validation rule for jwt_secrets.rsa_public_key is inconsistent between the write side and consume side

[jizhilong]

Is there an existing issue for this?

• I have searched the existing issues

Kong version ($ kong version)

2.2.2+

Current Behavior

No response

Expected Behavior

No response

Steps To Reproduce

No response

Anything else?

• on the write side, jwt_secrets.rsa_public_key MUST be content of a plain text pem file when asymmetric crypto is used.

    entity_checks = {
      { conditional = { if_field = "algorithm",
                        if_match = {
                          match_any = { patterns = { "^RS256$",
                                                     "^RS384$",
                                                     "^RS512$",
                                                     "^PS256$",
                                                     "^PS384$",
                                                     "^PS512$",
                                                     "^EdDSA$",
                                                     }, },
                        },
                        then_field = "rsa_public_key",
                        then_match = {
                          required = true,
                          custom_validator = validate_ssl_key,
                        },
                      },

• while on the consume side, jwt_secrets.rsa_public_key MAY get base64 decoded when plugin_conf.secret_is_base64 is switched on, with no regard to whether the crypto used is symmetric or asymmetric

  local jwt_secret_value = algorithm ~= nil and algorithm:sub(1, 2) == "HS" and
                           jwt_secret.secret or jwt_secret.rsa_public_key

  if conf.secret_is_base64 then
    jwt_secret_value = jwt:base64_decode(jwt_secret_value)
  end

In scenarios with algorithm='RS256' and conf.secret_is_base64=true, jwt:base64_decode(jwt_secret_value) will always fail, which lead to issues like #2891 .

We can work around this problem by switching off secret_is_base64, just like @smileMrLee did in #2891 . Or we can make a fix to jwt/handler.lua by check the necessity of base64 decoding with regard to both algorithm and conf.secret_is_base64:

  local is_symmetric_algorithm = algorithm ~= nil and algorithm:sub(1, 2) == "HS"
  local jwt_secret_value =  is_symmetric_algorithm and jwt_secret.secret or jwt_secret.rsa_public_key

  if is_symmetric_algorithm and conf.secret_is_base64 then
    jwt_secret_value = jwt:base64_decode(jwt_secret_value)
  end

[samugi]

Hello @jizhilong, thank you for opening this issue. It appears you have a solution coded for this problem, would you consider opening a pull request? Thank you!

[jizhilong]

@samugi glad to help, the PR is ready at #13717 now

[jizhilong]

@samugi can you help to review the PR, thanks.