Package org.eclipse.jgit.util.sha1

Class SHA1

java.lang.Object

org.eclipse.jgit.util.sha1.SHA1

public class SHA1
extends java.lang.Object

Pure Java implementation of SHA-1 from FIPS 180-1 / RFC 3174.

See RFC 3174.

Unlike MessageDigest, this implementation includes the algorithm used by sha1dc to detect cryptanalytic collision attacks against SHA-1, such as the one used by SHAttered. See sha1collisiondetection for more information.

When detectCollision is true (default), this implementation throws Sha1CollisionException from any digest method if a potential collision was detected.

Since:

4.7

Nested Class Summary

Nested Classes

Modifier and Type	Class	Description
private static class	SHA1.State

Field Summary

Fields

Modifier and Type	Field	Description
private byte[]	buffer	Buffer to accumulate partial blocks to 64 byte alignment.
private static boolean	DETECT_COLLISIONS
private boolean	detectCollision
private boolean	foundCollision
private SHA1.State	h
private SHA1.State	hIn
private SHA1.State	hTmp
private long	length	Total number of bytes in the message.
private static org.slf4j.Logger	LOG
private SHA1.State	state58
private SHA1.State	state65
private int[]	w
private int[]	w2

Constructor Summary

Constructors

Modifier	Constructor	Description
private	SHA1()

Method Summary

Modifier and Type	Method	Description
private void	compress()
private void	compress(byte[] block, int p)
byte[]	digest()	Finish the digest and return the resulting hash.
void	digest(MutableObjectId id)	Finish the digest and return the resulting hash.
private static boolean	eq(SHA1.State q, SHA1.State r)
private void	finish()
boolean	hasCollision()	Check if a collision was detected.
private void	initBlock(byte[] block, int p)
static SHA1	newInstance()	Create a new context to compute a SHA-1 hash of data.
private void	recompress(int t)
SHA1	reset()	Reset this instance to compute another hash.
private static int	s1(int a, int b, int c, int d, int w_t)
private static int	s2(int a, int b, int c, int d, int w_t)
private static int	s3(int a, int b, int c, int d, int w_t)
private static int	s4(int a, int b, int c, int d, int w_t)
SHA1	setDetectCollision(boolean detect)	Enable likely collision detection.
ObjectId	toObjectId()	Finish the digest and return the resulting hash.
void	update(byte b)	Update the digest computation by adding a byte.
void	update(byte[] in)	Update the digest computation by adding bytes to the message.
void	update(byte[] in, int p, int len)	Update the digest computation by adding bytes to the message.

Methods inherited from class java.lang.Object

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

Field Detail

LOG

private static final org.slf4j.Logger LOG

DETECT_COLLISIONS

private static final boolean DETECT_COLLISIONS

h

private final SHA1.State h

w

private final int[] w

buffer

private final byte[] buffer

Buffer to accumulate partial blocks to 64 byte alignment.

length

private long length

Total number of bytes in the message.

detectCollision

private boolean detectCollision

foundCollision

private boolean foundCollision

w2

private final int[] w2

state58

private final SHA1.State state58

state65

private final SHA1.State state65

hIn

private final SHA1.State hIn

hTmp

private final SHA1.State hTmp

Constructor Detail

SHA1

private SHA1()

Method Detail

newInstance

public static SHA1 newInstance()

Create a new context to compute a SHA-1 hash of data.

Returns:

a new context to compute a SHA-1 hash of data.

setDetectCollision

public SHA1 setDetectCollision(boolean detect)

Enable likely collision detection.

Default is true.

May also be set by system property: -Dorg.eclipse.jgit.util.sha1.detectCollision=true.

Parameters:

detect - a boolean.

Returns:

this

update

public void update(byte b)

Update the digest computation by adding a byte.

Parameters:

b - a byte.

update

public void update(byte[] in)

Update the digest computation by adding bytes to the message.

Parameters:

in - input array of bytes.

update

public void update(byte[] in,
                   int p,
                   int len)

Update the digest computation by adding bytes to the message.

Parameters:

in - input array of bytes.

p - offset to start at from in.

len - number of bytes to hash.

compress

private void compress(byte[] block,
                      int p)

initBlock

private void initBlock(byte[] block,
                       int p)

compress

private void compress()

recompress

private void recompress(int t)

s1

private static int s1(int a,
                      int b,
                      int c,
                      int d,
                      int w_t)

s2

private static int s2(int a,
                      int b,
                      int c,
                      int d,
                      int w_t)

s3

private static int s3(int a,
                      int b,
                      int c,
                      int d,
                      int w_t)

s4

private static int s4(int a,
                      int b,
                      int c,
                      int d,
                      int w_t)

eq

private static boolean eq(SHA1.State q,
                          SHA1.State r)

finish

private void finish()

digest

public byte[] digest()
              throws Sha1CollisionException

Finish the digest and return the resulting hash.

Once digest() is called, this instance should be discarded.

Returns:

the bytes for the resulting hash.

Throws:

Sha1CollisionException - if a collision was detected and safeHash is false.

toObjectId

public ObjectId toObjectId()
                    throws Sha1CollisionException

Finish the digest and return the resulting hash.

Once digest() is called, this instance should be discarded.

Returns:

the ObjectId for the resulting hash.

Throws:

Sha1CollisionException - if a collision was detected and safeHash is false.

digest

public void digest(MutableObjectId id)
            throws Sha1CollisionException

Finish the digest and return the resulting hash.

Once digest() is called, this instance should be discarded.

Parameters:

id - destination to copy the digest to.

Throws:

Sha1CollisionException - if a collision was detected and safeHash is false.

hasCollision

public boolean hasCollision()

Check if a collision was detected.

This method only returns an accurate result after the digest was obtained through digest(), digest(MutableObjectId) or toObjectId(), as the hashing function must finish processing to know the final state.

Returns:

true if a likely collision was detected.

reset

public SHA1 reset()

Reset this instance to compute another hash.

Returns:

this.