secrets: allow extending generate-secrets

`generate-secrets` is no longer a monolithic script. Instead, it's
composed of the values of option `nix-bitcoin.generateSecretsCmds`.

This has the following advantages:
- generate-secrets is now extensible by users
- Only secrets of enabled services are generated
- RPC IPs in the `lnd` and `loop` certs are no longer hardcoded.

Secrets are no longer automatically generated when entering nix-shell.
Instead, they are generated before deployment (via `krops-deploy`)
because secrets generation is now dependant on the node configuration.

helper/makeShell.nix

@@ -21,12 +21,22 @@ stdenv.mkDerivation rec {
       ${toString ./fetch-release}
     }
 
-    krops-deploy() {
+    generate-secrets() {(
+      set -euo pipefail
+      genSecrets=$(nix-build --no-out-link -I nixos-config="${cfgDir}/configuration.nix" \
+                   '<nixpkgs/nixos>' -A config.nix-bitcoin.generateSecretsScript)
+      mkdir -p "${cfgDir}/secrets"
+      (cd "${cfgDir}/secrets"; $genSecrets)
+    )}
+
+    krops-deploy() {(
+      set -euo pipefail
+      generate-secrets
       # Ensure strict permissions on secrets/ directory before rsyncing it to
       # the target machine
       chmod 700 "${cfgDir}/secrets"
       $(nix-build --no-out-link "${cfgDir}/krops/deploy.nix")
-    }
+    )}
 
     # Print logo if
     # 1. stdout is a TTY, i.e. we're not piping the output

modules/backups.nix

@@ -98,6 +98,12 @@ in {
       };
 
       nix-bitcoin.secrets.backup-encryption-env.user = "root";
+      nix-bitcoin.generateSecretsCmds.backups = ''
+        makePasswordSecret backup-encryption-password
+        if [[ backup-encryption-password -nt backup-encryption-env ]]; then
+           echo "PASSPHRASE=$(cat backup-encryption-password)" > backup-encryption-env
+        fi
+      '';
 
       services.backups.postgresqlDatabases = mkIf config.services.btcpayserver.enable [ "btcpaydb" ];
     };

modules/bitcoind.nix

@@ -394,15 +394,22 @@ in {
     };
     users.groups.${cfg.group} = {};
     users.groups.bitcoinrpc-public = {};
+
     nix-bitcoin.operator.groups = [ cfg.group ];
 
-    nix-bitcoin.secrets.bitcoin-rpcpassword-privileged.user = cfg.user;
-    nix-bitcoin.secrets.bitcoin-rpcpassword-public = {
-      user = cfg.user;
-      group = "bitcoinrpc-public";
-    };
+    nix-bitcoin.secrets = {
+      bitcoin-rpcpassword-privileged.user = cfg.user;
+      bitcoin-rpcpassword-public = {
+        user = cfg.user;
+        group = "bitcoinrpc-public";
+      };
 
-    nix-bitcoin.secrets.bitcoin-HMAC-privileged.user = cfg.user;
-    nix-bitcoin.secrets.bitcoin-HMAC-public.user = cfg.user;
+      bitcoin-HMAC-privileged.user = cfg.user;
+      bitcoin-HMAC-public.user = cfg.user;
+    };
+    nix-bitcoin.generateSecretsCmds.bitcoind = ''
+      makeBitcoinRPCPassword privileged
+      makeBitcoinRPCPassword public
+    '';
   };
 }

modules/btcpayserver.nix

@@ -253,5 +253,8 @@ in {
       };
       bitcoin-HMAC-btcpayserver.user = cfg.bitcoind.user;
     };
+    nix-bitcoin.generateSecretsCmds.btcpayserver = ''
+      makeBitcoinRPCPassword btcpayserver
+    '';
   };
 }

modules/joinmarket-ob-watcher.nix

@@ -131,5 +131,8 @@ in {
       bitcoin-rpcpassword-joinmarket-ob-watcher.user = cfg.user;
       bitcoin-HMAC-joinmarket-ob-watcher.user = bitcoind.user;
     };
+    nix-bitcoin.generateSecretsCmds.joinmarket-ob-watcher = ''
+      makeBitcoinRPCPassword joinmarket-ob-watcher
+    '';
   };
 }

modules/joinmarket.nix

@@ -305,6 +305,9 @@ in {
     };
 
     nix-bitcoin.secrets.jm-wallet-password.user = cfg.user;
+    nix-bitcoin.generateSecretsCmds.joinmarket = ''
+      makePasswordSecret jm-wallet-password
+    '';
   }
 
