fix(protocol): harden gateway contract validation

gen/swift/Protocol.swift

@@ -1,12 +1,21 @@
 // Code generated by tools/generate.py; DO NOT EDIT.
 import Foundation
 public typealias JSONObject = [String: String]
-public let schemaSHA256 = "e35414af52d7a097dea05567fdab11f842a42e529fb6cbedd281c48dbf930b17"
+public let schemaSHA256 = "e98c75ef81bbeac6be2b8f11202c1ffecec0aa515b48576a26756290e99d5dd8"
 public let currentWireVersion = "1"
 public let nMinus1WireVersion = "0"
 public let nMinus2WireVersion = "-1"
 public struct ContractValidationError: Error, Equatable { public let field: String; public let code: String }
 private struct AnyCodingKey: CodingKey { let stringValue: String; let intValue: Int?; init?(stringValue: String) { self.stringValue = stringValue; self.intValue = nil }; init?(intValue: Int) { self.stringValue = String(intValue); self.intValue = intValue } }
+private func validBase64URL(_ value: String) -> Bool {
+    guard !value.isEmpty, value.utf8.allSatisfy({ byte in
+        (byte >= 65 && byte <= 90) || (byte >= 97 && byte <= 122) || (byte >= 48 && byte <= 57) || byte == 45 || byte == 95
+    }) else { return false }
+    let padding = String(repeating: "=", count: (4 - value.utf8.count % 4) % 4)
+    let standard = value.replacingOccurrences(of: "-", with: "+").replacingOccurrences(of: "_", with: "/") + padding
+    guard let decoded = Data(base64Encoded: standard) else { return false }
+    return decoded.base64EncodedString().replacingOccurrences(of: "+", with: "-").replacingOccurrences(of: "/", with: "_").replacingOccurrences(of: "=", with: "") == value
+}
 
 public struct AllocationPolicy: Codable, Equatable {
     public let minimumKbps: Int64
@@ -343,6 +352,7 @@ public struct ChannelFrame: Codable, Equatable {
         if self.fragmentCount > 16 { throw ContractValidationError(field: "fragment_count", code: "maximum") }
         if self.timestampMs < 0 { throw ContractValidationError(field: "timestamp_ms", code: "minimum") }
         if self.payload.utf8.count > 87384 { throw ContractValidationError(field: "payload", code: "max_length") }
+        if self.payload.utf8.count > 65536 { throw ContractValidationError(field: "payload", code: "max_bytes") }
         if fragmentIndex >= fragmentCount { throw ContractValidationError(field: "fragment_index", code: "invalid_order") }
     }
 
@@ -926,10 +936,12 @@ public struct GatewayClipboardText: Codable, Equatable {
     public func validate() throws {
         if !["client_to_provider", "provider_to_client"].contains(self.direction) { throw ContractValidationError(field: "direction", code: "invalid_value") }
         if self.text.utf8.count > 65536 { throw ContractValidationError(field: "text", code: "max_length") }
+        if self.text.utf8.count > 65536 { throw ContractValidationError(field: "text", code: "max_bytes") }
         if self.encoding != "utf-8" { throw ContractValidationError(field: "encoding", code: "invalid_value") }
         if self.loopToken.isEmpty { throw ContractValidationError(field: "loop_token", code: "required") }
         if !self.loopToken.isEmpty && self.loopToken.utf8.count < 16 { throw ContractValidationError(field: "loop_token", code: "min_length") }
         if self.loopToken.utf8.count > 128 { throw ContractValidationError(field: "loop_token", code: "max_length") }
+        if !validBase64URL(self.loopToken) { throw ContractValidationError(field: "loop_token", code: "invalid_format") }
     }
 
     public static func decodeJSON(_ data: Data) throws -> Self { try JSONDecoder().decode(Self.self, from: data) }