cc_ssh.py: fix private key group owner and permissions (#1070)

When default host keys are created by sshd-keygen (/etc/ssh/ssh_host_*_key)
in RHEL/CentOS/Fedora, openssh it performs the following:

# create new keys
if ! $KEYGEN -q -t $KEYTYPE -f $KEY -C '' -N '' >&/dev/null; then
        exit 1
fi

# sanitize permissions
/usr/bin/chgrp ssh_keys $KEY
/usr/bin/chmod 640 $KEY
/usr/bin/chmod 644 $KEY.pub
Note that the group ssh_keys exists only in RHEL/CentOS/Fedora.

Now that we disable sshd-keygen to allow only cloud-init to create
them, we miss the "sanitize permissions" part, where we set the group
owner as ssh_keys and the private key mode to 640.

According to https://bugzilla.redhat.com/show_bug.cgi?id=2013644#c8, failing
to set group ownership and permissions like openssh does makes the RHEL openscap
tool generate an error.

Signed-off-by: Emanuele Giuseppe Esposito eesposit@redhat.com

RHBZ: 2013644

1 files changed, 14 insertions, 0 deletions

diff --git a/cloudinit/util.py b/cloudinit/util.py
index 1b4384e1..575a1fef 100644
--- a/cloudinit/util.py
+++ b/cloudinit/util.py
@@ -1880,6 +1880,20 @@ def chmod(path, mode):
             os.chmod(path, real_mode)
 
 
+def get_group_id(grp_name: str) -> int:
+    """
+    Returns the group id of a group name, or -1 if no group exists
+
+    @param grp_name: the name of the group
+    """
+    gid = -1
+    try:
+        gid = grp.getgrnam(grp_name).gr_gid
+    except KeyError:
+        LOG.debug("Group %s is not a valid group name", grp_name)
+    return gid
+
+
 def get_permissions(path: str) -> int:
     """
     Returns the octal permissions of the file/folder pointed by the path,