nixos/aesmd: add option to configure quote provider library

Changes sgx-psw to append `aesm` to `LD_LIBRARY_PATH`:
- Append instead of prepend to allow for overriding in service config
- As we already add a wrapper to add `aesm` to `LD_LIBRARY_PATH` it is
not necessary to also set in `LD_LIBRARY_PATH` of the systemd service.

Co-authored-by: Vincent Haupert <[e-mail]>

nixos/modules/services/security/aesmd.nix

···
       default = false;
       description = lib.mdDoc "Whether to build the PSW package in debug mode.";
     };
+    quoteProviderLibrary = mkOption {
+      type = with types; nullOr path;
+      default = null;
+      example = literalExpression "pkgs.sgx-azure-dcap-client";
+      description = lib.mdDoc "Custom quote provider library to use.";
+    };
     settings = mkOption {
       description = lib.mdDoc "AESM configuration";
       default = { };
···
         storeAesmFolder = "${sgx-psw}/aesm";
         # Hardcoded path AESM_DATA_FOLDER in psw/ae/aesm_service/source/oal/linux/aesm_util.cpp
         aesmDataFolder = "/var/opt/aesmd/data";
-        aesmStateDirSystemd = "%S/aesmd";
       in
       {
         description = "Intel Architectural Enclave Service Manager";
···
         environment = {
           NAME = "aesm_service";
           AESM_PATH = storeAesmFolder;
-          LD_LIBRARY_PATH = storeAesmFolder;
+          LD_LIBRARY_PATH = makeLibraryPath [ cfg.quoteProviderLibrary ];
         };
 
         # Make sure any of the SGX application enclave devices is available

nixos/tests/aesmd.nix

···
 { pkgs, lib, ... }: {
   name = "aesmd";
   meta = {
-    maintainers = with lib.maintainers; [ veehaitch ];
+    maintainers = with lib.maintainers; [ trundle veehaitch ];
   };
 
   nodes.machine = { lib, ... }: {
···
 
     # We don't have a real SGX machine in NixOS tests
     systemd.services.aesmd.unitConfig.AssertPathExists = lib.mkForce [ ];
+
+    specialisation = {
+      withQuoteProvider.configuration = { ... }: {
+        services.aesmd.quoteProviderLibrary = pkgs.sgx-azure-dcap-client;
+      };
+    };
   };
 
-  testScript = ''
-    with subtest("aesmd.service starts"):
-      machine.wait_for_unit("aesmd.service")
-      status, main_pid = machine.systemctl("show --property MainPID --value aesmd.service")
-      assert status == 0, "Could not get MainPID of aesmd.service"
-      main_pid = main_pid.strip()
+  testScript = { nodes, ... }:
+    let
+      specialisations = "${nodes.machine.system.build.toplevel}/specialisation";
+    in
+    ''
+      def get_aesmd_pid():
+        status, main_pid = machine.systemctl("show --property MainPID --value aesmd.service")
+        assert status == 0, "Could not get MainPID of aesmd.service"
+        return main_pid.strip()
+
+      with subtest("aesmd.service starts"):
+        machine.wait_for_unit("aesmd.service")
+
+      main_pid = get_aesmd_pid()
+
+      with subtest("aesmd.service runtime directory permissions"):
+        runtime_dir = "/run/aesmd";
+        res = machine.succeed(f"stat -c '%a %U %G' {runtime_dir}").strip()
+        assert "750 aesmd sgx" == res, f"{runtime_dir} does not have the expected permissions: {res}"
+
+      with subtest("aesm.socket available on host"):
+        socket_path = "/var/run/aesmd/aesm.socket"
+        machine.wait_until_succeeds(f"test -S {socket_path}")
+        machine.succeed(f"test 777 -eq $(stat -c '%a' {socket_path})")
+        for op in [ "-r", "-w", "-x" ]:
+          machine.succeed(f"sudo -u sgxtest test {op} {socket_path}")
+          machine.fail(f"sudo -u nosgxtest test {op} {socket_path}")
+
+      with subtest("Copies white_list_cert_to_be_verify.bin"):
+        whitelist_path = "/var/opt/aesmd/data/white_list_cert_to_be_verify.bin"
+        whitelist_perms = machine.succeed(
+          f"nsenter -m -t {main_pid} ${pkgs.coreutils}/bin/stat -c '%a' {whitelist_path}"
+        ).strip()
+        assert "644" == whitelist_perms, f"white_list_cert_to_be_verify.bin has permissions {whitelist_perms}"
+
+      with subtest("Writes and binds aesm.conf in service namespace"):
+        aesmd_config = machine.succeed(f"nsenter -m -t {main_pid} ${pkgs.coreutils}/bin/cat /etc/aesmd.conf")
 
