diff --git a/nixos/modules/security/pam.nix b/nixos/modules/security/pam.nix index 2ff08cbfde81..acd0673877b8 100644 --- a/nixos/modules/security/pam.nix +++ b/nixos/modules/security/pam.nix @@ -287,6 +287,18 @@ let ''; }; + rssh = lib.mkOption { + default = false; + type = lib.types.bool; + description = '' + If set, the calling user's SSH agent is used to authenticate + against the configured keys. This module works in a manner + similar to pam_ssh_agent_auth, but supports a wider range + of SSH key types, including those protected by security + keys (FIDO2). + ''; + }; + duoSecurity = { enable = lib.mkOption { default = false; @@ -673,6 +685,7 @@ let { name = "ssh_agent_auth"; enable = config.security.pam.sshAgentAuth.enable && cfg.sshAgentAuth; control = "sufficient"; modulePath = "${pkgs.pam_ssh_agent_auth}/libexec/pam_ssh_agent_auth.so"; settings = { file = lib.concatStringsSep ":" config.security.pam.sshAgentAuth.authorizedKeysFiles; }; } + (let inherit (config.security.pam) rssh; in { name = "rssh"; enable = rssh.enable && cfg.rssh; control = "sufficient"; modulePath = "${pkgs.pam_rssh}/lib/libpam_rssh.so"; inherit (rssh) settings; }) (let p11 = config.security.pam.p11; in { name = "p11"; enable = cfg.p11Auth; control = p11.control; modulePath = "${pkgs.pam_p11}/lib/security/pam_p11.so"; args = [ "${pkgs.opensc}/lib/opensc-pkcs11.so" ]; }) @@ -950,8 +963,9 @@ let value.source = pkgs.writeText "${name}.pam" service.text; }; - optionalSudoConfigForSSHAgentAuth = lib.optionalString config.security.pam.sshAgentAuth.enable '' - # Keep SSH_AUTH_SOCK so that pam_ssh_agent_auth.so can do its magic. + optionalSudoConfigForSSHAgentAuth = lib.optionalString + (config.security.pam.sshAgentAuth.enable || config.security.pam.rssh.enable) '' + # Keep SSH_AUTH_SOCK so that pam_ssh_agent_auth.so and libpam_rssh.so can do their magic. Defaults env_keep+=SSH_AUTH_SOCK ''; @@ -1068,6 +1082,55 @@ in }; }; + security.pam.rssh = { + enable = lib.mkEnableOption "authenticating using a signature performed by the ssh-agent"; + + settings = lib.mkOption { + type = lib.types.submodule { + freeformType = moduleSettingsType; + options = { + auth_key_file = lib.mkOption { + type = with lib.types; nullOr nonEmptyStr; + description = '' + Path to file with trusted public keys in OpenSSH's `authorized_keys` format. The following + variables are expanded to the respective PAM items: + + - `service`: `PAM_SERVICE`, the service name, + - `user`: `PAM_USER`, the username of the entity under whose identity service will be given, + - `tty`: `PAM_TTY`, the terminal name, + - `rhost`: `PAM_RHOST`, the requesting hostname, and + - `ruser`: `PAM_RUSER`, the requesting entity. + + These PAM items are explained in {manpage}`pam_get_item(3)`. + + Variables may be specified as `$var`, `''${var}` or `''${var:defaultValue}`. + + ::: {.note} + Specifying user-writeable files here results in an insecure configuration: a malicious process + can then edit such an `authorized_keys` file and bypass the ssh-agent-based authentication. + + This option is ignored if {option}`security.pam.rssh.settings.authorized_keys_command` is set. + + If both this option and {option}`security.pam.rssh.settings.authorized_keys_command` are unset, + the keys will be read from `''${HOME}/.ssh/authorized_keys`, which should be considered + insecure. + ''; + default = "/etc/ssh/authorized_keys.d/$ruser"; + }; + }; + }; + + default = { }; + description = '' + Options to pass to the pam_rssh module. Refer to + + for supported values. + + ${moduleSettingsDescription} + ''; + }; + }; + security.pam.enableOTPW = lib.mkEnableOption "the OTPW (one-time password) PAM module"; security.pam.dp9ik = { @@ -1512,16 +1575,30 @@ in Did you forget to set `services.openssh.enable` ? ''; } + { + assertion = with config.security.pam.rssh; + enable -> (settings.auth_key_file or null != null || settings.authorized_keys_command or null != null); + message = '' + security.pam.rssh.enable requires either security.pam.rssh.settings.auth_key_file or + security.pam.rssh.settings.authorized_keys_command to be set. + ''; + } ]; warnings = lib.optional - (with lib; with config.security.pam.sshAgentAuth; + (with config.security.pam.sshAgentAuth; enable && lib.any (s: lib.hasPrefix "%h" s || lib.hasPrefix "~" s) authorizedKeysFiles) ''config.security.pam.sshAgentAuth.authorizedKeysFiles contains files in the user's home directory. Specifying user-writeable files there result in an insecure configuration: a malicious process can then edit such an authorized_keys file and bypass the ssh-agent-based authentication. See https://github.com/NixOS/nixpkgs/issues/31611 + '' ++ lib.optional + (with config.security.pam.rssh; + enable && settings.auth_key_file or null != null && settings.authorized_keys_command or null != null) '' + security.pam.rssh.settings.auth_key_file will be ignored as + security.pam.rssh.settings.authorized_keys_command has been specified. + Explictly set the former to null to silence this warning. ''; environment.systemPackages =