simple-sso/src/ssso_base64.lua

local b64 = require("ngx.base64") -- only contains URL-variants

if not b64["decode_base64"] then
  b64.decode_base64 = function(base64)
    base64 = base64:gsub("%+", "-")
    base64 = base64:gsub("/", "_")
    return b64.decode_base64url(base64)
  end
end

if not b64["encode_base64"] then
  b64.encode_base64 = function(plaintext)
    local plain, err = b64.encode_base64url(plaintext)
    if not plain then
      return nil, err
    end
    plain = plain:gsub("_", "/")
    return plain:gsub("%-", "+"), nil
  end
end

return b64