Hauke Mehrtens <[email protected]> writes: > On 12/18/18 12:46 PM, Hauke Mehrtens wrote: >> On 12/17/18 1:54 AM, Dave Taht wrote: >>> >>> A pretty deep look at home MIPS and arm routers, and a surprising bug in >>> Linux/MIPS - by mudge and co: >>> >>> https://cyber-itl.org/2018/12/07/a-look-at-home-routers-and-linux-mips.html >>> >>> I have no idea if current openwrt, or what prior releases... are subject to >>> the problems they outline. >> >> In the second paper "Build Safety of Software in 28 Popular Home Router" >> [0] they checked the "security" of multiple popular devices, by checking >> if they activate ASLR, Non stack Exec, Relro and stack guards. The best >> device was the Linksys wrt32x and this is based on OpenWrt with not so >> many modifications. ;-) Just something like Samba downgrade to 3.0.37. >> The paper also wonders why the other Linksys devices like the wrt1900ac >> are much worse, but they probably do not use OpenWrt or a much older >> version. The GPL source code tar.gz of the Linksys wrt32x, begins with >> cloning from https://github.com/openwrt/openwrt.git >> >> >> It is also interesting how different this approve to security checking >> is to what the German BSI published in the "BSI TR-03148: Secure >> Broadband Router:" [1]. >> You can build a device which scores 100% in the one and 0% in the other, >> there is no overlap. ;-) >> >> Hauke >> >> >> [0]: >> https://cyber-itl.org/assets/papers/2018/build_safety_of_software_in_28_popular_home_routers.pdf >> [1]: >> https://www.bsi.bund.de/SharedDocs/Downloads/DE/BSI/Publikationen/TechnischeRichtlinien/TR03148/TR03148.pdf?__blob=publicationFile&v=2 > > It looks like they ran checksec from > http://github.com/slimm609/checksec.sh on the root file system of the > devices and came up with these results. The numbers for the Linksys > wrt32x look very similar to current OpenWrt master, even for MIPS > CPUs. > > I attached two outputs of checksec to this mail from the lantiq target > with a MIP24Kc CPU. One with master and the current default > configuration and one with master + activated ASLR configuration > option. > > You can generate these yourself like this: > ../checksec.sh/checksec -d build_dir/target-mips_24kc_musl/root-lantiq/
This might be a useful tool to make more obvious security issues to future builders of openwrt. > > ASLR increases the image size by about 2.8%: > Without ASLR: 5.386.965 bytes > With ASLR: 5.540.565 bytes To me this seems worth it on the larger flash sizes. > This is caused by increased user space binary size, see for example > busybox binary which is 7% bigger: > Without ASLR: 425.532 bytes > With ASLR: 457.336 bytes > > The fortified function count does not work with fortify-headers, but > only with glibc. With glibc some function calls are getting replaced > with calls to *_chk functions which are taking extra arguments, this > is done by some glibc header magic. For musl libc OpenWrt uses > fortify-headers which overwrites the original functions and inlined > some extra security checks into the calling application. The result > should be similar, so I assume that we have at least in most places > similar security for the glibc fortified functions. > I checked this by compiling an test application and checked the > assembler code, it contained some extra size checks. > > It looks like the detection does not work correctly for kernel modules. > > Currently RELRO is not activated for the following libraries: > root-lantiq/usr/lib/libbz2.so.1.0 > root-lantiq/usr/lib/libbz2.so.1.0.6 > root-lantiq/lib/libgcc_s.so.1 > this looks like a bug. > > For libgcc_s.so.1 also NX is disabled, which is not good. Hmm. Does gcc still actually contain executable code in this segment? > Some binaries do not use a stack canary, I assume that these binaries > just do not have an array on the stack which could be exploited. The > compiler adds stack canaries only to functions which the compiler > thinks need it. > > ASLR is deactivated for root-lantiq/sbin/vdsl_cpe_control, because > this application does not link any more when ASLR is activated, this > is a bug in the package build system. > > Hauke > > > _______________________________________________ > openwrt-devel mailing list > [email protected] > https://lists.openwrt.org/mailman/listinfo/openwrt-devel _______________________________________________ openwrt-devel mailing list [email protected] https://lists.openwrt.org/mailman/listinfo/openwrt-devel
