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libsec: rewrite aex_xts_encrypt()/aes_xts_decrypt()

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the previous implementation was not portable at all, assuming
little endian in gf_mulx() and that one can cast unaligned
pointers to ulong in xor128(). also the error code is likely
to be ignored, so better abort() when the length is not a
multiple of the AES block size.

we also pass in full AESstate structures now instead of
the expanded key longs, so that we do not need to hardcode
the number of rounds. this allows each indiviaul keys to
be bigger than 128 bit.
This commit is contained in:
cinap_lenrek 2017-10-29 21:49:24 +01:00
parent 77757dbdb1
commit c021390e21
3 changed files with 75 additions and 62 deletions
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4
sys/include/ape/libsec.h
View file

@ -509,8 +509,8 @@ uchar *readcert(char *filename, int *pcertlen);
PEMChain*readcertchain(char *filename);
/* aes_xts.c */
int aes_xts_encrypt(ulong tweak[], ulong ecb[], uvlong sectorNumber, uchar *input, uchar *output, ulong len) ;
int aes_xts_decrypt(ulong tweak[], ulong ecb[], uvlong sectorNumber, uchar *input, uchar *output, ulong len);
void aes_xts_encrypt(AESstate *tweak, AESstate *ecb, uvlong sectorNumber, uchar *input, uchar *output, ulong len);
void aes_xts_decrypt(AESstate *tweak, AESstate *ecb, uvlong sectorNumber, uchar *input, uchar *output, ulong len);
typedef struct ECpoint{
int inf;

4
sys/include/libsec.h
View file

@ -502,8 +502,8 @@ uchar *readcert(char *filename, int *pcertlen);
PEMChain*readcertchain(char *filename);
/* aes_xts.c */
int aes_xts_encrypt(ulong tweak[], ulong ecb[], uvlong sectorNumber, uchar *input, uchar *output, ulong len) ;
int aes_xts_decrypt(ulong tweak[], ulong ecb[], uvlong sectorNumber, uchar *input, uchar *output, ulong len);
void aes_xts_encrypt(AESstate *tweak, AESstate *ecb, uvlong sectorNumber, uchar *input, uchar *output, ulong len);
void aes_xts_decrypt(AESstate *tweak, AESstate *ecb, uvlong sectorNumber, uchar *input, uchar *output, ulong len);
typedef struct ECpoint{
int inf;

