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Last updated March 2020


msys.validate.opendkim.get_sig_keysize — Fetch the size of the key used to generate a signature



dkim_sig: userdata, DKIM_SIGINFO type


This function fetches the size of the key used to generate a signature. Use msys.validate.opendkim.get_num_sigs and msys.validate.opendkim.get_sig to get a DKIM_SIGINFO object to pass to this function. For a description of the DKIM_SIGINFO object, see DKIM_DSIGINFO.

This function requires the opendkim module.

Enable this function with the statement require('msys.validate.opendkim');.

This function returns the size of the signing key in bits and the DKIM status DKIM_STAT.

The DKIM_STAT can be one of the following values:

  • DKIM_STAT_OK – successful completion

  • DKIM_STAT_BADSIG – signature did not match headers and body

  • DKIM_STAT_NOSIG – no signature present

  • DKIM_STAT_NOKEY – no key available for verifying

  • DKIM_STAT_CANTVRFY – cannot get key for verifying

  • DKIM_STAT_SYNTAX – message is not in valid syntax

  • DKIM_STAT_NORESOURCE – resource unavailable

  • DKIM_STAT_INTERNAL – internal error

  • DKIM_STAT_REVOKED – signing key revoked

  • DKIM_STAT_INVALID – invalid parameter(s)

  • DKIM_STAT_NOTIMPLEMENT – function not implemented

  • DKIM_STAT_KEYFAIL – key retrieval failed (try again later)

  • DKIM_STAT_CBREJECT – callback requested message rejection

  • DKIM_STAT_CBTRYAGAIN – callback cannot complete (try again later)

  • DKIM_STAT_CBERROR – unspecified callback error

local mod = {};

function mod:validate_data(msg, accept, vctx)
  local num = 0;
  local stat;
  local dkim_sig;
  local dkim = msys.validate.opendkim.verify(msg);
  num, stat = msys.validate.opendkim.get_num_sigs(dkim);
  -- create loop controlled by num 
  if num > 0 then
    for i = 0, num-1 do
      dkim_sig = msys.validate.opendkim.get_sig(dkim, i);
      -- now do something with the signature
      local size = msys.validate.opendkim.get_sig_keysize(dkim_sig);
      if size < 1024 then
  return msys.core.VALIDATE_CONT;
msys.registerModule("test_opendkim", mod);

See Also

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