Send an HMAC(SHA1) protecting the User ID for the ReCAPTCHA bypass, rather than simply the secret itself, so it's useless if that HMAC leaks
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537c7e1137
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1 changed files with 26 additions and 7 deletions
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@ -21,6 +21,8 @@ from synapse.api.constants import LoginType
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from base import RestServlet, client_path_pattern
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import synapse.util.stringutils as stringutils
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from hashlib import sha1
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import hmac
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import json
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import logging
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import urllib
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@ -142,7 +144,7 @@ class RegisterRestServlet(RestServlet):
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if not self.hs.config.enable_registration_captcha:
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raise SynapseError(400, "Captcha not required.")
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yield self._check_recaptcha(request, register_json)
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yield self._check_recaptcha(request, register_json, session)
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session[LoginType.RECAPTCHA] = True # mark captcha as done
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self._save_session(session)
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@ -151,14 +153,27 @@ class RegisterRestServlet(RestServlet):
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})
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@defer.inlineCallbacks
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def _check_recaptcha(self, request, register_json):
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if "captcha_bypass_secret" in register_json:
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if (self.hs.config.captcha_bypass_secret and
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register_json["captcha_bypass_secret"] ==
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def _check_recaptcha(self, request, register_json, session):
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if ("captcha_bypass_hmac" in register_json and
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self.hs.config.captcha_bypass_secret):
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if "user" not in register_json:
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raise SynapseError(400, "Captcha bypass needs 'user'")
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want = hmac.new(
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key=self.hs.config.captcha_bypass_secret,
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msg=register_json["user"],
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digestmod=sha1,
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).hexdigest()
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# str() because otherwise hmac complains that 'unicode' does not
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# have the buffer interface
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got = str(register_json["captcha_bypass_hmac"])
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if hmac.compare_digest(want, got):
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session["user"] = register_json["user"]
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defer.returnValue(None)
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else:
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raise SynapseError(400, "Captcha bypass secret incorrect",
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raise SynapseError(400, "Captcha bypass HMAC incorrect",
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errcode=Codes.CAPTCHA_NEEDED)
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challenge = None
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@ -209,6 +224,10 @@ class RegisterRestServlet(RestServlet):
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# captcha should've been done by this stage!
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raise SynapseError(400, "Captcha is required.")
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if ("user" in session and "user" in register_json and
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session["user"] != register_json["user"]):
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raise SynapseError(400, "Cannot change user ID during registration")
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password = register_json["password"].encode("utf-8")
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desired_user_id = (register_json["user"].encode("utf-8") if "user"
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in register_json else None)
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