[Fix] Harden MTP codec, transport, and SDK security

example/server/src/handlers.rs

@@ -3,7 +3,9 @@ use std::collections::HashMap;
 use mtp::codec::{
     CommunicationType, CommunicationValue, DataType, DataTypeId, DataValue, InMemoryReplayGuard,
     ProtectedOpenOptions, ProtectionPolicy, ProtectionPurpose, SignaturePolicy, TypeMap,
-    forward_relay_frame, open_protected_with, open_relay_content, open_relay_metadata_with,
+    forward_relay_frame, open_protected_with_checked,
+    open_relay_content_with_limits_without_replay,
+    open_relay_metadata_with_checked,
 };
 use mtp::crypto::{Keyring, PublicKeyBundle};
 
@@ -65,7 +67,7 @@ fn process_direct_protected(
         ));
     }
 
-    let opened = open_protected_with(
+    let opened = open_protected_with_checked(
         msg,
         std::slice::from_ref(&host_keyring),
         None,
@@ -76,7 +78,7 @@ fn process_direct_protected(
             ProtectionPurpose::from(DIRECT_ENCRYPTION_PURPOSE),
             SIGNATURE_POLICY,
         ),
-        Some(accepted_messages),
+        accepted_messages,
     )
     .map_err(|e| format!("direct protected message could not be authenticated: {e}"))?;
     let signer_id = opened.signer_id;
@@ -133,7 +135,7 @@ fn process_sealed_relay(
         ));
     }
 
-    let metadata = open_relay_metadata_with(
+    let metadata = open_relay_metadata_with_checked(
         msg,
         std::slice::from_ref(&host_keyring),
         None,
@@ -141,7 +143,7 @@ fn process_sealed_relay(
             resolve_signer_key(signer_id, registered_clients).map(|key| vec![key])
         },
         SIGNATURE_POLICY,
-        Some(accepted_messages),
+        accepted_messages,
     )
     .map_err(|e| format!("metadata relay could not authenticate metadata: {e}"))?;
     println!(
@@ -160,7 +162,7 @@ fn process_sealed_relay(
             .len()
     );
 
-    let content_result = open_relay_content(
+    let content_result = open_relay_content_with_limits_without_replay(
         &metadata,
         host_keyring,
         &resolve_signer_key(metadata.signer_id(), registered_clients)

example/server/src/keys.rs

@@ -27,7 +27,7 @@ pub async fn export_host_public_keys(
     save_public_key_bundle(&bundle, "host.mpkb")?;
 
     /* The web client fetches the bundle as hex over HTTP. */
-    let bundle_hex = hex::encode(bundle.as_bytes());
+    let bundle_hex = hex::encode(bundle.try_as_bytes()?);
     fs::write("host_public_key_bundle.hex", &bundle_hex).await?;
     fs::create_dir_all("web-client/public").await?;
     fs::write("web-client/public/host_public_key_bundle.hex", &bundle_hex).await?;

example/server/src/main.rs

@@ -111,8 +111,9 @@ async fn main() -> Result<(), Box<dyn std::error::Error>> {
         }) as Pin<Box<dyn Future<Output = u64> + Send>>
     };
 
+    let decrypt_keyring_bytes = host_keyring.try_to_bytes()?;
     let decrypt_keyring = Arc::new(
-        match mtp::crypto::Keyring::from_bytes(&host_keyring.to_bytes()) {
+        match mtp::crypto::Keyring::from_bytes(&decrypt_keyring_bytes) {
             Ok(keyring) => keyring,
             Err(e) => {
                 return Err(format!("failed to re-load host keyring for decryption: {e}").into());