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// // 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 (
// gcmblock_size = 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)*block_size {
// panic("crypto/cipher: message too large for GCM")
// }
// var counter, tagMask [gcmblock_size]byte
// if len(nonce) == gcmStandardNonceSize {
// // Init counter to nonce||1
// copy(counter[:], nonce)
// counter[gcmblock_size-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(block_size)+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 [gcmblock_size]byte
// if len(nonce) == gcmStandardNonceSize {
// // Init counter to nonce||1
// copy(counter[:], nonce)
// counter[gcmblock_size-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
// }