Date: Sat, 6 Oct 2018 21:46:36 +0300 From: Konstantin Belousov <kostikbel@gmail.com> To: freebsd-security@freebsd.org Subject: Re: [FreeBSD-Announce] FreeBSD Security Advisory FreeBSD-SA-18:12.elf Message-ID: <20181006184636.GT5335@kib.kiev.ua> In-Reply-To: <20181006182104.GS5335@kib.kiev.ua> References: <20180912054309.61C6B13269@freefall.freebsd.org> <20181006173525.GC813@lena.kiev> <20181006182104.GS5335@kib.kiev.ua>
next in thread | previous in thread | raw e-mail | index | archive | help
On Sat, Oct 06, 2018 at 09:21:04PM +0300, Konstantin Belousov wrote: > On Sat, Oct 06, 2018 at 08:35:26PM +0300, Lena@lena.kiev.ua wrote: > > > Insufficient validation was performed in the ELF header parser, and malformed > > > or otherwise invalid ELF binaries were not rejected as they should be. > > > > What is invalid in the /usr/local/share/google-earth/googleearth-bin > > binary of the port google-earth-7.1.5.1557,3 ? > > > > FreeBSD 11.2-RELEASE-p4 Sep 27 GENERIC i386, the binary: > > https://drive.google.com/file/d/1SgHk8ijSp2F9UcQGlx44psT832TdIEL0/view > > > > ~ $ googleearth > > Invalid PT_INTERP > > exec: ./googleearth-bin: Exec format error > > ~ $ readelf --program-headers /usr/local/share/google-earth/googleearth-bin > > > > Elf file type is EXEC (Executable file) > > Entry point 0x8048650 > > There are 8 program headers, starting at offset 52 > > > > Program Headers: > > Type Offset VirtAddr PhysAddr FileSiz MemSiz Flg Align > > PHDR 0x000034 0x08048034 0x08048034 0x00100 0x00100 R E 0x4 > > INTERP 0x000134 0x08048134 0x08048134 0x00011 0x00011 R 0x1 > > [Requesting program interpreter: /lib/ld-linux.so.2] > As you see, the file delcares that file/memory length of the interpreter > name' segment is 0x11 == 16 decimal. But the string does not end on > byte 16, which is not NUL. We tighten the checks and do require that > PT_INTERP string is valid by checking that it is NUL-terminated at the > offset declared by the size. As emaste pointed out, I am off by one, i.e. replace 16 by 17 in the text above.
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?20181006184636.GT5335>