Merge branch 'service-hardening'

README.md

@@ -1,7 +1,7 @@
 nix-bitcoin
 ===
 
-Nix packages and nixos modules for easily installing Bitcoin nodes and higher layer protocols.
+Nix packages and nixos modules for easily installing Bitcoin nodes and higher layer protocols with an emphasis on security.
 This is a work in progress - don't expect it to be bug free or secure.
 
 The default configuration sets up a Bitcoin Core node and c-lightning. The user can enable spark-wallet in `configuration.nix` to make c-lightning accessible with a smartphone using spark-wallet.
@@ -49,6 +49,19 @@ The easiest way is to run `nix-shell` (on a Linux machine) in the nix-bitcoin di
 Fix the FIXMEs in configuration.nix and deploy with nixops in nix-shell.
 See [install.md](docs/install.md) for a detailed tutorial.
 
+Security
+---
+* Nix package manager, NixOS and packages can be built from source to reduce reliance on binary caches.
+* Builds happen in a [sandboxed environment](https://nixos.org/nix/manual/).
+* Packages dependencies are [pinned](pkgs/nixpkgs-pinned.nix). Most packages are built from the [nixos stable channel](https://github.com/NixOS/nixpkgs-channels/tree/nixos-19.03), with a few exceptions that are built from the nixpkgs unstable channel.
+* nix-bitcoin merge commits are signed.
+* nix-bitcoin is built with a [hardened kernel](https://github.com/NixOS/nixpkgs/blob/master/nixos/modules/profiles/hardened.nix) by default.
+* Services operate with least privileges. They each have their own user and are restricted further with [systemd options](modules/nix-bitcoin-services.nix).
+* There's a non-root user *operator* to interact with the various services.
+
+Note that nix-bitcoin is still experimental.
+Also, by design if the machine you're deploying *from* is insecure, there is nothing nix-bitcoin can do to protect itself.
+
 Hardware requirements
 ---
 * Disk space: 300 GB (235GB for Bitcoin blockchain + some room)

docs/install.md

@@ -169,6 +169,10 @@ This is borrowed from the [NixOS manual](https://nixos.org/nixos/manual/index.ht
 	swapon /dev/sda2
 	```
 
+4. Option 3: Set up encrypted partitions:
+
+    Follow the guide at https://gist.github.com/martijnvermaat/76f2e24d0239470dd71050358b4d5134.
+
 5. Generate NixOS config
 
 	```

modules/bitcoind.nix

@@ -3,6 +3,7 @@
 with lib;
 
 let
+  nix-bitcoin-services = pkgs.callPackage ./nix-bitcoin-services.nix { };
   cfg = config.services.bitcoind;
   pidFile = "${cfg.dataDir}/bitcoind.pid";
   configFile = pkgs.writeText "bitcoin.conf" ''
@@ -192,6 +193,7 @@ in {
           to stay under the specified target size in MiB)
         '';
       };
+      enforceTor =  nix-bitcoin-services.enforceTor;
     };
   };
 
@@ -235,7 +237,11 @@ in {
 
         # Permission for preStart
         PermissionsStartOnly = "true";
-      };
+      } // nix-bitcoin-services.defaultHardening
+        // (if cfg.enforceTor
+          then nix-bitcoin-services.allowTor
+          else nix-bitcoin-services.allowAnyIP
+        );
     };
     systemd.services.bitcoind-import-banlist = {
       description = "Bitcoin daemon banlist importer";
@@ -269,16 +275,10 @@ in {
         ExecStart = "${pkgs.bash}/bin/bash ${pkgs.banlist}/bin/banlist ${pkgs.altcoins.bitcoind}";
         StateDirectory = "bitcoind";
 
-        # Hardening measures
-        PrivateTmp = "true";
-        ProtectSystem = "full";
-        NoNewPrivileges = "true";
-        PrivateDevices = "true";
-        MemoryDenyWriteExecute = "true";
-
         # Permission for preStart
         PermissionsStartOnly = "true";
-      };
+      } // nix-bitcoin-services.defaultHardening
+        // nix-bitcoin-services.allowTor;
     };
 
     users.users.${cfg.user} = {

modules/clightning.nix

@@ -3,6 +3,7 @@
 with lib;
 
 let
+  nix-bitcoin-services = pkgs.callPackage ./nix-bitcoin-services.nix { };
   cfg = config.services.clightning;
   configFile = pkgs.writeText "config" ''
     autolisten=${if cfg.autolisten then "true" else "false"}
@@ -56,6 +57,7 @@ in {
       default = "/var/lib/clightning";
       description = "The data directory for clightning.";
     };
+    enforceTor =  nix-bitcoin-services.enforceTor;
   };
 
