Date: Sun, 27 Mar 2016 06:30:07 +0300 From: Solar Designer <solar@...nwall.com> To: musl@...ts.openwall.com Cc: Timo Teras <timo.teras@....fi> Subject: Re: [PATCH] crypt_blowfish: allow short salt strings On Sun, Mar 27, 2016 at 05:11:21AM +0300, Solar Designer wrote: > There is one maybe-bug seen in your test results: the "*" return on > error. Normally, it would be "*0" or "*1" for crypt_blowfish, and it > would never match the salt input. Rich, did musl retain this behavior? > Where does the bare "*" come from? The concern here is that a "*" might > also be returned when crypt() is called with "*" for the salt input. > Then its output would match what may be a stored hash placeholder, where > "*" means locked account or an error having occurred when the password > was set. We must deny access in such cases, but returning "*" on all > errors would grant access. This could be a musl or PHP security bug, if > it's indeed as bad as it appears from that test. I just discussed this with Rich. Yes, musl's modified crypt_blowfish returns "*" on error. No, this isn't a security bug in musl as a whole, because that code path is not reached when the setting argument is "*" as well. So no match. However, there's risk for code reuse from musl by other projects, and for potential cut-down revisions of musl (with only bcrypt left, invoked unconditionally). So I think a change is needed, either reintroducing the "*0" / "*1" behavior (my preference) or returning NULL (Rich's preference) on error like glibc does (and unfortunately crashing older programs that don't expect this). Alexander
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