When using sockets to pass data between e.g. nginx and oauth2-proxy it's
simpler to use sockets. Systemd can even facilitate this and pass the
actual socket directly.
This also means that only the socket runs with the same group as nginx
while the service runs with DynamicUser.
Does not support TLS yet.
nginx
```
server {
location /oauth2/ {
proxy_pass http://unix:/run/oauth2-proxy/oauth2.sock;
}
```
oauth2-proxy.socket
```
[Socket]
ListenStream=%t/oauth2.sock
SocketGroup=www-data
SocketMode=0660
```
Start oauth2-proxy with the parameter `--http-address=fd:3`.
Signed-off-by: Josef Johansson <josef@oderland.se>
