Use local secp256k1 callbacks in kotlin native code

These callbacks are only triggered either by arguments do not match explicit rquirements of the sepc256k1 library, or by hardware failures, memory corruption
or bug in secp256k1, and not by misuse of the library.
In theory we do not need to implement them, except to find bugs in our own code, but the default callbacks print a message to stderr and call abort() which
is not nice especially on mobile apps.

=> Here we introduce 2 specific exceptions, Secp256k1ErrorCallbackException and Secp256k1IllegalCallbackException, which are thrown when the error callback or illegal callback are called.

build.gradle.kts

@@ -22,7 +22,7 @@ buildscript {
 
 allprojects {
     group = "fr.acinq.secp256k1"
-    version = "0.11.0"
+    version = "0.12.0-SNAPSHOT"
 
     repositories {
         google()

jni/c/src/fr_acinq_secp256k1_Secp256k1CFunctions.c

@@ -17,34 +17,87 @@
 void JNI_ThrowByName(JNIEnv *penv, const char *name, const char *msg)
 {
   jclass cls = (*penv)->FindClass(penv, name);
-     if (cls != NULL) {
+  if (cls != NULL)
+  {
     (*penv)->ThrowNew(penv, cls, msg);
     (*penv)->DeleteLocalRef(penv, cls);
   }
 }
+/**
+ * secp256k1 uses callbacks for errors that are either hw pbs or bugs in the calling library, for example
+ * passing parameters with values that are explicitly defined as illegal in the API, and should never be called for normal operations
+ * But if they are, default behaviour is to print an error to stderr and abort which is not what we want especially in mobile apps
+ * => we set up string pointers in every method, and custom callback that will set them to the message passed in by sec256k1's callbacks, which
+ * we turn into specific Sec256k1 exceptions
+*/
+#define SETUP_ERROR_CALLBACKS                                                               \
+  char *error_callback_message = NULL;                                                      \
+  char *illegal_callback_message = NULL;                                                    \
+  secp256k1_context_set_error_callback(ctx, my_error_callback_fn, &error_callback_message); \
+  secp256k1_context_set_illegal_callback(ctx, my_illegal_callback_fn, &illegal_callback_message);
 
-#define CHECKRESULT(errorcheck, message) {                                        \
-    if (errorcheck) {                                                             \
+#define CHECKRESULT(errorcheck, message)                                                                       \
+  {                                                                                                            \
+    if (error_callback_message)                                                                                \
+    {                                                                                                          \
+      JNI_ThrowByName(penv, "fr/acinq/secp256k1/Secp256k1ErrorCallbackException", error_callback_message);     \
+      return 0;                                                                                                \
+    }                                                                                                          \
+    if (illegal_callback_message)                                                                              \
+    {                                                                                                          \
+      JNI_ThrowByName(penv, "fr/acinq/secp256k1/Secp256k1IllegalCallbackException", illegal_callback_message); \
+      return 0;                                                                                                \
+    }                                                                                                          \
+    if (errorcheck)                                                                                            \
+    {                                                                                                          \
       JNI_ThrowByName(penv, "fr/acinq/secp256k1/Secp256k1Exception", message);                                 \
       return 0;                                                                                                \
     }                                                                                                          \
   }
 
-#define CHECKRESULT1(errorcheck, message, dosomething) {                          \
-    if (errorcheck) {                                                             \
+#define CHECKRESULT1(errorcheck, message, dosomething)                                                         \
+  {                                                                                                            \
+    if (error_callback_message)                                                                                \
+    {                                                                                                          \
       dosomething;                                                                                             \
+      JNI_ThrowByName(penv, "fr/acinq/secp256k1/Secp256k1ErrorCallbackException", error_callback_message);     \
+      return 0;                                                                                                \
+    }                                                                                                          \
+    if (illegal_callback_message)                                                                              \
+    {                                                                                                          \
+      dosomething;                                                                                             \
+      JNI_ThrowByName(penv, "fr/acinq/secp256k1/Secp256k1IllegalCallbackException", illegal_callback_message); \
+      return 0;                                                                                                \
+    }                                                                                                          \
+    if (errorcheck)                                                                                            \
+    {                                                                                                          \
       JNI_ThrowByName(penv, "fr/acinq/secp256k1/Secp256k1Exception", message);                                 \
       return 0;                                                                                                \
     }                                                                                                          \
   }
 
+void my_illegal_callback_fn(const char *str, void *data)
+{
+  if (data != NULL)
+  {
+    *(char **)data = str;
+  }
+}
+
+void my_error_callback_fn(const char *str, void *data)
+{
+  if (data != NULL)
+  {
+    *(char **)data = str;
+  }
+}
+
 /*
  * Class:     fr_acinq_bitcoin_Secp256k1Bindings
  * Method:    secp256k1_context_create
  * Signature: (I)J
  */
-JNIEXPORT jlong JNICALL Java_fr_acinq_secp256k1_Secp256k1CFunctions_secp256k1_1context_1create
-  (JNIEnv *penv, jclass clazz, jint flags)
+JNIEXPORT jlong JNICALL Java_fr_acinq_secp256k1_Secp256k1CFunctions_secp256k1_1context_1create(JNIEnv *penv, jclass clazz, jint flags)
 {
   return (jlong)secp256k1_context_create(flags);
 }
@@ -54,10 +107,10 @@ JNIEXPORT jlong JNICALL Java_fr_acinq_secp256k1_Secp256k1CFunctions_secp256k1_1c
  * Method:    secp256k1_context_destroy
  * Signature: (J)V
  */
-JNIEXPORT void JNICALL Java_fr_acinq_secp256k1_Secp256k1CFunctions_secp256k1_1context_1destroy
-  (JNIEnv *penv, jclass clazz, jlong ctx)
+JNIEXPORT void JNICALL Java_fr_acinq_secp256k1_Secp256k1CFunctions_secp256k1_1context_1destroy(JNIEnv *penv, jclass clazz, jlong ctx)
+{
+  if (ctx != 0)
   {
-    if (ctx != 0) {
     secp256k1_context_destroy((secp256k1_context *)ctx);
   }
 }
@@ -67,16 +120,20 @@ JNIEXPORT void JNICALL Java_fr_acinq_secp256k1_Secp256k1CFunctions_secp256k1_1co
  * Method:    secp256k1_ec_seckey_verify
  * Signature: (J[B)I
  */
-JNIEXPORT jint JNICALL Java_fr_acinq_secp256k1_Secp256k1CFunctions_secp256k1_1ec_1seckey_1verify
-  (JNIEnv *penv, jclass clazz, jlong jctx, jbyteArray jseckey)
+JNIEXPORT jint JNICALL Java_fr_acinq_secp256k1_Secp256k1CFunctions_secp256k1_1ec_1seckey_1verify(JNIEnv *penv, jclass clazz, jlong jctx, jbyteArray jseckey)
 {
   secp256k1_context *ctx = (secp256k1_context *)jctx;
   jbyte *seckey;
   int result = 0;
 
