mirror of
https://github.com/superseriousbusiness/gotosocial.git
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304 lines
7.5 KiB
Go
304 lines
7.5 KiB
Go
// Copyright 2017 The Go Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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//go:build gc && !purego
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package sha3
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// This file contains code for using the 'compute intermediate
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// message digest' (KIMD) and 'compute last message digest' (KLMD)
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// instructions to compute SHA-3 and SHAKE hashes on IBM Z.
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import (
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"hash"
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"golang.org/x/sys/cpu"
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)
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// codes represent 7-bit KIMD/KLMD function codes as defined in
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// the Principles of Operation.
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type code uint64
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const (
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// function codes for KIMD/KLMD
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sha3_224 code = 32
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sha3_256 = 33
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sha3_384 = 34
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sha3_512 = 35
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shake_128 = 36
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shake_256 = 37
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nopad = 0x100
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)
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// kimd is a wrapper for the 'compute intermediate message digest' instruction.
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// src must be a multiple of the rate for the given function code.
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//
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//go:noescape
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func kimd(function code, chain *[200]byte, src []byte)
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// klmd is a wrapper for the 'compute last message digest' instruction.
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// src padding is handled by the instruction.
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//
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//go:noescape
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func klmd(function code, chain *[200]byte, dst, src []byte)
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type asmState struct {
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a [200]byte // 1600 bit state
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buf []byte // care must be taken to ensure cap(buf) is a multiple of rate
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rate int // equivalent to block size
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storage [3072]byte // underlying storage for buf
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outputLen int // output length for full security
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function code // KIMD/KLMD function code
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state spongeDirection // whether the sponge is absorbing or squeezing
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}
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func newAsmState(function code) *asmState {
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var s asmState
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s.function = function
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switch function {
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case sha3_224:
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s.rate = 144
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s.outputLen = 28
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case sha3_256:
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s.rate = 136
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s.outputLen = 32
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case sha3_384:
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s.rate = 104
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s.outputLen = 48
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case sha3_512:
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s.rate = 72
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s.outputLen = 64
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case shake_128:
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s.rate = 168
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s.outputLen = 32
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case shake_256:
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s.rate = 136
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s.outputLen = 64
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default:
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panic("sha3: unrecognized function code")
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}
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// limit s.buf size to a multiple of s.rate
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s.resetBuf()
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return &s
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}
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func (s *asmState) clone() *asmState {
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c := *s
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c.buf = c.storage[:len(s.buf):cap(s.buf)]
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return &c
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}
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// copyIntoBuf copies b into buf. It will panic if there is not enough space to
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// store all of b.
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func (s *asmState) copyIntoBuf(b []byte) {
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bufLen := len(s.buf)
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s.buf = s.buf[:len(s.buf)+len(b)]
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copy(s.buf[bufLen:], b)
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}
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// resetBuf points buf at storage, sets the length to 0 and sets cap to be a
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// multiple of the rate.
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func (s *asmState) resetBuf() {
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max := (cap(s.storage) / s.rate) * s.rate
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s.buf = s.storage[:0:max]
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}
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// Write (via the embedded io.Writer interface) adds more data to the running hash.
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// It never returns an error.
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func (s *asmState) Write(b []byte) (int, error) {
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if s.state != spongeAbsorbing {
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panic("sha3: Write after Read")
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}
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length := len(b)
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for len(b) > 0 {
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if len(s.buf) == 0 && len(b) >= cap(s.buf) {
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// Hash the data directly and push any remaining bytes
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// into the buffer.
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remainder := len(b) % s.rate
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kimd(s.function, &s.a, b[:len(b)-remainder])
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if remainder != 0 {
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s.copyIntoBuf(b[len(b)-remainder:])
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}
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return length, nil
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}
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if len(s.buf) == cap(s.buf) {
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// flush the buffer
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kimd(s.function, &s.a, s.buf)
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s.buf = s.buf[:0]
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}
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// copy as much as we can into the buffer
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n := len(b)
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if len(b) > cap(s.buf)-len(s.buf) {
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n = cap(s.buf) - len(s.buf)
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}
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s.copyIntoBuf(b[:n])
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b = b[n:]
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}
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return length, nil
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}
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// Read squeezes an arbitrary number of bytes from the sponge.
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func (s *asmState) Read(out []byte) (n int, err error) {
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// The 'compute last message digest' instruction only stores the digest
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// at the first operand (dst) for SHAKE functions.
