On 2/13/19 11:51 PM, Felix Fietkau wrote: > On 2019-02-13 23:15, Hauke Mehrtens wrote: >> This will build all executable as Position Independent Executables (PIE) >> by default. PIE executable can make full use of Address Space Layout >> Randomization (ASLR) because all sections can be placed at random >> offsets of the executed program. This makes it harder to exploit bugs >> in our binaries. >> >> This will increase the size of executable, libraries are already build >> position independent and their size will not change. >> >> This increases the size of the resulting images by about 3% on MIPS BE. >> I tested this with the default configuration for the lantiq xrx200 >> target. >> >> The size of the initramfs binaries increased by 2.88%: >> Without PIE: >> 5.303.716 openwrt-lantiq-xrx200-bt_homehub-v5a-initramfs-kernel.bin >> With PIE: >> 5.456.339 openwrt-lantiq-xrx200-bt_homehub-v5a-initramfs-kernel.bin >> >> With PIE activated the executable are getting bigger, here are some >> examples from the lantiq mips_24kc target: >> >> Without PIE: >> 112.309 /bin/opkg >> 299.061 /bin/busybox >> 456.549 /usr/sbin/wpad >> >> With PIE: >> 142.496 /bin/opkg (26.87% increase) >> 388.404 /bin/busybox (29.87% increase) >> 580.128 /usr/sbin/wpad (27.06% increase) >> >> With PIE activated the sections of the binaries are loaded to >> different offsets for each program instance like shown here: >> >> root@OpenWrt:/# cat /proc/self/maps >> 555c4000-55622000 r-xp 00000000 00:02 1030 /bin/busybox >> 55631000-55632000 r-xp 0005d000 00:02 1030 /bin/busybox >> 55632000-55633000 rwxp 0005e000 00:02 1030 /bin/busybox >> 55633000-55634000 rwxp 00000000 00:00 0 >> 77ee2000-77f04000 r-xp 00000000 00:02 331 /lib/libgcc_s.so.1 >> 77f04000-77f05000 r-xp 00012000 00:02 331 /lib/libgcc_s.so.1 >> 77f05000-77f06000 rwxp 00013000 00:02 331 /lib/libgcc_s.so.1 >> 77f06000-77f9a000 r-xp 00000000 00:02 329 /lib/libc.so >> 77fa9000-77fab000 rwxp 00093000 00:02 329 /lib/libc.so >> 77fab000-77fad000 rwxp 00000000 00:00 0 >> 7fb26000-7fb47000 rw-p 00000000 00:00 0 [stack] >> 7fefb000-7fefc000 r-xp 00000000 00:00 0 >> 7ff0a000-7ff0b000 r--p 00000000 00:00 0 [vvar] >> 7ff0b000-7ff0c000 r-xp 00000000 00:00 0 [vdso] >> root@OpenWrt:/# cat /proc/self/maps >> 5561d000-5567b000 r-xp 00000000 00:02 1030 /bin/busybox >> 5568a000-5568b000 r-xp 0005d000 00:02 1030 /bin/busybox >> 5568b000-5568c000 rwxp 0005e000 00:02 1030 /bin/busybox >> 5568c000-5568d000 rwxp 00000000 00:00 0 >> 77e8e000-77eb0000 r-xp 00000000 00:02 331 /lib/libgcc_s.so.1 >> 77eb0000-77eb1000 r-xp 00012000 00:02 331 /lib/libgcc_s.so.1 >> 77eb1000-77eb2000 rwxp 00013000 00:02 331 /lib/libgcc_s.so.1 >> 77eb2000-77f46000 r-xp 00000000 00:02 329 /lib/libc.so >> 77f55000-77f57000 rwxp 00093000 00:02 329 /lib/libc.so >> 77f57000-77f59000 rwxp 00000000 00:00 0 >> 7fd1c000-7fd3d000 rw-p 00000000 00:00 0 [stack] >> 7fefb000-7fefc000 r-xp 00000000 00:00 0 >> 7ff60000-7ff61000 r--p 00000000 00:00 0 [vvar] >> 7ff61000-7ff62000 r-xp 00000000 00:00 0 [vdso] >> root@OpenWrt:/# >> >> Signed-off-by: Hauke Mehrtens <[email protected]> >> --- >> >> I would like to get some comments if we should activate PIE by default. >> The advantage is that it will be harder to exploit OpenWrt, but on the >> other hand the binaries are getting bigger. We could also restrict this >> to some CPU types, but as targets share the binaries it is not really >> possible to do this based on the target. >> >> I am not sure if this should go into the next release or wait for later. >> >> This could also break some packages, as it is possible to activate PIE >> by default for some time many bugs are already fixed, but probably not >> all of them. > I think this is a lot of extra bloat. Maybe we can add a restricted PIE > mode where packages can opt-in individually?
So we should probably make it a chose with 3 options: 1. No PIE 2. Use PIE for exposed binaries 3. Use PIE for all binaries Then we need something in addition to the existing PKG_ASLR_PIE we already have to deactivate it. Do we want a generic name like this: PKG_CRITICAL or something specific to PIE: PKG_ASLR_PIE_PREFERED Hauke _______________________________________________ openwrt-devel mailing list [email protected] https://lists.openwrt.org/mailman/listinfo/openwrt-devel
