implement Countersigner; include "sys.m";	sys: Sys; include "draw.m";	draw: Draw; include "keyring.m";	kr: Keyring; include "msgio.m";	msgio: Msgio; include "security.m"; Countersigner: module{	init:	fn(ctxt: ref Draw->Context, argv: list of string);}; stderr, stdin, stdout: ref Sys->FD; init(nil: ref Draw->Context, nil: list of string){	sys = load Sys Sys->PATH;	kr = load Keyring Keyring->PATH;	msgio = load Msgio Msgio->PATH;	msgio->init(); 	stdin = sys->fildes(0);	stdout = sys->fildes(1);	stderr = sys->fildes(2); 	sys->pctl(Sys->FORKNS, nil);	if(sys->chdir("/keydb") < 0){		sys->fprint(stderr, "countersigner: no key database\n");		raise "fail:no keydb";	} 	# get boxid	buf := msgio->getmsg(stdin);	if(buf == nil){		sys->fprint(stderr, "countersigner: client hung up\n");		raise "fail:hungup";	}	boxid := string buf; 	# read file	file := "countersigned/"+boxid;	fd := sys->open(file, Sys->OREAD);	if(fd == nil){		sys->fprint(stderr, "countersigner: can't open %s: %r\n", file);		raise "fail:bad boxid";	}	blind := msgio->getmsg(fd);	if(blind == nil){		sys->fprint(stderr, "countersigner: can't read %s\n", file);		raise "fail:no blind";	} 	# answer client	msgio->sendmsg(stdout, blind, len blind);}