[extractor/screencastomatic] Support --video-password (#4761)

Authored by: shreyasminocha

yt_dlp/extractor/screencastomatic.py

@@ -1,10 +1,12 @@
 from .common import InfoExtractor
 from ..utils import (
+    ExtractorError,
     get_element_by_class,
     int_or_none,
     remove_start,
     strip_or_none,
     unified_strdate,
+    urlencode_postdata,
 )
 
 
@@ -34,6 +36,28 @@ def _real_extract(self, url):
         video_id = self._match_id(url)
         webpage = self._download_webpage(
             'https://screencast-o-matic.com/player/' + video_id, video_id)
+
+        if (self._html_extract_title(webpage) == 'Protected Content'
+                or 'This video is private and requires a password' in webpage):
+            password = self.get_param('videopassword')
+
+            if not password:
+                raise ExtractorError('Password protected video, use --video-password <password>', expected=True)
+
+            form = self._search_regex(
+                r'(?is)<form[^>]*>(?P<form>.+?)</form>', webpage, 'login form', group='form')
+            form_data = self._hidden_inputs(form)
+            form_data.update({
+                'scPassword': password,
+            })
+
+            webpage = self._download_webpage(
+                'https://screencast-o-matic.com/player/password', video_id, 'Logging in',
+                data=urlencode_postdata(form_data))
+
+            if '<small class="text-danger">Invalid password</small>' in webpage:
+                raise ExtractorError('Unable to login: Invalid password', expected=True)
+
         info = self._parse_html5_media_entries(url, webpage, video_id)[0]
         info.update({
             'id': video_id,