# SDF inside termux
Title: SDF inside termux
Date: 2022-03-07T09:07:59+00:00
Category: Misc
## SDF comes to your pocket: meet Termux
Recently, I stumbled across Termux. It is a combination of terminal
emulator and apt based package manager which makes it possible to do
development related stuff right at your fingertips everywhere you go.
## What you can do inside Termux?
Well, a lot of stuffs. Connecting to sdf via ssh, accessing files stored
on sdf clusters, backing up files into sdf clusters, typing markdown
text and convert it to html, compiling source code, and more that you
can imagine.
For my use case, the main advantage of termux is that it makes it easy
to connect to sdf. I can even transfers my emails on sdf for offline
consumption inside termux. It even possible to setup email client inside
termux to read all those mails transferred from sdf.
### mutt inside Termux
Well, first thing to do is to get a copy of mail spool from sdf. This
can be done easily using scp or sftp.
```bash
# $(whoami) is sdf login name, of course!
scp $(whoami)@tty.sdf.org:/mail/$(whoami) ~/playground/sdf/mail/inbox
```
Then, mutt inside termux can be configured to read offine mail, synced
from sdf.
Here is a snippet from `~/.muttrc` to read mails from sdf inside termux.
```muttrc
mailboxes ~/playground/sdf/mail/inbox
set spoolfile=~/playground/sdf/mail/inbox
```
### sending mail from Termux
With those setups, sdf mails come inside Termux. The tricky part: how
about sending mails? Do I need to fire up ssh connection into sdf every
time I want to send emails?
#### First workaround: compose locally and postpone the message
Without further trick, this is the simplest possible setup. This is
nice, since email can be composed locally, without the need to edit the
file via ssh.
FYI, typing something via ssh is somewhat **laggy**. There is noticeable
delay between entering text and the displayed text. Of course, the typed
input needs to travel far to sdf and sent back to the screen.
So, for convenience: composing mail locally and postponing the mail is a
workaround to get decent typing experience. Later, one needs to login to
sdf with mail in hand, ready to send.
With this setup, `mutt` will append the postponed message to
`~/postponed`. This file can be transferred to sdf, for later delivery.
#### This is too cumbersome. I want to send it right from Termux.
Very demanding, aren't I? Well, it is possible to use `mx.sdf.org` from
within Termux, with `MetaARPA` membership level.
Unfortunately, such membership level is beyond what a mere diary writer
can spend, so here I am stuck with `user` membership.
No problem, I can tell Mutt to send the message with local
`sendmail` script that connect to sdf's sendmail instance.
Here is one line addition inside Termux's `~/.muttrc`
```muttrc
set sendmail=~/bin/sdf_sendmail.sh
```
For this setup, there is configuration needed to get `msmtp` working.
Log into sdf and create `~/.msmtprc`.
```
account sdf
from
[email protected]
user SDFUSERNAME
host mx.sdf.org
port 587
tls on
tls_trust_file ~/.ssl/cacert.pem
account default: sdf
```
For the trust file, a copy of Termux's ca bundle can be used.
Alternatively, curl's ca bundle can be obtained easily to the designated
`tls_trust_file`.
Now back to Termux. A simple `~/bin/sdf_sendmail.sh` executable needs to be created so `mutt`
can send mail directly, without `postponed` workaround above.
Here is the content of `~/bin/sdf_sendmail.sh`
```bash
#!/bin/sh
SDFUSERNAME="myloginnamehere"
if [ -S "$SSH_AUTH_SOCK" ] ; then
ssh-add -l | grep sdf && \
ssh "$SDFUSERNAME"@tty.sdf.org "msmtp $*" || \
{ echo "ssh key is not added to agent" ; \
echo "refusing operation" ; \
return 1 ;}
else
echo "Unable to use ssh-agent"
echo "Ensure you have started ssh-agent"
echo "and add the key for tty.sdf.org to the agent."
echo -e '\a'
return 1
fi
```
Give it executable bit and mutt is ready to go.
```bash
chmod +x ~/bin/sdf_sendmail.sh
```
`~/bin/sdf_sendmail.sh` relies on public key authentication enabled
for the account used on sdf, so be sure to start `ssh-agent` and add the
key to agent before sending mail from Termux.
```bash
eval $(ssh-agent)
ssh-add ~/.ssh/sdf.key
```
With the setup, everytime `mutt` sends a message,
`~/bin/sdf_sendmail.sh` is launched. If the requirements are met: the
presence of running `ssh-agent` and the key for sdf login has been added
to the agent, `mutt` will send the message via `msmtp` that is
accessible on the sdf cluster.
The benefit of this setup: mail sent from Termux as if one is sending
from sdf ssh session. No ip address at home is exposed on the mail and
the email will go through the sdf mail server, without any violation of
sdf's spf records.
Very convenient, indeed!
