diff options
| author | Jason A. Donenfeld <Jason@zx2c4.com> | 2022-03-22 21:43:12 -0600 |
|---|---|---|
| committer | Jason A. Donenfeld <Jason@zx2c4.com> | 2022-03-25 08:49:40 -0600 |
| commit | d97c68d178fbf8aaaf21b69b446f2dfb13909316 (patch) | |
| tree | 4d3bf4711e8ba72c7ffe04e619559c15c4e1d38b /drivers/char | |
| parent | af704c856e888fb044b058d731d61b46eeec499d (diff) | |
random: treat bootloader trust toggle the same way as cpu trust toggle
If CONFIG_RANDOM_TRUST_CPU is set, the RNG initializes using RDRAND.
But, the user can disable (or enable) this behavior by setting
`random.trust_cpu=0/1` on the kernel command line. This allows system
builders to do reasonable things while avoiding howls from tinfoil
hatters. (Or vice versa.)
CONFIG_RANDOM_TRUST_BOOTLOADER is basically the same thing, but regards
the seed passed via EFI or device tree, which might come from RDRAND or
a TPM or somewhere else. In order to allow distros to more easily enable
this while avoiding those same howls (or vice versa), this commit adds
the corresponding `random.trust_bootloader=0/1` toggle.
Cc: Theodore Ts'o <tytso@mit.edu>
Cc: Graham Christensen <graham@grahamc.com>
Reviewed-by: Ard Biesheuvel <ardb@kernel.org>
Reviewed-by: Dominik Brodowski <linux@dominikbrodowski.net>
Link: https://github.com/NixOS/nixpkgs/pull/165355
Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
Diffstat (limited to 'drivers/char')
| -rw-r--r-- | drivers/char/Kconfig | 3 | ||||
| -rw-r--r-- | drivers/char/random.c | 8 |
2 files changed, 9 insertions, 2 deletions
diff --git a/drivers/char/Kconfig b/drivers/char/Kconfig index 740811893c57..55f48375e3fe 100644 --- a/drivers/char/Kconfig +++ b/drivers/char/Kconfig @@ -449,6 +449,7 @@ config RANDOM_TRUST_BOOTLOADER device randomness. Say Y here to assume the entropy provided by the booloader is trustworthy so it will be added to the kernel's entropy pool. Otherwise, say N here so it will be regarded as device input that - only mixes the entropy pool. + only mixes the entropy pool. This can also be configured at boot with + "random.trust_bootloader=on/off". endmenu diff --git a/drivers/char/random.c b/drivers/char/random.c index 74e0b069972e..1d7aac2a9600 100644 --- a/drivers/char/random.c +++ b/drivers/char/random.c @@ -948,11 +948,17 @@ static bool drain_entropy(void *buf, size_t nbytes, bool force) **********************************************************************/ static bool trust_cpu __ro_after_init = IS_ENABLED(CONFIG_RANDOM_TRUST_CPU); +static bool trust_bootloader __ro_after_init = IS_ENABLED(CONFIG_RANDOM_TRUST_BOOTLOADER); static int __init parse_trust_cpu(char *arg) { return kstrtobool(arg, &trust_cpu); } +static int __init parse_trust_bootloader(char *arg) +{ + return kstrtobool(arg, &trust_bootloader); +} early_param("random.trust_cpu", parse_trust_cpu); +early_param("random.trust_bootloader", parse_trust_bootloader); /* * The first collection of entropy occurs at system boot while interrupts @@ -1160,7 +1166,7 @@ EXPORT_SYMBOL_GPL(add_hwgenerator_randomness); */ void add_bootloader_randomness(const void *buf, size_t size) { - if (IS_ENABLED(CONFIG_RANDOM_TRUST_BOOTLOADER)) + if (trust_bootloader) add_hwgenerator_randomness(buf, size, size * 8); else add_device_randomness(buf, size); |