Full Disclosure mailing list archives
Re: new class of printf issue: int overflow
From: Thomas <tom () electric-sheep org>
Date: Thu, 11 Jan 2007 09:55:29 +0100
Hello Felix. Am Donnerstag, 11. Januar 2007 02:00 schrieb Felix von Leitner:
This is about two issues. First: abs within vasprintf. I just read some gnupg source code and stumbled upon their vasprintf implementation.
Did you told them about it?
Second issue: int overflow in *printf: But that got me thinking. *printf return an int, and it's supposed to be the number of chars written. So a typical idiom is size_t memory_needed=snprintf(NULL,0,format_string,...); char* ptr=malloc(memory_needed+1); sprintf(ptr,format_string,...);
This is nothing new. It is documented in the man-page and in the libc sources. By coincidence I found such a bug while doing a code review a few weeks ago. But in this case the return value was used in calculating an pointer offset and using this pointer again in sprintf(). At the end the result was an overflow. :-) Bye Thomas -- Tom <tom () electric-sheep org> fingerprint = F055 43E5 1F3C 4F4F 9182 CD59 DBC6 111A 8516 8DBF _______________________________________________ Full-Disclosure - We believe in it. Charter: http://lists.grok.org.uk/full-disclosure-charter.html Hosted and sponsored by Secunia - http://secunia.com/
Current thread:
- new class of printf issue: int overflow Felix von Leitner (Jan 10)
- Re: new class of printf issue: int overflow Pierre Habouzit (Jan 11)
- Re: new class of printf issue: int overflow Felix von Leitner (Jan 11)
- Re: new class of printf issue: int overflow Pierre Habouzit (Jan 11)
- Re: new class of printf issue: int overflow Pierre Habouzit (Jan 11)
- Re: new class of printf issue: int overflow Felix von Leitner (Jan 11)
- Re: new class of printf issue: int overflow Pierre Habouzit (Jan 11)
- Re: new class of printf issue: int overflow Mihai Dontu (Jan 11)
- Re: new class of printf issue: int overflow Thomas (Jan 11)
- Re: new class of printf issue: int overflow Felix von Leitner (Jan 11)
- Re: new class of printf issue: int overflow Thomas (Jan 11)
- Re: new class of printf issue: int overflow Felix von Leitner (Jan 11)