Login on failure with Nexus with basic auth

[a186710]

Hello,

I have a Nexus repository with basic auth enabled (not anonymous pull). I see two issues when pulling:

1. Login fails even with docker/config.json having credentials properly set
2. oras-py expects realm of WWW-authenticate to be an URL which is not what Nexus does

Note that pulling the same artifact with Go oras works fine.

I have a doubt on how basic auth is handled in provider.py when using config.json:

1. In _load_auth if a matching token is found, it sets _basic_auth but does not change the headers like set_basic_auth does. Shouldn't it be:

            # Case 2: no auth there (wonky file)
            elif not auth:
                return False
            self._basic_auth = auth
            self.set_header("Authorization", "Basic %s" % self._basic_auth)# <<< add
            return True

2. get_manifest does not load self.header when doing the query while a lot of other methods do. Shouldn't it be something like:

        headers = {"Accept": ";".join(allowed_media_type)}
        headers.update(self.headers) # <<< add
        url = f"{self.prefix}://{container.get_manifest_url()}"  # type: ignore
        response = self.do_request(url, "GET", headers=headers)

If I make these two changes, it works but I'm not sure whether this is entirely correct. If it is, I can submit an MR.

*** .venv/lib/python3.10/site-packages/oras/provider.py     2023-03-24 18:54:38.717625157 +0100
--- provider.py 2023-03-24 19:00:13.727639413 +0100
***************
*** 110,115 ****
--- 110,116 ----
              elif not auth:
                  return False
              self._basic_auth = auth
+             self.set_header("Authorization", "Basic %s" % self._basic_auth)
              return True
          return False
  
***************
*** 694,699 ****
--- 695,701 ----
          if not allowed_media_type:
              allowed_media_type = [oras.defaults.default_manifest_media_type]
          headers = {"Accept": ";".join(allowed_media_type)}
+         headers.update(self.headers)
          url = f"{self.prefix}://{container.get_manifest_url()}"  # type: ignore
          response = self.do_request(url, "GET", headers=headers)
          self._check_200_response(response)

[vsoch]

If you'd like to debug against nexus and submit a pull request with changes, this would be appreciated! I don't have access so I wouldn't be able to make changes and then test them. Thanks!

[a186710]

Done