Jon Portnoy > App-bmkpasswd > App::bmkpasswd

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Module Version: 2.005002   Source  

NAME ^

App::bmkpasswd - bcrypt-capable mkpasswd(1) and exported helpers

SYNOPSIS ^

  ## From Perl:

  use App::bmkpasswd 'mkpasswd', 'passwdcmp';
  my $bcrypted = mkpasswd($passwd);
  say 'matched' if passwdcmp($passwd, $bcrypted);

  ## From a shell:

  bmkpasswd --help
  
  # Generate bcrypted passwords:
  bmkpasswd

  # Defaults to work cost factor '08':
  bmkpasswd --workcost='06'

  # SHA requires Crypt::Passwd::XS or a recent libc:
  bmkpasswd --method='sha512'
  
  # Compare a hash:
  bmkpasswd --check=HASH

  # Check hash generation times:
  bmkpasswd --benchmark

DESCRIPTION ^

App::bmkpasswd is a bcrypt-enabled mkpasswd implementation.

Helper functions are also exported for use in other applications; see "EXPORTED". Crypt::Bcrypt::Easy provides an easier bcrypt-specific programmatic interface for Perl programmers.

See bmkpasswd --help for command-line usage information.

Uses Crypt::Eksblowfish::Bcrypt for bcrypted passwords.

Bcrypt leverages a work-cost factor allowing hash generation to become configurably slower as computers get faster, thereby impeding brute-force hash generation attempts. See http://codahale.com/how-to-safely-store-a-password/ for more on why you ought to be using bcrypt or similar "adaptive" techniques.

SHA-256 and SHA-512 are supported if available. SHA support requires either Crypt::Passwd::XS or a system crypt() that can handle SHA (such as glibc-2.7+ or modern FreeBSD builds).

Uses Bytes::Random::Secure to generate random salts. Strongly-random salts can also be enabled; see "mkpasswd".

For added security in public-facing applications, constant time comparison is used when comparing hashes.

EXPORTED ^

Crypt::Bcrypt::Easy provides an easier programmatic interface, if you're only interested in generating bcrypt passwords. If you'd like to make use of other password types, you can use the exported mkpasswd and passwdcmp functions:

  # Import selectively:
  use App::bmkpasswd 'mkpasswd', 'passwdcmp';
  # Or import all functions:
  use App::bmkpasswd -all;

This module uses Exporter::Tiny to export functions. This provides for flexible import options. See the Exporter::Tiny docs for details.

passwdcmp

Compare a password against a hash.

  if ( passwdcmp($plaintext, $crypted) ) {
    ## Successful match
  } else {
    ## Failed match
  }

passwdcmp will return the hash if it is a match; otherwise, an empty list is returned.

Uses constant time comparison to help mitigate against timing attacks.

mkpasswd_available

  my @available = mkpasswd_available;

  if ( mkpasswd_available('sha512') ) { ... }

Given no arguments, returns the list of available hash types.

Given a type (see "mkpasswd"), returns boolean true if the method is available. ('bcrypt' is always available.)

mkpasswd

  my $crypted = mkpasswd($passwd);
  my $crypted = mkpasswd($passwd, $type);
  my $crypted = mkpasswd($passwd, 'bcrypt', $cost);
  my $crypted = mkpasswd($passwd, $type, $cost, $strongsalt);

  my $crypted = mkpasswd( $passwd => 
    +{
      type    => $type,
      cost    => $cost,
      strong  => $strongsalt,
      saltgen => $saltgenerator,
    }
  );

Generate hashed passwords.

By default, generates a bcrypted passwd with work-cost 08:

  $bcrypted = mkpasswd($passwd);

A different work-cost can be specified for bcrypt passwds:

  $bcrypted = mkpasswd($passwd, 'bcrypt', '10');

SHA-256 and SHA-512 are supported, in which case the work-cost value is ignored:

  $crypted = mkpasswd($passwd, 'sha256');
  $crypted = mkpasswd($passwd, 'sha512');

If a fourth boolean-true argument is specified, a strongly-random salt is generated. This requires spare entropy, and will block if entropy-starved:

  $crypted = mkpasswd($passwd, 'bcrypt', '08', 'strong');
  $crypted = mkpasswd($passwd, 'sha512', 0, 'strong');

Options can be passed as a HASH, instead. This also lets you pass in a salt generator coderef:

  $crypted = mkpasswd( $passwd => +{
      type => 'bcrypt',
      cost => '10',
      strong  => 0,
      saltgen => $saltgenerator,
    }
  );

The salt generator is passed the type (one of: bcrypt, sha, md5) and the value of the strong option (default false).

  my $saltgenerator = sub {
    my ($type, $strongsalt) = @_;
    if ($type eq 'bcrypt') {
      # ...
    } elsif ($type eq 'sha') {
      # ...
    } else {
      die "Don't know how to create a salt for type '$type'!"
    }
  };

(Most people want random salts, in which case the default salt generator should be fine.)

AUTHOR ^

Jon Portnoy <avenj@cobaltirc.org>

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