SMP server is the relay server used to pass messages in SimpleX network. SimpleX Chat apps have preset servers (for mobile apps these are smp11, smp12 and smp14.simplex.im), but you can easily change app configuration to use other servers.
SimpleX clients only determine which server is used to receive the messages, separately for each contact (or group connection with a group member), and these servers are only temporary, as the delivery address can change.
_Please note_: when you change the servers in the app configuration, it only affects which servers will be used for the new contacts, the existing contacts will not automatically move to the new servers, but you can move them manually using ["Change receiving address"](../blog/20221108-simplex-chat-v4.2-security-audit-new-website.md#change-your-delivery-address-beta) button in contact/member information pages – it will be automated in the future.
To see which options are available, execute `smp-server` without flags:
```sh
sudo su smp -c smp-server
...
Available commands:
init Initialize server - creates /etc/opt/simplex and
/var/opt/simplex directories and configuration files
start Start server (configuration:
/etc/opt/simplex/smp-server.ini)
delete Delete configuration and log files
```
You can get further help by executing `sudo su smp -c "smp-server <command> -h"`
After that, we need to configure `smp-server`:
### Interactively
Execute the following command:
```sh
sudo su smp -c "smp-server init"
```
There are several options to consider:
-`Enable store log to restore queues and messages on server restart (Yn):`
Enter `y` to enable saving and restoring connections and messages when the server is restarted.
_Please note_: it is important to use SIGINT to restart the server, as otherwise the undelivered messages will not be restored. The connections will be restored irrespective of how the server is restarted, as unlike messages they are added to append-only log on every change.
-`Enable logging daily statistics (yN):`
Enter `y` to enable logging statistics in CSV format, e.g. they can be used to show aggregate usage charts in `Grafana`.
These statistics include daily counts of created, secured and deleted queues, sent and received messages, and also daily, weekly, and monthly counts of active queues (that is, the queues that were used for any messages). We believe that this information does not include anything that would allow correlating different queues as belonging to the same users, but please [let us know](./SECURITY.md), confidentially, if you believe that this can be exploited in any way.
-`Enter server FQDN or IP address for certificate (127.0.0.1):`
Enter your domain or ip address that your smp-server is running on - it will be included in server certificates and also printed as part of server address.
### Via command line options
Execute the following command:
```sh
sudo su smp -c "smp-server init -h"
...
Available options:
-l,--store-log Enable store log for persistence
-s,--daily-stats Enable logging daily server statistics
-a,--sign-algorithm ALG Signature algorithm used for TLS certificates:
ED25519, ED448 (default: ED448)
--ip IP Server IP address, used as Common Name for TLS online
certificate if FQDN is not supplied
(default: "127.0.0.1")
-n,--fqdn FQDN Server FQDN used as Common Name for TLS online
certificate
--no-password Allow creating new queues without password
--password PASSWORD Set password to create new messaging queues
-y,--yes Non-interactive initialization using command-line
options
-h,--help Show this help text
```
You should determine which flags are needed for your use-case and then execute `smp-server init` with `-y` flag for non-interactive initialization:
```sh
sudo su smp -c "smp-server init -y -<yourflag><youroption>"
The server address above should be used in your client configuration, and if you added server password it should only be shared with the other people who you want to allow using your server to receive the messages (all your contacts will be able to send messages - it does not require a password). If you passed IP address or hostnames during the initialisation, they will be printed as part of server address, otherwise replace `<hostnames>` with the actual server hostnames.
## Further configuration
All generated configuration, along with a description for each parameter, is available inside configuration file in `/etc/opt/simplex/smp-server.ini` for further customization. Depending on the smp-server version, the configuration file looks something like this:
Although it's convenient to initialize smp-server configuration directly on the server, operators **ARE ADVISED** to initialize smp-server fully offline to protect your SMP server CA private key.
