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"Invalid HTTP Request Headers" in Firefox
Date: 9/1/2015
Tags: firefox
For most of 2014 I've been using Firefox because I feel it's doing a better job of looking after my privacy. However it's not without it's cost. For instance today I found some pretty quirky behaviour in the Mac build of Firefox v34.0.5:



Basically on this site it's dropping the leading "G" of the "GET" request. To make matters worse the problem is intermittent. I can reproduce with a clear cache. Internally Firebug is reporting the correct packet, but Wireshark shows the missing byte.
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Scripting Debugger
Date: 16/12/2014
Tags: scribe scripting


And extern library function support!
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Portable OpenSSL on Mac OS X
Date: 12/12/2014
Tags: dylib openssl
So it's been brought to my attention that Scribe's self install of OpenSSL on Mac doesn't actually work in v2.0.x, so the last week I've been looking into what it takes to do that.

The main issue is that load paths, are by default, absolute and hardcoded. Which works against you when you want a portable install of something. Secondly the OpenSSL .dylib is made of 2 libraries; libssl and libcrypt. And when you dlopen the first (libssl) the system needs to be able to find libcrypt. The link is embedded in the Mach-O image as a LC_LOAD_DYLIB segment. You can see that by issue the command:
otool -l ./libssl.1.0.0.dylib
Part of the output you'll get:
    cmd LC_LOAD_DYLIB
cmdsize 64
   name /usr/lib/libcrypto.1.0.0.dylib (offset 24)
   time stamp 2 Thu Jan  1 10:00:02 1970
That absolute path is what is causing the dlopen of libssl to fail. So we need to fix that. And the tool to do it 'install_name_tool', which is provided from Apple. Now I had two problems. Firstly what do you change the path to? And how do you actually get the tool to change the path?

Firstly Apple has several ways of locating shared libraries:
  1. @executable_path : relative to the main executable
  2. @loader_path : relative to the referring binary
  3. @rpath : relative to any of a list of paths.
What I wanted is the path to be relative to the executable, so I want:
@executable_path/libcrypto.1.0.0.dylib

But how to call install_name_tool to actually do that? Well to start with I tried:
install_name_tool -change /usr/lib/libcrypto.1.0.0.dylib @executable_path/libcrypto.1.0.0.dylib ./libssl.1.0.0.dylib
Which is actually the right command. But because the new string is longer than the old string the command fails (silently I might add). The trick to getting it to work is to add the linker command:
-Wl,-headerpad_max_install_names
to the CFLAG variable in the OpenSSL root Makefile. This causes the load segments to have extra padding bytes so that you can change the paths as much as you want later. Now after rebuilding the OpenSSL dylibs you can reissue the install_name_tool command and the link path changes:
MacOS matthew$ otool -l ./libssl.1.0.0.dylib
...
    cmd LC_LOAD_DYLIB
cmdsize 64
   name @executable_path/libcrypto.1.0.0.dylib (offset 24)
...
Then I could dlopen 'libssl.1.0.0.dylib' and it would pull in the right libcrypt file (both as sitting in the same folder as the executable).

I'm putting this here so I don't forget how to do this next time. Ha.
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Calling Msys and MingW commands from outsite their environment (i.e. CreateProcess)
Date: 16/11/2014
Tags: mingw
So I wanted to check in on how Lgi apps built on Msys / MingW these days, particularly to have a look at implementing a GDB wrapper in the LgiIde application so that I can debug stuff directly in Linux without having to drop down to the command line. But never mind that convoluted explanation.

The problem that I initially saw when trying to call Msys's 'make' was this:
0 [main] make.exe" 4408 fhandler_base::dup: dup(some disk file) failed, handle 0, Win32 error 6
/bin/sh: line 1: /c/Code/Lgi/trunk/LgiIde/C:/MinGW/msys/1.0/bin/make.exe: No such file or directory
Then after I started using a different CreateProcess wrapper I got this:
-f: Nothing to be done for `Makefile.windows'.
I checked and re-checked that the path pointed to both the Msys and MingW bin directories in make's environment. But it still wouldn't work. From the command line it was fine, but doing a CreateProcess on make failed.

It would appear that Msys make really needs to be run inside a shell of some sort. Even if it's just windows build in cmd.exe. So I ended up with code that looks like this:
CreateProcess("C:\\Windows\\System32\\cmd.exe", "/C make.exe -f Makefile.windows", ...);
Which works well enough for me.
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The Abomination Of Wingdings And The Shortfalls Of Outlook
Date: 24/3/2014
Tags: email charsets Outlook
It's fairly well accepted that the font WingDings should not be used in webpages. Many modern cross platform browsers don't even support it. One of the reasons is that supporting WingDings means supporting creating symbol fonts which requires adding the SYMBOL_CHARSET define to the call to CreateFont instead of the normal ANSI_CHARSET. Due to their cross platform nature they want as much code as possible to be the same regardless of platform. So instances like this where a Windows specific font needs some special handling are often unimplemented to keep things simple. It may even be a strategic design decision made to deliberately weaken the support for it hoping that it's usage would fade away.

