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Jan 20 04:20:31 nwhost stunnel: LOG3: No more addresses to connect Jan 20 04:20:31 nwhost stunnel: LOG5: Connection reset: 0 byte(s) sent to TLS, 0 byte(s) sent to socket This setup has worked great for years, but sometime last year (or year before? gawd 2020.), during OS upgrades (Ubuntu 16.04 and 18.04), something changed where stunnel is now spamming the logfiles with hundreds of error messages per second whenever the remote syslog server is rebooted or unavailable. The client, of course, is configured to forward it's logs to the server over stunnel. The remote host has syslog configured to listen for logfiles over the stunnel connection. Nmap done: 1 IP address (1 host up) scanned in 1.I have stunnel v5.44 (Ubuntu 18.04 v3:5.44-1ubuntu3) configured on a client to connect to a server in a screened subnet. Other addresses for localhost (not scanned): ::1 Nmap scan report for localhost (127.0.0.1)
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You can also verify that stunnel is running using nmap to check if the stunnel port is open: Proto Recv-Q Send-Q Local Address Foreign Address State PID/Program name Will not be shown, you would have to be root to see it all.)Īctive Internet connections (only servers) (Not all processes could be identified, non-owned process info On Ubuntu you can use the netstat utility to see open ports: Once stunnel is running properly, you won't see any startup message: In another window you can run tail on the stunnel log: Service : Failed to initialize SSL context SSL_CTX_use_PrivateKey_file: 200100D: error:0200100D:system library:fopen:Permission denied error queue: 140B0002: error:140B0002:SSL routines:SSL_CTX_use_PrivateKey_file:system lib Loading private key from file: /etc/stunnel/ Certificate loaded from file: /etc/stunnel/ Loading certificate from file: /etc/stunnel/ Reading configuration from file /etc/stunnel/nf Threading:PTHREAD Sockets:POLL,IPv6,SYSTEMD TLS:ENGINE,FIPS,OCSP,PSK,SNI Auth:LIBWRAP
Linux stunnel update#
Update OpenSSL shared libraries or rebuild stunnel stunnel 5.30 on x86_64-pc-linux-gnu platform
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Here's an example of a permissions error with a certificate file: If there are problems, stunnel may or may not print them out when you run the stunnel command. This is what a simple stunnel config looks like:Ĭert = /etc/stunnel/ To set this up, we use the nf configuration file.
Linux stunnel install#
The short version: if you control the client and the server, and are using a self-signed certificate, you can skip verification or you can install the server's certificate authority (which, for a self-signed certificate, is the same as the certificate itself).
Linux stunnel how to#
See the Stunnel/Certificates page for more info on how to create an SSL certificate for the server. (Useful if you have a service only exposed to LOCAL traffic from localhost or 127.0.0.1 and not bound to an EXTERNAL ip address like 0.0.0.0). Typically, stunnel is forwarding that traffic on to a local port, something like 8443. (Note that other services like Iodine allow you to do similar things with disguising network connections over port 53, the typical port used by DNS servers.) We can use stunnel on any port that we want, but communicating between stunnel clients and servers on port 443 allows us to disguise arbitrary traffic (HTTP, HTTPS, SSH, database, etc.) as legitimate HTTPS. This means that only stunnel can listen on 443, so this cannot be a server for an HTTPS web site. Therefore the arrangement we will use is, stunnel will listen on port 443, open to external traffic, for SSL-encrypted stunnel traffic. The configuration we're showing here is intended to bypass a local network that allows only HTTP and HTTPS traffic on ports 80 and 443. Stunnel servers can listen on any port, and the port you choose depends on the application. Stunnel running as a server will open two ports: one to listen for incoming traffic, and one to forward the (unencrypted) traffic onto.