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Merge pull request #9739 from gilles-peskine-arm/mbedtls_psa_ecp_generate_key-no_public_key-3.6

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Backport 3.6: PSA ECC key generation: don't generate the public key
This commit is contained in:
Gilles Peskine 2024-11-04 16:36:49 +00:00 committed by GitHub
commit aef3f74e4d
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GPG Key ID: B5690EEEBB952194
5 changed files with 277 additions and 19 deletions
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3
ChangeLog.d/mbedtls_psa_ecp_generate_key-no_public_key.txt Normal file
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@ -0,0 +1,3 @@
Changes
* Improve performance of PSA key generation with ECC keys: it no longer
computes the public key (which was immediately discarded). Fixes #9732.

36
library/psa_crypto_ecp.c
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@ -321,38 +321,36 @@ psa_status_t mbedtls_psa_ecp_generate_key(
const psa_key_attributes_t *attributes,
uint8_t *key_buffer, size_t key_buffer_size, size_t *key_buffer_length)
{
psa_status_t status = PSA_ERROR_CORRUPTION_DETECTED;
int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;
psa_ecc_family_t curve = PSA_KEY_TYPE_ECC_GET_FAMILY(
attributes->type);
mbedtls_ecp_group_id grp_id =
mbedtls_ecc_group_from_psa(curve, attributes->bits);
const mbedtls_ecp_curve_info *curve_info =
mbedtls_ecp_curve_info_from_grp_id(grp_id);
mbedtls_ecp_keypair ecp;
if (grp_id == MBEDTLS_ECP_DP_NONE || curve_info == NULL) {
if (grp_id == MBEDTLS_ECP_DP_NONE) {
return PSA_ERROR_NOT_SUPPORTED;
}
mbedtls_ecp_keypair ecp;
mbedtls_ecp_keypair_init(&ecp);
ret = mbedtls_ecp_gen_key(grp_id, &ecp,
mbedtls_psa_get_random,
MBEDTLS_PSA_RANDOM_STATE);
int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;
ret = mbedtls_ecp_group_load(&ecp.grp, grp_id);
if (ret != 0) {
mbedtls_ecp_keypair_free(&ecp);
return mbedtls_to_psa_error(ret);
goto exit;
}
status = mbedtls_to_psa_error(
mbedtls_ecp_write_key_ext(&ecp, key_buffer_length,
key_buffer, key_buffer_size));
ret = mbedtls_ecp_gen_privkey(&ecp.grp, &ecp.d,
mbedtls_psa_get_random,
MBEDTLS_PSA_RANDOM_STATE);
if (ret != 0) {
goto exit;
}
ret = mbedtls_ecp_write_key_ext(&ecp, key_buffer_length,
key_buffer, key_buffer_size);
exit:
mbedtls_ecp_keypair_free(&ecp);
return status;
return mbedtls_to_psa_error(ret);
}
#endif /* MBEDTLS_PSA_BUILTIN_KEY_TYPE_ECC_KEY_PAIR_GENERATE */

10
tests/scripts/analyze_outcomes.py
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@ -428,6 +428,8 @@ class DriverVSReference_ecp_light_only(outcome_analysis.DriverVSReference):
IGNORED_SUITES = [
# Modules replaced by drivers
'ecdsa', 'ecdh', 'ecjpake',
# Unit tests for the built-in implementation
'psa_crypto_ecp',
]
IGNORED_TESTS = {
'test_suite_config': [
@ -468,6 +470,8 @@ class DriverVSReference_no_ecp_at_all(outcome_analysis.DriverVSReference):
IGNORED_SUITES = [
# Modules replaced by drivers
'ecp', 'ecdsa', 'ecdh', 'ecjpake',
# Unit tests for the built-in implementation
'psa_crypto_ecp',
