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mbedtls_pk_import_into_psa: fix Montgomery keys in the legacy case

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Fix the workaround for the weirdness of mbedtls_ecp_write_key(), which
assumed a Weierstrass key.

This fixes the Montgomery private key parse tests in test_suite_pkparse.

Signed-off-by: Gilles Peskine <Gilles.Peskine@arm.com>
This commit is contained in:
Gilles Peskine 2024-02-15 17:26:07 +01:00
parent 2ec141a429
commit 83b8baf899
1 changed files with 8 additions and 6 deletions
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14
library/pk.c
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@ -704,17 +704,19 @@ static int import_pair_into_psa(const mbedtls_pk_context *pk,
return MBEDTLS_ERR_PK_TYPE_MISMATCH;
}
unsigned char key_buffer[PSA_BITS_TO_BYTES(PSA_VENDOR_ECC_MAX_CURVE_BITS)];
int ret = mbedtls_ecp_write_key(ec,
key_buffer, sizeof(key_buffer));
/* Make sure to pass the exact key length to
* mbedtls_ecp_write_key(), because it writes Montgomery keys
* at the start of the buffer but Weierstrass keys at the
* end of the buffer. */
size_t key_length = PSA_BITS_TO_BYTES(ec->grp.nbits);
int ret = mbedtls_ecp_write_key(ec, key_buffer, key_length);
if (ret < 0) {
return ret;
}
size_t key_length = PSA_BITS_TO_BYTES(ec->grp.nbits);
unsigned char *key_data = key_buffer + sizeof(key_buffer) - key_length;
ret = PSA_PK_TO_MBEDTLS_ERR(psa_import_key(attributes,
key_data, key_length,
key_buffer, key_length,
key_id));
mbedtls_platform_zeroize(key_data, key_length);
mbedtls_platform_zeroize(key_buffer, key_length);
return ret;
#endif /* MBEDTLS_PK_USE_PSA_EC_DATA */
}