[QUESTION] When switching to PKCE flow there are error in openidc_load_jwt_and_verify_crypto() and openidc_load_and_validate_jwt_id_token() methods

[madonar]

Environment

• lua-resty-openidc version : 1.21.4.1
• OpenID Connect provider : PhenixID

Expected behaviour

We are switching from "code" flow to the "pkce" flow for security reasons. When doing so we see errors and are unable to proceed with the implementation. Is there someone who can point out the mistake and help us in this switching?

When a user starts to reach a website the following happens(SSO),
authorization endpoint -> success response
Token endpoint -> success response
jwks endpoint -> success response

After receiving the JWKS, the JWT verification should be successful without errors and the flow should proceed to be able to obtain a user token from the userinfo endpoint. How can I achieve this?

Actual behaviour

After receiving the response from jwks endpoint, the below errors are seen in logs, especially the line "RSA key with id 2LhxLYAqxej8ltPfuqPb1SLP-7g" is the same(including the same id(from cache or similar?)) for several different SSO attempts to log in to the website. Is the RSA key cached and reused everytime? How can we fix this?

[error] 1234953#1234953: *2 [lua] openidc.lua:1006: openidc_load_jwt_and_verify_crypto(): RSA key with id 2LhxLYAqxej8ltPfuqPb1SLP-7g not found,
[error] 1234953#1234953: *2 [lua] openidc.lua:1066: openidc_load_and_validate_jwt_id_token(): id_token '' signature verification failed,

Minimized example

local opts = {
redirect_uri = "/sso/ebx",
discovery = "https://replacedforsecurityreasons-acceptance.se/oidc-basic-pkce-tenant/.well-known/openid-configuration",
client_id = "replacedforsecurityreasons",
client_secret = "replacedforsecurityreasons",
ssl_verify = "no",
timeout = 500,
use_pkce = true,
scope = "openid",
use_nonce = false,
accept_none_alg = true,
keepalive = "yes",
jwt_verification_cache_ignore = true
}
local res, err, tgt_url, session = require("resty.openidc").authenticate(opts)

[madonar]

debug.log
Attaching the logs(debug mode) with "replacedforsecurityreasons" text replacing IP, URL & large binary data.