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if s.function != shake_128 && s.function != shake_256 {
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panic("sha3: can only call Read for SHAKE functions")
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}
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n = len(out)
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// need to pad if we were absorbing
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if s.state == spongeAbsorbing {
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s.state = spongeSqueezing
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// write hash directly into out if possible
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if len(out)%s.rate == 0 {
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klmd(s.function, &s.a, out, s.buf) // len(out) may be 0
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s.buf = s.buf[:0]
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return
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}
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// write hash into buffer
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max := cap(s.buf)
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if max > len(out) {
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max = (len(out)/s.rate)*s.rate + s.rate
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}
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klmd(s.function, &s.a, s.buf[:max], s.buf)
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s.buf = s.buf[:max]
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}
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for len(out) > 0 {
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// flush the buffer
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if len(s.buf) != 0 {
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c := copy(out, s.buf)
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out = out[c:]
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s.buf = s.buf[c:]
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continue
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}
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// write hash directly into out if possible
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if len(out)%s.rate == 0 {
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klmd(s.function|nopad, &s.a, out, nil)
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return
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}
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// write hash into buffer
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s.resetBuf()
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if cap(s.buf) > len(out) {
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s.buf = s.buf[:(len(out)/s.rate)*s.rate+s.rate]
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}
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klmd(s.function|nopad, &s.a, s.buf, nil)
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}
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return
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}
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// Sum appends the current hash to b and returns the resulting slice.
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// It does not change the underlying hash state.
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func (s *asmState) Sum(b []byte) []byte {
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if s.state != spongeAbsorbing {
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panic("sha3: Sum after Read")
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}
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// Copy the state to preserve the original.
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a := s.a
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// Hash the buffer. Note that we don't clear it because we
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// aren't updating the state.
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switch s.function {
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case sha3_224, sha3_256, sha3_384, sha3_512:
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klmd(s.function, &a, nil, s.buf)
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return append(b, a[:s.outputLen]...)
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case shake_128, shake_256:
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d := make([]byte, s.outputLen, 64)
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klmd(s.function, &a, d, s.buf)
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return append(b, d[:s.outputLen]...)
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default:
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panic("sha3: unknown function")
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}
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}
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// Reset resets the Hash to its initial state.
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func (s *asmState) Reset() {
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for i := range s.a {
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s.a[i] = 0
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}
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s.resetBuf()
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s.state = spongeAbsorbing
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}
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// Size returns the number of bytes Sum will return.
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func (s *asmState) Size() int {
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return s.outputLen
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}
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// BlockSize returns the hash's underlying block size.
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// The Write method must be able to accept any amount
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// of data, but it may operate more efficiently if all writes
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// are a multiple of the block size.
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func (s *asmState) BlockSize() int {
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return s.rate
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}
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// Clone returns a copy of the ShakeHash in its current state.
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func (s *asmState) Clone() ShakeHash {
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return s.clone()
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}
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// new224 returns an assembly implementation of SHA3-224 if available,
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// otherwise it returns a generic implementation.
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func new224() hash.Hash {
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if cpu.S390X.HasSHA3 {
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return newAsmState(sha3_224)
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}
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return new224Generic()
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}
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// new256 returns an assembly implementation of SHA3-256 if available,
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// otherwise it returns a generic implementation.
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func new256() hash.Hash {
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if cpu.S390X.HasSHA3 {
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return newAsmState(sha3_256)
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}
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return new256Generic()
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}
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// new384 returns an assembly implementation of SHA3-384 if available,
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// otherwise it returns a generic implementation.
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func new384() hash.Hash {
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if cpu.S390X.HasSHA3 {
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return newAsmState(sha3_384)
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}
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return new384Generic()
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}
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// new512 returns an assembly implementation of SHA3-512 if available,
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// otherwise it returns a generic implementation.
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func new512() hash.Hash {
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if cpu.S390X.HasSHA3 {
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return newAsmState(sha3_512)
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}
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return new512Generic()
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}
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// newShake128 returns an assembly implementation of SHAKE-128 if available,
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// otherwise it returns a generic implementation.
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func newShake128() ShakeHash {
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if cpu.S390X.HasSHA3 {
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return newAsmState(shake_128)
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}
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return newShake128Generic()
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}
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// newShake256 returns an assembly implementation of SHAKE-256 if available,
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// otherwise it returns a generic implementation.
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func newShake256() ShakeHash {
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if cpu.S390X.HasSHA3 {
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return newAsmState(shake_256)
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}
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return newShake256Generic()
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}
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