From ae099e8e98fb01395228628be5a4661e3bd86fe4 Mon Sep 17 00:00:00 2001 From: "Jason A. Donenfeld" Date: Wed, 23 Feb 2022 13:43:44 +0100 Subject: random: add mechanism for VM forks to reinitialize crng When a VM forks, we must immediately mix in additional information to the stream of random output so that two forks or a rollback don't produce the same stream of random numbers, which could have catastrophic cryptographic consequences. This commit adds a simple API, add_vmfork_ randomness(), for that, by force reseeding the crng. This has the added benefit of also draining the entropy pool and setting its timer back, so that any old entropy that was there prior -- which could have already been used by a different fork, or generally gone stale -- does not contribute to the accounting of the next 256 bits. Cc: Dominik Brodowski Cc: Theodore Ts'o Cc: Jann Horn Cc: Eric Biggers Reviewed-by: Ard Biesheuvel Signed-off-by: Jason A. Donenfeld --- include/linux/random.h | 1 + 1 file changed, 1 insertion(+) (limited to 'include/linux') diff --git a/include/linux/random.h b/include/linux/random.h index 725a4d08c0a0..117468f3a92e 100644 --- a/include/linux/random.h +++ b/include/linux/random.h @@ -34,6 +34,7 @@ extern void add_input_randomness(unsigned int type, unsigned int code, extern void add_interrupt_randomness(int irq) __latent_entropy; extern void add_hwgenerator_randomness(const void *buffer, size_t count, size_t entropy); +extern void add_vmfork_randomness(const void *unique_vm_id, size_t size); extern void get_random_bytes(void *buf, size_t nbytes); extern int wait_for_random_bytes(void); -- cgit v1.2.3-59-g8ed1b