Add test vector for ECDSA secp256k1

test/ecdsa_test_vectors.c

diff --git a/test/ecdsa_test_vectors.c b/test/ecdsa_test_vectors.c
new file mode 100644
index 0000000..1e902b2
--- /dev/null
+++ b/test/ecdsa_test_vectors.c
@@ -0,0 +1,128 @@
+/* Copyright 2020, Kenneth MacKay. Licensed under the BSD 2-clause license. */
+
+#include "uECC.h"
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+
+typedef struct {
+  const char* private_key;
+  const char* public_key;
+  const char* k;
+  const char* hash;
+  const char* r;
+  const char* s;
+} Test;
+
+Test secp256k1_tests[] = {
+    {
+        "ebb2c082fd7727890a28ac82f6bdf97bad8de9f5d7c9028692de1a255cad3e0f",
+        "779dd197a5df977ed2cf6cb31d82d43328b790dc6b3b7d4437a427bd5847dfcde94b724a555b6d017bb7607c3e3281daf5b1699d6ef4124975c9237b917d426f",
+        "49a0d7b786ec9cde0d0721d72804befd06571c974b191efb42ecf322ba9ddd9a",
+        "4b688df40bcedbe641ddb16ff0a1842d9c67ea1c3bf63f3e0471baa664531d1a",
+        "241097efbf8b63bf145c8961dbdf10c310efbb3b2676bbc0f8b08505c9e2f795",
+        "021006b7838609339e8b415a7f9acb1b661828131aef1ecbc7955dfb01f3ca0e"
+    },
+};
+
+extern int uECC_sign_with_k(const uint8_t *private_key,
+                            const uint8_t *message_hash,
+                            unsigned hash_size,
+                            const uint8_t *k,
+                            uint8_t *signature,
+                            uECC_Curve curve);
+
+
+void vli_print(uint8_t *vli, unsigned int size) {
+    for(unsigned i=0; i<size; ++i) {
+        printf("%02X ", (unsigned)vli[i]);
+    }
+    printf("\n");
+}
+
+void strtobytes(const char* str, uint8_t* bytes, int count) {
+  for (int c = 0; c < count; ++c) {
+    if (sscanf(str, "%2hhx", &bytes[c]) != 1) {
+      printf("Failed to read string to bytes");
+      exit(1);
+    }
+    str += 2;
+  }
+}
+
+int run(Test* tests, int num_tests, uECC_Curve curve) {
+    uint8_t private[32] = {0};
+    uint8_t public[64] = {0};
+    uint8_t k[32] = {0};
+    uint8_t hash[32] = {0};
+    uint8_t r[32] = {0};
+    uint8_t s[32] = {0};
+
+    uint8_t signature[64] = {0};
+
+    int result;
+    int i;
+    int private_key_size;
+    int public_key_size;
+    int all_success = 1;
+
+    private_key_size = uECC_curve_private_key_size(curve);
+    public_key_size = uECC_curve_public_key_size(curve);
+
+    for (i = 0; i < num_tests; ++i) {
+        strtobytes(tests[i].private_key, private, private_key_size);
+        strtobytes(tests[i].public_key, public, public_key_size);
+        strtobytes(tests[i].k, k, private_key_size);
+        strtobytes(tests[i].hash, hash, private_key_size);
+        strtobytes(tests[i].r, r, private_key_size);
+        strtobytes(tests[i].s, s, private_key_size);
+
+        result = uECC_sign_with_k(private, hash, private_key_size, k, signature, curve);
+        if (!result) {
+            all_success = 0;
+            printf("  Sign failed for test %d\n", i);
+        }
+        if (result) {
+            if (memcmp(signature, r, private_key_size) != 0) {
+                all_success = 0;
+                printf("  Got incorrect r for test %d\n", i);
+                printf("    Expected: ");
+                vli_print(r, private_key_size);
+                printf("    Calculated: ");
+                vli_print(signature, private_key_size);
+            }
+            if (memcmp(signature + private_key_size, s, private_key_size) != 0) {
+                all_success = 0;
+                printf("  Got incorrect s for test %d\n", i);
+                printf("    Expected: ");
+                vli_print(s, private_key_size);
+                printf("    Calculated: ");
+                vli_print(signature + private_key_size, private_key_size);
+            }
+
+            result = uECC_verify(public, hash, private_key_size, signature, curve);
+            if (!result) {
+                printf("  Verify failed for test %d\n", i);
+            }
+        }
+    }
+
+    return all_success;
+}
+
+#define RUN_TESTS(curve) \
+    printf(#curve ":\n"); \
+    if (run(curve##_tests, sizeof(curve##_tests) / sizeof(curve##_tests[0]), uECC_##curve()) ) { \
+        printf("  All passed\n"); \
+    } else { \
+        printf("  Failed\n"); \
+    }
+
+int main() {
+#if uECC_SUPPORTS_secp256k1
+    RUN_TESTS(secp256k1)
+#endif
+
+    return 0;
+}

uECC.c

diff --git a/uECC.c b/uECC.c
index b3ff348..a3d502c 100644
--- a/uECC.c
+++ b/uECC.c
@@ -1243,7 +1243,7 @@
     }
 }
 
-static int uECC_sign_with_k(const uint8_t *private_key,
+static int uECC_sign_with_k_internal(const uint8_t *private_key,
                             const uint8_t *message_hash,
                             unsigned hash_size,
                             uECC_word_t *k,
@@ -1326,6 +1326,18 @@
     return 1;
 }
 
+/* For testing - sign with an explicitly specified k value */
+int uECC_sign_with_k(const uint8_t *private_key,
+                            const uint8_t *message_hash,
+                            unsigned hash_size,
+                            const uint8_t *k,
+                            uint8_t *signature,
+                            uECC_Curve curve) {
+    uECC_word_t k2[uECC_MAX_WORDS];
+    bits2int(k2, k, BITS_TO_BYTES(curve->num_n_bits), curve);
+    return uECC_sign_with_k_internal(private_key, message_hash, hash_size, k2, signature, curve);
+}
+
 int uECC_sign(const uint8_t *private_key,
               const uint8_t *message_hash,
               unsigned hash_size,
@@ -1339,7 +1351,7 @@
             return 0;
         }
 
-        if (uECC_sign_with_k(private_key, message_hash, hash_size, k, signature, curve)) {
+        if (uECC_sign_with_k_internal(private_key, message_hash, hash_size, k, signature, curve)) {
             return 1;
         }
     }
@@ -1455,7 +1467,7 @@
                 mask >> ((bitcount_t)(num_n_words * uECC_WORD_SIZE * 8 - num_n_bits));
         }
 
-        if (uECC_sign_with_k(private_key, message_hash, hash_size, T, signature, curve)) {
+        if (uECC_sign_with_k_internal(private_key, message_hash, hash_size, T, signature, curve)) {
             return 1;
         }