pk: minor fix to code and comments

Signed-off-by: Valerio Setti <valerio.setti@nordicsemi.no>

Author: valeriosetti

library/pk.c

@@ -819,7 +819,7 @@ int mbedtls_pk_check_pair(const mbedtls_pk_context *pub,
     if (pub->pk_info->type != MBEDTLS_PK_RSA) {
         return prv->pk_info->check_pair_func(pub, prv, f_rng, p_rng);
     } else
-#endif
+#endif /* MBEDTLS_USE_PSA_CRYPTO */
     return prv->pk_info->check_pair_func(pub->pk_ctx, prv->pk_ctx, f_rng, p_rng);
 }
 

library/pkparse.c

@@ -471,9 +471,9 @@ static int pk_use_ecparams(const mbedtls_asn1_buf *params, mbedtls_pk_context *p
         if ((ret = pk_group_id_from_specified(params, &grp_id)) != 0) {
             return ret;
         }
-#else
+#else /* MBEDTLS_PK_PARSE_EC_EXTENDED */
         return MBEDTLS_ERR_PK_KEY_INVALID_FORMAT;
-#endif
+#endif /* MBEDTLS_PK_PARSE_EC_EXTENDED */
     }
 
     ec_family = mbedtls_ecc_group_to_psa(grp_id, &bits);
@@ -588,7 +588,7 @@ static int pk_get_ecpubkey(unsigned char **p, const unsigned char *end,
 
     return 0;
 }
-#else /* MBEDTLS_USE_PSA_CRYPTO*/
+#else /* MBEDTLS_USE_PSA_CRYPTO */
 /*
  * Use EC parameters to initialise an EC group
  *
@@ -1125,9 +1125,9 @@ static int pk_parse_key_sec1_der(mbedtls_ecp_keypair *eck,
 
 #if defined(MBEDTLS_USE_PSA_CRYPTO)
             if ((ret = pk_get_ecpubkey(&p, end2, pk)) == 0) {
-#else
+#else /* MBEDTLS_USE_PSA_CRYPTO */
             if ((ret = pk_get_ecpubkey(&p, end2, eck)) == 0) {
-#endif
+#endif /* MBEDTLS_USE_PSA_CRYPTO */
                 pubkey_done = 1;
             } else {
                 /*

library/pkwrite.c

@@ -112,7 +112,7 @@ static int pk_write_ec_pubkey(unsigned char **p, unsigned char *start,
 
     len = pk->pk_raw_len;
 
-    if ((*p - start) < (long int) len) {
+    if (((size_t) (*p - start)) < len) {
         return MBEDTLS_ERR_PK_BUFFER_TOO_SMALL;
     }