diff --git a/nixos/modules/module-list.nix b/nixos/modules/module-list.nix index 28f536056bf..40904ef0c17 100644 --- a/nixos/modules/module-list.nix +++ b/nixos/modules/module-list.nix @@ -200,6 +200,7 @@ ./security/rtkit.nix ./security/wrappers/default.nix ./security/sudo.nix + ./security/doas.nix ./security/systemd-confinement.nix ./security/tpm2.nix ./services/admin/oxidized.nix diff --git a/nixos/modules/security/doas.nix b/nixos/modules/security/doas.nix new file mode 100644 index 00000000000..1991a58db60 --- /dev/null +++ b/nixos/modules/security/doas.nix @@ -0,0 +1,274 @@ +{ config, lib, pkgs, ... }: + +with lib; +let + cfg = config.security.doas; + + inherit (pkgs) doas; + + mkUsrString = user: toString user; + + mkGrpString = group: ":${toString group}"; + + mkOpts = rule: concatStringsSep " " [ + (optionalString rule.noPass "nopass") + (optionalString rule.persist "persist") + (optionalString rule.keepEnv "keepenv") + "setenv { SSH_AUTH_SOCK ${concatStringsSep " " rule.setEnv} }" + ]; + + mkArgs = rule: + if (isNull rule.args) then "" + else if (length rule.args == 0) then "args" + else "args ${concatStringsSep " " rule.args}"; + + mkRule = rule: + let + opts = mkOpts rule; + + as = optionalString (!isNull rule.runAs) "as ${rule.runAs}"; + + cmd = optionalString (!isNull rule.cmd) "cmd ${rule.cmd}"; + + args = mkArgs rule; + in + optionals (length cfg.extraRules > 0) [ + ( + optionalString (length rule.users > 0) + (map (usr: "permit ${opts} ${mkUsrString usr} ${as} ${cmd} ${args}") rule.users) + ) + ( + optionalString (length rule.groups > 0) + (map (grp: "permit ${opts} ${mkGrpString grp} ${as} ${cmd} ${args}") rule.groups) + ) + ]; +in +{ + + ###### interface + + options.security.doas = { + + enable = mkOption { + type = with types; bool; + default = false; + description = '' + Whether to enable the doas command, which allows + non-root users to execute commands as root. + ''; + }; + + wheelNeedsPassword = mkOption { + type = with types; bool; + default = true; + description = '' + Whether users of the wheel group must provide a password to + run commands as super user via doas. + ''; + }; + + extraRules = mkOption { + default = []; + description = '' + Define specific rules to be set in the + /etc/doas.conf file. More specific rules should + come after more general ones in order to yield the expected behavior. + You can use mkBefore and/or mkAfter to ensure + this is the case when configuration options are merged. + ''; + example = literalExample '' + [ + # Allow execution of any command by any user in group doas, requiring + # a password and keeping any previously-defined environment variables. + { groups = [ "doas" ]; noPass = false; keepEnv = true; } + + # Allow execution of "/home/root/secret.sh" by user `backup` OR user + # `database` OR any member of the group with GID `1006`, without a + # password. + { users = [ "backup" "database" ]; groups = [ 1006 ]; + cmd = "/home/root/secret.sh"; noPass = true; } + + # Allow any member of group `bar` to run `/home/baz/cmd1.sh` as user + # `foo` with argument `hello-doas`. + { groups = [ "bar" ]; runAs = "foo"; + cmd = "/home/baz/cmd1.sh"; args = [ "hello-doas" ]; } + + # Allow any member of group `bar` to run `/home/baz/cmd2.sh` as user + # `foo` with no arguments. + { groups = [ "bar" ]; runAs = "foo"; + cmd = "/home/baz/cmd2.sh"; args = [ ]; } + + # Allow user `abusers` to execute "nano" and unset the value of + # SSH_AUTH_SOCK, override the value of ALPHA to 1, and inherit the + # value of BETA from the current environment. + { users = [ "abusers" ]; cmd = "nano"; + setEnv = [ "-SSH_AUTH_SOCK" "ALPHA=1" "BETA" ]; } + ] + ''; + type = with types; listOf ( + submodule { + options = { + + noPass = mkOption { + type = with types; bool; + default = false; + description = '' + If true, the user is not required to enter a + password. + ''; + }; + + persist = mkOption { + type = with types; bool; + default = false; + description = '' + If true, do not ask for a password again for some + time after the user successfully authenticates. + ''; + }; + + keepEnv = mkOption { + type = with types; bool; + default = false; + description = '' + If true, environment variables other than those + listed in + doas1 + are kept when creating the environment for the new process. + ''; + }; + + setEnv = mkOption { + type = with types; listOf str; + default = []; + description = '' + Keep or set the specified variables. Variables may also be + removed with a leading '-' or set using + variable=value. If the first character of + value is a '$', the value to be set is taken from + the existing environment variable of the indicated name. This + option is processed after the default environment has been + created. + + NOTE: All rules have setenv { SSH_AUTH_SOCK } by + default. To prevent SSH_AUTH_SOCK from being + inherited, add "-SSH_AUTH_SOCK" anywhere in this + list. + ''; + }; + + users = mkOption { + type = with types; listOf (either str int); + default = []; + description = "The usernames / UIDs this rule should apply for."; + }; + + groups = mkOption { + type = with types; listOf (either str int); + default = []; + description = "The groups / GIDs this rule should apply for."; + }; + + runAs = mkOption { + type = with types; nullOr str; + default = null; + description = '' + Which user or group the specified command is allowed to run as. + When set to null (the default), all users are + allowed. + + A user can be specified using just the username: + "foo". It is also possible to only allow running as + a specific group with ":bar". + ''; + }; + + cmd = mkOption { + type = with types; nullOr str; + default = null; + description = '' + The command the user is allowed to run. When set to + null (the default), all commands are allowed. + + NOTE: It is best practice to specify absolute paths. If a + relative path is specified, only a restricted PATH will be + searched. + ''; + }; + + args = mkOption { + type = with types; nullOr (listOf str); + default = null; + description = '' + Arguments that must be provided to the command. When set to + [], the command must be run without any arguments. + ''; + }; + }; + } + ); + }; + + extraConfig = mkOption { + type = with types; lines; + default = ""; + description = '' + Extra configuration text appended to doas.conf. + ''; + }; + }; + + + ###### implementation + + config = mkIf cfg.enable { + + security.doas.extraRules = [ + { + groups = [ "wheel" ]; + noPass = !cfg.wheelNeedsPassword; + } + ]; + + security.wrappers = { + doas.source = "${doas}/bin/doas"; + }; + + environment.systemPackages = [ + doas + ]; + + security.pam.services.doas = { + allowNullPassword = true; + sshAgentAuth = true; + }; + + environment.etc."doas.conf" = { + source = pkgs.runCommand "doas-conf" + { + src = pkgs.writeText "doas-conf-in" '' + # To modify this file, set the NixOS options + # `security.doas.extraRules` or `security.doas.extraConfig`. To + # completely replace the contents of this file, use + # `environment.etc."doas.conf"`. + + # "root" is allowed to do anything. + permit nopass keepenv root + + # extraRules + ${concatStringsSep "\n" (lists.flatten (map mkRule cfg.extraRules))} + + # extraConfig + ${cfg.extraConfig} + ''; + preferLocalBuild = true; + } + # Make sure that the doas.conf file is syntactically valid. + "${pkgs.buildPackages.doas}/bin/doas -C $src && cp $src $out"; + mode = "0440"; + }; + + }; + + meta.maintainers = with