swarm-bao: keep the bootstrap policy in one file, checked against the units using it (#4698)
setup.md's copy of the swarm-bootstrap policy still granted only the controller's first six paths, while eight units now act with the bootstrap token. The policy moves to nix/host-modules/swarm-bao-bootstrap-policy.hcl, now covering every path those units call. module-eval-bao-grants reads that file and fails when a unit whose script uses the token calls a path the file does not grant.
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@ -94,6 +94,125 @@ let
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"swarm-bao-otel-oidc"
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];
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# What the bootstrap token may do, read from the file the operator writes it
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# from (../../docs/getting-started/setup.md points there), against what the
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# units holding that token actually call. The units are found by the token
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# path in their script rather than by name, so a new one is checked without
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# anyone listing it here.
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bootstrapTokenFile = "/run/secrets/bao-bootstrap.token";
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bootstrapUnits = lib.filterAttrs (
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_: u: lib.hasInfix bootstrapTokenFile u.script
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) baoGrantWithConsumers.systemd.services;
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# Comment lines dropped first: both the HCL and the scripts explain
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# themselves in prose that names paths and `bao` commands.
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codeLines =
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text: lib.filter (l: builtins.match "[[:space:]]*#.*" l == null) (lib.splitString "\n" text);
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bootstrapPolicyText = lib.concatStringsSep "\n" (
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codeLines (builtins.readFile ../host-modules/swarm-bao-bootstrap-policy.hcl)
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);
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matches = re: text: lib.filter lib.isList (builtins.split re text);
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bootstrapGrants =
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map
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(m: {
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path = lib.elemAt m 0;
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caps = map lib.head (matches ''"([a-z]+)"'' (lib.elemAt m 1));
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})
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(
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matches ''path "([^"]+)"[[:space:]]*[{][[:space:]]*capabilities[[:space:]]*=[[:space:]]*[[]([a-z", ]*)'' bootstrapPolicyText
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);
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# One `bao …` invocation → the path and capabilities it needs, as
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# `bao <cmd> -output-policy` reports them. Path-specific `sudo` (bao's
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# root-protected paths, e.g. `pki/root` for a delete) does not follow from
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# the verb, so only `auth enable` is checked for it. A verb not listed here
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# needs a path no grant has, so it fails the case until it is taught.
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baoCallNeeds =
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words:
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let
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flags = lib.filter (lib.hasPrefix "-") words;
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args = lib.filter (w: !(lib.hasPrefix "-" w) && w != "\\") words;
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a = i: if i < lib.length args then lib.elemAt args i else "";
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need = path: caps: {
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inherit path caps;
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call = lib.concatStringsSep " " words;
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};
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cu = [
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"create"
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"update"
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];
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in
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if a 0 == "policy" && a 1 == "write" then
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need "sys/policies/acl/${a 2}" cu
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else if a 0 == "secrets" && a 1 == "list" then
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need "sys/mounts" [ "read" ]
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else if a 0 == "secrets" && a 1 == "enable" then
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need "sys/mounts/${lib.removePrefix "-path=" (lib.findFirst (lib.hasPrefix "-path=") "-path=${a 2}" flags)}" cu
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else if a 0 == "secrets" && a 1 == "tune" then
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need "sys/mounts/${a 2}/tune" cu
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else if a 0 == "auth" && a 1 == "list" then
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need "sys/auth" [ "read" ]
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else if a 0 == "auth" && a 1 == "enable" then
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need "sys/auth/${a 2}" (cu ++ [ "sudo" ])
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else if a 0 == "write" then
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need (a 1) cu
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else if a 0 == "read" then
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need (a 1) [ "read" ]
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else if a 0 == "list" then
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need (a 1) [ "list" ]
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else if a 0 == "delete" then
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need (a 1) [ "delete" ]
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else
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need "unrecognised call" [ ];
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baoCalls =
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script:
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map
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(
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inv:
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baoCallNeeds (lib.filter (w: w != "") (lib.splitString " " (lib.replaceStrings [ "'" ] [ "" ] inv)))
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)
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(
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lib.concatMap (l: map (m: lib.elemAt m 1) (matches "(^[[:space:]]*|[$][(]|[)] )bao ([^|;)]*)" l)) (
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codeLines script
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)
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);
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# bao's own rule: an exact path wins, otherwise the longest glob prefix.
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bootstrapGrantFor =
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path:
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let
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exact = lib.filter (g: g.path == path) bootstrapGrants;
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globs = lib.filter (
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g: lib.hasSuffix "*" g.path && lib.hasPrefix (lib.removeSuffix "*" g.path) path
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) bootstrapGrants;
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in
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if exact != [ ] then
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lib.head exact
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else
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lib.foldl' (
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best: g: if best == null || lib.stringLength g.path > lib.stringLength best.path then g else best
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) null globs;
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bootstrapUngranted = lib.concatLists (
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lib.mapAttrsToList (
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unit: u:
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map (n: "${unit}: `bao ${n.call}` needs ${n.path} [${toString n.caps}]") (
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lib.filter (
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n:
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let
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g = bootstrapGrantFor n.path;
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in
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g == null || !(lib.all (c: lib.elem c g.caps) n.caps)
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) (baoCalls u.script)
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)
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) bootstrapUnits
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);
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cases = [
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{
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# Reads the rendered unit on the HOST, which is where the write happens:
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@ -627,6 +746,43 @@ let
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name = "a bootstrap token on a host that runs no store grants nothing";
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ok = !(baoGrantNoStore.systemd.services ? swarm-bao-bootstrap-dir);
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}
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{
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# The drift this case exists to stop: setup.md's copy of the policy
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# stayed at the controller's first six grants while seven more units
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# started using the token. Failing names every ungranted call.
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name =
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"every bao call a bootstrap-token unit makes is granted by swarm-bao-bootstrap-policy.hcl"
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+ lib.optionalString (bootstrapUngranted != [ ]) (
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": " + lib.concatStringsSep "; " bootstrapUngranted
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);
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ok = bootstrapUngranted == [ ];
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}
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{
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# What makes the case above mean something: discovery by token path
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# reaches every unit that uses the token today, and each yields calls.
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name = "the bootstrap-policy check sees all eight units that use the token, and parses calls from each";
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ok =
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lib.all (n: bootstrapUnits ? ${n}) [
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"swarm-bao-controller-policy"
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"swarm-bao-secret-publisher-policy"
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"swarm-bao-matrix-ctl-policy"
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"swarm-bao-matrix-token-policy"
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"swarm-bao-queue-agent-policy"
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"swarm-bao-grafana-oidc-policy"
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"swarm-bao-otel-oidc-policy"
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"swarm-bao-services-issuer-policy"
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]
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&& lib.all (u: baoCalls u.script != [ ]) (lib.attrValues bootstrapUnits);
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}
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{
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# And the grants side: a stanza the parser skipped would read as a
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# grant that is not there.
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name = "every path stanza in swarm-bao-bootstrap-policy.hcl parses";
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ok =
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bootstrapGrants != [ ]
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&& lib.length bootstrapGrants == lib.length (matches ''path "'' bootstrapPolicyText)
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&& lib.all (g: g.caps != [ ]) bootstrapGrants;
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}
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];
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in
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runGroup "bao-grants" cases
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