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Return and propagate UECC_FAULT_DETECTED

Browse source 
This commit first changes the return convention of EccPoint_mult_safer() so
that it properly reports when faults are detected. Then all functions that
call it need to be changed to (1) follow the same return convention and (2)
properly propagate UECC_FAULT_DETECTED when it occurs.

Here's the reverse call graph from EccPoint_mult_safer() to the rest of the
library (where return values are translated to the MBEDTLS_ERR_ space) and test
functions (where expected return values are asserted explicitly).

EccPoint_mult_safer()
    EccPoint_compute_public_key()
        uECC_compute_public_key()
            pkparse.c
            tests/suites/test_suite_pkparse.function
        uECC_make_key_with_d()
        uECC_make_key()
            ssl_cli.c
            ssl_srv.c
            tests/suites/test_suite_pk.function
            tests/suites/test_suite_tinycrypt.function
    uECC_shared_secret()
        ssl_tls.c
        tests/suites/test_suite_tinycrypt.function
    uECC_sign_with_k()
        uECC_sign()
            pk.c
            tests/suites/test_suite_tinycrypt.function

Note: in uECC_sign_with_k() a test for uECC_vli_isZero(p) is suppressed
because it is redundant with a more thorough test (point validity) done at the
end of EccPoint_mult_safer(). This redundancy was introduced in a previous
commit but not noticed earlier.
This commit is contained in:
Manuel Pégourié-Gonnard 2019-11-25 13:06:05 +01:00
parent 4d6186beb0
commit 9d6a535ba1
14 changed files with 112 additions and 96 deletions

4
include/tinycrypt/ecc.h
View file

@ -217,7 +217,7 @@ int uECC_curve_public_key_size(void);
* @param private_key IN -- The private key to compute the public key for
* @param public_key OUT -- Will be filled in with the corresponding public key
* @param curve
* @return Returns 1 if key was computed successfully, 0 if an error occurred.
* @return UECC_SUCCESS or UECC_FAILURE or UECC_FAULT_DETECTED
*/
int uECC_compute_public_key(const uint8_t *private_key,
uint8_t *public_key);
@ -228,6 +228,7 @@ int uECC_compute_public_key(const uint8_t *private_key,
* @param result OUT -- public-key
* @param private_key IN -- private-key
* @param curve IN -- elliptic curve
* @return UECC_SUCCESS or UECC_FAILURE or UECC_FAULT_DETECTED
*/
uECC_word_t EccPoint_compute_public_key(uECC_word_t *result,
uECC_word_t *private_key);
@ -241,6 +242,7 @@ uECC_word_t EccPoint_compute_public_key(uECC_word_t *result,
* @param result OUT -- returns scalar*point
* @param point IN -- elliptic curve point
* @param scalar IN -- scalar
* @return UECC_SUCCESS or UECC_FAILURE or UECC_FAULT_DETECTED
*/
int EccPoint_mult_safer(uECC_word_t * result, const uECC_word_t * point,
const uECC_word_t * scalar);

6
include/tinycrypt/ecc_dh.h
View file

@ -83,8 +83,7 @@ extern "C" {
/**
* @brief Create a public/private key pair.
* @return returns TC_CRYPTO_SUCCESS (1) if the key pair was generated successfully
* returns TC_CRYPTO_FAIL (0) if error while generating key pair
* @return UECC_SUCCESS or UECC_FAILURE or UECC_FAULT_DETECTED
*
* @param p_public_key OUT -- Will be filled in with the public key. Must be at
* least 2 * the curve size (in bytes) long. For curve secp256r1, p_public_key
@ -114,8 +113,7 @@ int uECC_make_key_with_d(uint8_t *p_public_key, uint8_t *p_private_key,
/**
* @brief Compute a shared secret given your secret key and someone else's
* public key.
* @return returns TC_CRYPTO_SUCCESS (1) if the shared secret was computed successfully
* returns TC_CRYPTO_FAIL (0) otherwise
* @return UECC_SUCCESS or UECC_FAILURE or UECC_FAULT_DETECTED
*
* @param p_secret OUT -- Will be filled in with the shared secret value. Must be
* the same size as the curve size (for curve secp256r1, secret must be 32 bytes

3
include/tinycrypt/ecc_dsa.h
View file

@ -92,8 +92,7 @@ extern "C" {
/**
* @brief Generate an ECDSA signature for a given hash value.
* @return returns TC_CRYPTO_SUCCESS (1) if the signature generated successfully
* returns TC_CRYPTO_FAIL (0) if an error occurred.
* @return UECC_SUCCESS or UECC_FAILURE or UECC_FAULT_DETECTED
*
* @param p_private_key IN -- Your private key.
* @param p_message_hash IN -- The hash of the message to sign.

