How to correctly read the control port when Tor is started with `--ControlPort a

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4 total messages Started by Anonymous@news.n Tue, 11 May 2021 08:09

#216

Author: Anonymous@news.n
Date: Tue, 11 May 2021 08:09

25 lines
1353 bytes

It is possible to start Tor with the following arguments (or parameters in Tor's config file):

    --ControlPort auto --ControlPortWriteToFile <TEMPORARY_FILE_PATH>>

So Tor [writes][1] to `<TEMPORARY_FILE_PATH>` file the following:

    PORT7.0.0.1:58771

and you just read it in your program. This sounds obvious but if I'm not missing something it is not.

So I think the following steps are necessary to read the correct port number:

1. Make sure that `<TEMPORARY_FILE_PATH>` does not exist [to eliminate risk that you read some old value].
1. Start Tor process with the arguments
1. Wait until `<TEMPORARY_FILE_PATH>` file exists [the file may exist but its content may not be flushed just yet now]
1. Repeat
    * Open `<TEMPORARY_FILE_PATH>` file for reading and read a single line (ending with `n`)
    * When the line starts with `PORT=`, you can parse the port -> success & break from loop.

I'm aware that you can start Tor and just wait few hunder milliseconds, read the file and you'll get *most likely* the correct port number. However, I want to read always the correct port number.

My question is: What is the recommended (and correct) procedure to read the control port number?

  [1]: https://github.com/torproject/tor/blob/1d18ecbc5f74e8aba8096e9bfd851ff775bbce0d/src/feature/control/control.c#L134
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Re: How to correctly read the control port when Tor is started with `--ControlPort a

#217

Author: Anonymous@news.n
Date: Tue, 11 May 2021 08:26

18 lines
826 bytes

Anonymous wrote:

> It is possible to start Tor with the following arguments (or parameters in Tor's config file):

>     --ControlPort auto --ControlPortWriteToFile <TEMPORARY_FILE_PATH>>

> So Tor [writes][1] to `<TEMPORARY_FILE_PATH>` file the following:

>     PORT7.0.0.1:58771

> and you just read it in your program. This sounds obvious but if I'm not missing something it is not.

> ...

> I'm aware that you can start Tor and just wait few hunder milliseconds, read the file and you'll get *most likely* the correct port number. However, I want to read always the correct port number.

Is the concern that you may read an old file? The steps you list sound correct and it should work. Maybe test the mtime (file modification time) to see if is a new file or not before using the info.
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Re: How to correctly read the control port when Tor is started with `--ControlPort a

#218

Author: Marc SCHAEFER
Date: Tue, 11 May 2021 08:30

7 lines
208 bytes

Anonymous <Anonymous@news.novabbs.org> wrote:
> My question is: What is the recommended (and correct) procedure to read the control port number?

Set it statically with:

   ControlPort

in the configuration?

Re: How to correctly read the control port when Tor is started with `--ControlPort a

#219

Author: Anonymous@news.n
Date: Wed, 12 May 2021 02:44

14 lines
696 bytes

Anonymous wrote:

> It is possible to start Tor with the following arguments (or parameters in Tor's config file):

>     --ControlPort auto --ControlPortWriteToFile <TEMPORARY_FILE_PATH>>

> So Tor [writes][1] to `<TEMPORARY_FILE_PATH>` file the following:

>     PORT7.0.0.1:58771

> and you just read it in your program. This sounds obvious but if I'm not missing something it is not.

If the control port is set only when Tor starts, you could use a script to modify torrc at each start with a new port number. You would create the port number randomly in your script. Then there is no need to read the log, you know the port number that the script generated.
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