Fixed error in nip04 implementation. Now working

nostr_core/nip044.c

@@ -62,8 +62,8 @@ static unsigned char* pad_plaintext(const char* plaintext, size_t* padded_len) {
         return NULL;
     }
     
-    // NIP-44 allows empty messages (unpadded_len can be 0)
-    *padded_len = calc_padded_len(unpadded_len + 2); // +2 for length prefix
+    size_t padded_content_len = calc_padded_len(unpadded_len);
+    *padded_len = padded_content_len + 2; // Add 2 bytes for the length prefix
     unsigned char* padded = malloc(*padded_len);
     if (!padded) return NULL;
     
@@ -71,33 +71,34 @@ static unsigned char* pad_plaintext(const char* plaintext, size_t* padded_len) {
     padded[0] = (unpadded_len >> 8) & 0xFF;
     padded[1] = unpadded_len & 0xFF;
     
-    // Copy plaintext (if any)
-    if (unpadded_len > 0) {
-        memcpy(padded + 2, plaintext, unpadded_len);
-    }
-    
-    // Zero-fill padding
-    memset(padded + 2 + unpadded_len, 0, *padded_len - 2 - unpadded_len);
+    // Copy plaintext and add zero-padding
+    memcpy(padded + 2, plaintext, unpadded_len);
+    memset(padded + 2 + unpadded_len, 0, padded_content_len - unpadded_len);
     
     return padded;
 }
 
-// NIP-44 unpadding (per spec)  
+// NIP-44 unpadding (per spec)
 static char* unpad_plaintext(const unsigned char* padded, size_t padded_len) {
-    if (padded_len < 2) return NULL;
-    
-    // Read length prefix (big-endian u16)
+    if (padded_len < 4) return NULL; 
+
     size_t unpadded_len = (padded[0] << 8) | padded[1];
-    if (unpadded_len > padded_len - 2) {
-        return NULL;
-    }
-    
-    // Verify padding length matches expected
-    size_t expected_padded_len = calc_padded_len(unpadded_len + 2);
+    size_t expected_padded_len = calc_padded_len(unpadded_len);
+
+    printf("--- unpad_plaintext DEBUG ---\n");
+    printf("padded_len: %zu\n", padded_len);
+    printf("unpadded_len: %zu\n", unpadded_len);
+    printf("expected_padded_len: %zu\n", expected_padded_len);
+    printf("--- end unpad_plaintext DEBUG ---\n");
+
     if (padded_len != expected_padded_len) {
         return NULL;
     }
-    
+
+    if (unpadded_len > padded_len - 2) {
+        return NULL;
+    }
+
     char* plaintext = malloc(unpadded_len + 1);
     if (!plaintext) return NULL;
     
@@ -339,9 +340,9 @@ int nostr_nip44_decrypt(const unsigned char* recipient_private_key,
     }
     
     unsigned char* nonce = payload + 1;
-    size_t ciphertext_len = payload_len - 65; // payload - version - nonce - mac
     unsigned char* ciphertext = payload + 33;
     unsigned char* received_mac = payload + payload_len - 32;
+    size_t ciphertext_len = (payload + payload_len - 32) - (payload + 33); // mac_start - ciphertext_start
     
     // Step 3: Compute ECDH shared secret
     unsigned char shared_secret[32];
@@ -402,6 +403,7 @@ int nostr_nip44_decrypt(const unsigned char* recipient_private_key,
         return NOSTR_ERROR_CRYPTO_FAILED;
     }
     
+    // Constant-time MAC verification
     // Constant-time MAC verification
     if (!constant_time_compare(received_mac, computed_mac, 32)) {
         memory_clear(shared_secret, 32);
@@ -439,6 +441,7 @@ int nostr_nip44_decrypt(const unsigned char* recipient_private_key,
         return NOSTR_ERROR_CRYPTO_FAILED;
     }
     
+    // Step 8: Remove padding according to NIP-44 spec
     // Step 8: Remove padding according to NIP-44 spec
     char* plaintext = unpad_plaintext(padded_plaintext, ciphertext_len);
     if (!plaintext) {