MCOOKIE

Section: Linux Programmer's Manual (1)
Updated: 25 September 1995
Index Return to Main Contents

NAME

mcookie - generate magic cookies for xauth

SYNOPSIS

mcookie [-v] [-f filename]

DESCRIPTION

mcookie generates a 128-bit random hexadecimal number for use with the X authority system. Typical usage:

: xauth add :0 . `mcookie`

The "random" number generated is actually the output of the MD5 message digest fed with various pieces of random information: the current time, the process id, the parent process id, the contents of an input file (if -f is specified), and several bytes of information from the first of the following devices which is present: /dev/random, /dev/urandom, files in /proc, /dev/audio.

BUGS

The entropy in the generated 128-bit is probably quite small (and, therefore, vulnerable to attack) unless a non-pseudorandom number generator is used (e.g., /dev/random under Linux).

It is assumed that none of the devices opened will block.

FILES

/dev/random
/dev/urandom
/dev/audio
/proc/stat
/proc/loadavg

AVAILABILITY

The mcookie command is part of the util-linux-ng package and is available from ftp://ftp.kernel.org/pub/linux/utils/util-linux-ng/.