5
library/pk.c
View file

@ -723,8 +723,9 @@ static int uecc_eckey_sign_wrap( void *ctx, mbedtls_md_type_t md_alg,
#define MAX_SECP256R1_ECDSA_SIG_LEN ( 3 + 2 * ( 3 + NUM_ECC_BYTES ) )
ret = uECC_sign( keypair->private_key, hash, hash_len, sig );
/* TinyCrypt uses 0 to signal errors. */
if( ret == 0 )
if( ret == UECC_FAULT_DETECTED )
return( MBEDTLS_ERR_PLATFORM_FAULT_DETECTED );
if( ret != UECC_SUCCESS )
return( MBEDTLS_ERR_PK_HW_ACCEL_FAILED );
*sig_len = 2 * NUM_ECC_BYTES;

4
library/pkparse.c
View file

@ -987,7 +987,9 @@ static int pk_parse_key_sec1_der( mbedtls_uecc_keypair *keypair,
{
ret = uECC_compute_public_key( keypair->private_key,
keypair->public_key );
if( ret == 0 )
if( ret == UECC_FAULT_DETECTED )
return( MBEDTLS_ERR_PLATFORM_FAULT_DETECTED );
if( ret != UECC_SUCCESS )
return( MBEDTLS_ERR_PK_KEY_INVALID_FORMAT );
}

16
library/ssl_cli.c
View file

@ -3568,7 +3568,6 @@ static int ssl_out_client_key_exchange_write( mbedtls_ssl_context *ssl,
{
((void) n);
((void) ret);
if( (size_t)( end - p ) < 2 * NUM_ECC_BYTES + 2 )
return( MBEDTLS_ERR_SSL_BUFFER_TOO_SMALL );
@ -3576,10 +3575,11 @@ static int ssl_out_client_key_exchange_write( mbedtls_ssl_context *ssl,
*p++ = 2 * NUM_ECC_BYTES + 1;
*p++ = 0x04; /* uncompressed point presentation */
if( !uECC_make_key( p, ssl->handshake->ecdh_privkey ) )
{
ret = uECC_make_key( p, ssl->handshake->ecdh_privkey );
if( ret == UECC_FAULT_DETECTED )
return( MBEDTLS_ERR_PLATFORM_FAULT_DETECTED );
if( ret != UECC_SUCCESS )
return( MBEDTLS_ERR_SSL_HW_ACCEL_FAILED );
}
p += 2 * NUM_ECC_BYTES;
}
else
@ -3717,7 +3717,6 @@ static int ssl_out_client_key_exchange_write( mbedtls_ssl_context *ssl,
{
#if defined(MBEDTLS_USE_TINYCRYPT)
((void) n);
((void) ret);
if( (size_t)( end - p ) < 2 * NUM_ECC_BYTES + 2 )
return( MBEDTLS_ERR_SSL_BUFFER_TOO_SMALL );
@ -3725,10 +3724,11 @@ static int ssl_out_client_key_exchange_write( mbedtls_ssl_context *ssl,
*p++ = 2 * NUM_ECC_BYTES + 1;
*p++ = 0x04; /* uncompressed point presentation */
if( !uECC_make_key( p, ssl->handshake->ecdh_privkey ) )
{
ret = uECC_make_key( p, ssl->handshake->ecdh_privkey );
if( ret == UECC_FAULT_DETECTED )
return( MBEDTLS_ERR_PLATFORM_FAULT_DETECTED );
if( ret != UECC_SUCCESS )
return( MBEDTLS_ERR_SSL_HW_ACCEL_FAILED );
}
p += 2 * NUM_ECC_BYTES;
#else /* MBEDTLS_USE_TINYCRYPT */
/*