-    if (jctx == 0) return 0;
-    if (jseckey == NULL) return 0;
-    if ((*penv)->GetArrayLength(penv, jseckey) != 32) return 0;
+  if (jctx == 0)
+    return 0;
+  if (jseckey == NULL)
+    return 0;
+  if ((*penv)->GetArrayLength(penv, jseckey) != 32)
+    return 0;
+
+  SETUP_ERROR_CALLBACKS
 
   seckey = (*penv)->GetByteArrayElements(penv, jseckey, 0);
   result = secp256k1_ec_seckey_verify(ctx, (unsigned char *)seckey);
@@ -89,8 +146,7 @@ JNIEXPORT jint JNICALL Java_fr_acinq_secp256k1_Secp256k1CFunctions_secp256k1_1ec
  * Method:    secp256k1_ec_pubkey_parse
  * Signature: (J[B)[B
  */
-JNIEXPORT jbyteArray JNICALL Java_fr_acinq_secp256k1_Secp256k1CFunctions_secp256k1_1ec_1pubkey_1parse
-  (JNIEnv *penv, jclass clazz, jlong jctx, jbyteArray jpubkey)
+JNIEXPORT jbyteArray JNICALL Java_fr_acinq_secp256k1_Secp256k1CFunctions_secp256k1_1ec_1pubkey_1parse(JNIEnv *penv, jclass clazz, jlong jctx, jbyteArray jpubkey)
 {
   secp256k1_context *ctx = (secp256k1_context *)jctx;
   jbyte *pubkeyBytes;
@@ -98,8 +154,12 @@ JNIEXPORT jbyteArray JNICALL Java_fr_acinq_secp256k1_Secp256k1CFunctions_secp256
   size_t size;
   int result = 0;
 
-    if (jctx == 0) return 0;
-    if (jpubkey == NULL) return 0;
+  if (jctx == 0)
+    return 0;
+  if (jpubkey == NULL)
+    return 0;
+
+  SETUP_ERROR_CALLBACKS
 
   size = (*penv)->GetArrayLength(penv, jpubkey);
   CHECKRESULT((size != 33) && (size != 65), "invalid public key size");
@@ -123,8 +183,7 @@ JNIEXPORT jbyteArray JNICALL Java_fr_acinq_secp256k1_Secp256k1CFunctions_secp256
  * Method:    secp256k1_ec_pubkey_create
  * Signature: (J[B)[B
  */
-JNIEXPORT jbyteArray JNICALL Java_fr_acinq_secp256k1_Secp256k1CFunctions_secp256k1_1ec_1pubkey_1create
-  (JNIEnv *penv, jclass clazz, jlong jctx, jbyteArray jseckey)
+JNIEXPORT jbyteArray JNICALL Java_fr_acinq_secp256k1_Secp256k1CFunctions_secp256k1_1ec_1pubkey_1create(JNIEnv *penv, jclass clazz, jlong jctx, jbyteArray jseckey)
 {
   secp256k1_context *ctx = (secp256k1_context *)jctx;
   jbyte *seckey, *pubkey;
@@ -133,8 +192,12 @@ JNIEXPORT jbyteArray JNICALL Java_fr_acinq_secp256k1_Secp256k1CFunctions_secp256
   size_t len;
   jbyteArray jpubkey = 0;
 
-    if (jseckey == NULL) return NULL;
-    if (jctx == 0) return NULL;
+  if (jseckey == NULL)
+    return NULL;
+  if (jctx == 0)
+    return NULL;
+
+  SETUP_ERROR_CALLBACKS
 
   CHECKRESULT((*penv)->GetArrayLength(penv, jseckey) != 32, "secret key must be 32 bytes");
   seckey = (*penv)->GetByteArrayElements(penv, jseckey, 0);
@@ -155,8 +218,7 @@ JNIEXPORT jbyteArray JNICALL Java_fr_acinq_secp256k1_Secp256k1CFunctions_secp256
  * Method:    secp256k1_ecdsa_sign
  * Signature: (J[B[B)[B
  */
-JNIEXPORT jbyteArray JNICALL Java_fr_acinq_secp256k1_Secp256k1CFunctions_secp256k1_1ecdsa_1sign
-  (JNIEnv *penv, jclass clazz, jlong jctx, jbyteArray jmsg, jbyteArray jseckey)
+JNIEXPORT jbyteArray JNICALL Java_fr_acinq_secp256k1_Secp256k1CFunctions_secp256k1_1ecdsa_1sign(JNIEnv *penv, jclass clazz, jlong jctx, jbyteArray jmsg, jbyteArray jseckey)
 {
   secp256k1_context *ctx = (secp256k1_context *)jctx;
   jbyte *seckey, *msg, *sig;
@@ -164,9 +226,14 @@ JNIEXPORT jbyteArray JNICALL Java_fr_acinq_secp256k1_Secp256k1CFunctions_secp256
   int result = 0;
   jbyteArray jsig;
 
-    if (jctx == 0) return NULL;
-    if (jmsg == NULL) return NULL;
-    if (jseckey == NULL) return NULL;
+  if (jctx == 0)
+    return NULL;
+  if (jmsg == NULL)
+    return NULL;
+  if (jseckey == NULL)
+    return NULL;
+
+  SETUP_ERROR_CALLBACKS
 
   CHECKRESULT((*penv)->GetArrayLength(penv, jseckey) != 32, "secret key must be 32 bytes");
   CHECKRESULT((*penv)->GetArrayLength(penv, jmsg) != 32, "message key must be 32 bytes");
@@ -188,8 +255,10 @@ JNIEXPORT jbyteArray JNICALL Java_fr_acinq_secp256k1_Secp256k1CFunctions_secp256
 
 int GetSignatureFormat(size_t size)
 {
-    if (size == 64) return SIG_FORMAT_COMPACT;
-    if (size < 64) return SIG_FORMAT_UNKNOWN;
+  if (size == 64)
+    return SIG_FORMAT_COMPACT;
+  if (size < 64)
+    return SIG_FORMAT_UNKNOWN;
   return SIG_FORMAT_DER;
 }
 
@@ -198,8 +267,7 @@ int GetSignatureFormat(size_t size)
  * Method:    secp256k1_ecdsa_verify
  * Signature: (J[B[B[B)I
  */
-JNIEXPORT jint JNICALL Java_fr_acinq_secp256k1_Secp256k1CFunctions_secp256k1_1ecdsa_1verify
-  (JNIEnv *penv, jclass clazz, jlong jctx, jbyteArray jsig, jbyteArray jmsg, jbyteArray jpubkey)
+JNIEXPORT jint JNICALL Java_fr_acinq_secp256k1_Secp256k1CFunctions_secp256k1_1ecdsa_1verify(JNIEnv *penv, jclass clazz, jlong jctx, jbyteArray jsig, jbyteArray jmsg, jbyteArray jpubkey)
 {
   secp256k1_context *ctx = (secp256k1_context *)jctx;
   jbyte *pub, *msg, *sig;
@@ -208,10 +276,16 @@ JNIEXPORT jint JNICALL Java_fr_acinq_secp256k1_Secp256k1CFunctions_secp256k1_1ec
   size_t sigSize, pubSize;
   int result = 0;
 
