crypto: Document when a key export may panic.

matrix_sdk/src/client.rs

@@ -1727,6 +1727,11 @@ impl Client {
     /// returns `true` the `InboundGroupSessoin` will be included in the export,
     /// if the closure returns `false` it will not be included.
     ///
+    /// # Panics
+    ///
+    /// This method will panic if it can't get enough randomness from the OS to
+    /// encrypt the exported keys securely.
+    ///
     /// # Examples
     ///
     /// ```no_run

matrix_sdk_crypto/src/file_encryption/key_export.rs

@@ -122,6 +122,11 @@ pub fn decrypt_key_export(
 /// attacks. Should be at least `10000`, while values in the `100000` ranges
 /// should be preferred.
 ///
+/// # Panics
+///
+/// This method will panic if it can't get enough randomness from the OS to
+/// encrypt the exported keys securely.
+///
 /// # Examples
 /// ```no_run
 /// # use matrix_sdk_crypto::{OlmMachine, encrypt_key_export};

matrix_sdk_crypto/src/machine.rs

@@ -172,7 +172,7 @@ impl OlmMachine {
         let store = Store::new(store);
         let verification_machine = VerificationMachine::new(account.clone(), store.clone());
         let user_id = Arc::new(user_id.clone());
-        let device_id: Arc<DeviceIdBox> = Arc::new(device_id.into());
+        let device_id: Arc<DeviceIdBox> = Arc::new(device_id);
         let key_request_machine =
             KeyRequestMachine::new(user_id.clone(), device_id.clone(), store.clone());
 
@@ -1612,6 +1612,17 @@ impl OlmMachine {
 
     /// Export the keys that match the given predicate.
     ///
+    /// # Arguments
+    ///
+    /// * `predicate` - A closure that will be called for every known
+    /// `InboundGroupSession`, which represents a room key. If the closure
+    /// returns `true` the `InboundGroupSessoin` will be included in the export,
+    /// if the closure returns `false` it will not be included.
+    ///
+    /// # Panics
+    ///
+    /// This method will panic if it can't get enough randomness from the OS to
+    /// encrypt the exported keys securely.
     ///
     /// # Examples
     ///