From d522a46f1dd9e2f6a601dde645187db8607a4dc5 Mon Sep 17 00:00:00 2001
From: oddlama <oddlama@oddlama.org>
Date: Fri, 14 Apr 2023 14:32:17 +0200
Subject: [PATCH] refactor(wireguard): extract cross-host aggregation functions
 into extraLib

---
 README.md                            |   7 +
 hosts/ward/net.nix                   |  10 +-
 modules/wireguard.nix                | 250 ++++++++++++---------------
 nix/apps/generate-wireguard-keys.nix |  90 +++++-----
 nix/apps/show-wireguard-qr.nix       |  16 +-
 nix/lib.nix                          |  61 +++++++
 6 files changed, 239 insertions(+), 195 deletions(-)

diff --git a/README.md b/README.md
index 2993955..9061037 100644
--- a/README.md
+++ b/README.md
@@ -37,6 +37,7 @@ This is my personal nix config.
   - `dev-shell.nix` Environment setup for `nix develop` for using this flake
   - `extra-builtins.nix` Extra builtins via nix-plugins to support transparent repository-wide secrets
   - `hosts.nix` Wrapper that extracts all defined hosts from `hosts/`
+  - `lib.nix` Commonly used functionality or helpers that weren't available in the standard library
   - `rage-decrypt.sh` Auxiliary script for repository-wide secrets
   - `secrets.nix` Helper to access repository-wide secrets, used by colmena.nix
 - `secrets/` Global secrets and age identities
@@ -57,6 +58,12 @@ This is my personal nix config.
 - fill net.nix
 - todo: hostid (move to nodeSecrets)
 - generate-initrd-keys
+- generate-wireguard-keys
+
+#### Show QR for external wireguard client
+
+nix run show-wireguard-qr
+then select the host in the fzf menu
 
 #### New secret
 
diff --git a/hosts/ward/net.nix b/hosts/ward/net.nix
index f07f6e4..5d9c0e3 100644
--- a/hosts/ward/net.nix
+++ b/hosts/ward/net.nix
@@ -22,11 +22,13 @@
     };
   };
 
-  extra.wireguard.networks.vms = {
+  extra.wireguard.vms = {
+    server = {
+      enable = true;
+      port = 51822;
+      openFirewall = true;
+    };
     address = ["10.0.0.1/24"];
-    listen = true;
-    listenPort = 51822;
-    openFirewall = true;
     externalPeers = {
       test1 = ["10.0.0.91/32"];
       test2 = ["10.0.0.92/32"];
diff --git a/modules/wireguard.nix b/modules/wireguard.nix
index c423ed0..6b0c78d 100644
--- a/modules/wireguard.nix
+++ b/modules/wireguard.nix
@@ -11,88 +11,50 @@
     (lib)
     any
     attrNames
-    attrValues
     concatMap
     concatMapStrings
     concatStringsSep
-    filter
-    flatten
-    foldl'
-    genAttrs
+    filterAttrs
     head
-    mapAttrs'
     mapAttrsToList
     mdDoc
     mergeAttrs
     mkIf
     mkOption
-    nameValuePair
-    optional
-    recursiveUpdate
+    mkEnableOption
+    optionalAttrs
     splitString
     types
     ;
 
-  inherit (extraLib) duplicates;
+  inherit
+    (extraLib)
+    concatAttrs
+    duplicates
+    ;
 
   cfg = config.extra.wireguard;
 
-  sortedPeers = peerA: peerB:
-    if peerA < peerB
-    then {
-      peer1 = peerA;
-      peer2 = peerB;
-    }
-    else {
-      peer1 = peerB;
-      peer2 = peerA;
-    };
-
   configForNetwork = wgName: wg: let
-    peerPublicKey = peerName: builtins.readFile (../secrets/wireguard + "/${wgName}/keys/${peerName}.pub");
-    peerPrivateKeyFile = peerName: ../secrets/wireguard + "/${wgName}/keys/${peerName}.age";
-    peerPrivateKeySecret = peerName: "wireguard-${wgName}-priv-${peerName}";
+    inherit
+      (extraLib.wireguard wgName)
+      allPeers
+      peerPresharedKeyPath
+      peerPresharedKeySecret
+      peerPrivateKeyPath
+      peerPrivateKeySecret
+      peerPublicKeyPath
+      ;
 
