full-disclosure - Re: Python 2.5 (Modules/zlib) minigzip local buffer overflow vulnerability

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Message-Id: <200703160220.07136.ismail@pardus.org.tr>
Date: Fri, 16 Mar 2007 02:20:06 +0200
From: Ismail Dönmez <ismail@...dus.org.tr>
To: metaur@...ia.com
Cc: full-disclosure@...ts.grok.org.uk
Subject: Re: Python 2.5 (Modules/zlib) minigzip local
	buffer overflow vulnerability

On Friday 16 March 2007 00:00:23 Ulf Harnhammar wrote:
> > Using strncpy is just strcpy + strlen
> > anyway it can't have a big speed impact or anything.
>
> That's not really true. If you check the Linux manpage for strncpy(3),
> it says:
>
>        char *strncpy(char *dest, const char *src, size_t n);
> [blah]
>        In the case where the length of src is less than that of n, the
> remain- der of dest will be padded with null bytes.
>
> "The C Programming Language" agrees:
>
> "Pad with '\0's if t has fewer than n characters."

Argh I forgot about the NULL padding, you are correct.

> Thus, replacing strcpy(3) calls with strncpy(3) can have definite
> impacts on performance.

But the question is how big impact? Its a security/speed trade-off. 

Regards.

-- 
Happiness in intelligent people is the rarest thing I know. (Ernest Hemingway)

Ismail Donmez ismail (at) pardus.org.tr
GPG Fingerprint: 7ACD 5836 7827 5598 D721 DF0D 1A9D 257A 5B88 F54C
Pardus Linux / KDE developer

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