From 2942c465b9b82287dc3c034a965f4c29c305673f Mon Sep 17 00:00:00 2001
From: Daniel Barlow <dan@telent.net>
Date: Thu, 10 Aug 2023 22:53:21 +0100
Subject: [PATCH] add ssh module

---
 examples/rotuer.nix     | 21 ++---------------
 modules/ssh/default.nix | 50 +++++++++++++++++++++++++++++++++++++++++
 modules/ssh/ssh.nix     | 42 ++++++++++++++++++++++++++++++++++
 3 files changed, 94 insertions(+), 19 deletions(-)
 create mode 100644 modules/ssh/default.nix
 create mode 100644 modules/ssh/ssh.nix

diff --git a/examples/rotuer.nix b/examples/rotuer.nix
index 293546c..9351931 100644
--- a/examples/rotuer.nix
+++ b/examples/rotuer.nix
@@ -50,6 +50,7 @@ in rec {
     ../modules/hostapd
     ../modules/bridge
     ../modules/ntp
+    ../modules/ssh
   ];
   rootfsType = "jffs2";
   hostname = "rotuer";
@@ -95,25 +96,7 @@ in rec {
     makestep = { threshold = 1.0; limit = 3; };
   };
 
-  services.sshd = longrun {
-    name = "sshd";
-    # env -i clears the environment so we don't pass anything weird to
-    # ssh sessions. Dropbear params are
-    # -e  pass environment to child
-    # -E  log to stderr
-    # -R  create hostkeys if needed
-    # -P  pid-file
-    # -F  don't fork into background
-
-    run = ''
-      if test -d /persist; then
-        mkdir -p /persist/secrets/dropbear
-        ln -s /persist/secrets/dropbear /run
-      fi
-      PATH=${lib.makeBinPath config.defaultProfile.packages}:/bin
-      exec env -i ENV=/etc/ashrc PATH=$PATH ${dropbear}/bin/dropbear -e -E -R -P /run/dropbear.pid  -F
-    '';
-  };
+  services.sshd = svc.ssh.build { };
 
   users.root = secrets.root;
 
diff --git a/modules/ssh/default.nix b/modules/ssh/default.nix
new file mode 100644
index 0000000..cb1305f
--- /dev/null
+++ b/modules/ssh/default.nix
@@ -0,0 +1,50 @@
+## Secure Shell
+## ============
+##
+## Provide SSH service using Dropbear
+
+{ lib, pkgs, config, ...}:
+let
+  inherit (lib) mkOption types;
+  inherit (pkgs) liminix;
+  mkBoolOption = description : mkOption {
+    type = types.bool;
+    inherit description;
+    default = true;
+  };
+
+in {
+  options = {
+    system.service.ssh = mkOption {
+      type = liminix.lib.types.serviceDefn;
+    };
+  };
+  config.system.service = {
+    ssh = liminix.callService ./ssh.nix {
+      address = mkOption {
+        type = types.nullOr types.str;
+        default = null;
+        description = "Listen on specified address";
+        example = "127.0.0.1";
+      };
+      port = mkOption {
+        type = types.port;
+        default = 22;
+        description = "Listen on specified TCP port";
+      };
+      allowRoot = mkBoolOption "Allow root to login";
+      allowPasswordLogin = mkBoolOption "Allow login using password (disable for public key auth only)";
+      allowPasswordLoginForRoot = mkBoolOption "Allow root to login using password (disable for public key auth only)";
+      allowLocalPortForward = mkBoolOption "Enable local port forwarding";
+      allowRemotePortForward = mkBoolOption "Enable remote port forwarding";
+      allowRemoteConnectionToForwardedPorts = mkOption {
+        type = types.bool; default = false;
+        description = "Allow remote hosts to connect to local forwarded ports (by default they are bound to loopback)";
+      };
+      extraConfig = mkOption {
+        type = types.separatedString " ";
+        default = "";
+      };
+    };
+  };
+}
diff --git a/modules/ssh/ssh.nix b/modules/ssh/ssh.nix
new file mode 100644
index 0000000..ef5942e
--- /dev/null
+++ b/modules/ssh/ssh.nix
@@ -0,0 +1,42 @@
+{
+  liminix
+, dropbear
+, serviceFns
+, lib
+}:
+p :
+let
+  inherit (liminix.services) longrun;
+  inherit (lib) concatStringsSep;
+  options =
+    [
+      "-e" #  pass environment to child
+      "-E" #  log to stderr
+      "-R" #  create hostkeys if needed
+      "-P /run/dropbear.pid"
+      "-F" #  don't fork into background
+    ] ++
+    (lib.optional (! p.allowRoot) "-w") ++
+    (lib.optional (! p.allowPasswordLogin) "-s") ++
+    (lib.optional (! p.allowPasswordLoginForRoot) "-g") ++
+    (lib.optional (! p.allowLocalPortForward) "-j") ++
+    (lib.optional (! p.allowRemotePortForward) "-k") ++
+    (lib.optional (! p.allowRemoteConnectionToForwardedPorts) "-a") ++
+    [(if p.address != null
+      then "-p ${p.address}:${p.port}"
+      else "-p ${builtins.toString p.port}")] ++
+    [p.extraConfig];
+in
+longrun {
+  name = "sshd";
+  # env -i clears the environment so we don't pass anything weird to
+  # ssh sessions
+  run = ''
+    if test -d /persist; then
+      mkdir -p /persist/secrets/dropbear
+      ln -s /persist/secrets/dropbear /run
+    fi
+    . /etc/profile # sets PATH but do we need this?  it's the same file as ashrc
+    exec env -i ENV=/etc/ashrc PATH=$PATH ${dropbear}/bin/dropbear ${concatStringsSep " " options}
+  '';
+}