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Key Value Server

The server is self hosted and should be live at keyvalue.ca.

Back End

The back end server is written in rust and interfaces with an sqlite database. It exposes five http endpoints.

(in hindsight, basic auth headers should be used instead of using the body content).

  • /health
    HEAD endpoint. gives ok on health check success, else internal server error.
  • /create-account
    POST json:
    Yields a session token. Same as if logging in. 
    {
  "username": "...",
  "password": "..."
}
  • /login
    PUT json:
    Yields a session token in the form of a uuid, which is used when setting and getting values. 
    {
  "username": "...",
  "password": "..."
}
  • /set-value
    PUT json: 
    {
  "username": "...",
  "session_token": "79997094-a636-4220-87ae-7d42c1412ae7",
  "key": "...",
  "value": "value"
}
  • /get-value
    PUT json:
    Yields the plaintext value. 
    {
  "username": "...",
  "session_token": "79997094-a636-4220-87ae-7d42c1412ae7",
  "key": "...",
}

The database stores the salted password hashes and sessions associated with each user. Since this is a demo, entries that have been inactive for an hour are deleted.

Front End

The front end is JS, CSS, and HTML, statically served by nginx. It has three pages

  • login page
  • create account page
  • set get page

nginx also provides a TLS terminating ingress using let's encrypt as the cert authority.

Initialization Steps

duckdns

I used duckdns as a dynamic dns service, to associate the ip of my server with the correct domain name. Even if the server moves location, then it will automatically update.

This update is run by a cron script, and follows the instructions provided by them:

*/20 * * * * /path/to/duck.sh >/dev/null 2>&1

whc

(in hindsight it's much better and easier to use cloudflare's dns api. todo migrate)

I bought a domain via web hosting canada and used the following configs:

Domain forwarding: https://www.keyvalue.ca

This effectively redirects keyvalue.ca -> www.keyvalue.ca

Under Advanced DNS Manager, I have:

NAME TTL TYPE VALUE
@ 14440 A 149.56.225.6
www 14440 CNAME keyvalue.duckdns.org

the cname record creates an alias of www.keyvalue.ca -> keyvalue.duckdns.org
the A record points to the whc parking area (since they are not hosting the domain for me)

tls limitation

Due to the fact that I don't want to upgrade to whc's hosted plan, there is a tls error under some very specific circumstances, only when typing the url with https and without www, and only noticable when using curl or some browsers.
e.g. curl -vvv https://keyvalue.ca will use whc's ssl certificate, which doesn't match keyvalue's name.
It's not worth it for me to pay for this functionality.

compose

There is a bit more of a complex startup process due to a circular dependency. The nginx configuration can't be used until the tls certificates are available. Yet the certs can't be issued by the cert authority if the server is not running. process inspired from here.

# get recommended TLS parameters. used in nginx config
curl https://raw.githubusercontent.com/certbot/certbot/master/certbot-nginx/certbot_nginx/_internal/tls_configs/options-ssl-nginx.conf > certbot/conf/options-ssl-nginx.conf
curl https://raw.githubusercontent.com/certbot/certbot/master/certbot/certbot/ssl-dhparams.pem > certbot/conf/ssl-dhparams.pem

# creating temporary self signed certificate
# or else nginx 443 server will fail to launch from files not found
mkdir certbot/conf/live/www.keyvalue.ca/
docker compose run --rm --entrypoint "\
  openssl req -x509 -nodes -newkey rsa:4096 -days 1\
    -keyout '/etc/letsencrypt/live/www.keyvalue.ca/privkey.pem' \
    -out '/etc/letsencrypt/live/www.keyvalue.ca/fullchain.pem' \
    -subj '/CN=localhost'" certbot

# at this point, comment out the restart and entrypoint for the certbot service in compose.yaml
# the reason for this is certbot can only do one thing at a time, and will ignore any other calls below like "docker compose run --rm certbot ..."
# just for the startup process, leave it commented out. then uncomment it at the end (mentioned again below).

# check that the site is available via local ip
docker compose up

# leave compose running!
# delete the self signed certificate (or else cert bot will complain that the folder already exists)
rm -rf certbot/conf/live/www.keyvalue.ca/

# generate the correct certificates from the CA
docker compose run --rm certbot certonly --webroot --webroot-path /var/www/certbot/ --dry-run -d www.keyvalue.ca
# if it is successful, then remove --dry-run and do it again

# check if renewing works
docker compose run --rm certbot renew --force-renew

# now uncomment the certbot restart and entrypoint mentioned above, and restart docker compose

systemd

compose is wrapped as a systemd service

# /etc/systemd/system/keyvalue-app.service

[Unit]
Description=keyvalue web app
Requires=docker.service
After=docker.service
StartLimitIntervalSec=120

[Service]
WorkingDirectory=/home/john/key_value
ExecStartPre=/bin/sleep 30
ExecStart=/usr/bin/docker compose up --remove-orphans
ExecStop=/usr/bin/docker compose down
TimeoutStartSec=900
Restart=always
StartLimitBurst=3
# optional for debugging
# StandardInput=null
# StandardOutput=file:/home/john/key_value/out.log
# StandardError=file:/home/john/key_value/error.log

[Install]
WantedBy=multi-user.target

systemctl enable keyvalue-app.service
systemctl start keyvalue-app.service # or reboot to ensure startup success