   config = mkIf cfg.enable {
@@ -93,12 +95,11 @@ in {
         User = "clightning";
         Restart = "on-failure";
         RestartSec = "10s";
-        PrivateTmp = "true";
-        ProtectSystem = "full";
-        NoNewPrivileges = "true";
-        PrivateDevices = "true";
-        MemoryDenyWriteExecute = "true";
-      };
+      } // nix-bitcoin-services.defaultHardening
+        // (if cfg.enforceTor
+          then nix-bitcoin-services.allowTor
+          else nix-bitcoin-services.allowAnyIP
+        );
     };
   };
 }

modules/electrs.nix

@@ -3,6 +3,7 @@
 with lib;
 
 let
+  nix-bitcoin-services = pkgs.callPackage ./nix-bitcoin-services.nix { };
   cfg = config.services.electrs;
   index-batch-size = "${if cfg.high-memory then "" else "--index-batch-size=10"}";
   jsonrpc-import = "${if cfg.high-memory then "" else "--jsonrpc-import"}";
@@ -42,6 +43,7 @@ in {
         default = 50003;
         description = "Override the default port on which to listen for connections.";
     };
+    enforceTor =  nix-bitcoin-services.enforceTor;
   };
 
   config = mkIf cfg.enable {
@@ -74,11 +76,11 @@ in {
         User = "electrs";
         Restart = "on-failure";
         RestartSec = "10s";
-        PrivateTmp = "true";
-        ProtectSystem = "full";
-        NoNewPrivileges = "true";
-        PrivateDevices = "true";
-      };
+      } // nix-bitcoin-services.defaultHardening
+        // (if cfg.enforceTor
+          then nix-bitcoin-services.allowTor
+          else nix-bitcoin-services.allowAnyIP
+        );
     };
 
     services.nginx = {

modules/lightning-charge.nix

@@ -3,6 +3,7 @@
 with lib;
 
 let
+  nix-bitcoin-services = pkgs.callPackage ./nix-bitcoin-services.nix { };
   cfg = config.services.lightning-charge;
 in {
   options.services.lightning-charge = {
@@ -37,11 +38,9 @@ in {
           User = "clightning";
           Restart = "on-failure";
           RestartSec = "10s";
-          PrivateTmp = "true";
-          ProtectSystem = "full";
-          NoNewPrivileges = "true";
-          PrivateDevices = "true";
-      };
+      } // nix-bitcoin-services.defaultHardening
+        // nix-bitcoin-services.nodejs
+        // nix-bitcoin-services.allowTor;
     };
   };
 }

modules/liquid.nix

@@ -3,6 +3,7 @@
 with lib;
 
 let
+  nix-bitcoin-services = pkgs.callPackage ./nix-bitcoin-services.nix { };
   cfg = config.services.liquidd;
   pidFile = "${cfg.dataDir}/liquidd.pid";
   configFile = pkgs.writeText "liquid.conf" ''
@@ -165,6 +166,7 @@ in {
           to stay under the specified target size in MiB)
         '';
       };
+      enforceTor =  nix-bitcoin-services.enforceTor;
     };
   };
 
@@ -195,28 +197,23 @@ in {
         PIDFile = "${pidFile}";
         Restart = "on-failure";
 
-        # Hardening measures
-        PrivateTmp = "true";
-        ProtectSystem = "full";
-        NoNewPrivileges = "true";
-        PrivateDevices = "true";
-        MemoryDenyWriteExecute = "true";
-
         # Permission for preStart
         PermissionsStartOnly = "true";
-      };
+      } // nix-bitcoin-services.defaultHardening
+        // (if cfg.enforceTor
+          then nix-bitcoin-services.allowTor
+          else nix-bitcoin-services.allowAnyIP
+        );
     };
     users.users.${cfg.user} = {
       name = cfg.user;
-      #uid  = config.ids.uids.liquid;
       group = cfg.group;
       extraGroups = [ "keys" ];
       description = "Liquid daemon user";
       home = cfg.dataDir;
     };
     users.groups.${cfg.group} = {
       name = cfg.group;
-      #gid = config.ids.gids.liquid;
     };
   };
 }

modules/nanopos.nix

@@ -3,6 +3,7 @@
 with lib;
 
 let
+  nix-bitcoin-services = pkgs.callPackage ./nix-bitcoin-services.nix { };
   cfg = config.services.nanopos;
   defaultItemsFile = pkgs.writeText "items.yaml" ''
     tea:
@@ -73,11 +74,9 @@ in {
         User = "nanopos";
         Restart = "on-failure";
         RestartSec = "10s";
-        PrivateTmp = "true";
-        ProtectSystem = "full";
-        NoNewPrivileges = "true";
-        PrivateDevices = "true";
-      };
+      } // nix-bitcoin-services.defaultHardening
+        // nix-bitcoin-services.nodejs
+        // nix-bitcoin-services.allowTor;
     };
   };
 }

