Application Security: Web service and E-Mail (April 11, 2011) © Abdou Illia – Spring 2011

Learning Objectives Discuss general Application security Discuss Webservice/E-Commerce security Discuss E-Mail security

General Applications Security Issues

Applications Security Issues Few Operating Systems But Many Applications Because OS are harden, most attacks target applications installed on servers. Many applications run with administrative or super user (root) privileges Securing applications is challenging Buffer Overflow Attacks Most widespread vulnerabilities in application programs 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

Buffer Overflow The overflowsample function: Declares a buffer array capable of holding eight ASCII characters Places the buffer in an initialization loop The loop force-feeds 15 “x” into the buffer array through programming error Only 8 “x” could fit Nine “x” must spill over A function written in C void overflowsample (void) { char buffer1[8]; int I; For (I = 0; I < 16; I++) { buffer1[I] = ‘x’; } } When the program is run… What will be the value of buffer1[3]? _____, Buffer1[15]? _____ What would happen? The part of the function’s code designed to check the bounds of the array will prevent any error from happening. The program will generate an error and terminate.

Buffer Overflow Int main() { char name[8]; char etc_passwd[8]; char password[8]; // retrieve the user information printf (“Enter your name:”); gets (name); etc_passwd = get_password (name); printf (“Enter your password:”); gets (password); printf (“Your name and password entries were %s and %s.”, name, password); printf (“The password for %s In the /etc/shadow file Is %s”’ name, etc_passwd); // call procedure to check login authorization authenticate (password, etc_password); return 0; } void authenticate (char * string1, char string2) { char buffer1[8]; char buffer2[8]; strcpy (buffer1, string1); strcpy (buffer2, string2); if (strcmp (buffer1, buffer2) == 0 permit(); }

Buffer Overflow

Stack Entry and Buffer Overflow Stack entry: data buffer & Return address registry 2. Add Data to Buffer 1. Write Return Address Return Address 5. Start of Attacker data Data Buffer 3. Direction of Data Writing 4. Overwrite Return 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/

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 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 9 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)

General Application Security Minimize number of applications Fewer applications on a computer, fewer attack opportunities Use security baselines for installation Security baselines improve security Add application layer authentication Important for sensitive applications Could be password-based Implement cryptographic systems

Web service security

Webservice Versus E-Commerce Webservice includes basic functionalities for Retrieval of static files Creation of dynamic webpages E-Commerce requires additional software for Online catalogs Shopping carts Connection to back-end database Connection to organizations for payments, etc. E-Commerce Software Webserver Software (IIS, Apache, etc.) Subsidiary E-Commerce Software Component (DHTML, etc.) Custom Programs (in client-side scripting)

Webservice Versus E-Commerce 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

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

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

Traversal Attack Normally, paths start at the WWW root directory Adding ../ might take the attacker up a level, out of the WWW root box If attacker traverses to Command Prompt directory in Windows 2000 or NT, can execute any command with system privileges

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 Hex Null NUL Ctrl @ 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

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

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

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.

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.

IIS IPP Buffer Overflow (cont.) Source: http://puna.net.nz/archives/Hacking/David_Sheridan_GCIH.doc

HTTP Requests GET By far the most common method used HTTP defines 8 methods (or "verbs") indicating the desired action to be performed on a resource GET HEAD POST PUT DELETE TRACE OPTIONS CONNECT HTTP Requests GET By far the most common method used Requests data from specified host Example of request with GET method GET /index.html HTTP/1.1 Host: www.example.com

HTTP Requests HEAD Asks for response identical to a GET request without response body Useful for retrieving meta-information written in response headers without having to transport the entire content POST Submits data to be processed (e.g. from an HTML form) to a server The data is included in the body of the request PUT Uploads data to the server DELETE Delete specified file TRACE Echoes back the received request so that a client can see what intermediate servers are adding or changing in the request OPTIONS Returns HTTP methods supported by the server. This can be used to check the functionality of a web server.

Browser Attacks Malicious links attack.txt.exe seems to be attack.txt 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

Browser Attacks (Cont.) Common Attacks Redirection to unwanted webpage Scripts might change the registry, home page Some scripts might “trojanize” when 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)

E-Mail

E-Mail Protocols SMTP To Send SMTP To Send Receiver’s Mail Server Sender’s Mail Server Simple Mail Transfer Protocol (SMTP) to transmit mail in real time to a user’s mail server or between mail servers Sender-initiated Sending E-Mail Client Receiving E-Mail Client

E-Mail protocols POP or IMAP To Receive Receiver’s Mail Sender’s Mail Server Sender’s Mail Server POP or IMAP to download mail to receiver when the receiver capable of downloading mail. Receiver-initiated Sending E-Mail Client Receiving E-Mail Client Internet Message Application Program (IMAP): More powerful, can manage messages on the receiver’s mail server, less widely used Post Office Protocol (POP): Simple, loosing grounds to IMAP

E-Mail Standards Receiver’s Mail Server Sender’s Mail Server Message Body Format Standard Message RFC 822 or 2822 HTML body UNICODE Sending E-Mail Client Receiving E-Mail Client RFC 822 (English ASCII code) or 2822: for all-text bodies UNICODE: for all languages HTML body: for fancy text and graphics

E-Mail Security E-Mail Encryption Not widely used because of lack of clear standards IETF has not been able to settle upon a single standard because of in-fighting Three standards are used in corporations TLS S/MIME PGP

E-Mail Security E-Mail Encryption TLS only requires a digital certificate for servers S/MIME requires a PKI for digital certificates PGP uses trust among circles of friends: If A trusts B, and B trusts C, A may trust C’s list of public keys Dangerous: Misplaced trust can spread bogus key/name pairs widely