ser2sock - Serial to Socket Redirector

The ser2sock utility allows sharing of a serial device over a TCP/IP network. It also supports encryption and authentication via OpenSSL.

Installation

1. ./configure
2. make
3. sudo cp ser2sock /usr/local/bin/
4. sudo mkdir -p /etc/ser2sock
5. sudo cp ser2sock.conf.example /etc/ser2sock/ser2sock.conf
6. vi /etc/ser2sock/ser2sock.conf
7. sudo cp init/ser2sock /etc/init.d/
8. sudo update-rc.d ser2sock defaults
9. sudo /etc/init.d/ser2sock start

Usage

Usage: ser2sock -p <socket listen port> -s <serial port dev>

  -h, -help                 display this help and exit
  -p port                   socket port to listen on
  -s <serial device>        serial device; ex /dev/ttyUSB0
options
  -i IP                     bind to a specific ip address; default is ALL
  -b baudrate               set baud rate; defaults to 9600
  -d                        daemonize
  -t                        send terminal init string
  -g                        debug level 0-3
  -c                        keep incoming connections when a serial device is disconnected
  -w milliseconds           delay between attempts to open a serial device (5000)
  -e                        use SSL to encrypt the connection

Authentication via SSL

In addition to supporting cleartext TCP/IP connections, ser2sock also supports SSL authentication and encryption as of v1.4.0.

There are three pieces you need to make this work.

• CA certificate - Certificate Authority that is used to authorize clients against.
• Server-side certificate - The certificate used by ser2sock, signed by the CA.
• Client-side certificate - The certificate used by clients of ser2sock, also signed by the CA.

Generating the Certificates

Create the CA certificate and key: openssl req -out ca.pem -new -x509

Generate the Server key: openssl genrsa -out server.key 2048

Generate a signing request for the Server: openssl req -key server.key -new -out server.req

Sign the server's request:

echo "00" > ca.srl
openssl x509 -req -in server.req -CA ca.pem -CAkey privkey.pem -CAserial ca.srl -out server.pem

Generate the Client key: openssl genrsa -out client.key 2048

Generate a signing request for the Client: openssl req -key client.key -new -out client.req

Sign the client's request: openssl x509 -req -in client.req -CA ca.pem -CAkey privkey.pem -CAserial ca.srl -out client.pem

Now all you have to do is enable encryption in the configuration, update your certificate paths, and restart the service.

Testing the SSL Certificates

After the certificates have been generated and ser2sock restarted you can verify that the certificates work with OpenSSL: openssl s_client -connect 127.0.0.1:10000 -cert client.pem -key client.key -CAfile ca.pem