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On Monday 23 January 2012 15:12:47 Francesco Riosa wrote: |
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> 2012/1/23 Mike Gilbert: |
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> > On Mon, Jan 23, 2012 at 2:57 PM, Jason A. Donenfeld wrote: |
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> >> To check for PIE, |
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> >> |
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> >> readelf -h /bin/su | grep Type |
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> >> |
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> >> If it says EXEC, no PIE. If it says DYN, yes PIE. |
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> > |
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> > I'm asking "how does one enable PIE/ASLR", not how to check if it is |
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> > enabled already. |
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> |
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> - PIE should be -fPIC also for the executable, not only for the .so |
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> (has a performance impact) |
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not entirely sure what you're saying here. i'll clarify in general: |
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- build all code going into shared libraries with -fPIC |
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(regardless of hardening, this is Gentoo policy today) |
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- build code going into executables with -fPIE |
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(this is what hardened does, not default Gentoo systems) |
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you could build all code (including executables) with -fPIC, but that has |
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useless overhead compared to -fPIE. it's small but not insignificant. |
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> - ASLR you need "hardened" use for gcc, and the toolchain, pax kernel help |
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> too |
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the hardened toolchain "helps", but it is not required. ASLR is in the |
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mainline Linux kernel and iirc, enabled by default. it is already operating |
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on all shared libraries because those are PIC. |
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-mike |
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