From 0c91c5604130a56bb1628fd12c56edf60de966b0 Mon Sep 17 00:00:00 2001
From: Sebastian Falbesoner <sebastian.falbesoner@gmail.com>
Date: Fri, 12 Sep 2025 03:53:06 +0200
Subject: [PATCH] test: introduce group order byte-array constant for
 deduplication

---
 src/modules/ecdh/tests_impl.h |  8 ++------
 src/tests.c                   | 22 +++-------------------
 src/testutil.h                |  8 ++++++++
 3 files changed, 13 insertions(+), 25 deletions(-)

diff --git a/src/modules/ecdh/tests_impl.h b/src/modules/ecdh/tests_impl.h
index 6888f18c64..8265131105 100644
--- a/src/modules/ecdh/tests_impl.h
+++ b/src/modules/ecdh/tests_impl.h
@@ -90,12 +90,7 @@ static void test_ecdh_generator_basepoint(void) {
 
 static void test_bad_scalar(void) {
     unsigned char s_zero[32] = { 0 };
-    unsigned char s_overflow[32] = {
-        0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
-        0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xfe,
-        0xba, 0xae, 0xdc, 0xe6, 0xaf, 0x48, 0xa0, 0x3b,
-        0xbf, 0xd2, 0x5e, 0x8c, 0xd0, 0x36, 0x41, 0x41
-    };
+    unsigned char s_overflow[32] = { 0 };
     unsigned char s_rand[32] = { 0 };
     unsigned char output[32];
     secp256k1_scalar rand;
@@ -107,6 +102,7 @@ static void test_bad_scalar(void) {
     CHECK(secp256k1_ec_pubkey_create(CTX, &point, s_rand) == 1);
 
     /* Try to multiply it by bad values */
+    memcpy(s_overflow, secp256k1_group_order_bytes, 32);
     CHECK(secp256k1_ecdh(CTX, output, &point, s_zero, NULL, NULL) == 0);
     CHECK(secp256k1_ecdh(CTX, output, &point, s_overflow, NULL, NULL) == 0);
     /* ...and a good one */
diff --git a/src/tests.c b/src/tests.c
index 28bec5904c..cb3b3c4248 100644
--- a/src/tests.c
+++ b/src/tests.c
@@ -6036,12 +6036,7 @@ static void run_ec_pubkey_parse_test(void) {
 }
 
 static void run_eckey_edge_case_test(void) {
-    const unsigned char orderc[32] = {
-        0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
-        0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xfe,
-        0xba, 0xae, 0xdc, 0xe6, 0xaf, 0x48, 0xa0, 0x3b,
-        0xbf, 0xd2, 0x5e, 0x8c, 0xd0, 0x36, 0x41, 0x41
-    };
+    const unsigned char *orderc = secp256k1_group_order_bytes;
     const unsigned char zeros[sizeof(secp256k1_pubkey)] = {0x00};
     unsigned char ctmp[33];
     unsigned char ctmp2[33];
@@ -6355,13 +6350,7 @@ static int nonce_function_test_retry(unsigned char *nonce32, const unsigned char
        return 1;
    }
    if (counter < 5) {
-       static const unsigned char order[] = {
-           0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,
-           0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFE,
-           0xBA,0xAE,0xDC,0xE6,0xAF,0x48,0xA0,0x3B,
-           0xBF,0xD2,0x5E,0x8C,0xD0,0x36,0x41,0x41
-       };
-       memcpy(nonce32, order, 32);
+       memcpy(nonce32, secp256k1_group_order_bytes, 32);
        if (counter == 4) {
            nonce32[31]++;
        }
@@ -7379,12 +7368,7 @@ static void test_ecdsa_edge_cases(void) {
     /* Privkey export where pubkey is the point at infinity. */
     {
         unsigned char privkey[300];
-        unsigned char seckey[32] = {
-            0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
-            0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xfe,
-            0xba, 0xae, 0xdc, 0xe6, 0xaf, 0x48, 0xa0, 0x3b,
-            0xbf, 0xd2, 0x5e, 0x8c, 0xd0, 0x36, 0x41, 0x41,
-        };
+        const unsigned char *seckey = secp256k1_group_order_bytes;
         size_t outlen = 300;
         CHECK(!ec_privkey_export_der(CTX, privkey, &outlen, seckey, 0));
         outlen = 300;
diff --git a/src/testutil.h b/src/testutil.h
index 64b3bb41c0..480f6a1a0c 100644
--- a/src/testutil.h
+++ b/src/testutil.h
@@ -11,6 +11,14 @@
 #include "testrand.h"
 #include "util.h"
 
+/* group order of the secp256k1 curve in 32-byte big endian representation */
+static const unsigned char secp256k1_group_order_bytes[32] = {
+    0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
+    0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xfe,
+    0xba, 0xae, 0xdc, 0xe6, 0xaf, 0x48, 0xa0, 0x3b,
+    0xbf, 0xd2, 0x5e, 0x8c, 0xd0, 0x36, 0x41, 0x41
+};
+
 static void testutil_random_fe(secp256k1_fe *x) {
     unsigned char bin[32];
     do {