From 566a991f8499d815314b695cb52959f334bcb9e9 Mon Sep 17 00:00:00 2001
From: Kim Alvefur <zash@zash.se>
Date: Thu, 16 Mar 2023 12:18:23 +0100
Subject: util.sasl.oauthbearer: Return username from callback instead using
 authzid (BC)

RFC 6120 states that
>  If the initiating entity does not wish to act on behalf of another
>  entity, it MUST NOT provide an authorization identity.

Thus it seems weird to require it here.  We can instead expect an
username from the token data passed back from the profile.

This follows the practice of util.sasl.external where the profile
callback returns the selected username, making the authentication module
responsible for extracting the username from the token.
---
 plugins/mod_tokenauth.lua | 12 +++++++-----
 util/sasl/oauthbearer.lua | 36 +++---------------------------------
 2 files changed, 10 insertions(+), 38 deletions(-)

diff --git a/plugins/mod_tokenauth.lua b/plugins/mod_tokenauth.lua
index 03f6b961..f1bd084a 100644
--- a/plugins/mod_tokenauth.lua
+++ b/plugins/mod_tokenauth.lua
@@ -125,19 +125,21 @@ function revoke_token(token)
 end
 
 function sasl_handler(auth_provider, purpose, extra)
-	return function (_, username, token, realm)
+	return function (sasl, token, realm, _authzid)
 		local token_info, err = get_token_info(token);
 		if not token_info then
 			module:log("debug", "SASL handler failed to verify token: %s", err);
 			return nil, nil, extra;
 		end
-		local token_user, token_host = jid.split(token_info.jid);
-		if username ~= token_user or realm ~= token_host or (purpose and token_info.purpose ~= purpose) then
+		local token_user, token_host, resource = jid.split(token_info.jid);
+		if realm ~= token_host or (purpose and token_info.purpose ~= purpose) then
 			return nil, nil, extra;
 		end
-		if auth_provider.is_enabled and not auth_provider.is_enabled(username) then
+		if auth_provider.is_enabled and not auth_provider.is_enabled(token_user) then
 			return true, false, token_info;
 		end
-		return true, true, token_info;
+		sasl.resource = resource;
+		sasl.token_info = token_info;
+		return token_user, true, token_info;
 	end;
 end
diff --git a/util/sasl/oauthbearer.lua b/util/sasl/oauthbearer.lua
index 939c5385..490a205f 100644
--- a/util/sasl/oauthbearer.lua
+++ b/util/sasl/oauthbearer.lua
@@ -1,8 +1,4 @@
-local saslprep = require "util.encodings".stringprep.saslprep;
-local nodeprep = require "util.encodings".stringprep.nodeprep;
-local jid = require "util.jid";
 local json = require "util.json";
-local log = require "util.logger".init("sasl");
 local _ENV = nil;
 
 
@@ -32,37 +28,13 @@ local function oauthbearer(self, message)
 		return "failure", "malformed-request";
 	end
 
-	local username = jid.prepped_split(gs2_authzid);
-
-	if not username or username == "" then
-		return "failure", "malformed-request", "Expected authorization identity in the username@hostname format";
-	end
-
-	-- SASLprep username
-	username = saslprep(username);
-
-	if not username or username == "" then
-		log("debug", "Username violates SASLprep.");
-		return "failure", "malformed-request", "Invalid username.";
-	end
-
-	local _nodeprep = self.profile.nodeprep;
-	if _nodeprep ~= false then
-		username = (_nodeprep or nodeprep)(username);
-		if not username or username == "" then
-			return "failure", "malformed-request", "Invalid username or password."
-		end
-	end
-
-	self.username = username;
-
 	local token = auth_header:match("^Bearer (.+)$");
 
-	local correct, state, token_info = self.profile.oauthbearer(self, username, token, self.realm);
+	local username, state, token_info = self.profile.oauthbearer(self, token, self.realm, gs2_authzid);
 
 	if state == false then
 		return "failure", "account-disabled";
-	elseif state == nil or not correct then
+	elseif state == nil or not username then
 		-- For token-level errors, RFC 7628 demands use of a JSON-encoded
 		-- challenge response upon failure. We relay additional info from
 		-- the auth backend if available.
@@ -72,9 +44,7 @@ local function oauthbearer(self, message)
 			["openid-configuration"] = token_info and token_info.oidc_discovery_url or nil;
 		});
 	end
-
-	self.resource = token_info.resource;
-	self.role = token_info.role;
+	self.username = username;
 	self.token_info = token_info;
 
 	return "success";
-- 
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