From: Petr Špaček <petr.spacek@nic.cz>
Date: Thu, 4 Apr 2019 11:19:45 +0000 (+0200)
Subject: doh: limit max query size to 1024 B
X-Git-Tag: v4.0.0~10^2~10
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=937a3ee0d3e6326f59ac0936026457cd6774d299;p=thirdparty%2Fknot-resolver.git

doh: limit max query size to 1024 B

The value is kind of arbitrary, as precaution. 64k value was causing
cqueues to close connections with GET requests with "Broken pipe"
and it seems to work with 1024 B.
---

diff --git a/modules/http/http_doh.lua b/modules/http/http_doh.lua
index ae33edbd7..0299a67a3 100644
--- a/modules/http/http_doh.lua
+++ b/modules/http/http_doh.lua
@@ -20,13 +20,13 @@ local function serve_doh(h, stream)
 	local input
 	local method = h:get(':method')
 	if method == 'POST' then
-		input = stream:get_body_chars(65536, 2)  -- read timeout = KR_CONN_RTT_MAX
+		input = stream:get_body_chars(1025, 2)  -- read timeout = KR_CONN_RTT_MAX
 	elseif method == 'GET' then
 		local input_b64 = string.match(h:get(':path'), '^/doh%?dns=([a-zA-Z0-9_-]+)$')
 		if not input_b64 then
 			return 400, 'base64url query not found'
 		end
-		if #input_b64 > 87380 then  -- base64url encode 65535
+		if #input_b64 > 1368 then  -- base64url encode 1024
 			return 414, 'query parameter in URI too long'
 		end
 		input = basexx.from_url64(input_b64)
@@ -39,7 +39,7 @@ local function serve_doh(h, stream)
 
 	if #input < 12 then
 		return 400, 'input too short'
-	elseif #input > 65535 then
+	elseif #input > 1024 then
 		return 413, 'input too long'
 	end
 
diff --git a/modules/http/http_doh.test.lua b/modules/http/http_doh.test.lua
index 88e7f8644..0e00b02b7 100644
--- a/modules/http/http_doh.test.lua
+++ b/modules/http/http_doh.test.lua
@@ -167,21 +167,21 @@ else
 	local function test_post_long_input()
 		local req = assert(req_templ:clone())
 		req.headers:upsert(':method', 'POST')
-		req:set_body(string.rep('s', 65536))  -- > DNS msg over UDP
+		req:set_body(string.rep('s', 1025))  -- > DNS msg over UDP
 		check_err(req, '413', 'too long POST finishes with 413')
 	end
 
 	local function test_get_long_input()
 		local req = assert(req_templ:clone())
 		req.headers:upsert(':method', 'GET')
-		req.headers:upsert(':path', '/doh?dns=' .. basexx.to_url64(string.rep('s', 65536)))
+		req.headers:upsert(':path', '/doh?dns=' .. basexx.to_url64(string.rep('\0', 1030)))
 		check_err(req, '414', 'too long GET finishes with 414')
 	end
 
 	local function test_post_unparseable_input()
 		local req = assert(req_templ:clone())
 		req.headers:upsert(':method', 'POST')
-		req:set_body(string.rep('\0', 65535))  -- garbage
+		req:set_body(string.rep('\0', 1024))  -- garbage
 		check_err(req, '400', 'unparseable DNS message finishes with 400')
 	end