fix(protocol): harden gateway contract validation

gen/rust/protocol.rs

@@ -1,6 +1,6 @@
 // Code generated by tools/generate.py; DO NOT EDIT.
 #![allow(non_snake_case)]
-pub const SCHEMA_SHA256: &str = "e35414af52d7a097dea05567fdab11f842a42e529fb6cbedd281c48dbf930b17";
+pub const SCHEMA_SHA256: &str = "e98c75ef81bbeac6be2b8f11202c1ffecec0aa515b48576a26756290e99d5dd8";
 pub const CURRENT_WIRE_VERSION: &str = "1";
 pub const N_MINUS_1_WIRE_VERSION: &str = "0";
 pub const N_MINUS_2_WIRE_VERSION: &str = "-1";
@@ -10,6 +10,27 @@ pub type JsonObject = std::collections::BTreeMap<String, String>;
 pub struct ValidationError { pub field: &'static str, pub code: &'static str }
 impl ValidationError { pub const fn new(field: &'static str, code: &'static str) -> Self { Self { field, code } } }
 
+fn base64url_value(value: u8) -> Option<u8> {
+    match value {
+        b'A'..=b'Z' => Some(value - b'A'),
+        b'a'..=b'z' => Some(value - b'a' + 26),
+        b'0'..=b'9' => Some(value - b'0' + 52),
+        b'-' => Some(62),
+        b'_' => Some(63),
+        _ => None,
+    }
+}
+fn valid_base64_url(value: &str) -> bool {
+    let bytes = value.as_bytes();
+    if bytes.is_empty() || bytes.iter().any(|byte| base64url_value(*byte).is_none()) { return false; }
+    match bytes.len() % 4 {
+        0 => true,
+        2 => base64url_value(*bytes.last().unwrap()).unwrap() & 0x0f == 0,
+        3 => base64url_value(*bytes.last().unwrap()).unwrap() & 0x03 == 0,
+        _ => false,
+    }
+}
+
 #[derive(Debug, Clone, PartialEq, Eq)]
 pub struct AllocationPolicy {
     minimumKbps: i64,
@@ -259,6 +280,7 @@ impl ChannelFrame {
         if self.fragmentCount > 16 { return Err(ValidationError::new("fragment_count", "maximum")); }
         if self.timestampMs < 0 { return Err(ValidationError::new("timestamp_ms", "minimum")); }
         if self.payload.len() > 87384 { return Err(ValidationError::new("payload", "max_length")); }
+        if self.payload.as_bytes().len() > 65536 { return Err(ValidationError::new("payload", "max_bytes")); }
         if self.fragmentIndex >= self.fragmentCount { return Err(ValidationError::new("fragment_index", "invalid_order")); }
         Ok(())
     }
@@ -692,10 +714,12 @@ impl GatewayClipboardText {
     pub fn validate(&self) -> Result<(), ValidationError> {
         if self.direction != "client_to_provider" && self.direction != "provider_to_client" { return Err(ValidationError::new("direction", "invalid_value")); }
         if self.text.len() > 65536 { return Err(ValidationError::new("text", "max_length")); }
+        if self.text.as_bytes().len() > 65536 { return Err(ValidationError::new("text", "max_bytes")); }
         if self.encoding != "utf-8" { return Err(ValidationError::new("encoding", "invalid_value")); }
         if self.loopToken.is_empty() { return Err(ValidationError::new("loop_token", "required")); }
         if !self.loopToken.is_empty() && self.loopToken.len() < 16 { return Err(ValidationError::new("loop_token", "min_length")); }
         if self.loopToken.len() > 128 { return Err(ValidationError::new("loop_token", "max_length")); }
+        if !valid_base64_url(self.loopToken.as_str()) { return Err(ValidationError::new("loop_token", "invalid_format")); }
         Ok(())
     }
     pub fn direction(&self) -> &String { &self.direction }