Life Of Navin

Random Musings, Random Bullshit.

kc

Google Authenticator 2FA on Mac OS with oathtool

Multi-factor authentication (Commonly 2FA) is a security godsend. You really should enable it on every account you have that supports it. I usually use Google Authenticator for time-variant OTP systems. However, I find it irritating to have to reach for my phone to check for the OTP every time I log in to a site. Why do I find it irritating? Because of 2 reasons:
  1. I actually have to get to my physical device, which I usually don't carry around with me. 
    • In office, I usually keep my phone away from me to avoid distraction/unwanted calls/notifications.
  2. Even after I open up Authenticator, I have to type out the digits from screen to screen. 
    • I know there are other alternatives, but Google Authenticator is most widely supported across services I use daily: AWS, Okta, Google Suite, Pager etc. and it's not going away soon.
I always wondered if there is an easier way to get the added security of 2FA, with more flexibility. And the solution was to simply use 2FA from my laptop itself. So I came up with a workflow. This is my current workflow on Mac OS Sierra (but should work on any Mac).

Step 1: Generate 2FA tokens on laptop
This turned out to be simpler than I imagined. I simply needed to use the awesome oath-toolkit, which basically behaves like Google Authenticator for the laptop. It can be used to easily generate time-variant one time passwords, which is what GA does! Setting it up is a breeze:

$ brew install oath-toolkit
$ oathtool --totp -b "your_key_here" | pbcopy

The key you use here is a key generated when you set up OTP (You probably remember scanning a QR code). If you don't have the key saved locally, you will have to do a one-time reset of your 2FA to generate a new key.

We pipe the generated token to pbcopy to copy it to clipboard. This allows us to generate totp tokens and have them ready to be pasted when needed. No need to look for your mobile phone for OTP anymore!

Step 2: Smoother Workflow
Now that we can generate OTP tokens without a phone, let's clean up the process. Currently, we need to go to the terminal every time we want to generate a new token. What if we could bind this to a global key command instead? Mac OS has an awful global keyboard macro system (Yay Linux as always), but it can still be done. This is how I do it:
  • Install ICanHazShortcut, a nifty Mac app for global hotkeys. It's not too fancy, but delivers what it promises!
  • Set up an Automator service to simply paste clipboard contents when called:
    • Go to Applications -> Automator -> New -> Service
    • Service receives "no input" in "any application"
    • Drag the "Run Applescript" action to the right and fill in the following and then save the workflow as paste-from-clipboard. You can save it in your home directory:

  • Finally, bring it all together! Set up keyboard shortcuts in ICanHazShortcut, and set the command to run as:  
/usr/local/bin/oathtool --totp -b "your_key_here" | pbcopy | automator ~/paste-from-clipboard.workflow/
Here I assume that the workflow you created was named paste-from-clipboard and saved in your home directory. You may not need to specify the full path for oathtool, but I had to.

And that's it! Now whenever you're on a page that needs a 2FA token, simply type in your keyboard shortcut, and your token will be filled in!

...And the love kickstarts again ;)

PS: Yes, this is unsafe because if someone get's physical access to your system, then he can access your 2FA key and generate tokens, thereby rendering your 2FA useless. Then again, if he has physical access to your system, then this is just one of a million ways to get access to your data, so the attack vector surface increase is not as prominent. Of course, if you're uber concerned about security, skip this. But if you want a compromise between security and usability then this is a decent solution! :)

Debugging Running JVM Without Restart

Debugging a process actively running on a JVM without restarting the application and setting up flags and attaching a debugger is a a bit of a pain. However, there's quite a bit you can do to debug a running process without needing a JVM restart.

This. But with less enthusiasm. Much less enthusiasm.
Here's a quick walkthrough, with the associated commands. I'm simply compiling the steps to allow a single lookup for everyone else who has to walk down this road.
  • Ensure that it is the JVM which is consuming too many resources. A combination of free and sorting ps output should do the trick.  free tells us current memory consumption, while ps gives us process level statistics
$ free -m
                            total        used   free   shared   buffers   cached
  Mem:               15040    13956  1083      0          84         890
  -/+ buffers/cache: 12980 2059
  Swap:                  0            0        0

$ ps -eo pmem,pcpu,vsize,pid,cmd | sort -k 1 -nr | head -5 

69.8  67.5 8180544 24204 java -Duser.dir=[...]
  7.5   5.6 1550956 4866 python /mnt/manage.py run_gunicorn -c /mnt/conf.py
  7.4   6.3 1542356 4848 python /mnt/manage.py run_gunicorn -c /mnt/conf.py
  7.4   6.0 1548132 4863 python /mnt/manage.py run_gunicorn -c /mnt/conf.py
  7.4   5.8 1537104 4869 python /mnt/manage.py run_gunicorn -c /mnt/conf.py

Wow, so we seem to have barely a GB of memory free and a resource hog java process and a bunch of gunicorn processes. Let's take a look at the Java process shall we? The pid is 24204 (highlighted in previous command)
  • Let's find thread utilization of resources. ps to the rescue again!
$ ps -mo 'pid lwp stime time pcpu' -p 24204
        PID   LWP   STIME   TIME   %CPU
    24204       -      16:12   00:32:41   17.4
          -   24204   16:12   00:00:00   0.0
          -   24255   16:12   00:00:03   0.0
          -   24256   16:12   00:01:11   0.6
          -   24257   16:12   00:01:11   0.6
          -   24258   16:12   00:01:11   0.6
          -   24259   16:12   00:01:11   0.6
          -   24260   16:12   00:06:34  33.5
          -   24261   16:12   00:00:11   0.0
          -   24262   16:12   00:00:00   0.0
          -   24263   16:12   00:00:00   0.0
          -   24264   16:12   00:00:00   0.0
          -   24265   16:12   00:00:00   0.0
          -   24266   16:12   00:00:43   0.3
Interesting. It looks like a single issue here. How do we trace this? Why, we take a couple of thread dumps of course! We use jstack for this. jstack simply produces a thread dump of the given process.

jstack 24204 > 1.dump
jstack 24204 > 2.dump
jstack 24204 > 3.dump

I usually take multiple jstacks just for further analysis. You may also need to run jstack as sudo as sudo -u user jstack <pid>

  • Now we have the thread dump and the misbehaving thread, so we can check what that thread is doing. Since thread id in the previous command (24260) is a decimal, we first convert it into hex because thread dumps use hex ids. To do this we simply use bc to convert the number, and then tr to transform the uppercase into lowercase. 
$ echo "obase=16; 24260" | bc | tr '[:upper:]' '[:lower:]'
5ec4  # this is the thread id in hex

$ vim 1.dump # Now search for the thread hex in the dump file
[...]
"Concurrent Mark-Sweep GC Thread" os_prio=0 tid=0x00007fea2c083000 nid=0x5ec4 runnable
[...]
So it turns out in this specific case that the GC is taking up a massive number of CPU cycles. The solutions for this are numerous, and may vary depending on what your constraints are. The other issues may be related to database access, I/O access, or, quite frankly, a million other reasons relating to badly written code.

To be honest, this method of debugging does have it's constraints, but can be a godsend when you need to quickly validate your thinking when it comes to resource hog bugs. And of course, you can celebrate by posting memes on slack!

At Bloomreach, we prefer :patre: #insidejoke
Hope this is helpful! Until the next b̶u̶g̶ feature...  :D

PS: Yes, I know the first couple of steps can be done using htop as well, using htop in thread view. I just find ps so much more convenient


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Prologue

Finally after all these years, here's to the beginning of what was there, what is there and hopefully what will remain!! So here are my thoughts & words -Online!!