Bug #80744 [Opn->Nab]: password_verify fail to verify bcrypt hashes with cost below 4

Edit report at https://bugs.php.net/bug.php?id=80744&edit=1 ID: 80744 Updated by: nikic@php.net Reported by: divinity76 at gmail dot com Summary: password_verify fail to verify bcrypt hashes with cost below 4 -Status: Open +Status: Not a bug Type: Bug Package: *Encryption and hash functions PHP Version: 8.0.2 Block user comment: N Private report: N New Comment: No, the self-test is performed with a reduced minimum cost threshold (1 instead of 16). Previous Comments: ------------------------------------------------------------------------ [2021-02-13 14:03:41] divinity76 at gmail dot com @allenjb interesting, does that mean that the self-test code on line 4 here should be increased from cost 0 to cost 4? since it's not actually testing a valid bcrypt hash in it's current form? https://github.com/php/php-src/blob/07fa13088e1349f4b5a044faeee57f2b34f6b6e4/ext/standard/crypt_blowfish.c#L814 ------------------------------------------------------------------------ [2021-02-13 13:58:48] php-bugs at allenjb dot me dot uk I would posit that this response is correct: The original OpenBSD implementation[0], which is the closest I believe exists to a specification for bcrypt, specifies a minimum number of 16 (2^4) rounds (BCRYPT_MINROUNDS in the OpenBSD source). I would guess this is because lower values are likely vulnerable to the speed of brute-force cracking even at the time the algorithm was first proposed (and we've had over 2 decades of advances since then). Following this "reference implementation", no library should ever generate a hash with a cost value of less than 4, and any such hashes that exist are therefore invalid. [0] https://cvsweb.openbsd.org/cgi-bin/cvsweb/src/lib/libc/crypt/bcrypt.c?rev=1.1&content-type=text/x-cvsweb-markup ------------------------------------------------------------------------ [2021-02-13 13:11:08] divinity76 at gmail dot com Description: ------------ password_verify fail to verify bcrypt hashes with cost below 4 Test script: --------------- <?php var_dump(password_verify("",'$2a$03$AAAAAAAAAAAAAAAAAAAAA.TCFhOtNOtk2Oeef1z4xP561tW1AQOMW')); Expected result: ---------------- bool(true) Actual result: -------------- bool(false) ------------------------------------------------------------------------ -- Edit this bug report at https://bugs.php.net/bug.php?id=80744&edit=1