-    if (jctx == 0) return 0;
-    if (jsig == NULL) return 0;
-    if (jmsg == NULL) return 0;
-    if (jpubkey == NULL) return 0;
+  if (jctx == 0)
+    return 0;
+  if (jsig == NULL)
+    return 0;
+  if (jmsg == NULL)
+    return 0;
+  if (jpubkey == NULL)
+    return 0;
+
+  SETUP_ERROR_CALLBACKS
 
   sigSize = (*penv)->GetArrayLength(penv, jsig);
   int sigFormat = GetSignatureFormat(sigSize);
@@ -223,7 +297,8 @@ JNIEXPORT jint JNICALL Java_fr_acinq_secp256k1_Secp256k1CFunctions_secp256k1_1ec
   CHECKRESULT((*penv)->GetArrayLength(penv, jmsg) != 32, "message must be 32 bytes");
 
   sig = (*penv)->GetByteArrayElements(penv, jsig, 0);
-    switch(sigFormat) {
+  switch (sigFormat)
+  {
   case SIG_FORMAT_COMPACT:
     result = secp256k1_ecdsa_signature_parse_compact(ctx, &signature, (unsigned char *)sig);
     (*penv)->ReleaseByteArrayElements(penv, jsig, sig, 0);
@@ -252,8 +327,7 @@ JNIEXPORT jint JNICALL Java_fr_acinq_secp256k1_Secp256k1CFunctions_secp256k1_1ec
  * Method:    secp256k1_ecdsa_signature_normalize
  * Signature: (J[B[B)I
  */
-JNIEXPORT jint JNICALL Java_fr_acinq_secp256k1_Secp256k1CFunctions_secp256k1_1ecdsa_1signature_1normalize
-  (JNIEnv *penv, jclass clazz, jlong jctx, jbyteArray jsigin, jbyteArray jsigout)
+JNIEXPORT jint JNICALL Java_fr_acinq_secp256k1_Secp256k1CFunctions_secp256k1_1ecdsa_1signature_1normalize(JNIEnv *penv, jclass clazz, jlong jctx, jbyteArray jsigin, jbyteArray jsigout)
 {
   secp256k1_context *ctx = (secp256k1_context *)jctx;
   jbyte *sig;
@@ -263,9 +337,14 @@ JNIEXPORT jint JNICALL Java_fr_acinq_secp256k1_Secp256k1CFunctions_secp256k1_1ec
   int return_value = 0;
   int sigFormat = SIG_FORMAT_UNKNOWN;
 
-    if (jctx == 0) return 0;
-    if (jsigin == NULL) return 0;
-    if (jsigout == NULL) return 0;
+  if (jctx == 0)
+    return 0;
+  if (jsigin == NULL)
+    return 0;
+  if (jsigout == NULL)
+    return 0;
+
+  SETUP_ERROR_CALLBACKS
 
   size = (*penv)->GetArrayLength(penv, jsigin);
   sigFormat = GetSignatureFormat(size);
@@ -273,7 +352,8 @@ JNIEXPORT jint JNICALL Java_fr_acinq_secp256k1_Secp256k1CFunctions_secp256k1_1ec
   CHECKRESULT((*penv)->GetArrayLength(penv, jsigout) != 64, "output signature length must be 64 bytes");
 
   sig = (*penv)->GetByteArrayElements(penv, jsigin, 0);
-    switch(sigFormat) {
+  switch (sigFormat)
+  {
   case SIG_FORMAT_COMPACT:
     result = secp256k1_ecdsa_signature_parse_compact(ctx, &signature_in, (unsigned char *)sig);
     (*penv)->ReleaseByteArrayElements(penv, jsigin, sig, 0);
@@ -299,15 +379,19 @@ JNIEXPORT jint JNICALL Java_fr_acinq_secp256k1_Secp256k1CFunctions_secp256k1_1ec
  * Method:    secp256k1_ec_privkey_negate
  * Signature: (J[B)[B
  */
-JNIEXPORT jbyteArray JNICALL Java_fr_acinq_secp256k1_Secp256k1CFunctions_secp256k1_1ec_1privkey_1negate
-  (JNIEnv *penv, jclass clazz, jlong jctx, jbyteArray jseckey)
+JNIEXPORT jbyteArray JNICALL Java_fr_acinq_secp256k1_Secp256k1CFunctions_secp256k1_1ec_1privkey_1negate(JNIEnv *penv, jclass clazz, jlong jctx, jbyteArray jseckey)
 {
   secp256k1_context *ctx = (secp256k1_context *)jctx;
   jbyte *seckey;
   int result = 0;
 
-    if (jctx == 0) return 0;
-    if (jseckey == NULL) return 0;
+  if (jctx == 0)
+    return 0;
+  if (jseckey == NULL)
+    return 0;
+
+  SETUP_ERROR_CALLBACKS
+
   CHECKRESULT((*penv)->GetArrayLength(penv, jseckey) != 32, "secret key must be 32 bytes");
   seckey = (*penv)->GetByteArrayElements(penv, jseckey, 0);
   result = secp256k1_ec_seckey_negate(ctx, (unsigned char *)seckey);
@@ -321,8 +405,7 @@ JNIEXPORT jbyteArray JNICALL Java_fr_acinq_secp256k1_Secp256k1CFunctions_secp256
  * Method:    secp256k1_ec_pubkey_negate
  * Signature: (J[B)[B
  */
-JNIEXPORT jbyteArray JNICALL Java_fr_acinq_secp256k1_Secp256k1CFunctions_secp256k1_1ec_1pubkey_1negate
-  (JNIEnv *penv, jclass clazz, jlong jctx, jbyteArray jpubkey)
+JNIEXPORT jbyteArray JNICALL Java_fr_acinq_secp256k1_Secp256k1CFunctions_secp256k1_1ec_1pubkey_1negate(JNIEnv *penv, jclass clazz, jlong jctx, jbyteArray jpubkey)
 {
   secp256k1_context *ctx = (secp256k1_context *)jctx;
   jbyte *pub;
@@ -330,8 +413,12 @@ JNIEXPORT jbyteArray JNICALL Java_fr_acinq_secp256k1_Secp256k1CFunctions_secp256
   size_t size;
   int result = 0;
 
-    if (jctx == 0) return 0;
-    if (jpubkey == NULL) return 0;
+  if (jctx == 0)
+    return 0;
+  if (jpubkey == NULL)
+    return 0;
+
+  SETUP_ERROR_CALLBACKS
 
   size = (*penv)->GetArrayLength(penv, jpubkey);
   CHECKRESULT((size != 33) && (size != 65), "invalid public key size");
@@ -357,16 +444,20 @@ JNIEXPORT jbyteArray JNICALL Java_fr_acinq_secp256k1_Secp256k1CFunctions_secp256
  * Method:    secp256k1_ec_privkey_tweak_add
  * Signature: (J[B[B)[B
  */
-JNIEXPORT jbyteArray JNICALL Java_fr_acinq_secp256k1_Secp256k1CFunctions_secp256k1_1ec_1privkey_1tweak_1add
-  (JNIEnv *penv, jclass clazz, jlong jctx, jbyteArray jseckey, jbyteArray jtweak)
+JNIEXPORT jbyteArray JNICALL Java_fr_acinq_secp256k1_Secp256k1CFunctions_secp256k1_1ec_1privkey_1tweak_1add(JNIEnv *penv, jclass clazz, jlong jctx, jbyteArray jseckey, jbyteArray jtweak)
 {
   secp256k1_context *ctx = (secp256k1_context *)jctx;
   jbyte *seckey, *tweak;
   int result = 0;
 
-    if (jctx == 0) return NULL;
-    if (jseckey == NULL) return NULL;
-    if (jtweak == NULL) return NULL;
+  if (jctx == 0)
+    return NULL;
+  if (jseckey == NULL)
+    return NULL;
+  if (jtweak == NULL)
+    return NULL;
+
+  SETUP_ERROR_CALLBACKS
 
