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From: "Simon J Oliver (sjoliver)" 
<sjoli...@memphis.edu<mailto:sjoli...@memphis.edu>>
Date: February 20, 2013, 8:23:33 PM CST
To: Ken Anderson <kenli...@anderhome.com<mailto:kenli...@anderhome.com>>
Subject: Re: Storing a user in a cookie

Yes I think OAuth could potentially work, although you'd probably want some 
sort of local session management /caching anyway to avoid the need to validate 
every request with the identity provider. OAuth has the advantage at least over 
Pascal's original scheme that it provides an form of expiry/invalidation 
mechanism that allows a token to be repudiated if needed.

Depending on how long you want the tokens to live and/or how sensitive the data 
is, you'd probably want to ensure that your app was served solely over SSH to 
minimize the risk of token theft.

It really all depends on you, your users and your data... I can't imagine many 
circumstances where just re-locking the door to fix a confidentiality/integrity 
 breach after the fact is a 'good enough' solution to keeping an app secure 
(especially where the breach can have happened through no identifiable fault of 
the user, as in the case of tokens sniffed off the network) but if that works 
for your scenario, then that's great. :-)

Simon

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On Feb 20, 2013, at 11:36 AM, "Ken Anderson" 
<kenli...@anderhome.com<mailto:kenli...@anderhome.com>> wrote:

Doesn't OAUTH do exactly what you're asking for?  For users that use one of my 
iOS apps (RailTime), we get an OAUTH secret from Twitter that's unique to us.  
The user can always log onto Twitter and disable our OAUTH secret, but 
otherwise it lasts forever.

If a user complains that they're seeing strange behavior on their account, 
revoke the secret and issue another one.

Ken


On Feb 20, 2013, at 10:24 AM, Simon J Oliver (sjoliver) 
<sjoli...@memphis.edu<mailto:sjoli...@memphis.edu>> wrote:

I think that first you have to think seriously if you really want to do this. 
There are two problems to guard against - making up tokens, and re-using other 
people's. Encryption might fix the first, but not the second.

If you do REALLY want to do it,  you have to basically emulate a session ID, 
and store that in the database or in a file or something, and then look it up - 
with some sort of expiry period built in. You can generate the tokens with a 
hash function, it doesn't need to be reversible encryption.

If there is no expiry mechanism then anyone who has access to your token (e.g., 
from sniffing network traffic) from the cookie can masquerade as that user at 
any time (years later even), bypassing authentication, and you have no way to 
stop them short of invalidating the user id.

Session id's are always a bit of a trade off security wise, but you need some 
way to check that the return of the user is plausible and not just accept any 
connection that knows the magic words.

Simon
CISSP-ISSAP, ISSMP, GWAPT, OSWP

Sent from my iPhone

On Feb 20, 2013, at 11:08 AM, "Jesse Tayler" 
<jtay...@oeinc.com<mailto:jtay...@oeinc.com>> wrote:

you're only going to compare one resulted cypher to another resulted cypher you 
have stored -- knowing they calculate to the same result and are the 
same/correct is enough to ensure people haven't just made up a cookie and you'd 
never reveal a cookie that would be useful.


On Feb 20, 2013, at 12:02 PM, Pascal Robert 
<prob...@macti.ca<mailto:prob...@macti.ca>> wrote:

What would you use for storing details about an user in a cookie for stateless 
apps (e.g., in a "keep me logged" situation)? I see two solutions:

- Using BlowFish to encrypt the username in the cookie, and to decrypt the 
value of the cookie to see who is the user;

- Encrypting the username with BCrypt, storing the encrypted username in the 
database and in the cookie, and doing a comparison.

Opinions? The only problem I see with the first one is that if someone find the 
cipher key, you're toast, but at the same time, if they find it, it's probably 
because it was stored in the file system or in a SCM, so if they found it, you 
will probably have other problems too.


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