[ie/dropbox] Fix password-protected video extraction (#11636)

Closes #11634
Authored by: bashonly

yt_dlp/extractor/dropbox.py

@@ -48,32 +48,30 @@ def _real_extract(self, url):
         webpage = self._download_webpage(url, video_id)
         fn = urllib.parse.unquote(url_basename(url))
         title = os.path.splitext(fn)[0]
-        password = self.get_param('videopassword')
+        content_id = None
 
         for part in self._yield_decoded_parts(webpage):
             if '/sm/password' in part:
-                webpage = self._download_webpage(
-                    update_url('https://www.dropbox.com/sm/password', query=part.partition('?')[2]), video_id)
+                content_id = self._search_regex(r'content_id=([\w.+=/-]+)', part, 'content ID')
                 break
 
-        if (self._og_search_title(webpage, default=None) == 'Dropbox - Password Required'
-                or 'Enter the password for this link' in webpage):
-            if password:
-                response = self._download_json(
-                    'https://www.dropbox.com/sm/auth', video_id, 'POSTing video password',
-                    headers={'content-type': 'application/x-www-form-urlencoded; charset=UTF-8'},
-                    data=urlencode_postdata({
-                        'is_xhr': 'true',
-                        't': self._get_cookies('https://www.dropbox.com')['t'].value,
-                        'content_id': self._search_regex(r'content_id=([\w.+=/-]+)["\']', webpage, 'content id'),
-                        'password': password,
-                        'url': url,
-                    }))
-
-                if response.get('status') != 'authed':
-                    raise ExtractorError('Invalid password', expected=True)
-            elif not self._get_cookies('https://dropbox.com').get('sm_auth'):
+        if content_id:
+            password = self.get_param('videopassword')
+            if not password:
                 raise ExtractorError('Password protected video, use --video-password <password>', expected=True)
+
+            response = self._download_json(
+                'https://www.dropbox.com/sm/auth', video_id, 'POSTing video password',
+                data=urlencode_postdata({
+                    'is_xhr': 'true',
+                    't': self._get_cookies('https://www.dropbox.com')['t'].value,
+                    'content_id': content_id,
+                    'password': password,
+                    'url': update_url(url, scheme='', netloc=''),
+                }))
+            if response.get('status') != 'authed':
+                raise ExtractorError('Invalid password', expected=True)
+
             webpage = self._download_webpage(url, video_id)
 
         formats, subtitles = [], {}