Merge branch 'fix/ccm_constant_time' into develop
This closes #73 and closes #76
This commit is contained in:
Steffen Jaeckel
commit
eb26b7efd4
@ -20,7 +20,7 @@
|
||||
/**
|
||||
CCM encrypt/decrypt and produce an authentication tag
|
||||
|
||||
*1 'pt' and 'ct' can both be 'in' or 'out', depending on 'direction'
|
||||
*1 'pt', 'ct' and 'tag' can both be 'in' or 'out', depending on 'direction'
|
||||
|
||||
@param cipher The index of the cipher desired
|
||||
@param key The secret key to use
|
||||
@ -33,8 +33,8 @@
|
||||
@param pt [*1] The plaintext
|
||||
@param ptlen The length of the plaintext (octets)
|
||||
@param ct [*1] The ciphertext
|
||||
@param tag [out] The destination tag
|
||||
@param taglen [in/out] The max size and resulting size of the authentication tag
|
||||
@param tag [*1] The destination tag
|
||||
@param taglen The max size and resulting size of the authentication tag
|
||||
@param direction Encrypt or Decrypt direction (0 or 1)
|
||||
@return CRYPT_OK if successful
|
||||
*/
|
||||
@ -48,10 +48,15 @@ int ccm_memory(int cipher,
|
||||
unsigned char *tag, unsigned long *taglen,
|
||||
int direction)
|
||||
{
|
||||
unsigned char PAD[16], ctr[16], CTRPAD[16], b;
|
||||
unsigned char PAD[16], ctr[16], CTRPAD[16], ptTag[16], b, *pt_real;
|
||||
unsigned char *pt_work = NULL;
|
||||
symmetric_key *skey;
|
||||
int err;
|
||||
unsigned long len, L, x, y, z, CTRlen;
|
||||
#ifdef LTC_FAST
|
||||
LTC_FAST_TYPE fastMask = -1; /* initialize fastMask at all zeroes */
|
||||
#endif
|
||||
unsigned char mask = 0xff; /* initialize mask at all zeroes */
|
||||
|
||||
if (uskey == NULL) {
|
||||
LTC_ARGCHK(key != NULL);
|
||||
@ -65,6 +70,8 @@ int ccm_memory(int cipher,
|
||||
LTC_ARGCHK(tag != NULL);
|
||||
LTC_ARGCHK(taglen != NULL);
|
||||
|
||||
pt_real = pt;
|
||||
|
||||
#ifdef LTC_FAST
|
||||
if (16 % sizeof(LTC_FAST_TYPE)) {
|
||||
return CRYPT_INVALID_ARG;
|
||||
@ -141,6 +148,15 @@ int ccm_memory(int cipher,
|
||||
skey = uskey;
|
||||
}
|
||||
|
||||
/* initialize buffer for pt */
|
||||
if (direction == CCM_DECRYPT) {
|
||||
pt_work = XMALLOC(ptlen);
|
||||
if (pt_work == NULL) {
|
||||
goto error;
|
||||
}
|
||||
pt = pt_work;
|
||||
}
|
||||
|
||||
/* form B_0 == flags | Nonce N | l(m) */
|
||||
x = 0;
|
||||
PAD[x++] = (unsigned char)(((headerlen > 0) ? (1<<6) : 0) |
|
||||
@ -203,13 +219,11 @@ int ccm_memory(int cipher,
|
||||
PAD[x++] ^= header[y];
|
||||
}
|
||||
|
||||
/* remainder? */
|
||||
if (x != 0) {
|
||||
/* remainder */
|
||||
if ((err = cipher_descriptor[cipher].ecb_encrypt(PAD, PAD, skey)) != CRYPT_OK) {
|
||||
goto error;
|
||||
}
|
||||
}
|
||||
}
|
||||
|
||||
/* setup the ctr counter */
|
||||
x = 0;
|
||||
@ -254,7 +268,7 @@ int ccm_memory(int cipher,
|
||||
goto error;
|
||||
}
|
||||
}
|
||||
} else {
|
||||
} else { /* direction == CCM_DECRYPT */
|
||||
for (; y < (ptlen & ~15); y += 16) {
|
||||
/* increment the ctr? */
|
||||
for (z = 15; z > 15-L; z--) {
|
||||
@ -328,18 +342,60 @@ int ccm_memory(int cipher,
|
||||
cipher_descriptor[cipher].done(skey);
|
||||
}
|
||||
|
||||
if (direction == CCM_ENCRYPT) {
|
||||
/* store the TAG */
|
||||
for (x = 0; x < 16 && x < *taglen; x++) {
|
||||
tag[x] = PAD[x] ^ CTRPAD[x];
|
||||
}
|
||||
*taglen = x;
|
||||
} else { /* direction == CCM_DECRYPT */
|
||||
/* decrypt the tag */
|
||||
for (x = 0; x < 16 && x < *taglen; x++) {
|
||||
ptTag[x] = tag[x] ^ CTRPAD[x];
|
||||
}
|
||||
*taglen = x;
|
||||
|
||||
/* check validity of the decrypted tag against the computed PAD (in constant time) */
|
||||
/* HACK: the boolean value of XMEM_NEQ becomes either 0 (CRYPT_OK) or 1 (CRYPT_ERR).
