IABSD.fr/src/lib/libc/crypt/crypt.3

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• Author : tedu
  Date : 2015-04-06 20:49:41
  Hash : 4c974c3f
  Message : bludgeon DES support out of crypt. long live the bcrypt.

• lib/libc/crypt/crypt.3

• .\" $OpenBSD: crypt.3,v 1.45 2015/04/06 20:49:41 tedu Exp $
  .\"
  .\" FreeSec: libcrypt
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  .\" Copyright (c) 1994 David Burren
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  .\" Manual page, using -mandoc macros
  .\"
  .Dd $Mdocdate: April 6 2015 $
  .Dt CRYPT 3
  .Os
  .Sh NAME
  .Nm crypt ,
  .Nm bcrypt_gensalt ,
  .Nm bcrypt
  .Nd password hashing
  .Sh SYNOPSIS
  .In stdlib.h
  .Pp
  .In unistd.h
  .Ft char *
  .Fn crypt "const char *key" "const char *setting"
  .In pwd.h
  .Ft char *
  .Fn bcrypt_gensalt "u_int8_t log_rounds"
  .Ft char *
  .Fn bcrypt "const char *key" "const char *salt"
  .Sh DESCRIPTION
  These functions are deprecated in favor of
  .Xr crypt_checkpass 3
  and
  .Xr crypt_newhash 3 .
  .Pp
  The
  .Fn crypt
  function performs password hashing.
  Additional code has been added to deter key search attempts and to use
  stronger hashing algorithms.
  .Pp
  The first argument to
  .Fn crypt
  is a NUL-terminated
  string
  .Fa key ,
  typically a user's typed password.
  The second,
  .Fa setting ,
  currently supports a single form.
  If it begins
  with a string character
  .Pq Ql $
  and a number then a different algorithm is used depending on the number.
  At the moment
  .Ql $2
  chooses Blowfish hashing; see below for more information.
  .Ss Blowfish crypt
  The Blowfish version of crypt has 128 bits of
  .Fa salt
  in order to make building dictionaries of common passwords space consuming.
  The initial state of the
  Blowfish cipher is expanded using the
  .Fa salt
  and the
  .Fa password
  repeating the process a variable number of rounds, which is encoded in
  the password string.
  The maximum password length is 72.
  The final Blowfish password entry is created by encrypting the string
  .Pp
  .Dq OrpheanBeholderScryDoubt
  .Pp
  with the Blowfish state 64 times.
  .Pp
  The version number, the logarithm of the number of rounds and
  the concatenation of salt and hashed password are separated by the
  .Ql $
  character.
  An encoded
  .Sq 8
  would specify 256 rounds.
  A valid Blowfish password looks like this:
  .Pp
  .Dq $2b$12$FPWWO2RJ3CK4FINTw0Hi8OiPKJcX653gzSS.jqltHFMxyDmmQ0Hqq .
  .Pp
  The whole Blowfish password string is passed as
  .Fa setting
  for interpretation.
  .Sh RETURN VALUES
  The function
  .Fn crypt
  returns a pointer to the encrypted value on success, and
  .Dv NULL
  on failure.
  .Sh SEE ALSO
  .Xr encrypt 1 ,
  .Xr login 1 ,
  .Xr passwd 1 ,
  .Xr blowfish 3 ,
  .Xr crypt_checkpass 3 ,
  .Xr getpass 3 ,
  .Xr passwd 5
  .Sh HISTORY
  A rotor-based
  .Fn crypt
  function appeared in
  .At v3 .
  A DES-based
  .Fn crypt
  first appeared in
  .At v7 .
  .Fn bcrypt
  first appeared in
  .Ox 2.1 .
  .Sh BUGS
  The
  .Fn crypt
  function returns a pointer to static data, and subsequent calls to
  .Fn crypt
  will modify the same object.