EC key pair import: check the buffer size

When importing a private elliptic curve key, require the input to have
exactly the right size. RFC 5915 requires the right size (you aren't
allow to omit leading zeros). A different buffer size likely means
that something is wrong, e.g. a mismatch between the declared key type
and the actual data.

Author: gilles-peskine-arm

library/psa_crypto.c

@@ -621,6 +621,9 @@ static psa_status_t psa_import_ec_private_key( psa_ecc_curve_t curve,
     mbedtls_ecp_keypair *ecp = NULL;
     mbedtls_ecp_group_id grp_id = mbedtls_ecc_group_of_psa( curve );
 
+    if( PSA_BITS_TO_BYTES( PSA_ECC_CURVE_BITS( curve ) ) != data_length )
+        return( PSA_ERROR_INVALID_ARGUMENT );
+
     *p_ecp = NULL;
     ecp = mbedtls_calloc( 1, sizeof( mbedtls_ecp_keypair ) );
     if( ecp == NULL )

tests/suites/test_suite_psa_crypto.data

@@ -243,6 +243,10 @@ PSA import EC keypair: DER format
 depends_on:MBEDTLS_PK_PARSE_C:MBEDTLS_ECP_C:MBEDTLS_ECP_DP_SECP256R1_ENABLED
 import:"3077020101042049c9a8c18c4b885638c431cf1df1c994131609b580d4fd43a0cab17db2f13eeea00a06082a8648ce3d030107a144034200047772656f814b399279d5e1f1781fac6f099a3c5ca1b0e35351834b08b65e0b572590cdaf8f769361bcf34acfc11e5e074e8426bdde04be6e653945449617de45":PSA_KEY_TYPE_ECC_KEYPAIR(PSA_ECC_CURVE_SECP256R1):PSA_ERROR_INVALID_ARGUMENT
 
+PSA import EC keypair: too short
+depends_on:MBEDTLS_PK_PARSE_C:MBEDTLS_ECP_C:MBEDTLS_ECP_DP_SECP256R1_ENABLED
+import:"0123456789abcdef0123456789abcdef":PSA_KEY_TYPE_ECC_KEYPAIR(PSA_ECC_CURVE_SECP256R1):PSA_ERROR_INVALID_ARGUMENT
+
 PSA import EC keypair: public key
 depends_on:MBEDTLS_PK_PARSE_C:MBEDTLS_ECP_C:MBEDTLS_ECP_DP_SECP256R1_ENABLED
 import:"04dea5e45d0ea37fc566232a508f4ad20ea13d47e4bf5fa4d54a57a0ba012042087097496efc583fed8b24a5b9be9a51de063f5a00a8b698a16fd7f29b5485f320":PSA_KEY_TYPE_ECC_KEYPAIR(PSA_ECC_CURVE_SECP256R1):PSA_ERROR_INVALID_ARGUMENT