[tor-commits] [meek/master] Fix readIntoBuf when starting with a non-empty buffer.

[dcf at torproject.org]

commit 5b51cf7d301c6f8d5fd3a939dea602c7484111ed
Author: David Fifield <david at bamsoftware.com>
Date:   Mon Sep 8 16:43:37 2014 -0700

    Fix readIntoBuf when starting with a non-empty buffer.
    
    readIntoBuf concatenates results from multiple reads until a buffer is
    filled. There was a mistake whenever the current offset was not 0: the
    second argument is an absolute index, not a length relative to the first
    argument.
    
    The affected line of code was:
    	this.buf.subarray(this.buf.length - this.bytesToRead, n).set(data)
    For example, if bytesToRead were 100, and readIntoBuf were called with
    20 bytes available, the data would be stored in the buffer as:
    	this.buf.subarray(100 - 100, 20).set(<array with length 20>)
    So far, so good. The first 20 elements of the array would be set. When
    the next read happened, say there are 80 bytes available, the call would
    be:
    	this.buf.subarray(100 - 80, 80).set(<array with length 80>)
    The code was trying to store an 80-length array in a 60-length subarray,
    and failed with
    	RangeError: invalid array length
    
    I'm pretty sure this bug was the cause of
    	"tbb bundle with meek takes (literally) hours to connect"
    	https://trac.torproject.org/projects/tor/ticket/11612
    It would be more likely to happen during initial bootstrapping, because
    that's when the client sends some large bunches of data (they can be
    about 80 KB), which are more likely to be split into two sends. I was
    able to reproduce the described error by altering meek-client to split
    its sends into two, with a 500-millisecond delay in between.
---
 firefox/components/main.js |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/firefox/components/main.js b/firefox/components/main.js
index ec98d15..1b71412 100644
--- a/firefox/components/main.js
+++ b/firefox/components/main.js
@@ -340,7 +340,7 @@ MeekHTTPHelper.RequestReader.prototype = {
     readIntoBuf: function(input) {
         var n = Math.min(input.available(), this.bytesToRead);
         var data = input.readByteArray(n);
-        this.buf.subarray(this.buf.length - this.bytesToRead, n).set(data)
+        this.buf.subarray(this.buf.length - this.bytesToRead).set(data);
         this.bytesToRead -= n;
     },