From: Andy Lutomirski <luto@amacapital.net>
To: Kristen Carlson Accardi <kristen@linux.intel.com>
Cc: tglx@linutronix.de, mingo@redhat.com, bp@alien8.de,
hpa@zytor.com, arjan@linux.intel.com, keescook@chromium.org,
rick.p.edgecombe@intel.com, x86@kernel.org,
linux-kernel@vger.kernel.org,
kernel-hardening@lists.openwall.com
Subject: Re: [RFC PATCH 04/11] x86/boot/KASLR: Introduce PRNG for faster shuffling
Date: Wed, 5 Feb 2020 17:11:11 -0800 [thread overview]
Message-ID: <487F8A1B-3FBC-4A0E-B6EC-5FE0F70D18DD@amacapital.net> (raw)
In-Reply-To: <20200205223950.1212394-5-kristen@linux.intel.com>
> On Feb 5, 2020, at 2:39 PM, Kristen Carlson Accardi <kristen@linux.intel.com> wrote:
>
> From: Kees Cook <keescook@chromium.org>
>
> This *might* improve shuffling speed at boot. Possibly only marginally.
> This has not yet been tested, and would need to have some performance
> tests run to determine if it helps before merging.
Ugh, don’t do this. Use a real DRBG. Someone is going to break the construction in your patch just to prove they can.
ChaCha20 is a good bet.
>
> (notes from Kristen) - initial performance tests suggest that any
> improvement is indeed marginal. However, this code is useful
> for using a known seed.
>
> Signed-off-by: Kees Cook <keescook@chromium.org>
> Signed-off-by: Kristen Carlson Accardi <kristen@linux.intel.com>
> ---
> arch/x86/boot/compressed/kaslr.c | 4 +--
> arch/x86/include/asm/kaslr.h | 3 +-
> arch/x86/lib/kaslr.c | 50 +++++++++++++++++++++++++++++++-
> arch/x86/mm/init.c | 2 +-
> arch/x86/mm/kaslr.c | 2 +-
> 5 files changed, 55 insertions(+), 6 deletions(-)
>
> diff --git a/arch/x86/boot/compressed/kaslr.c b/arch/x86/boot/compressed/kaslr.c
> index d7408af55738..ae4dce76a9bd 100644
> --- a/arch/x86/boot/compressed/kaslr.c
> +++ b/arch/x86/boot/compressed/kaslr.c
> @@ -598,7 +598,7 @@ static unsigned long slots_fetch_random(void)
> if (slot_max == 0)
> return 0;
>
> - slot = kaslr_get_random_long("Physical") % slot_max;
> + slot = kaslr_get_random_seed("Physical") % slot_max;
>
> for (i = 0; i < slot_area_index; i++) {
> if (slot >= slot_areas[i].num) {
> @@ -880,7 +880,7 @@ static unsigned long find_random_virt_addr(unsigned long minimum,
> slots = (KERNEL_IMAGE_SIZE - minimum - image_size) /
> CONFIG_PHYSICAL_ALIGN + 1;
>
> - random_addr = kaslr_get_random_long("Virtual") % slots;
> + random_addr = kaslr_get_random_seed("Virtual") % slots;
>
> return random_addr * CONFIG_PHYSICAL_ALIGN + minimum;
> }
> diff --git a/arch/x86/include/asm/kaslr.h b/arch/x86/include/asm/kaslr.h
> index db7ba2feb947..47d5b25e5b11 100644
> --- a/arch/x86/include/asm/kaslr.h
> +++ b/arch/x86/include/asm/kaslr.h
> @@ -2,7 +2,8 @@
> #ifndef _ASM_KASLR_H_
> #define _ASM_KASLR_H_
>
> -unsigned long kaslr_get_random_long(const char *purpose);
> +unsigned long kaslr_get_random_seed(const char *purpose);
> +unsigned long kaslr_get_prandom_long(void);
>
> #ifdef CONFIG_RANDOMIZE_MEMORY
> void kernel_randomize_memory(void);
> diff --git a/arch/x86/lib/kaslr.c b/arch/x86/lib/kaslr.c
> index 2b3eb8c948a3..41b5610855a3 100644