-    with subtest("aesmd.service runtime directory permissions"):
-      runtime_dir = "/run/aesmd";
-      res = machine.succeed(f"stat -c '%a %U %G' {runtime_dir}").strip()
-      assert "750 aesmd sgx" == res, f"{runtime_dir} does not have the expected permissions: {res}"
+        assert aesmd_config == "whitelist url = http://nixos.org\nproxy type = direct\ndefault quoting type = ecdsa_256\n", "aesmd.conf differs"
 
-    with subtest("aesm.socket available on host"):
-      socket_path = "/var/run/aesmd/aesm.socket"
-      machine.wait_until_succeeds(f"test -S {socket_path}")
-      machine.succeed(f"test 777 -eq $(stat -c '%a' {socket_path})")
-      for op in [ "-r", "-w", "-x" ]:
-        machine.succeed(f"sudo -u sgxtest test {op} {socket_path}")
-        machine.fail(f"sudo -u nosgxtest test {op} {socket_path}")
+      with subtest("aesmd.service without quote provider library has correct LD_LIBRARY_PATH"):
+        status, environment = machine.systemctl("show --property Environment --value aesmd.service")
+        assert status == 0, "Could not get Environment of aesmd.service"
+        env_by_name = dict(entry.split("=", 1) for entry in environment.split())
+        assert not env_by_name["LD_LIBRARY_PATH"], "LD_LIBRARY_PATH is not empty"
 
-    with subtest("Copies white_list_cert_to_be_verify.bin"):
-      whitelist_path = "/var/opt/aesmd/data/white_list_cert_to_be_verify.bin"
-      whitelist_perms = machine.succeed(
-        f"nsenter -m -t {main_pid} ${pkgs.coreutils}/bin/stat -c '%a' {whitelist_path}"
-      ).strip()
-      assert "644" == whitelist_perms, f"white_list_cert_to_be_verify.bin has permissions {whitelist_perms}"
+      with subtest("aesmd.service with quote provider library starts"):
+        machine.succeed('${specialisations}/withQuoteProvider/bin/switch-to-configuration test')
+        machine.wait_for_unit("aesmd.service")
 
-    with subtest("Writes and binds aesm.conf in service namespace"):
-      aesmd_config = machine.succeed(f"nsenter -m -t {main_pid} ${pkgs.coreutils}/bin/cat /etc/aesmd.conf")
+      main_pid = get_aesmd_pid()
 
-      assert aesmd_config == "whitelist url = http://nixos.org\nproxy type = direct\ndefault quoting type = ecdsa_256\n", "aesmd.conf differs"
-  '';
+      with subtest("aesmd.service with quote provider library has correct LD_LIBRARY_PATH"):
+        ld_library_path = machine.succeed(f"xargs -0 -L1 -a /proc/{main_pid}/environ | grep LD_LIBRARY_PATH")
+        assert ld_library_path.startswith("LD_LIBRARY_PATH=${pkgs.sgx-azure-dcap-client}/lib:"), \
+          "LD_LIBRARY_PATH is not set to the configured quote provider library"
+    '';
 }

nixos/tests/all-tests.nix

···
   _3proxy = runTest ./3proxy.nix;
   acme = runTest ./acme.nix;
   adguardhome = runTest ./adguardhome.nix;
-  aesmd = runTest ./aesmd.nix;
+  aesmd = runTestOn ["x86_64-linux"] ./aesmd.nix;
   agate = runTest ./web-servers/agate.nix;
   agda = handleTest ./agda.nix {};
   airsonic = handleTest ./airsonic.nix {};

pkgs/os-specific/linux/sgx/psw/default.nix

···
 
     mkdir $out/bin
     makeWrapper $out/aesm/aesm_service $out/bin/aesm_service \
-      --prefix LD_LIBRARY_PATH : ${lib.makeLibraryPath [ protobuf ]}:$out/aesm \
+      --suffix LD_LIBRARY_PATH : ${lib.makeLibraryPath [ protobuf ]}:$out/aesm \
       --chdir "$out/aesm"
 
     # Make sure we didn't forget to handle any files