cipher: s390x, gcm mode ghash #248

.github/workflows/test_s390x.yaml

@@ -39,6 +39,11 @@ jobs:
       env:
         GOARCH: ${{ matrix.arch }}
 
+    - name: Test Cipher
+      run: go test -v -short ./cipher/...
+      env:
+        GOARCH: ${{ matrix.arch }}
+
 #    - name: Test
 #      run: go test -v -short ./...
 #      env:

cipher/gcm.go

@@ -0,0 +1,47 @@
+
+// Copyright 2024 Sun Yimin. All rights reserved.
+// Use of this source code is governed by a MIT-style
+// license that can be found in the LICENSE file.
+
+//go:build purego || !s390x
+
+package cipher
+
+import (
+	_cipher "crypto/cipher"
+)
+
+// A proxy of Golang cipher gcm mode.
+
+// NewGCM returns the given 128-bit, block cipher wrapped in Galois Counter Mode
+// with the standard nonce length.
+//
+// In general, the GHASH operation performed by this implementation of GCM is not constant-time.
+// An exception is when the underlying Block was created by aes.NewCipher
+// on systems with hardware support for AES. See the crypto/aes package documentation for details.
+func NewGCM(cipher _cipher.Block) (_cipher.AEAD, error) {
+	return _cipher.NewGCM(cipher)
+}
+
+// NewGCMWithNonceSize returns the given 128-bit, block cipher wrapped in Galois
+// Counter Mode, which accepts nonces of the given length. The length must not
+// be zero.
+//
+// Only use this function if you require compatibility with an existing
+// cryptosystem that uses non-standard nonce lengths. All other users should use
+// NewGCM, which is faster and more resistant to misuse.
+func NewGCMWithNonceSize(cipher _cipher.Block, size int) (_cipher.AEAD, error) {
+	return _cipher.NewGCMWithNonceSize(cipher, size)
+}
+
+// NewGCMWithTagSize returns the given 128-bit, block cipher wrapped in Galois
+// Counter Mode, which generates tags with the given length.
+//
+// Tag sizes between 12 and 16 bytes are allowed.
+//
+// Only use this function if you require compatibility with an existing
+// cryptosystem that uses non-standard tag lengths. All other users should use
+// NewGCM, which is more resistant to misuse.
+func NewGCMWithTagSize(cipher _cipher.Block, tagSize int) (_cipher.AEAD, error) {
+	return _cipher.NewGCMWithTagSize(cipher, tagSize)
+}

