237673d052
These files are used to select s390x assembler support in the gc
toolchain. We don't currently have that support, as it is written in
the cmd/asm syntax rather than gas syntax. Mark the files to be ignored
for now, falling back to the default implementations.
Patch by Andreas Krebbel.
Reviewed-on: https://go-review.googlesource.com/26994
From-SVN: r239442
78 lines
2.3 KiB
Go
78 lines
2.3 KiB
Go
// Copyright 2016 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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// +build ignore
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package aes
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import (
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"crypto/cipher"
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"unsafe"
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)
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// Assert that aesCipherAsm implements the ctrAble interface.
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var _ ctrAble = (*aesCipherAsm)(nil)
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// xorBytes xors the contents of a and b and places the resulting values into
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// dst. If a and b are not the same length then the number of bytes processed
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// will be equal to the length of shorter of the two. Returns the number
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// of bytes processed.
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//go:noescape
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func xorBytes(dst, a, b []byte) int
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// streamBufferSize is the number of bytes of encrypted counter values to cache.
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const streamBufferSize = 32 * BlockSize
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type aesctr struct {
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block *aesCipherAsm // block cipher
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ctr [2]uint64 // next value of the counter (big endian)
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buffer []byte // buffer for the encrypted counter values
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storage [streamBufferSize]byte // array backing buffer slice
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}
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// NewCTR returns a Stream which encrypts/decrypts using the AES block
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// cipher in counter mode. The length of iv must be the same as BlockSize.
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func (c *aesCipherAsm) NewCTR(iv []byte) cipher.Stream {
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if len(iv) != BlockSize {
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panic("cipher.NewCTR: IV length must equal block size")
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}
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var ac aesctr
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ac.block = c
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ac.ctr[0] = *(*uint64)(unsafe.Pointer((&iv[0]))) // high bits
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ac.ctr[1] = *(*uint64)(unsafe.Pointer((&iv[8]))) // low bits
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ac.buffer = ac.storage[:0]
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return &ac
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}
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func (c *aesctr) refill() {
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// Fill up the buffer with an incrementing count.
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c.buffer = c.storage[:streamBufferSize]
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c0, c1 := c.ctr[0], c.ctr[1]
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for i := 0; i < streamBufferSize; i += BlockSize {
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b0 := (*uint64)(unsafe.Pointer(&c.buffer[i]))
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b1 := (*uint64)(unsafe.Pointer(&c.buffer[i+BlockSize/2]))
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*b0, *b1 = c0, c1
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// Increment in big endian: c0 is high, c1 is low.
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c1++
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if c1 == 0 {
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// add carry
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c0++
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}
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}
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c.ctr[0], c.ctr[1] = c0, c1
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// Encrypt the buffer using AES in ECB mode.
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cryptBlocks(c.block.function, &c.block.key[0], &c.buffer[0], &c.buffer[0], streamBufferSize)
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}
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func (c *aesctr) XORKeyStream(dst, src []byte) {
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for len(src) > 0 {
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if len(c.buffer) == 0 {
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c.refill()
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}
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n := xorBytes(dst, src, c.buffer)
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c.buffer = c.buffer[n:]
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src = src[n:]
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dst = dst[n:]
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}
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}
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