   CHECKRESULT((*penv)->GetArrayLength(penv, jseckey) != 32, "secret key must be 32 bytes");
   CHECKRESULT((*penv)->GetArrayLength(penv, jtweak) != 32, "tweak must be 32 bytes");
@@ -384,8 +475,7 @@ JNIEXPORT jbyteArray JNICALL Java_fr_acinq_secp256k1_Secp256k1CFunctions_secp256
  * Method:    secp256k1_ec_pubkey_tweak_add
  * Signature: (J[B[B)[B
  */
-JNIEXPORT jbyteArray JNICALL Java_fr_acinq_secp256k1_Secp256k1CFunctions_secp256k1_1ec_1pubkey_1tweak_1add
-  (JNIEnv *penv, jclass clazz, jlong jctx, jbyteArray jpubkey, jbyteArray jtweak)
+JNIEXPORT jbyteArray JNICALL Java_fr_acinq_secp256k1_Secp256k1CFunctions_secp256k1_1ec_1pubkey_1tweak_1add(JNIEnv *penv, jclass clazz, jlong jctx, jbyteArray jpubkey, jbyteArray jtweak)
 {
   secp256k1_context *ctx = (secp256k1_context *)jctx;
   jbyte *pub, *tweak;
@@ -393,9 +483,14 @@ JNIEXPORT jbyteArray JNICALL Java_fr_acinq_secp256k1_Secp256k1CFunctions_secp256
   size_t size;
   int result = 0;
 
-    if (jctx == 0) return NULL;
-    if (jpubkey == NULL) return NULL;
-    if (jtweak == NULL) return NULL;
+  if (jctx == 0)
+    return NULL;
+  if (jpubkey == NULL)
+    return NULL;
+  if (jtweak == NULL)
+    return NULL;
+
+  SETUP_ERROR_CALLBACKS
 
   size = (*penv)->GetArrayLength(penv, jpubkey);
   CHECKRESULT((size != 33) && (size != 65), "invalid public key size");
@@ -425,16 +520,20 @@ JNIEXPORT jbyteArray JNICALL Java_fr_acinq_secp256k1_Secp256k1CFunctions_secp256
  * Method:    secp256k1_ec_privkey_tweak_mul
  * Signature: (J[B[B)[B
  */
-JNIEXPORT jbyteArray JNICALL Java_fr_acinq_secp256k1_Secp256k1CFunctions_secp256k1_1ec_1privkey_1tweak_1mul
-  (JNIEnv *penv, jclass clazz, jlong jctx, jbyteArray jseckey, jbyteArray jtweak)
+JNIEXPORT jbyteArray JNICALL Java_fr_acinq_secp256k1_Secp256k1CFunctions_secp256k1_1ec_1privkey_1tweak_1mul(JNIEnv *penv, jclass clazz, jlong jctx, jbyteArray jseckey, jbyteArray jtweak)
 {
   secp256k1_context *ctx = (secp256k1_context *)jctx;
   jbyte *seckey, *tweak;
   int result = 0;
 
-    if (jctx == 0) return NULL;
-    if (jseckey == NULL) return NULL;
-    if (jtweak == NULL) return NULL;
+  if (jctx == 0)
+    return NULL;
+  if (jseckey == NULL)
+    return NULL;
+  if (jtweak == NULL)
+    return NULL;
+
+  SETUP_ERROR_CALLBACKS
 
   CHECKRESULT((*penv)->GetArrayLength(penv, jseckey) != 32, "secret key must be 32 bytes");
   CHECKRESULT((*penv)->GetArrayLength(penv, jtweak) != 32, "tweak must be 32 bytes");
@@ -452,8 +551,7 @@ JNIEXPORT jbyteArray JNICALL Java_fr_acinq_secp256k1_Secp256k1CFunctions_secp256
  * Method:    secp256k1_ec_pubkey_tweak_mul
  * Signature: (J[B[B)[B
  */
-JNIEXPORT jbyteArray JNICALL Java_fr_acinq_secp256k1_Secp256k1CFunctions_secp256k1_1ec_1pubkey_1tweak_1mul
-  (JNIEnv *penv, jclass clazz, jlong jctx, jbyteArray jpubkey, jbyteArray jtweak)
+JNIEXPORT jbyteArray JNICALL Java_fr_acinq_secp256k1_Secp256k1CFunctions_secp256k1_1ec_1pubkey_1tweak_1mul(JNIEnv *penv, jclass clazz, jlong jctx, jbyteArray jpubkey, jbyteArray jtweak)
 {
   secp256k1_context *ctx = (secp256k1_context *)jctx;
   jbyte *pub, *tweak;
@@ -461,9 +559,14 @@ JNIEXPORT jbyteArray JNICALL Java_fr_acinq_secp256k1_Secp256k1CFunctions_secp256
   size_t size;
   int result = 0;
 
-    if (jctx == 0) return NULL;
-    if (jpubkey == NULL) return NULL;
-    if (jtweak == NULL) return NULL;
+  if (jctx == 0)
+    return NULL;
+  if (jpubkey == NULL)
+    return NULL;
+  if (jtweak == NULL)
+    return NULL;
+
+  SETUP_ERROR_CALLBACKS
 
   size = (*penv)->GetArrayLength(penv, jpubkey);
   CHECKRESULT((size != 33) && (size != 65), "invalid public key size");
@@ -490,8 +593,10 @@ JNIEXPORT jbyteArray JNICALL Java_fr_acinq_secp256k1_Secp256k1CFunctions_secp256
 void free_pubkeys(secp256k1_pubkey **pubkeys, size_t count)
 {
   size_t i;
-    for(i = 0; i < count; i++) {
-        if (pubkeys[i] != NULL) free(pubkeys[i]);
+  for (i = 0; i < count; i++)
+  {
+    if (pubkeys[i] != NULL)
+      free(pubkeys[i]);
   }
   free(pubkeys);
 }
@@ -501,8 +606,7 @@ void free_pubkeys(secp256k1_pubkey **pubkeys, size_t count)
  * Method:    secp256k1_ec_pubkey_combine
  * Signature: (J[[B)[B
  */
-JNIEXPORT jbyteArray JNICALL Java_fr_acinq_secp256k1_Secp256k1CFunctions_secp256k1_1ec_1pubkey_1combine
-  (JNIEnv *penv, jclass clazz, jlong jctx, jobjectArray jpubkeys)
+JNIEXPORT jbyteArray JNICALL Java_fr_acinq_secp256k1_Secp256k1CFunctions_secp256k1_1ec_1pubkey_1combine(JNIEnv *penv, jclass clazz, jlong jctx, jobjectArray jpubkeys)
 {
   secp256k1_context *ctx = (secp256k1_context *)jctx;
   jbyte *pub;
@@ -513,13 +617,18 @@ JNIEXPORT jbyteArray JNICALL Java_fr_acinq_secp256k1_Secp256k1CFunctions_secp256
   size_t i;
   int result = 0;
 
-    if (jctx == 0) return NULL;
-    if (jpubkeys == NULL) return NULL;
+  if (jctx == 0)
+    return NULL;
+  if (jpubkeys == NULL)
+    return NULL;
+
+  SETUP_ERROR_CALLBACKS
 
   count = (*penv)->GetArrayLength(penv, jpubkeys);
   pubkeys = calloc(count, sizeof(secp256k1_pubkey *));
 
