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-Way Web Hack We need two things to make an effective attack: Interactive terminal access Ability to transfer files
Invoking the Command Interpreter, 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 Command Prompt 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
Installing the Web Based Command 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\x C0\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 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.
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?
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