Secure Sockets Layer (SSL)Secure Sockets Layer (SSL)

Server ExtensionsServer Extensions

Each of these extensions has Each of these extensions has vulnerabilities, such as buffer overflowsvulnerabilities, such as buffer overflows

Microsoft WebDAV "Translate: f" problem Microsoft WebDAV "Translate: f" problem – Add "translate: f" to header of the HTTP GET Add "translate: f" to header of the HTTP GET

request, and a \ to the end of the URLrequest, and a \ to the end of the URL– Reveals source codeReveals source code

Links Ch 10u, vLinks Ch 10u, v

Server Extensions Exploitation Server Extensions Exploitation CountermeasuresCountermeasures

Patch or disable vulnerable extensionsPatch or disable vulnerable extensions– The The Translate: fTranslate: f problem was patched long problem was patched long

agoago

Buffer Overflows Buffer Overflows

Web servers, like all other computers, can Web servers, like all other computers, can be compromised by buffer overflowsbe compromised by buffer overflows

The Web server is easy to find, and The Web server is easy to find, and connected to the Internet, so it is a connected to the Internet, so it is a common targetcommon target

Famous Buffer OverflowsFamous Buffer Overflows

IIS HTR Chunked Encoding Transfer Heap IIS HTR Chunked Encoding Transfer Heap OverflowOverflow– Affects Microsoft IIS 4.0, 5.0, and 5.1Affects Microsoft IIS 4.0, 5.0, and 5.1– Leads to remote denial of service or remote code Leads to remote denial of service or remote code

execution at the IWAM_ execution at the IWAM_ MACHINENAMEMACHINENAME privilege privilege levellevel

IIS's Indexing Service extension (idq.dll)IIS's Indexing Service extension (idq.dll)– A buffer overflow used by the infamous Code Red A buffer overflow used by the infamous Code Red

wormworm

Internet Printing Protocol (IPP) vulnerabilityInternet Printing Protocol (IPP) vulnerability


Apache mod_rewrite vulnerabilityApache mod_rewrite vulnerability– Affects all versions up to and including Apache 2.2.0Affects all versions up to and including Apache 2.2.0– Results in remote code execution at the web server Results in remote code execution at the web server

contextcontext


Apache mod_ssl vulnerabilityApache mod_ssl vulnerability– Also known as the Slapper wormAlso known as the Slapper worm– Affects all versions up to and including Apache 2.0.40Affects all versions up to and including Apache 2.0.40– Results in remote code execution at the super-user Results in remote code execution at the super-user

levellevel

Apache also suffered from a vulnerability in the Apache also suffered from a vulnerability in the way it handled HTTP requests encoded with way it handled HTTP requests encoded with chunked encodingchunked encoding– Resulted in a worm dubbed "Scalper"Resulted in a worm dubbed "Scalper"– Thought to be the first Apache worm Thought to be the first Apache worm

Buffer Overflow CountermeasuresBuffer Overflow Countermeasures

Apply software patchesApply software patches

Scan your server with a vulnerability Scan your server with a vulnerability scanner scanner

Denial of ServiceDenial of Service

Hacktivism is the new ego-driven attackHacktivism is the new ego-driven attack

Low Orbit Ion CannonLow Orbit Ion Cannon– Simple attack toolSimple attack tool

th3j3st3r's XerXesth3j3st3r's XerXes– Appears to perform layer 7 attacks, like Appears to perform layer 7 attacks, like

SlowLoris and RUDYSlowLoris and RUDY

Link Ch 10z_12Link Ch 10z_12

Web Server Vulnerability Scanners Web Server Vulnerability Scanners

Nikto checks for common Web Nikto checks for common Web server vulnerabilitiesserver vulnerabilities– It is not subtle—it leaves obvious It is not subtle—it leaves obvious

traces in log filestraces in log files– Link Ch 10z01Link Ch 10z01

Nessus/OpenVASNessus/OpenVAS– Not directly focused on web Not directly focused on web

serversservers

Nikto DemonstrationNikto Demonstration

Scan DVL Web Server with NiktoScan DVL Web Server with Nikto

Web Application HackingWeb Application Hacking

Web Application Hacking Web Application Hacking

Attacks on applications themselves, as Attacks on applications themselves, as opposed to the web server software upon opposed to the web server software upon which these applications runwhich these applications run

The same techniquesThe same techniques– Input-validation attacksInput-validation attacks– Source code disclosure attacksSource code disclosure attacks– etc.etc.

