lol-fi/cve-2011-4862Educational patch implementation for FreeBSD telnetd buffer overflow (CVE-2011-4862) with step-by-step fix explanation and manual patching instructions.
I originally tried to use diff to make a patch. I patched it the way I thought it would be, before looking at the real patch. encrypt.patch is this original patch that I made with teh diff. However, when we tried applying this patch to freeBSD, it would not accept it.
Instead, we had to fetch the real patch. I then changed the patch to implement the fix the way I originally thought it should. This works because it puts the whole path into the patch.
In the patch, we simply check the length compared to MAXLENGTH. If it's bigger than that, set it to 0. This way, it falls into the case of len = 0, which errors out. This fixes it :-)
Here is an explanation of how to apply a patch in freeBSD. https://www.freebsd.org/security/advisories/FreeBSD-SA-11:08.telnetd.asc Simply use this patch instead of fetching the real one. It will work, and you will no longer be able to exploit the buffer overflow.