|
||||
* there should be a better way of setting the correct error code in constant
|
||||
* time.
|
||||
*/
|
||||
err = XMEM_NEQ(ptTag, PAD, *taglen);
|
||||
|
||||
/* Zero the plaintext if the tag was invalid (in constant time) */
|
||||
if (ptlen > 0) {
|
||||
y = 0;
|
||||
mask *= 1 - err; /* mask = ( err ? 0 : 0xff ) */
|
||||
#ifdef LTC_FAST
|
||||
fastMask *= 1 - err;
|
||||
if (ptlen & ~15) {
|
||||
for (; y < (ptlen & ~15); y += 16) {
|
||||
for (z = 0; z < 16; z += sizeof(LTC_FAST_TYPE)) {
|
||||
*((LTC_FAST_TYPE*)(&pt_real[y+z])) = *((LTC_FAST_TYPE*)(&pt[y+z])) & fastMask;
|
||||
}
|
||||
}
|
||||
}
|
||||
#endif
|
||||
for (; y < ptlen; y++) {
|
||||
pt_real[y] = pt[y] & mask;
|
||||
}
|
||||
}
|
||||
}
|
||||
|
||||
#ifdef LTC_CLEAN_STACK
|
||||
fastMask = 0;
|
||||
mask = 0;
|
||||
zeromem(skey, sizeof(*skey));
|
||||
zeromem(PAD, sizeof(PAD));
|
||||
zeromem(CTRPAD, sizeof(CTRPAD));
|
||||
if (pt_work != NULL) {
|
||||
zeromem(pt_work, ptlen);
|
||||
}
|
||||
#endif
|
||||
error:
|
||||
if (pt_work) {
|
||||
XFREE(pt_work);
|
||||
}
|
||||
if (skey != uskey) {
|
||||
XFREE(skey);
|
||||
}
|
||||
|
||||
@ -114,11 +114,13 @@ int ccm_test(void)
|
||||
|
||||
};
|
||||
unsigned long taglen, x, y;
|
||||
unsigned char buf[64], buf2[64], tag2[16], tag[16];
|
||||
unsigned char buf[64], buf2[64], tag[16], tag2[16], tag3[16], zero[64];
|
||||
int err, idx;
|
||||
symmetric_key skey;
|
||||
ccm_state ccm;
|
||||
|
||||
zeromem(zero, 64);
|
||||
|
||||
idx = find_cipher("aes");
|
||||
if (idx == -1) {
|
||||
idx = find_cipher("rijndael");
|
||||
@ -166,8 +168,8 @@ int ccm_test(void)
|
||||
if (XMEMCMP(buf, tests[x].ct, tests[x].ptlen)) {
|
||||
#if defined(LTC_TEST_DBG)
|
||||
printf("\n%d: x=%lu y=%lu\n", __LINE__, x, y);
|
||||
print_hex("ct is ", tag, taglen);
|
||||
print_hex("ct should", tests[x].tag, taglen);
|
||||
print_hex("ct is ", buf, tests[x].ptlen);
|
||||
print_hex("ct should", tests[x].ct, tests[x].ptlen);
|
||||
#endif
|
||||
return CRYPT_FAIL_TESTVECTOR;
|
||||
}
|
||||
@ -188,6 +190,8 @@ int ccm_test(void)
|
||||
}
|
||||
|
||||
if (y == 0) {
|
||||
XMEMCPY(tag3, tests[x].tag, tests[x].taglen);
|
||||
taglen = tests[x].taglen;
|
||||
if ((err = ccm_memory(idx,
|
||||
tests[x].key, 16,
|
||||
NULL,
|
||||
@ -195,7 +199,7 @@ int ccm_test(void)
|
||||
tests[x].header, tests[x].headerlen,
|
||||
