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Message-ID: <CAGXu5j+orJe-6FzZvuOiZQKM+_vnwjVmN_5_KP7+LJH_-h0MZg@mail.gmail.com>
Date: Wed, 16 Aug 2017 16:23:16 -0700
From: Kees Cook <keescook@...omium.org>
To: Laura Abbott <labbott@...hat.com>
Cc: Daniel Micay <danielmicay@...il.com>,
"kernel-hardening@...ts.openwall.com" <kernel-hardening@...ts.openwall.com>, LKML <linux-kernel@...r.kernel.org>,
Linux-MM <linux-mm@...ck.org>, Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [PATCHv3 2/2] extract early boot entropy from the passed cmdline
On Wed, Aug 16, 2017 at 4:14 PM, Laura Abbott <labbott@...hat.com> wrote:
> From: Daniel Micay <danielmicay@...il.com>
>
>
> Existing Android bootloaders usually pass data useful as early entropy
> on the kernel command-line. It may also be the case on other embedded
> systems. Sample command-line from a Google Pixel running CopperheadOS:
>
> console=ttyHSL0,115200,n8 androidboot.console=ttyHSL0
> androidboot.hardware=sailfish user_debug=31 ehci-hcd.park=3
> lpm_levels.sleep_disabled=1 cma=32M@...xffffffff buildvariant=user
> veritykeyid=id:dfcb9db0089e5b3b4090a592415c28e1cb4545ab
> androidboot.bootdevice=624000.ufshc androidboot.verifiedbootstate=yellow
> androidboot.veritymode=enforcing androidboot.keymaster=1
> androidboot.serialno=FA6CE0305299 androidboot.baseband=msm
> mdss_mdp.panel=1:dsi:0:qcom,mdss_dsi_samsung_ea8064tg_1080p_cmd:1:none:cfg:single_dsi
> androidboot.slot_suffix=_b fpsimd.fpsimd_settings=0
> app_setting.use_app_setting=0 kernelflag=0x00000000 debugflag=0x00000000
> androidboot.hardware.revision=PVT radioflag=0x00000000
> radioflagex1=0x00000000 radioflagex2=0x00000000 cpumask=0x00000000
> androidboot.hardware.ddr=4096MB,Hynix,LPDDR4 androidboot.ddrinfo=00000006
> androidboot.ddrsize=4GB androidboot.hardware.color=GRA00
> androidboot.hardware.ufs=32GB,Samsung androidboot.msm.hw_ver_id=268824801
> androidboot.qf.st=2 androidboot.cid=11111111 androidboot.mid=G-2PW4100
> androidboot.bootloader=8996-012001-1704121145
> androidboot.oem_unlock_support=1 androidboot.fp_src=1
> androidboot.htc.hrdump=detected androidboot.ramdump.opt=mem@2g:2g,mem@4g:2g
> androidboot.bootreason=reboot androidboot.ramdump_enable=0 ro
> root=/dev/dm-0 dm="system none ro,0 1 android-verity /dev/sda34"
> rootwait skip_initramfs init=/init androidboot.wificountrycode=US
> androidboot.boottime=1BLL:85,1BLE:669,2BLL:0,2BLE:1777,SW:6,KL:8136
>
> Among other things, it contains a value unique to the device
> (androidboot.serialno=FA6CE0305299), unique to the OS builds for the
> device variant (veritykeyid=id:dfcb9db0089e5b3b4090a592415c28e1cb4545ab)
> and timings from the bootloader stages in milliseconds
> (androidboot.boottime=1BLL:85,1BLE:669,2BLL:0,2BLE:1777,SW:6,KL:8136).
>
> Signed-off-by: Daniel Micay <danielmicay@...il.com>
> [labbott: Line-wrapped command line]
> Signed-off-by: Laura Abbott <labbott@...hat.com>
Acked-by: Kees Cook <keescook@...omium.org>
Thanks!
-Kees
> ---
> v3: add_device_randomness comes before canary initialization, clarified comment.
> ---
> init/main.c | 2 ++
> 1 file changed, 2 insertions(+)
>
> diff --git a/init/main.c b/init/main.c
> index 21d599eaad06..ba2b3a8a2382 100644
> --- a/init/main.c
> +++ b/init/main.c
> @@ -530,8 +530,10 @@ asmlinkage __visible void __init start_kernel(void)
> setup_arch(&command_line);
> /*
> * Set up the the initial canary and entropy after arch
> + * and after adding latent and command line entropy.
> */
> add_latent_entropy();
> + add_device_randomness(command_line, strlen(command_line));
> boot_init_stack_canary();
> mm_init_cpumask(&init_mm);
> setup_command_line(command_line);
> --
> 2.13.0
>
--
Kees Cook
Pixel Security
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