]
IGNORED_TESTS = {
'test_suite_config': [
@ -508,6 +512,8 @@ class DriverVSReference_ecc_no_bignum(outcome_analysis.DriverVSReference):
'ecp', 'ecdsa', 'ecdh', 'ecjpake',
'bignum_core', 'bignum_random', 'bignum_mod', 'bignum_mod_raw',
'bignum.generated', 'bignum.misc',
# Unit tests for the built-in implementation
'psa_crypto_ecp',
]
IGNORED_TESTS = {
'test_suite_config': [
@ -553,6 +559,8 @@ class DriverVSReference_ecc_ffdh_no_bignum(outcome_analysis.DriverVSReference):
'ecp', 'ecdsa', 'ecdh', 'ecjpake', 'dhm',
'bignum_core', 'bignum_random', 'bignum_mod', 'bignum_mod_raw',
'bignum.generated', 'bignum.misc',
# Unit tests for the built-in implementation
'psa_crypto_ecp',
]
IGNORED_TESTS = {
'ssl-opt': [
@ -623,6 +631,8 @@ class DriverVSReference_tfm_config(outcome_analysis.DriverVSReference):
'ecp', 'ecdsa', 'ecdh', 'ecjpake',
'bignum_core', 'bignum_random', 'bignum_mod', 'bignum_mod_raw',
'bignum.generated', 'bignum.misc',
# Unit tests for the built-in implementation
'psa_crypto_ecp',
]
IGNORED_TESTS = {
'test_suite_config': [

82
tests/suites/test_suite_psa_crypto_ecp.data Normal file
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@ -0,0 +1,82 @@
ECC generate: unknown family (0)
generate_key:0:256:64:PSA_ERROR_NOT_SUPPORTED
ECC generate: unknown family (0xff)
generate_key:0xff:256:64:PSA_ERROR_NOT_SUPPORTED
ECC generate: SECP_R1 bad bit-size (0)
generate_key:PSA_ECC_FAMILY_SECP_R1:0:64:PSA_ERROR_NOT_SUPPORTED
ECC generate: SECP_R1 bad bit-size (512)
generate_key:PSA_ECC_FAMILY_SECP_R1:512:64:PSA_ERROR_NOT_SUPPORTED
ECC generate: SECP_R1 bad bit-size (528)
generate_key:PSA_ECC_FAMILY_SECP_R1:528:64:PSA_ERROR_NOT_SUPPORTED
ECC generate: SECP_R1 256-bit not supported
depends_on:!MBEDTLS_PSA_BUILTIN_ECC_SECP_R1_256
generate_key:PSA_ECC_FAMILY_SECP_R1:256:32:PSA_ERROR_NOT_SUPPORTED
ECC generate: SECP_R1 384-bit not supported
depends_on:!MBEDTLS_PSA_BUILTIN_ECC_SECP_R1_384
generate_key:PSA_ECC_FAMILY_SECP_R1:384:48:PSA_ERROR_NOT_SUPPORTED
ECC generate: SECP_R1 521-bit not supported
depends_on:!MBEDTLS_PSA_BUILTIN_ECC_SECP_R1_521
generate_key:PSA_ECC_FAMILY_SECP_R1:521:66:PSA_ERROR_NOT_SUPPORTED
ECC generate: SECP_K1 256-bit not supported
depends_on:!MBEDTLS_PSA_BUILTIN_ECC_SECP_K1_256
generate_key:PSA_ECC_FAMILY_SECP_K1:256:32:PSA_ERROR_NOT_SUPPORTED
ECC generate: Curve25519 not supported
depends_on:!MBEDTLS_PSA_BUILTIN_ECC_MONTGOMERY_255
generate_key:PSA_ECC_FAMILY_MONTGOMERY:255:32:PSA_ERROR_NOT_SUPPORTED
ECC generate: Curve448 not supported
depends_on:!MBEDTLS_PSA_BUILTIN_ECC_MONTGOMERY_448
generate_key:PSA_ECC_FAMILY_MONTGOMERY:448:56:PSA_ERROR_NOT_SUPPORTED
ECC generate: SECP_R1 256-bit, size=31, too small
depends_on:MBEDTLS_PSA_BUILTIN_ECC_SECP_R1_256
generate_key:PSA_ECC_FAMILY_SECP_R1:256:31:PSA_ERROR_BUFFER_TOO_SMALL
ECC generate: SECP_R1 256-bit, size=32, ok
depends_on:MBEDTLS_PSA_BUILTIN_ECC_SECP_R1_256
generate_key:PSA_ECC_FAMILY_SECP_R1:256:32:PSA_SUCCESS
ECC generate: SECP_R1 256-bit, size=33, ok
depends_on:MBEDTLS_PSA_BUILTIN_ECC_SECP_R1_256