-    for(i = 0; i < count; i++) {
+  for (i = 0; i < count; i++)
+  {
     pubkeys[i] = calloc(1, sizeof(secp256k1_pubkey));
     jpubkey = (jbyteArray)(*penv)->GetObjectArrayElement(penv, jpubkeys, i);
     size = (*penv)->GetArrayLength(penv, jpubkey);
@@ -547,8 +656,7 @@ JNIEXPORT jbyteArray JNICALL Java_fr_acinq_secp256k1_Secp256k1CFunctions_secp256
  * Method:    secp256k1_ecdh
  * Signature: (J[B[B)[B
  */
-JNIEXPORT jbyteArray JNICALL Java_fr_acinq_secp256k1_Secp256k1CFunctions_secp256k1_1ecdh
-  (JNIEnv *penv, jclass clazz, jlong jctx, jbyteArray jseckey, jbyteArray jpubkey)
+JNIEXPORT jbyteArray JNICALL Java_fr_acinq_secp256k1_Secp256k1CFunctions_secp256k1_1ecdh(JNIEnv *penv, jclass clazz, jlong jctx, jbyteArray jseckey, jbyteArray jpubkey)
 {
   secp256k1_context *ctx = (secp256k1_context *)jctx;
   jbyte *seckeyBytes, *pubkeyBytes, *output;
@@ -557,9 +665,14 @@ JNIEXPORT jbyteArray JNICALL Java_fr_acinq_secp256k1_Secp256k1CFunctions_secp256
   size_t size;
   int result;
 
-    if (jctx == 0) return NULL;
-    if (jseckey == NULL) return NULL;
-    if (jpubkey == NULL) return NULL;
+  if (jctx == 0)
+    return NULL;
+  if (jseckey == NULL)
+    return NULL;
+  if (jpubkey == NULL)
+    return NULL;
+
+  SETUP_ERROR_CALLBACKS
 
   CHECKRESULT((*penv)->GetArrayLength(penv, jseckey) != 32, "invalid private key size");
 
@@ -584,8 +697,7 @@ JNIEXPORT jbyteArray JNICALL Java_fr_acinq_secp256k1_Secp256k1CFunctions_secp256
  * Method:    secp256k1_ecdsa_recover
  * Signature: (J[B[BI)[B
  */
-JNIEXPORT jbyteArray JNICALL Java_fr_acinq_secp256k1_Secp256k1CFunctions_secp256k1_1ecdsa_1recover
-  (JNIEnv *penv, jclass clazz, jlong jctx, jbyteArray jsig, jbyteArray jmsg, jint recid)
+JNIEXPORT jbyteArray JNICALL Java_fr_acinq_secp256k1_Secp256k1CFunctions_secp256k1_1ecdsa_1recover(JNIEnv *penv, jclass clazz, jlong jctx, jbyteArray jsig, jbyteArray jmsg, jint recid)
 {
   secp256k1_context *ctx = (secp256k1_context *)jctx;
   jbyte *sig, *msg, *pub;
@@ -597,16 +709,25 @@ JNIEXPORT jbyteArray JNICALL Java_fr_acinq_secp256k1_Secp256k1CFunctions_secp256
   size_t sigSize, size;
   int result;
 
-    if (jctx == 0) return NULL;
-    if (jsig == NULL) return NULL;
-    if (jmsg == NULL) return NULL;
+  if (jctx == 0)
+    return NULL;
+  if (jsig == NULL)
+    return NULL;
+  if (jmsg == NULL)
+    return NULL;
+
+  SETUP_ERROR_CALLBACKS
+
+  // we do not check that recid is valid, which should trigger our illegal callback handler to throw a Secp256k1IllegalCallbackException
+  // CHECKRESULT(recid < 0 || recid > 3, "recid must be 0, 1, 2 or 3")
 
   sigSize = (*penv)->GetArrayLength(penv, jsig);
   int sigFormat = GetSignatureFormat(sigSize);
   CHECKRESULT(sigFormat == SIG_FORMAT_UNKNOWN, "invalid signature size");
   CHECKRESULT((*penv)->GetArrayLength(penv, jmsg) != 32, "message must be 32 bytes");
   sig = (*penv)->GetByteArrayElements(penv, jsig, 0);
-    switch(sigFormat) {
+  switch (sigFormat)
+  {
   case SIG_FORMAT_COMPACT:
     result = secp256k1_ecdsa_recoverable_signature_parse_compact(ctx, &signature, (unsigned char *)sig, recid);
     (*penv)->ReleaseByteArrayElements(penv, jsig, sig, 0);
@@ -641,18 +762,22 @@ JNIEXPORT jbyteArray JNICALL Java_fr_acinq_secp256k1_Secp256k1CFunctions_secp256
  * Method:    secp256k1_compact_to_der
  * Signature: (J[B)[B
  */
-JNIEXPORT jbyteArray JNICALL Java_fr_acinq_secp256k1_Secp256k1CFunctions_secp256k1_1compact_1to_1der
-  (JNIEnv *penv, jclass clazz, jlong jctx, jbyteArray jsig)
+JNIEXPORT jbyteArray JNICALL Java_fr_acinq_secp256k1_Secp256k1CFunctions_secp256k1_1compact_1to_1der(JNIEnv *penv, jclass clazz, jlong jctx, jbyteArray jsig)
 {
   secp256k1_context *ctx = (secp256k1_context *)jctx;
   jbyte *sig;
-    secp256k1_ecdsa_signature signature;;
+  secp256k1_ecdsa_signature signature;
   unsigned char der[73];
   size_t size;
   int result = 0;
 
-    if (jctx == 0) return 0;
-    if (jsig == NULL) return 0;
+  if (jctx == 0)
+    return 0;
+  if (jsig == NULL)
+    return 0;
+
+  SETUP_ERROR_CALLBACKS
+
   CHECKRESULT((*penv)->GetArrayLength(penv, jsig) != 64, "invalid signature size");
 
   size = (*penv)->GetArrayLength(penv, jsig);
@@ -676,8 +801,7 @@ JNIEXPORT jbyteArray JNICALL Java_fr_acinq_secp256k1_Secp256k1CFunctions_secp256
  * Method:    secp256k1_schnorrsig_sign
  * Signature: (J[B[B[B)[B
  */
-JNIEXPORT jbyteArray JNICALL Java_fr_acinq_secp256k1_Secp256k1CFunctions_secp256k1_1schnorrsig_1sign
-  (JNIEnv *penv, jclass clazz, jlong jctx, jbyteArray jmsg, jbyteArray jseckey, jbyteArray jauxrand32)
+JNIEXPORT jbyteArray JNICALL Java_fr_acinq_secp256k1_Secp256k1CFunctions_secp256k1_1schnorrsig_1sign(JNIEnv *penv, jclass clazz, jlong jctx, jbyteArray jmsg, jbyteArray jseckey, jbyteArray jauxrand32)
 {
   secp256k1_context *ctx = (secp256k1_context *)jctx;
   jbyte *seckey, *msg, *sig, *auxrand32 = NULL;
@@ -686,13 +810,19 @@ JNIEXPORT jbyteArray JNICALL Java_fr_acinq_secp256k1_Secp256k1CFunctions_secp256
   int result = 0;
   jbyteArray jsig;
 
-    if (jctx == 0) return NULL;
-    if (jmsg == NULL) return NULL;
-    if (jseckey == NULL) return NULL;
+  if (jctx == 0)
+    return NULL;
+  if (jmsg == NULL)
+    return NULL;
+  if (jseckey == NULL)
+    return NULL;
+
+  SETUP_ERROR_CALLBACKS
 