13
library/ssl_srv.c
View file

@ -3410,6 +3410,7 @@ static int ssl_prepare_server_key_exchange( mbedtls_ssl_context *ssl,
#if defined(MBEDTLS_USE_TINYCRYPT)
{
int ret;
static const unsigned char ecdh_param_hdr[] = {
MBEDTLS_SSL_EC_TLS_NAMED_CURVE,
0 /* high bits of secp256r1 TLS ID */,
@ -3426,12 +3427,12 @@ static int ssl_prepare_server_key_exchange( mbedtls_ssl_context *ssl,
ecdh_param_hdr, sizeof( ecdh_param_hdr ) );
ssl->out_msglen += sizeof( ecdh_param_hdr );
if( !uECC_make_key( &ssl->out_msg[ ssl->out_msglen ],
ssl->handshake->ecdh_privkey ) )
{
MBEDTLS_SSL_DEBUG_MSG( 1, ( "Key creation failed" ) );
return( MBEDTLS_ERR_SSL_INTERNAL_ERROR );
}
ret = uECC_make_key( &ssl->out_msg[ ssl->out_msglen ],
ssl->handshake->ecdh_privkey );
if( ret == UECC_FAULT_DETECTED )
return( MBEDTLS_ERR_PLATFORM_FAULT_DETECTED );
if( ret != UECC_SUCCESS )
return( MBEDTLS_ERR_SSL_HW_ACCEL_FAILED );
ssl->out_msglen += 2*NUM_ECC_BYTES;
}

26
library/ssl_tls.c
View file

@ -1973,14 +1973,13 @@ int mbedtls_ssl_build_pms( mbedtls_ssl_context *ssl )
mbedtls_ssl_suite_get_key_exchange( ciphersuite_info )
== MBEDTLS_KEY_EXCHANGE_ECDH_ECDSA )
{
((void) ret);
if( !uECC_shared_secret( ssl->handshake->ecdh_peerkey,
ssl->handshake->ecdh_privkey,
ssl->handshake->premaster ) )
{
ret = uECC_shared_secret( ssl->handshake->ecdh_peerkey,
ssl->handshake->ecdh_privkey,
ssl->handshake->premaster );
if( ret == UECC_FAULT_DETECTED )
return( MBEDTLS_ERR_PLATFORM_FAULT_DETECTED );
if( ret != UECC_SUCCESS )
return( MBEDTLS_ERR_SSL_HW_ACCEL_FAILED );
}
ssl->handshake->pmslen = NUM_ECC_BYTES;
}
@ -2168,14 +2167,13 @@ int mbedtls_ssl_psk_derive_premaster( mbedtls_ssl_context *ssl, mbedtls_key_exch
size_t zlen;
#if defined(MBEDTLS_USE_TINYCRYPT)
((void) ret);
if( !uECC_shared_secret( ssl->handshake->ecdh_peerkey,
ssl->handshake->ecdh_privkey,
p + 2 ) )
{
ret = uECC_shared_secret( ssl->handshake->ecdh_peerkey,
ssl->handshake->ecdh_privkey,
p + 2 );
if( ret == UECC_FAULT_DETECTED )
return( MBEDTLS_ERR_PLATFORM_FAULT_DETECTED );
if( ret != UECC_SUCCESS )
return( MBEDTLS_ERR_SSL_HW_ACCEL_FAILED );
}
zlen = NUM_ECC_BYTES;
#else /* MBEDTLS_USE_TINYCRYPT */

2
tests/suites/test_suite_pk.function
View file

@ -36,7 +36,7 @@ static int pk_genkey( mbedtls_pk_context *pk )
ret = uECC_make_key( mbedtls_pk_uecc( *pk )->public_key,
mbedtls_pk_uecc( *pk )->private_key );
if( ret == 0 )
if( ret != UECC_SUCCESS )
return( -1 );
return( 0 );

2
tests/suites/test_suite_pkparse.function
View file

@ -137,7 +137,7 @@ void pk_parse_keyfile_ec( char * key_file, char * password, int result )
uecckey = mbedtls_pk_uecc( ctx );
TEST_ASSERT( uECC_valid_public_key( uecckey->public_key ) == 0 );
TEST_ASSERT( uECC_compute_public_key( uecckey->private_key,
tmp_pubkey ) != 0 );
tmp_pubkey ) == UECC_SUCCESS );
TEST_ASSERT( memcmp( tmp_pubkey, uecckey->public_key,
sizeof( tmp_pubkey ) ) == 0 );
#endif /* MBEDTLS_USE_TINYCRYPT */

