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Subject: Re: [PATCH 2/3] random: rng-seed source is utf-8
To:     "Theodore Y. Ts'o" <tytso@mit.edu>, Rob Herring <robh@kernel.org>
Cc:     Masami Hiramatsu <mhiramat@kernel.org>,
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        Android Kernel Team <kernel-team@android.com>,
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        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        Richard Henderson <richard.henderson@linaro.org>,
        Mark Brown <broonie@kernel.org>,
        Kees Cook <keescook@chromium.org>,
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From:   Mark Salyzyn <salyzyn@android.com>
Message-ID: <f15511bf-b840-0633-3354-506b7b0607fe@android.com>
Date:   Fri, 14 Feb 2020 14:55:36 -0800
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On 2/14/20 2:47 PM, Theodore Y. Ts'o wrote:
> On Fri, Feb 14, 2020 at 01:58:35PM -0600, Rob Herring wrote:
>> On Fri, Feb 14, 2020 at 12:10 AM Masami Hiramatsu <mhiramat@kernel.org> wrote:
>>> From: Mark Salyzyn <salyzyn@android.com>
>>>
>>> commit 428826f5358c922dc378830a1717b682c0823160
>>> ("fdt: add support for rng-seed") makes the assumption that the data
>>> in rng-seed is binary, when it is typically constructed of utf-8
>> Typically? Why is that?
>>
>>> characters which has a bitness of roughly 6 to give appropriate
>>> credit due for the entropy.
> This is why I really think what gets specified via the boot command
> line, or bootconfig, should specify the bits of entropy and the
> entropy seed *separately*, so it can be specified explicitly, instead
> of assuming that *everyone knows* that rng-seed is either (a) a binary
> string, or (b) utf-8, or (c) a hex string.  The fact is, everyone does
> *not* know, or everyone will have a different implementation, which
> everyone will say is *obviously* the only way to go....
>
> 	      	     		     	  - Ted

Given that the valid option are between 4 (hex), 6 (utf-8) or 8 
(binary), we can either split the difference and accept 6; or take a 
pass at the values and determine which of the set they belong to 
[0-9a-fA-F], [!-~] or [\000-\377]  nor need to separately specify.

-- Mark