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Date: Wed, 6 Jul 2016 17:27:33 +0200
From: magnum <john.magnum@...hmail.com>
To: john-dev@...ts.openwall.com
Subject: rules.c bug/feature
Solar,
While playing with some old contest rules I found a bug in John that's
not Jumbo-specific: Apparently it lacks some checks so a 'ddd' rule will
blow the destination buffer even at moderate input lengths (eg. 50).
The implications are a smashed rules_data.classes array which may
eventually lead to a segfault but I think it may also just "seem to
work" although subsequent rules will actually execute incorrectly.
I think the best fix is to quietly truncate the copy so ddd (and even
dddd and so on) will work fine with short enough words? Here is a fix
that seem to work but not much tested and I really did not count the
fence posts very carefully:
diff --git a/src/rules.c b/src/rules.c
index d20d1d5..0bb525b 100644
--- a/src/rules.c
+++ b/src/rules.c
@@ -441,7 +441,9 @@ char *rules_apply(char *word, char *rule, int split,
char *last)
break;
case 'd':
- memcpy(in + length, in, length);
+ if (rules_max_length - length > 0)
+ strnzcpy(in + length, in,
+ rules_max_length - length);
in[length <<= 1] = 0;
break;
I'll wait with fixing Jumbo until you comment.
magnum
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