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google-compute-config: Reintroduce fetch-ssh-keys

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Reintroduce the `fetch-ssh-keys` service so that GCE images that work
with NixOps can once again be built. Also, reformat the code a bit.

The service was removed in 88570538b3,
likely due to a comment saying it should be removed. It was still
needed for images to work with NixOps, however, and probably needed to
be replaced or rewritten rather than removed.
This commit is contained in:
talyz 2021-01-13 11:01:01 +01:00
parent db4cede416
commit dd6ebb7871
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1 changed files with 63 additions and 0 deletions
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63
nixos/modules/virtualisation/google-compute-config.nix
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@ -69,6 +69,69 @@ in
# GC has 1460 MTU
networking.interfaces.eth0.mtu = 1460;
systemd.services.fetch-ssh-keys = {
description = "Fetch host keys and authorized_keys for root user";
wantedBy = [ "sshd.service" ];
before = [ "sshd.service" ];
after = [ "network-online.target" ];
wants = [ "network-online.target" ];
script =
let
wget = "${pkgs.wget}/bin/wget --retry-connrefused -t 15 --waitretry=10 --header='Metadata-Flavor: Google'";
mktemp = "mktemp --tmpdir=/run";
in ''
# When dealing with cryptographic keys, we want to keep things private.
umask 077
mkdir -m 0700 -p /root/.ssh
echo "Obtaining SSH keys..."
AUTH_KEYS=$(${mktemp})
${wget} -O $AUTH_KEYS http://metadata.google.internal/computeMetadata/v1/instance/attributes/sshKeys
if [ -s $AUTH_KEYS ]; then
# Read in key one by one, split in case Google decided
# to append metadata (it does sometimes) and add to
# authorized_keys if not already present.
touch /root/.ssh/authorized_keys
NEW_KEYS=$(${mktemp})
# Yes this is a nix escape of two single quotes.
while IFS=''' read -r line || [[ -n "$line" ]]; do
keyLine=$(echo -n "$line" | cut -d ':' -f2)
IFS=' ' read -r -a array <<< "$keyLine"
if [ ''${#array[@]} -ge 3 ]; then
echo ''${array[@]:0:3} >> $NEW_KEYS
echo "Added ''${array[@]:2} to authorized_keys"
fi
done < $AUTH_KEYS
mv $NEW_KEYS /root/.ssh/authorized_keys
chmod 600 /root/.ssh/authorized_keys
rm -f $KEY_PUB
else
echo "Downloading http://metadata.google.internal/computeMetadata/v1/project/attributes/sshKeys failed."
false
fi
rm -f $AUTH_KEYS
SSH_HOST_KEYS_DIR=$(${mktemp} -d)
${wget} -O $SSH_HOST_KEYS_DIR/ssh_host_ed25519_key http://metadata.google.internal/computeMetadata/v1/instance/attributes/ssh_host_ed25519_key
${wget} -O $SSH_HOST_KEYS_DIR/ssh_host_ed25519_key.pub http://metadata.google.internal/computeMetadata/v1/instance/attributes/ssh_host_ed25519_key_pub
if [ -s $SSH_HOST_KEYS_DIR/ssh_host_ed25519_key -a -s $SSH_HOST_KEYS_DIR/ssh_host_ed25519_key.pub ]; then
mv -f $SSH_HOST_KEYS_DIR/ssh_host_ed25519_key* /etc/ssh/
chmod 600 /etc/ssh/ssh_host_ed25519_key
chmod 644 /etc/ssh/ssh_host_ed25519_key.pub
else
echo "Setup of ssh host keys from http://metadata.google.internal/computeMetadata/v1/instance/attributes/ failed."
false
fi
rm -rf $SSH_HOST_KEYS_DIR
'';
serviceConfig.Type = "oneshot";
serviceConfig.RemainAfterExit = true;
serviceConfig.StandardError = "journal+console";
serviceConfig.StandardOutput = "journal+console";
};
systemd.services.google-instance-setup = {
description = "Google Compute Engine Instance Setup";
after = [ "network-online.target" "network.target" "rsyslog.service" ];