> --- a/arch/x86/lib/kaslr.c
> +++ b/arch/x86/lib/kaslr.c
> @@ -46,7 +46,7 @@ static inline u16 i8254(void)
> return timer;
> }
>
> -unsigned long kaslr_get_random_long(const char *purpose)
> +unsigned long kaslr_get_random_seed(const char *purpose)
> {
> #ifdef CONFIG_X86_64
> const unsigned long mix_const = 0x5d6008cbf3848dd3UL;
> @@ -96,3 +96,51 @@ unsigned long kaslr_get_random_long(const char *purpose)
>
> return random;
> }
> +
> +/*
> + * 64bit variant of Bob Jenkins' public domain PRNG
> + * 256 bits of internal state
> + */
> +struct prng_state {
> + u64 a, b, c, d;
> +};
> +
> +static struct prng_state state;
> +static bool initialized;
> +
> +#define rot(x, k) (((x)<<(k))|((x)>>(64-(k))))
> +static u64 prng_u64(struct prng_state *x)
> +{
> + u64 e;
> +
> + e = x->a - rot(x->b, 7);
> + x->a = x->b ^ rot(x->c, 13);
> + x->b = x->c + rot(x->d, 37);
> + x->c = x->d + e;
> + x->d = e + x->a;
> +
> + return x->d;
> +}
> +
> +static void prng_init(struct prng_state *state)
> +{
> + int i;
> +
> + state->a = kaslr_get_random_seed(NULL);
> + state->b = kaslr_get_random_seed(NULL);
> + state->c = kaslr_get_random_seed(NULL);
> + state->d = kaslr_get_random_seed(NULL);
> +
> + for (i = 0; i < 30; ++i)
> + (void)prng_u64(state);
> +
> + initialized = true;
> +}
> +
> +unsigned long kaslr_get_prandom_long(void)
> +{
> + if (!initialized)
> + prng_init(&state);
> +
> + return prng_u64(&state);
> +}
> diff --git a/arch/x86/mm/init.c b/arch/x86/mm/init.c
> index e7bb483557c9..c974dbab2293 100644
> --- a/arch/x86/mm/init.c
> +++ b/arch/x86/mm/init.c
> @@ -722,7 +722,7 @@ void __init poking_init(void)
> */
> poking_addr = TASK_UNMAPPED_BASE;
> if (IS_ENABLED(CONFIG_RANDOMIZE_BASE))
> - poking_addr += (kaslr_get_random_long("Poking") & PAGE_MASK) %
> + poking_addr += (kaslr_get_random_seed("Poking") & PAGE_MASK) %
> (TASK_SIZE - TASK_UNMAPPED_BASE - 3 * PAGE_SIZE);
>
> if (((poking_addr + PAGE_SIZE) & ~PMD_MASK) == 0)
> diff --git a/arch/x86/mm/kaslr.c b/arch/x86/mm/kaslr.c
> index dc6182eecefa..b30bd1db7543 100644
> --- a/arch/x86/mm/kaslr.c
> +++ b/arch/x86/mm/kaslr.c
> @@ -123,7 +123,7 @@ void __init kernel_randomize_memory(void)
> for (i = 0; i < ARRAY_SIZE(kaslr_regions); i++)
> remain_entropy -= get_padding(&kaslr_regions[i]);
>
> - prandom_seed_state(&rand_state, kaslr_get_random_long("Memory"));
> + prandom_seed_state(&rand_state, kaslr_get_random_seed("Memory"));
>
> for (i = 0; i < ARRAY_SIZE(kaslr_regions); i++) {
> unsigned long entropy;
> --
> 2.24.1
>
next prev parent reply other threads:[~2020-02-06 1:11 UTC|newest]
Thread overview: 72+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-02-05 22:39 [RFC PATCH 00/11] Finer grained kernel address space randomization Kristen Carlson Accardi
2020-02-05 22:39 ` [RFC PATCH 01/11] modpost: Support >64K sections Kristen Carlson Accardi
2020-02-06 12:38 ` Kees Cook
2020-02-05 22:39 ` [RFC PATCH 02/11] x86: tools/relocs: Support >64K section headers Kristen Carlson Accardi
2020-02-06 12:39 ` Kees Cook
