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Prism_Breaker

Use syncthing to share big file over tor

Onionshare is a good choice when you want to share small files over tor. But onionshare cannot handle big files, when tor circuit fails(which is quite common) your download simply fails, and it does not support resuming the download at where it fails. Syncthing is a better alternative for sharing big files over tor, because it will automatically retry at break point when network fails.

Syncthing is FOSS software and has E2EE by default, and can run without a clearnet ip address. This means you can just spin up a client, and your data will be encrypted and sent through syncthing network. If you have a threat model that needs a way to reliably share files with minimum exposure, this setup will be suitable.

Syncthing has its own relays for supporting tranmission of files between peers which are both behind the nat, and it works when both parties are behind tor. This guarantees the anonymity of both parties.

OPSEC Recommendations:
1.Hardware : (Personal Computer / Laptop)
2.Host OS: Linux (Or Qubes OS)
3.Hypervisor: libvirtd QEMU/KVM (Or Qubes OS's Xen)
4.Guest OS: Whonix setup

It is highly recommended to use whonix for this setup, because there are always cases that an app might not honor your proxy setting and somehow connects directly. It is always a good idea to put sensitive app behind whonix gateway, so your clearnet ip will never be exposed

Initial Setup

The first thing to do is to get syncthing to your whonix workstation. Download the syncthing client from their website

Next verify the sha256sum according to https://syncthing.net/security/

curl -s https://syncthing.net/release-key.txt | gpg --import

Check the gpg fingerprint, it should be like this

gpg --fingerprint
/home/user/.gnupg/pubring.kbx
-----------------------------
pub   rsa2048/0xD26E6ED000654A3E 2014-12-29 [SC]
		Key fingerprint = 37C8 4554 E7E0 A261 E4F7  6E1E D26E 6ED0 0065 4A3E
uid                   [ unknown] Syncthing Release Management 
sub   rsa2048/0x681C3CFCF614F575 2014-12-29 [E]

Then download verify the checksum file, and check the checksum to see if it matches

$ curl -sLO https://github.com/syncthing/syncthing/releases/download/v1.23.6/sha256sum.txt.asc	

$ gpg --verify sha256sum.txt.asc
gpg: Signature made Mo 03 Jul 2023 10:09:30 UTC
gpg:                using RSA key D26E6ED000654A3E
gpg: Good signature from "Syncthing Release Management "
gpg: WARNING: This key is not certified with a trusted signature!
gpg:          There is no indication that the signature belongs to the owner.	

$ sha256sum -c sha256sum.txt.asc
...
sha256sum: syncthing-linux-386-v1.23.6.tar.gz: No such file or directory
syncthing-linux-386-v1.23.6.tar.gz: FAILED open or read
syncthing-linux-amd64-v1.23.6.tar.gz: OK  <-- this one
sha256sum: syncthing-linux-armv5-v1.23.6.tar.gz: No such file or directory
syncthing-linux-armv5-v1.23.6.tar.gz: FAILED open or read
...
sha256sum: WARNING: 14 lines are improperly formatted
sha256sum: WARNING: 35 listed files could not be read

Next you need to do some changes in the tor browser, so you can access the web panel

type about:config inside the address bar, accept the risk and continue

serach for no_proxies_on in the search bar, and add 127.0.0.1 to it

Set up syncthing

Next decompress the syncthing pack and execute it

$ tar xvf syncthing-linux-amd64-v1.28.0.tar.gz

$ cd syncthing-linux-amd64-v1.28.0/

$ ./syncthing

If you have setup your tor browser correctly it should automatically redirect you to http://127.0.0.1:8384/ and you will see the web panel

Next thing to do is to find your client id, it is in the actions menu

Next exchange this id with people you are sharing file with

After that add each other in both clients in the remote device section, if nothing goes wrong you should be able to see each other in the remote device section showed as "connected"

Sync files

After the previous setup, you can share the file you want

Choose add folder to create a new sharing Folder, and choose to share this folder with your peer

If nothing goes wrong, the receiver should this

Agree and add the folder, after that syncthing will automatically transmit the files

The last remainder is syncthing over tor is really slow! Because if both parties are behind, your file will probably goes through a circuit like this: You -> Yours three tor nodes -> Syncthing node -> Receiver's three tor nodes -> Receiver

I personally tried this setup, and it took me 4 hours 30 minutes to send a 10GB file. So be patient when you are sending some large files