request_uri allows CRLF injection

Start at the request_uri API and reproduce the report with the provided Lua example and a netcat server. Check how the URI is sent when it contains CRLF, then verify that the completed change prevents injected requests while preserving the normal request. Add or run coverage for the demonstrated input if the repository’s existing test layout provides one.

The request_uri API syntax: res, err = httpc:request_uri(uri, params) allows the 1st param uri to contain CRLF (\r\n), which can be used to inject another request with http pipelining.

For example, the following code will result in 3 requests to be made.

1. run nc as dummy http server nc -k -l 127.0.0.1 8088
2. run test code

local http = require 'resty.http'

local httpc = http.new()

local mq = " HTTP/1.1\r\nHost: 127.0.0.1:8088\r\nContent-Type: application/json\r\nX-File: abc\r\nContent-Length: 2\r\n\r\n{}GET /xxx-inject HTTP/1.1\r\nHost: 127.0.0.1:8088\r\nContent-Length: 0\r\n\r\nGET /world"

local ret, err = httpc:request_uri('http://127.0.0.1:8088/hello'..mq)

Result in nc output:

GET /hello HTTP/1.1
Host: 127.0.0.1:8088
Content-Type: application/json
X-File: abc
Content-Length: 2

{}GET /xxx-inject HTTP/1.1
Host: 127.0.0.1:8088
Content-Length: 0

GET /world HTTP/1.1
User-Agent: lua-resty-http/0.16.1 (Lua) ngx_lua/10019
Host: 127.0.0.1:8088

A possible fix is:

local http = require 'resty.http'

local httpc = http.new()

local mq = " HTTP/1.1\r\nHost: 127.0.0.1:8088\r\nContent-Type: application/json\r\nX-File: abc\r\nContent-Length: 2\r\n\r\n{}GET /xxx-inject HTTP/1.1\r\nHost: 127.0.0.1:8088\r\nContent-Length: 0\r\n\r\nGET /world"

local function uri_gsub_crlf(uri)
	return string.gsub(uri, '[\r\n]', function (s)
		return string.format('%%%02X', string.byte(s))
	end)
end

mq = uri_gsub_crlf(mq)

local ret, err = httpc:request_uri('http://127.0.0.1:8088/hello'..mq)

After the above fix, output in nc will be:

GET /hello HTTP/1.1%0D%0AHost: 127.0.0.1:8088%0D%0AContent-Type: application/json%0D%0AX-File: abc%0D%0AContent-Length: 2%0D%0A%0D%0A{}GET /xxx-inject HTTP/1.1%0D%0AHost: 127.0.0.1:8088%0D%0AContent-Length: 0%0D%0A%0D%0AGET /world HTTP/1.1
User-Agent: lua-resty-http/0.16.1 (Lua) ngx_lua/10019
Host: 127.0.0.1:8088