diff options
Diffstat (limited to 'vendor/golang.org/x/crypto/internal/chacha20/chacha_generic.go')
-rw-r--r-- | vendor/golang.org/x/crypto/internal/chacha20/chacha_generic.go | 264 |
1 files changed, 264 insertions, 0 deletions
diff --git a/vendor/golang.org/x/crypto/internal/chacha20/chacha_generic.go b/vendor/golang.org/x/crypto/internal/chacha20/chacha_generic.go new file mode 100644 index 000000000..6570847f5 --- /dev/null +++ b/vendor/golang.org/x/crypto/internal/chacha20/chacha_generic.go @@ -0,0 +1,264 @@ +// Copyright 2016 The Go Authors. All rights reserved. +// Use of this source code is governed by a BSD-style +// license that can be found in the LICENSE file. + +// Package ChaCha20 implements the core ChaCha20 function as specified +// in https://tools.ietf.org/html/rfc7539#section-2.3. +package chacha20 + +import ( + "crypto/cipher" + "encoding/binary" + + "golang.org/x/crypto/internal/subtle" +) + +// assert that *Cipher implements cipher.Stream +var _ cipher.Stream = (*Cipher)(nil) + +// Cipher is a stateful instance of ChaCha20 using a particular key +// and nonce. A *Cipher implements the cipher.Stream interface. +type Cipher struct { + key [8]uint32 + counter uint32 // incremented after each block + nonce [3]uint32 + buf [bufSize]byte // buffer for unused keystream bytes + len int // number of unused keystream bytes at end of buf +} + +// New creates a new ChaCha20 stream cipher with the given key and nonce. +// The initial counter value is set to 0. +func New(key [8]uint32, nonce [3]uint32) *Cipher { + return &Cipher{key: key, nonce: nonce} +} + +// ChaCha20 constants spelling "expand 32-byte k" +const ( + j0 uint32 = 0x61707865 + j1 uint32 = 0x3320646e + j2 uint32 = 0x79622d32 + j3 uint32 = 0x6b206574 +) + +func quarterRound(a, b, c, d uint32) (uint32, uint32, uint32, uint32) { + a += b + d ^= a + d = (d << 16) | (d >> 16) + c += d + b ^= c + b = (b << 12) | (b >> 20) + a += b + d ^= a + d = (d << 8) | (d >> 24) + c += d + b ^= c + b = (b << 7) | (b >> 25) + return a, b, c, d +} + +// XORKeyStream XORs each byte in the given slice with a byte from the +// cipher's key stream. Dst and src must overlap entirely or not at all. +// +// If len(dst) < len(src), XORKeyStream will panic. It is acceptable +// to pass a dst bigger than src, and in that case, XORKeyStream will +// only update dst[:len(src)] and will not touch the rest of dst. +// +// Multiple calls to XORKeyStream behave as if the concatenation of +// the src buffers was passed in a single run. That is, Cipher +// maintains state and does not reset at each XORKeyStream call. +func (s *Cipher) XORKeyStream(dst, src []byte) { + if len(dst) < len(src) { + panic("chacha20: output smaller than input") + } + if subtle.InexactOverlap(dst[:len(src)], src) { + panic("chacha20: invalid buffer overlap") + } + + // xor src with buffered keystream first + if s.len != 0 { + buf := s.buf[len(s.buf)-s.len:] + if len(src) < len(buf) { + buf = buf[:len(src)] + } + td, ts := dst[:len(buf)], src[:len(buf)] // BCE hint + for i, b := range buf { + td[i] = ts[i] ^ b + } + s.len -= len(buf) + if s.len != 0 { + return + } + s.buf = [len(s.buf)]byte{} // zero the empty buffer + src = src[len(buf):] + dst = dst[len(buf):] + } + + if len(src) == 0 { + return + } + if haveAsm { + if uint64(len(src))+uint64(s.counter)*64 > (1<<38)-64 { + panic("chacha20: counter overflow") + } + s.xorKeyStreamAsm(dst, src) + return + } + + // set up a 64-byte buffer to pad out the final block if needed + // (hoisted out of the main loop to avoid spills) + rem := len(src) % 64 // length of final block + fin := len(src) - rem // index of final block + if rem > 0 { + copy(s.buf[len(s.buf)-64:], src[fin:]) + } + + // pre-calculate most of the first round + s1, s5, s9, s13 := quarterRound(j1, s.key[1], s.key[5], s.nonce[0]) + s2, s6, s10, s14 := quarterRound(j2, s.key[2], s.key[6], s.nonce[1]) + s3, s7, s11, s15 := quarterRound(j3, s.key[3], s.key[7], s.nonce[2]) + + n := len(src) + src, dst = src[:n:n], dst[:n:n] // BCE hint + for i := 0; i < n; i += 64 { + // calculate the remainder of the first round + s0, s4, s8, s12 := quarterRound(j0, s.key[0], s.key[4], s.counter) + + // execute the second round + x0, x5, x10, x15 := quarterRound(s0, s5, s10, s15) + x1, x6, x11, x12 := quarterRound(s1, s6, s11, s12) + x2, x7, x8, x13 := quarterRound(s2, s7, s8, s13) + x3, x4, x9, x14 := quarterRound(s3, s4, s9, s14) + + // execute the remaining 18 rounds + for i := 0; i < 9; i++ { + x0, x4, x8, x12 = quarterRound(x0, x4, x8, x12) + x1, x5, x9, x13 = quarterRound(x1, x5, x9, x13) + x2, x6, x10, x14 = quarterRound(x2, x6, x10, x14) + x3, x7, x11, x15 = quarterRound(x3, x7, x11, x15) + + x0, x5, x10, x15 = quarterRound(x0, x5, x10, x15) + x1, x6, x11, x12 = quarterRound(x1, x6, x11, x12) + x2, x7, x8, x13 = quarterRound(x2, x7, x8, x13) + x3, x4, x9, x14 = quarterRound(x3, x4, x9, x14) + } + + x0 += j0 + x1 += j1 + x2 += j2 + x3 += j3 + + x4 += s.key[0] + x5 += s.key[1] + x6 += s.key[2] + x7 += s.key[3] + x8 += s.key[4] + x9 += s.key[5] + x10 += s.key[6] + x11 += s.key[7] + + x12 += s.counter + x13 += s.nonce[0] + x14 += s.nonce[1] + x15 += s.nonce[2] + + // increment the counter + s.counter += 1 + if s.counter == 0 { + panic("chacha20: counter overflow") + } + + // pad to 64 bytes if needed + in, out := src[i:], dst[i:] + if i == fin { + // src[fin:] has already been copied into s.buf before + // the main loop + in, out = s.buf[len(s.buf)-64:], s.buf[len(s.buf)-64:] + } + in, out = in[:64], out[:64] // BCE hint + + // XOR the key stream with the source and write out the result + xor(out[0:], in[0:], x0) + xor(out[4:], in[4:], x1) + xor(out[8:], in[8:], x2) + xor(out[12:], in[12:], x3) + xor(out[16:], in[16:], x4) + xor(out[20:], in[20:], x5) + xor(out[24:], in[24:], x6) + xor(out[28:], in[28:], x7) + xor(out[32:], in[32:], x8) + xor(out[36:], in[36:], x9) + xor(out[40:], in[40:], x10) + xor(out[44:], in[44:], x11) + xor(out[48:], in[48:], x12) + xor(out[52:], in[52:], x13) + xor(out[56:], in[56:], x14) + xor(out[60:], in[60:], x15) + } + // copy any trailing bytes out of the buffer and into dst + if rem != 0 { + s.len = 64 - rem + copy(dst[fin:], s.buf[len(s.buf)-64:]) + } +} + +// Advance discards bytes in the key stream until the next 64 byte block +// boundary is reached and updates the counter accordingly. If the key +// stream is already at a block boundary no bytes will be discarded and +// the counter will be unchanged. +func (s *Cipher) Advance() { + s.len -= s.len % 64 + if s.len == 0 { + s.buf = [len(s.buf)]byte{} + } +} + +// XORKeyStream crypts bytes from in to out using the given key and counters. +// In and out must overlap entirely or not at all. Counter contains the raw +// ChaCha20 counter bytes (i.e. block counter followed by nonce). +func XORKeyStream(out, in []byte, counter *[16]byte, key *[32]byte) { + s := Cipher{ + key: [8]uint32{ + binary.LittleEndian.Uint32(key[0:4]), + binary.LittleEndian.Uint32(key[4:8]), + binary.LittleEndian.Uint32(key[8:12]), + binary.LittleEndian.Uint32(key[12:16]), + binary.LittleEndian.Uint32(key[16:20]), + binary.LittleEndian.Uint32(key[20:24]), + binary.LittleEndian.Uint32(key[24:28]), + binary.LittleEndian.Uint32(key[28:32]), + }, + nonce: [3]uint32{ + binary.LittleEndian.Uint32(counter[4:8]), + binary.LittleEndian.Uint32(counter[8:12]), + binary.LittleEndian.Uint32(counter[12:16]), + }, + counter: binary.LittleEndian.Uint32(counter[0:4]), + } + s.XORKeyStream(out, in) +} + +// HChaCha20 uses the ChaCha20 core to generate a derived key from a key and a +// nonce. It should only be used as part of the XChaCha20 construction. +func HChaCha20(key *[8]uint32, nonce *[4]uint32) [8]uint32 { + x0, x1, x2, x3 := j0, j1, j2, j3 + x4, x5, x6, x7 := key[0], key[1], key[2], key[3] + x8, x9, x10, x11 := key[4], key[5], key[6], key[7] + x12, x13, x14, x15 := nonce[0], nonce[1], nonce[2], nonce[3] + + for i := 0; i < 10; i++ { + x0, x4, x8, x12 = quarterRound(x0, x4, x8, x12) + x1, x5, x9, x13 = quarterRound(x1, x5, x9, x13) + x2, x6, x10, x14 = quarterRound(x2, x6, x10, x14) + x3, x7, x11, x15 = quarterRound(x3, x7, x11, x15) + + x0, x5, x10, x15 = quarterRound(x0, x5, x10, x15) + x1, x6, x11, x12 = quarterRound(x1, x6, x11, x12) + x2, x7, x8, x13 = quarterRound(x2, x7, x8, x13) + x3, x4, x9, x14 = quarterRound(x3, x4, x9, x14) + } + + var out [8]uint32 + out[0], out[1], out[2], out[3] = x0, x1, x2, x3 + out[4], out[5], out[6], out[7] = x12, x13, x14, x15 + return out +} |