nixos/tpm2: create tss user and group if either is required (#490284)

nixos/modules/security/tpm2.nix

@@ -276,11 +276,11 @@ in
         services.udev.extraRules = lib.mkIf cfg.applyUdevRules (udevRules cfg.tssUser cfg.tssGroup);
 
         # Create the tss user and group only if the default value is used
-        users.users.${cfg.tssUser} = lib.mkIf (cfg.tssUser == "tss") {
+        users.users.tss = lib.mkIf (cfg.tssUser == "tss" || cfg.tssGroup == "tss") {
           isSystemUser = true;
           group = "tss";
         };
-        users.groups.${cfg.tssGroup} = lib.mkIf (cfg.tssGroup == "tss") { };
+        users.groups.tss = lib.mkIf (cfg.tssUser == "tss" || cfg.tssGroup == "tss") { };
 
         environment.variables = lib.mkIf cfg.tctiEnvironment.enable (
           lib.attrsets.genAttrs

nixos/tests/all-tests.nix

@@ -1638,7 +1638,7 @@ in
   tomcat = runTest ./tomcat.nix;
   tor = runTest ./tor.nix;
   tpm-ek = handleTest ./tpm-ek { };
-  tpm2 = runTest ./tpm2.nix;
+  tpm2 = import ./tpm2 { inherit runTest; };
   traccar = runTest ./traccar.nix;
   # tracee requires bpf
   tracee = handleTestOn [ "x86_64-linux" ] ./tracee.nix { };

nixos/tests/tpm2/default.nix

@@ -0,0 +1,5 @@
+{ runTest }:
+{
+  abrmd = runTest ./tpm2-abrmd.nix;
+  tpmrm = runTest ./tpm2-tpmrm.nix;
+}

nixos/tests/tpm2/tpm2-abrmd.nix

@@ -39,6 +39,10 @@
     machine.start()
     machine.wait_for_unit("multi-user.target")
 
+    with subtest("/dev/tpmrm0 has correct ownership"):
+        machine.succeed('[ `stat -c "%U" /dev/tpmrm0` = "tss" ]')
+        machine.succeed('[ `stat -c "%G" /dev/tpmrm0` = "tss" ]')
+
     with subtest("tabrmd service started properly"):
         machine.succeed('[ `systemctl show tpm2-abrmd.service --property=Result` = "Result=success" ]')
         machine.succeed('[ `journalctl -b -u tpm2-abrmd.service | grep -c "Starting"` = "1" ]')

nixos/tests/tpm2/tpm2-tpmrm.nix

@@ -0,0 +1,72 @@
+{ lib, pkgs, ... }:
+{
+  name = "tpm2-tpmrm";
+
+  nodes.machine =
+    { config, pkgs, ... }:
+    {
+      virtualisation = {
+        mountHostNixStore = true;
+        useEFIBoot = true;
+        tpm.enable = true;
+      };
+
+      users.users = {
+        tss-user = {
+          isNormalUser = true;
+          extraGroups = [ "tss" ];
+        };
+      };
+
+      security.sudo.wheelNeedsPassword = false;
+
+      security.tpm2 = {
+        enable = true;
+        pkcs11.enable = true;
+        tctiEnvironment.enable = true;
+        fapi.ekCertLess = true;
+      };
+
+      environment.systemPackages = [
+        pkgs.tpm2-tools
+        pkgs.openssl
+      ];
+    };
+
+  testScript = ''
+    machine.start()
+    machine.wait_for_unit("multi-user.target")
+
+    with subtest("/dev/tpmrm0 has correct ownership"):
+        machine.succeed('[ `stat -c "%U" /dev/tpmrm0` = "root" ]')
+        machine.succeed('[ `stat -c "%G" /dev/tpmrm0` = "tss" ]')
+
+    with subtest("tpm2 cli works"):
+        machine.succeed('tpm2 createprimary --hierarchy=o --key-algorithm=aes256 --attributes="fixedtpm|fixedparent|sensitivedataorigin|userwithauth|restricted|decrypt" --key-context=owner_root_key.ctx')
+        machine.succeed('tpm2 create --parent-context=owner_root_key.ctx --key-algorithm=ecc256:ecdsa-sha256:null --attributes="fixedtpm|fixedparent|sensitivedataorigin|userwithauth|restricted|sign" --key-context=ecc_sign_key.ctx --creation-ticket=ecc_sign_key-creation_ticket.bin -f pem --output=ecc_sign_key_public.pem')
+        machine.succeed('echo "A very important message." > message.txt')
+        machine.succeed('tpm2 sign --key-context=ecc_sign_key.ctx --hash-algorithm=sha256 -f plain --signature message_signature.bin message.txt')
+        machine.succeed('openssl dgst -verify ecc_sign_key_public.pem -signature message_signature.bin message.txt')
+        machine.succeed('echo "evil addition!" >> message.txt')
+        machine.fail('openssl dgst -verify ecc_sign_key_public.pem -signature message_signature.bin message.txt')
+
+    def format_command(command, user):
+        return f"runuser -u {user} -- bash -c '{command}'"
+    def succeedu(command,user):
+        return machine.succeed(format_command(command,user))
+    def failu(command,user):
+        return machine.fail(format_command(command,user))
+
+    with subtest("tss2 cli works"):
+        machine.succeed('tss2 provision')
+        succeedu('tss2 createkey --path=HS/SRK/sign --type=sign --authValue=""',"tss-user")
+        succeedu('tss2 gettpmblobs --path=HS/SRK/sign --tpm2bPublic=$HOME/sign_key_public.bin',"tss-user")
+        succeedu('tpm2 print -t TPM2B_PUBLIC -f pem $HOME/sign_key_public.bin > $HOME/sign_key_public.pem',"tss-user")
+        succeedu('echo "A very important message." > $HOME/message.txt',"tss-user")
+        succeedu('tpm2 hash --hash-algorithm=sha256 --output=$HOME/message_hash.bin $HOME/message.txt',"tss-user")
+        succeedu('tss2 sign --keyPath=HS/SRK/sign --digest=$HOME/message_hash.bin --signature=$HOME/message_signature.bin',"tss-user")
+        succeedu('openssl dgst -verify $HOME/sign_key_public.pem -signature $HOME/message_signature.bin $HOME/message.txt',"tss-user")
+        succeedu('echo "evil addition!" >> $HOME/message.txt',"tss-user")
+        failu('openssl dgst -verify $HOME/sign_key_public.pem -signature $HOME/message_signature.bin $HOME/message.txt',"tss-user")
+  '';
+}