buf2, tests[x].ptlen,
|
||||
buf,
|
||||
tag2, &taglen, 1 )) != CRYPT_OK) {
|
||||
tag3, &taglen, 1 )) != CRYPT_OK) {
|
||||
return err;
|
||||
}
|
||||
} else {
|
||||
@ -219,24 +223,56 @@ int ccm_test(void)
|
||||
if (XMEMCMP(buf2, tests[x].pt, tests[x].ptlen)) {
|
||||
#if defined(LTC_TEST_DBG)
|
||||
printf("\n%d: x=%lu y=%lu\n", __LINE__, x, y);
|
||||
print_hex("pt is ", tag, taglen);
|
||||
print_hex("pt should", tests[x].tag, taglen);
|
||||
print_hex("pt is ", buf2, tests[x].ptlen);
|
||||
print_hex("pt should", tests[x].pt, tests[x].ptlen);
|
||||
#endif
|
||||
return CRYPT_FAIL_TESTVECTOR;
|
||||
}
|
||||
if (y == 0) {
|
||||
/* check if decryption with the wrong tag does not reveal the plaintext */
|
||||
XMEMCPY(tag3, tests[x].tag, tests[x].taglen);
|
||||
tag3[0] ^= 0xff; /* set the tag to the wrong value */
|
||||
taglen = tests[x].taglen;
|
||||
if ((err = ccm_memory(idx,
|
||||
tests[x].key, 16,
|
||||
NULL,
|
||||
tests[x].nonce, tests[x].noncelen,
|
||||
tests[x].header, tests[x].headerlen,
|
||||
buf2, tests[x].ptlen,
|
||||
buf,
|
||||
tag3, &taglen, 1 )) != CRYPT_ERROR) {
|
||||
return CRYPT_FAIL_TESTVECTOR;
|
||||
}
|
||||
if (XMEMCMP(buf2, zero, tests[x].ptlen)) {
|
||||
#if defined(LTC_CCM_TEST_DBG)
|
||||
printf("\n%d: x=%lu y=%lu\n", __LINE__, x, y);
|
||||
print_hex("pt is ", buf2, tests[x].ptlen);
|
||||
print_hex("pt should", zero, tests[x].ptlen);
|
||||
#endif
|
||||
return CRYPT_FAIL_TESTVECTOR;
|
||||
}
|
||||
} else {
|
||||
/* FIXME: Only check the tag if ccm_memory was not called: ccm_memory already
|
||||
validates the tag. ccm_process and ccm_done should somehow do the same,
|
||||
although with current setup it is impossible to keep the plaintext hidden
|
||||
if the tag is incorrect.
|
||||
*/
|
||||
if (XMEMCMP(tag2, tests[x].tag, tests[x].taglen)) {
|
||||
#if defined(LTC_TEST_DBG)
|
||||
printf("\n%d: x=%lu y=%lu\n", __LINE__, x, y);
|
||||
print_hex("tag is ", tag, tests[x].taglen);
|
||||
print_hex("tag is ", tag2, tests[x].taglen);
|
||||
print_hex("tag should", tests[x].tag, tests[x].taglen);
|
||||
#endif
|
||||
return CRYPT_FAIL_TESTVECTOR;
|
||||
}
|
||||
}
|
||||
|
||||
if (y == 0) {
|
||||
cipher_descriptor[idx].done(&skey);
|
||||
}
|
||||
}
|
||||
}
|
||||
|
||||
return CRYPT_OK;
|
||||
#endif
|
||||
}
|
||||
|
||||
Loading…
x
Reference in New Issue
Block a user