1 files changed, 116 insertions, 0 deletions
diff --git a/modules/http/http_doh.lua b/modules/http/http_doh.lua
new file mode 100644
index 0000000..33815f7
--- /dev/null
+++ b/modules/http/http_doh.lua
@@ -0,0 +1,116 @@
+-- SPDX-License-Identifier: GPL-3.0-or-later
+local basexx = require('basexx')
+local ffi = require('ffi')
+local condition = require('cqueues.condition')
+
+-- Trace execution of DNS queries
+local function serve_doh(h, stream)
+	local input
+	local method = h:get(':method')
+	if method == 'POST' then
+		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'), '^/[^?]*%?dns=([a-zA-Z0-9_-]+)$') or
+				string.match(h:get(':path'), '^/[^?]*%?dns=([a-zA-Z0-9_-]+)&') or
+				string.match(h:get(':path'), '^/[^?]*%?.*&dns=([a-zA-Z0-9_-]+)$') or
+				string.match(h:get(':path'), '^/[^?]*%?.*&dns=([a-zA-Z0-9_-]+)&')
+		if not input_b64 then
+			return 400, 'base64url query not found'
+		end
+		if #input_b64 > 1368 then  -- base64url encode 1024
+			return 414, 'query parameter in URI too long'
+		end
+		input = basexx.from_url64(input_b64)
+		if not input then
+			return 400, 'invalid base64url'
+		end
+	else
+		return 405, 'only HTTP POST and GET are supported'
+	end
+
+	if not input or #input < 12 then
+		return 400, 'input too short'
+	elseif #input > 1024 then
+		return 413, 'input too long'
+	end
+
+	local content_type = h:get('content-type') or 'application/dns-message'
+	if content_type ~= 'application/dns-message' then
+		return 415, 'only Content-Type: application/dns-message is supported'
+	end
+--	RFC 8484 section-4.1 allows us to ignore Accept header
+--	local accept = h:get('accept') or 'application/dns-message'
+--	if accept ~= 'application/dns-message' then
+--		return 406, 'only Accept: application/dns-message is supported'
+--	end
+
+	-- We get these values beforehand, because it's easier to handle errors now.
+	local _, peer_addr, peer_port = stream:peername()
+	local _, dst_addr, dst_port = stream:localname()
+	if not (peer_addr and peer_port and dst_addr and dst_port) then
+		 -- The connection probably died in the meantime or something.
+		return 504, 'failed to determine your address'
+	end
+
+	-- Output buffer
+	local output
+	local output_ttl
+
+	-- Wait for the result of the query
+	-- Note: We can't do non-blocking write to stream directly from resolve callbacks
+	-- because they don't run inside cqueue.
+	local cond = condition.new()
+	local waiting, done = false, false
+	local finish_cb = function (answer, _)
+		output_ttl = ffi.C.packet_ttl(answer)
+		-- binary output
+		output = ffi.string(answer.wire, answer.size)
+		if waiting then
+			cond:signal()
+		end
+		done = true
+	end
+
+	-- convert query to knot_pkt_t
+	local wire = ffi.cast("void *", input)
+	local pkt = ffi.gc(ffi.C.knot_pkt_new(wire, #input, nil), ffi.C.knot_pkt_free)
+	if not pkt then
+		return 500, 'internal server error'
+	end
+
+	local result = ffi.C.knot_pkt_parse(pkt, 0)
+	if result ~= 0 then
+		return 400, 'unparseable DNS message'
+	end
+
+	-- set source address so filters can work
+	local function init_cb(req)
+		req.qsource.addr = ffi.C.kr_straddr_socket(peer_addr, peer_port, req.pool)
+		req.qsource.dst_addr = ffi.C.kr_straddr_socket(dst_addr, dst_port, req.pool)
+		assert(req.qsource.addr ~= nil and req.qsource.dst_addr ~= nil)
+		req.qsource.flags.tcp = true
+		req.qsource.flags.tls = (stream.connection:checktls() ~= nil)
+		req.qsource.flags.http = true
+	end
+
+	-- resolve query
+	worker.resolve_pkt(pkt, {}, finish_cb, init_cb)
+	if not done then
+		waiting = true
+		cond:wait()
+	end
+
+	-- Return buffered data
+	if not done then
+		return 504, 'huh?'  -- FIXME
+	end
+	return output, nil, 'application/dns-message', output_ttl
+end
+
+-- Export endpoints
+return {
+	endpoints = {
+		['/doh'] = {'text/plain', serve_doh, nil, nil, true},
+		['/dns-query'] = {'text/plain', serve_doh, nil, nil, true},
+	}
+}