Using OIDC with a custom bearer token header

The OIDC plugin fails when we send the bearer token in a custom header, how do we get the plugin to find the token? Custom header example: jefftoken-xyz: Bearer XXXXXXXXXX

Use the serverless pre-function plugin to change the header from jefftoken-xyz to Authorization.

1. Create some custom lua code to add a new header using the value from jefftoken-xyz and save the file as custom-auth.lua:

   local authhead = kong.request.get_header("jefftoken-xyz")
   
   kong.service.request.set_header("authorization", authhead)

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   Optionally, you can also delete the original header with the following additional line depending on whether the upstream still needs the original value:

   kong.service.request.clear_header("jefftoken-xyz")

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2. Add a pre-function plugin with config file custom-auth.lua (make sure your working directory has the custom-auth.lua file in it):

   curl -i -X POST http://localhost:8001/services/<your service name>/plugins \
   -H "kong-admin-token: <your admin token value>" \
   -F "name=pre-function" \
   -F "config.access[1]=@custom-auth.lua" \

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The OIDC plugin will now find the bearer token in the Authorization header.