Doc #66564 [Asn->Csd]: crypt() seems to silently discard input after a certain length

Edit report at https://bugs.php.net/bug.php?id=66564&edit=1 ID: 66564 Updated by: googleguy@php.net Reported by: ss23 at ss23 dot geek dot nz Summary: crypt() seems to silently discard input after a certain length -Status: Assigned +Status: Closed Type: Documentation Problem Package: Documentation problem PHP Version: Irrelevant Assigned To: googleguy Block user comment: N Private report: N New Comment: This bug has been fixed in the documentation's XML sources. Since the online and downloadable versions of the documentation need some time to get updated, we would like to ask you to be a bit patient. Thank you for the report, and for helping us make our documentation better. Previous Comments: ------------------------------------------------------------------------ [2014-01-28 13:10:22] googleguy@php.net Automatic comment from SVN on behalf of googleguy Revision: http://svn.php.net/viewvc/?view=revision&revision=332747 Log: Add cautionary statement about truncation for crypt and password_hash using BCRYPT. Fixes Bug #66564. This includes a cautionary statement that the CRYPT_BLOWFISH algorithm in crypt/password_hash functions will truncate the input string at a maxmimum length of 72 characters. Typically not a problem for the average use case since this is only likely used for passwords and assuming each hash has a unique salt. However, it's still a good idea to document this behavior so that users are aware of the side effect. ------------------------------------------------------------------------ [2014-01-28 10:29:09] googleguy@php.net It seems that input from the $str argument of crypt will truncate at exactly 73 characters when using CRYPT_BLOWFISH $salt. password_hash, is obviously also affected in the same way. Tested on release bracnhes of 5.3.0 through 5.6.0alpha1 with 3v4l.org and independently on my own system. Reproducible results for crypt: http://3v4l.org/3icqi Reproducible results for password_hash: http://3v4l.org/GbOo4 Reference to php-src http://lxr.php.net/xref/PHP_5_5/ext/standard/crypt_blowfish.c#819 Will update the documentation to reflect this limit more clearly in the documentation since it is defined behavior. ------------------------------------------------------------------------ [2014-01-24 00:07:51] googleguy@php.net Will assign to myself for now. ------------------------------------------------------------------------ [2014-01-24 00:06:21] ss23 at ss23 dot geek dot nz Description: ------------ It seems there is a limit to the input length of the password/str parameter to crypt(), however this is not documented anywhere. This has profound security implications, and all users should be aware of the issue. My preference would be a warning/notice triggered when you exceed the length, as well as documentation on this. Test script: --------------- $long = str_repeat('a', 100); var_dump(crypt($long . "1", '$2y$04$saltysaltysaltysaltytt')); var_dump(crypt($long . "2", '$2y$04$saltysaltysaltysaltytt')); var_dump(crypt($long . "12", '$2y$04$saltysaltysaltysaltytt')); Expected result: ---------------- A different hash in each case Actual result: -------------- string(60) "$2y$04$saltysaltysaltysaltyte9usMwh4/IIx0al18sl5oEFVM2Z/XJ7q" string(60) "$2y$04$saltysaltysaltysaltyte9usMwh4/IIx0al18sl5oEFVM2Z/XJ7q" string(60) "$2y$04$saltysaltysaltysaltyte9usMwh4/IIx0al18sl5oEFVM2Z/XJ7q" ------------------------------------------------------------------------ -- Edit this bug report at https://bugs.php.net/bug.php?id=66564&edit=1