generate_key:PSA_ECC_FAMILY_SECP_R1:256:33:PSA_SUCCESS
ECC generate: SECP_R1 521-bit, size=65, too small
depends_on:MBEDTLS_PSA_BUILTIN_ECC_SECP_R1_521
generate_key:PSA_ECC_FAMILY_SECP_R1:521:65:PSA_ERROR_BUFFER_TOO_SMALL
ECC generate: SECP_R1 521-bit, size=66, ok
depends_on:MBEDTLS_PSA_BUILTIN_ECC_SECP_R1_521
generate_key:PSA_ECC_FAMILY_SECP_R1:521:66:PSA_SUCCESS
ECC generate: Curve25519, size=31, too small
depends_on:MBEDTLS_PSA_BUILTIN_ECC_MONTGOMERY_255
generate_key:PSA_ECC_FAMILY_MONTGOMERY:255:31:PSA_ERROR_BUFFER_TOO_SMALL
ECC generate: Curve25519, size=32, ok
depends_on:MBEDTLS_PSA_BUILTIN_ECC_MONTGOMERY_255
generate_key:PSA_ECC_FAMILY_MONTGOMERY:255:32:PSA_SUCCESS
ECC generate: Curve25519, size=33, ok
depends_on:MBEDTLS_PSA_BUILTIN_ECC_MONTGOMERY_255
generate_key:PSA_ECC_FAMILY_MONTGOMERY:255:33:PSA_SUCCESS
ECC generate: Curve448, size=55, too small
depends_on:MBEDTLS_PSA_BUILTIN_ECC_MONTGOMERY_448
generate_key:PSA_ECC_FAMILY_MONTGOMERY:448:55:PSA_ERROR_BUFFER_TOO_SMALL
ECC generate: Curve448, size=56, ok
depends_on:MBEDTLS_PSA_BUILTIN_ECC_MONTGOMERY_448
generate_key:PSA_ECC_FAMILY_MONTGOMERY:448:56:PSA_SUCCESS
ECC generate: Curve448, size=57, ok
depends_on:MBEDTLS_PSA_BUILTIN_ECC_MONTGOMERY_448
generate_key:PSA_ECC_FAMILY_MONTGOMERY:448:57:PSA_SUCCESS

165
tests/suites/test_suite_psa_crypto_ecp.function Normal file
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@ -0,0 +1,165 @@
/* BEGIN_HEADER */
/* Unit tests for internal functions for built-in ECC mechanisms. */
#include <psa/crypto.h>
#include "psa_crypto_ecp.h"
#if defined(MBEDTLS_PSA_BUILTIN_KEY_TYPE_ECC_KEY_PAIR_GENERATE)
/*
* Check if a buffer is all-0 bytes:
* return 1 if it is,
* 0 if it isn't.
*
* TODO: we use this in multiple test suites. Move it to tests/src.
*/
static int buffer_is_all_zero(const uint8_t *buf, size_t size)
{
for (size_t i = 0; i < size; i++) {
if (buf[i] != 0) {
return 0;
}
}
return 1;
}
typedef struct {
unsigned bit_bot; /* lowest non-forced bit */
unsigned bit_top; /* highest non-forced bit */
} ecc_private_key_stats_t;
/* Do some sanity checks on an ECC private key. This is not intended to be
* a full validity check, just to catch some potential mistakes. */
static int check_ecc_private_key(psa_ecc_family_t family, size_t bits,
const uint8_t *key, size_t key_length,
ecc_private_key_stats_t *stats)
{
int ok = 0;
/* Check the expected length (same calculation for all curves). */
TEST_EQUAL(PSA_BITS_TO_BYTES(bits), key_length);
/* All-bits zero is invalid and means no key material was copied to the
* output buffer, or a grave RNG pluming failure. */
TEST_ASSERT(!buffer_is_all_zero(key, key_length));
/* Check the top byte of the value for non-byte-aligned curve sizes.
* This is a partial endianness check. */
if (bits % 8 != 0) {
/* All supported non-byte-aligned curve sizes are for Weierstrass
* curves with a big-endian representation. */
uint8_t top_byte = key[0];
uint8_t mask = 0xff << (bits & 8);
TEST_EQUAL(top_byte & mask, 0);
}
/* Check masked bits on Curve25519 and Curve448 scalars.
