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ed25519: check that the signature is smaller than the order #7513

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May 13, 2024
Merged

ed25519: check that the signature is smaller than the order #7513

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2508c9e
ed25519: check that the signature is smaller than the order
julek-wolfssl May 8, 2024
ab03324
ed25519: put entire order into buffer for sanity check
julek-wolfssl May 8, 2024
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52 changes: 19 additions & 33 deletions wolfcrypt/src/ed25519.c
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Original file line number Diff line number Diff line change
Expand Up @@ -698,15 +698,14 @@ static int ed25519_verify_msg_update_with_sha(const byte* msgSegment,
return ed25519_hash_update(key, sha, msgSegment, msgSegmentLen);
}

/* Low part of order in big endian. */
static const byte ed25519_low_order[] = {
0x14, 0xde, 0xf9, 0xde, 0xa2, 0xf7, 0x9c, 0xd6,
0x58, 0x12, 0x63, 0x1a, 0x5c, 0xf5, 0xd3, 0xed
/* ed25519 order in little endian. */
static const byte ed25519_order[] = {
0xed, 0xd3, 0xf5, 0x5c, 0x1a, 0x63, 0x12, 0x58,
0xd6, 0x9c, 0xf7, 0xa2, 0xde, 0xf9, 0xde, 0x14,
0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x10
};

#define ED25519_SIG_LOW_ORDER_IDX \
((int)(ED25519_SIG_SIZE/2 + sizeof(ed25519_low_order) - 1))

/*
sig is array of bytes containing the signature
sigLen is the length of sig byte array
Expand All @@ -725,6 +724,7 @@ static int ed25519_verify_msg_final_with_sha(const byte* sig, word32 sigLen,
ge_p2 R;
#endif
int ret;
int i;

/* sanity check on arguments */
if (sig == NULL || res == NULL || key == NULL)
Expand All @@ -740,33 +740,19 @@ static int ed25519_verify_msg_final_with_sha(const byte* sig, word32 sigLen,
* 2^252 + 0x14def9dea2f79cd65812631a5cf5d3ed
* = 0x1000000000000000000000000000000014def9dea2f79cd65812631a5cf5d3ed
*/
if (sig[ED25519_SIG_SIZE-1] > 0x10)
return BAD_FUNC_ARG;
if (sig[ED25519_SIG_SIZE-1] == 0x10) {
int i = ED25519_SIG_SIZE-1;
int j;

/* Check high zeros. */
for (--i; i > ED25519_SIG_LOW_ORDER_IDX; i--) {
if (sig[i] > 0x00)
break;
}
/* Did we see all zeros up to lower order index? */
if (i == ED25519_SIG_LOW_ORDER_IDX) {
/* Check lower part. */
for (j = 0; j < (int)sizeof(ed25519_low_order); j++, i--) {
/* Check smaller. */
if (sig[i] < ed25519_low_order[j])
break;
/* Check bigger. */
if (sig[i] > ed25519_low_order[j])
return BAD_FUNC_ARG;
}
/* Check equal - all bytes match. */
if (i == ED25519_SIG_SIZE/2 - 1)
return BAD_FUNC_ARG;
}

/* Check S is not larger than or equal to order. */
for (i = (int)sizeof(ed25519_order) - 1; i >= 0; i--) {
/* Bigger than order. */
if (sig[ED25519_SIG_SIZE/2 + i] > ed25519_order[i])
return BAD_FUNC_ARG;
/* Less than order. */
if (sig[ED25519_SIG_SIZE/2 + i] < ed25519_order[i])
break;
}
/* Check equal - all bytes match. */
if (i == -1)
return BAD_FUNC_ARG;

/* uncompress A (public key), test if valid, and negate it */
#ifndef FREESCALE_LTC_ECC
Expand Down
73 changes: 73 additions & 0 deletions wolfcrypt/test/test.c
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Original file line number Diff line number Diff line change
Expand Up @@ -33910,6 +33910,79 @@ WOLFSSL_TEST_SUBROUTINE wc_test_ret_t ed25519_test(void)
#endif /* HAVE_ED25519_VERIFY */
}

{
/* Run tests for some rare code paths */
/* sig is exactly equal to the order */
const byte rareEd1[] = {
0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
0xed, 0xd3, 0xf5, 0x5c, 0x1a, 0x63, 0x12, 0x58,
0xd6, 0x9c, 0xf7, 0xa2, 0xde, 0xf9, 0xde, 0x14,
0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x10
};
/* sig is larger than the order before we get to the low part */
const byte rareEd2[] = {
0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
0xed, 0xd3, 0xf5, 0x5c, 0x1a, 0x63, 0x12, 0x58,
0xd6, 0x9c, 0xf7, 0xa2, 0xde, 0xf9, 0xde, 0x14,
0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
0x00, 0x00, 0x00, 0x00, 0x00, 0x01, 0x00, 0x10
};
/* sig is larger than the order in the low part */
const byte rareEd3[] = {
0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
0xed, 0xd3, 0xf5, 0x5c, 0x1a, 0x63, 0x12, 0x58,
0xd6, 0x9c, 0xf9, 0xa2, 0xde, 0xf9, 0xde, 0x14,
0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x10
};
/* sig is smaller than the order */
const byte rareEd4[] = {
0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
0xed, 0xd3, 0xf5, 0x5c, 0x1a, 0x63, 0x12, 0x58,
0xd6, 0x9c, 0xf1, 0xa2, 0xde, 0xf9, 0xde, 0x14,
0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x10
};

ret = wc_ed25519_import_private_key(sKeys[0], ED25519_KEY_SIZE,
pKeys[0], pKeySz[0], &key);
if (ret != 0)
return ret;

ret = wc_ed25519_verify_msg(rareEd1, sizeof(rareEd1), msgs[0], msgSz[0],
&verify, &key);
if (ret != BAD_FUNC_ARG)
return ret;

ret = wc_ed25519_verify_msg(rareEd2, sizeof(rareEd2), msgs[0], msgSz[0],
&verify, &key);
if (ret != BAD_FUNC_ARG)
return ret;

ret = wc_ed25519_verify_msg(rareEd3, sizeof(rareEd3), msgs[0], msgSz[0],
&verify, &key);
if (ret != BAD_FUNC_ARG)
return ret;

ret = wc_ed25519_verify_msg(rareEd4, sizeof(rareEd4), msgs[0], msgSz[0],
&verify, &key);
if (ret != SIG_VERIFY_E)
return ret;
}

ret = ed25519ctx_test();
if (ret != 0)
return ret;
Expand Down