Wandering Thoughts archives

Apple joins the webmail hall of shame

Selected headers of a just-received advance fee fraud:

Received: from smtpout.mac.com
  ([17.250.248.89])
  by <redacted> ...
Received: from mac.com
  (webmail11-en1 [10.13.10.117])
  by ...;
  Sat, 8 Apr 2006 03:01:49 -0700 (PDT)
From: JOHAN CAMPHER <johancampher4@mac.com>
To:   JOHAN CAMPHER <johancampher4@mac.com>
Subject: I AWAIT YOUR RESPONSE
X-Originating-IP: 80.89.179.237/instID=151

80.89.179.237 has been listed as part of SBL32972 for being a source of advance fee fraud since November 26th, 2005. Yet Apple is still perfectly willing to help it spam us, for whatever reason.

I don't have much to say that I didn't already say when Demon Internet joined the webmail hall of shame, so I'll just refer people to that entry.

(I'm not sure if Apple's .Mac stuff offers genuinely free webmail, but their FAQ says that they have at least a 60 day free trial. And when they call a machine webmail11-en1, I take them at their word.)

A common socket programming mistake: not handling short IO

With normal file IO, when you do do 'read(fd, buf, len)' you'll almost always get back len bytes unless you hit EOF or a disk IO error. This breeds a certain sloppyness when filling buffers; an awful lot of code effectively ignores the return value of read() except to check it for errors.

This can and will bite you on the rear when writing socket code, because networks only give you so much data at once. Short reads are routine for socket IO; you can't assume that you can get all of what you want in a single read.

The mistake is especially pernicious because the mistaken code almost always works. Usually the lines or transactions you're reading from the network are small; usually you test on a fast local network. Speaking from personal experience, it's easy to forget this and then not notice.

(Today's case was some of my code that assumed it could read all of a HTTP POST body in one read().)

Whether or not a normal (blocking) write() has similar issues is probably system dependent. Linux seems to only return from a socket write() once all data has been pushed out, but I don't know what other systems do in practice.

(According to the Single Unix Specification page for write(), in theory you can count on this behavior on any SuS compliant system.)