Author: Guy

WiFi won’t connect on Samsung Galaxy S2 with CyanogenMod 9 (ICS 4.0.4)

After upgrading to CyanogenMod 9 (ICS 4.0.4) I’ve experience problems connecting to WiFi networks. Most of the time I’ve tried to connect to a WiFi network it would try to connect and then fail. Often it would also show the network I’ve just tried to connect to as “Not in range”. This was extremely irritating, as I could stand by my router and have the phone report that there is no signal, while another Galaxy S2 phone would connect immediately, the only difference was that the other phone was running Android 2.3.7. Needless to say, I haven’t made any major (or minor) changes to my WiFi equipment and the problem wasn’t confined just to my home. Sometimes, it would connect after being idle for a day or so.

Back when I was using CyanogenMod 7, I had no problems with the WiFi on my phone, and I could also replicate this behaviour on another Galaxy S2 I’ve upgraded to CyanogenMod 9. Initially I thought it was some bug in CyanogenMod, but I came up with nothing. Over the weekend, I’ve figured maybe the bug isn’t specific to CyanogenMod, and I’ve found this bug report WiFi freeze on Samsung Galaxy S2 with ICS 4.0.3. For some reason many people have problems with WiFi on Galaxy S2 with ICS. While the report relates to the WiFi freezing, which I didn’t experience, I’ve decided to sift through the comments. Some people mentioned the “Wi-Fi frequency band” feature available in Wi-Fi settings -> Advanced (available by pressing the menu button), so I’ve decided to try playing with the different settings there.

This setting allows you to choose the WiFi operating frequency between three options 5GHz, 2.4GHz and “Auto”, which as you can guess automatically figures out the right frequency, 5GHz (802.11a and 802.11n) and 2.4GHz(802.11b/g/n). However, it seems the phone (probably due to a problem in the driver) fails the “Auto” thing. Instead of guessing the right frequency, it fails to connect. So I’ve changed it to 2.4GHz, which is still more popular choice in routers over 5GHz, and instantly my phone connected to my router.

For conclusion: If you have trouble connecting to WiFi on Samsung Galaxy S2 with ICS, you should probably set the phone to use 2GHz only (or 5GHz only) instead of the default “Auto” mode.

spass-3.0 Released

I’ve released today the new version of spass, a tool that creates cryptographically strong passwords and passphrases by generating random bits from your sound card.

In the user facing side, spass can now create passphrases as long as passwords. The words for the passphrases are chosen out of a list of 8192 words which means each word adds 13 bits of entropy to the passphrase.

spass can now use one of three audio backends (the old version could only use OSS):

  • Advanced Linux Sound Architecture (ALSA)
  • Open Sound System (OSS)
  • PortAudio

The PortAudio support will hopefully make it easy to port spass to other platforms as well (such as Windows). The random number generator got overhauled and now there is an unbiasing step before applying the hash function. This should help getting consistent results in terms of entropy. In the backstage I’ve migrated the project from autotools to cmake.

You can find more information, as well as both source and binary packages in https://github.com/guyru/spass.

Auto-Detect Dependencies when Building .debs Using CMake

CMake (via CPack) as a great feature that allows you to automatically generate Debian/Ubuntu (.deb) packages. One of the annoying things to do when you create a package is listing its dependencies. CMake asks you do it via the CPACK_DEBIAN_PACKAGE_DEPENDS variable. For example:

set (CPACK_DEBIAN_PACKAGE_DEPENDS "libc6 (>=2.7-18)")

But what happens when you work on a more complex project? Keeping track of all the dependencies by hand is a tedious task. Debian provides a tool named dpkg-shlibdeps which makes this task easier by updating the debian/control file with dependencies extracted from the dynamic libraries needed by a given executable. Luckily since CMake 2.8.3, CMake also supports running this tool automatically to figure out the required dependencies. The documentation is sparse, and I had hard time finding how to do so (I actually found it via a bug report and a commit message, but afterwards I’ve seen it the official documentation too). To enable it, you need to add the following line to your CMakeLists.txt file:

# autogenerate dependency information
set (CPACK_DEBIAN_PACKAGE_SHLIBDEPS ON)

SQL Dump for MS Access databases (.mdb files) on Linux

I recently had to work with some data that came in a huge Microsoft Access database. Because I like SQLite (and despise Access), I’ve decided to export the data to an SQLite file. The first thing I needed to do was to somehow get all the data out of the db. Being a Linux user, complicates things a bit, but thanks to mdb-tools it’s possible to process the .mdb files without resorting to Windows and buying Access. Using mdb-tools directly can be tedious if you want to export a large db with multiple tables, so when I’ve looked for a way to automate it, I came across Liberating data from Microsoft Access “.mdb” files. This post shows a nice script that dumps every table in a .mdb file to separate CSV file.

While useful, I wanted something that I could easily import into SQLite. So I’ve modified their script to generate an SQL dump of the db. Given a db file, it writes to stdout SQL statements describing the schema of the DB followed by INSERTs for each table. Actually because mdb-tools doesn’t support SQLite as a backend, the dump uses a MySQL dialect, but it should be fine with SQLite as well (SQLite will mostly ignore the parts it can’t process such as COMMENTs). The easiest way to use the script is

$ python AccessDump.py access.mdb | sqlite3 new.db

If the original db contains non-ascii characters, and isn’t encoded in UTF-8, you should set the MDB_JET3_CHARSET environment variable to the correct charset. The dump itself will be UTF-8 encoded.

