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42 lines
1.7 KiB
Groff
42 lines
1.7 KiB
Groff
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.TH seedrng 8
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.SH NAME
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seedrng \- seed the Linux kernel random number generator
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.SH SYNOPSIS
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.B seedrng
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.SH DESCRIPTION
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.B SeedRNG
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SeedRNG is a simple program made for seeding the Linux kernel random
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number generator from seed files. The program takes no arguments, must
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be run as root, and always attempts to do something useful.
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This program is useful in light of the fact that the Linux kernel RNG
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cannot be initialized from shell scripts, and new seeds cannot be safely
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generated from boot time shell scripts either.
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It should be run once at init time and once at shutdown time. It can be
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run at other times without detriment as well. Whenever it is run, it writes
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existing seed files into the RNG pool, and then creates a new seed file.
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If the RNG is initialized at the time of creating a new seed file, then that
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new seed file is marked as "creditable", which means it can be used to
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initialize the RNG. Otherwise, it is marked as "non-creditable", in which
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case it is still used to seed the RNG's pool, but will not initialize the
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RNG.
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In order to ensure that entropy only ever stays the same or increases from
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one seed file to the next, old seed values are hashed together with new seed
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values when writing new seed files:
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.BR
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new_seed = new_seed[:-32] || HASH(fixed_prefix || real_time || boot_time || old_seed_len || old_seed || new_seed_len || new_seed)
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The seed is stored in /var/lib/seedrng/, which can be adjusted at
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compile time. If the SEEDRNG_SKIP_CREDIT environment variable is set to 1,
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true, yes, or y, then seeds never credit the RNG, even if the seed file
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is creditable.
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.SH FILES
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.IR /var/lib/seedrng/seed.credit
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.IR /var/lib/seedrng/seed.no-credit
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.SH AUTHOR
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Jason A. Donenfeld <Jason@zx2c4.com>
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