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pkg/cryptstate, pkg/cryptstate/ocb2: split OCB2 implementation out into its own package.

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This commit is contained in:
Mikkel Krautz 2012-12-01 11:42:02 +01:00
parent 51eee0abd0
commit 0f058d3b76
4 changed files with 196 additions and 201 deletions
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135
pkg/cryptstate/cryptstate.go
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@ -10,6 +10,7 @@ import (
"crypto/cipher"
"crypto/rand"
"errors"
"mumbleapp.com/grumble/pkg/cryptstate/ocb2"
"time"
)
@ -175,7 +176,7 @@ func (cs *CryptState) Decrypt(dst, src []byte) (err error) {
}
}
cs.OCBDecrypt(dst[0:], src[4:], cs.DecryptIV[0:], tag[0:])
ocb2.Decrypt(cs.cipher, dst[0:], src[4:], cs.DecryptIV[0:], tag[0:])
for i := 0; i < 3; i++ {
if tag[i] != src[i+1] {
@ -225,7 +226,7 @@ func (cs *CryptState) Encrypt(dst, src []byte) {
}
}
cs.OCBEncrypt(dst[4:], src, cs.EncryptIV[0:], tag[0:])
ocb2.Encrypt(cs.cipher, dst[4:], src, cs.EncryptIV[0:], tag[0:])
dst[0] = cs.EncryptIV[0]
dst[1] = tag[0]
@ -233,132 +234,4 @@ func (cs *CryptState) Encrypt(dst, src []byte) {
dst[3] = tag[2]
return
}
func zeros(block []byte) {
for i := range block {
block[i] = 0
}
}
func xor(dst []byte, a []byte, b []byte) {
for i := 0; i < aes.BlockSize; i++ {
dst[i] = a[i] ^ b[i]
}
}
func times2(block []byte) {
carry := (block[0] >> 7) & 0x1
for i := 0; i < aes.BlockSize-1; i++ {
block[i] = (block[i] << 1) | ((block[i+1] >> 7) & 0x1)
}
block[aes.BlockSize-1] = (block[aes.BlockSize-1] << 1) ^ (carry * 135)
}
func times3(block []byte) {
carry := (block[0] >> 7) & 0x1
for i := 0; i < aes.BlockSize-1; i++ {
block[i] ^= (block[i] << 1) | ((block[i+1] >> 7) & 0x1)
}
block[aes.BlockSize-1] ^= ((block[aes.BlockSize-1] << 1) ^ (carry * 135))
}
func (cs *CryptState) OCBEncrypt(dst []byte, src []byte, nonce []byte, tag []byte) (err error) {
var delta [aes.BlockSize]byte
var checksum [aes.BlockSize]byte
var tmp [aes.BlockSize]byte
var pad [aes.BlockSize]byte
off := 0
cs.cipher.Encrypt(delta[0:], nonce[0:])
zeros(checksum[0:])
remain := len(src)
for remain > aes.BlockSize {
times2(delta[0:])
xor(tmp[0:], delta[0:], src[off:off+aes.BlockSize])
cs.cipher.Encrypt(tmp[0:], tmp[0:])
xor(dst[off:off+aes.BlockSize], delta[0:], tmp[0:])
xor(checksum[0:], checksum[0:], src[off:off+aes.BlockSize])
remain -= aes.BlockSize
off += aes.BlockSize
}
times2(delta[0:])
zeros(tmp[0:])
num := remain * 8
tmp[aes.BlockSize-2] = uint8((uint32(num) >> 8) & 0xff)
tmp[aes.BlockSize-1] = uint8(num & 0xff)
xor(tmp[0:], tmp[0:], delta[0:])
cs.cipher.Encrypt(pad[0:], tmp[0:])
copied := copy(tmp[0:], src[off:])
if copied != remain {
err = errors.New("Copy failed")
return
}
if copy(tmp[copied:], pad[copied:]) != (aes.BlockSize - remain) {
err = errors.New("Copy failed")
return
}
xor(checksum[0:], checksum[0:], tmp[0:])
xor(tmp[0:], pad[0:], tmp[0:])
if copy(dst[off:], tmp[0:]) != remain {
err = errors.New("Copy failed")
return
}
times3(delta[0:])
xor(tmp[0:], delta[0:], checksum[0:])
cs.cipher.Encrypt(tag[0:], tmp[0:])
return
}
func (cs *CryptState) OCBDecrypt(plain []byte, encrypted []byte, nonce []byte, tag []byte) (err error) {
var checksum [aes.BlockSize]byte
var delta [aes.BlockSize]byte
var tmp [aes.BlockSize]byte
var pad [aes.BlockSize]byte
off := 0
cs.cipher.Encrypt(delta[0:], nonce[0:])
zeros(checksum[0:])
remain := len(encrypted)
for remain > aes.BlockSize {
times2(delta[0:])
xor(tmp[0:], delta[0:], encrypted[off:off+aes.BlockSize])
cs.cipher.Decrypt(tmp[0:], tmp[0:])
xor(plain[off:off+aes.BlockSize], delta[0:], tmp[0:])
xor(checksum[0:], checksum[0:], plain[off:off+aes.BlockSize])
off += aes.BlockSize
remain -= aes.BlockSize
}
times2(delta[0:])
zeros(tmp[0:])
num := remain * 8
tmp[aes.BlockSize-2] = uint8((uint32(num) >> 8) & 0xff)
tmp[aes.BlockSize-1] = uint8(num & 0xff)
xor(tmp[0:], tmp[0:], delta[0:])
cs.cipher.Encrypt(pad[0:], tmp[0:])
zeros(tmp[0:])
copied := copy(tmp[0:remain], encrypted[off:off+remain])
if copied != remain {
err = errors.New("Copy failed")
return
}
xor(tmp[0:], tmp[0:], pad[0:])
xor(checksum[0:], checksum[0:], tmp[0:])
copied = copy(plain[off:off+remain], tmp[0:remain])
if copied != remain {
err = errors.New("Copy failed")
return
}
times3(delta[0:])
xor(tmp[0:], delta[0:], checksum[0:])
cs.cipher.Encrypt(tag[0:], tmp[0:])
return
}
}