Authentication Cheat Sheet
- 1 Introduction
- 2 Authentication General Guidelines
- 2.1 Implement Proper Password Strength Controls
- 2.2 Implement Secure Password Recovery Mechanism
- 2.3 Utilize Multi-Factor Authentication
- 2.4 Authentication and Error Messages
- 2.5 Transmit Passwords Only Over TLS
- 2.6 Implement Account Lockout
- 3 Session Management General Guidelines
- 4 References
- 5 Authors and Primary Editors
Authentication is the process of verification that an individual or an entity is who it claims to be. Authentication is commonly performed by submitting a user name or ID and one or more items of private information that only a given user should know.
Session Management is a process by which a server maintains the state of an entity interacting with it. This is required for a server to remember how to react to subsiquent requests throughout a transaction. Sessions are maintained on the server by a session identifier which can be passed back and forward between the client and server when mtransmitting and receiving requests. Sessions should be unique per user and computationally very difficult to predict.
For more information on Authentication, please see the OWASP Guide to Authentication page.
Authentication General Guidelines
Implement Proper Password Strength Controls
A key concern when using passwords for authentication is password strength. A "strong" password policy makes it difficult or even improbable for one to guess the password either by using manual or automated means. The following characteristics define strong a strong password:
The longer the password the more combinations possible combinations of characters exist and is hence more difficult to guess.
Important applications: Minimum of 6 characters in length.
Critical applications: Minimum of 8 characters in length. (consider multi-factor authentication)
Highly critical applications: Consider multi-factor authentication
2. Password complexity
Passwords should be checked for the following composition or a variance of such:
- at least: 1 uppercase character (A-Z)
- at least: 1 lowercase character (a-z)
- at least: 1 digit (0-9)
- at least one special character (!"£$%&...)
- a defined minimum length (e.g. 8 chars)
- a defined maximum length (as with all external input)
- no contiguous characters (e.g. 123abcd)
- not more than 2 identical characters in a row (1111)
Implement Secure Password Recovery Mechanism
It is common for an application to have a mechanism that provides a means for a user to gain access to their account in the event they forget their password. Password recovery systems are difficult to secure against abuse, circumvention. The best way is to keep them as simple as possible.
Weaknesses with sectet questions are common;
Weakness may be that the security question is too easy to guess or find an answer to E.g. Car, Date of Birth (DOB), Colour Such question have a a finite sample space and are easily brute forced/guessed.
Delivery Mechanisims / Implementation weakness
Common issues with a reset password delivery are
Email: Setting the email address to that which is not the email address of the user for which the password is to be reset.
- Password Reset Rate
Limiting the rate at which password reset requests are processed in order to limit hijacking and brute force attempts.
Utilize Multi-Factor Authentication
Authentication and Error Messages
Transmit Passwords Only Over TLS
Implement Account Lockout
Session Management General Guidelines
Transmit Session ID's Only Over TLS
Ensure Session ID's are Cryptographically Strong and Random
Implement Idle And Absolute Timeout
Caching & Privacy
OWASP Cheat Sheets Project Homepage
Authors and Primary Editors
Eoin Keary eoinkeary[at]owasp.org