16
tests/suites/test_suite_tinycrypt.function
View file

@ -23,13 +23,13 @@ void test_ecdh()
uECC_set_rng( &uecc_rng_wrapper );
TEST_ASSERT( uECC_make_key( public1, private1 ) != 0 );
TEST_ASSERT( uECC_make_key( public1, private1 ) == UECC_SUCCESS );
TEST_ASSERT( uECC_make_key( public2, private2 ) != 0 );
TEST_ASSERT( uECC_make_key( public2, private2 ) == UECC_SUCCESS );
TEST_ASSERT( uECC_shared_secret( public2, private1, secret1 ) != 0 );
TEST_ASSERT( uECC_shared_secret( public2, private1, secret1 ) == UECC_SUCCESS );
TEST_ASSERT( uECC_shared_secret( public1, private2, secret2 ) != 0 );
TEST_ASSERT( uECC_shared_secret( public1, private2, secret2 ) == UECC_SUCCESS );
TEST_ASSERT( memcmp( secret1, secret2, sizeof( secret1 ) ) == 0 );
}
@ -47,9 +47,9 @@ void test_ecdsa()
TEST_ASSERT( rnd_std_rand( NULL, hash, NUM_ECC_BYTES ) == 0 );
TEST_ASSERT( uECC_make_key( public, private ) != 0 );
TEST_ASSERT( uECC_make_key( public, private ) == UECC_SUCCESS );
TEST_ASSERT( uECC_sign( private, hash, sizeof( hash ), sig ) != 0 );
TEST_ASSERT( uECC_sign( private, hash, sizeof( hash ), sig ) == UECC_SUCCESS );
TEST_ASSERT( uECC_verify( public, hash, sizeof( hash ), sig ) == UECC_SUCCESS );
}
@ -71,9 +71,9 @@ void ecdh_primitive_testvec( data_t * private1, data_t * xA_str,
memcpy( public2 + NUM_ECC_BYTES, yB_str->x, yB_str->len );
// Compute shared secrets and compare to test vector secret
TEST_ASSERT( uECC_shared_secret( public2, private1->x, secret1 ) != 0 );
TEST_ASSERT( uECC_shared_secret( public2, private1->x, secret1 ) == UECC_SUCCESS );
TEST_ASSERT( uECC_shared_secret( public1, private2->x, secret2 ) != 0 );
TEST_ASSERT( uECC_shared_secret( public1, private2->x, secret2 ) == UECC_SUCCESS );
TEST_ASSERT( memcmp( secret1, secret2, sizeof( secret1 ) ) == 0 );
TEST_ASSERT( memcmp( secret1, z_str->x, sizeof( secret1 ) ) == 0 );

