[PHPBB3-11343] Loose string comparison during new password activation Created: 25/Jan/13  Updated: 22/Jan/17  Resolved: 27/Jan/13

Status: Closed
Project: phpBB3
Component/s: User Control Panel (UCP)
Affects Version/s: 3.0.11
Fix Version/s: 3.0.12-RC1

Type: Bug Priority: Major
Reporter: David King Assignee: Andreas Fischer
Resolution: Fixed Votes: 0
Labels: None

Issue Links:
blocks PHPBB3-11327 Forgot Password should link to a form... Patch Awaiting Review
GitHub Pull Request URL: https://github.com/phpbb/phpbb3/pull/1219


Although request_var() takes care of casting user input to the appropriate type, when comparing strings in a security context, it is required to use strict comparison (===). This is because e.g. "10" == "1e1" evaluates to true which might weaken security properties (e.g. when comparing to a random string).

Comment by EXreaction [X] (Inactive) [ 25/Jan/13 ]

Was this changed for 3.1-dev then? In phpbb_check_password in 3.1-dev I have:

return (_hash_crypt_private($password, $hash, $itoa64) === $hash) ? true : false;

Comment by Andreas Fischer [ 25/Jan/13 ]

I don't understand your question.

Comment by Andreas Fischer [ 25/Jan/13 ]

To clearify: This is about uses such as

$user_row['user_actkey'] != $key
Comment by David King [ 25/Jan/13 ]

Nathan, this issue is specifically tied to this topic: https://www.phpbb.com/community/viewtopic.php?f=44&t=2169160 and is present in both olympus and develop.

EDIT: To clarify, the "vulnerability" is very weak. Basically, it allows an attacker to, with a very low likelihood, use 1 or 0 as the activation key for resetting a user's password because some strings can be evaluated as numbers using loose comparison (==). This ultimately can lock a user out of their account by changing their password to a temporary one, but in the end, the user will still have the temporary password in their email, which the attacker cannot access. As such, this does not result in the attacker being able to gain the user's account, unless the attacker is able to access the user's email, in which case he would not need to use this "vulnerability" anyway, as both the activation key and the temporary password are sent in the email. It is more of an annoyance than a vulnerability. However, it is something we should fix.

Comment by Andreas Fischer [ 25/Jan/13 ]

This ticket should obviously be about all "loose string comparisons in a security context", not just the new password activation one. $user_row['user_actkey'] != $key however seems to be the only occurance of this issue so far.

Also, FYI: This ticket will be made public sooner or later.

Comment by EXreaction [X] (Inactive) [ 27/Jan/13 ]

Oops, I must have read this too fast on my phone and thought it was about password comparison, not during password activation.

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