129
sys/src/libsec/port/aes_xts.c
View file

@ -1,70 +1,83 @@
// Author Taru Karttunen <taruti@taruti.net>
// This file can be used as both Public Domain or Creative Commons CC0.
#include "os.h"
#include <libsec.h>
/* little-endian data order */
#define GET4(p) ((p)[0]|((p)[1]<<8)|((p)[2]<<16)|((p)[3]<<24))
#define PUT4(p,v) (p)[0]=(v);(p)[1]=(v)>>8;(p)[2]=(v)>>16;(p)[3]=(v)>>24
static void
xor128(uchar *o, uchar *i1, uchar *i2) {
((ulong*)o)[0] = ((ulong*)i1)[0] ^ ((ulong*)i2)[0];
((ulong*)o)[1] = ((ulong*)i1)[1] ^ ((ulong*)i2)[1];
((ulong*)o)[2] = ((ulong*)i1)[2] ^ ((ulong*)i2)[2];
((ulong*)o)[3] = ((ulong*)i1)[3] ^ ((ulong*)i2)[3];
gf_mulx(uchar *x)
{
ulong t0, t1, t2, t3, t4;
t0 = GET4(x);
t1 = GET4(x+4);
t2 = GET4(x+8);
t3 = GET4(x+12);
t4 = (t3 >> 31);
t3 = (t3 << 1) | (t2 >> 31);
t2 = (t2 << 1) | (t1 >> 31);
t1 = (t1 << 1) | (t0 >> 31);
t0 = (t0 << 1) ^ (t4*135);
PUT4(x, t0);
PUT4(x+4, t1);
PUT4(x+8, t2);
PUT4(x+12, t3);
}
static void
gf_mulx(uchar *x) {
ulong t = ((((ulong*)(x))[3] & 0x80000000u) ? 0x00000087u : 0);;
((ulong*)(x))[3] = (((ulong*)(x))[3] << 1) | (((ulong*)(x))[2] & 0x80000000u ? 1 : 0);
((ulong*)(x))[2] = (((ulong*)(x))[2] << 1) | (((ulong*)(x))[1] & 0x80000000u ? 1 : 0);
((ulong*)(x))[1] = (((ulong*)(x))[1] << 1) | (((ulong*)(x))[0] & 0x80000000u ? 1 : 0);
((ulong*)(x))[0] = (((ulong*)(x))[0] << 1) ^ t;
}
int
aes_xts_encrypt(ulong tweak[], ulong ecb[], uvlong sectorNumber, uchar *input, uchar *output, ulong len) {
uchar T[16], x[16];
xor128(uchar *o, uchar *i1, uchar *i2)
{
int i;
if(len % 16 != 0)
return -1;
for(i=0; i<AESbsize; i++) {
T[i] = (uchar)(sectorNumber & 0xFF);
sectorNumber = sectorNumber >> 8;
}
aes_encrypt(tweak, 10, T, T);
for (i=0; i<len; i+=AESbsize) {
xor128(&x[0], &input[i], &T[0]);
aes_encrypt(ecb, 10, x, x);
xor128(&output[i], &x[0], &T[0]);
gf_mulx(&T[0]);
}
return 0;
for(i=0; i<16; i++)
o[i] = i1[i] ^ i2[i];
}
int
aes_xts_decrypt(ulong tweak[], ulong ecb[], uvlong sectorNumber, uchar *input, uchar *output, ulong len) {
uchar T[16], x[16];
int i;
if(len % 16 != 0)
return -1;
for(i=0; i<AESbsize; i++) {
T[i] = (uchar)(sectorNumber & 0xFF);
sectorNumber = sectorNumber >> 8;
}
aes_encrypt(tweak, 10, T, T);
for (i=0; i<len; i+=AESbsize) {
xor128(&x[0], &input[i], &T[0]);
aes_decrypt(ecb, 10, x, x);
xor128(&output[i], &x[0], &T[0]);
gf_mulx(&T[0]);
}
return 0;
static void
setupT(AESstate *tweak, uvlong sectorNumber, uchar T[AESbsize])
{
PUT4(T+0, (ulong)sectorNumber), sectorNumber >>= 32;
PUT4(T+4, (ulong)sectorNumber);
PUT4(T+8, 0);
PUT4(T+12, 0);
aes_encrypt(tweak->ekey, tweak->rounds, T, T);
}
void
aes_xts_encrypt(AESstate *tweak, AESstate *ecb,
uvlong sectorNumber, uchar *input, uchar *output, ulong len)
{
uchar T[AESbsize], x[AESbsize];
if(len % AESbsize)
abort();
setupT(tweak, sectorNumber, T);
for (; len > 0; len -= AESbsize, input += AESbsize, output += AESbsize) {
xor128(x, input, T);
aes_encrypt(ecb->ekey, ecb->rounds, x, x);
xor128(output, x, T);
gf_mulx(T);
}
}
void
aes_xts_decrypt(AESstate *tweak, AESstate *ecb,
uvlong sectorNumber, uchar *input, uchar *output, ulong len)
{
uchar T[AESbsize], x[AESbsize];
if(len % AESbsize)
abort();
setupT(tweak, sectorNumber, T);
for (; len > 0; len -= AESbsize, input += AESbsize, output += AESbsize) {
xor128(x, input, T);
aes_decrypt(ecb->dkey, ecb->rounds, x, x);
xor128(output, x, T);
gf_mulx(T);
}
}