   (mkIf cfg.yieldgenerator.enable {

modules/lightning-loop.nix

@@ -112,5 +112,8 @@ in {
        loop-key.user = lnd.user;
        loop-cert.user = lnd.user;
      };
+     nix-bitcoin.generateSecretsCmds.lightning-loop = ''
+       makeCert loop '${optionalString (cfg.rpcAddress != "localhost") "IP:${cfg.rpcAddress}"}'
+    '';
   };
 }

modules/liquid.nix

@@ -247,5 +247,8 @@ in {
     nix-bitcoin.operator.groups = [ cfg.group ];
 
     nix-bitcoin.secrets.liquid-rpcpassword.user = cfg.user;
+    nix-bitcoin.generateSecretsCmds.liquid = ''
+      makePasswordSecret liquid-rpcpassword
+    '';
   };
 }

modules/lnd.nix

@@ -293,7 +293,14 @@ in {
       lnd-wallet-password.user = cfg.user;
       lnd-key.user = cfg.user;
       lnd-cert.user = cfg.user;
-      lnd-cert.permissions = "0444"; # world readable
+      lnd-cert.permissions = "444"; # world readable
     };
+    # Advantages of manually pre-generating certs:
+    # - Reduces dynamic state
+    # - Enables deployment of a mesh of server plus client nodes with predefined certs
+    nix-bitcoin.generateSecretsCmds.lnd = ''
+      makePasswordSecret lnd-wallet-password
+      makeCert lnd '${optionalString (cfg.rpcAddress != "localhost") "IP:${cfg.rpcAddress}"}'
+    '';
   };
 }

modules/secrets/secrets.nix

@@ -2,9 +2,6 @@
 
 with lib;
 let
-  cfg = config.nix-bitcoin;
-in
-{
   options.nix-bitcoin = {
     secretsDir = mkOption {
       type = types.path;
@@ -29,6 +26,14 @@ in
       '';
     };
 
+    generateSecretsCmds = mkOption {
+      type = types.attrsOf types.str;
+      default = {};
+      description = ''
+        Bash expressions for generating secrets.
+      '';
+    };
+
     # Currently, this is used only by ../deployment/nixops.nix
     deployment.secretsDir = mkOption {
       type = types.path;
@@ -72,8 +77,68 @@ in
          - Set `nix-bitcoin.secretsSetupMethod = "manual"` if you want to manually setup secrets
       '';
     };
+
+    generateSecretsScript = mkOption {
+      internal = true;
+      default = let
+        rpcauthSrc = builtins.fetchurl {
+          url = "https://raw.githubusercontent.com/bitcoin/bitcoin/d6cde007db9d3e6ee93bd98a9bbfdce9bfa9b15b/share/rpcauth/rpcauth.py";
+          sha256 = "189mpplam6yzizssrgiyv70c9899ggh8cac76j4n7v0xqzfip07n";
+        };
+        rpcauth = pkgs.writers.writeBash "rpcauth" ''
+          exec ${pkgs.python3}/bin/python ${rpcauthSrc} "$@"
+        '';
+      in pkgs.writers.writeBash "generate-secrets" ''
+        set -euo pipefail
+
+        export PATH=${lib.makeBinPath (with pkgs; [ coreutils gnugrep ])}
+
+        makePasswordSecret() {
+          # Passwords have alphabet {a-z, A-Z, 0-9} and ~119 bits of entropy
+          [[ -e $1 ]] || ${pkgs.pwgen}/bin/pwgen -s 20 1 > "$1"
+        }
+        makeBitcoinRPCPassword() {
+          user=$1
+          file=bitcoin-rpcpassword-$user
+          HMACfile=bitcoin-HMAC-$user
+          makePasswordSecret "$file"
+          if [[ $file -nt $HMACfile ]]; then
+            ${rpcauth} $user $(cat "$file") | grep rpcauth | cut -d ':' -f 2 > "$HMACfile"
+          fi
+        }
+        makeCert() {
+          name=$1
+          # Add leading comma if not empty
+          extraAltNames=''${2:+,}''${2:-}
+          if [[ ! -e $name-key ]]; then
+            # Create new key and cert
+            doMakeCert "-newkey ec -pkeyopt ec_paramgen_curve:prime256v1 -nodes -keyout $name-key"
+          elif [[ ! -e $name-cert \
+                  || $(cat "$name-cert-alt-names" 2>/dev/null) != $extraAltNames ]]; then
+            # Create cert from existing key
+            doMakeCert "-key $name-key"
+          fi;
+        }
+        doMakeCert() {
+           # This fn uses global variables `name` and `extraAltNames`
+           keyOpts=$1
+           ${pkgs.openssl}/bin/openssl req -x509 \
+             -sha256 -days 3650 $keyOpts -out "$name-cert"  \
+             -subj "/CN=localhost/O=$name" \
+             -addext "subjectAltName=DNS:localhost,IP:127.0.0.1$extraAltNames"
+           echo "$extraAltNames" > "$name-cert-alt-names"
+        }
+
+        umask u=rw,go=
+        ${builtins.concatStringsSep "\n" (builtins.attrValues cfg.generateSecretsCmds)}
+      '';
+    };
   };
 
