Lua can't import a module and says file not found but the file exists - lua

Question

i'm trying to run a lua script from inside haproxy that imports the "pgmoon" library. i can import pgmoon and get as far as opening a socket, but then i run into this:
[ALERT] 082/234313 (8) : Lua function 'queue-request': runtime error: /usr/local/share/lua/5.3/pgmoon/init.lua:269: module 'pgmoon.crypto' not found:
no field package.preload['pgmoon.crypto']
no file '/usr/local/share/lua/5.3/pgmoon/crypto.lua'
no file '/usr/local/share/lua/5.3/pgmoon/crypto/init.lua'
no file '/usr/local/lib/lua/5.3/pgmoon/crypto.lua'
no file '/usr/local/lib/lua/5.3/pgmoon/crypto/init.lua'
no file '/usr/share/lua/5.3/pgmoon/crypto.lua'
no file '/usr/share/lua/5.3/pgmoon/crypto/init.lua'
no file './pgmoon/crypto.lua'
no file './pgmoon/crypto/init.lua'
no file '/usr/local/lib/lua/5.3/pgmoon/crypto.so'
no file '/usr/lib/x86_64-linux-gnu/lua/5.3/pgmoon/crypto.so'
no file '/usr/lib/lua/5.3/pgmoon/crypto.so'
no file '/usr/local/lib/lua/5.3/loadall.so'
no file './pgmoon/crypto.so'
no file '/usr/local/lib/lua/5.3/pgmoon.so'
no file '/usr/lib/x86_64-linux-gnu/lua/5.3/pgmoon.so'
no file '/usr/lib/lua/5.3/pgmoon.so'
no file '/usr/local/lib/lua/5.3/loadall.so'
no file './pgmoon.so' from [C] global 'require', /usr/local/share/lua/5.3/pgmoon/init.lua:269 C function line 267 ..., /usr/local/share/lua/5.3/pgmoon/init.lua:211 method 'connect', /usr/local/haproxy/queue-request.lua:38 C function line 25.
however, there is a file at /usr/local/share/lua/5.3/pgmoon/crypto.lua, this is what ls shows:
# ls -la /usr/local/share/lua/5.3/pgmoon/
total 60
drwxr-xr-x 1 root root 4096 Mar 24 23:42 .
drwxr-xr-x 1 root root 4096 Mar 24 23:00 ..
-rw-r--r-- 1 root root 2880 Mar 24 23:00 arrays.lua
-rw-r--r-- 1 root root 1130 Mar 24 23:00 bit.lua
-rw-r--r-- 1 root root 1587 Mar 24 23:00 cqueues.lua
-rw-r--r-- 1 root root 654 Mar 24 23:00 crypto.lua
-rw-r--r-- 1 root root 2084 Mar 24 23:00 hstore.lua
-rw-r--r-- 1 root root 20127 Mar 24 23:00 init.lua
-rw-r--r-- 1 root root 665 Mar 24 23:00 json.lua
-rw-r--r-- 1 root root 2728 Mar 24 23:42 socket.lua
-rw-r--r-- 1 root root 457 Mar 24 23:00 util.lua
i could see it being permissions-related, if the haproxy user couldn't access a root owned file, but by the time it gets here it's already executed init.lua which has imported socket.lua and they've all got the same permissions...
Anybody know why lua thinks there is no file at crypto.lua?

Answer 1

I guess that you have haproxy configured with chroot and there actually isn't a file at /usr/local/share/lua/5.3/pgmoon/crypto.lua - in the chroot you haproxy runs in.
The require('pgmoon.crypto') in init.lua is within a function and probably tries to run long after Haproxy and lua initialization - and the root change.
And somewhat (un)relatedly - you can probably expect other problems with the pgmoon not being aware of haproxy, eg. its use of luasocket and not the haproxy-provided replacement: https://www.haproxy.com/blog/5-ways-to-extend-haproxy-with-lua/
The Socket class is a replacement for the standard Lua Socket class and is compatible with HAProxy’s non-blocking nature. When you want to use socket functions in your actions, you must use this class.