local crypto = require('crypto')

local print = ngx.say
local hmacdigest = crypto.hmac.digest
local base64 = ngx.encode_base64
local headers = ngx.req.get_headers()

ngx.header.content_type = 'text/plain';
for k, v in pairs(headers) do
    print(string.format("%s\t%s: %s", base64(hmacdigest('sha256', v, k, true)), k, v))
end