modules/nix-bitcoin-services.nix

@@ -0,0 +1,44 @@
+{ config, lib, pkgs, ... }:
+
+with lib;
+
+let
+  defaultHardening = {
+      PrivateTmp = "true";
+      ProtectSystem = "full";
+      ProtectHome = "true";
+      NoNewPrivileges = "true";
+      PrivateDevices = "true";
+      MemoryDenyWriteExecute = "true";
+      ProtectKernelTunables = "true";
+      ProtectKernelModules = "true";
+      ProtectControlGroups = "true";
+      RestrictAddressFamilies = "AF_UNIX AF_INET AF_INET6";
+      RestrictNamespaces = "true";
+      LockPersonality = "true";
+      IPAddressDeny = "any";
+  };
+in
+{
+  inherit defaultHardening;
+  # nodejs applications apparently rely on memory write execute
+  nodejs = { MemoryDenyWriteExecute = "false"; };
+  # Allow tor traffic. Allow takes precedence over Deny.
+  allowTor = {
+    IPAddressAllow = "127.0.0.1/32 ::1/128";
+  };
+  # Allow any traffic
+  allowAnyIP = { IPAddressAllow = "any"; };
+
+   enforceTor = mkOption {
+     type = types.bool;
+     default = false;
+     description = ''
+       "Whether to force Tor on a service by only allowing connections from and
+       to 127.0.0.1;";
+     '';
+   };
+}
+
+
+

modules/nix-bitcoin-webindex.nix

@@ -3,6 +3,7 @@
 with lib;
 
 let
+  nix-bitcoin-services = pkgs.callPackage ./nix-bitcoin-services.nix { };
   cfg = config.services.nix-bitcoin-webindex;
   indexFile = pkgs.writeText "index.html" ''
     <html>
@@ -43,6 +44,7 @@ in {
         If enabled, the webindex service will be installed.
       '';
     };
+    enforceTor =  nix-bitcoin-services.enforceTor;
   };
 
   config = mkIf cfg.enable {
@@ -80,7 +82,11 @@ in {
         RemainAfterExit="yes";
         Restart = "on-failure";
         RestartSec = "10s";
-      };
+      } // nix-bitcoin-services.defaultHardening
+        // (if cfg.enforceTor
+          then nix-bitcoin-services.allowTor
+          else nix-bitcoin-services.allowAnyIP
+        );
     };
   };
 }

modules/nix-bitcoin.nix

@@ -60,6 +60,7 @@ in {
     services.bitcoind.sysperms = if config.services.electrs.enable then true else null;
     services.bitcoind.disablewallet = if config.services.electrs.enable then true else null;
     services.bitcoind.proxy = config.services.tor.client.socksListenAddress;
+    services.bitcoind.enforceTor = true;
     services.bitcoind.port = 8333;
     services.bitcoind.rpcuser = "bitcoinrpc";
     services.bitcoind.extraConfig = ''
@@ -82,6 +83,7 @@ in {
     # clightning
     services.clightning.bitcoin-rpcuser = config.services.bitcoind.rpcuser;
     services.clightning.proxy = config.services.tor.client.socksListenAddress;
+    services.clightning.enforceTor = true;
     services.clightning.always-use-proxy = true;
     services.clightning.bind-addr = "127.0.0.1:9735";
     services.tor.hiddenServices.clightning = {
@@ -128,6 +130,8 @@ in {
       };
     };
 
+    services.nix-bitcoin-webindex.enforceTor = true;
+
     services.liquidd.rpcuser = "liquidrpc";
     services.liquidd.prune = 1000;
     services.liquidd.extraConfig = "
@@ -136,16 +140,18 @@ in {
     ";
     services.liquidd.listen = true;
     services.liquidd.proxy = config.services.tor.client.socksListenAddress;
+    services.liquidd.enforceTor = true;
     services.liquidd.port = 7042;
     services.tor.hiddenServices.liquidd = {
       map = [{
         port = config.services.liquidd.port; toPort = config.services.liquidd.port;
       }];
       version = 3;
     };
-     
+
     services.spark-wallet.onion-service = true;
     services.electrs.port = 50001;
+    services.electrs.enforceTor = true;
     services.electrs.onionport = 50002;
     services.electrs.nginxport = 50003;
     services.electrs.high-memory = false;

modules/onion-chef.nix

@@ -8,6 +8,7 @@
 with lib;
 
 let
+  nix-bitcoin-services = pkgs.callPackage ./nix-bitcoin-services.nix { };
   cfg = config.services.onion-chef;
   dataDir = "/var/lib/onion-chef/";
   onion-chef-script = pkgs.writeScript "onion-chef.sh" ''
@@ -77,11 +78,7 @@ in {
         ExecStart = "${pkgs.bash}/bin/bash ${onion-chef-script}";
         User = "root";
         Type = "oneshot";
-        PrivateTmp = "true";
-        ProtectSystem = "full";
-        NoNewPrivileges = "true";
-        PrivateDevices = "true";
-      };
+      } // nix-bitcoin-services.defaultHardening;
     };
   };
 }