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Use safer return values in uECC_verify()

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This is a first step in protecting against fault injection attacks: the
attacker can no longer change failure into success by flipping a single bit.
Additional steps are needed to prevent other attacks (instruction skip etc)
and will be the object of future commits.

The return value of uECC_vli_equal() should be protected as well, which will
be done in a future commit as well.
This commit is contained in:
Manuel Pégourié-Gonnard 2019-11-06 10:30:26 +01:00
parent c05f1506f4
commit 10d8e8ed64
5 changed files with 14 additions and 12 deletions
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4
include/tinycrypt/ecc_dsa.h
View file

@ -123,8 +123,8 @@ int uECC_sign_with_k(const uint8_t *private_key, const uint8_t *message_hash,
/**
* @brief Verify an ECDSA signature.
* @return returns TC_SUCCESS (1) if the signature is valid
* returns TC_FAIL (0) if the signature is invalid.
* @return returns UECC_SUCCESS if the signature is valid
* returns UECC_FAILURE if the signature is invalid.
*
* @param p_public_key IN -- The signer's public key.
* @param p_message_hash IN -- The hash of the signed data.

2
library/pk.c
View file

@ -591,7 +591,7 @@ static int uecc_eckey_verify_wrap( void *ctx, mbedtls_md_type_t md_alg,
ret = uECC_verify( keypair->public_key, hash,
(unsigned) hash_len, signature, uecc_curve );
if( ret == 0 )
if( ret != UECC_SUCCESS )
return( MBEDTLS_ERR_PK_HW_ACCEL_FAILED );
return( 0 );

2
tests/suites/test_suite_tinycrypt.data
View file

@ -8,4 +8,4 @@ ECDH primitive rfc 5903 p256
ecdh_primitive_testvec:"C88F01F510D9AC3F70A292DAA2316DE544E9AAB8AFE84049C62A9C57862D1433":"DAD0B65394221CF9B051E1FECA5787D098DFE637FC90B9EF945D0C3772581180":"5271A0461CDB8252D61F1C456FA3E59AB1F45B33ACCF5F58389E0577B8990BB3":"C6EF9C5D78AE012A011164ACB397CE2088685D8F06BF9BE0B283AB46476BEE53":"D12DFB5289C8D4F81208B70270398C342296970A0BCCB74C736FC7554494BF63":"56FBF3CA366CC23E8157854C13C58D6AAC23F046ADA30F8353E74F33039872AB":"D6840F6B42F6EDAFD13116E0E12565202FEF8E9ECE7DCE03812464D04B9442DE"
ECDSA primitive rfc 4754 p256
ecdsa_primitive_testvec:"2442A5CC0ECD015FA3CA31DC8E2BBC70BF42D60CBCA20085E0822CB04235E970":"6FC98BD7E50211A4A27102FA3549DF79EBCB4BF246B80945CDDFE7D509BBFD7D":"BA7816BF8F01CFEA414140DE5DAE2223B00361A396177A9CB410FF61F20015AD":"CB28E0999B9C7715FD0A80D8E47A77079716CBBF917DD72E97566EA1C066957C":"86FA3BB4E26CAD5BF90B7F81899256CE7594BB1EA0C89212748BFF3B3D5B0315":1
ecdsa_primitive_testvec:"2442A5CC0ECD015FA3CA31DC8E2BBC70BF42D60CBCA20085E0822CB04235E970":"6FC98BD7E50211A4A27102FA3549DF79EBCB4BF246B80945CDDFE7D509BBFD7D":"BA7816BF8F01CFEA414140DE5DAE2223B00361A396177A9CB410FF61F20015AD":"CB28E0999B9C7715FD0A80D8E47A77079716CBBF917DD72E97566EA1C066957C":"86FA3BB4E26CAD5BF90B7F81899256CE7594BB1EA0C89212748BFF3B3D5B0315"

9
tests/suites/test_suite_tinycrypt.function
View file

@ -55,7 +55,7 @@ void test_ecdsa()
TEST_ASSERT( uECC_sign( private, hash, sizeof( hash ), sig, curve ) != 0 );
TEST_ASSERT( uECC_verify( public, hash, sizeof( hash ), sig, curve ) != 0 );
TEST_ASSERT( uECC_verify( public, hash, sizeof( hash ), sig, curve ) == UECC_SUCCESS );
}
/* END_CASE */
@ -88,8 +88,7 @@ void ecdh_primitive_testvec( data_t * private1, data_t * xA_str,
/* BEGIN_CASE depends_on:MBEDTLS_USE_TINYCRYPT */
void ecdsa_primitive_testvec( data_t * xQ_str, data_t * yQ_str,
data_t * hash, data_t * r_str, data_t * s_str,
int result )
data_t * hash, data_t * r_str, data_t * s_str )
{
const struct uECC_Curve_t * curve = uECC_secp256r1();
uint8_t pub_bytes[2*NUM_ECC_BYTES] = {0};
@ -101,7 +100,7 @@ void ecdsa_primitive_testvec( data_t * xQ_str, data_t * yQ_str,
memcpy( sig_bytes + NUM_ECC_BYTES, s_str->x, r_str->len );
TEST_ASSERT( uECC_verify( pub_bytes, hash->x, hash->len,
sig_bytes, curve ) == result );
sig_bytes, curve ) == UECC_SUCCESS );
// Alter the signature and check the verification fails
for( int i = 0; i < 2*NUM_ECC_BYTES; i++ )
@ -109,7 +108,7 @@ void ecdsa_primitive_testvec( data_t * xQ_str, data_t * yQ_str,
uint8_t temp = sig_bytes[i];
sig_bytes[i] = ( sig_bytes[i] + 1 ) % 256;
TEST_ASSERT( uECC_verify( pub_bytes, hash->x, hash->len,
sig_bytes, curve ) == 0 );
sig_bytes, curve ) == UECC_FAILURE );
sig_bytes[i] = temp;
}

9
tinycrypt/ecc_dsa.c
View file

@ -235,13 +235,13 @@ int uECC_verify(const uint8_t *public_key, const uint8_t *message_hash,
/* r, s must not be 0. */
if (uECC_vli_isZero(r) || uECC_vli_isZero(s)) {
return 0;
return UECC_FAILURE;
}
/* r, s must be < n. */
if (uECC_vli_cmp_unsafe(curve->n, r) != 1 ||
uECC_vli_cmp_unsafe(curve->n, s) != 1) {
return 0;
return UECC_FAILURE;
}
/* Calculate u1 and u2. */
@ -301,7 +301,10 @@ int uECC_verify(const uint8_t *public_key, const uint8_t *message_hash,
}
/* Accept only if v == r. */
return (int)(uECC_vli_equal(rx, r) == 0);
if (uECC_vli_equal(rx, r) == 0)
return UECC_SUCCESS;
return UECC_FAILURE;
}
#else
typedef int mbedtls_dummy_tinycrypt_def;