Allocate memory for message blobs on the heap

Messages can be very large, so we don't really want to allocate them on the
stack. Switch to using the heap for them, and try to clean up some of the
string handling while we're at it.

javascript/olm_inbound_group_session.js

@@ -64,34 +64,50 @@ 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, plaintext_buffer;
-    var message_buffer = stack(message_array);
+
+    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_array.length);
+        )(this.ptr, message_buffer, message.length);
-    // caculating the length destroys the input buffer.
+
-    // So we copy the array to a new buffer
+        // caculating the length destroys the input buffer, so we need to re-copy it.
-    var message_buffer = stack(message_array);
+        Module['writeAsciiToMemory'](message, message_buffer, true);
-    var plaintext_buffer = stack(max_plaintext_length + NULL_BYTE_PADDING_LENGTH);
+
+        plaintext_buffer = malloc(max_plaintext_length + NULL_BYTE_PADDING_LENGTH);
         var message_index = stack(4);
-    var plaintext_length = inbound_group_session_method(Module["_olm_group_decrypt"])(
+
+        var plaintext_length = inbound_group_session_method(
+            Module["_olm_group_decrypt"]
+        )(
             this.ptr,
-        message_buffer, message_array.length,
+            message_buffer, message.length,
             plaintext_buffer, max_plaintext_length,
             message_index
         );
 
-    // Pointer_stringify requires a null-terminated argument (the optional
+        // UTF8ToString requires a null-terminated argument, so add the
-    // 'len' argument doesn't work for UTF-8 data).
+        // null terminator.
         Module['setValue'](
             plaintext_buffer+plaintext_length,
             0, "i8"
         );
 
         return {
-        "plaintext": Pointer_stringify(plaintext_buffer),
+            "plaintext": UTF8ToString(plaintext_buffer),
             "message_index": Module['getValue'](message_index, "i32")
         }
+    } finally {
+        if (message_buffer !== undefined) {
+            free(message_buffer);
+        }
+        if (plaintext_buffer !== undefined) {
+            free(plaintext_buffer);
+        }
+    }
 });
 
 InboundGroupSession.prototype['session_id'] = restore_stack(function() {

javascript/olm_outbound_group_session.js

@@ -63,20 +63,36 @@ OutboundGroupSession.prototype['create'] = restore_stack(function() {
     );
 });
 
-OutboundGroupSession.prototype['encrypt'] = restore_stack(function(plaintext) {
+OutboundGroupSession.prototype['encrypt'] = function(plaintext) {
-    var plaintext_array = array_from_string(plaintext);
+    var plaintext_buffer, message_buffer;
+    try {
+        var plaintext_length = Module['lengthBytesUTF8'](plaintext);
+
         var message_length = outbound_group_session_method(
             Module['_olm_group_encrypt_message_length']
-    )(this.ptr, plaintext_array.length);
+        )(this.ptr, plaintext_length);
-    var plaintext_buffer = stack(plaintext_array);
+
-    var message_buffer = stack(message_length + NULL_BYTE_PADDING_LENGTH);
+        // need to allow space for the terminator (which stringToUTF8 always
+        // writes), hence + 1.
+        plaintext_buffer = malloc(plaintext_length + 1);
+        Module['stringToUTF8'](plaintext, plaintext_buffer, plaintext_length + 1);
+
+        message_buffer = malloc(message_length + NULL_BYTE_PADDING_LENGTH);
         outbound_group_session_method(Module['_olm_group_encrypt'])(
             this.ptr,
-        plaintext_buffer, plaintext_array.length,
+            plaintext_buffer, plaintext_length,
             message_buffer, message_length
         );
-    return Pointer_stringify(message_buffer);
+        return Module['UTF8ToString'](message_buffer);
-});
+    } finally {
+        if (plaintext_buffer !== undefined) {
+            free(plaintext_buffer);
+        }
+        if (message_buffer !== undefined) {
+            free(message_buffer);
+        }
+    }
+};
 
 OutboundGroupSession.prototype['session_id'] = restore_stack(function() {
     var length = outbound_group_session_method(

javascript/olm_post.js

@@ -4,9 +4,11 @@ var free = Module['_free'];
 var Pointer_stringify = Module['Pointer_stringify'];
 var OLM_ERROR = Module['_olm_error']();
 