$ MDB_JET3_CHARSET="cp1255" python AccessDump.py access.mdb | sqlite3 new.db

Continue reading SQL Dump for MS Access databases (.mdb files) on Linux

Conditional Compilation in Autoconf and Automake

While working on my audio based random password generator (you view the source in github), I wanted to do some conditional compilation: Compiling certain parts of the program only in case some option is passed to the configure script. As it usually happens with GNU’s autotools, it kind of hell to do it. Documentation is spread across dozens of sources, each provides only a specific part of what to do. I’m writing it here in the blog, in hope I’ll never have to search how to do so again.
Continue reading Conditional Compilation in Autoconf and Automake

Some Thoughts About Android’s Full Disk Encryption

One of the new features touted by ICS is full-disk encryption (actually it was first available in Android 3). The first look is promising. The android developers went with dm-crypt as the underlying transparent disk encryption subsystem, which is the de-facto way to perform full-disk-encryption in Linux nowadays. This ensures both portability of the encrypted file systems and tried-and-tested implementation. The cipher itself is 128-bit AES in a ESSIV mode, and the encryption key is derived from the password using PBKDF2 (actually it’s the key that encrypts the actual encryption key, allowing fast password changes). So where do I think it went wrong?

Enabling the full disk encryption.

Continue reading Some Thoughts About Android’s Full Disk Encryption

A Note About Open Sound System (OSS)

A while ago I wrote about creating random numbers out of noise gathered from audio device and also created a password generator based on the idea. The implementation was based on Open Sound System (commonly known as OSS). OSS was the defacto way to access audio device couple of years ago, when it hit licensing issues and subsequently replaced by ALSA. As Ubuntu no longer supports OSS (and even the ALSA wrapper for it is in Universe), I’ve decided to re-write the code in some modern alternative.
Continue reading A Note About Open Sound System (OSS)

Fixing virtualenv after Upgrading Your Distribution/Python

After you upgrade your python/distribution (specifically this happened to me after upgrading from Ubuntu 11.10 to 12.04), your existing virtualenv environments may stop working. This manifests itself by reporting that some modules are missing. For example when I tried to open a Django shell, it complained that urandom was missing from the os module. I guess almost any module will be broken.

Apparently, the solution is dead simple. Just re-create the virtualenv environment:

virtualenv /PATH/TO/EXISTING/ENVIRONMENT

or

virtualenv --system-site-packages /PATH/TO/EXISTING/ENVIRONMENT

(depending on how you created it in the same place). All the modules you’ve already installed should keep working as before (at least it was that way for me).

Debugging File Type (MIME) Associations

I’m having less and less time to blog and write stuff lately, so it’s a good oppertunity to catch up with old thing I did. Back in the happy days I used Gentoo, one of irritating issues I faced was messed up file type associations. MIME type for some files was recognized incorrectly, and as a result, KDE offered to open files with unsuitable applications. In order to debug it I wrote a small python script which would help me debug the way KDE applications are associated with MIME types and what MIME type is inferred form each file.

The script does so by querying the KMimeType and KMimeTypeTrader. The script does 3 things:

  • Given a MIME type, show it’s hierarchy and a list of applications associated with it.
  • Given an applications, list all MIME types it’s associated with
  • Given a file, show its MIME type (and also the accuracy, which allows one to know why that MIME type was selected, although I admit that in the two years since I wrote it, I forgot how it works :))

The script is pasted below. I hope someone that still fiddles with less than standard installations, will find it helpful.
Continue reading Debugging File Type (MIME) Associations

Installing culmus-latex on Ubuntu 11.10

After someone complained to me that he can’t install culmus-latex on Ubuntu 11.10, I decided to check the issue. Apparently culmus-latex can’t be installed as-is on Ubuntu 11.10 (and probably other new versions of Debian and Ubuntu). The problem have been reported in few places such as Whatsup, but as I don’t frequent the forum lately, I wasn’t aware of it. Skip bellow if you’re just interested in the workaround.

Technical Details

The problem manifests itself as:

sudo make install
... snipped for brevity ...
mktexlsr: Done.
updmap-sys --enable Map=culmus.map
updmap: This is updmap, version $Id: updmap 14402 2009-07-23 17:09:15Z karl $
updmap: using transcript file `/var/lib/texmf/web2c/updmap.log'
updmap: initial config file is `/var/lib/texmf/web2c/updmap.cfg'
make: *** [install] Error 2

But if you look at updmap’s manpage there is no documentation for the return codes. Also there is no explicit place where it exits with return code 2 in the code. After some straceing I found the culprit in the combination of the set -e in the top of /usr/bin/updmap and the function pickLocalFile in /usr/share/tex-common/debianize-upddmap which overrides certain behaviors in updmap. The pickLocalFile uses the following lines

localfile=""
localfile="`ls $debDirname/*local*cfg 2>/dev/null`"
if [ -n "$localfile" ]; then

To check if there is a local configuration file under /etc/texmf/updmap.d. If such file doesn’t exist, instead of creating one (as the maintainers of debianize-updmap intended) it fails due to the set -e in /usr/bin/updmap. Thus updmap exists with error code 2, instead of completing the installation.

Meanwhile, until the bug is fixed, there is a simple workaround

Workaround

Before installing, execute

sudo touch /etc/texmf/updmap.d/10local.cfg

And now the regular sudo make install installation should finish successfully.

As the problem is a result of a Debian bug, I don’t expect to release a new version of culmus-latex, instead I’ll report the bug to the Debian team.