1 files changed, 186 insertions, 0 deletions
diff --git a/src/crypto/aes/aes_gcm.go b/src/crypto/aes/aes_gcm.go
new file mode 100644
index 0000000..f77d279
--- /dev/null
+++ b/src/crypto/aes/aes_gcm.go
@@ -0,0 +1,186 @@
+// Copyright 2015 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 amd64 || arm64
+
+package aes
+
+import (
+	"crypto/cipher"
+	"crypto/internal/alias"
+	"crypto/subtle"
+	"errors"
+)
+
+// The following functions are defined in gcm_*.s.
+
+//go:noescape
+func gcmAesInit(productTable *[256]byte, ks []uint32)
+
+//go:noescape
+func gcmAesData(productTable *[256]byte, data []byte, T *[16]byte)
+
+//go:noescape
+func gcmAesEnc(productTable *[256]byte, dst, src []byte, ctr, T *[16]byte, ks []uint32)
+
+//go:noescape
+func gcmAesDec(productTable *[256]byte, dst, src []byte, ctr, T *[16]byte, ks []uint32)
+
+//go:noescape
+func gcmAesFinish(productTable *[256]byte, tagMask, T *[16]byte, pLen, dLen uint64)
+
+const (
+	gcmBlockSize         = 16
+	gcmTagSize           = 16
+	gcmMinimumTagSize    = 12 // NIST SP 800-38D recommends tags with 12 or more bytes.
+	gcmStandardNonceSize = 12
+)
+
+var errOpen = errors.New("cipher: message authentication failed")
+
+// Assert that aesCipherGCM implements the gcmAble interface.
+var _ gcmAble = (*aesCipherGCM)(nil)
+
+// NewGCM returns the AES cipher wrapped in Galois Counter Mode. This is only
+// called by crypto/cipher.NewGCM via the gcmAble interface.
+func (c *aesCipherGCM) NewGCM(nonceSize, tagSize int) (cipher.AEAD, error) {
+	g := &gcmAsm{ks: c.enc, nonceSize: nonceSize, tagSize: tagSize}
+	gcmAesInit(&g.productTable, g.ks)
+	return g, nil
+}
+
+type gcmAsm struct {
+	// ks is the key schedule, the length of which depends on the size of
+	// the AES key.
+	ks []uint32
+	// productTable contains pre-computed multiples of the binary-field
+	// element used in GHASH.
+	productTable [256]byte
+	// nonceSize contains the expected size of the nonce, in bytes.
+	nonceSize int
+	// tagSize contains the size of the tag, in bytes.
+	tagSize int
+}
+
+func (g *gcmAsm) NonceSize() int {
+	return g.nonceSize
+}
+
+func (g *gcmAsm) Overhead() int {
+	return g.tagSize
+}
+
+// sliceForAppend takes a slice and a requested number of bytes. It returns a
+// slice with the contents of the given slice followed by that many bytes and a
+// second slice that aliases into it and contains only the extra bytes. If the
+// original slice has sufficient capacity then no allocation is performed.
+func sliceForAppend(in []byte, n int) (head, tail []byte) {
+	if total := len(in) + n; cap(in) >= total {
+		head = in[:total]
+	} else {
+		head = make([]byte, total)
+		copy(head, in)
+	}
+	tail = head[len(in):]
+	return
+}
+
+// Seal encrypts and authenticates plaintext. See the cipher.AEAD interface for
+// details.
+func (g *gcmAsm) 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)*BlockSize {
+		panic("crypto/cipher: message too large for GCM")
+	}
+
+	var counter, tagMask [gcmBlockSize]byte
+
+	if len(nonce) == gcmStandardNonceSize {
+		// Init counter to nonce||1
+		copy(counter[:], nonce)
+		counter[gcmBlockSize-1] = 1
+	} else {
+		// Otherwise counter = GHASH(nonce)
+		gcmAesData(&g.productTable, nonce, &counter)
+		gcmAesFinish(&g.productTable, &tagMask, &counter, uint64(len(nonce)), uint64(0))
+	}
+
+	encryptBlockAsm(len(g.ks)/4-1, &g.ks[0], &tagMask[0], &counter[0])
+
+	var tagOut [gcmTagSize]byte
+	gcmAesData(&g.productTable, data, &tagOut)
+
+	ret, out := sliceForAppend(dst, len(plaintext)+g.tagSize)
+	if alias.InexactOverlap(out[:len(plaintext)], plaintext) {
+		panic("crypto/cipher: invalid buffer overlap")
+	}
+	if len(plaintext) > 0 {
+		gcmAesEnc(&g.productTable, out, plaintext, &counter, &tagOut, g.ks)
+	}
+	gcmAesFinish(&g.productTable, &tagMask, &tagOut, uint64(len(plaintext)), uint64(len(data)))
+	copy(out[len(plaintext):], tagOut[:])
+
+	return ret
+}
+
+// Open authenticates and decrypts ciphertext. See the cipher.AEAD interface
+// for details.
+func (g *gcmAsm) 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(BlockSize)+uint64(g.tagSize) {
+		return nil, errOpen
+	}
+
+	tag := ciphertext[len(ciphertext)-g.tagSize:]
+	ciphertext = ciphertext[:len(ciphertext)-g.tagSize]
+
+	// See GCM spec, section 7.1.
+	var counter, tagMask [gcmBlockSize]byte
+
+	if len(nonce) == gcmStandardNonceSize {
+		// Init counter to nonce||1
+		copy(counter[:], nonce)
+		counter[gcmBlockSize-1] = 1
+	} else {
+		// Otherwise counter = GHASH(nonce)
+		gcmAesData(&g.productTable, nonce, &counter)
+		gcmAesFinish(&g.productTable, &tagMask, &counter, uint64(len(nonce)), uint64(0))
+	}
+
+	encryptBlockAsm(len(g.ks)/4-1, &g.ks[0], &tagMask[0], &counter[0])
+
+	var expectedTag [gcmTagSize]byte
+	gcmAesData(&g.productTable, data, &expectedTag)
+
+	ret, out := sliceForAppend(dst, len(ciphertext))
+	if alias.InexactOverlap(out, ciphertext) {
+		panic("crypto/cipher: invalid buffer overlap")
+	}
+	if len(ciphertext) > 0 {
+		gcmAesDec(&g.productTable, out, ciphertext, &counter, &expectedTag, g.ks)
+	}
+	gcmAesFinish(&g.productTable, &tagMask, &expectedTag, uint64(len(ciphertext)), uint64(len(data)))
+
+	if subtle.ConstantTimeCompare(expectedTag[:g.tagSize], tag) != 1 {
+		for i := range out {
+			out[i] = 0
+		}
+		return nil, errOpen
+	}
+
+	return ret, nil
+}