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Special Forums Cybersecurity swordfish --- a password generator Post 302081450 by Perderabo on Tuesday 25th of July 2006 11:19:23 AM
Old 07-25-2006
I will post a new copy of swordfish making these changes:
Code:
In the weak_start_tigershark function: the line in green is new.

function weak_start_tigershark
{
        typeset -i  i final duration
        ((final=SECONDS+2))

        while((SECONDS < final)) ; do
                i=$RANDOM
        done

        ((Carry=0))
        ((X0=$$))
        ((X1=RANDOM))
        ((X2=RANDOM))
        ((X3=RANDOM))
        ((DEBUG)) && echo weakstart X3=$X3 X2=$X2 X1=$X1 X0=$X0 Carry=$Carry
        Sum=0
        ((Stigershark=Stigershark+1))
        return 0
}


In the Main section: The lines in red go away:

if [[ $Entropy = $ZeroEntropy ]] ; then
                echo "********************************" >&2
                echo "*                              *" >&2
                echo "*  Warning:  Entropy is zero!  *" >&2
                echo "*                              *" >&2
                echo "********************************" >&2
                echo generating weak entropy... >&2
                weak_start_tigershark
                status_tigershark
                entropy_generator 1 array
                echo  Entropy = ${Entropy}
                NeedMoreEntropy=1
fi

It is too early in the program to call status_tigershark since linecount has not be initialized and also it is sending unsolicted output to stdout. And that "echo Entropy" should have been directed to stderr as well. The remaining error message should be enough to call attention to the fact that swordfish is not operating in an optimum manner. And the user can always turn on debug mode for more output.

Yes, my intent is that swordfish be invoked always in the same directory. swordfish maintains an entropy file which is random data used to initialize the internal random number generator. But the first time the random number generator is called, there won't be an entropy file. So swordfish will initialize the RNG from /dev/urandom or /dev/random. If neither of those is available then swordfish is stuck with no decent source of initial random numbers. So it invokes the internal ksh RANDOM routine to get a few random numbers and it uses its current PID for one more random number. It first spends a couple of seconds burning off some of KSH's random numbers so it is not as bad as it might otherwise be. But it still complains about the situation. This is what is happening to you. Even HP-UX finally implemented /dev/random in 11.23. What OS are you using without a /dev/random?

If you really want to call swordfish from arbitrary directories, you could change the line:
ENTROPYFILE=swordfish.ent
to be an obsolute path to your entropy file. But remember, if other people can read your entropy file, they might be able to predict the passwords it
will generate.
 

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RANDOM(4)						   BSD Kernel Interfaces Manual 						 RANDOM(4)

NAME
random , urandom -- random data source devices. SYNOPSIS
pseudo-device random DESCRIPTION
The random device produces uniformly distributed random byte values of potentially high quality. To obtain random bytes, open /dev/random for reading and read from it. The same random data is also available from getentropy(2). Using the getentropy(2) system call interface will provide resiliency to file descriptor exhaustion, chroot, or sandboxing which can make /dev/random unavailable. Additionally, the arc4random(3) API provides a fast userspace random number generator built on the random data source and is preferred over directly accessing the system's random device. /dev/urandom is a compatibility nod to Linux. On Linux, /dev/urandom will produce lower quality output if the entropy pool drains, while /dev/random will prefer to block and wait for additional entropy to be collected. With Yarrow, this choice and distinction is not necessary, and the two devices behave identically. You may use either. The random device implements the Yarrow pseudo random number generator algorithm and maintains its entropy pool. The kernel automatically seeds the algorithm with additional entropy during normal execution. FILES
/dev/random /dev/urandom HISTORY
A random device appeared in the Linux operating system. Darwin September 6, 2001 Darwin
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