ref: ed3a576e8b103032b659febc5d3c62565c9cf7d7
dir: /sys/src/libsec/port/aes_gcm.c/
#include "os.h"
#include <libsec.h>
static void
load128(uchar b[16], ulong W[4])
{
W[0] = (ulong)b[15] | (ulong)b[14]<<8 | (ulong)b[13]<<16 | (ulong)b[12]<<24;
W[1] = (ulong)b[11] | (ulong)b[10]<<8 | (ulong)b[ 9]<<16 | (ulong)b[ 8]<<24;
W[2] = (ulong)b[ 7] | (ulong)b[ 6]<<8 | (ulong)b[ 5]<<16 | (ulong)b[ 4]<<24;
W[3] = (ulong)b[ 3] | (ulong)b[ 2]<<8 | (ulong)b[ 1]<<16 | (ulong)b[ 0]<<24;
}
static void
store128(ulong W[4], uchar b[16])
{
b[15] = W[0], b[14] = W[0]>>8, b[13] = W[0]>>16, b[12] = W[0]>>24;
b[11] = W[1], b[10] = W[1]>>8, b[ 9] = W[1]>>16, b[ 8] = W[1]>>24;
b[ 7] = W[2], b[ 6] = W[2]>>8, b[ 5] = W[2]>>16, b[ 4] = W[2]>>24;
b[ 3] = W[3], b[ 2] = W[3]>>8, b[ 1] = W[3]>>16, b[ 0] = W[3]>>24;
}
static void
gfmul(ulong X[4], ulong Y[4], ulong Z[4])
{
long m, i;
Z[0] = Z[1] = Z[2] = Z[3] = 0;
for(i=127; i>=0; i--){
m = ((long)Y[i>>5] << 31-(i&31)) >> 31;
Z[0] ^= X[0] & m;
Z[1] ^= X[1] & m;
Z[2] ^= X[2] & m;
Z[3] ^= X[3] & m;
m = ((long)X[0]<<31) >> 31;
X[0] = X[0]>>1 | X[1]<<31;
X[1] = X[1]>>1 | X[2]<<31;
X[2] = X[2]>>1 | X[3]<<31;
X[3] = X[3]>>1 ^ (0xE1000000 & m);
}
}
static void
prepareM(ulong H[4], ulong M[16][256][4])
{
ulong X[4], i, j;
for(i=0; i<16; i++){
for(j=0; j<256; j++){
X[0] = X[1] = X[2] = X[3] = 0;
X[i>>2] = j<<((i&3)<<3);
gfmul(X, H, M[i][j]);
}
}
}
static void
ghash1(AESGCMstate *s, ulong X[4], ulong Y[4])
{
ulong *Xi, i;
X[0] ^= Y[0], X[1] ^= Y[1], X[2] ^= Y[2], X[3] ^= Y[3];
if(0){
gfmul(X, s->H, Y);
return;
}
Y[0] = Y[1] = Y[2] = Y[3] = 0;
for(i=0; i<16; i++){
Xi = s->M[i][(X[i>>2]>>((i&3)<<3))&0xFF];
Y[0] ^= Xi[0];
Y[1] ^= Xi[1];
Y[2] ^= Xi[2];
Y[3] ^= Xi[3];
}
}
static void
ghashn(AESGCMstate *s, uchar *dat, ulong len, ulong Y[4])
{
uchar tmp[16];
ulong X[4];
while(len >= 16){
load128(dat, X);
ghash1(s, X, Y);
dat += 16, len -= 16;
}
if(len > 0){
memmove(tmp, dat, len);
memset(tmp+len, 0, 16-len);
load128(tmp, X);
ghash1(s, X, Y);
}
}
static ulong
aesxctr1(AESstate *s, uchar ctr[AESbsize], uchar *dat, ulong len)
{
uchar tmp[AESbsize];
ulong i;
aes_encrypt(s->ekey, s->rounds, ctr, tmp);
if(len > AESbsize)
len = AESbsize;
for(i=0; i<len; i++)
dat[i] ^= tmp[i];
return len;
}
static void
aesxctrn(AESstate *s, uchar *dat, ulong len)
{
uchar ctr[AESbsize];
ulong i;
memmove(ctr, s->ivec, AESbsize);
while(len > 0){
for(i=AESbsize-1; i>=AESbsize-4; i--)
if(++ctr[i] != 0)
break;
if(aesxctr1(s, ctr, dat, len) < AESbsize)
break;
dat += AESbsize;
len -= AESbsize;
}
}
void
aesgcm_setiv(AESGCMstate *s, uchar *iv, int ivlen)
{
if(ivlen == 96/8){
memmove(s->ivec, iv, ivlen);
memset(s->ivec+ivlen, 0, AESbsize-ivlen);
s->ivec[AESbsize-1] = 1;
} else {
ulong L[4], Y[4] = {0};
ghashn(s, iv, ivlen, Y);
L[0] = ivlen << 3;
L[1] = ivlen >> 29;
L[2] = L[3] = 0;
ghash1(s, L, Y);
store128(Y, s->ivec);
}
}
void
setupAESGCMstate(AESGCMstate *s, uchar *key, int keylen, uchar *iv, int ivlen)
{
setupAESstate(s, key, keylen, nil);
memset(s->ivec, 0, AESbsize);
aes_encrypt(s->ekey, s->rounds, s->ivec, s->ivec);
load128(s->ivec, s->H);
memset(s->ivec, 0, AESbsize);
prepareM(s->H, s->M);
if(iv != nil && ivlen > 0)
aesgcm_setiv(s, iv, ivlen);
}
void
aesgcm_encrypt(uchar *dat, ulong ndat, uchar *aad, ulong naad, uchar tag[16], AESGCMstate *s)
{
ulong L[4], Y[4] = {0};
ghashn(s, aad, naad, Y);
aesxctrn(s, dat, ndat);
ghashn(s, dat, ndat, Y);
L[0] = ndat << 3;
L[1] = ndat >> 29;
L[2] = naad << 3;
L[3] = naad >> 29;
ghash1(s, L, Y);
store128(Y, tag);
aesxctr1(s, s->ivec, tag, 16);
}
int
aesgcm_decrypt(uchar *dat, ulong ndat, uchar *aad, ulong naad, uchar tag[16], AESGCMstate *s)
{
ulong L[4], Y[4] = {0};
uchar tmp[16];
ghashn(s, aad, naad, Y);
ghashn(s, dat, ndat, Y);
L[0] = ndat << 3;
L[1] = ndat >> 29;
L[2] = naad << 3;
L[3] = naad >> 29;
ghash1(s, L, Y);
store128(Y, tmp);
aesxctr1(s, s->ivec, tmp, 16);
if(tsmemcmp(tag, tmp, 16) != 0)
return -1;
aesxctrn(s, dat, ndat);
return 0;
}