arlut.csd.crypto

Class Sha512Crypt

java.lang.Object

arlut.csd.crypto.Sha512Crypt

public final class Sha512Crypt
extends java.lang.Object

This class defines a method, Sha512_crypt(), which takes a password and a salt string and generates a Sha512 encrypted password entry.

This class implements the new generation, scalable, SHA512-based Unix 'crypt' algorithm developed by a group of engineers from Red Hat, Sun, IBM, and HP for common use in the Unix and Linux /etc/shadow files.

The Linux glibc library (starting at version 2.7) includes support for validating passwords hashed using this algorithm.

The algorithm itself was released into the Public Domain by Ulrich Drepper <drepper@redhat.com>. A discussion of the rationale and development of this algorithm is at

http://people.redhat.com/drepper/sha-crypt.html

and the specification and a sample C language implementation is at

http://people.redhat.com/drepper/SHA-crypt.txt

Field Summary

Fields

Modifier and Type	Field and Description
private static java.lang.String	itoa64
private static int	ROUNDS_DEFAULT
private static int	ROUNDS_MAX
private static int	ROUNDS_MIN
private static int	SALT_LEN_MAX
private static java.lang.String	SALTCHARS
private static java.lang.String	sha512_rounds_prefix
private static java.lang.String	sha512_salt_prefix

Constructor Summary

Constructors

Constructor and Description
Sha512Crypt()

Method Summary

Methods

Modifier and Type	Method and Description
private static java.lang.String	b64_from_24bit(byte B2, byte B1, byte B0, int size)
private static java.security.MessageDigest	getSHA512()
static void	main(java.lang.String[] arg) Test rig
private static void	selfTest() Validate our implementation using test data from Ulrich Drepper's C implementation.
static java.lang.String	Sha512_crypt(java.lang.String keyStr, java.lang.String saltStr, int roundsCount) This method actually generates an Sha512 crypted password hash from a plaintext password and a salt.
static boolean	verifyHashTextFormat(java.lang.String sha512CryptText) Returns true if sha512CryptText is a valid Sha512Crypt hashtext, false if not.
static boolean	verifyPassword(java.lang.String plaintextPass, java.lang.String sha512CryptText) This method tests a plaintext password against a SHA512 Unix Crypt'ed hash and returns true if the password matches the hash.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail

sha512_salt_prefix

private static final java.lang.String sha512_salt_prefix

See Also:

Constant Field Values

sha512_rounds_prefix

private static final java.lang.String sha512_rounds_prefix

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Constant Field Values

SALT_LEN_MAX

private static final int SALT_LEN_MAX

See Also:

Constant Field Values

ROUNDS_DEFAULT

private static final int ROUNDS_DEFAULT

See Also:

Constant Field Values

ROUNDS_MIN

private static final int ROUNDS_MIN

See Also:

Constant Field Values

ROUNDS_MAX

private static final int ROUNDS_MAX

See Also:

Constant Field Values

SALTCHARS

private static final java.lang.String SALTCHARS

See Also:

Constant Field Values

itoa64

private static final java.lang.String itoa64

See Also:

Constant Field Values

Constructor Detail

Sha512Crypt

public Sha512Crypt()

Method Detail

getSHA512

private static java.security.MessageDigest getSHA512()

Sha512_crypt

public static final java.lang.String Sha512_crypt(java.lang.String keyStr,
                            java.lang.String saltStr,
                            int roundsCount)

This method actually generates an Sha512 crypted password hash from a plaintext password and a salt.

The resulting string will be in the form '$6$<rounds=n>$<salt>$<hashed mess>

Parameters:

keyStr - Plaintext password

saltStr - An encoded salt/roundes which will be consulted to determine the salt and round count, if not null

roundsCount - If this value is not 0, this many rounds will used to generate the hash text.

Returns:

The Sha512 Unix Crypt hash text for the keyStr

b64_from_24bit

private static final java.lang.String b64_from_24bit(byte B2,
                              byte B1,
                              byte B0,
                              int size)

verifyPassword

public static final boolean verifyPassword(java.lang.String plaintextPass,
                     java.lang.String sha512CryptText)

This method tests a plaintext password against a SHA512 Unix Crypt'ed hash and returns true if the password matches the hash.

Parameters:

plaintextPass - The plaintext password text to test.

sha512CryptText - The hash text we're testing against. We'll extract the salt and the round count from this String.

verifyHashTextFormat

public static final boolean verifyHashTextFormat(java.lang.String sha512CryptText)

Returns true if sha512CryptText is a valid Sha512Crypt hashtext, false if not.

selfTest

private static void selfTest()

Validate our implementation using test data from Ulrich Drepper's C implementation.

main

public static void main(java.lang.String[] arg)

Test rig