Callback data: Accept pointers to either const or non-const data

include/secp256k1.h

@@ -94,7 +94,7 @@ typedef int (*secp256k1_nonce_function_t)(
     const unsigned char *msg32,
     const unsigned char *key32,
     const unsigned char *algo16,
-    const void *data,
+    void *data,
     unsigned int attempt
 );
 
@@ -187,7 +187,7 @@ void secp256k1_context_destroy(
 void secp256k1_context_set_illegal_callback(
     secp256k1_context_t* ctx,
     void (*fun)(const char* message, void* data),
-    void* data
+    const void* data
 ) SECP256K1_ARG_NONNULL(1);
 
 /** Set a callback function to be called when an internal consistency check
@@ -209,7 +209,7 @@ void secp256k1_context_set_illegal_callback(
 void secp256k1_context_set_error_callback(
     secp256k1_context_t* ctx,
     void (*fun)(const char* message, void* data),
-    void* data
+    const void* data
 ) SECP256K1_ARG_NONNULL(1);
 
 /** Parse a variable-length public key into the pubkey object.

src/modules/recovery/main_impl.h

@@ -105,7 +105,7 @@ int secp256k1_ecdsa_sign_recoverable(const secp256k1_context_t* ctx, secp256k1_e
         secp256k1_scalar_set_b32(&msg, msg32, NULL);
         while (1) {
             unsigned char nonce32[32];
-            ret = noncefp(nonce32, seckey, msg32, NULL, noncedata, count);
+            ret = noncefp(nonce32, seckey, msg32, NULL, (void*)noncedata, count);
             if (!ret) {
                 break;
             }

src/modules/schnorr/main_impl.h

@@ -36,7 +36,7 @@ int secp256k1_schnorr_sign(const secp256k1_context_t* ctx, unsigned char *sig64,
     secp256k1_scalar_set_b32(&sec, seckey, NULL);
     while (1) {
         unsigned char nonce32[32];
-        ret = noncefp(nonce32, msg32, seckey, secp256k1_schnorr_algo16, noncedata, count);
+        ret = noncefp(nonce32, msg32, seckey, secp256k1_schnorr_algo16, (void*)noncedata, count);
         if (!ret) {
             break;
         }
@@ -107,7 +107,7 @@ int secp256k1_schnorr_generate_nonce_pair(const secp256k1_context_t* ctx, secp25
 
     do {
         int overflow;
-        ret = noncefp(privnonce32, sec32, msg32, secp256k1_schnorr_algo16, noncedata, count++);
+        ret = noncefp(privnonce32, sec32, msg32, secp256k1_schnorr_algo16, (void*)noncedata, count++);
         if (!ret) {
             break;
         }

src/secp256k1.c

@@ -22,7 +22,7 @@
 
 #define ARG_CHECK(cond) do { \
     if (EXPECT(!(cond), 0)) { \
-        ctx->illegal_callback.fn(#cond, ctx->illegal_callback.data); \
+        secp256k1_callback(&ctx->illegal_callback, #cond); \
         return 0; \
     } \
 } while(0)
@@ -94,14 +94,14 @@ void secp256k1_context_destroy(secp256k1_context_t* ctx) {
     free(ctx);
 }
 
-void secp256k1_context_set_illegal_callback(secp256k1_context_t* ctx, void (*fun)(const char* message, void* data), void* data) {
+void secp256k1_context_set_illegal_callback(secp256k1_context_t* ctx, void (*fun)(const char* message, void* data), const void* data) {
     if (!fun)
         fun = default_illegal_callback_fn;
     ctx->illegal_callback.fn = fun;
     ctx->illegal_callback.data = data;
 }
 
-void secp256k1_context_set_error_callback(secp256k1_context_t* ctx, void (*fun)(const char* message, void* data), void* data) {
+void secp256k1_context_set_error_callback(secp256k1_context_t* ctx, void (*fun)(const char* message, void* data), const void* data) {
     if (!fun)
         fun = default_error_callback_fn;
     ctx->error_callback.fn = fun;
@@ -230,7 +230,7 @@ int secp256k1_ecdsa_verify(const secp256k1_context_t* ctx, const secp256k1_ecdsa
             secp256k1_ecdsa_sig_verify(&ctx->ecmult_ctx, &r, &s, &q, &m));
 }
 