29
tinycrypt/ecc.c
View file

@ -1021,16 +1021,16 @@ int EccPoint_mult_safer(uECC_word_t * result, const uECC_word_t * point,
wordcount_t num_words = NUM_ECC_WORDS;
uECC_word_t carry;
uECC_word_t *initial_Z = 0;
int r;
int r = UECC_FAULT_DETECTED;
/* Protect against faults modifying curve paremeters in flash */
if (uECC_check_curve_integrity() != 0) {
return 0;
return UECC_FAULT_DETECTED;
}
/* Protects against invalid curves attacks */
/* Protects against invalid curve attacks */
if (uECC_valid_point(point) != 0 ) {
return 0;
return UECC_FAILURE;
}
/* Regularize the bitcount for the private key so that attackers cannot use a
@ -1041,7 +1041,7 @@ int EccPoint_mult_safer(uECC_word_t * result, const uECC_word_t * point,
* protect against side-channel attacks such as Template SPA */
if (g_rng_function) {
if (!uECC_generate_random_int(k2[carry], curve_p, num_words)) {
r = 0;
r = UECC_FAILURE;
goto clear_and_out;
}
initial_Z = k2[carry];
@ -1052,17 +1052,17 @@ int EccPoint_mult_safer(uECC_word_t * result, const uECC_word_t * point,
/* Protect against fault injections that would make the resulting
* point not lie on the intended curve */
if (uECC_valid_point(result) != 0 ) {
r = 0;
r = UECC_FAULT_DETECTED;
goto clear_and_out;
}
/* Protect against faults modifying curve paremeters in flash */
if (uECC_check_curve_integrity() != 0) {
r = 0;
r = UECC_FAULT_DETECTED;
goto clear_and_out;
}
r = 1;
r = UECC_SUCCESS;
clear_and_out:
/* erasing temporary buffer used to store secret: */
@ -1176,7 +1176,7 @@ int uECC_valid_public_key(const uint8_t *public_key)
int uECC_compute_public_key(const uint8_t *private_key, uint8_t *public_key)
{
int ret;
uECC_word_t _private[NUM_ECC_WORDS];
uECC_word_t _public[NUM_ECC_WORDS * 2];
@ -1187,23 +1187,24 @@ int uECC_compute_public_key(const uint8_t *private_key, uint8_t *public_key)
/* Make sure the private key is in the range [1, n-1]. */
if (uECC_vli_isZero(_private)) {
return 0;
return UECC_FAILURE;
}
if (uECC_vli_cmp(curve_n, _private) != 1) {
return 0;
return UECC_FAILURE;
}
/* Compute public key. */
if (!EccPoint_compute_public_key(_public, _private)) {
return 0;
ret = EccPoint_compute_public_key(_public, _private);
if (ret != UECC_SUCCESS) {
return ret;
}
uECC_vli_nativeToBytes(public_key, NUM_ECC_BYTES, _public);
uECC_vli_nativeToBytes(
public_key +
NUM_ECC_BYTES, NUM_ECC_BYTES, _public + NUM_ECC_WORDS);
return 1;
return UECC_SUCCESS;
}
#else
typedef int mbedtls_dummy_tinycrypt_def;

55
tinycrypt/ecc_dh.c
View file

@ -75,7 +75,7 @@
int uECC_make_key_with_d(uint8_t *public_key, uint8_t *private_key,
unsigned int *d)
{
int ret;
uECC_word_t _private[NUM_ECC_WORDS];
uECC_word_t _public[NUM_ECC_WORDS * 2];
@ -85,30 +85,32 @@ int uECC_make_key_with_d(uint8_t *public_key, uint8_t *private_key,
mbedtls_platform_memcpy (_private, d, NUM_ECC_BYTES);
/* Computing public-key from private: */
if (EccPoint_compute_public_key(_public, _private)) {
/* Converting buffers to correct bit order: */
uECC_vli_nativeToBytes(private_key,
BITS_TO_BYTES(NUM_ECC_BITS),
_private);
uECC_vli_nativeToBytes(public_key,
NUM_ECC_BYTES,
_public);
uECC_vli_nativeToBytes(public_key + NUM_ECC_BYTES,
NUM_ECC_BYTES,
_public + NUM_ECC_WORDS);
/* erasing temporary buffer used to store secret: */
mbedtls_platform_memset(_private, 0, NUM_ECC_BYTES);
return 1;
ret = EccPoint_compute_public_key(_public, _private);
if (ret != UECC_SUCCESS) {
goto exit;
}
return 0;
/* Converting buffers to correct bit order: */
uECC_vli_nativeToBytes(private_key,
BITS_TO_BYTES(NUM_ECC_BITS),
_private);
uECC_vli_nativeToBytes(public_key,
NUM_ECC_BYTES,
_public);
uECC_vli_nativeToBytes(public_key + NUM_ECC_BYTES,
NUM_ECC_BYTES,
_public + NUM_ECC_WORDS);
exit:
/* erasing temporary buffer used to store secret: */
mbedtls_platform_memset(_private, 0, NUM_ECC_BYTES);
return ret;
}
int uECC_make_key(uint8_t *public_key, uint8_t *private_key)
{
int ret;
uECC_word_t _random[NUM_ECC_WORDS * 2];
uECC_word_t _private[NUM_ECC_WORDS];
uECC_word_t _public[NUM_ECC_WORDS * 2];
@ -119,14 +121,19 @@ int uECC_make_key(uint8_t *public_key, uint8_t *private_key)
uECC_RNG_Function rng_function = uECC_get_rng();
if (!rng_function ||
!rng_function((uint8_t *)_random, 2 * NUM_ECC_WORDS*uECC_WORD_SIZE)) {
return 0;
return UECC_FAILURE;
}
/* computing modular reduction of _random (see FIPS 186.4 B.4.1): */
uECC_vli_mmod(_private, _random, curve_n);
/* Computing public-key from private: */
if (EccPoint_compute_public_key(_public, _private)) {
ret = EccPoint_compute_public_key(_public, _private);
/* don't try again if a fault was detected */
if (ret == UECC_FAULT_DETECTED) {
return ret;
}
if (ret == UECC_SUCCESS) {
/* Converting buffers to correct bit order: */
uECC_vli_nativeToBytes(private_key,
@ -142,10 +149,10 @@ int uECC_make_key(uint8_t *public_key, uint8_t *private_key)
/* erasing temporary buffer that stored secret: */
mbedtls_platform_memset(_private, 0, NUM_ECC_BYTES);
return 1;
return UECC_SUCCESS;
}
}
return 0;
return UECC_FAILURE;
}
int uECC_shared_secret(const uint8_t *public_key, const uint8_t *private_key,

