Solved SOCKS5 proxy for only a few domains

beyondexcess

I'm trying to configure a SOCKS5 proxy to be used for only two domains (say all websites at example.nl and example.net). The Proxy settings button in Vivaldi Settings brings me to a global Windows configuration, which doesn't seem to work, but adding the command line argument --proxy-server="socks5://<host>:<port>" does enable me to use the proxy. However, I can't figure out how to make sure the proxy is only used for these two domains. There is the argument --proxy-bypass-list which lets me specify for which domains the proxy should not be used, but I'm looking for the reverse of that. Is there some other argument that I could use, or some syntax which would work with the bypass list to accomplish this?

I know that an extension like Proxy SwitchyOmega would be able to do this, but I've been afraid to use it after reading this article: https://arstechnica.com/security/2025/01/dozens-of-backdoored-chrome-extensions-discovered-on-2-6-million-devices/

DoctorG

@beyondexcess Ah, ok.

Then something like proxy.pac file could help.
~~Wait…~~

Untested!

/* example */
function FindProxyForURL(url, host) { 
  if (dnsDomainIs(host, ".example.com") return "SOCKS 192.168.0.1:8055;";
  if (dnsDomainIs(host, ".example.org") return "SOCKS 192.168.0.1:8055;";
  return "DIRECT";
}

I think command line option would be (example):
vivaldi --proxy-pac-url=file:///T:/proxy.pac

More:

DoctorG

@beyondexcess I remember that commandline options for SOCKS proxy do not work correctly, on Linux it was discussed at
https://forum.vivaldi.net/topic/92354/no-socks5-proxy-support-yet

beyondexcess

@DoctorG I haven't tried them on Linux, but they do work fine for me on Windows. Only problem is that the proxy is used for too many websites now.

DoctorG

@beyondexcess Ah, ok.

Then something like proxy.pac file could help.
~~Wait…~~

Untested!

/* example */
function FindProxyForURL(url, host) { 
  if (dnsDomainIs(host, ".example.com") return "SOCKS 192.168.0.1:8055;";
  if (dnsDomainIs(host, ".example.org") return "SOCKS 192.168.0.1:8055;";
  return "DIRECT";
}

I think command line option would be (example):
vivaldi --proxy-pac-url=file:///T:/proxy.pac

More:

beyondexcess

@DoctorG Fantastic, that works! I adapted the file to:

function FindProxyForURL(url, host) {
  if (dnsDomainIs(host, ".example.com")) return "SOCKS5 192.168.0.1:8055";
  if (dnsDomainIs(host, ".example.org")) return "SOCKS5 192.168.0.1:8055";
  return "DIRECT";
}

That still didn't work, because apparently file:// urls are no longer allowed: https://superuser.com/questions/1405499/chrome-72-seems-to-no-longer-accept-proxy-pac-url
But I managed to work around that by starting Vivaldi from wsl and using jonny's answer on that page:
/path/to/vivaldi.exe --proxy-pac-url='data:application/x-javascript-config;base64,'$(base64 -w0 /path/to/proxy.pac)

thanks a lot!

DoctorG

@beyondexcess Oh, crazy solution.
Interesting that such Base64 encoded data-URL work.
And … oh, my goodness, starting by Linux shell.
Good trick.

I guess that using a Powershell script would work, too, without Linux shell
But your solution is the shortest way to solve it.

DoctorG

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