-static int nonce_function_rfc6979(unsigned char *nonce32, const unsigned char *msg32, const unsigned char *key32, const unsigned char *algo16, const void *data, unsigned int counter) {
+static int nonce_function_rfc6979(unsigned char *nonce32, const unsigned char *msg32, const unsigned char *key32, const unsigned char *algo16, void *data, unsigned int counter) {
    unsigned char keydata[112];
    int keylen = 64;
    secp256k1_rfc6979_hmac_sha256_t rng;
@@ -285,7 +285,7 @@ int secp256k1_ecdsa_sign(const secp256k1_context_t* ctx, secp256k1_ecdsa_signatu
         secp256k1_scalar_set_b32(&msg, msg32, NULL);
         while (1) {
             unsigned char nonce32[32];
-            ret = noncefp(nonce32, msg32, seckey, NULL, noncedata, count);
+            ret = noncefp(nonce32, msg32, seckey, NULL, (void*)noncedata, count);
             if (!ret) {
                 break;
             }

src/tests.c

@@ -1787,7 +1787,7 @@ void run_ecdsa_sign_verify(void) {
 }
 
 /** Dummy nonce generation function that just uses a precomputed nonce, and fails if it is not accepted. Use only for testing. */
-static int precomputed_nonce_function(unsigned char *nonce32, const unsigned char *msg32, const unsigned char *key32, const unsigned char *algo16, const void *data, unsigned int counter) {
+static int precomputed_nonce_function(unsigned char *nonce32, const unsigned char *msg32, const unsigned char *key32, const unsigned char *algo16, void *data, unsigned int counter) {
     (void)msg32;
     (void)key32;
     (void)algo16;
@@ -1795,7 +1795,7 @@ static int precomputed_nonce_function(unsigned char *nonce32, const unsigned cha
     return (counter == 0);
 }
 
-static int nonce_function_test_fail(unsigned char *nonce32, const unsigned char *msg32, const unsigned char *key32, const unsigned char *algo16, const void *data, unsigned int counter) {
+static int nonce_function_test_fail(unsigned char *nonce32, const unsigned char *msg32, const unsigned char *key32, const unsigned char *algo16, void *data, unsigned int counter) {
    /* Dummy nonce generator that has a fatal error on the first counter value. */
    if (counter == 0) {
        return 0;
@@ -1803,7 +1803,7 @@ static int nonce_function_test_fail(unsigned char *nonce32, const unsigned char
    return nonce_function_rfc6979(nonce32, msg32, key32, algo16, data, counter - 1);
 }
 
-static int nonce_function_test_retry(unsigned char *nonce32, const unsigned char *msg32, const unsigned char *key32, const unsigned char *algo16, const void *data, unsigned int counter) {
+static int nonce_function_test_retry(unsigned char *nonce32, const unsigned char *msg32, const unsigned char *key32, const unsigned char *algo16, void *data, unsigned int counter) {
    /* Dummy nonce generator that produces unacceptable nonces for the first several counter values. */
    if (counter < 3) {
        memset(nonce32, counter==0 ? 0 : 255, 32);

src/util.h

@@ -17,9 +17,13 @@
 
 typedef struct {
     void (*fn)(const char *text, void* data);
-    void* data;
+    const void* data;
 } callback_t;
 
+static SECP256K1_INLINE void secp256k1_callback(const callback_t * const cb, const char * const text) {
+    cb->fn(text, (void*)cb->data);
+}
+
 #ifdef DETERMINISTIC
 #define TEST_FAILURE(msg) do { \
     fprintf(stderr, "%s\n", msg); \
@@ -64,7 +68,7 @@ typedef struct {
 static SECP256K1_INLINE void *checked_malloc(const callback_t* cb, size_t size) {
     void *ret = malloc(size);
     if (ret == NULL) {
-        cb->fn("Out of memory", cb->data);
+        secp256k1_callback(cb, "Out of memory");
     }
     return ret;
 }