Any suggestion on how to tap snap applications?

[astonchev]

First of all, I applaud your elegant approach!
I guess it's a simple issue, but my lack of golang skills prevents me from finding a workaround:
(Ubuntu 24.04.1)

$ curl -L https://github.com/monasticacademy/httptap/releases/download/v0.0.5/httptap_linux_x86_64.tar.gz | tar xzf -
...
$ sudo snap install helm --classic
...
$ sudo ./httptap -- helm search hub anything
cannot fstatat canonical snap directory: Permission denied
subprocess exited with code 1

[alexflint]

Oh fascinating. Haven't tried it with snap in my testing. What if you try adding --no-overlay like this:

./httptap --no-overlay -- helm search hub anything

[astonchev]

Still the same unfortunately

$ sudo ./httptap --no-overlay -- helm search hub anything
cannot fstatat canonical snap directory: Permission denied
subprocess exited with code 1

[alexflint]

Yeah I can reproduce this now. It looks like this is related to the user namespace that httptap creates, which is only necessary for non-root, so you should be able to do:

sudo ./httptap --no-new-user-namespace helm search hub foo

I think I can support this case better though... I'll look into making this work out of the box.

[astonchev]

Confirm. Thank you so much for your work, Alex

[mhalano]

I installed using go install, but I still get the error:

➜ ~/go/bin/httptap -- thunderbird
cannot fstatat() in canonical tools directory: Permission denied

Using the namespace trick didn't work either, but for some other reason:

➜ sudo ~/go/bin/httptap --no-new-user-namespace --verbose thunderbird
at second stage, creating certificate authority...
created /tmp/3809910581/ca-certificates.crt
created /tmp/3809910581/ca-bundle.crt
created /tmp/3809910581/ca-certificates.pkcs12
tun device has MTU 1500
overlaying /etc ...
overlaying /etc/ssl/certs/ca-certificates.crt...
openssl is installed and configured to read "SSL_CERT_FILE"
openssl is installed and configured to read "SSL_CERT_DIR"
running subcommand now ================
listening on httptap
launching third stage targetting uid 0, gid 0...
mkdir: cannot create directory ‘/run/user/0’: Permission denied
Error: cannot open display: :0

My goal here is understand how many connections Thunderbird does with Gmail because I getting an error about too many connections, so I think it would be nice to use this tool to find this information.

[alexflint]

I can reproduce this problem with most GUI-oriented snap applications. I guess this is because the network namespace created by httptap interrupts the X11 network connections. I don't know why mkdir: cannot create directory ‘/run/user/0’: Permission denied would happen. It seems to happen even when adding --no-overlay. I need to invetigate this further at my end and understand how to implement X forwarding.

[alexflint]

Well, I'm going to post some comments here as I investigate this. It looks like the X11 socket is accessible from within httptap:

$ httptap file /tmp/.X11-unix/X0                                                                                              
/tmp/.X11-unix/X0: socket

Furthermore elementary X applications work just fine under httptap:

$ httptap xcalc   # calculator shows up just fine

So this is something beyond the basic X11 socket.

[alexflint]

Slightly less elementary example: running gnome-calculator etc under httptap works fine too:

$ httptap gnome-calculator   # calculator shows up

[alexflint]

Running the hello-world snap does not work as non-root under httptap:

$ httptap snap run hello-world                                                                                                 
cannot fstatat() in canonical tools directory: Permission denied

However the same under sudo works fine:

$ sudo $(which httptap) snap run hello-world                                                          
Hello World!

So there are at least some snap applications that can be run under some circumstances under httptap...

[alexflint]

However the gnome-calculator snap does not work, and produces the error that most snaps seem to run into:

$ sudo $(which httptap) snap run gnome-calculator
mkdir: cannot create directory ‘/run/user/0’: Permission denied
Authorization required, but no authorization protocol specified


(gnome-calculator:306957): Gtk-WARNING **: 17:55:09.814: Failed to open display

A good way to explore what's going on is using the dash-shell snap to get a shell under snap+httptap like this:

$ sudo snap install dash-shell
$ sudo $(which httptap) -- snap run dash-shell.dash                                                                          
HTTPTAP # 

However, it's a rather austere environment... no curl or wget

[alexflint]

OK a very slightly less austere option is:

sudo snap install bash-omgerbuilder
sudo $(which httptap) snap run bash-omgerbuilder

There is a "curl" snap but it's less helpful because you don't get a shell, so you can't poke around in the environment. However, it doesn't actually work under httptap, which is very interesting:

$ sudo $(which httptap) snap run curl example.com                                                                           
curl: (6) Could not resolve host: example.com