TLS Client Fingerprint

.swift-version

@@ -0,0 +1 @@
+wasm-5.7.1

Makefile

@@ -12,3 +12,7 @@ docc:
 
 github-pages:
 	echo "compute-runtime.swift.cloud" > docs/CNAME
+
+demo:
+	swift build -c debug --triple wasm32-unknown-wasi
+	fastly compute serve --skip-build --file ./.build/debug/*.wasm

Package.swift

@@ -15,6 +15,7 @@ let package = Package(
     ],
     targets: [
         .target(name: "Compute", dependencies: ["ComputeRuntime"]),
-        .target(name: "ComputeRuntime")
+        .target(name: "ComputeRuntime"),
+        .executableTarget(name: "Demo", dependencies: ["Compute"])
     ]
 )

Sources/Compute/IncomingRequest.swift

@@ -90,3 +90,10 @@ extension IncomingRequest {
         }
     }
 }
+
+extension IncomingRequest {
+
+    public func clientFingerprint() -> String? {
+        return try? request.tlsJa3Md5()
+    }
+}

Sources/Compute/Runtime/Request.swift

@@ -288,3 +288,12 @@ extension Request {
         return bytes.split { $0 == 0 }.compactMap { String(bytes: $0, encoding: .utf8) }
     }
 }
+
+extension Request {
+
+    public func tlsJa3Md5() throws -> String? {
+        return try wasiString(maxBufferLength: 16) { buffer, _, written in
+            fastly_http_req__downstream_tls_ja3_md5(buffer, &written)
+        }
+    }
+}

Sources/Compute/Runtime/Stubs.swift

@@ -130,6 +130,8 @@ func fastly_http_req__redirect_to_grip_proxy(_ backend: UnsafePointer<CChar>!, _
 
 func fastly_http_req__register_dynamic_backend(_ name: UnsafePointer<CChar>!, _ name_len: Int, _ target: UnsafePointer<CChar>!, _ target_len: Int, _ backend_config_mask: UInt32, _ backend_configuration: UnsafeMutablePointer<DynamicBackendConfig>!) -> Int32 { fatalError() }
 
+func fastly_http_req__downstream_tls_ja3_md5(_ value: UnsafeMutablePointer<UInt8>!, _ nwritten: UnsafeMutablePointer<Int>!) -> Int32 { fatalError() }
+
 /* FASTLY_HTTP_RESP */
 
 func fastly_http_resp__new(_ handle: UnsafeMutablePointer<WasiHandle>!) -> Int32 { fatalError() }

Sources/ComputeRuntime/include/ComputeRuntime.h

@@ -197,6 +197,9 @@ int fastly_http_req__redirect_to_websocket_proxy(const char *backend, size_t bac
 WASM_IMPORT("fastly_http_req", "redirect_to_grip_proxy")
 int fastly_http_req__redirect_to_grip_proxy(const char *backend, size_t backend_len);
 
+WASM_IMPORT("fastly_http_req", "downstream_tls_ja3_md5")
+int fastly_http_req__downstream_tls_ja3_md5(uint8_t *value, size_t *nwritten);
+
 WASM_IMPORT("fastly_http_req", "register_dynamic_backend")
 int fastly_http_req__register_dynamic_backend(const char *name,
                                               size_t name_len,

Sources/Demo/main.swift

@@ -0,0 +1,10 @@
+import Compute
+
+let router = Router()
+
+router.get("/") { req, res in
+    print("fingerprint:", req.clientFingerprint() ?? "(null)")
+    try await res.status(200).send("Hello, Swift")
+}
+
+try await router.listen()

fastly.toml

@@ -0,0 +1,2 @@
+language = "swift"
+manifest_version = 2