[202012][armhf] sshd failed to start

[Blueve]

Description

sshd failed to start in armhf platform after this PR merged #10910

Permission errors are raised during start up sshd service

sudo sshd -t
@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@
@         WARNING: UNPROTECTED PRIVATE KEY FILE!          @
@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@
Permissions 0644 for '/etc/ssh/ssh_host_rsa_key' are too open.
It is required that your private key files are NOT accessible by others.
This private key will be ignored.
@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@
@         WARNING: UNPROTECTED PRIVATE KEY FILE!          @
@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@
Permissions 0644 for '/etc/ssh/ssh_host_ecdsa_key' are too open.
It is required that your private key files are NOT accessible by others.
This private key will be ignored.
@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@
@         WARNING: UNPROTECTED PRIVATE KEY FILE!          @
@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@
Permissions 0644 for '/etc/ssh/ssh_host_ed25519_key' are too open.
It is required that your private key files are NOT accessible by others.
This private key will be ignored.
sshd: no hostkeys available -- exiting.

Issue can be mitigated by manually change the key's permission level

sudo chmod 600 /etc/ssh/ssh_host_rsa_key
sudo chmod 600 /etc/ssh/ssh_host_ecdsa_key
sudo chmod 600 /etc/ssh/ssh_host_ed25519_key

The issue were not found on x86 platform.

Steps to reproduce the issue:

1. Install image with change [202012][openssh] openssh: Upgrade from 7.9 to 8.4, to match version in buster-backports #10910
2. ssh to the device

Describe the results you received:

ssh client failed to connect to switch

Describe the results you expected:

ssh should work as usual

Output of show version:

(paste your output here)

Output of show techsupport:

(paste your output here or download and attach the file here )

Additional information you deem important (e.g. issue happens only occasionally):

[Blueve]

Might related to this change? #10633

[Blueve]

Plan to revert the openssh upgrade change: #11136

The main concern is the openssh 8.4 will bring another issue: CVE-2021-28041 openssh: double-free memory corruption may lead to arbitrary code execution

[yxieca]

@Blueve what do we need to do to close this issue? Any further actions?

[Blueve]

@yxieca the root cause was armhf private key permission issue.
I think we need to solve it as well before we close this issue.