Minor non-breaking changes to captcha

Added image/jpeg content-type header to /captcha.jpg. Made unsigned digests
urlsafe (as they were intended to be).

anonstream/captcha.py

@@ -5,9 +5,9 @@ from quart import current_app
 from anonstream.helpers.captcha import generate_captcha_digest, generate_captcha_image
 
 CONFIG = current_app.config
+CAPTCHAS = current_app.captchas
 CAPTCHA_FACTORY = current_app.captcha_factory
 CAPTCHA_SIGNER = current_app.captcha_signer
-CAPTCHAS = current_app.captchas
 
 def generate_random_captcha_solution():
     return ''.join(

anonstream/helpers/captcha.py

@@ -31,7 +31,7 @@ def _generate_captcha_unsigned_digest(salt, solution):
         + solution.encode()
     )
     raw_unsigned_digest = hashlib.sha256(parts).digest()[:16] + salt
-    return base64.b64encode(raw_unsigned_digest).removesuffix(b'=')
+    return base64.urlsafe_b64encode(raw_unsigned_digest).removesuffix(b'=')
 
 def generate_captcha_digest(signer, salt, solution):
     unsigned_digest = _generate_captcha_unsigned_digest(salt, solution)
@@ -44,7 +44,7 @@ def check_captcha_digest(signer, digest, answer):
         try:
             unsigned_digest = signer.unsign(
                 digest,
-                max_age=CONFIG['CAPTCHA_LIFETIME']
+                max_age=CONFIG['CAPTCHA_LIFETIME'],
             )
         except BadTimeSignature:
             result = Answer.BAD

anonstream/routes/core.py

@@ -37,4 +37,4 @@ async def captcha(user):
     if image is None:
         return abort(410)
     else:
-        return image
+        return image, {'Content-Type': 'image/jpeg'}