   CHECKRESULT((*penv)->GetArrayLength(penv, jseckey) != 32, "secret key must be 32 bytes");
   CHECKRESULT((*penv)->GetArrayLength(penv, jmsg) != 32, "message must be 32 bytes");
-    if (jauxrand32 != 0) {
+  if (jauxrand32 != 0)
+  {
     CHECKRESULT((*penv)->GetArrayLength(penv, jauxrand32) != 32, "auxiliary random data must be 32 bytes");
   }
   seckey = (*penv)->GetByteArrayElements(penv, jseckey, 0);
@@ -701,13 +831,15 @@ JNIEXPORT jbyteArray JNICALL Java_fr_acinq_secp256k1_Secp256k1CFunctions_secp256
   CHECKRESULT(!result, "secp256k1_keypair_create failed");
 
   msg = (*penv)->GetByteArrayElements(penv, jmsg, 0);
-    if (jauxrand32 != 0) {
+  if (jauxrand32 != 0)
+  {
     auxrand32 = (*penv)->GetByteArrayElements(penv, jauxrand32, 0);
   }
 
   result = secp256k1_schnorrsig_sign32(ctx, signature, (unsigned char *)msg, &keypair, auxrand32);
   (*penv)->ReleaseByteArrayElements(penv, jmsg, msg, 0);
-    if (auxrand32 != 0) {
+  if (auxrand32 != 0)
+  {
     (*penv)->ReleaseByteArrayElements(penv, jauxrand32, auxrand32, 0);
   }
   CHECKRESULT(!result, "secp256k1_schnorrsig_sign failed");
@@ -724,18 +856,23 @@ JNIEXPORT jbyteArray JNICALL Java_fr_acinq_secp256k1_Secp256k1CFunctions_secp256
  * Method:    secp256k1_schnorrsig_verify
  * Signature: (J[B[B[B)I
  */
-JNIEXPORT jint JNICALL Java_fr_acinq_secp256k1_Secp256k1CFunctions_secp256k1_1schnorrsig_1verify
-  (JNIEnv *penv, jclass clazz, jlong jctx, jbyteArray jsig, jbyteArray jmsg, jbyteArray jpubkey)
+JNIEXPORT jint JNICALL Java_fr_acinq_secp256k1_Secp256k1CFunctions_secp256k1_1schnorrsig_1verify(JNIEnv *penv, jclass clazz, jlong jctx, jbyteArray jsig, jbyteArray jmsg, jbyteArray jpubkey)
 {
   secp256k1_context *ctx = (secp256k1_context *)jctx;
   jbyte *pub, *msg, *sig;
   secp256k1_xonly_pubkey pubkey;
   int result = 0;
 
-    if (jctx == 0) return 0;
-    if (jsig == NULL) return 0;
-    if (jmsg == NULL) return 0;
-    if (jpubkey == NULL) return 0;
+  if (jctx == 0)
+    return 0;
+  if (jsig == NULL)
+    return 0;
+  if (jmsg == NULL)
+    return 0;
+  if (jpubkey == NULL)
+    return 0;
+
+  SETUP_ERROR_CALLBACKS
 
   CHECKRESULT((*penv)->GetArrayLength(penv, jsig) != 64, "signature must be 64 bytes");
   CHECKRESULT((*penv)->GetArrayLength(penv, jpubkey) != 32, "public key must be 32 bytes");

src/commonMain/kotlin/fr/acinq/secp256k1/Secp256k1.kt

@@ -166,7 +166,17 @@ public interface Secp256k1 {
 
 internal expect fun getSecpk256k1(): Secp256k1
 
-public class Secp256k1Exception : RuntimeException {
+public open class Secp256k1Exception : RuntimeException {
+    public constructor() : super()
+    public constructor(message: String?) : super(message)
+}
+
+public class Secp256k1ErrorCallbackException : Secp256k1Exception {
+    public constructor() : super()
+    public constructor(message: String?) : super(message)
+}
+
+public class Secp256k1IllegalCallbackException : Secp256k1Exception {
     public constructor() : super()
     public constructor(message: String?) : super(message)
 }

src/nativeMain/kotlin/fr/acinq/secp256k1/Secp256k1Native.kt

@@ -4,15 +4,67 @@ import kotlinx.cinterop.*
 import platform.posix.size_tVar
 import secp256k1.*
 
-@OptIn(ExperimentalUnsignedTypes::class)
+private typealias Secp256k1CallbackHandler = (String) -> Unit
+
+@OptIn(ExperimentalStdlibApi::class)
+private class CallbackHandler(ctx: CPointer<secp256k1_context>) : AutoCloseable {
+    var illegalCallBackMessage: String? = null
+    val illegalHandler: Secp256k1CallbackHandler = { x: String -> illegalCallBackMessage = x }
+    val illegalCallbackRef = StableRef.create(illegalHandler)
+    var errorCallBackMessage: String? = null
+    val errorHandler: Secp256k1CallbackHandler = { x: String -> errorCallBackMessage = x }
+    val errorCallbackRef = StableRef.create(errorHandler)
+
+    init {
+        secp256k1_context_set_error_callback(
+            ctx, staticCFunction { buffer: CPointer<ByteVar>?, data: COpaquePointer? ->
+                if (data != null) {
+                    val callback = data.asStableRef<Secp256k1CallbackHandler>().get()
+                    callback(buffer?.toKString() ?: "error callback triggered")
+                }
+            },
+            errorCallbackRef.asCPointer()
+        )
+        secp256k1_context_set_illegal_callback(
+            ctx, staticCFunction { buffer: CPointer<ByteVar>?, data: COpaquePointer? ->
+                if (data != null) {
+                    val callback = data.asStableRef<Secp256k1CallbackHandler>().get()
+                    callback(buffer?.toKString() ?: "illegal callback triggered")
+                }
+            },
+            illegalCallbackRef.asCPointer()
+        )
+    }
+
+    fun checkForErrors() {
+        errorCallBackMessage?.let { throw Secp256k1ErrorCallbackException(it) }
+        illegalCallBackMessage?.let { throw Secp256k1IllegalCallbackException(it) }
+    }
+
+    override fun close() {
+        // StableRef instances have to be disposed of manually
+        illegalCallbackRef.dispose()
+        errorCallbackRef.dispose()
+    }
+}
+
+@OptIn(ExperimentalUnsignedTypes::class, ExperimentalStdlibApi::class)
 public object Secp256k1Native : Secp256k1 {
 
     private val ctx: CPointer<secp256k1_context> by lazy {
+
         secp256k1_context_create((SECP256K1_FLAGS_TYPE_CONTEXT or SECP256K1_FLAGS_BIT_CONTEXT_SIGN or SECP256K1_FLAGS_BIT_CONTEXT_VERIFY).toUInt())
             ?: error("Could not create secp256k1 context")
     }
 
