Add seckey extraction from keypair to the extrakeys tests

Author: elichai

src/modules/extrakeys/tests_impl.h

@@ -311,6 +311,7 @@ void test_xonly_pubkey_tweak_recursive(void) {
 
 void test_keypair(void) {
     unsigned char sk[32];
+    unsigned char sk_tmp[32];
     unsigned char zeros96[96] = { 0 };
     unsigned char overflows[32];
     secp256k1_keypair keypair;
@@ -396,6 +397,28 @@ void test_keypair(void) {
     CHECK(secp256k1_memcmp_var(&xonly_pk, &xonly_pk_tmp, sizeof(pk)) == 0);
     CHECK(pk_parity == pk_parity_tmp);
 
+    /* Test keypair_seckey */
+    ecount = 0;
+    secp256k1_testrand256(sk);
+    CHECK(secp256k1_keypair_create(ctx, &keypair, sk) == 1);
+    CHECK(secp256k1_keypair_sec(none, sk_tmp, &keypair) == 1);
+    CHECK(secp256k1_keypair_sec(none, NULL, &keypair) == 0);
+    CHECK(ecount == 1);
+    CHECK(secp256k1_keypair_sec(none, sk_tmp, NULL) == 0);
+    CHECK(ecount == 2);
+    CHECK(secp256k1_memcmp_var(zeros96, sk_tmp, sizeof(sk_tmp)) == 0);
+
+    /* keypair returns the same seckey it got */
+    CHECK(secp256k1_keypair_create(sign, &keypair, sk) == 1);
+    CHECK(secp256k1_keypair_sec(none, sk_tmp, &keypair) == 1);
+    CHECK(secp256k1_memcmp_var(sk, sk_tmp, sizeof(sk_tmp)) == 0);
+
+
+    /* Using an invalid keypair is fine for keypair_seckey */
+    memset(&keypair, 0, sizeof(keypair));
+    CHECK(secp256k1_keypair_sec(none, sk_tmp, &keypair) == 1);
+    CHECK(secp256k1_memcmp_var(zeros96, sk_tmp, sizeof(sk_tmp)) == 0);
+
     secp256k1_context_destroy(none);
     secp256k1_context_destroy(sign);
     secp256k1_context_destroy(verify);
@@ -484,6 +507,7 @@ void test_keypair_add(void) {
         secp256k1_pubkey output_pk_xy;
         secp256k1_pubkey output_pk_expected;
         unsigned char pk32[32];
+        unsigned char sk32[32];
         int pk_parity;
 
         secp256k1_testrand256(tweak);
@@ -501,7 +525,8 @@ void test_keypair_add(void) {
         CHECK(secp256k1_memcmp_var(&output_pk_xy, &output_pk_expected, sizeof(output_pk_xy)) == 0);
 
         /* Check that the secret key in the keypair is tweaked correctly */
-        CHECK(secp256k1_ec_pubkey_create(ctx, &output_pk_expected, &keypair.data[0]) == 1);
+        CHECK(secp256k1_keypair_sec(none, sk32, &keypair) == 1);
+        CHECK(secp256k1_ec_pubkey_create(ctx, &output_pk_expected, sk32) == 1);
         CHECK(secp256k1_memcmp_var(&output_pk_xy, &output_pk_expected, sizeof(output_pk_xy)) == 0);
     }
     secp256k1_context_destroy(none);