Repository: yt-dlp
Issue: .netrc authentification does not quote backslash character in password
Labels: bug,external issue,core:extractor

### DO NOT REMOVE OR SKIP THE ISSUE TEMPLATE

- [X] I understand that I will be **blocked** if I *intentionally* remove or skip any mandatory\* field

### Checklist

- [X] I'm reporting a bug unrelated to a specific site
- [X] I've verified that I'm running yt-dlp version **2023.07.06** ([update instructions](https://github.com/yt-dlp/yt-dlp#update)) or later (specify commit)
- [X] I've checked that all provided URLs are playable in a browser with the same IP and same login details
- [X] I've checked that all URLs and arguments with special characters are [properly quoted or escaped](https://github.com/yt-dlp/yt-dlp/wiki/FAQ#video-url-contains-an-ampersand--and-im-getting-some-strange-output-1-2839-or-v-is-not-recognized-as-an-internal-or-external-command)
- [X] I've searched [known issues](https://github.com/yt-dlp/yt-dlp/issues/3766) and the [bugtracker](https://github.com/yt-dlp/yt-dlp/issues?q=) for similar issues **including closed ones**. DO NOT post duplicates
- [X] I've read the [guidelines for opening an issue](https://github.com/yt-dlp/yt-dlp/blob/master/CONTRIBUTING.md#opening-an-issue)

### Provide a description that is worded well enough to be understood

When using ``.netrc`` authentication, if you have a password that contains a backslash character ``\``, it will be treated as an escape character for the next character instead of the backslash literal.

Say for example, your password was ``a\b`` and the content of your ``.netrc`` file was
```
machine watchnebula login test@example.net password a\b
```
yt-dlp would then interpret the password as ``ab`` as b escaped just turns into b again. The same does not occur when using ``--username`` authentication. If you type ``a\b`` in the password prompt, yt-dlp interprets the backslash character as a literal backslash and the entire password as ``a\b``.

I believe this is not intentional behavior since:
- Your readme section **Authentication with netrc** does not mention the need to manually escape backslashes in passwords
- Neither does the [website about .netrc files you link to](https://stackoverflow.com/tags/.netrc/info) in the readme
- I couldn't find any information on the internet about the need to manually escape backslashes in passwords in ``.netrc`` files.

In the **Complete Verbose Output** section of this issue, I have slightly modified the code in order to better demonstrate the issue. I have added a ``print(password)`` statement to the ``_get_login_info`` function in ``yt-dlp/yt_dlp/extractor/common.py`` just before https://github.com/yt-dlp/yt-dlp/blob/9b16762f48914de9ac914601769c76668e433325/yt_dlp/extractor/common.py#L1347
so we can see the difference in interpreting the password when running the verbose example with ``--netrc`` and with ``--username``. See the line below ``yt-dlp is up to date (stable@2023.07.06)`` in the respective verbose outputs.

In my example I use the ``nebula`` extractor since this is where I first noticed the issue, however from what I can tell the issue seems to be unrelated to that specific extractor but rather be a core issue.

In order to answer the questions of "How it could be fixed", I would suggest escaping backslashes in ``.netrc`` passwords so that backslash literals are still interpreted as backslash literals. In case I am wrong with my assessment and that is actually the intended behavior I would instead appreciate if the need to manually escape backslashes in passwords in netrc authentication was mentioned in the **Authentication with netrc** section in the readme.

### Provide verbose output that clearly demonstrates the problem

- [X] Run **your** yt-dlp command with **-vU** flag added (`yt-dlp -vU <your command line>`)
- [ ] If using API, add `'verbose': True` to `YoutubeDL` params instead
- [X] Copy the WHOLE output (starting with `[debug] Command-line config`) and insert it below

