bcrypt password hashing for your software and your servers
Please note that password hashing is often wrongly referred to as
"password encryption".
Hashing is a more appropriate term since encryption is something that is
supposed to be easily reversible.
This is an implementation of bcrypt, a password hashing method based on the
Blowfish
block cipher, provided via the crypt(3) and a reentrant interface.
It is fully compatible with OpenBSD bcrypt for prefix $2b$.
bcrypt was originally designed and implemented by
Niels Provos and
David Mazieres.
A paper on the algorithm that explains the design decisions is available
here.
The most important property of bcrypt (and thus crypt_blowfish)
is that it is adaptable to future processor performance improvements,
allowing you to arbitrarily increase the processing cost of checking a
password while still maintaining compatibility with your older
password hashes.
Already now bcrypt hashes you would use are several orders of
magnitude stronger than traditional Unix DES-based or FreeBSD-style
MD5-based hashes.
Today, a number of other operating systems, besides OpenBSD, support
bcrypt password hashes, with Niels' original implementation,
with this implementation (crypt_blowfish), or otherwise.
These systems include recent versions of FreeBSD and NetBSD, Solaris 10,
and indeed the Linux distributions that have integrated crypt_blowfish
(see below for a list).
Only some of these systems use bcrypt for newly set passwords
by default, though.
This code comes from John the Ripper password
cracker, and is placed in the public domain to let you use this on
your system, as part of a software package, or anywhere else to improve
security, ensure compatibility, or for any other purpose. There's no
license to worry about, not even a BSD-style copyright.
You can use the provided routines in your own packages or link them
into a C library. Hooks for linking into GNU libc are provided.
Note that simply adding this code into your libc is probably not enough
to make your system use the new password hashing algorithm. Changes to
passwd(1), PAM modules, or whatever else your system uses will likely
be needed as well. These are not part of this package, but there's
pam_tcb in the
Openwall GNU/*/Linux (Owl) tcb package
which uses the password hashing framework provided by crypt_blowfish,
and there are the Owl
shadow suite patches (in particular, the crypt_gensalt patch)
available from our CVSweb server.
Version 1.2 adds support for the $2y$ prefix (denoting correctly computed
hashes) and a countermeasure to avoid one-correct to many-buggy hash collisions
with the $2a$ prefix (desirable when upgrading systems with existing $2a$
hashes computed using pre-1.1 versions of crypt_blowfish).
Version 1.3 adds support for the $2b$ prefix introduced in OpenBSD 5.5+,
which behaves exactly the same as crypt_blowfish's $2y$.
This way, full compatibility with OpenBSD's bcrypt is achieved at this
new prefix.
crypt_blowfish was fully integrated into
Owl and
distributions by
ALT Linux
team as the default password hashing scheme,
although ALT Linux has since changed the default to yescrypt.
crypt_blowfish is part of the glibc package on
SUSE Linux.
Additionally, crypt_blowfish is used
in PHP 5.3.0+,
in the Suhosin security hardening patch for older versions of PHP,
in Crypt::Eksblowfish Perl module,
in PostgreSQL's contrib/pgcrypto providing bcrypt support for crypt() and gen_salt() SQL functions, and
in CommuniGate Pro messaging server starting with version 4.1
(but you need to explicitly configure CGP to use "UB-crpt" "password encryption" in order to have it produce bcrypt
hashes for new passwords).
crypt_blowfish is a registered project with
Open Hub.