Follow the steps to quickly initialize the server offline:
3. Destroy the container. All relevant configuration files and keys will be available at `$HOME/simplex/smp/config`.
4. Move your `CA` private key (`ca.key`) to the safe place. For further explanation, see the next section: [Server security: Private keys](#private-keys).
5. Copy all other configuration files **except** the CA key to the server:
Connection to the smp server occurs via a TLS connection. During the TLS handshake, the client verifies smp-server CA and server certificates by comparing its fingerprint with the one included in server address. If server TLS credential is compromised, this key can be used to sign a new one, keeping the same server identity and established connections. In order to protect your smp-server from bad actors, operators **ARE ADVISED** to move CA private key to a safe place. That could be:
- [Tails](https://tails.net/) live usb drive with [persistent and encrypted storage](https://tails.net/doc/persistent_storage/create/index.en.html).
- Offline Linux laptop.
- Bitwarden.
- Any other safe storage that satisfy your security requirements.
Follow the steps to secure your CA keys:
1. Login to your server via SSH.
2. Copy the CA key to a safe place from this file:
```sh
/etc/opt/simplex/ca.key
```
3. Delete the CA key from the server. **Please make sure you've saved you CA key somewhere safe. Otherwise, you would lose the ability to [rotate the online certificate](#online-certificate-rotation)**:
```sh
rm /etc/opt/simplex/ca.key
```
### Online certificate rotation
Operators of smp servers **ARE ADVISED** to rotate online certificate regularly (e.g., every 3 months). In order to do this, follow the steps:
1. Create relevant folders:
```sh
mkdir -p $HOME/simplex/smp/config
```
1. Copy the configuration files from the server to the local machine (if not yet):
SMP-server can also be deployed to be available via [Tor](https://www.torproject.org) network. Run the following commands as `root` user.
1. Install tor:
We're assuming you're using Ubuntu/Debian based distributions. If not, please refer to [offical tor documentation](https://community.torproject.org/onion-services/setup/install/) or your distribution guide.
- Configure offical Tor PPA repository:
```sh
CODENAME="$(lsb_release -c | awk '{print $2}')"
echo "deb [signed-by=/usr/share/keyrings/tor-archive-keyring.gpg] https://deb.torproject.org/torproject.org ${CODENAME} main
Open tor configuration with your editor of choice (`nano`,`vim`,`emacs`,etc.):
```sh
vim /etc/tor/torrc
```
And insert the following lines to the bottom of configuration. Please note lines starting with `#`: this is comments about each individual options.
```sh
# Enable log (otherwise, tor doesn't seem to deploy onion address)
Log notice file /var/log/tor/notices.log
# Enable single hop routing (2 options below are dependencies of the third) - It will reduce the latency at the cost of lower anonimity of the server - as SMP-server onion address is used in the clients together with public address, this is ok. If you deploy SMP-server with onion-only address, you may want to keep standard configuration instead.
SOCKSPort 0
HiddenServiceNonAnonymousMode 1
HiddenServiceSingleHopMode 1
# smp-server hidden service host directory and port mappings
Enable `systemd` service and start tor. Offical `tor` is a bit flaky on the first start and may not create onion host address, so we're restarting it just in case.
```sh
systemctl enable --now tor && systemctl restart tor
```
4. Display onion host:
Execute the following command to display your onion host address:
```sh
cat /var/lib/tor/simplex-smp/hostname
```
### SOCKS port for SMP PROXY
SMP-server versions starting from `v5.8.0-beta.0` can be configured to PROXY smp servers available exclusively through [Tor](https://www.torproject.org) network to be accessible to the clients that do not use Tor. Run the following commands as `root` user.
1. Install tor as described in the [previous section](#installation-for-onion-address).
2. Execute the following command to creatae a new Tor daemon instance:
```sh
tor-instance-create tor2
```
3. Open the `tor2` configuration and replace its content with the following lines:
```sh
vim /etc/tor/instances/tor2/torrc
```
```sh
# Log tor to systemd daemon
Log notice syslog
# Listen to local 9050 port for socks proxy
SocksPort 9050
```
3. Enable service at startup and start the daemon:
```sh
systemctl enable --now tor@tor2
```
You can check `tor2` logs with the following command:
```sh
journalctl -u tor@tor2
```
4. After [server initialization](#configuration), configure the `PROXY` section like so:
SMP-server versions starting from `v5.8.0` can be configured to serve Web page with server information that can include admin info, server info, provider info, etc. Run the following commands as `root` user.
