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  1. Application Security: General apps &Web service (April 11, 2012) © Abdou Illia – Spring 2012

  2. Learning Objectives • Discuss general Application security • Discuss Webservice/E-Commerce security • [Discuss E-Mail security]

  3. General Applications Security Issues

  4. Web service software (IIS, Apache, ...)Web browser, Photo editors, Movie maker, Productivity software, etc. Client & server application programs Operating System Computer Hardware Applications Security Issues • Few Operating Systems But Many Applications • Because OS are harden, most attacks target applications installed on servers. • Most applications run with administrative or super user (root) privileges • Securing applications is challenging

  5. Which of the following is true about Application Security? If a server application (or service) is no longer needed, it should be turned off Fewer applications on a computer, fewer attack opportunities Use good security baselines to install and configure apps Do not install application centrally using group policies Add application layer authentication by requiring users to provide credentials to run application programs Implement cryptographic authentication for sensitive apps If a server application (or service) is no longer needed, it should be removed Do not turn on each applications’ automatic update checking 5

  6. Applications and Buffer Overflow Buffer Overflow is the biggest issue in application coding Buffer overflow leads to Buffer Overflow Attacks Buffers are RAM areas where data is stored temporarily If an attacker sends more data than the programmer had allocated to a buffer, a buffer might overflow, overwriting an adjacent section of RAM RAM Buffer1 Buffer2 Buffer3 Buffer4 Buffer5 Buffer6 Buffer7 6

  7. Buffer Overflow Attack Occurs when ill-written programs allow data destined to a memory buffer to overwrite instructions in adjacent memory register that contains instructions. If the data contains malware, the malware could run and creates a DoS Example of input data: ABCDEF LET JOHN IN WITHOUT PASSWORD 7

  8. Stack entry: data buffer & Return address registry Stack Entry and Buffer Overflow 2. Add Data to Buffer 1. Write Return Address Return Address 5. Start of Attacker data Data Buffer 4. Overwrite Return Address 3. Direction of Data Writing • When a program must put one subprogram on hold to call another, it writes the return address in RAM areas called stack entries • The called subprogram may add data to the buffer to the point it overwrites the return address • If the added buffer data is Attack code, this will be a buffer overflow attack

  9. Preventing Buffer Overflow • Use Language tools that provide automatic bounds checking such as Perl, Python, and Java instead lower level language (C, C++, Assembly, etc). • However, this is usually not possible or practical because almost all modern OS are written in the C language. • Eliminate The Use Of Flawed Library Functions like gets(), strcpy, and strcmp that fail to check the length or bounds of their arguments. • Design And Build Security Within Code • Use Source Code Scanning Tools. • Example: PurifyPlus Software Suite can perform a dynamic analysis of Java, C, or C++ source code. For instance, this simple change informs strcpy() that it only has an eight byte destination buffer and that it must discontinue raw copy at eight bytes. // replace le following line Strcpy (buffer2, strng2); // by Strcpy (buffer2, string2, 8)

  10. Web service security

  11. Webservice & E-Commerce apps • Web applications could be the target of many types of attacks like: • Directory browsing • Traversal attacks • Web defacement • Using HTTP proxy to manipulate interaction between client and server • IIS IPP Buffer Overflow • Browser attacks • Time configuration

  12. Web sites’ directory browsing • Web server with Directory Browsing disabled • User cannot get access to list of files in the directory by knowing or guessing directory names

  13. Web site with directory browsing • Web server with Directory Browsing enabled • User can get access to the list of files in the directory by knowing or guessing directory names

  14. Traversal Attack • Normally, paths start at the WWW root directory • Adding ../ (Windows) or ..\ (Unix) in an HTTP request might take the attacker up a level, out of the WWW root directory. Example: ../../ Example: • If attacker traverses to Command Prompt directory in Windows 2000 or NT, he can execute any command with system privileges

  15. Traversal Attacks (Cont.) • Preventing traversal attacks • Companies filter out ../ and ..\ using URL scanning software • Attackers respond with hexadecimal and UNICODE representations for ../ and ..\

  16. Website defacement • Taking over a web server and replacing normal web pages by hacker-produced pages • Effect could last because ISP cache of popular web sites • Example of recent website defacements • ATTRITION Web Page Hack Mirror: • Zone-H web site for most recent attacks: Check Onhold and Archive

  17. Manipulating HTTP requests • Attackers use proxies to manipulate communications between browsers and web servers • Example using Webscarab

  18. IIS IPP Buffer Overflow • The Internet Printing Protocol (IPP) service included in IIS 5.0 and earlier versions is vulnerable to buffer overflow attacks • The jill.c program was developed to launch the attack using: GET NULL.printer HTTP/1.0 Host: 420-byte jill.c code to launch the command shell • IIS server responds launching the command shell (C:\WINNT\SYSTEM32\>) giving the attacker SYSTEM privileges.

  19. IIS IPP Buffer Overflow (cont.) • Link to jill.c code • Code compilable using gcc jill.c –o jill on Linux • Precompiled version (jill-win32.c) and executable (jill-win32.exe) available at • newfiles/jill-win32.exe. This executable file is ready to run on a Windows machine.

  20. IIS IPP Buffer Overflow (cont.) • Source:

  21. Browser Attacks • Malicious links • User must click on them to execute (but not always) • Common extensions are hidden by default in some operating systems. • attack.txt.exe seems to be attack.txt

  22. Browser Attacks (Cont.) • Common Attacks • Redirection to unwanted webpage • Scripts might change the registry, home page • Some scripts might “trojanize” your DNS error-handling routine when you mistype a URL • Pop-up windows • Web bugs; i.e. links that are nearly invisible, can be used to track users at a website • Domain names that are common misspellings of popular domain names •, (a porn site)