In my email client I have two places that I have to special case code just for WingDings. Firstly the above mentioned CreateFont call needs a special flag added so that when rendering HTML email that uses WingDings the correct glyphs are placed on the screen/page. The second place is during conversion from HTML to (unicode) text. Of course the actual bytes to render in the HTML in the document are not unicode or some easily known charset, so you have to convert from "WingDingsCharset" to Unicode using some hacked together table.

Now the question is "Who is creating all this content that uses the WingDings font?"

That's an excellent question dear reader, and the answer is: Outlook. In 2014 Outlook still happily converts:
:)
Into a WingDings HTML font tag containing a single uppercase 'J'. That will be rendered as a smiley face by Outlook and a capital J by most other software. Especially software on Macs and Linux that don't have access to that font by default. Never mind that Unicode has a perfectly functional smiley face character (☺) which could be rendered correctly by pretty much any software these days.

Outlook's character set issues don't stop there though. Take the case that I ran into recently where Outlook was used to send an email containing a URL that included a Unicode character. Now that in itself is somewhat dubious and indeed the URL referred to a Microsoft content server that should've known better than to allow a unicode character in the URL (especially when a perfectly suitable ascii character was available). Now that Unicode URL was specified used proper HTML entity encoding, however the meta charset of the HTML aaaaand the Content-Type of the MIME segment both stated the document was in us-ascii. And well, that Unicode character got converted to garbage at some point. Instead Outlook should make the charset of the HTML "utf-8" or something so that the character can exist in the specified charset. I've taken the approach of assuming the attributes of tags like 'src' and 'href' are in unicode despite the prevailing HTML charset.

Another aspect of the poor charset implementation in Outlook is the tendency to use undefined characters in the specified charset. Take for instance an Outlook generated email says it's using the ISO-8859-1 charset and then goes on to use characters in the 0x80 to 0x9F address space which is according to ISO-8859-1, undefined. Internally Outlook is using the Windows-1252 charset, which DOES define characters in that range. However instead of marking the email as "Windows-1252" it puts the incorrect ISO-8859-1 charset in the headers (they are essentially the same outside of that range). This commonly manifests as smart quotes (0x91 and 0x92) getting rendered incorrectly. Scribe of course has the ability to let the user override the charset which fixes the problem.

Now I'm in no way saying Scribe is perfect and lets all bash on Outlook. But I feel these bugs have been there for over 10 years and still haven't been addressed and something needs to be said. I doubt they will ever fix their software. Which is sad, because it makes the rest of the email software community look bad when we have to deal with the broken emails coming out of Outlook. I try and take a very literal interpretation of the incoming data. So that the user sees the content warts and all. I'm not a fan of sweeping bugs in other clients under my carpet. That has had a very poor history in the web-browser world. Ending in content bugs lasting far longer than they should have.

And if this ever gets back to someone working on the Outlook team: fix thy bugs. It's not even hard... these are really basic problems and it would most likely take a day or less to address.
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Very high Windows 7 idle hard disk utilization
Date: 15/3/2014
For months now I've noticed that when I leave my Windows 7 machine alone for over 30 minutes the hard disk starts grinding away relentlessly. Of course if you go to investigate what it's doing all activity ceases immediately. Preventing you from finding out exactly what is going on.

I had these thoughts of possible malware or a virus infection cross my mind and so downloaded and ran Process Monitor and then left the machine sit for 50 minutes. When I came back to it sure enough the hard disk was grinding away. But now I've been logging the activity! So what's the secret process using so much disk I/O?
9:49:49.6359004 PM	MsMpEng.exe	948	ReadFile	
9:49:49.6465209 PM	MsMpEng.exe	948	ReadFile	
9:49:49.6465457 PM	MsMpEng.exe	948	ReadFile	
9:49:49.6540933 PM	MsMpEng.exe	948	ReadFile	
9:49:49.6541138 PM	MsMpEng.exe	948	ReadFile	
9:49:49.6577645 PM	MsMpEng.exe	948	ReadFile	
9:49:49.6600897 PM	MsMpEng.exe	948	ReadFile	
Oh just Microsoft's anti-malware service checking all my files. "Alright... everything seems to be in order here... as you were".
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