First cut at key backup code. Not tested yet.

Still missing Python script to drive backup process, and need to do
something about setting the EXPORTABLE key flag for this to be useful.

1 files changed, 13 insertions, 12 deletions

diff --git a/ecdsa.c b/ecdsa.c
index 8a31504..3fc1462 100644
--- a/ecdsa.c
+++ b/ecdsa.c
@@ -258,20 +258,21 @@ static const ecdsa_curve_t * const get_curve(const hal_curve_name_t curve)
   }
 }
 
-static inline const ecdsa_curve_t * oid_to_curve(hal_curve_name_t *curve_name,
-                                                 const uint8_t * const oid,
-                                                 const size_t oid_len)
+hal_error_t hal_ecdsa_oid_to_curve(hal_curve_name_t *curve_name,
+                                   const uint8_t * const oid,
+                                   const size_t oid_len)
 {
-  assert(curve_name != NULL && oid != NULL);
+  if (curve_name == NULL || oid == NULL)
+    return HAL_ERROR_BAD_ARGUMENTS;
 
-  const ecdsa_curve_t *curve = NULL;
   *curve_name = HAL_CURVE_NONE;
+  const ecdsa_curve_t *curve;
 
   while ((curve = get_curve(++*curve_name)) != NULL)
     if (oid_len == curve->oid_len && memcmp(oid, curve->oid, oid_len) == 0)
-      return curve;
+      return HAL_OK;
 
-  return NULL;
+  return HAL_ERROR_UNSUPPORTED_KEY;
 }
 
 /*
@@ -1395,7 +1396,7 @@ hal_error_t hal_ecdsa_private_key_from_der(hal_ecdsa_key_t **key_,
 
   if (alg_oid_len != hal_asn1_oid_ecPublicKey_len ||
       memcmp(alg_oid, hal_asn1_oid_ecPublicKey, alg_oid_len) != 0 ||
-      oid_to_curve(&key->curve, curve_oid, curve_oid_len) == NULL)
+      hal_ecdsa_oid_to_curve(&key->curve, curve_oid, curve_oid_len) != HAL_OK)
     return HAL_ERROR_ASN1_PARSE_FAILED;
 
   if ((err = hal_asn1_decode_header(ASN1_SEQUENCE, privkey, privkey_len, &hlen, &vlen)) != HAL_OK)
@@ -1516,19 +1517,19 @@ hal_error_t hal_ecdsa_public_key_from_der(hal_ecdsa_key_t **key_,
 
   const uint8_t *alg_oid = NULL, *curve_oid = NULL, *pubkey = NULL;
   size_t         alg_oid_len,     curve_oid_len,     pubkey_len;
-  const ecdsa_curve_t *curve;
   hal_error_t err;
 
-  if ((err = hal_asn1_decode_spki(&alg_oid, &alg_oid_len, &curve_oid, &curve_oid_len, &pubkey, &pubkey_len,
+  if ((err = hal_asn1_decode_spki(&alg_oid, &alg_oid_len, &curve_oid, &curve_oid_len,
+                                  &pubkey, &pubkey_len,
                                   der, der_len)) != HAL_OK)
     return err;
 
   if (alg_oid == NULL || curve_oid == NULL || pubkey == NULL ||
       alg_oid_len != hal_asn1_oid_ecPublicKey_len ||
       memcmp(alg_oid, hal_asn1_oid_ecPublicKey, alg_oid_len) != 0 ||
-      (curve = oid_to_curve(&key->curve, curve_oid, curve_oid_len)) == NULL ||
+      hal_ecdsa_oid_to_curve(&key->curve, curve_oid, curve_oid_len) != HAL_OK ||
       pubkey_len < 3 || (pubkey_len & 1) == 0 || pubkey[0] != 0x04 ||
-      pubkey_len / 2 != fp_unsigned_bin_size(unconst_fp_int(curve->q)))
+      pubkey_len / 2 != fp_unsigned_bin_size(unconst_fp_int(get_curve(key->curve)->q)))
     return HAL_ERROR_ASN1_PARSE_FAILED;
 
   const uint8_t * const Qx = pubkey + 1;