Scaffolding for fetching and parsing emails from IMAP with Python

A friend asked me if I could help him write a Python script for fetching and processing data from emails in his mailbox … Well, the thing with emails is that they’re a pain to work with (in any form). So, I tried to help him out with a little scaffolding (also available as a Gist).

Strings at Facebook

It’s great to see how the simplest things we take for granted are engineered and improved. Case in point: Facebook’s std::string replacement.

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https://www.youtube.com/watch?v=kPR8h4-qZdk

Ubuntu on Windows

I didn’t see that coming … I still remember a time where this was UNTHINKABLE!!! ?

Backup And Restore Your Android Phone With ADB (And rsync)

Based on my previous scripts and inspired by two blog posts that I stumbled upon I tackled the “backup all my apps, settings and data” problem for my Android devices again. The “new” solutions both use rsync instead of adb pull for file transfers. They both use ADB to start a rsync daemon on the device, forward its ports to localhost and run rsync against it from your host.

Simon’s solution assumes your phone has rsync already (e.g. because you run CyanogenMod) and can become root via adb root . It clones all files from the phone (minus /dev , /sys , /proc etc.). He also configures udev to start the backup automatically when the phone is plugged in.

pts solves the setup without necessarily becoming root. He also has a way of providing a rsync binary to phones that don’t have any (e.g. when running OxygenOS). He also has a few tricks on how to debug the rsync daemon setup on the phone.

I’ve tried to combine both methods. My approach doesn’t require adb or rsync to be run as root. It’ll use the the system’s rsync when available or temporarily upload and use a backup one extracted from Cyanogen OS (for my OnePlus One). Android won’t allow you to chmod +x a file uploaded to /sdcard , but in /data/local/tmp it works. ?

The scripts will currently only backup and restore all of your /sdcard directory. Assuming you’re also using something like Titanium Backup you’ll be able to backup and restore all your apps, settings and data. To reduce the amount of data to copy it uses rsync filters to exclude caches and other files that you definitely don’t want synced ( .DS_Store files anyone?).

At the moment there’s one caveat: I had to disable restoring modification times (i.e. use --no-times ) because of an obnoxious error (they will be backuped fine, only restoring is the problem): ?

mkstemp “…” (in root) failed: Operation not permitted (1)

Additionally if you’re on the paranoid side you can also build your own rsync for Android to use as the backup binary.

The code and a ton of documentation can be found on GitHub. Comments and suggestions are welcome. ?

Build Rsync for Android Yourself

To build rsync for Android you’ll need to have the Android NDK installed already.

Then clone the rsync for android source (e.g. from ~~CyanogenMod~~ LineageOS) …

git clone https://github.com/LineageOS/android_external_rsync.git
cd android_external_rsync
# checkout the most recent branch
git checkout cm-14.1

git clone https://github.com/LineageOS/android_external_rsync.git

cd android_external_rsync

# checkout the most recent branch

git checkout cm-14.1

… create the missing
jni/Application.mk
build file (e.g. from this Gist) and adapt it to your case …

… and start the build with

export NDK_PROJECT_PATH=<code>pwd</code> ndk-build -d rsync

1	export NDK_PROJECT_PATH=<code>pwd</code> ndk-build -d rsync

You’ll find your self-build rsync in
obj/local/*/rsync
. ?

Update 2017-10-06:

Updated sources from CyanogenMod to LineageOS.
Added links to Gist and Andoid NDK docs
Updated steps to work with up-to-date setups

If you get something like the following warnings and errors …

[...]
./flist.c:454:16: warning: implicit declaration of function 'major' is invalid in C99
      [-Wimplicit-function-declaration]
                        if ((uint32)major(rdev) == rdev_major)
                                    ^
./flist.c:458:41: warning: implicit declaration of function 'minor' is invalid in C99
      [-Wimplicit-function-declaration]
                        if (protocol_version < 30 && (uint32)minor(rdev) <= 0xFFu)
                                                             ^
./flist.c:467:11: warning: implicit declaration of function 'makedev' is invalid in C99
      [-Wimplicit-function-declaration]
                        rdev = MAKEDEV(major(rdev), 0);
                               ^
./rsync.h:446:36: note: expanded from macro 'MAKEDEV'
#define MAKEDEV(devmajor,devminor) makedev(devmajor,devminor)
                                   ^
3 warnings generated.
[...]
./flist.c:473: error: undefined reference to 'makedev'
./flist.c:454: error: undefined reference to 'major'
./flist.c:457: error: undefined reference to 'major'
./flist.c:458: error: undefined reference to 'minor'
./flist.c:467: error: undefined reference to 'major'
./flist.c:467: error: undefined reference to 'makedev'
./flist.c:617: error: undefined reference to 'major'
./flist.c:619: error: undefined reference to 'minor'
./flist.c:621: error: undefined reference to 'minor'
./flist.c:788: error: undefined reference to 'makedev'
./flist.c:869: error: undefined reference to 'makedev'
./flist.c:1027: error: undefined reference to 'minor'
clang++: error: linker command failed with exit code 1 (use -v to see invocation) 
make: *** [obj/local/armeabi-v7a/rsync] Error 1

[...]

