d2i_ECPrivateKey: split private key setting into a helper

Contrary to domain parameters and public key, the private key most be
part of the DER. Convert that to a BIGNUM and set it on the EC_KEY.
Use the dedicated setter for this (which will possibly call the handler
of the EC_KEY_METHOD) rather than doing this by hand.

ok jsing

1 files changed, 31 insertions, 14 deletions

diff --git a/src/lib/libcrypto/ec/ec_asn1.c b/src/lib/libcrypto/ec/ec_asn1.c
index 1ba1e36435..5234d4380a 100644
--- a/src/lib/libcrypto/ec/ec_asn1.c
+++ b/src/lib/libcrypto/ec/ec_asn1.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: ec_asn1.c,v 1.90 2024/10/28 17:58:18 tb Exp $ */
+/* $OpenBSD: ec_asn1.c,v 1.91 2024/10/28 17:59:45 tb Exp $ */
 /*
  * Written by Nils Larsch for the OpenSSL project.
  */
@@ -1113,6 +1113,35 @@ ec_key_set_group_from_parameters(EC_KEY *ec_key, const ECPKPARAMETERS *params)
         return ret;
 }
 
+static int
+ec_key_set_private_key(EC_KEY *ec_key, const ASN1_OCTET_STRING *aos)
+{
+        BIGNUM *priv_key = NULL;
+        int ret = 0;
+
+        if (aos == NULL) {
+                ECerror(EC_R_MISSING_PRIVATE_KEY);
+                goto err;
+        }
+
+        /*
+         * XXX - Sec 1, C.4 requires that this octet string be padded to the
+         * byte length of the group's order. This can't be enforced because
+         * i2d_ECPrivateKey() produces a semi-compatible ad hoc format.
+         */
+        if ((priv_key = BN_bin2bn(aos->data, aos->length, NULL)) == NULL)
+                goto err;
+        if (!EC_KEY_set_private_key(ec_key, priv_key))
+                goto err;
+
+        ret = 1;
+
+ err:
+        BN_free(priv_key);
+
+        return ret;
+}
+
 EC_KEY *
 d2i_ECPrivateKey(EC_KEY **out_ec_key, const unsigned char **in, long len)
 {
@@ -1132,20 +1161,8 @@ d2i_ECPrivateKey(EC_KEY **out_ec_key, const unsigned char **in, long len)
         ec_key->version = ec_privatekey->version;
         if (!ec_key_set_group_from_parameters(ec_key, ec_privatekey->parameters))
                 goto err;
-
-        if (ec_privatekey->privateKey) {
-                ec_key->priv_key = BN_bin2bn(
-                    ASN1_STRING_data(ec_privatekey->privateKey),
-                    ASN1_STRING_length(ec_privatekey->privateKey),
-                    ec_key->priv_key);
-                if (ec_key->priv_key == NULL) {
-                        ECerror(ERR_R_BN_LIB);
-                        goto err;
-                }
-        } else {
-                ECerror(EC_R_MISSING_PRIVATE_KEY);
+        if (!ec_key_set_private_key(ec_key, ec_privatekey->privateKey))
                 goto err;
-        }
 
         if (ec_key->pub_key)
                 EC_POINT_free(ec_key->pub_key);