PHP’s implementation of crypt_blowfish differs from the upstream Openwall
version by adding a “PHP Hack”, which allows one to cut short the BCrypt salt
by including a `$` character within the characters that represent the salt.
Hashes that are affected by the “PHP Hack” may erroneously validate any
password as valid when used with `password_verify` and when comparing the
return value of `crypt()` against the input.
The PHP Hack exists since the first version of PHP’s own crypt_blowfish
implementation that was added in 1e820eca02.
No clear reason is given for the PHP Hack’s existence. This commit removes it,
because BCrypt hashes containing a `$` character in their salt are not valid
BCrypt hashes.
7882d12ff2