2020-02-05 22:39 ` [RFC PATCH 03/11] x86/boot: Allow a "silent" kaslr random byte fetch Kristen Carlson Accardi
2020-02-06 1:08 ` Andy Lutomirski
2020-02-06 11:48 ` Kees Cook
2020-02-06 16:58 ` Kristen Carlson Accardi
2020-02-05 22:39 ` [RFC PATCH 04/11] x86/boot/KASLR: Introduce PRNG for faster shuffling Kristen Carlson Accardi
2020-02-06 1:11 ` Andy Lutomirski [this message]
2020-02-06 15:10 ` Jason A. Donenfeld
[not found] ` <CAGiyFdes26XnNeDfaz-vkm+bU7MBYQiK3xty2EigGjOXBGui2w@mail.gmail.com>
2020-02-07 9:05 ` Kees Cook
2020-02-07 16:52 ` Kristen Carlson Accardi
2020-02-05 22:39 ` [RFC PATCH 05/11] x86: Makefile: Add build and config option for CONFIG_FG_KASLR Kristen Carlson Accardi
2020-02-06 10:30 ` Peter Zijlstra
2020-02-06 11:52 ` Kees Cook
2020-02-25 17:55 ` Arvind Sankar
2020-02-26 19:13 ` Kristen Carlson Accardi
2020-03-24 21:24 ` Kristen Carlson Accardi
2020-03-25 15:34 ` Kees Cook
2020-02-05 22:39 ` [RFC PATCH 06/11] x86: make sure _etext includes function sections Kristen Carlson Accardi
2020-02-06 12:26 ` Kees Cook
2020-02-06 13:15 ` Jann Horn
2020-02-06 16:27 ` David Laight
2020-02-06 14:39 ` Arvind Sankar
2020-02-06 15:29 ` Arvind Sankar
2020-02-06 16:11 ` Andy Lutomirski
2020-02-06 14:57 ` Arvind Sankar
2020-02-06 15:45 ` Arvind Sankar
2020-02-06 19:41 ` Kristen Carlson Accardi
2020-02-06 20:02 ` Andy Lutomirski
2020-02-07 9:24 ` Peter Zijlstra
2020-02-10 1:43 ` Kees Cook
2020-02-10 10:51 ` Peter Zijlstra
2020-02-10 15:54 ` Arjan van de Ven
2020-02-10 16:36 ` Arvind Sankar
2020-02-21 19:50 ` Josh Poimboeuf
2020-02-21 23:05 ` Arvind Sankar
2020-02-05 22:39 ` [RFC PATCH 07/11] x86/tools: Adding relative relocs for randomized functions Kristen Carlson Accardi
2020-02-06 12:37 ` Kees Cook
2020-02-05 22:39 ` [RFC PATCH 08/11] x86: Add support for finer grained KASLR Kristen Carlson Accardi
2020-02-06 1:17 ` Andy Lutomirski
2020-02-06 11:56 ` Kees Cook
2020-02-06 17:36 ` Kristen Carlson Accardi
2020-02-06 10:38 ` Peter Zijlstra
2020-02-06 12:06 ` Kees Cook
2020-02-06 14:52 ` Peter Zijlstra
2020-02-06 17:25 ` Kristen Carlson Accardi
2020-02-06 17:35 ` Peter Zijlstra
2020-02-06 17:43 ` Kristen Carlson Accardi
2020-02-25 17:49 ` Arvind Sankar
2020-02-26 19:26 ` Kristen Carlson Accardi
2020-02-05 22:39 ` [RFC PATCH 09/11] kallsyms: hide layout and expose seed Kristen Carlson Accardi
2020-02-06 12:32 ` Kees Cook
2020-02-06 17:51 ` Kristen Carlson Accardi
2020-02-06 19:27 ` Jann Horn
2020-03-02 19:01 ` Kristen Carlson Accardi
2020-03-02 19:08 ` Kees Cook
2020-03-02 19:19 ` Kristen Carlson Accardi
2020-02-27 2:42 ` Baoquan He
2020-02-27 16:02 ` Kees Cook
2020-02-28 3:36 ` Baoquan He
2020-02-05 22:39 ` [RFC PATCH 10/11] module: Reorder functions Kristen Carlson Accardi
2020-02-06 12:41 ` Kees Cook
2020-02-11 12:39 ` Jessica Yu
2020-02-05 22:39 ` [RFC PATCH 11/11] x86/boot: Move "boot heap" out of .bss Kristen Carlson Accardi
2020-02-06 0:11 ` Arvind Sankar
2020-02-06 0:33 ` Kristen Carlson Accardi
2020-02-06 11:13 ` Kees Cook
2020-02-06 14:25 ` Arvind Sankar
2020-02-06 21:32 ` Kees Cook
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