27
tinycrypt/ecc_dsa.c
View file

@ -122,12 +122,12 @@ int uECC_sign_with_k(const uint8_t *private_key, const uint8_t *message_hash,
/* Make sure 0 < k < curve_n */
if (uECC_vli_isZero(k) ||
uECC_vli_cmp(curve_n, k) != 1) {
return 0;
return UECC_FAILURE;
}
r = EccPoint_mult_safer(p, curve_G, k);
if (r == 0 || uECC_vli_isZero(p)) {
return 0;
if (r != UECC_SUCCESS) {
return r;
}
/* If an RNG function was specified, get a random number
@ -137,7 +137,7 @@ int uECC_sign_with_k(const uint8_t *private_key, const uint8_t *message_hash,
tmp[0] = 1;
}
else if (!uECC_generate_random_int(tmp, curve_n, num_n_words)) {
return 0;
return UECC_FAILURE;
}
/* Prevent side channel analysis of uECC_vli_modInv() to determine
@ -159,16 +159,17 @@ int uECC_sign_with_k(const uint8_t *private_key, const uint8_t *message_hash,
uECC_vli_modAdd(s, tmp, s, curve_n); /* s = e + r*d */
uECC_vli_modMult(s, s, k, curve_n); /* s = (e + r*d) / k */
if (uECC_vli_numBits(s) > (bitcount_t)NUM_ECC_BYTES * 8) {
return 0;
return UECC_FAILURE;
}
uECC_vli_nativeToBytes(signature + NUM_ECC_BYTES, NUM_ECC_BYTES, s);
return 1;
return UECC_SUCCESS;
}
int uECC_sign(const uint8_t *private_key, const uint8_t *message_hash,
unsigned hash_size, uint8_t *signature)
{
int r;
uECC_word_t _random[2*NUM_ECC_WORDS];
uECC_word_t k[NUM_ECC_WORDS];
uECC_word_t tries;
@ -178,17 +179,23 @@ int uECC_sign(const uint8_t *private_key, const uint8_t *message_hash,
uECC_RNG_Function rng_function = uECC_get_rng();
if (!rng_function ||
!rng_function((uint8_t *)_random, 2*NUM_ECC_WORDS*uECC_WORD_SIZE)) {
return 0;
return UECC_FAILURE;
}
// computing k as modular reduction of _random (see FIPS 186.4 B.5.1):
uECC_vli_mmod(k, _random, curve_n);
if (uECC_sign_with_k(private_key, message_hash, hash_size, k, signature)) {
return 1;
r = uECC_sign_with_k(private_key, message_hash, hash_size, k, signature);
/* don't keep trying if a fault was detected */
if (r == UECC_FAULT_DETECTED) {
return r;
}
if (r == UECC_SUCCESS) {
return UECC_SUCCESS;
}
/* else keep trying */
}
return 0;
return UECC_FAILURE;
}
static bitcount_t smax(bitcount_t a, bitcount_t b)