- Security Testing Tutorial
- Security Testing - Home
- Security Testing - Overview
- Security Testing - Process
- Security Testing - Malicious Software
- HTTP Protocol Basics
- HTTPS Protocol Basics
- Encoding and Decoding
- Security Testing - Cryptography
- Security Testing - Same Origin Policy
- Security Testing - Cookies
- Hacking Web Applications
- Security Testing - Injection
- Testing Broken Authentication
- Testing Cross Site Scripting
- Insecure Direct Object Reference
- Testing Security Misconfiguration
- Testing Sensitive Data Exposure
- Missing Function Level Access Control
- Cross Site Request Forgery
- Components with Vulnerabilities
- Unvalidated Redirects and Forwards
- Security Testing - Ajax Security
- Testing Security - Web Service
- Security Testing - Buffer Overflows
- Security Testing - Denial of Service
- Testing Malicious File Execution
- Security Testing - Automation Tools
- Security Testing Useful Resources
- Security Testing - Quick Guide
- Security Testing - Useful Resources
- Security Testing - Discussion
- Selected Reading
- UPSC IAS Exams Notes
- Developer's Best Practices
- Questions and Answers
- Effective Resume Writing
- HR Interview Questions
- Computer Glossary
- Who is Who
Security Testing - HTTP Messages
HTTP is based on client-server architecture model and a stateless request/response protocol that operates by exchanging messages across a reliable TCP/IP connection.
An HTTP "client" is a program (Web browser or any other client) that establishes a connection to a server for the purpose of sending one or more HTTP request messages. An HTTP "server" is a program (generally a web server like Apache Web Server or Internet Information Services IIS etc.) that accepts connections in order to serve HTTP requests by sending HTTP response messages.
HTTP makes use of the Uniform Resource Identifier (URI) to identify a given resource and to establish a connection. Once connection is established, HTTP messages are passed in a format similar to that used by Internet mail [RFC5322] and the Multipurpose Internet Mail Extensions (MIME) [RFC2045]. These messages are consisted of requests from client to server and responses from server to client which will have following format −
HTTP-message = <Request> | <Response> ; HTTP/1.1 messages
HTTP request and HTTP response use a generic message format of RFC 822 for transferring the required data. This generic message format consists of following four items −
Zero or more header fields followed by CRLF
An empty line (i.e., a line with nothing preceding the CRLF) indicating the end of the header fields
Optionally a message-body
Following section will explain each of the entities used in HTTP message.
A start-line will have the following generic syntax −
start-line = Request-Line | Status-Line
We will discuss Request-Line and Status-Line while discussing HTTP Request and HTTP Response messages respectively. For now let's see the examples of start line in case of request and response −
GET /hello.htm HTTP/1.1 (This is Request-Line sent by the client) HTTP/1.1 200 OK (This is Status-Line sent by the server)
HTTP header fields provide required information about the request or response, or about the object sent in the message body. There are following four types of HTTP message headers −
General-header − These header fields have general applicability for both request and response messages.
Request-header − These header fields are applicability only for request messages.
Response-header − These header fields are applicability only for response messages.
Entity-header − These header fields define meta information about the entity-body or, if no body is present.
All the above-mentioned headers follow the same generic format and each of the header field consists of a name followed by a colon (:) and the field value as follows −
message-header = field-name ":" [ field-value ]
Following are the examples of various header fields −
User-Agent: curl/7.16.3 libcurl/7.16.3 OpenSSL/0.9.7l zlib/1.2.3 Host: www.example.com Accept-Language: en, mi Date: Mon, 27 Jul 2009 12:28:53 GMT Server: Apache Last-Modified: Wed, 22 Jul 2009 19:15:56 GMT ETag: "34aa387-d-1568eb00" Accept-Ranges: bytes Content-Length: 51 Vary: Accept-Encoding Content-Type: text/plain
The message body part is optional for an HTTP message but if it is available then it is used to carry the entity-body associated with the request or response. If entity body is associated then usually Content-Type and Content-Length headers lines specify the nature of the body associated.
A message body is the one which carries actual HTTP request data (including form data and uploaded etc.) and HTTP response data from the server (including files, images, etc.). Following is a simple content of a message body −
<html> <body> <h1>Hello, World!</h1> </body> </html>