croc – another file transfer method

I have lost count of the number of times I have had to send a large file to someone at work, usually in a hurry. I’ve used Dropbox, ownCloud, Firefox Send (no longer available) etc. Transferring large files became a bit easier when e-mail service providers increased the size limit for attachments, but that is still not a solution for very large files. The xkcd cartoon FILE TRANSFER sums up the situation nicely.

I recently discovered the command line utility croc, which the author claims is a way to ‘easily and securely transfer stuff from one computer to another.’ I thought I’d give it a try, if only to have another tool to fall back on in an emergency. It does rely on both ends having croc installed, but hopefully that should not be a show-stopper as croc is available for Linux, Windows, macOS and BSD. To quote the author:

croc differs from a utility like scp because it doesn’t require any two computers to have enabled port-forwarding. Instead, croc will uses a relay – a temporary server setup locally (if both computers are on lan) or publicly (default is at croc4.schollz.com). Any two computers can connect to the relay, and after securing their channel with PAKE [password authenticated key exchange], they can transfer encrypted metadata and data through the relay. The relay works by first having the computers communicate the PAKE protocol via websockets, and then exchanging encrypted metadata, and then stapling the TCP connections directly so that they can transfer directly.

So, to use croc you will be dependent on the public relay provided by the author unless you set up your own relay (instructions are provided in the author’s original 2018 blog post introducing croc – see link above – and in various third-party articles about croc, such as ‘Securely Transfer Files and Folders Between Computers Using Croc‘ and ‘Transfer Files And Folders Between Computers With Croc‘).

Anyway, I installed croc in Lubuntu and Gentoo Linux from the author’s GitHub repository and indeed it is easy to use and works fine. The binary releases for the various OSs and Linux distributions can be found on the Releases page of the GitHub repository or via the OS package manager.

Lubuntu 20.10:

user $ wget https://github.com/schollz/croc/releases/download/v9.1.6/croc_9.1.6_Linux-64bit.deb
user $ sudo dpkg -i croc_9.1.6_Linux-64bit.deb

Gentoo Linux:

root # emerge net-misc/croc

(Note that croc ebuilds are not currently marked as Stable in the Gentoo Linux Portage tree, so you’ll have to unmask them by keyword if you are using the Stable branch.)

Termux:

I even installed croc in Termux on my Samsung Galaxy Note 20 Ultra 5G, and it works in Android too:

$ pkg install croc

Other OSs and other Linux distributions:

See the instructions in the README file online.

Using croc

Using croc is as simple as entering a command on one computer, informing (via e-mail, telephone, SMS, Signal or other social media) the person using the other computer of the command to use, and entering that command on the other computer. For example:

Sender

user $ croc send Documents/flight-times.ods
Sending 'flight-times.ods' (16.6 kB)
Code is: 8878-salary-courage-roger
On the other computer run

croc 8878-salary-courage-roger

Receiver

user $ croc 8878-salary-courage-roger
Accept 'flight-times.ods' (16.6 kB)? (Y/n) 

If the receiving user then enters ‘Y’, the sending user sees something similar to this:

user $ croc send Documents/flight-times.ods
Sending 'flight-times.ods' (16.6 kB)
Code is: 8878-salary-courage-roger
On the other computer run

croc 8878-salary-courage-roger

Sending (->192.168.1.74:60740)
 100% |████████████████████| (17/17 kB, 10.918 MB/s)
user $ 

and the receiving user sees something similar to this:

user $ croc 8878-salary-courage-roger
Accept 'flight-times.ods' (16.6 kB)? (Y/n) Y

Receiving (<-[::1]:39442)
 100% |████████████████████| (17/17 kB, 3.989 MB/s)
user $ 

The observant reader will notice that the above example shows a file being transferred on the same computer. When transferred between different computers the IP addresses of each computer will be displayed instead. I have used croc to transfer files between different computers on my home network (I would normally just use my NAS for this, though), between remote computers on the Internet, and between my computers and my phone via mobile broadband, and croc works in all cases.

