linux-kernel - [PATCH 5.15 049/145] random: ensure early RDSEED goes through mixer on init

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-Id: <20220527084856.727135806@linuxfoundation.org>
Date:   Fri, 27 May 2022 10:49:10 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Theodore Tso <tytso@....edu>,
        Dominik Brodowski <linux@...inikbrodowski.net>,
        Eric Biggers <ebiggers@...gle.com>,
        "Jason A. Donenfeld" <Jason@...c4.com>
Subject: [PATCH 5.15 049/145] random: ensure early RDSEED goes through mixer on init

From: "Jason A. Donenfeld" <Jason@...c4.com>

commit a02cf3d0dd77244fd5333ac48d78871de459ae6d upstream.

Continuing the reasoning of "random: use RDSEED instead of RDRAND in
entropy extraction" from this series, at init time we also don't want to
be xoring RDSEED directly into the crng. Instead it's safer to put it
into our entropy collector and then re-extract it, so that it goes
through a hash function with preimage resistance. As a matter of hygiene,
we also order these now so that the RDSEED byte are hashed in first,
followed by the bytes that are likely more predictable (e.g. utsname()).

Cc: Theodore Ts'o <tytso@....edu>
Reviewed-by: Dominik Brodowski <linux@...inikbrodowski.net>
Reviewed-by: Eric Biggers <ebiggers@...gle.com>
Signed-off-by: Jason A. Donenfeld <Jason@...c4.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 drivers/char/random.c |   16 +++++-----------
 1 file changed, 5 insertions(+), 11 deletions(-)

--- a/drivers/char/random.c
+++ b/drivers/char/random.c
@@ -1208,24 +1208,18 @@ int __init rand_initialize(void)
 	bool arch_init = true;
 	unsigned long rv;
 
-	mix_pool_bytes(&now, sizeof(now));
 	for (i = BLAKE2S_BLOCK_SIZE; i > 0; i -= sizeof(rv)) {
-		if (!arch_get_random_seed_long(&rv) &&
-		    !arch_get_random_long(&rv))
-			rv = random_get_entropy();
-		mix_pool_bytes(&rv, sizeof(rv));
-	}
-	mix_pool_bytes(utsname(), sizeof(*(utsname())));
-
-	extract_entropy(&primary_crng.state[4], sizeof(u32) * 12);
-	for (i = 4; i < 16; i++) {
 		if (!arch_get_random_seed_long_early(&rv) &&
 		    !arch_get_random_long_early(&rv)) {
 			rv = random_get_entropy();
 			arch_init = false;
 		}
-		primary_crng.state[i] ^= rv;
+		mix_pool_bytes(&rv, sizeof(rv));
 	}
+	mix_pool_bytes(&now, sizeof(now));
+	mix_pool_bytes(utsname(), sizeof(*(utsname())));
+
+	extract_entropy(&primary_crng.state[4], sizeof(u32) * 12);
 	if (arch_init && trust_cpu && crng_init < 2) {
 		invalidate_batched_entropy();
 		crng_init = 2;