Your configured password of `smp-server`. You can check your configured pasword in `/etc/opt/simplex/smp-server.ini`, under `[AUTH]` section in `create_password:` field.
Your configured hostname(s) of `smp-server`. You can check your configured hosts in `/etc/opt/simplex/smp-server.ini`, under `[TRANSPORT]` section in `host:` field.
Nov 23 19:23:21 5588ab759e80 systemd[1]: Started SMP server.
Nov 23 19:23:21 5588ab759e80 smp-server[30878]: SMP server v3.4.0
Nov 23 19:23:21 5588ab759e80 smp-server[30878]: Fingerprint: d5fcsc7hhtPpexYUbI2XPxDbyU2d3WsVmROimcL90ss=
Nov 23 19:23:21 5588ab759e80 smp-server[30878]: Server address: smp://d5fcsc7hhtPpexYUbI2XPxDbyU2d3WsVmROimcL90ss=:V8ONoJ6ICwnrZnTC_QuSHfCEYq53uLaJKQ_oIC6-ve8=@<hostnames>
Nov 23 19:23:21 5588ab759e80 smp-server[30878]: Store log: /var/opt/simplex/smp-server-store.log
Nov 23 19:23:21 5588ab759e80 smp-server[30878]: Listening on port 5223 (TLS)...
Nov 23 19:23:21 5588ab759e80 smp-server[30878]: not expiring inactive clients
Nov 23 19:23:21 5588ab759e80 smp-server[30878]: creating new queues requires password
```
To stop `smp-server`, run:
```sh
sudo systemctl stop smp-server.service
```
To check tail of `smp-server` log, run:
```sh
sudo journalctl -fu smp-server.service
Nov 23 19:23:21 5588ab759e80 systemd[1]: Started SMP server.
Nov 23 19:23:21 5588ab759e80 smp-server[30878]: SMP server v3.4.0
Nov 23 19:23:21 5588ab759e80 smp-server[30878]: Fingerprint: d5fcsc7hhtPpexYUbI2XPxDbyU2d3WsVmROimcL90ss=
Nov 23 19:23:21 5588ab759e80 smp-server[30878]: Server address: smp://d5fcsc7hhtPpexYUbI2XPxDbyU2d3WsVmROimcL90ss=:V8ONoJ6ICwnrZnTC_QuSHfCEYq53uLaJKQ_oIC6-ve8=@<hostnames>
Nov 23 19:23:21 5588ab759e80 smp-server[30878]: Store log: /var/opt/simplex/smp-server-store.log
Nov 23 19:23:21 5588ab759e80 smp-server[30878]: Listening on port 5223 (TLS)...
Nov 23 19:23:21 5588ab759e80 smp-server[30878]: not expiring inactive clients
Nov 23 19:23:21 5588ab759e80 smp-server[30878]: creating new queues requires password
```
### Monitoring
You can enable `smp-server` statistics for `Grafana` dashboard by setting value `on` in `/etc/opt/simplex/smp-server.ini`, under `[STORE_LOG]` section in `log_stats:` field.
Logs will be stored as `csv` file in `/var/opt/simplex/smp-server-stats.daily.log`. Fields for the `csv` file are:
To configure the app to use your messaging server copy it's full address, including password, and add it to the app. You have an option to use your server together with preset servers or without them - you can remove or disable them.
It is also possible to share the address of your server with your friends by letting them scan QR code from server settings - it will include server password, so they will be able to receive messages via your server as well.
_Please note_: you need SMP server version 4.0 to have password support. If you already have a deployed server, you can add password by adding it to server INI file.