I have not mentioned all croc’s features. I’ll leave you to read up on croc in more detail in the links I’ve given above. It looks like it might be a useful tool to have installed.

Advertisement

Using adb tools in Linux to remove bloatware from my Samsung Galaxy Note 20 Ultra

Samsung included a lot of bloatware on my Galaxy Note 20 Ultra 5G, and it is not possible to uninstall it using Play Store. However, it is possible to remove this stuff using adb tools. I got rid of the bloatware I don’t want very easily using the Linux version of the adb tools.

I have never had a Facebook account and never will, so I decided to remove all trace of it as follows:

1. Installed adb tools

In Lubuntu 20.10:

user $ sudo apt install android-tools-adb

In Gentoo Linux:

root # emerge dev-util/android-tools

2. Enabled ‘Developer Options’ on the phone

‘Settings’ > ‘About Phone’ > ‘Software Information’ and quickly tapped 7 times on ‘Build number’.

3. Enabled USB Debugging on the phone

‘Settings’ > ‘Developer options’, scrolled down and tapped on ‘USB debugging’.

4. Launched adb

user $ adb start-server
* daemon not running; starting now at tcp:5037
* daemon started successfully

5. Connected the phone to the computer using the USB cable

A few prompts on the phone asked whether or not I wanted to allow USB debugging. Tapped ‘Always allow from this computer’ and tapped ‘OK’.

6. Uninstalled Facebook

The packages I needed to uninstall were:

com.facebook.appmanager
com.facebook.katana
com.facebook.services
com.facebook.system

First I tried to uninstall with the ‘-k‘ option:

user $ adb uninstall -k --user 0 com.facebook.appmanager
The -k option uninstalls the application while retaining the data/cache.
At the moment, there is no way to remove the remaining data.
You will have to reinstall the application with the same signature, and fully uninstall it.
If you truly wish to continue, execute 'adb shell cmd package uninstall -k'.

See ‘Difference between pm clear and pm uninstall -k on Android

I have never been a member of Facebook and never will, so I dispensed with the ‘-k‘ option and entered the following commands:

user $ adb uninstall --user 0 com.facebook.appmanager
Success
user $ adb uninstall --user 0 com.facebook.katana
Success
user $ adb uninstall --user 0 com.facebook.services
Success
user $ adb uninstall --user 0 com.facebook.system
Success

I didn’t want the LinkedIn, Samsung Global Goals and Spotify apps either, so I uninstalled those too:

user $ adb uninstall --user 0 com.linkedin.android
Success
user $ adb uninstall --user 0 com.samsung.sree
Success
user $ adb uninstall --user 0 com.spotify.music
Success

7. Stopped the adb server on the computer

user $ adb kill-server

8. Unplugged the phone from the computer.

That’s it.

In order to disable the apps using this method, you will need to know the exact package name of the app you want to get rid of. For this, use Play Store and install App Inspector (there are several apps with this name in Play Store; I installed the app by Projectoria Ltd but the others look OK too). Launch App Inspector and you can find the package name under the name of the app. This starts with a ‘com‘ or ‘net‘ followed by words separated by dots.

For example, App Inspector shows the package name for LinkedIn as ‘com.linkedin.android‘.

Some useful links:

To get a list of all the packages installed on my phone:

user $ adb shell pm list packages

To get a list of system apps only:

user $ adb shell pm list packages -s

To get a list of only Samsung packages:

user $ adb shell pm list packages | grep samsung

To search for e.g. facebook packages:

user $ adb shell pm list packages | grep facebook

(Returns nothing now, as I already deleted all the Facebook packages. Yay!)

To search for other packages, e.g.:

user $ adb shell pm list packages | grep kids
package:com.samsung.android.kidsinstaller
package:com.sec.android.app.kidshome