Lapis failed to handle HTTP-request with duplicated header key `Content-Type`

[Toliak]

Is there an existing issue for this?

No, I have searched the existing issues (query: "attempt to call method 'lower'")

Related issue: Kong/kong#14187

Version

I am using the docker image kong:3.9.0-ubuntu

# luarocks show lapis

kong-lapis 1.16.0.1-1 - A fork of leafo/lapis for Kong

License:        MIT
Installed in:   /usr/local

Error

Logs from netcat:

HTTP/1.1 500 Internal Server Error
Date: Fri, 17 Jan 2025 13:31:20 GMT
Content-Type: application/json; charset=utf-8
Connection: keep-alive
Access-Control-Allow-Origin: http://localhost:8002
X-Kong-Admin-Request-ID: c18cf71ef5ecf01b7fcc0d1fa9eaaa3e
vary: Origin
Access-Control-Allow-Credentials: true
Content-Length: 42
X-Kong-Admin-Latency: 8
Server: kong/3.9.0.0-enterprise-edition

{"message":"An unexpected error occurred"}%

Logs from server:

2025/01/17 13:31:20 [error] 2550#0: *11300 [lua] api_helpers.lua:541: handle_error(): /usr/local/share/lua/5.1/lapis/application.lua:440: /usr/local/share/lua/5.1/lapis/application.lua:488: attempt to call method 'lower' (a nil value)
stack traceback:
        /usr/local/share/lua/5.1/lapis/application.lua: in function </usr/local/share/lua/5.1/lapis/application.lua:484>

stack traceback:
        [C]: in function 'error'
        /usr/local/share/lua/5.1/lapis/application.lua:440: in function 'handler'
        /usr/local/share/lua/5.1/lapis/application.lua:186: in function 'resolve'
        /usr/local/share/lua/5.1/lapis/application.lua:217: in function </usr/local/share/lua/5.1/lapis/application.lua:215>
        [C]: in function 'xpcall'
        /usr/local/share/lua/5.1/lapis/application.lua:215: in function 'dispatch'
        /usr/local/share/lua/5.1/lapis/nginx.lua:231: in function 'serve'
        /usr/local/share/lua/5.1/kong/init.lua:2130: in function 'admin_content'
        content_by_lua(nginx-kong.conf:447):2: in main chunk, client: 172.17.0.1, server: kong_admin, request: "GET / HTTP/1.1", host: "127.0.0.0"

The trace from the server relates to the lapis, so I have created the issue in this repository instead of Kong.

Steps to reproduce

The start.sh file (based on the docker image documentation):

#! /bin/bash
set -ue
SCRIPT_DIR=$( cd -- "$( dirname -- "${BASH_SOURCE[0]}" )" &> /dev/null && pwd )
MOUNT_DIR="$SCRIPT_DIR/kong-vol"

docker run -it --name kong-dbless \
 -v "$MOUNT_DIR:/kong/declarative/" \
 -e "KONG_DATABASE=off" \
 -e "KONG_DECLARATIVE_CONFIG=/kong/declarative/kong.yml" \
 -e "KONG_PROXY_ACCESS_LOG=/dev/stdout" \
 -e "KONG_ADMIN_ACCESS_LOG=/dev/stdout" \
 -e "KONG_PROXY_ERROR_LOG=/dev/stderr" \
 -e "KONG_ADMIN_ERROR_LOG=/dev/stderr" \
 -e "KONG_ADMIN_LISTEN=0.0.0.0:8001" \
 -e "KONG_ADMIN_GUI_URL=http://localhost:8002" \
 -e KONG_LICENSE_DATA \
 -p 9000:8000 \
 -p 9001:8001 \
 -p 9002:8002 \
 -p 9003:8003 \
 -p 9004:8004 \
 kong/kong-gateway:3.9.0.0

The Packet packet.txt (two empty lines at the end. The line-endings must be CRLF):

GET / HTTP/1.1
Accept: */*
Host: 127.0.0.0
Content-Type: application/x-www-form-urlencoded
Content-Type: application/x-www-form-urlencoded

The send.sh script:

#! /bin/bash
set -ue
SCRIPT_DIR=$( cd -- "$( dirname -- "${BASH_SOURCE[0]}" )" &> /dev/null && pwd )
PACKETS_DIR="$SCRIPT_DIR/packets"

cat "$PACKETS_DIR/$1" | netcat 127.0.0.1 9001 &
sleep 2
kill %1

Steps:

1. Run kong using bash start.sh
2. Run bash send.sh packet.txt

Misc

As I can see, lower method expects string in content_type variable (and receives it, if there is only one header with key Content-Type). However, if multiple lines Content-Type: ... provided, the content_type variable will contain a table.

Related source code:

• Lua:

  lapis/lapis/application.lua

  Line 487 in a13caec

  if string.find(content_type:lower(), "application/json", nil, true) then

• Moon:

  lapis/lapis/application.moon

  Line 428 in a13caec

  if string.find content_type\lower!, "application/json", nil, true