How do I generate a random session ID?
The session ID is generated using the Random Number Generator (RNG) cryptographic provider. The service provider returns a sequence of 15 randomly generated numbers (15 bytes x 8 bit = 120 bits). The array of random numbers is then mapped to valid URL characters and returned as a string.
What is a secure way to store a session ID?
1 Answer
- ensure you are using a “secure enough” random generator to build the token.
- make sure the transmission of the token is as secure as possible against eavesdropping or client-side theft (e.g. use SSL, httponly and secure cookie flags)
Where should we store session identifiers in an application?
The session ID is stored inside the server, it is assigned to a specific user for the duration of that user’s visit (session). The session ID can be stored as a cookie, form field, or URL.
How often should new session IDs be generated?
E.g. Regenerate the session ID every 15 minutes for security sensitive content. Even in the case that a session ID is stolen, both the legitimate user’s and the attacker’s session will expire. In other words access by the user or the attacker will generate an obsolete session access error.
What happens if session ID is not random?
If the attacker determines a valid session token for another user, then it may be possible to view, modify, or delete arbitrary users’ data without having to guess the victim’s username or password.
What is session ID randomness?
A session ID is usually a randomly generated string to decrease the probability of obtaining a valid one by means of a brute-force search. Many servers perform additional verification of the client, in case the attacker has obtained the session ID.
What is the typical approach to making a session identifier?
A session ID is a unique number that a Web site’s server assigns a specific user for the duration of that user’s visit (session). The session ID can be stored as a cookie, form field, or URL (Uniform Resource Locator). Some Web servers generate session IDs by simply incrementing static numbers.
What is session ID entropy?
Session ID Entropy The session ID must be unpredictable (random enough) to prevent guessing attacks, where an attacker is able to guess or predict the ID of a valid session through statistical analysis techniques. For this purpose, a good CSPRNG (Cryptographically Secure Pseudorandom Number Generator) must be used.
What is the typical session identifier?
What are session related vulnerabilities?
Session Fixation is an attack that permits an attacker to hijack a valid user session. The attack explores a limitation in the way the web application manages the session ID, more specifically the vulnerable web application.
What do you mean by session hijacking?
A session hijacking attack happens when an attacker takes over your internet session — for instance, while you’re checking your credit card balance, paying your bills, or shopping at an online store. Session hijackers usually target browser or web application sessions.
What does it mean when session IDs are random?
1. Random session Ids Random session Id’s have no meaning by virtue of being completely random. The server sends them to the client and stores them in a database along with the the user information. If session Id’s are random numbers, how do we ensure that they cannot be guessed or predicted by hackers?
What’s the best way to generate a session ID?
Most languages have pseudo random numbers generators (PRNGs) that generate ‘cryptographically secure’ random numbers that have entropy. As an example, Tomcat uses SHA1 PRNG to generate a random number and hash it with MD5 (see warning below) to create session Id’s.
How are session IDs stored in the store?
The session Id consists of both a random number and a hash combining some properties of the user such as the username and IP address. sessionId = SHA2(userId + ipAddr) + prngRandomNumber The resulting session Id is stored in the session store and looked up for each request.
What should the entropy of a session ID be?
In Cryptography theory, entropy is the measure of uncertainty associated with a random number. Session Id’s should have very high entropy to protect against attacks. OWASP suggests at least 64 bits of entropy.