sockhole is a decrypting
SOCKS
proxy.
When it receives a request to make a connection to a port listed in its
TLS_PORTS list, it will establish the encrypted connection itself, verify the
TLS certificate, and then proxy decrypted data to the client as if the
connection were made to a plaintext service.
This is intended to support old software/equipment which supports SOCKS proxies
but does not support SSL/TLS or modern ciphers.
That software can establish a plaintext connection over a trusted LAN
connection to a local machine running sockhole, and the sockhole proxy can
establish a secure tunnel over the public internet.
For example, a computer running a POP3 client with SOCKS proxy support but no SSL support can connect to a remote POP3 server over TLS just by switching the port configured in the POP3 client to 995 (POP3S).
server$ bundle install --path vendor/bundle
server$ bundle exec ruby sockhole.rb
Supported options:
-a allowed range: add the IP/mask to the list of allowed IPs; defaults to the /24 of the listen IP-d: enable debugging-p port: set the listen port (defaults to 1080)-i ip: set the listen IP (defaults to the first non-loopback IP on all interfaces)
curl should be instructed to use the http protocol on port 443, not
https, or else it will expect encrypted data to come through the SOCKS proxy.
However, when specifying a URL of http://example.com:443/, curl will send a
header of Host: example.com:443 which may cause problems on the server end
with it not matching a configured virtual host.
The -H option can be used to override the sent Host header to remove the
port:
server$ bundle exec ruby sockhole.rb
[2020-11-12 08:47:24 -0600] [I] [server] listening on 192.168.1.1:1080
client$ curl -H "Host: example.com" --preproxy socks5h://192.168.1.1 http://example.com:443/
<!doctype html>
...
When connecting to a TLS host with an invalid certificate, sockhole will reject
the client before it sends any data.
client$ curl -H "Host: wrong.host.badssl.com" --preproxy socks5h://192.168.1.1 http://wrong.host.badssl.com:443/
curl: (97) connection to proxy closed
client$ nc -x 192.168.1.1 imap.fastmail.com imaps
* OK IMAP4 ready