Description of problem:

By default selinux blocks qemu guest agent from accessing SSH key files.
Currently there is a boolean to allow reading keys "virt_qemu_ga_read_ssh", but there is no boolean to allow writing keys.

Version-Release number of selected component (if applicable):
selinux-policy  38.1.8-1.el9 

How reproducible:
100%

Steps to Reproduce:
1. Start a VM with RHEL 9.2 guest image. I've used "rhel-guest-image-9.2-20230220.9.x86_64.qcow2"

virt-customize -a rhel-9.2.qcow2 \
  --ssh-inject root \
  --root-password password:pass123 \
  --uninstall cloud-init \
  --connect qemu:///system

virt-install --name test-vm \
  --vcpus 2 \
  --cpu host \
  --memory 2048 \
  --rng /dev/urandom \
  --disk rhel-9.2.qcow2 \
  --os-variant=rhel9.0 \
  --import \
  --boot uefi \
  --noautoconsole \
  --connect qemu:///system


2. Try to set SSH keys using qemu guest agent.
virsh -c qemu:///system set-user-sshkeys test-vm root --file ~/.ssh/id_rsa.pub

Fails with error message:
error: internal error: unable to execute QEMU agent command 'guest-ssh-add-authorized-keys': failed to write to '/root/.ssh/authorized_keys': Failed to create file “/root/.ssh/authorized_keys.SUES11”: Permission denied


Additional info:

Reading the keys fails similarly, if the "virt_qemu_ga_read_ssh" boolean is not set in the guest.

virsh -c qemu:///system get-user-sshkeys test-vm root

fails with:
error: internal error: unable to execute QEMU agent command 'guest-ssh-get-authorized-keys': failed to read '/root/.ssh/authorized_keys': Failed to open file “/root/.ssh/authorized_keys”: Permission denied


After the boolean is set,

virsh -c qemu:///system get-user-sshkeys test-vm root

Succeeds and prints the key.