Merge pull request #39 from matrix-org/rav/messages_on_heap

Allocate memory for message blobs on the heap

1 files changed, 43 insertions, 25 deletions

diff --git a/javascript/olm_inbound_group_session.js b/javascript/olm_inbound_group_session.js
index 1b7fcfe..2e4727f 100644
--- a/javascript/olm_inbound_group_session.js
+++ b/javascript/olm_inbound_group_session.js
@@ -64,33 +64,51 @@ InboundGroupSession.prototype['create'] = restore_stack(function(session_key) {
 InboundGroupSession.prototype['decrypt'] = restore_stack(function(
     message
 ) {
-    var message_array = array_from_string(message);
-    var message_buffer = stack(message_array);
-    var max_plaintext_length = inbound_group_session_method(
-        Module['_olm_group_decrypt_max_plaintext_length']
-    )(this.ptr, message_buffer, message_array.length);
-    // caculating the length destroys the input buffer.
-    // So we copy the array to a new buffer
-    var message_buffer = stack(message_array);
-    var plaintext_buffer = stack(max_plaintext_length + NULL_BYTE_PADDING_LENGTH);
-    var message_index = stack(4);
-    var plaintext_length = inbound_group_session_method(Module["_olm_group_decrypt"])(
-        this.ptr,
-        message_buffer, message_array.length,
-        plaintext_buffer, max_plaintext_length,
-        message_index
-    );
+    var message_buffer, plaintext_buffer, plaintext_length;
 
-    // Pointer_stringify requires a null-terminated argument (the optional
-    // 'len' argument doesn't work for UTF-8 data).
-    Module['setValue'](
-        plaintext_buffer+plaintext_length,
-        0, "i8"
-    );
+    try {
+        message_buffer = malloc(message.length);
+        Module['writeAsciiToMemory'](message, message_buffer, true);
+
+        var max_plaintext_length = inbound_group_session_method(
+            Module['_olm_group_decrypt_max_plaintext_length']
+        )(this.ptr, message_buffer, message.length);
+
+        // caculating the length destroys the input buffer, so we need to re-copy it.
+        Module['writeAsciiToMemory'](message, message_buffer, true);
+
+        plaintext_buffer = malloc(max_plaintext_length + NULL_BYTE_PADDING_LENGTH);
+        var message_index = stack(4);
 
-    return {
-        "plaintext": Pointer_stringify(plaintext_buffer),
-        "message_index": Module['getValue'](message_index, "i32")
+        plaintext_length = inbound_group_session_method(
+            Module["_olm_group_decrypt"]
+        )(
+            this.ptr,
+            message_buffer, message.length,
+            plaintext_buffer, max_plaintext_length,
+            message_index
+        );
+
+        // UTF8ToString requires a null-terminated argument, so add the
+        // null terminator.
+        Module['setValue'](
+            plaintext_buffer+plaintext_length,
+            0, "i8"
+        );
+
+        return {
+            "plaintext": UTF8ToString(plaintext_buffer),
+            "message_index": Module['getValue'](message_index, "i32")
+        }
+    } finally {
+        if (message_buffer !== undefined) {
+            free(message_buffer);
+        }
+        if (plaintext_buffer !== undefined) {
+            // don't leave a copy of the plaintext in the heap.
+            bzero(plaintext_buffer, plaintext_length + NULL_BYTE_PADDING_LENGTH);
+            free(plaintext_buffer);
+        }
     }
 });