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Re: out of bounds stack access in idn tool

From: Simon Josefsson
Subject: Re: out of bounds stack access in idn tool
Date: Mon, 10 Aug 2015 10:34:49 +0200
User-agent: Gnus/5.130014 (Ma Gnus v0.14) Emacs/24.4 (gnu/linux)

Simon Josefsson <address@hidden> writes:

> Hanno Böck <address@hidden> writes:
>> Hi,
>> When passing the attacked file (libidn-oob-stack-read-main) to the idn
>> command line tool this will cause an out of bounds stack access. This
>> can be seen with either valgrind or by recompiling idn with address
>> sanitizer. The input consists of a random character, a newline and a
>> zero byte.
>> The error happens in the function main in this code
>>       if (readbuf[strlen (readbuf) - 1] == '\n')
>>      readbuf[strlen (readbuf) - 1] = '\0';
>> If readbuf is a zero byte string this won't work. I have attached a
>> patch how to prevent this. Not sure if this is the best way, but it
>> prevents the oob access.
> Thank you for the report.  I believe idn should use getline instead of
> this funky fixed-buffer fgets+hacks approach.  I'll try to implement it.

Hi Hanno.

I have implemented this solution now -- please see these commits:;a=commitdiff;h=570e68886c41c2e765e6218cb317d9a9a447a041;a=commitdiff;h=8b6b44f1bffbdae98d8791434bf5e77da74acbb4

If you have any comments or thoughts, please let me know.


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