### Complete Verbose Output

```shell
# using .netrc authentication
~ yt-dlp -vU https://nebula.tv/videos/jetlag-ep-4-we-played-a-96hour-game-of-capture-the-flag-across-japan --netrc                               
[debug] Command-line config: ['-vU', 'https://nebula.tv/videos/jetlag-ep-4-we-played-a-96hour-game-of-capture-the-flag-across-japan', '--netrc']
[debug] User config "/home/dasug/.yt-dlp/config": []
[debug] Encodings: locale UTF-8, fs utf-8, pref UTF-8, out utf-8, error utf-8, screen utf-8
[debug] yt-dlp version stable@2023.07.06 [b532a3481]
[debug] Python 3.11.3 (CPython x86_64 64bit) - Linux-6.4.3-zen1-2-zen-x86_64-with-glibc2.37 (OpenSSL 3.1.1 30 May 2023, glibc 2.37)
[debug] exe versions: ffmpeg 6.0 (setts), ffprobe 6.0, rtmpdump 2.4
[debug] Optional libraries: Cryptodome-3.12.0, brotlicffi-1.0.9.2, certifi-2023.05.07, mutagen-1.46.0, secretstorage-3.3.3, sqlite3-2.6.0, websockets-10.4
[debug] Proxy map: {}
[debug] Loaded 1855 extractors
[debug] Fetching release info: https://api.github.com/repos/yt-dlp/yt-dlp/releases/latest
Available version: stable@2023.07.06, Current version: stable@2023.07.06
yt-dlp is up to date (stable@2023.07.06)
ab
[Nebula] Logging in to Nebula with supplied credentials
WARNING: [Nebula] Authentication failed or rejected: HTTP Error 400: Bad Request
ERROR: [Nebula] jetlag-ep-4-we-played-a-96hour-game-of-capture-the-flag-across-japan: This video is only available for registered users. Use --username and --password, --netrc-cmd, or --netrc (watchnebula) to provide account credentials
  File "/usr/lib/python3.11/site-packages/yt_dlp/extractor/common.py", line 707, in extract
    self.initialize()
  File "/usr/lib/python3.11/site-packages/yt_dlp/extractor/common.py", line 613, in initialize
    self._perform_login(username, password)
  File "/usr/lib/python3.11/site-packages/yt_dlp/extractor/nebula.py", line 109, in _perform_login
    self._nebula_api_token = self._perform_nebula_auth(username, password)
                             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/usr/lib/python3.11/site-packages/yt_dlp/extractor/nebula.py", line 33, in _perform_nebula_auth
    self.raise_login_required(method='password')
  File "/usr/lib/python3.11/site-packages/yt_dlp/extractor/common.py", line 1170, in raise_login_required
    raise ExtractorError(msg, expected=True)


# using --username authentication
~ yt-dlp -vU https://nebula.tv/videos/jetlag-ep-4-we-played-a-96hour-game-of-capture-the-flag-across-japan --username="test@example.net"
[debug] Command-line config: ['-vU', 'https://nebula.tv/videos/jetlag-ep-4-we-played-a-96hour-game-of-capture-the-flag-across-japan', '--username=PRIVATE']
[debug] User config "/home/dasug/.yt-dlp/config": []
Type account password and press [Return]: 
[debug] Encodings: locale UTF-8, fs utf-8, pref UTF-8, out utf-8, error utf-8, screen utf-8
[debug] yt-dlp version stable@2023.07.06 [b532a3481]
[debug] Python 3.11.3 (CPython x86_64 64bit) - Linux-6.4.3-zen1-2-zen-x86_64-with-glibc2.37 (OpenSSL 3.1.1 30 May 2023, glibc 2.37)
[debug] exe versions: ffmpeg 6.0 (setts), ffprobe 6.0, rtmpdump 2.4
[debug] Optional libraries: Cryptodome-3.12.0, brotlicffi-1.0.9.2, certifi-2023.05.07, mutagen-1.46.0, secretstorage-3.3.3, sqlite3-2.6.0, websockets-10.4
[debug] Proxy map: {}
[debug] Loaded 1855 extractors
[debug] Fetching release info: https://api.github.com/repos/yt-dlp/yt-dlp/releases/latest
Available version: stable@2023.07.06, Current version: stable@2023.07.06
yt-dlp is up to date (stable@2023.07.06)
a\b
[Nebula] Logging in to Nebula with supplied credentials
[Nebula] Authorizing to Nebula
[Nebula] Extracting URL: https://nebula.tv/videos/jetlag-ep-4-we-played-a-96hour-game-of-capture-the-flag-across-japan
[Nebula] jetlag-ep-4-we-played-a-96hour-game-of-capture-the-flag-across-japan: Fetching video meta data
^C
ERROR: Interrupted by user
```