Initial Commit

2026-05-28 10:21:26 +02:00 · 2019-10-12 02:36:31 -05:00
commit 0a8b992628
5 changed files with 252 additions and 0 deletions
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+# Content Cache Locator
+
+The locator is the service that provides a list of registered local caches.
+
+Oddly, Apple chose to register the caches based on the public IP address of the
+registered cache.
+
+The locator service URL is: `https://lcdn-locator.apple.com/lcdn/locate`
+
+The request JSON to locate all the caches is:
+
+```json
+{
+    "ranked-results": true,
+    "locator-tag": "#f5cfd4d0", // Seems to be different each time.
+    "local-addresses": [
+      "10.0.0.60" // My local address.
+    ],
+    "public-address-ranges": [
+      []
+    ],
+    "locator-software": [
+      {
+        "build": "19A578c",
+        "type": "system",
+        "name": "Mac OS X",
+        "version": "10.15"
+      },
+      {
+        "id": "com.apple.AssetCacheLocatorService",
+        "executable": "AssetCacheLocatorService",
+        "type": "bundle",
+        "name": "AssetCacheLocatorService",
+        "version": "106.1"
+      }
+    ]
+}
+```
+
+The response looks similar to:
+
+```json
+{
+  "connect-timeout": 0.75,
+  "servers": [
+    {
+      "address": "10.0.0.60",
+      "port": 54459,
+      "guid": "C881402D-001C-49BD-8672-7BA84A69C9AB",
+      "version": "233",
+      "connect-timeout": 0.5,
+      "details": {
+        "capabilities": {
+          "ur": true,
+          "sc": true,
+          "pc": true,
+          "im": true,
+          "ns": true,
+          "query-parameters": true
+        },
+        "cache-size": 150000000000,
+        "ac-power": true,
+        "is-portable": true,
+        "local-network": [
+          {
+            "speed": 30,
+            "wired": false
+          }
+        ]
+      },
+      "rank": 1
+    }
+  ],
+  "validity-interval": 3600
+}
+```
+
+## Notes
+
+Given the usage of public IPs as the way to differentiate between caches,
+I wonder if it would be possible to use shared VPNs and receive a list
+of caches on the shared VPN. This is quite concerning, though likely has
+no actual security impact given that the local clients should not be available
+between VPN clients.
+
+Also, the reason that Apple seems to register content caches at all is related to
+region restriction control of cached content (movies that aren't available in certain regions.)
+
+Frankly, I believe that Apple should reconsider this system and use mDNS to discover content caches. It just makes more sense, and Apple already uses mDNS (because of Bonjour), so why not?
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+import 'dart:async';
+import 'dart:convert';
+import 'dart:io';
+
+Future<void> main(List<String> args) async {
+  var client = new HttpClient();
+  var request = await client.postUrl(Uri.parse("https://lcdn-locator.apple.com/lcdn/locate"));
+  request.writeln(json.encode({
+    "ranked-results": true,
+    "locator-tag": "#f5cfd4d0",
+    "local-addresses": [
+      args[0]
+    ],
+    "public-address-ranges": [
+      []
+    ],
+    "locator-software": [
+      {
+        "build": "19A578c",
+        "type": "system",
+        "name": "Mac OS X",
+        "version": "10.15"
+      },
+      {
+        "id": "com.apple.AssetCacheLocatorService",
+        "executable": "AssetCacheLocatorService",
+        "type": "bundle",
+        "name": "AssetCacheLocatorService",
+        "version": "106.1"
+      }
+    ]
+  }));
+  var response = await request.close();
+  var content = await utf8.decodeStream(response);
+  var data = json.decode(content);
+  print(const JsonEncoder.withIndent("  ").convert(data));
+  client.close();
+}