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WEB SYSTEM

Components of a GenericWeb Application System

URL Mappings to the WebApplication System

Web Application Architecture

Web Server vs Web Application

Web Server: Serves client request and forward to proper application for

further processing (e.g. IIS, Apache, thttpd and etc.) Web Application:

Using programming language (e.g. ASP, PHP, Java, .Net, Perl or C) to

implement business logic and serve the client Web Application does not run without Web Server Web Server does run without Web Application (Serving

static content) Web Application should contain:

Web Server and underlying OS Web Application Code Backend Server

Web Server Vulnerability

Can be identified by: Port scan for web related ports (TCP 80, 443 and etc) Vulnerability scanner (Whisker.pl, N-Stealth, Nikto.pl

and others) Example:

IIS File system traversal vulnerability Unicode and superflous decode vulnerability Various buffer overflow in ISAPI filters (.ida, .printer,

WebDAV and etc)

Impact: Usually the attacker can take over the system running

the web server

Web Application Vulnerability

Vulnerability on web application itself Can be identified by:

Source code review Application testing

Automatic scanner Manual testing

Example: SQL or command Injection E-Shop lifting Passport reset password flaw

Impact: Data confidentiality and integrity breached System compromised

Flowchart for a One-WayWeb Hack

We need two things to make an effective

attack: Interactive terminal

access Ability to transfer files

Step 1: Finding the Entry Point

URL parsing vulnerability n Unicode / Double decode attack http://www1.example.com/scripts/..%c0%af../winnt/system32/cmd.Exe?/C+copy+c:\winnt\

system32\cmd.Exe+c:\inetpub \scripts

Parameter parsing vulnerability Example: script uses open() insecurely

http://www2.example.com/cgi-bin/news.cgi?story=101003.txt|cp+/bin/sh+/usr/local/apache/cgi-bin/sh.cgi

SQL Injection Etc…

Invoking the CommandInterpreter

Invoking the CommandInterpreter, con’t

Care must be taken to get cmd.exe to receive commands properly Content-length must be right Remember to run “exit” command

Make a script to automate POSTing commands This can be done for /bin/sh, too

Web Based CommandPrompt

POSTing commands isn’t desirable We want to run commands interactively

And we don’t want to trip an IDS or get blocked by a firewall

Solution: web based command prompt

Web Based Command Prompt (WCP)

Installing the Web BasedCommand Prompt

How do we get our script on the server? Use our script for POSTing commands Script files: write to a file one line at a time

using “echo” Script files usually don’t need extra

permissions Binary files: on certain shells you can echo

arbitrary characters to a file echo -e "\x0B\xAD\xC0\xDE\x0B\xAD\xC0\xDE\

x0B\xAD\xC0\xDE" > file

Uploading Files

We’d also like to upload files to the server FTP, NFS, NetBIOs aren’t good to use for obvious

reasons Create a file uploader script in your favorite

language Get it on the server the same way as the web

based command prompt

Now what?

Now we can do all sorts of fun stuff!!! Find source code of web apps Find server configuration files Try to perform privilege elevation attacks

that work locally Screw with the database

Hacking IIS5(windows 2000 server) via unicode bug

Cari file html disimpan

Hacking IIS5(windows 2000 server) via unicode bug

Jalankan cmd.exe

Hacking IIS5(windows 2000 server) via unicode bug

Copy file cmd.exe

Hacking IIS5(windows 2000 server) via unicode bug

IT’S SHOW TIME ..

Hacking IIS5(windows 2000 server) via unicode bug

Deface time

SQL Injection

Hackers typically test for SQL injection vulnerabilities by sending the application input that would cause the server to generate an invalid SQL query.

If the server then returns an error message to the client, the attacker will attempt to reverse-engineer portions of the original SQL query using information gained from these error messages.

The typical administrative safeguard is simply to prohibit the display of database server error messages. Regrettably, that’s not sufficient.

If your application does not return error messages, it may still be susceptible to “blind” SQL injection attacks.

Solution

To secure an application against SQL injection, developers must never allow client supplied data to modify the syntax of SQL statements.

In fact, the best protection is to isolate the web application from SQL altogether.

All SQL statements required by the application should be in stored procedures and kept on the database server.

The application should execute the stored procedures using a safe interface such as JDBC’s CallableStatement or ADO’s Command Object.

If arbitrary statements must be used, use PreparedStatements.

Both PreparedStatements and stored procedures compile the SQL statement before the user input is added, making it impossible for user input to modify the actual SQL statement.

Web Application Vulnerability

Application Design Application Implementation Application Deployment Infrastructure Configuration

Application Design

Vulnerability in the stage of application design

Examples: Weak password (policy) No protection (Encryption) on confidential

data Bad choice on using cryptography Weak authentication/authorization mechanism

Application Deployment

Transition of application state (e.g. from test to production) Did not strip out information

Test/Guest accounts Test information Debug configuration Account/Password information

No audit/test before deployment Deployed bugged version

Expose test environment

Find Web Application Vulnerability

How Do You Find Web Application Vulnerability Today?

Raise Your Hand If You Use Automatic Tool!

Raise Your Hand If You Use Manual Test!

Raise Your Hand If You Don’t Use Any of Them!

Assesment Plan

Do You know what will be tested? Do you have control to add or delete the

test? Who is making the plan? What is the methodology? What is the knowledge base?

Accuracy

How accurate is the result? Can any tool identify “ANY” of the case study

we are going to talk about?

Is it confused by your customized error page?

Can it login into your HTML Form-based authentication application?

Can it assess authorization or access control problem?

Accountability & Traceability

Can you verify or reproduce any single vulnerability found?

How easy/hard would that be? Can you identify what is the risk brought to

you by the vulnerability? Can you change/define how the risk is

calculated?