Application Security: General apps &Web service

(April 11, 2012)

© Abdou Illia – Spring 2012

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Learning Objectives

Discuss general Application security Discuss Webservice/E-Commerce security [Discuss E-Mail security]

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General Applications Security Issues

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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

Computer HardwareOperating System

Web service software (IIS, Apache, ...)Web browser, Photo editors, Movie maker,

Productivity software, etc.

Client & server application programs

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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

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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

RAMBuffer1 Buffer2

Buffer7Buffer3 Buffer4 Buffer6Buffer5

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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

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Buffer Instructions

1 2 3 4 5 6

Print

Run Program

Accept input

Buffer Instructions

1 2 3 4 5 6

A B C D E F LET JOHN IN WITHOUT PASSWORD

Run Program

Accept input

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Stack entry: data buffer & Return address registry

Stack Entry and Buffer Overflow

ReturnAddress

1. Write ReturnAddress

2. Add Datato Buffer

Data Buffer5. Start of

Attacker data

3. Direction ofData Writing

4. OverwriteReturn Address

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

http://www.metacafe.com/watch/1452134/buffer_overflow_attacks_explained_with_beer/

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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.

// replace le following line

Strcpy (buffer2, strng2);

// by

Strcpy (buffer2, string2, 8)

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.

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Web service security

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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

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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

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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

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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: http://website.com ../../

Example: http://castle.eiu.edu/~a_illia/BUS3500/Brief/Case1/../

If attacker traverses to Command Prompt directory in Windows 2000 or NT, he can execute any command with system privileges

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Traversal Attacks (Cont.) Preventing traversal attacks

Companies filter out ../ and ..\ using URL scanning software

Attackers respond with hexadecimal and UNICODE representations for ../ and ..\

ASCII Character Chart with Decimal, Binary and Hexadecimal Conversions

Name Character Code Decimal Binary HexNull NUL Ctrl @ 0 00000000 00

Start of Heading SOH Ctrl A 1 00000001 01

Space 32 00100000 20

Exclamation Point ! Shift 1 33 00100010 22

Plus + Shift = 43 00101011 2B

Period . . 46 00101110 2E

Forward Slash / / 47 00101111 2F

Tilde ~ Shift’ 126 01111110 7E

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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:

http://attrition.org/mirror/ Zone-H web site for most recent attacks:

http://www.zone-h.org: Check Onhold and Archive

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Manipulating HTTP requests

Attackers use proxies to manipulate communications between browsers and web servers

Example using Webscarab

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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.

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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 ftp://ftp.technotronic.com/

newfiles/jill-win32.exe. This executable file is ready to run on a Windows machine.

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IIS IPP Buffer Overflow (cont.)

Source: http://puna.net.nz/archives/Hacking/David_Sheridan_GCIH.doc

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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

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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

Microsoff.com, www.whitehouse.com (a porn site)