cipher/gcm_s390x.go

@@ -0,0 +1,285 @@
+// Copyright 2024 Sun Yimin. All rights reserved.
+// Use of this source code is governed by a MIT-style
+// license that can be found in the LICENSE file.
+
+//go:build !purego
+
+package cipher
+
+import (
+	_cipher "crypto/cipher"
+	_subtle "crypto/subtle"
+	"encoding/binary"
+	"errors"
+
+	"github.com/emmansun/gmsm/internal/alias"
+	"github.com/emmansun/gmsm/internal/subtle"
+)
+
+// gcmAble is an interface implemented by ciphers that have a specific optimized
+// implementation of GCM, like crypto/aes. NewGCM will check for this interface
+// and return the specific AEAD if found.
+type gcmAble interface {
+	NewGCM(nonceSize, tagSize int) (_cipher.AEAD, error)
+}
+
+// gcmHashKey represents the 16-byte hash key required by the GHASH algorithm.
+type gcmHashKey [16]byte
+
+// gcm represents a Galois Counter Mode with a specific key. See
+// https://csrc.nist.gov/groups/ST/toolkit/BCM/documents/proposedmodes/gcm/gcm-revised-spec.pdf
+type gcm struct {
+	cipher    _cipher.Block
+	nonceSize int
+	tagSize   int
+	hashKey   gcmHashKey
+}
+
+// NewGCM returns the given 128-bit, block cipher wrapped in Galois Counter Mode
+// with the standard nonce length.
+//
+// In general, the GHASH operation performed by this implementation of GCM is not constant-time.
+// An exception is when the underlying Block was created by aes.NewCipher
+// on systems with hardware support for AES. See the crypto/aes package documentation for details.
+func NewGCM(cipher _cipher.Block) (_cipher.AEAD, error) {
+	return newGCMWithNonceAndTagSize(cipher, gcmStandardNonceSize, gcmTagSize)
+}
+
+// NewGCMWithNonceSize returns the given 128-bit, block cipher wrapped in Galois
+// Counter Mode, which accepts nonces of the given length. The length must not
+// be zero.
+//
+// Only use this function if you require compatibility with an existing
+// cryptosystem that uses non-standard nonce lengths. All other users should use
+// NewGCM, which is faster and more resistant to misuse.
+func NewGCMWithNonceSize(cipher _cipher.Block, size int) (_cipher.AEAD, error) {
+	return newGCMWithNonceAndTagSize(cipher, size, gcmTagSize)
+}
+
+// NewGCMWithTagSize returns the given 128-bit, block cipher wrapped in Galois
+// Counter Mode, which generates tags with the given length.
+//
+// Tag sizes between 12 and 16 bytes are allowed.
+//
+// Only use this function if you require compatibility with an existing
+// cryptosystem that uses non-standard tag lengths. All other users should use
+// NewGCM, which is more resistant to misuse.
+func NewGCMWithTagSize(cipher _cipher.Block, tagSize int) (_cipher.AEAD, error) {
+	return newGCMWithNonceAndTagSize(cipher, gcmStandardNonceSize, tagSize)
+}
+
+func newGCMWithNonceAndTagSize(cipher _cipher.Block, nonceSize, tagSize int) (_cipher.AEAD, error) {
+	if tagSize < gcmMinimumTagSize || tagSize > gcmBlockSize {
+		return nil, errors.New("cipher: incorrect tag size given to GCM")
+	}
+
+	if nonceSize <= 0 {
+		return nil, errors.New("cipher: the nonce can't have zero length, or the security of the key will be immediately compromised")
+	}
+
+	if cipher, ok := cipher.(gcmAble); ok {
+		return cipher.NewGCM(nonceSize, tagSize)
+	}
+
+	if cipher.BlockSize() != gcmBlockSize {
+		return nil, errors.New("cipher: NewGCM requires 128-bit block cipher")
+	}
+
+	var hk gcmHashKey
+	cipher.Encrypt(hk[:], hk[:])
+
+	g := &gcm{cipher: cipher, nonceSize: nonceSize, tagSize: tagSize, hashKey: hk}
+
+	return g, nil
+}
+
+const (
+	gcmBlockSize         = 16
+	gcmTagSize           = 16
+	gcmMinimumTagSize    = 12 // NIST SP 800-38D recommends tags with 12 or more bytes.
+	gcmStandardNonceSize = 12
+)
+
+func (g *gcm) NonceSize() int {
+	return g.nonceSize
+}
+
+func (g *gcm) Overhead() int {
+	return g.tagSize
+}
+
+// gcmCount represents a 16-byte big-endian count value.
+type gcmCount [16]byte
+
+// inc increments the rightmost 32-bits of the count value by 1.
+func (x *gcmCount) inc() {
+	binary.BigEndian.PutUint32(x[len(x)-4:], binary.BigEndian.Uint32(x[len(x)-4:])+1)
+}
+
+// ghash uses the GHASH algorithm to hash data with the given key. The initial
+// hash value is given by hash which will be updated with the new hash value.
+// The length of data must be a multiple of 16-bytes.
+//
+//go:noescape
+func ghash(key *gcmHashKey, hash *[16]byte, data []byte)
+
+// paddedGHASH pads data with zeroes until its length is a multiple of
+// 16-bytes. It then calculates a new value for hash using the GHASH algorithm.
+func (g *gcm) paddedGHASH(hash *[16]byte, data []byte) {
+	siz := len(data) &^ 0xf // align size to 16-bytes
+	if siz > 0 {
+		ghash(&g.hashKey, hash, data[:siz])
+		data = data[siz:]
+	}
+	if len(data) > 0 {
+		var s [16]byte
+		copy(s[:], data)
+		ghash(&g.hashKey, hash, s[:])
+	}
+}
+
+// gcmLengths writes len0 || len1 as big-endian values to a 16-byte array.
+func gcmLengths(len0, len1 uint64) [16]byte {
+	v := [16]byte{}
+	binary.BigEndian.PutUint64(v[0:], len0)
+	binary.BigEndian.PutUint64(v[8:], len1)
+	return v
+}
+