./flist.c:454:16: warning: implicit declaration of function 'major' is invalid in C99

[-Wimplicit-function-declaration]

if ((uint32)major(rdev) == rdev_major)

./flist.c:458:41: warning: implicit declaration of function 'minor' is invalid in C99

[-Wimplicit-function-declaration]

if (protocol_version < 30 && (uint32)minor(rdev) <= 0xFFu)

./flist.c:467:11: warning: implicit declaration of function 'makedev' is invalid in C99

[-Wimplicit-function-declaration]

rdev = MAKEDEV(major(rdev), 0);

./rsync.h:446:36: note: expanded from macro 'MAKEDEV'

#define MAKEDEV(devmajor,devminor) makedev(devmajor,devminor)

3 warnings generated.

[...]

./flist.c:473: error: undefined reference to 'makedev'

./flist.c:454: error: undefined reference to 'major'

./flist.c:457: error: undefined reference to 'major'

./flist.c:458: error: undefined reference to 'minor'

./flist.c:467: error: undefined reference to 'major'

./flist.c:467: error: undefined reference to 'makedev'

./flist.c:617: error: undefined reference to 'major'

./flist.c:619: error: undefined reference to 'minor'

./flist.c:621: error: undefined reference to 'minor'

./flist.c:788: error: undefined reference to 'makedev'

./flist.c:869: error: undefined reference to 'makedev'

./flist.c:1027: error: undefined reference to 'minor'

clang++: error: linker command failed with exit code 1 (use -v to see invocation)

make: *** [obj/local/armeabi-v7a/rsync] Error 1

… you probably need to update
config.h
and change
/* #undef MAJOR_IN_SYSMACROS */
to
#define MAJOR_IN_SYSMACROS 1
.

CFSSL FTW

After reading how CloudFlare handles their PKI and that LetsEncrypt will use it I wanted to give CFSSL a shot.

Reading the project’s documentation doesn’t really help in building your own CA, but searching the Internet I found Fernando Barillas’ blog explaining how to create your own root certificate and how to create intermediate certificates from this.

I took it a step further I wrote a script generating new certificates for several services with different intermediates and possibly different configurations (e.g. depending on your distro and services certain cyphers (e.g. using ECC) may not be supported).
I also streamlined generating service specific key, cert and chain files. 😀

Have a look at the full Gist or just the most interesting part:

You’ll still have to deploy them yourself.

Update 2016-10-04:
Fixed some issues with this Gist.

Fixed a bug where intermediate CA certificates weren’t marked as CAs any more
Updated the example CSRs and the script so it can now be run without errors

Update 2017-10-08:

Cleaned up renew-certs.sh by extracting functions for generating root CA, intermediate CA and service keys.

A Service Monitor built with Polymer

I tried to build a service monitor having the following features:

showing the reachability of HTTP servers
plotting the amount of messages in a specific RabbitMQ queue
plotting the amount of queues with specific prefixes
showing the status of RabbitMQ queues i.e. how many messages are in there? are there any consumers? are they hung?
showing the availability of certain Redis clients

Well, you can find the result on GitHub.
It uses two things I published before: polymer-flot and flot-sparklines. 😀

An example dashboard:

Flot Sparklines with Polymer

After wrapping Flot for Polymer I needed an element that would present a sparklines style graph.
I made one and put it into a Gist along with a demo on how to use it.

Sparkline with thresholds and pop-up on hover

Flot in Polymer

I was playing with Polymer at work, building a service monitor with it. At some point I needed charts and Flot seemed to be the simplest solution.

So after a little work I managed to wrap Flot for Polymer (on GitHub). ?

Making RabbitMQ Recover from (a)Mnesia

In the company I work for we’re using RabbitMQ to offload non-timecritical processing of tasks. To be able to recover in case RabbitMQ goes down our queues are durable and all our messages are marked as persistent. We generally have a very low number of messages in flight at any moment in time. There’s just one queue with a decent amount of them: the “failed messages” dump.

The Problem

It so happens that after a botched update to the most recent version of RabbitMQ (3.5.3 at the time) our admins had to nuke the server and install it from scratch. They had made a backup of RabbitMQ’s Mnesia database and I was tasked to recover the messages from it.
This is the story of how I did it.

Since our RabbitMQ was configured to persist all the messages this should be generally possible. Surely I wouldn’t be the first one to attempt this. ?

Looking through the Internet it seems there’s no way of ex/importing a node’s configuration if it’s not running. I couldn’t find any documentation on how to import a Mnesia backup into a new node or extract data from it into a usable form. ?

The Idea

My idea was to setup a virtual machine (running Debian Wheezy) with RabbitMQ and then to somehow make it read/recover and run the broken server’s database.