-    private fun Int.requireSuccess(message: String): Int = if (this != 1) throw Secp256k1Exception(message) else this
+    private fun Int.requireSuccess(message: String): Int {
+        return if (this != 1) throw Secp256k1Exception(message) else this
+    }
+
+    private fun Int.requireSuccess(callbackHandler: CallbackHandler, message: String): Int {
+        callbackHandler.checkForErrors()
+        return if (this != 1) throw Secp256k1Exception(message) else this
+    }
 
     private fun MemScope.allocSignature(input: ByteArray): secp256k1_ecdsa_signature {
         val sig = alloc<secp256k1_ecdsa_signature>()
@@ -58,181 +110,225 @@ public object Secp256k1Native : Secp256k1 {
     public override fun verify(signature: ByteArray, message: ByteArray, pubkey: ByteArray): Boolean {
         require(message.size == 32)
         require(pubkey.size == 33 || pubkey.size == 65)
+        CallbackHandler(ctx).use { callbackHandler ->
             memScoped {
                 val nPubkey = allocPublicKey(pubkey)
                 val nMessage = toNat(message)
                 val nSig = allocSignature(signature)
-            return secp256k1_ecdsa_verify(ctx, nSig.ptr, nMessage, nPubkey.ptr) == 1
+                val verify = secp256k1_ecdsa_verify(ctx, nSig.ptr, nMessage, nPubkey.ptr)
+                callbackHandler.checkForErrors()
+                return verify == 1
+            }
         }
     }
 
     public override fun sign(message: ByteArray, privkey: ByteArray): ByteArray {
         require(privkey.size == 32)
         require(message.size == 32)
+        CallbackHandler(ctx).use { callbackHandler ->
             memScoped {
                 val nPrivkey = toNat(privkey)
                 val nMessage = toNat(message)
                 val nSig = alloc<secp256k1_ecdsa_signature>()
-            secp256k1_ecdsa_sign(ctx, nSig.ptr, nMessage, nPrivkey, null, null).requireSuccess("secp256k1_ecdsa_sign() failed")
+                secp256k1_ecdsa_sign(ctx, nSig.ptr, nMessage, nPrivkey, null, null).requireSuccess(callbackHandler, "secp256k1_ecdsa_sign() failed")
                 return serializeSignature(nSig)
             }
         }
+    }
 
     public override fun signatureNormalize(sig: ByteArray): Pair<ByteArray, Boolean> {
         require(sig.size >= 64) { "invalid signature ${Hex.encode(sig)}" }
+        CallbackHandler(ctx).use { callbackHandler ->
             memScoped {
                 val nSig = allocSignature(sig)
                 val isHighS = secp256k1_ecdsa_signature_normalize(ctx, nSig.ptr, nSig.ptr)
+                callbackHandler.checkForErrors()
                 return Pair(serializeSignature(nSig), isHighS == 1)
             }
         }
+    }
 
     public override fun secKeyVerify(privkey: ByteArray): Boolean {
         if (privkey.size != 32) return false
+        CallbackHandler(ctx).use { callbackHandler ->
             memScoped {
                 val nPrivkey = toNat(privkey)
-            return secp256k1_ec_seckey_verify(ctx, nPrivkey) == 1
+                val result = secp256k1_ec_seckey_verify(ctx, nPrivkey) == 1
+                callbackHandler.checkForErrors()
+                return result
+            }
         }
     }
 
     public override fun pubkeyCreate(privkey: ByteArray): ByteArray {
         require(privkey.size == 32)
+        CallbackHandler(ctx).use { callbackHandler ->
             memScoped {
                 val nPrivkey = toNat(privkey)
                 val nPubkey = alloc<secp256k1_pubkey>()
-            secp256k1_ec_pubkey_create(ctx, nPubkey.ptr, nPrivkey).requireSuccess("secp256k1_ec_pubkey_create() failed")
+                secp256k1_ec_pubkey_create(ctx, nPubkey.ptr, nPrivkey).requireSuccess(callbackHandler, "secp256k1_ec_pubkey_create() failed")
                 return serializePubkey(nPubkey)
             }
         }
+    }
 
     public override fun pubkeyParse(pubkey: ByteArray): ByteArray {
         require(pubkey.size == 33 || pubkey.size == 65)
+        CallbackHandler(ctx).use { callbackHandler ->
             memScoped {
                 val nPubkey = allocPublicKey(pubkey)
-            return serializePubkey(nPubkey)
+                val result = serializePubkey(nPubkey)
+                callbackHandler.checkForErrors()
+                return result
+            }
         }
     }
 
     public override fun privKeyNegate(privkey: ByteArray): ByteArray {
         require(privkey.size == 32)
+        CallbackHandler(ctx).use { callbackHandler ->
             memScoped {
                 val negated = privkey.copyOf()
                 val negPriv = toNat(negated)
-            secp256k1_ec_seckey_negate(ctx, negPriv).requireSuccess("secp256k1_ec_seckey_negate() failed")
+                secp256k1_ec_seckey_negate(ctx, negPriv).requireSuccess(callbackHandler, "secp256k1_ec_seckey_negate() failed")
                 return negated
             }
         }
+    }
 
     public override fun privKeyTweakAdd(privkey: ByteArray, tweak: ByteArray): ByteArray {
         require(privkey.size == 32)
+        CallbackHandler(ctx).use { callbackHandler ->
             memScoped {
                 val added = privkey.copyOf()
                 val natAdd = toNat(added)
                 val natTweak = toNat(tweak)
-            secp256k1_ec_seckey_tweak_add(ctx, natAdd, natTweak).requireSuccess("secp256k1_ec_seckey_tweak_add() failed")
+                secp256k1_ec_seckey_tweak_add(ctx, natAdd, natTweak).requireSuccess(callbackHandler, "secp256k1_ec_seckey_tweak_add() failed")
                 return added
             }
         }
+    }
 
     public override fun privKeyTweakMul(privkey: ByteArray, tweak: ByteArray): ByteArray {
         require(privkey.size == 32)
+        CallbackHandler(ctx).use { callbackHandler ->
             memScoped {
                 val multiplied = privkey.copyOf()
                 val natMul = toNat(multiplied)
                 val natTweak = toNat(tweak)
-            secp256k1_ec_privkey_tweak_mul(ctx, natMul, natTweak).requireSuccess("secp256k1_ec_privkey_tweak_mul() failed")
+                secp256k1_ec_privkey_tweak_mul(ctx, natMul, natTweak).requireSuccess(callbackHandler, "secp256k1_ec_privkey_tweak_mul() failed")
                 return multiplied
             }
         }
+    }
 
     public override fun pubKeyNegate(pubkey: ByteArray): ByteArray {
         require(pubkey.size == 33 || pubkey.size == 65)
+        CallbackHandler(ctx).use { callbackHandler ->
             memScoped {
                 val nPubkey = allocPublicKey(pubkey)
-            secp256k1_ec_pubkey_negate(ctx, nPubkey.ptr).requireSuccess("secp256k1_ec_pubkey_negate() failed")
+                secp256k1_ec_pubkey_negate(ctx, nPubkey.ptr).requireSuccess(callbackHandler, "secp256k1_ec_pubkey_negate() failed")
                 return serializePubkey(nPubkey)
             }
         }
+    }
 
     public override fun pubKeyTweakAdd(pubkey: ByteArray, tweak: ByteArray): ByteArray {
         require(pubkey.size == 33 || pubkey.size == 65)
+        CallbackHandler(ctx).use { callbackHandler ->
             memScoped {
                 val nPubkey = allocPublicKey(pubkey)
                 val nTweak = toNat(tweak)
-            secp256k1_ec_pubkey_tweak_add(ctx, nPubkey.ptr, nTweak).requireSuccess("secp256k1_ec_pubkey_tweak_add() failed")
+                secp256k1_ec_pubkey_tweak_add(ctx, nPubkey.ptr, nTweak).requireSuccess(callbackHandler, "secp256k1_ec_pubkey_tweak_add() failed")
                 return serializePubkey(nPubkey)
             }
         }
+    }
 
     public override fun pubKeyTweakMul(pubkey: ByteArray, tweak: ByteArray): ByteArray {
         require(pubkey.size == 33 || pubkey.size == 65)
+        CallbackHandler(ctx).use { callbackHandler ->
             memScoped {
                 val nPubkey = allocPublicKey(pubkey)
                 val nTweak = toNat(tweak)
-            secp256k1_ec_pubkey_tweak_mul(ctx, nPubkey.ptr, nTweak).requireSuccess("secp256k1_ec_pubkey_tweak_mul() failed")
+                secp256k1_ec_pubkey_tweak_mul(ctx, nPubkey.ptr, nTweak).requireSuccess(callbackHandler, "secp256k1_ec_pubkey_tweak_mul() failed")
                 return serializePubkey(nPubkey)
             }
         }
+    }
 
