ecdh: test NULL-checking of arguments

apoelstra · apoelstra · commit 6f8ae2f3c06a · 2016-11-26T20:17:14.000Z
Boosts the ECDH module to 100% coverage
diff --git a/src/modules/ecdh/main_impl.h b/src/modules/ecdh/main_impl.h
@@ -16,10 +16,10 @@ int secp256k1_ecdh(const secp256k1_context* ctx, unsigned char *result, const se
     secp256k1_gej res;
     secp256k1_ge pt;
     secp256k1_scalar s;
+    VERIFY_CHECK(ctx != NULL);
     ARG_CHECK(result != NULL);
     ARG_CHECK(point != NULL);
     ARG_CHECK(scalar != NULL);
-    (void)ctx;
 
     secp256k1_pubkey_load(ctx, &pt, point);
     secp256k1_scalar_set_b32(&s, scalar, &overflow);
diff --git a/src/modules/ecdh/tests_impl.h b/src/modules/ecdh/tests_impl.h
@@ -7,6 +7,35 @@
 #ifndef _SECP256K1_MODULE_ECDH_TESTS_
 #define _SECP256K1_MODULE_ECDH_TESTS_
 
+void test_ecdh_api(void) {
+    /* Setup context that just counts errors */
+    secp256k1_context *tctx = secp256k1_context_create(SECP256K1_CONTEXT_SIGN);
+    secp256k1_pubkey point;
+    unsigned char res[32];
+    unsigned char s_one[32] = { 0 };
+    int32_t ecount = 0;
+    s_one[31] = 1;
+
+    secp256k1_context_set_error_callback(tctx, counting_illegal_callback_fn, &ecount);
+    secp256k1_context_set_illegal_callback(tctx, counting_illegal_callback_fn, &ecount);
+    CHECK(secp256k1_ec_pubkey_create(tctx, &point, s_one) == 1);
+
+    /* Check all NULLs are detected */
+    CHECK(secp256k1_ecdh(tctx, res, &point, s_one) == 1);
+    CHECK(ecount == 0);
+    CHECK(secp256k1_ecdh(tctx, NULL, &point, s_one) == 0);
+    CHECK(ecount == 1);
+    CHECK(secp256k1_ecdh(tctx, res, NULL, s_one) == 0);
+    CHECK(ecount == 2);
+    CHECK(secp256k1_ecdh(tctx, res, &point, NULL) == 0);
+    CHECK(ecount == 3);
+    CHECK(secp256k1_ecdh(tctx, res, &point, s_one) == 1);
+    CHECK(ecount == 3);
+
+    /* Cleanup */
+    secp256k1_context_destroy(tctx);
+}
+
 void test_ecdh_generator_basepoint(void) {
     unsigned char s_one[32] = { 0 };
     secp256k1_pubkey point[2];
@@ -68,6 +97,7 @@ void test_bad_scalar(void) {
 }
 
 void run_ecdh_tests(void) {
+    test_ecdh_api();
     test_ecdh_generator_basepoint();
     test_bad_scalar();
 }
