fix: derive node_id from pubkey instead of privkey

sc_derive_node_id() hashed the private key, while invite links
(joindialog.cpp) hashed the public key — giving two different
node_ids for the same keypair.

Removed sc_derive_node_id(), kept only sc_derive_node_id_from_pubkey().
All callers updated to use pubkey-based derivation.

src/config_updater.c

@@ -293,8 +293,8 @@ int config_ensure_keys_and_node_id(const char *filename) {
                    global->my_public_key_hex[0] ? global->my_public_key_hex : "NULL", new_pub_key);
     }
 
-    // ── Step 3: derive node_id from privkey ──
-    new_node_id = sc_derive_node_id(priv_bin);
+    // ── Step 3: derive node_id from pubkey ──
+    new_node_id = sc_derive_node_id_from_pubkey(pub_bin);
     if (!is_valid_node_id(global->my_node_id) || global->my_node_id != new_node_id) {
         need_node_id = 1;
         DEBUG_WARN(DEBUG_CATEGORY_CONFIG, "Node_id mismatch (or missing), fixing: config=%016llx derived=%016llx file=%s",

src/secure_channel.c

@@ -422,10 +422,10 @@ sc_status_t sc_derive_ed25519_pubkey(const uint8_t *x25519_privkey, uint8_t *ed2
     return SC_OK;
 }
 
-uint64_t sc_derive_node_id(const uint8_t *private_key) {
-    if (!private_key) { DEBUG_ERROR(DEBUG_CATEGORY_CRYPTO, "sc_derive_node_id: NULL private_key"); return 0; }
+uint64_t sc_derive_node_id_from_pubkey(const uint8_t *public_key) {
+    if (!public_key) { DEBUG_ERROR(DEBUG_CATEGORY_CRYPTO, "sc_derive_node_id_from_pubkey: NULL public_key"); return 0; }
     uint8_t sha_hash[SC_HASH_SIZE]; SC_SHA256_CTX ctx;
-    sc_sha256_init(&ctx); sc_sha256_update(&ctx, private_key, SC_PRIVKEY_SIZE); sc_sha256_final(&ctx, sha_hash);
+    sc_sha256_init(&ctx); sc_sha256_update(&ctx, public_key, SC_PUBKEY_SIZE); sc_sha256_final(&ctx, sha_hash);
     uint64_t node_id;
     memcpy(&node_id, sha_hash, 8);
     node_id &= 0x7FFFFFFFFFFFFFFFULL;

src/secure_channel.h

@@ -114,7 +114,7 @@ sc_status_t sc_ed25519_verify(const uint8_t pubkey[32], const uint8_t* msg, size
 
 sc_status_t sc_derive_ed25519_pubkey(const uint8_t *x25519_privkey, uint8_t *ed25519_pubkey_out);
 
-uint64_t sc_derive_node_id(const uint8_t *private_key);
+uint64_t sc_derive_node_id_from_pubkey(const uint8_t *public_key);
 
 
 #ifdef __cplusplus

src/utun_instance.c

@@ -90,10 +90,12 @@ static int instance_init_common(struct UTUN_INSTANCE* instance, struct UASYNC* u
         return -1;
     }
 
-    // Derive node_id from privkey if not set in config
+    // Derive node_id from pubkey if not set in config
     if (!instance->node_id) {
-        instance->node_id = sc_derive_node_id(instance->my_keys.private_key);
-        DEBUG_INFO(DEBUG_CATEGORY_CONFIG, "node_id derived from privkey: %016llx", (unsigned long long)instance->node_id);
+        uint8_t pubkey[SC_PUBKEY_SIZE];
+        sc_compute_public_key_from_private(instance->my_keys.private_key, pubkey);
+        instance->node_id = sc_derive_node_id_from_pubkey(pubkey);
+        DEBUG_INFO(DEBUG_CATEGORY_CONFIG, "node_id derived from pubkey: %016llx", (unsigned long long)instance->node_id);
     }
     
     if (sc_derive_ed25519_pubkey(instance->my_keys.private_key, instance->my_ed25519_pubkey) != SC_OK) {

tools/chatgui/src/joindialog.cpp

@@ -14,6 +14,7 @@
 #include <cstring>
 
 extern "C" {
+#include "../../../src/secure_channel.h"
 #include "../../../lib/sha256.h"
 }
 
@@ -92,14 +93,7 @@ JoinDialog::JoinDialog(UtunNode* node, DbManager* db, QWidget* parent)
             setStatus("");
             return;
         }
-        uint8_t hash[32];
-        SC_SHA256_CTX ctx;
-        sc_sha256_init(&ctx);
-        sc_sha256_update(&ctx, (const uint8_t*)d.pubkey.constData(), 32);
-        sc_sha256_final(&ctx, hash);
-        uint64_t nodeId;
-        memcpy(&nodeId, hash, sizeof(nodeId));
-        nodeId &= 0x7FFFFFFFFFFFFFFFULL;
+        uint64_t nodeId = sc_derive_node_id_from_pubkey((const uint8_t*)d.pubkey.constData());
 
         QStringList addrList;
         for (const auto& a : d.addrs) {
@@ -162,14 +156,7 @@ void JoinDialog::onConnectClicked() {
         return;
     }
 
-    uint8_t hash[32];
-    SC_SHA256_CTX ctx;
-    sc_sha256_init(&ctx);
-    sc_sha256_update(&ctx, (const uint8_t*)d.pubkey.constData(), 32);
-    sc_sha256_final(&ctx, hash);
-    uint64_t nodeId;
-    memcpy(&nodeId, hash, sizeof(nodeId));
-    nodeId &= 0x7FFFFFFFFFFFFFFFULL;
+    uint64_t nodeId = sc_derive_node_id_from_pubkey((const uint8_t*)d.pubkey.constData());
 
     GUI_INFO("join: decoded invite ch=%llu pubkey=%016llx... nodeId=0x%016llx addrs=%d",
              d.channelId, *(const uint64_t*)d.pubkey.constData(), nodeId, d.addrs.size());