1 files changed, 263 insertions, 0 deletions
diff --git a/sha3/legacy_hash.go b/sha3/legacy_hash.go
new file mode 100644
index 0000000..b878453
--- /dev/null
+++ b/sha3/legacy_hash.go
@@ -0,0 +1,263 @@
+// Copyright 2014 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 sha3
+
+// This implementation is only used for NewLegacyKeccak256 and
+// NewLegacyKeccak512, which are not implemented by crypto/sha3.
+// All other functions in this package are wrappers around crypto/sha3.
+
+import (
+	"crypto/subtle"
+	"encoding/binary"
+	"errors"
+	"hash"
+	"unsafe"
+
+	"golang.org/x/sys/cpu"
+)
+
+const (
+	dsbyteKeccak = 0b00000001
+
+	// rateK[c] is the rate in bytes for Keccak[c] where c is the capacity in
+	// bits. Given the sponge size is 1600 bits, the rate is 1600 - c bits.
+	rateK256  = (1600 - 256) / 8
+	rateK512  = (1600 - 512) / 8
+	rateK1024 = (1600 - 1024) / 8
+)
+
+// NewLegacyKeccak256 creates a new Keccak-256 hash.
+//
+// Only use this function if you require compatibility with an existing cryptosystem
+// that uses non-standard padding. All other users should use New256 instead.
+func NewLegacyKeccak256() hash.Hash {
+	return &state{rate: rateK512, outputLen: 32, dsbyte: dsbyteKeccak}
+}
+
+// NewLegacyKeccak512 creates a new Keccak-512 hash.
+//
+// Only use this function if you require compatibility with an existing cryptosystem
+// that uses non-standard padding. All other users should use New512 instead.
+func NewLegacyKeccak512() hash.Hash {
+	return &state{rate: rateK1024, outputLen: 64, dsbyte: dsbyteKeccak}
+}
+
+// spongeDirection indicates the direction bytes are flowing through the sponge.
+type spongeDirection int
+
+const (
+	// spongeAbsorbing indicates that the sponge is absorbing input.
+	spongeAbsorbing spongeDirection = iota
+	// spongeSqueezing indicates that the sponge is being squeezed.
+	spongeSqueezing
+)
+
+type state struct {
+	a [1600 / 8]byte // main state of the hash
+
+	// a[n:rate] is the buffer. If absorbing, it's the remaining space to XOR
+	// into before running the permutation. If squeezing, it's the remaining
+	// output to produce before running the permutation.
+	n, rate int
+
+	// dsbyte contains the "domain separation" bits and the first bit of
+	// the padding. Sections 6.1 and 6.2 of [1] separate the outputs of the
+	// SHA-3 and SHAKE functions by appending bitstrings to the message.
+	// Using a little-endian bit-ordering convention, these are "01" for SHA-3
+	// and "1111" for SHAKE, or 00000010b and 00001111b, respectively. Then the
+	// padding rule from section 5.1 is applied to pad the message to a multiple
+	// of the rate, which involves adding a "1" bit, zero or more "0" bits, and
+	// a final "1" bit. We merge the first "1" bit from the padding into dsbyte,
+	// giving 00000110b (0x06) and 00011111b (0x1f).
+	// [1] http://csrc.nist.gov/publications/drafts/fips-202/fips_202_draft.pdf
+	//     "Draft FIPS 202: SHA-3 Standard: Permutation-Based Hash and
+	//      Extendable-Output Functions (May 2014)"
+	dsbyte byte
+
+	outputLen int             // the default output size in bytes
+	state     spongeDirection // whether the sponge is absorbing or squeezing
+}
+
+// BlockSize returns the rate of sponge underlying this hash function.
+func (d *state) BlockSize() int { return d.rate }
+
+// Size returns the output size of the hash function in bytes.
+func (d *state) Size() int { return d.outputLen }
+
+// Reset clears the internal state by zeroing the sponge state and
+// the buffer indexes, and setting Sponge.state to absorbing.
+func (d *state) Reset() {
+	// Zero the permutation's state.
+	for i := range d.a {
+		d.a[i] = 0
+	}
+	d.state = spongeAbsorbing
+	d.n = 0
+}
+
+func (d *state) clone() *state {
+	ret := *d
+	return &ret
+}
+
+// permute applies the KeccakF-1600 permutation.