+  cfg = config.nix-bitcoin;
+in {
+  inherit options;
+
   config = {
     # This target is active when secrets have been setup successfully.
     systemd.targets.nix-bitcoin-secrets = mkIf (cfg.secretsSetupMethod != "manual") {
@@ -106,7 +171,7 @@ in
           cd "${cfg.secretsDir}"
           chown root: .
           chmod 0700 .
-          ${cfg.pkgs.generate-secrets}
+          ${cfg.generateSecretsScript}
         ''}
 
         setupSecret() {
@@ -140,9 +205,11 @@ in
 
         # Make all other files accessible to root only
         unprocessedFiles=$(comm -23 <(printf '%s\n' *) <(printf '%s\n' "''${processedFiles[@]}" | sort))
-        IFS=$'\n'
-        chown root: $unprocessedFiles
-        chmod 0440 $unprocessedFiles
+        if [[ $unprocessedFiles ]]; then
+          IFS=$'\n'
+          chown root: $unprocessedFiles
+          chmod 0440 $unprocessedFiles
+        fi
 
         # Now make the secrets dir accessible to other users
         chmod 0751 "$dir"

modules/spark-wallet.nix

@@ -83,6 +83,13 @@ in {
       } // nbLib.allowedIPAddresses cfg.enforceTor
         // nbLib.nodejs;
     };
+
     nix-bitcoin.secrets.spark-wallet-login.user = cfg.user;
+    nix-bitcoin.generateSecretsCmds.spark-wallet = ''
+      makePasswordSecret spark-wallet-password
+      if [[ spark-wallet-password -nt spark-wallet-login ]]; then
+         echo "login=spark-wallet:$(cat spark-wallet-password)" > spark-wallet-login
+      fi
+    '';
   };
 }

pkgs/generate-secrets/default.nix

@@ -1,15 +0,0 @@
-{ pkgs }: with pkgs;
-
-let
-  rpcauthSrc = builtins.fetchurl {
-    url = "https://raw.githubusercontent.com/bitcoin/bitcoin/d6cde007db9d3e6ee93bd98a9bbfdce9bfa9b15b/share/rpcauth/rpcauth.py";
-    sha256 = "189mpplam6yzizssrgiyv70c9899ggh8cac76j4n7v0xqzfip07n";
-  };
-  rpcauth = pkgs.writeScriptBin "rpcauth" ''
-    exec ${pkgs.python3}/bin/python ${rpcauthSrc} "$@"
-  '';
-in
-writers.writeBash "generate-secrets" ''
-  export PATH=${lib.makeBinPath [ coreutils pwgen openssl gnugrep rpcauth ]}
-  . ${./generate-secrets.sh} ${./openssl.cnf}
-''

