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WEB SYSTEM. Components of a Generic Web Application System. URL Mappings to the Web Application 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.)

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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.


  • 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?


  • 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?

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