+// auth calculates GHASH(ciphertext, additionalData), masks the result with
+// tagMask and writes the result to out.
+func (g *gcm) auth(out, ciphertext, additionalData []byte, tagMask *[gcmTagSize]byte) {
+	var hash [16]byte
+	g.paddedGHASH(&hash, additionalData)
+	g.paddedGHASH(&hash, ciphertext)
+	lens := gcmLengths(uint64(len(additionalData))*8, uint64(len(ciphertext))*8)
+	g.paddedGHASH(&hash, lens[:])
+
+	copy(out, hash[:])
+	for i := range out {
+		out[i] ^= tagMask[i]
+	}
+}
+
+// deriveCounter computes the initial GCM counter state from the given nonce.
+// See NIST SP 800-38D, section 7.1. This assumes that counter is filled with
+// zeros on entry.
+func (g *gcm) deriveCounter(nonce []byte) gcmCount {
+	// GCM has two modes of operation with respect to the initial counter
+	// state: a "fast path" for 96-bit (12-byte) nonces, and a "slow path"
+	// for nonces of other lengths. For a 96-bit nonce, the nonce, along
+	// with a four-byte big-endian counter starting at one, is used
+	// directly as the starting counter. For other nonce sizes, the counter
+	// is computed by passing it through the GHASH function.
+	var counter gcmCount
+	if len(nonce) == gcmStandardNonceSize {
+		copy(counter[:], nonce)
+		counter[gcmBlockSize-1] = 1
+	} else {
+		var hash [16]byte
+		g.paddedGHASH(&hash, nonce)
+		lens := gcmLengths(0, uint64(len(nonce))*8)
+		g.paddedGHASH(&hash, lens[:])
+		copy(counter[:], hash[:])
+	}
+	return counter
+}
+
+// counterCrypt crypts in to out using g.cipher in counter mode.
+func (g *gcm) counterCrypt(out, in []byte, counter *gcmCount) {
+	var mask [gcmBlockSize]byte
+
+	for len(in) >= gcmBlockSize {
+		g.cipher.Encrypt(mask[:], counter[:])
+		counter.inc()
+
+		subtle.XORBytes(out, in, mask[:])
+		out = out[gcmBlockSize:]
+		in = in[gcmBlockSize:]
+	}
+
+	if len(in) > 0 {
+		g.cipher.Encrypt(mask[:], counter[:])
+		counter.inc()
+		subtle.XORBytes(out, in, mask[:])
+	}
+}
+
+// Seal encrypts and authenticates plaintext. See the cipher.AEAD interface for
+// details.
+func (g *gcm) Seal(dst, nonce, plaintext, data []byte) []byte {
+	if len(nonce) != g.nonceSize {
+		panic("crypto/cipher: incorrect nonce length given to GCM")
+	}
+	if uint64(len(plaintext)) > ((1<<32)-2)*uint64(g.cipher.BlockSize()) {
+		panic("crypto/cipher: message too large for GCM")
+	}
+
+	ret, out := alias.SliceForAppend(dst, len(plaintext)+g.tagSize)
+	if alias.InexactOverlap(out[:len(plaintext)], plaintext) {
+		panic("crypto/cipher: invalid buffer overlap")
+	}
+
+	counter := g.deriveCounter(nonce)
+
+	var tagMask [gcmBlockSize]byte
+	g.cipher.Encrypt(tagMask[:], counter[:])
+	counter.inc()
+
+	var tagOut [gcmTagSize]byte
+	g.counterCrypt(out, plaintext, &counter)
+	g.auth(tagOut[:], out[:len(plaintext)], data, &tagMask)
+	copy(out[len(plaintext):], tagOut[:])
+
+	return ret
+}
+
+// Open authenticates and decrypts ciphertext. See the cipher.AEAD interface
+// for details.
+func (g *gcm) Open(dst, nonce, ciphertext, data []byte) ([]byte, error) {
+	if len(nonce) != g.nonceSize {
+		panic("crypto/cipher: incorrect nonce length given to GCM")
+	}
+	// Sanity check to prevent the authentication from always succeeding if an implementation
+	// leaves tagSize uninitialized, for example.
+	if g.tagSize < gcmMinimumTagSize {
+		panic("crypto/cipher: incorrect GCM tag size")
+	}
+	if len(ciphertext) < g.tagSize {
+		return nil, errOpen
+	}
+	if uint64(len(ciphertext)) > ((1<<32)-2)*uint64(g.cipher.BlockSize())+uint64(g.tagSize) {
+		return nil, errOpen
+	}
+
+	tag := ciphertext[len(ciphertext)-g.tagSize:]
+	ciphertext = ciphertext[:len(ciphertext)-g.tagSize]
+
+	counter := g.deriveCounter(nonce)
+
+	var tagMask [gcmBlockSize]byte
+	g.cipher.Encrypt(tagMask[:], counter[:])
+	counter.inc()
+
+	var expectedTag [gcmTagSize]byte
+	g.auth(expectedTag[:], ciphertext, data, &tagMask)
+
+	ret, out := alias.SliceForAppend(dst, len(ciphertext))
+	if alias.InexactOverlap(out, ciphertext) {
+		panic("crypto/cipher: invalid buffer overlap")
+	}
+
+	if _subtle.ConstantTimeCompare(expectedTag[:g.tagSize], tag) != 1 {
+		// The AESNI code decrypts and authenticates concurrently, and
+		// so overwrites dst in the event of a tag mismatch. That
+		// behavior is mimicked here in order to be consistent across
+		// platforms.
+		for i := range out {
+			out[i] = 0
+		}
+		return nil, errOpen
+	}
+
+	g.counterCrypt(out, ciphertext, &counter)
+	return ret, nil
+}

cipher/gcm_s390x.s

@@ -0,0 +1,25 @@
+
+// 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.
+
+//go:build !purego
+
+#include "textflag.h"
+
+// func ghash(key *gcmHashKey, hash *[16]byte, data []byte)
+TEXT ·ghash(SB),NOSPLIT,$32-40
+	MOVD    $65, R0 // GHASH function code
+	MOVD	key+0(FP), R2
+	LMG	(R2), R6, R7
+	MOVD	hash+8(FP), R8
+	LMG	(R8), R4, R5
+	MOVD	$params-32(SP), R1
+	STMG	R4, R7, (R1)
+	LMG	data+16(FP), R2, R3 // R2=base, R3=len
+loop:
+	WORD    $0xB93E0002 // compute intermediate message digest (KIMD)
+	BVS     loop        // branch back if interrupted
+	MVC     $16, (R1), (R8)
+	MOVD	$0, R0
+	RET