Finding Vulnerable Web Apps with Finding Vulnerable Web Apps with Google DorksGoogle Dorks

You can find unprotected directories with You can find unprotected directories with searches like this:searches like this:– "Index of /admin""Index of /admin"– "Index of /password""Index of /password"– "Index of /mail""Index of /mail"

You can find password hints, vulnerable Web You can find password hints, vulnerable Web servers with FrontPage, MRTG traffic analysis servers with FrontPage, MRTG traffic analysis pages, .NET information, improperly configured pages, .NET information, improperly configured Outlook Web Access (OWA) servers…Outlook Web Access (OWA) servers…And many moreAnd many more– Link Ch 1aLink Ch 1a

Web Crawling Web Crawling

Examine a Web site carefully for Low Examine a Web site carefully for Low Hanging Fruit Hanging Fruit – Local path informationLocal path information– Backend server names and IP addressesBackend server names and IP addresses– SQL query strings with passwordsSQL query strings with passwords– Informational comments Informational comments

Look in static and dynamic pages, include Look in static and dynamic pages, include and other support files, source codeand other support files, source code

Web-Crawling Tools Web-Crawling Tools

wget is a simple command-line tool to wget is a simple command-line tool to download a page, and can be used in download a page, and can be used in scriptsscripts– Available for Linux and WindowsAvailable for Linux and Windows– Link Ch 10z03Link Ch 10z03

HTTrack Website CopierHTTrack Website Copier– Free cross-platform applicationFree cross-platform application– Link Ch 10z13Link Ch 10z13

Web Application Assessment Web Application Assessment

Once the target application content has Once the target application content has been crawled and thoroughly analyzedbeen crawled and thoroughly analyzed

Probe the features of the applicationProbe the features of the application– AuthenticationAuthentication– Session managementSession management– Database interactionDatabase interaction– Generic input validationGeneric input validation– Application logicApplication logic

Tools for Web Application Tools for Web Application HackingHacking

Browser plug-insBrowser plug-ins

Free tool suitesFree tool suites

Commercial web application scannersCommercial web application scanners

Tamper Data ProjectTamper Data Project

Acts like a proxy serverActs like a proxy server

You can see POST data and alter itYou can see POST data and alter it

This will defeat client-side validationThis will defeat client-side validation

JavaScript DebuggerJavaScript Debugger

Examine and step through JavaScriptExamine and step through JavaScript

Tool SuitesTool Suites

Proxies sit between client and Web Proxies sit between client and Web application server, like a man-in-the-application server, like a man-in-the-middle attackmiddle attack

Microsoft Fiddler can intercept and log Microsoft Fiddler can intercept and log requests and responsesrequests and responses

WebGoat DemoWebGoat Demo

Tools for Web Application Tools for Web Application Assessment Assessment

WebScarabWebScarab– Allows user to intercept and alter HTTPAllows user to intercept and alter HTTP– Includes spidering and fuzzingIncludes spidering and fuzzing– Runs on any platformRuns on any platform– Free, from OWASPFree, from OWASP

Burp SuiteBurp Suite– Proxy, Repeater, Sequencer, Spider, IntruderProxy, Repeater, Sequencer, Spider, Intruder– Powerful tool to craft automated attacksPowerful tool to craft automated attacks– Free version is limitedFree version is limited

Expensive Commercial ToolsExpensive Commercial Tools

HP WebInspect and Security ToolkitHP WebInspect and Security Toolkit

Rational AppScanRational AppScan

Cenzic HailstormCenzic Hailstorm

Cenzic HailstormCenzic Hailstorm

Highly rated commercial Web applicaion vulnerability Highly rated commercial Web applicaion vulnerability scannerscanner– Links Ch 11o, 11pLinks Ch 11o, 11p

Common Web Application Common Web Application Vulnerabilities Vulnerabilities

Common Web Application Common Web Application VulnerabilitiesVulnerabilities

Cross-Site Scripting (XSS)Cross-Site Scripting (XSS)

SQL InjectionSQL Injection

Cross-Site Request Forgery (CSRF)Cross-Site Request Forgery (CSRF)

HTTP Response SplittingHTTP Response Splitting

Cross-Site Scripting (XSS) Attacks Cross-Site Scripting (XSS) Attacks

One user injects code that attacks another userOne user injects code that attacks another user

Common on guestbooks, comment pages, Common on guestbooks, comment pages, forums, etc.forums, etc.