maintainers; [ cole-h ]; +} diff --git a/nixos/tests/all-tests.nix b/nixos/tests/all-tests.nix index ebb0dfef15a..b8ff4647b9f 100644 --- a/nixos/tests/all-tests.nix +++ b/nixos/tests/all-tests.nix @@ -69,6 +69,7 @@ in deluge = handleTest ./deluge.nix {}; dhparams = handleTest ./dhparams.nix {}; dnscrypt-proxy2 = handleTestOn ["x86_64-linux"] ./dnscrypt-proxy2.nix {}; + doas = handleTest ./doas.nix {}; docker = handleTestOn ["x86_64-linux"] ./docker.nix {}; oci-containers = handleTestOn ["x86_64-linux"] ./oci-containers.nix {}; docker-edge = handleTestOn ["x86_64-linux"] ./docker-edge.nix {}; diff --git a/nixos/tests/doas.nix b/nixos/tests/doas.nix new file mode 100644 index 00000000000..9c0a4bdc756 --- /dev/null +++ b/nixos/tests/doas.nix @@ -0,0 +1,83 @@ +# Some tests to ensure doas is working properly. +import ./make-test-python.nix ( + { lib, ... }: { + name = "doas"; + meta = with lib.maintainers; { + maintainers = [ cole-h ]; + }; + + machine = + { ... }: + { + users.groups = { foobar = {}; barfoo = {}; baz = { gid = 1337; }; }; + users.users = { + test0 = { isNormalUser = true; extraGroups = [ "wheel" ]; }; + test1 = { isNormalUser = true; }; + test2 = { isNormalUser = true; extraGroups = [ "foobar" ]; }; + test3 = { isNormalUser = true; extraGroups = [ "barfoo" ]; }; + test4 = { isNormalUser = true; extraGroups = [ "baz" ]; }; + test5 = { isNormalUser = true; }; + test6 = { isNormalUser = true; }; + test7 = { isNormalUser = true; }; + }; + + security.doas = { + enable = true; + wheelNeedsPassword = false; + + extraRules = [ + { users = [ "test1" ]; groups = [ "foobar" ]; } + { users = [ "test2" ]; noPass = true; setEnv = [ "CORRECT" "HORSE=BATTERY" ]; } + { groups = [ "barfoo" 1337 ]; noPass = true; } + { users = [ "test5" ]; noPass = true; keepEnv = true; runAs = "test1"; } + { users = [ "test6" ]; noPass = true; keepEnv = true; setEnv = [ "-STAPLE" ]; } + { users = [ "test7" ]; noPass = true; setEnv = [ "-SSH_AUTH_SOCK" ]; } + ]; + }; + }; + + testScript = '' + with subtest("users in wheel group should have passwordless doas"): + machine.succeed('su - test0 -c "doas -u root true"') + + with subtest("test1 user should not be able to use doas without password"): + machine.fail('su - test1 -c "doas -n -u root true"') + + with subtest("test2 user should be able to keep some env"): + if "CORRECT=1" not in machine.succeed('su - test2 -c "CORRECT=1 doas env"'): + raise Exception("failed to keep CORRECT") + + if "HORSE=BATTERY" not in machine.succeed('su - test2 -c "doas env"'): + raise Exception("failed to setenv HORSE=BATTERY") + + with subtest("users in group 'barfoo' shouldn't require password"): + machine.succeed("doas -u test3 doas -n -u root true") + + with subtest("users in group 'baz' (GID 1337) shouldn't require password"): + machine.succeed("doas -u test4 doas -n -u root echo true") + + with subtest("test5 user should be able to run commands under test1"): + machine.succeed("doas -u test5 doas -n -u test1 true") + + with subtest("test5 user should not be able to run commands under root"): + machine.fail("doas -u test5 doas -n -u root true") + + with subtest("test6 user should be able to keepenv"): + envs = ["BATTERY=HORSE", "CORRECT=false"] + out = machine.succeed( + 'su - test6 -c "BATTERY=HORSE CORRECT=false STAPLE=Tr0ub4dor doas env"' + ) + + if not all(env in out for env in envs): + raise Exception("failed to keep BATTERY or CORRECT") + if "STAPLE=Tr0ub4dor" in out: + raise Exception("failed to exclude STAPLE") + + with subtest("test7 should not have access to SSH_AUTH_SOCK"): + if "SSH_AUTH_SOCK=HOLEY" in machine.succeed( + 'su - test7 -c "SSH_AUTH_SOCK=HOLEY doas env"' + ): + raise Exception("failed to exclude SSH_AUTH_SOCK") + ''; + } +)