Module Name: src
Committed By: riastradh
Date: Mon Aug 26 15:28:58 UTC 2024
Modified Files:
src/share/man/man4: acpivmgenid.4
Log Message:
acpivmgenid(4): Nix BUGS that have been squashed.
Reference kern.entropy.epoch for the remaining bug (which is a
performance issue, not a security issue).
PR kern/58632: getentropy(2) and arc4random(3) do not reseed on VM
fork
To generate a diff of this commit:
cvs rdiff -u -r1.1 -r1.2 src/share/man/man4/acpivmgenid.4
Please note that diffs are not public domain; they are subject to the
copyright notices on the relevant files.
Modified files:
Index: src/share/man/man4/acpivmgenid.4
diff -u src/share/man/man4/acpivmgenid.4:1.1 src/share/man/man4/acpivmgenid.4:1.2
--- src/share/man/man4/acpivmgenid.4:1.1 Mon Aug 26 13:38:28 2024
+++ src/share/man/man4/acpivmgenid.4 Mon Aug 26 15:28:58 2024
@@ -1,4 +1,4 @@
-.\" $NetBSD: acpivmgenid.4,v 1.1 2024/08/26 13:38:28 riastradh Exp $
+.\" $NetBSD: acpivmgenid.4,v 1.2 2024/08/26 15:28:58 riastradh Exp $
.\"
.\" Copyright (c) 2024 The NetBSD Foundation, Inc.
.\" All rights reserved.
@@ -57,7 +57,12 @@ will reseed system random number generat
.Pa /dev/urandom
and
.Xr getentropy 3
-will be independent in the two clones.
+will be independent in the two clones, and the
+.Xr sysctl 7
+variable
+.Li kern.entropy.epoch
+will advance to notify applications that they should reseed random
+number generators from the system entropy pool.
.\"""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""
.Sh SYSCTLS
The following
@@ -94,19 +99,10 @@ driver first appeared in
.Nx 11.0 .
.\"""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""
.Sh BUGS
-Currently
-.Nx
-does not request fresh samples from all on-demand entropy sources when
-the VM generation ID changes, so although the outputs of the system
-entropy pool appear independent to an outside observer, disclosing the
-kernel memory of one VM clone to an adversary may allow the adversary
-to predict another VM clone's
-.Pa /dev/urandom
-outputs.
-.Pp
-Currently
-.Xr arc4random 3
-is not reseeded when the VM generation ID changes.
-.Pp
Currently there is no cheaper way to detect VM generation ID changes
than to query sysctl.
+(Applications deciding whether to reseed random number generators
+should generally query
+.Li kern.entropy.epoch ,
+not
+.Li "hw.acpivmgenid" Ns Va N Ns Li ".id" . )
