hive CA: catch a deleted CA file however its path is spelled

The CA-file assertion compared the option's raw string, so
`/var/lib//swarm-ca/root.pem` or `/var/lib/hive-tls/./ca.pem` got past it.
Both sides are normalised lexically now: empty and `.` components drop out,
`..` removes the one before it, a trailing `/` goes. A symlink is not
resolved at eval time, so a path through one still passes; docs/swarm/ca.md
says so.

docs/swarm/ca.md

@@ -182,8 +182,10 @@ under it.
 
 A host whose `deploy.bao.clientCaFile`, `deploy.bao.serverCaFile` or
 `deploy.swarm-controller.hiveClientCaFile` names one of those paths fails
-evaluation. Those options name the store's mTLS CA,
+evaluation, however it's spelled with `//`, `.`, `..` or a trailing `/`. A
-`/var/lib/swarm-bao-pki/ca.pem` on the host that runs the store.
+symlink to one isn't resolved, so it gets past the check. Those options name
+the store's mTLS CA, `/var/lib/swarm-bao-pki/ca.pem` on the host that runs
+the store.
 
 ## What to hand a peer
 

nix/host-modules/host-ca-removed.nix

@@ -21,7 +21,29 @@ let
     "ca-previous.pem"
     "ca-key.pem"
   ];
-  deleted = p: p == swarmCaDir || lib.hasPrefix "${swarmCaDir}/" p || lib.elem p hiveCaFiles;
+  # Lexical only: empty and `.` components drop out and `..` removes the
+  # one before it. A symlink is not resolved, so a path reaching a deleted
+  # file through one passes the check below.
+  normalise =
+    p:
+    lib.optionalString (lib.hasPrefix "/" p) "/"
+    + lib.concatStringsSep "/" (
+      lib.foldl' (
+        kept: c:
+        if c == "" || c == "." then
+          kept
+        else if c == ".." then
+          (if kept == [ ] then [ ] else lib.init kept)
+        else
+          kept ++ [ c ]
+      ) [ ] (lib.splitString "/" p)
+    );
+  deleted =
+    p:
+    let
+      n = normalise p;
+    in
+    n == swarmCaDir || lib.hasPrefix "${swarmCaDir}/" n || lib.elem n (map normalise hiveCaFiles);
   # The hive CA's serial file and its adoption marker: neither is a CA, so
   # no CA-file option can name them, and nothing reads them.
   hiveCaLeftovers = map (f: "${deployCfg.hive-controller.tls.stateDir}/${f}") [

nix/module-eval/hive-tls.nix

@@ -79,6 +79,22 @@ let
 
   remainsAfterExit = u: u.serviceConfig.RemainAfterExit or false;
 
+  # Whether `m` fails evaluation on `deploy.<option>` naming a deleted CA
+  # file, with the message pointing at the store's mTLS CA.
+  caFileRefused =
+    m: option:
+    lib.any (
+      a:
+      !a.assertion
+      && lib.hasInfix "services.hyperhive.deploy.${option} is" a.message
+      && lib.hasInfix "/var/lib/swarm-bao-pki/ca.pem" a.message
+    ) m.assertions;
+  caFileOptions = [
+    "bao.clientCaFile"
+    "bao.serverCaFile"
+    "swarm-controller.hiveClientCaFile"
+  ];
+
   renewAt = hours: "renewat=$(( ${toString hours} * 3600 / 2 ))";
 
   cases = [
@@ -402,14 +418,6 @@ let
       name = "a CA-file option naming a deleted CA file fails evaluation, naming the store's mTLS CA";
       ok =
         let
-          refused =
-            m: option:
-            lib.any (
-              a:
-              !a.assertion
-              && lib.hasInfix "services.hyperhive.deploy.${option} is" a.message
-              && lib.hasInfix "/var/lib/swarm-bao-pki/ca.pem" a.message
-            ) m.assertions;
           oldRoot = hiveWithController {
             deploy.singleHostSwarm = true;
             deploy.bao.clientCaFile = "/var/lib/swarm-ca/root.pem";
@@ -418,19 +426,34 @@ let
             deploy.bao.serverCaFile = "/var/lib/hive-tls/ca.pem";
             deploy.swarm-controller.hiveClientCaFile = "/var/lib/hive-tls/ca-previous.pem";
           };
-          options = [
-            "bao.clientCaFile"
-            "bao.serverCaFile"
-            "swarm-controller.hiveClientCaFile"
-          ];
         in
-        refused oldRoot "bao.clientCaFile"
+        caFileRefused oldRoot "bao.clientCaFile"
-        && refused oldRoot "swarm-controller.hiveClientCaFile"
+        && caFileRefused oldRoot "swarm-controller.hiveClientCaFile"
-        && refused hiveCa "bao.serverCaFile"
+        && caFileRefused hiveCa "bao.serverCaFile"
-        && refused hiveCa "swarm-controller.hiveClientCaFile"
+        && caFileRefused hiveCa "swarm-controller.hiveClientCaFile"
-        && !(lib.any (refused allLocal) options)
+        && !(lib.any (caFileRefused allLocal) caFileOptions)
         && allLocal.services.hyperhive.deploy.bao.clientCaFile == "/var/lib/swarm-bao-pki/ca.pem";
     }
+    {
+      # The control is a host whose options normalise to paths beside the
+      # deleted ones: a sibling of the swarm root's directory, and the
+      # store's mTLS CA reached through `..`.
+      name = "a CA-file option spelling a deleted path with `//`, `.`, `..` or a trailing slash fails evaluation too";
+      ok =
+        let
+          spelled = hive {
+            deploy.bao.clientCaFile = "/var/lib//swarm-ca/";
+            deploy.bao.serverCaFile = "/var/lib/hive-tls/./ca.pem";
+            deploy.swarm-controller.hiveClientCaFile = "/var/lib/hive-tls/x/../ca-key.pem";
+          };
+          beside = hive {
+            deploy.bao.clientCaFile = "/var/lib//swarm-ca-copy/./root.pem";
+            deploy.bao.serverCaFile = "/var/lib/hive-tls/../swarm-bao-pki/ca.pem";
+            deploy.swarm-controller.hiveClientCaFile = "/var/lib/hive-tls/ca.pem/../trust-bundle.pem";
+          };
+        in
+        lib.all (caFileRefused spelled) caFileOptions && !(lib.any (caFileRefused beside) caFileOptions);
+    }
     {
       # The store host's hive presents the leaf ./glue-bao-tls.nix mints for
       # it; not the reader's, not the services issuer's.