pkgs/generate-secrets/generate-secrets.sh

@@ -1,44 +0,0 @@
-#!/usr/bin/env bash
-
-set -euo pipefail
-
-opensslConf=${1:-openssl.cnf}
-
-makePasswordSecret() {
-    # Passwords have alphabet {a-z, A-Z, 0-9} and ~119 bits of entropy
-    [[ -e $1 ]] || pwgen -s 20 1 > "$1"
-}
-makeHMAC() {
-    user=$1
-    rpcauth $user $(cat bitcoin-rpcpassword-$user) | grep rpcauth | cut -d ':' -f 2 > bitcoin-HMAC-$user
-}
-
-makePasswordSecret bitcoin-rpcpassword-privileged
-makePasswordSecret bitcoin-rpcpassword-btcpayserver
-makePasswordSecret bitcoin-rpcpassword-joinmarket-ob-watcher
-makePasswordSecret bitcoin-rpcpassword-public
-makePasswordSecret lnd-wallet-password
-makePasswordSecret liquid-rpcpassword
-makePasswordSecret spark-wallet-password
-makePasswordSecret backup-encryption-password
-makePasswordSecret jm-wallet-password
-
-[[ -e bitcoin-HMAC-privileged ]] || makeHMAC privileged
-[[ -e bitcoin-HMAC-public ]] || makeHMAC public
-[[ -e bitcoin-HMAC-btcpayserver ]] || makeHMAC btcpayserver
-[[ -e bitcoin-HMAC-joinmarket-ob-watcher ]] || makeHMAC joinmarket-ob-watcher
-[[ -e spark-wallet-login   ]] || echo "login=spark-wallet:$(cat spark-wallet-password)" > spark-wallet-login
-[[ -e backup-encryption-env ]] || echo "PASSPHRASE=$(cat backup-encryption-password)" > backup-encryption-env
-
-makeCert() {
-  if [[ ! -e $name-key || ! -e $name-cert ]]; then
-    openssl req -x509 -newkey ec -pkeyopt ec_paramgen_curve:prime256v1 \
-      -sha256 -days 3650 -nodes -keyout "$name-key" -out "$name-cert" \
-      -subj "/CN=localhost/O=$name" \
-      -addext "subjectAltName=DNS:localhost,IP:127.0.0.1,IP:169.254.1.14,IP:169.254.1.22"
-    # TODO: Remove hardcoded lnd, loopd netns ips
-  fi
-}
-
-makeCert lnd
-makeCert loop

pkgs/generate-secrets/update-and-generate.nix

@@ -1,10 +0,0 @@
-{ pkgs }: with pkgs;
-
-let
-  generate-secrets = callPackage ./. {};
-in
-writeScript "make-secrets" ''
-  # Update from old secrets format
-  [[ -e secrets.nix ]] && . ${./update-secrets.sh}
-  ${generate-secrets}
-''

pkgs/generate-secrets/update-secrets.sh

@@ -1,45 +0,0 @@
-#!/usr/bin/env bash
-
-set -eo pipefail
-
-# Update secrets from the old format to the current one where each secret
-# has a local source file.
-
-reportError() {
-    echo "Updating secrets failed. (Error in line $1)"
-    echo "The secret files have been moved to secrets/old-secrets"
-}
-trap 'reportError $LINENO' ERR
-
-echo "Updating old secrets to the current format."
-
-mkdir old-secrets
-# move all files into old-secrets
-shopt -s extglob dotglob
-mv !(old-secrets) old-secrets
-shopt -u dotglob
-
-secrets=$(cat old-secrets/secrets.nix)
-
-extractPassword() {
-    pwName="$1"
-    destFile="${2:-$pwName}"
-    echo "$secrets" | sed -nE "s/.*?$pwName = \"(.*?)\".*/\1/p" > "$destFile"
-}
-
-rename() {
-    old="old-secrets/$1"
-    if [[ -e $old ]]; then
-        cp "$old" "$2"
-    fi
-}
-
-extractPassword bitcoinrpcpassword bitcoin-rpcpassword
-extractPassword lnd-wallet-password
-extractPassword liquidrpcpassword liquid-rpcpassword
-extractPassword spark-wallet-password
-
-rename lnd.key lnd-key
-rename lnd.cert lnd-cert
-
-rm -r old-secrets