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| author | Jason A. Donenfeld <Jason@zx2c4.com> | 2022-03-23 06:43:12 +0300 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2022-06-25 12:46:37 +0300 |
| commit | eed01a6b3e563bcc6cbe27ab046dc3cd46febd22 (patch) | |
| tree | f14e737ef026375ebc902482b75f8d8359307719 | |
| parent | df5104c1d0b6a602d5030fadf0249df4c302b9d7 (diff) | |
| download | linux-eed01a6b3e563bcc6cbe27ab046dc3cd46febd22.tar.xz | |
random: treat bootloader trust toggle the same way as cpu trust toggle
commit d97c68d178fbf8aaaf21b69b446f2dfb13909316 upstream.
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>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
| -rw-r--r-- | Documentation/admin-guide/kernel-parameters.txt | 6 | ||||
| -rw-r--r-- | drivers/char/Kconfig | 3 | ||||
| -rw-r--r-- | drivers/char/random.c | 8 |
3 files changed, 15 insertions, 2 deletions
diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt index 5840c7e810f5..681d429c6426 100644 --- a/Documentation/admin-guide/kernel-parameters.txt +++ b/Documentation/admin-guide/kernel-parameters.txt @@ -3532,6 +3532,12 @@ fully seed the kernel's CRNG. Default is controlled by CONFIG_RANDOM_TRUST_CPU. + random.trust_bootloader={on,off} + [KNL] Enable or disable trusting the use of a + seed passed by the bootloader (if available) to + fully seed the kernel's CRNG. Default is controlled + by CONFIG_RANDOM_TRUST_BOOTLOADER. + ras=option[,option,...] [KNL] RAS-specific options cec_disable [X86] diff --git a/drivers/char/Kconfig b/drivers/char/Kconfig index 9f51fd6bf5b4..3efb8a74dc01 100644 --- a/drivers/char/Kconfig +++ b/drivers/char/Kconfig @@ -612,4 +612,5 @@ 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.
\ No newline at end of file + only mixes the entropy pool. This can also be configured at boot with + "random.trust_bootloader=on/off". diff --git a/drivers/char/random.c b/drivers/char/random.c index 3fa256f02d65..48b87675ffdb 100644 --- a/drivers/char/random.c +++ b/drivers/char/random.c @@ -940,11 +940,17 @@ static bool drain_entropy(void *buf, size_t nbytes) **********************************************************************/ 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 @@ -1152,7 +1158,7 @@ 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); |