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https://issues.apache.org/jira/browse/OAK-634?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13580830#comment-13580830
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Thomas Mueller commented on OAK-634:
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> On a successful login the record should be updated to contain a password hash
> with just one iteration
I agree that a repeated login should be fast. So your solution would be a
simple LRU cache for known-good passwords, but the key is one iteration of the
password (not the plain text) to avoid keeping the password in memory? Yes I
think that would make sense.
> The record should also keep track of unsuccessful login attempts
Yes, that would be nice, but the question is where / how exactly to limit.
> though instead of SHA-256 we should be using something like bcrypt
I agree using our own algorithm (as we do now) should be avoided. I would
prefer PBKDF2 over bcrypt, because AFAIK PBKDF2 is the industry standard. I
recently implemented PBKDF2 for SHA-256, the source code is at
http://code.google.com/p/h2database/source/browse/trunk/h2/src/main/org/h2/security/SHA256.java#145
(I also used a low number of iterations actually, but the reason is different
- the problem is that calculating a hash is slow on Android). There are also
test cases, test vectors are here:
http://stackoverflow.com/questions/5130513/pbkdf2-hmac-sha2-test-vectors
> PasswordUtility.isSame() performance bottleneck
> -----------------------------------------------
>
> Key: OAK-634
> URL: https://issues.apache.org/jira/browse/OAK-634
> Project: Jackrabbit Oak
> Issue Type: Bug
> Components: core
> Reporter: Jukka Zitting
> Labels: performance
>
> The default 1000 SHA-256 iterations used for password hashes are seriously
> impacting the performance of login() calls. Here's a performance report of
> the number of milliseconds that a successful login takes with Jackrabbit 2.x
> and Oak (with an in-memory MK):
> {noformat}
> # Login min 10% 50% 90% max
> Jackrabbit 560 570 577 704 1522
> Oak-Memory 2537 2586 2630 2811 2916
> {noformat}
> Over 50% of that time is spent doing hash iterations in
> {{PasswordUtility.isSame()}}. This is a problem for two main reasons:
> # It severely drags down performance of acquiring a new session; something
> which should be essentially free.
> # It opens the denial of service attack vector of just bombarding a system
> with login attempts, which would cause CPU usage to spike.
> Iterating a password hash is a good idea for preventing offline attacks
> against a stolen password database (though instead of SHA-256 we should be
> using something like bcrypt that's explicitly designed and analyzed for this
> purpose), but the current implementation doesn't make much sense in a
> scenario like ours where we can expect dozens or hundreds of logins per
> second even in normal non-peak use cases. Password iteration makes more sense
> in use cases where logins are infrequent (e.g. once a day per user) and
> persisted through something like a session key.
> So, assuming we want to keep the cost of an offline attack high, here's what
> I suggest we do for password-based logins:
> * Switch to bcrypt or a similar password hashing algorithm if possible.
> * For each active user in the system, keep an in-memory record to speed up
> login calls.
> ** On a successful login the record should be updated to contain a password
> hash with just one iteration (calculated from the plain text password
> provided in the successful login). Use this instead of the in-repository
> password hash for authenticating further login attempts.
> ** The record should also keep track of unsuccessful login attempts and limit
> them to at most N attempts per minute to prevent DOS attacks.
> The result of such in-memory record keeping should be to massively speed up
> normal logins (point 1 above) and also to cap the CPU use of the potential
> DOS attack (point 2) to O(N*K) cycles per minute, with K being the total
> number of users in the system.
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