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agenix
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modules/age: symlink files into place 

This follows sops-nix's implementation, where it creates a
`/run/secrets.d` ramfs mountpoint and a "generation" each time
the activation script runs, and then symlinks `/run/secrets` to
`/run/secrets.d/[generation]`.
This commit is contained in:
Cole Helbling 2021-02-25 02:23:15 -08:00
parent 53aa91b417
commit f816a0d5df
1 changed files with 61 additions and 7 deletions
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68
modules/age.nix
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@ -16,16 +16,19 @@ let
identities = builtins.concatStringsSep " " (map (path: "-i ${path}") cfg.sshKeyPaths);
installSecret = secretType: ''
echo "decrypting ${secretType.file} to ${secretType.path}..."
TMP_FILE="${secretType.path}.tmp"
mkdir -p $(dirname ${secretType.path})
_truePath="${cfg.secretsMountPoint}/$_count/${secretType.name}"
echo "decrypting '${secretType.file}' to '$_truePath'..."
TMP_FILE="$_truePath.tmp"
mkdir -p "$(dirname "$_truePath")"
mkdir -p "$(dirname "${secretType.path}")"
(
umask u=r,g=,o=
LANG=${config.i18n.defaultLocale} ${ageBin} --decrypt ${identities} -o "$TMP_FILE" "${secretType.file}"
)
chmod ${secretType.mode} "$TMP_FILE"
chown ${secretType.owner}:${secretType.group} "$TMP_FILE"
mv -f "$TMP_FILE" '${secretType.path}'
mv -f "$TMP_FILE" "$_truePath"
[ "${secretType.path}" != "/run/secrets/${secretType.name}" ] && ln -sfn "/run/secrets/${secretType.name}" "${secretType.path}"
'';
isRootSecret = st: (st.owner == "root" || st.owner == "0") && (st.group == "root" || st.group == "0");
@ -92,6 +95,17 @@ in
Attrset of secrets.
'';
};
secretsMountPoint = mkOption {
type = types.addCheck types.str
(s:
(builtins.match "[ \t\n]*" s) == null # non-empty
&& (builtins.match ".+/" s) == null) # without trailing slash
// { description = "${types.str.description} (with check: non-empty without trailing slash)"; };
default = "/run/secrets.d";
description = ''
Where secrets are created before they are symlinked to /run/secrets
'';
};
sshKeyPaths = mkOption {
type = types.listOf types.path;
default =
@ -110,14 +124,54 @@ in
message = "age.sshKeyPaths must be set.";
}];
# Create a new directory full of secrets for symlinking (this helps
# ensure removed secrets are actually removed, or at least become
# invalid symlinks).
system.activationScripts.agenixMountSecrets = ''
_count="$(basename "$(readlink /run/secrets)" || echo 0)"
(( ++_count ))
echo "[agenix] symlinking new secrets to /run/secrets (generation $_count)..."
mkdir -p "${cfg.secretsMountPoint}"
chmod 0750 "${cfg.secretsMountPoint}"
grep -q "${cfg.secretsMountPoint} ramfs" /proc/mounts || mount -t ramfs none "${cfg.secretsMountPoint}" -o nodev,nosuid,mode=0750
mkdir -p "${cfg.secretsMountPoint}/$_count"
chmod 0750 "${cfg.secretsMountPoint}/$_count"
chown :keys "${cfg.secretsMountPoint}" "${cfg.secretsMountPoint}/$_count"
ln -sfn "${cfg.secretsMountPoint}/$_count" /run/secrets
'';
# Secrets with root owner and group can be installed before users
# exist. This allows user password files to be encrypted.
system.activationScripts.agenixRoot = stringAfter [ "specialfs" ] installRootOwnedSecrets;
system.activationScripts.agenixRoot = {
text = installRootOwnedSecrets;
deps = [ "agenixMountSecrets" "specialfs" ];
};
system.activationScripts.users.deps = [ "agenixRoot" ];
# Other secrets need to wait for users and groups to exist.
system.activationScripts.agenix = stringAfter [ "users" "groups" "specialfs" ] installNonRootSecrets;
# chown the secrets mountpoint and the current generation to the keys group
# instead of leaving it root:root.
system.activationScripts.agenixChownKeys = {
text = ''
chown :keys "${cfg.secretsMountPoint}" "${cfg.secretsMountPoint}/$_agenix_generation"
'';
deps = [
"users"
"groups"
"agenixMountSecrets"
];
};
# Other secrets need to wait for users and groups to exist.
system.activationScripts.agenix = {
text = installNonRootSecrets;
deps = [
"users"
"groups"
"specialfs"
"agenixMountSecrets"
"agenixChownKeys"
];
};
};
}