Comment 1 for bug 1890814

macOS already handles the missing space before M=, extract from :
https://opensource.apple.com/source/ppp/ppp-862.120.2/Helpers/pppd/chap_ms.c.auto.html

 //we'll allow the missing-space case from the server, even though
 //it's non-conforming to spec!
 dbglog("Rcvd non-conforming MSCHAPv2 Success packet, len=%d", len);
 if(len >= 2 && !strncmp((char*)msg, "M=", 2))
  msg += 2;
 else
 {
  error("MS-CHAPv2 Success packet is badly formed.");
  return 0;
 }