[kirkstone][PATCH] openssh: remove RRECOMMENDS to rng-tools for sshd package

Xiangyu Chen

It appears that rngd is not needed as of linux-5.6 and later[1]
and should not be installed by default since the purpose of rngd
is to provide additional trusted sources of entropy.

We did some testing on real hardware, the result seems to support that
we no longer need rngd by default on kernel v5.6 and later.

Testing result as below:

1. observing the crng init stage.
the "random: crng init done" always available before fs being mounted.

2. generating random number without rngd.
testing command: dd if=/dev/random of=/dev/null status=progress
on Marvell CN96xx RDB board, speed almost 20.4 MB/s without block
on NXP i.mx6q board, speed almost 31.9 MB/s without block
on qemu x86-64, speed almost 2.6MB/s without block

3. using rngtest command without rngd
testing command: rngtest -c 1000 </dev/random
on Marvell CN96xx RDB board:
rngtest: input channel speed: (min=4.340; avg=135.364; max=146.719)Mibits/s
rngtest: FIPS tests speed: (min=8.197; avg=69.020; max=72.800)Mibits/s
rngtest: Program run time: 418771 microseconds

on NXP i.mx6q board:
rngtest: input channel speed: (min=96.820; avg=326.769; max=340.598)Mibits/s
rngtest: FIPS tests speed: (min=15.090; avg=37.543; max=40.324)Mibits/s
rngtest: Program run time: 570229 microseconds

on qemu x86-64:
rngtest: input channel speed: (min=37.769; avg=101.136; max=136.239)Mibits/s
rngtest: FIPS tests speed: (min=10.288; avg=30.682; max=40.155)Mibits/s
rngtest: Program run time: 836800 microseconds

4. observing sshd service.
using "systemctl disable rng-tools" disable service and reboot system.
system boot up normal, sshd service also start in normal time without

[1] https://github.com/torvalds/linux/commit/30c08efec8884fb106b8e57094baa51bb4c44e32

Signed-off-by: Xiangyu Chen <xiangyu.chen@...>
Signed-off-by: Alexandre Belloni <alexandre.belloni@...>
(cherry picked from commit 868dfb46d96a27ec9041cb902fb769330277257d)
meta/recipes-connectivity/openssh/openssh_8.9p1.bb | 10 +---------
1 file changed, 1 insertion(+), 9 deletions(-)

diff --git a/meta/recipes-connectivity/openssh/openssh_8.9p1.bb b/meta/recipes-connectivity/openssh/openssh_8.9p1.bb
index e4446280d9..6057d055f4 100644
--- a/meta/recipes-connectivity/openssh/openssh_8.9p1.bb
+++ b/meta/recipes-connectivity/openssh/openssh_8.9p1.bb
@@ -54,15 +54,12 @@ SYSTEMD_SERVICE:${PN}-sshd = "sshd.socket"

inherit autotools-brokensep ptest

-PACKAGECONFIG ??= "rng-tools"
PACKAGECONFIG[kerberos] = "--with-kerberos5,--without-kerberos5,krb5"
PACKAGECONFIG[ldns] = "--with-ldns,--without-ldns,ldns"
PACKAGECONFIG[libedit] = "--with-libedit,--without-libedit,libedit"
PACKAGECONFIG[manpages] = "--with-mantype=man,--with-mantype=cat"

-# Add RRECOMMENDS to rng-tools for sshd package
-PACKAGECONFIG[rng-tools] = ""
EXTRA_AUTORECONF += "--exclude=aclocal"

# login path is hardcoded in sshd
@@ -162,15 +159,10 @@ FILES:${PN}-keygen = "${bindir}/ssh-keygen"

RDEPENDS:${PN} += "${PN}-scp ${PN}-ssh ${PN}-sshd ${PN}-keygen ${PN}-sftp-server"
RDEPENDS:${PN}-sshd += "${PN}-keygen ${@bb.utils.contains('DISTRO_FEATURES', 'pam', 'pam-plugin-keyinit pam-plugin-loginuid', '', d)}"
-RRECOMMENDS:${PN}-sshd:append:class-target = "\
- ${@bb.utils.filter('PACKAGECONFIG', 'rng-tools', d)} \
# break dependency on base package for -dev package
# otherwise SDK fails to build as the main openssh and dropbear packages
# conflict with each other
RDEPENDS:${PN}-dev = ""
# gdb would make attach-ptrace test pass rather than skip but not worth the build dependencies
RDEPENDS:${PN}-ptest += "${PN}-sftp ${PN}-misc ${PN}-sftp-server make sed sudo coreutils"