Caused by failure to filter out HTML tagsCaused by failure to filter out HTML tags– These characters < > " &These characters < > " &– Also watch out for hex-encoded versionsAlso watch out for hex-encoded versions

%3c instead of <%3c instead of <

%3e instead of >%3e instead of >

%22 instead of "%22 instead of "

XSS Scripting EffectsXSS Scripting Effects

Steal another user's authentication Steal another user's authentication cookiecookie– Hijack sessionHijack session

Harvest stored passwords from the Harvest stored passwords from the target's browsertarget's browser

Take over machine through browser Take over machine through browser vulnerabilityvulnerability

Redirect WebpageRedirect Webpage

Many, many other evil things…Many, many other evil things…5353

Common XSS Payloads Common XSS Payloads

See Link Ch 10z06See Link Ch 10z06

Cross-Site Scripting Cross-Site Scripting Countermeasures Countermeasures

Filter out < > ( ) # & and the variants of themFilter out < > ( ) # & and the variants of themHTML-encode output, so a character like < HTML-encode output, so a character like < becomes < -- that will stop scripts from runningbecomes < -- that will stop scripts from runningIn IE 6 SP1 or later, an application can set In IE 6 SP1 or later, an application can set HttpOnly Cookies, which prevents them from HttpOnly Cookies, which prevents them from being accessed by scriptsbeing accessed by scripts

Analyze your applications for XSS vulnerabilitiesAnalyze your applications for XSS vulnerabilities– Fix the errors you findFix the errors you find

Common Web Application Common Web Application Vulnerabilities Vulnerabilities

SQL Injection SQL Injection

SQL Injection ComicSQL Injection Comic

xkcd.org – a great comicxkcd.org – a great comic

Link Ch 10iLink Ch 10i

Automated SQL Injection Tools Automated SQL Injection Tools

HavijHavijsqlmapsqlmapSQL Power InjectorSQL Power InjectorAbsintheAbsintheSqlninjaSqlninja

SQL Injection Countermeasures SQL Injection Countermeasures

Perform strict input validationPerform strict input validationReplace direct SQL statements with Replace direct SQL statements with

stored procedures, prepared statements, stored procedures, prepared statements, or ADO command objectsor ADO command objects– That way they can't be modifiedThat way they can't be modified

Implement default error handlingImplement default error handling– Use a general error message for all errorsUse a general error message for all errors


Lock down ODBCLock down ODBC– Disable messaging to clients. Don't let regular Disable messaging to clients. Don't let regular

SQL statements through. This ensures that no SQL statements through. This ensures that no client, not just the web application, can client, not just the web application, can execute arbitrary SQL.execute arbitrary SQL.

Lock down the database server Lock down the database server configurationconfiguration– Specify users, roles, and permissions, so Specify users, roles, and permissions, so

even if SQL statements are injected, they even if SQL statements are injected, they can't do any harmcan't do any harm


Use Programmatic FrameworksUse Programmatic Frameworks– Tools such as Hibernate or LINQTools such as Hibernate or LINQ– Encourage the use of bind variablesEncourage the use of bind variables

Microsoft's Source Code Analyzer for SQL Microsoft's Source Code Analyzer for SQL Injection toolInjection tool– Link Ch 10z14Link Ch 10z14

Cross-Site Request Forgery (CSRF)Cross-Site Request Forgery (CSRF)Hijack a session by stealing cookiesHijack a session by stealing cookiesWe did this with hamster and ferretWe did this with hamster and ferret


Trick user into clicking on a malicious URLTrick user into clicking on a malicious URLIf server response contains user input, the If server response contains user input, the

HTTP response can be prematurely HTTP response can be prematurely terminated and a extra code can be terminated and a extra code can be insertedinserted

Result similar to XSSResult similar to XSSCountermeasures:Countermeasures:

– Validate inputValidate input


In WebGoatIn WebGoat

Other AttacksOther Attacks

Misuse of hidden tagsMisuse of hidden tagsServer Side IncludesServer Side IncludesDatabase hackingDatabase hacking

– Database discoveryDatabase discovery– Database vulnerabilitiesDatabase vulnerabilities

Network attacksNetwork attacksDatabase engine bugsDatabase engine bugsVulnerable built-in stored objectsVulnerable built-in stored objectsWeak or default passwordsWeak or default passwords

Chapter 10 Web Hacking Revised 10-29-12. Web Server Hacking.

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Transcript of Chapter 10 Web Hacking Revised 10-29-12. Web Server Hacking.