In the following you’ll see the following placeholders:

RABBITMQ_MNESIA_BASE will be /var/lib/rabbitmq/mnesia on Debian (see RabbitMQ’S file locations)
RABBITMQ_MNESIA_DIR is just $RABBITMQ_MNESIA_BASE/$RABBITMQ_NODENAME
BROKEN_NODENAME the $RABBITMQ_NODENAME of the broken server we have backups from
BROKEN_HOST the hostname of said server

One more thing before we start: if I say “fix permissions” below I mean

sudo chown -R rabbitmq:rabbitmq $RABBITMQ_MNESIA_DIR

1	sudo chown -R rabbitmq:rabbitmq $RABBITMQ_MNESIA_DIR

1st Try

My first try was to just copy the broken node’s Mnesia files to the VM’s $RABBITMQ_MNESIA_DIR failed. The files contained node names that RabbitMQ tried to reach but were unreachable from the VM.

Error description:
   {could_not_start,rabbit,
       {{failed_to_cluster_with,
            ['$BROKEN_NODENAME'],
            "Mnesia could not connect to any nodes."},
        {rabbit,start,[normal,[]]}}}

Error description:

{could_not_start,rabbit,

{{failed_to_cluster_with,

['$BROKEN_NODENAME'],

"Mnesia could not connect to any nodes."},

{rabbit,start,[normal,[]]}}}

So I tried to be a little bit more picky on what I copied.

First I had to reset $RABBITMQ_MNESIA_DIR by deleting it and have RabbitMQ recreate it. (I needed to do this way too many times ?)

sudo service rabbitmq-server stop
rm -r $RABBITMQ_MNESIA_DIR
sudo service rabbitmq-server start

sudo service rabbitmq-server stop

rm -r $RABBITMQ_MNESIA_DIR

sudo service rabbitmq-server start

Stopping RabbitMQ I tried to feed it the broken server’s data in piecemeal fashion. This time I only copied the rabbit_*.[DCD,DCL] and restarted RabbitMQ.

RabbitMQ Management Interface lists all the queues, but the node it thinks they're on is "down" — RabbitMQ’s management interface lists all the queues, but it thinks the node they’re on is “down”

Looking at the web management interface there were all the queues we were missing, but they were “down” and clicking on them told you

The object you clicked on was not found; it may have been deleted on the server.

Copying any more data didn’t solve the issue. So this was a dead end. ?

2nd Try

So I thought why doesn’t the RabbitMQ in the VM pretend to be the exact same node as on the broken server?

So I created a /etc/rabbitmq/rabbitmq-env.conf with NODENAME=$BROKEN_NODENAME in there.

I copied the backup to $RABBITMQ_MNESIA_DIR (now with the new node name) and fixed the permissions.

Now starting RabbitMQ failed with

ERROR: epmd error for host $BROKEN_HOST: nxdomain (non-existing domain)

1	ERROR: epmd error for host $BROKEN_HOST: nxdomain (non-existing domain)

I edited /etc/hosts to add $BROKEN_HOST to the list of names that resolve to 127.0.0.1.

Now restarting RabbitMQ failed with yet another error:

Error description:
   {could_not_start,rabbit,
       {{schema_integrity_check_failed,
            [{table_attributes_mismatch,rabbit_queue,
                 [name,durable,auto_delete,exclusive_owner,arguments,pid,
                  slave_pids,sync_slave_pids,recoverable_slaves,policy,
                  gm_pids,decorators,state],
                 [name,durable,auto_delete,exclusive_owner,arguments,pid,
                  slave_pids,sync_slave_pids,mirror_nodes,policy]}]},
        {rabbit,start,[normal,[]]}}}

Error description:

{could_not_start,rabbit,

{{schema_integrity_check_failed,

[{table_attributes_mismatch,rabbit_queue,

[name,durable,auto_delete,exclusive_owner,arguments,pid,

slave_pids,sync_slave_pids,recoverable_slaves,policy,

gm_pids,decorators,state],

[name,durable,auto_delete,exclusive_owner,arguments,pid,

slave_pids,sync_slave_pids,mirror_nodes,policy]}]},

{rabbit,start,[normal,[]]}}}

Now what? Why don’t I try to give it the Mnesia files piece by piece again?

Reset $RABBITMQ_MNESIA_DIR
Stop RabbitMQ
Copy rabbit_* files in again and fix their permissions
Start RabbitMQ

All our queues were back and all their configuration seemed OK as well. But we still didn’t have our messages back yet.

RabbitMQ Data Recovery Screen Shot 2 - Node Up, Queues Empty — The queues have been restored, but they have no messages in them

Solution

So I tried to copy more and more files over from the backup repeating the above steps. I finally reached my goal after copying rabbit_* , msg_store_* , queues and recovery.dets. Fixing their permissions and starting RabbitMQ it had all the queues restored with all the messages in them. ?

RabbitMQ Data Recovery Screen Shot 3 - Messages Restored — Queues and messages restored

Now I could use ordinary methods to extract all the messages. Dumping all the messages and examining them they looked OK. Publishing the recovered messages to the new server I was pretty euphoric. ?