     public override fun pubKeyCombine(pubkeys: Array<ByteArray>): ByteArray {
         pubkeys.forEach { require(it.size == 33 || it.size == 65) }
+        CallbackHandler(ctx).use { callbackHandler ->
             memScoped {
                 val nPubkeys = pubkeys.map { allocPublicKey(it).ptr }
                 val combined = alloc<secp256k1_pubkey>()
-            secp256k1_ec_pubkey_combine(ctx, combined.ptr, nPubkeys.toCValues(), pubkeys.size.convert()).requireSuccess("secp256k1_ec_pubkey_combine() failed")
+                secp256k1_ec_pubkey_combine(ctx, combined.ptr, nPubkeys.toCValues(), pubkeys.size.convert()).requireSuccess(callbackHandler, "secp256k1_ec_pubkey_combine() failed")
                 return serializePubkey(combined)
             }
         }
+    }
 
     public override fun ecdh(privkey: ByteArray, pubkey: ByteArray): ByteArray {
         require(privkey.size == 32)
         require(pubkey.size == 33 || pubkey.size == 65)
+        CallbackHandler(ctx).use { callbackHandler ->
             memScoped {
                 val nPubkey = allocPublicKey(pubkey)
                 val nPrivkey = toNat(privkey)
                 val output = allocArray<UByteVar>(32)
-            secp256k1_ecdh(ctx, output, nPubkey.ptr, nPrivkey, null, null).requireSuccess("secp256k1_ecdh() failed")
+                secp256k1_ecdh(ctx, output, nPubkey.ptr, nPrivkey, null, null).requireSuccess(callbackHandler, "secp256k1_ecdh() failed")
                 return output.readBytes(32)
             }
         }
+    }
 
     public override fun ecdsaRecover(sig: ByteArray, message: ByteArray, recid: Int): ByteArray {
         require(sig.size == 64)
         require(message.size == 32)
+        // we do not check that recid is valid, which should trigger our illegal callback handler to throw a Secp256k1IllegalCallbackException
+        // require(recid in 0..3)
+
+        CallbackHandler(ctx).use { callbackHandler ->
             memScoped {
                 val nSig = toNat(sig)
                 val rSig = alloc<secp256k1_ecdsa_recoverable_signature>()
-            secp256k1_ecdsa_recoverable_signature_parse_compact(ctx, rSig.ptr, nSig, recid).requireSuccess("secp256k1_ecdsa_recoverable_signature_parse_compact() failed")
+                secp256k1_ecdsa_recoverable_signature_parse_compact(ctx, rSig.ptr, nSig, recid).requireSuccess(callbackHandler, "secp256k1_ecdsa_recoverable_signature_parse_compact() failed")
                 val nMessage = toNat(message)
                 val pubkey = alloc<secp256k1_pubkey>()
-            secp256k1_ecdsa_recover(ctx, pubkey.ptr, rSig.ptr, nMessage).requireSuccess("secp256k1_ecdsa_recover() failed")
+                secp256k1_ecdsa_recover(ctx, pubkey.ptr, rSig.ptr, nMessage).requireSuccess(callbackHandler, "secp256k1_ecdsa_recover() failed")
                 return serializePubkey(pubkey)
             }
         }
+    }
 
     public override fun compact2der(sig: ByteArray): ByteArray {
         require(sig.size == 64)
+        CallbackHandler(ctx).use { callbackHandler ->
             memScoped {
                 val nSig = allocSignature(sig)
                 val natOutput = allocArray<UByteVar>(73)
                 val len = alloc<size_tVar>()
                 len.value = 73.convert()
-            secp256k1_ecdsa_signature_serialize_der(ctx, natOutput, len.ptr, nSig.ptr).requireSuccess("secp256k1_ecdsa_signature_serialize_der() failed")
+                secp256k1_ecdsa_signature_serialize_der(ctx, natOutput, len.ptr, nSig.ptr).requireSuccess(callbackHandler, "secp256k1_ecdsa_signature_serialize_der() failed")
                 return natOutput.readBytes(len.value.toInt())
             }
         }
+    }
 
     override fun verifySchnorr(signature: ByteArray, data: ByteArray, pub: ByteArray): Boolean {
         require(signature.size == 64)
         require(data.size == 32)
         require(pub.size == 32)
+        CallbackHandler(ctx).use { callbackHandler ->
             memScoped {
                 val nPub = toNat(pub)
                 val pubkey = alloc<secp256k1_xonly_pubkey>()
-            secp256k1_xonly_pubkey_parse(ctx, pubkey.ptr, nPub).requireSuccess("secp256k1_xonly_pubkey_parse() failed")
+                secp256k1_xonly_pubkey_parse(ctx, pubkey.ptr, nPub).requireSuccess(callbackHandler, "secp256k1_xonly_pubkey_parse() failed")
                 val nData = toNat(data)
                 val nSig = toNat(signature)
-            return secp256k1_schnorrsig_verify(ctx, nSig, nData, 32, pubkey.ptr) == 1
+                return secp256k1_schnorrsig_verify(ctx, nSig, nData, 32u, pubkey.ptr) == 1
+            }
         }
     }
 
@@ -240,17 +336,19 @@ public object Secp256k1Native : Secp256k1 {
         require(sec.size == 32)
         require(data.size == 32)
         auxrand32?.let { require(it.size == 32) }
+        CallbackHandler(ctx).use { callbackHandler ->
             memScoped {
                 val nSec = toNat(sec)
                 val nData = toNat(data)
                 val nAuxrand32 = auxrand32?.let { toNat(it) }
                 val nSig = allocArray<UByteVar>(64)
                 val keypair = alloc<secp256k1_keypair>()
-            secp256k1_keypair_create(ctx, keypair.ptr, nSec).requireSuccess("secp256k1_keypair_create() failed")
-            secp256k1_schnorrsig_sign32(ctx, nSig, nData, keypair.ptr, nAuxrand32).requireSuccess("secp256k1_ecdsa_sign() failed")
+                secp256k1_keypair_create(ctx, keypair.ptr, nSec).requireSuccess(callbackHandler, "secp256k1_keypair_create() failed")
+                secp256k1_schnorrsig_sign32(ctx, nSig, nData, keypair.ptr, nAuxrand32).requireSuccess(callbackHandler, "secp256k1_ecdsa_sign() failed")
                 return nSig.readBytes(64)
             }
         }
+    }
     
     public override fun cleanup() {
         secp256k1_context_destroy(ctx)

tests/src/commonTest/kotlin/fr/acinq/secp256k1/Secp256k1Test.kt

@@ -275,6 +275,11 @@ class Secp256k1Test {
         val pub0 = Secp256k1.ecdsaRecover(sig, message, 0)
         val pub1 = Secp256k1.ecdsaRecover(sig, message, 1)
         assertTrue(pub.contentEquals(pub0) || pub.contentEquals(pub1))
+
+        // this is a special case, ecdsaRecover explicitly does not check that recid is valid, which triggers our illegal callback handler
+        assertFailsWith(Secp256k1IllegalCallbackException::class) {
+            Secp256k1.ecdsaRecover(sig, message, 4)
+        }
     }
 
     @Test