ergo/irc/migrations/sha256.go

/*
Copyright (c) 2009 The Go Authors. All rights reserved.

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   * Redistributions of source code must retain the above copyright
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   * Redistributions in binary form must reproduce the above
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"AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
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LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
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*/

// SHA256 implementation from golang/go, modified to accommodate anope's
// password hashing scheme, which overrides the initialization vector
// using the salt.

package migrations

import (
	"encoding/binary"
)

// The size of a SHA256 checksum in bytes.
const Size = 32

const (
	chunk = 64
)

// digest represents the partial evaluation of a checksum.
type digest struct {
	h   [8]uint32
	x   [chunk]byte
	nx  int
	len uint64
}

func (d *digest) Write(p []byte) (nn int, err error) {
	nn = len(p)
	d.len += uint64(nn)
	if d.nx > 0 {
		n := copy(d.x[d.nx:], p)
		d.nx += n
		if d.nx == chunk {
			sha256BlockGeneric(d, d.x[:])
			d.nx = 0
		}
		p = p[n:]
	}
	if len(p) >= chunk {
		n := len(p) &^ (chunk - 1)
		sha256BlockGeneric(d, p[:n])
		p = p[n:]
	}
	if len(p) > 0 {
		d.nx = copy(d.x[:], p)
	}
	return
}

func (d *digest) Sum(in []byte) []byte {
	// Make a copy of d so that caller can keep writing and summing.
	d0 := *d
	hash := d0.checkSum()
	return append(in, hash[:]...)
}

func (d *digest) checkSum() [Size]byte {
	len := d.len
	// Padding. Add a 1 bit and 0 bits until 56 bytes mod 64.
	var tmp [64]byte
	tmp[0] = 0x80
	if len%64 < 56 {
		d.Write(tmp[0 : 56-len%64])
	} else {
		d.Write(tmp[0 : 64+56-len%64])
	}

	// Length in bits.
	len <<= 3
	binary.BigEndian.PutUint64(tmp[:], len)
	d.Write(tmp[0:8])

	if d.nx != 0 {
		panic("d.nx != 0")
	}

	var digest [Size]byte

	binary.BigEndian.PutUint32(digest[0:], d.h[0])
	binary.BigEndian.PutUint32(digest[4:], d.h[1])
	binary.BigEndian.PutUint32(digest[8:], d.h[2])
	binary.BigEndian.PutUint32(digest[12:], d.h[3])
	binary.BigEndian.PutUint32(digest[16:], d.h[4])
	binary.BigEndian.PutUint32(digest[20:], d.h[5])
	binary.BigEndian.PutUint32(digest[24:], d.h[6])
	binary.BigEndian.PutUint32(digest[28:], d.h[7])

	return digest
}

// Anope password hashing function: SHA-256 with an override for the IV
// The actual SHA-256 IV for reference:
// [8]uint32{0x6A09E667, 0xBB67AE85, 0x3C6EF372, 0xA54FF53A, 0x510E527F, 0x9B05688C, 0x1F83D9AB, 0x5BE0CD19}
func anopeSum256(data []byte, iv [8]uint32) [Size]byte {
	var d digest
	d.h = iv
	d.Write(data)
	return d.checkSum()
}