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Date: Sat, 15 Sep 2012 03:13:42 +0400
From: Solar Designer <solar@...nwall.com>
To: john-dev@...ts.openwall.com
Subject: "single crack" missing candidates (was: Office2john)

magnum -

On Fri, Sep 14, 2012 at 11:22:53PM +0200, magnum wrote:
> Is there any chance a very loaded GECOS field can "overwrite" the login field or otherwise screw Single mode from getting a candidate from that field?

Normally, no.

> I tried to spot any limitation on GECOS stuff other than LINE_BUFFER_SIZE but did not find any.

There are also LDR_WORDS_MAX and SINGLE_WORDS_PAIR_MAX, but they should
not cause the behavior you're describing.

Does your copy of single.c include these lines? -

/*
 * We use "short" for buffered key indices and "unsigned short" for buffered
 * key offsets - make sure these don't overflow.
 */
	if (key_count > 0x8000)
		key_count = 0x8000;
	while (key_count > 0xffff / length + 1)
		key_count >>= 1;

Is "offset" in "struct db_keys_hash_entry" actually "unsigned short"
(rather than simply "short")?

There were fairly recent fixes in this area.  Without them, GPU formats
with large min_keys_per_crypt settings could result in "single crack"
missing candidate passwords.

Alexander

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