* See RFC 7748 \S4.1 (we expect the "decoded" form here). */
#if defined(MBEDTLS_PSA_BUILTIN_ECC_MONTGOMERY_255)
if (family == PSA_ECC_FAMILY_MONTGOMERY && bits == 255) {
TEST_EQUAL(key[0] & 0xf8, key[0]);
TEST_EQUAL(key[31] & 0xc0, 0x40);
}
#endif /* MBEDTLS_PSA_BUILTIN_ECC_MONTGOMERY_255 */
#if defined(MBEDTLS_PSA_BUILTIN_ECC_MONTGOMERY_448)
if (family == PSA_ECC_FAMILY_MONTGOMERY && bits == 448) {
TEST_EQUAL(key[0] & 0xfc, key[0]);
TEST_EQUAL(key[55] & 0x80, 0x80);
}
#endif /* MBEDTLS_PSA_BUILTIN_ECC_MONTGOMERY_448 */
/* Don't bother to check that the value is in the exact permitted range
* (1 to p-1 for Weierstrass curves, 2^{n-1} to p-1 for Montgomery curves).
* We would need to bring in bignum machinery, and on most curves
* the probability of a number being out of range is negligible.
*/
/* Collect statistics on random-valued bits */
/* Defaults for big-endian numbers */
uint8_t bit_bot_mask = 0x01;
size_t bit_bot_index = key_length - 1;
uint8_t bit_top_mask = (bits % 8 == 0 ? 0x80 : 1 << (bits % 8 - 1));
size_t bit_top_index = 0;
if (family == PSA_ECC_FAMILY_MONTGOMERY) {
bit_bot_index = 0;
bit_top_index = key_length - 1;
if (bits == 255) {
bit_bot_mask = 0x08;
bit_top_mask = 0x20;
} else {
bit_bot_mask = 0x04;
bit_top_mask = 0x40;
}
}
if (key[bit_bot_index] & bit_bot_mask) {
++stats->bit_bot;
}
if (key[bit_top_index] & bit_top_mask) {
++stats->bit_top;
}
ok = 1;
exit:
return ok;
}
#endif
/* END_HEADER */
/* BEGIN_DEPENDENCIES
* depends_on:MBEDTLS_PSA_CRYPTO_C:MBEDTLS_PSA_BUILTIN_KEY_TYPE_ECC_PUBLIC_KEY
* END_DEPENDENCIES
*/
/* BEGIN_CASE depends_on:MBEDTLS_PSA_BUILTIN_KEY_TYPE_ECC_KEY_PAIR_GENERATE */
void generate_key(int family_arg, int bits_arg,
int output_size_arg,
psa_status_t expected_status)
{
psa_ecc_family_t family = family_arg;
size_t bits = bits_arg;
size_t output_size = output_size_arg;
uint8_t *output = NULL;
size_t output_length = SIZE_MAX;
psa_key_attributes_t attributes = PSA_KEY_ATTRIBUTES_INIT;
psa_set_key_type(&attributes, PSA_KEY_TYPE_ECC_KEY_PAIR(family));
psa_set_key_bits(&attributes, bits);
ecc_private_key_stats_t stats = { 0, 0 };
PSA_INIT();
TEST_CALLOC(output, output_size);
/* In success cases, run multiple iterations so that we can make
* statistical observations. */
unsigned iteration_count = expected_status == PSA_SUCCESS ? 256 : 1;
for (unsigned i = 0; i < iteration_count; i++) {
mbedtls_test_set_step(i);
TEST_EQUAL(mbedtls_psa_ecp_generate_key(&attributes,
output, output_size,
&output_length),
expected_status);
if (expected_status == PSA_SUCCESS) {
TEST_LE_U(output_length, output_size);
TEST_ASSERT(check_ecc_private_key(family, bits,
output, output_length,
&stats));
}
}
if (expected_status == PSA_SUCCESS) {
/* For selected bits, check that we saw the values 0 and 1 each
* at least some minimum number of times. The iteration count and
* the minimum are chosen so that a random failure is unlikely
* to more than cryptographic levels. */
unsigned const min_times = 10;
TEST_LE_U(min_times, stats.bit_bot);
TEST_LE_U(stats.bit_bot, iteration_count - min_times);
TEST_LE_U(min_times, stats.bit_top);
TEST_LE_U(stats.bit_top, iteration_count - min_times);
}
exit:
PSA_DONE();
mbedtls_free(output);
}
/* END_CASE */