+func (d *state) permute() {
+	var a *[25]uint64
+	if cpu.IsBigEndian {
+		a = new([25]uint64)
+		for i := range a {
+			a[i] = binary.LittleEndian.Uint64(d.a[i*8:])
+		}
+	} else {
+		a = (*[25]uint64)(unsafe.Pointer(&d.a))
+	}
+
+	keccakF1600(a)
+	d.n = 0
+
+	if cpu.IsBigEndian {
+		for i := range a {
+			binary.LittleEndian.PutUint64(d.a[i*8:], a[i])
+		}
+	}
+}
+
+// pads appends the domain separation bits in dsbyte, applies
+// the multi-bitrate 10..1 padding rule, and permutes the state.
+func (d *state) padAndPermute() {
+	// Pad with this instance's domain-separator bits. We know that there's
+	// at least one byte of space in the sponge because, if it were full,
+	// permute would have been called to empty it. dsbyte also contains the
+	// first one bit for the padding. See the comment in the state struct.
+	d.a[d.n] ^= d.dsbyte
+	// This adds the final one bit for the padding. Because of the way that
+	// bits are numbered from the LSB upwards, the final bit is the MSB of
+	// the last byte.
+	d.a[d.rate-1] ^= 0x80
+	// Apply the permutation
+	d.permute()
+	d.state = spongeSqueezing
+}
+
+// Write absorbs more data into the hash's state. It panics if any
+// output has already been read.
+func (d *state) Write(p []byte) (n int, err error) {
+	if d.state != spongeAbsorbing {
+		panic("sha3: Write after Read")
+	}
+
+	n = len(p)
+
+	for len(p) > 0 {
+		x := subtle.XORBytes(d.a[d.n:d.rate], d.a[d.n:d.rate], p)
+		d.n += x
+		p = p[x:]
+
+		// If the sponge is full, apply the permutation.
+		if d.n == d.rate {
+			d.permute()
+		}
+	}
+
+	return
+}
+
+// Read squeezes an arbitrary number of bytes from the sponge.
+func (d *state) Read(out []byte) (n int, err error) {
+	// If we're still absorbing, pad and apply the permutation.
+	if d.state == spongeAbsorbing {
+		d.padAndPermute()
+	}
+
+	n = len(out)
+
+	// Now, do the squeezing.
+	for len(out) > 0 {
+		// Apply the permutation if we've squeezed the sponge dry.
+		if d.n == d.rate {
+			d.permute()
+		}
+
+		x := copy(out, d.a[d.n:d.rate])
+		d.n += x
+		out = out[x:]
+	}
+
+	return
+}
+
+// Sum applies padding to the hash state and then squeezes out the desired
+// number of output bytes. It panics if any output has already been read.
+func (d *state) Sum(in []byte) []byte {
+	if d.state != spongeAbsorbing {
+		panic("sha3: Sum after Read")
+	}
+
+	// Make a copy of the original hash so that caller can keep writing
+	// and summing.
+	dup := d.clone()
+	hash := make([]byte, dup.outputLen, 64) // explicit cap to allow stack allocation
+	dup.Read(hash)
+	return append(in, hash...)
+}
+
+const (
+	magicKeccak = "sha\x0b"
+	// magic || rate || main state || n || sponge direction
+	marshaledSize = len(magicKeccak) + 1 + 200 + 1 + 1
+)
+
+func (d *state) MarshalBinary() ([]byte, error) {
+	return d.AppendBinary(make([]byte, 0, marshaledSize))
+}
+
+func (d *state) AppendBinary(b []byte) ([]byte, error) {
+	switch d.dsbyte {
+	case dsbyteKeccak:
+		b = append(b, magicKeccak...)
+	default:
+		panic("unknown dsbyte")
+	}
+	// rate is at most 168, and n is at most rate.
+	b = append(b, byte(d.rate))
+	b = append(b, d.a[:]...)
+	b = append(b, byte(d.n), byte(d.state))
+	return b, nil
+}
+
+func (d *state) UnmarshalBinary(b []byte) error {
+	if len(b) != marshaledSize {
+		return errors.New("sha3: invalid hash state")
+	}
+
+	magic := string(b[:len(magicKeccak)])
+	b = b[len(magicKeccak):]
+	switch {
+	case magic == magicKeccak && d.dsbyte == dsbyteKeccak:
+	default:
+		return errors.New("sha3: invalid hash state identifier")
+	}
+
+	rate := int(b[0])
+	b = b[1:]
+	if rate != d.rate {
+		return errors.New("sha3: invalid hash state function")
+	}
+
+	copy(d.a[:], b)
+	b = b[len(d.a):]
+
+	n, state := int(b[0]), spongeDirection(b[1])
+	if n > d.rate {
+		return errors.New("sha3: invalid hash state")
+	}
+	d.n = n
+	if state != spongeAbsorbing && state != spongeSqueezing {
+		return errors.New("sha3: invalid hash state")
+	}
+	d.state = state
+
+	return nil
+}