-/* The 'length' argument to Pointer_stringify doesn't work if the input includes
+/* The 'length' argument to Pointer_stringify doesn't work if the input
- * characters >= 128; we therefore need to add a NULL character to all of our
+ * includes characters >= 128, which makes Pointer_stringify unreliable. We
- * strings. This acts as a symbolic constant to help show what we're doing.
+ * could use it on strings which are known to be ascii, but that seems
+ * dangerous. Instead we add a NULL character to all of our strings and just
+ * use UTF8ToString.
  */
 var NULL_BYTE_PADDING_LENGTH = 1;
 
@@ -297,59 +299,90 @@ Session.prototype['matches_inbound_from'] = restore_stack(function(
 Session.prototype['encrypt'] = restore_stack(function(
     plaintext
 ) {
+    var plaintext_buffer, message_buffer;
+    try {
         var random_length = session_method(
             Module['_olm_encrypt_random_length']
         )(this.ptr);
         var message_type = session_method(
             Module['_olm_encrypt_message_type']
         )(this.ptr);
-    var plaintext_array = array_from_string(plaintext);
+
+        var plaintext_length = Module['lengthBytesUTF8'](plaintext);
         var message_length = session_method(
             Module['_olm_encrypt_message_length']
-    )(this.ptr, plaintext_array.length);
+        )(this.ptr, plaintext_length);
+
         var random = random_stack(random_length);
-    var plaintext_buffer = stack(plaintext_array);
+
-    var message_buffer = stack(message_length + NULL_BYTE_PADDING_LENGTH);
+        // need to allow space for the terminator (which stringToUTF8 always
+        // writes), hence + 1.
+        plaintext_buffer = malloc(plaintext_length + 1);
+        Module['stringToUTF8'](plaintext, plaintext_buffer, plaintext_length + 1);
+
+        message_buffer = malloc(message_length + NULL_BYTE_PADDING_LENGTH);
+
         session_method(Module['_olm_encrypt'])(
             this.ptr,
-        plaintext_buffer, plaintext_array.length,
+            plaintext_buffer, plaintext_length,
             random, random_length,
             message_buffer, message_length
         );
         return {
             "type": message_type,
-        "body": Pointer_stringify(message_buffer)
+            "body": Module['UTF8ToString'](message_buffer),
         };
+    } finally {
+        if (plaintext_buffer !== undefined) {
+            free(plaintext_buffer);
+        }
+        if (message_buffer !== undefined) {
+            free(message_buffer);
+        }
+    }
 });
 
 Session.prototype['decrypt'] = restore_stack(function(
     message_type, message
 ) {
-    var message_array = array_from_string(message);
+    var message_buffer, plaintext_buffer;
-    var message_buffer = stack(message_array);
+
+    try {
+        message_buffer = malloc(message.length);
+        Module['writeAsciiToMemory'](message, message_buffer, true);
+
         var max_plaintext_length = session_method(
             Module['_olm_decrypt_max_plaintext_length']
-    )(this.ptr, message_type, message_buffer, message_array.length);
+        )(this.ptr, message_type, message_buffer, message.length);
-    // caculating the length destroys the input buffer.
+
-    // So we copy the array to a new buffer
+        // caculating the length destroys the input buffer, so we need to re-copy it.
-    var message_buffer = stack(message_array);
+        Module['writeAsciiToMemory'](message, message_buffer, true);
-    var plaintext_buffer = stack(
+
-        max_plaintext_length + NULL_BYTE_PADDING_LENGTH
+        plaintext_buffer = malloc(max_plaintext_length + NULL_BYTE_PADDING_LENGTH);
-    );
+
         var plaintext_length = session_method(Module["_olm_decrypt"])(
             this.ptr, message_type,
             message_buffer, message.length,
             plaintext_buffer, max_plaintext_length
         );
 
-    // Pointer_stringify requires a null-terminated argument (the optional
+        // UTF8ToString requires a null-terminated argument, so add the
-    // 'len' argument doesn't work for UTF-8 data).
+        // null terminator.
         Module['setValue'](
             plaintext_buffer+plaintext_length,
             0, "i8"
         );
 
-    return Pointer_stringify(plaintext_buffer);
+        return UTF8ToString(plaintext_buffer);
+    } finally {
+        if (message_buffer !== undefined) {
+            free(message_buffer);
+        }
+        if (plaintext_buffer !== undefined) {
+            free(plaintext_buffer);
+        }
+    }
+
 });
 
 function Utility() {