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Date: Thu, 22 Jan 2009 05:09:38 +0300
From: Solar Designer <solar@...nwall.com>
To: john-users@...ts.openwall.com
Subject: Re: Programming External azAZ09-5 without filter

On Thu, Jan 22, 2009 at 01:50:05AM +0000, Ruben Lara wrote:
> I'm trying to program an external mode of azAZ09 charsets of 5 length.
> I want generate words cleanly, so i won't need use filter function() and earn time.
> It's possible that?

Indeed.

> My try is next:
...
> This produce 5 length words but can't avoid not alphanum characters...
> Where is my mistake?

I'm sorry, I did not review your code.

The most straightforward and generic way to achieve what you need is by
modifying the DumbForce external mode sample included in the bundled
john.conf file with recent versions of JtR.  Here it is, modified to
achieve what you wanted:

[List.External:DumbForce-azAZ09-5]
int maxlength;		// Maximum password length to try
int last;		// Last character position, zero-based
int lastid;		// Character index in the last position
int id[0x7f];		// Current character indices for other positions
int charset[0x100], c0;	// Character set

void init()
{
	int minlength;
	int i, c;

	minlength = 5;	// Initial password length to try, must be at least 1
	maxlength = 5;	// Must be at least same as minlength

/* This defines the character set. */
	i = 0;
	c = 'a';
	while (c <= 'z')
		charset[i++] = c++;
	c = 'A';
	while (c <= 'Z')
		charset[i++] = c++;
	c = '0';
	while (c <= '9')
		charset[i++] = c++;

/* Zero-terminate it, and cache the first character */
	charset[i] = 0;
	c0 = charset[0];

	last = minlength - 1;
	i = 0;
	while (i <= last) {
		id[i] = 0;
		word[i++] = c0;
	}
	lastid = -1;
	word[i] = 0;
}

void generate()
{
	int i;

/* Handle the typical case specially */
	if (word[last] = charset[++lastid]) return;

	lastid = 0;
	word[i = last] = c0;
	while (i--) {			// Have a preceding position?
		if (word[i] = charset[++id[i]]) return;
		id[i] = 0;
		word[i] = c0;
	}

	if (++last < maxlength) {	// Next length?
		id[last] = lastid = 0;
		word[last] = c0;
	} else				// We're done
		word = 0;
}

void restore()
{
	int i, c;

/* Calculate the current length and infer the character indices */
	last = 0;
	while (c = word[last]) {
		i = 0; while (charset[i] != c && charset[i]) i++;
		if (!charset[i]) i = 0;	// Not found
		id[last++] = i;
	}
	lastid = id[--last];
}

Indeed, it is possible to achieve the same with less code, but then the
code would not be as generic and it would be harder to modify for other
charsets.

If you ever need something like this, but with different charsets for
different character positions, then the sample to modify would be
KnownForce instead of DumbForce.

Alexander

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