1 files changed, 236 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 0000000..523751f
--- /dev/null
+++ b/vendor/golang.org/x/crypto/internal/chacha20/chacha_generic.go
@@ -0,0 +1,236 @@
+// 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}
+}
+
+// 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 {
+		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:])
+	}
+
+	// qr calculates a quarter round
+	qr := func(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
+	}
+
+	// ChaCha20 constants
+	const (
+		j0 = 0x61707865
+		j1 = 0x3320646e
+		j2 = 0x79622d32
+		j3 = 0x6b206574
+	)
+
+	// pre-calculate most of the first round
+	s1, s5, s9, s13 := qr(j1, s.key[1], s.key[5], s.nonce[0])
+	s2, s6, s10, s14 := qr(j2, s.key[2], s.key[6], s.nonce[1])
+	s3, s7, s11, s15 := qr(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 := qr(j0, s.key[0], s.key[4], s.counter)
+
+		// execute the second round
+		x0, x5, x10, x15 := qr(s0, s5, s10, s15)
+		x1, x6, x11, x12 := qr(s1, s6, s11, s12)
+		x2, x7, x8, x13 := qr(s2, s7, s8, s13)
+		x3, x4, x9, x14 := qr(s3, s4, s9, s14)
+
+		// execute the remaining 18 rounds
+		for i := 0; i < 9; i++ {
+			x0, x4, x8, x12 = qr(x0, x4, x8, x12)
+			x1, x5, x9, x13 = qr(x1, x5, x9, x13)
+			x2, x6, x10, x14 = qr(x2, x6, x10, x14)
+			x3, x7, x11, x15 = qr(x3, x7, x11, x15)
+
+			x0, x5, x10, x15 = qr(x0, x5, x10, x15)
+			x1, x6, x11, x12 = qr(x1, x6, x11, x12)
+			x2, x7, x8, x13 = qr(x2, x7, x8, x13)
+			x3, x4, x9, x14 = qr(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)
+}