-    peerPresharedKeyFile = peerA: peerB: let
-      inherit (sortedPeers peerA peerB) peer1 peer2;
-    in
-      ../secrets/wireguard + "/${wgName}/psks/${peer1}-${peer2}.age";
-
-    peerPresharedKeySecret = peerA: peerB: let
-      inherit (sortedPeers peerA peerB) peer1 peer2;
-    in "wireguard-${wgName}-psks-${peer1}-${peer2}";
-
-    # All peers that are other nodes
-    nodesWithThisNetwork = filter (n: builtins.hasAttr wgName nodes.${n}.config.extra.wireguard.networks) (attrNames nodes);
-    nodePeers = genAttrs (filter (n: n != nodeName) nodesWithThisNetwork) (n: nodes.${n}.config.extra.wireguard.networks.${wgName}.address);
-    # All peers that are defined as externalPeers on any node. Also prepends "external-" to their name.
-    externalPeers = foldl' recursiveUpdate {} (
-      map (n: mapAttrs' (extPeerName: nameValuePair "external-${extPeerName}") nodes.${n}.config.extra.wireguard.networks.${wgName}.externalPeers)
-      nodesWithThisNetwork
-    );
-
-    peers = nodePeers // externalPeers;
-
-    peerDefinition = peerName: peerAllowedIPs: {
-      wireguardPeerConfig =
-        {
-          PublicKey = peerPublicKey wgName peerName;
-          PresharedKeyFile = config.rekey.secrets.${peerPresharedKeySecret wgName nodeName peerName}.path;
-          AllowedIPs = peerAllowedIPs;
-        }
-        // optional wg.listen {
-          PersistentKeepalive = 25;
-        };
-    };
+    otherPeers = filterAttrs (n: _: n != nodeName) (allPeers nodes);
   in {
-    inherit nodesWithThisNetwork wgName;
-
     secrets =
-      foldl' mergeAttrs {
-        ${peerPrivateKeySecret nodeName}.file = peerPrivateKeyFile nodeName;
-      } (map (peerName: {
-        ${peerPresharedKeySecret nodeName peerName}.file = peerPresharedKeyFile nodeName peerName;
-      }) (attrNames peers));
+      concatAttrs (map (other: {
+        ${peerPresharedKeySecret nodeName other}.file = peerPresharedKeyPath nodeName other;
+      }) (attrNames otherPeers))
+      // {
+        ${peerPrivateKeySecret nodeName}.file = peerPrivateKeyPath nodeName;
+      };
 
     netdevs."${wg.priority}-${wgName}" = {
       netdevConfig = {
@@ -100,11 +62,26 @@
         Name = "${wgName}";
         Description = "Wireguard network ${wgName}";
       };
-      wireguardConfig = {
-        PrivateKeyFile = config.rekey.secrets.${peerPrivateKeySecret nodeName}.path;
-        ListenPort = wg.listenPort;
-      };
-      wireguardPeers = mapAttrsToList peerDefinition peers;
+      wireguardConfig =
+        {
+          PrivateKeyFile = config.rekey.secrets.${peerPrivateKeySecret nodeName}.path;
+        }
+        // optionalAttrs wg.server.enable {
+          ListenPort = wg.server.port;
+        };
+      wireguardPeers =
+        mapAttrsToList (peerName: peerAllowedIPs: {
+          wireguardPeerConfig =
+            {
+              PublicKey = builtins.readFile (peerPublicKeyPath peerName);
+              PresharedKeyFile = config.rekey.secrets.${peerPresharedKeySecret nodeName peerName}.path;
+              AllowedIPs = peerAllowedIPs;
+            }
+            // optionalAttrs wg.server.enable {
+              PersistentKeepalive = 25;
+            };
+        })
+        otherPeers;
     };
 
     networks."${wg.priority}-${wgName}" = {
@@ -113,95 +90,88 @@
     };
   };
 in {
-  options = {
-    extra.wireguard.networks = mkOption {
-      default = {};
-      description = "Configures wireguard networks via systemd-networkd.";
-      type = types.attrsOf (types.submodule {
-        options = {
-          address = mkOption {
-            type = types.listOf types.str;
-            description = mdDoc ''
-              The addresses to configure for this interface. Will automatically be added
-              as this peer's allowed addresses to all other peers.
-            '';
-          };
+  options.extra.wireguard = mkOption {
+    default = {};
+    description = "Configures wireguard networks via systemd-networkd.";
+    type = types.attrsOf (types.submodule {
+      options = {
+        server = {
+          enable = mkEnableOption (mdDoc "wireguard server");
 
-          listen = mkOption {
-            type = types.bool;
-            default = false;
-            description = mdDoc ''
-              Enables listening for incoming wireguard connections.
-              This also causes all other peers to include this as an endpoint in their configuration.
-            '';
-          };
-
-          listenPort = mkOption {
+          port = mkOption {
             default = 51820;
-            type = types.int;
+            type = types.port;
             description = mdDoc "The port to listen on, if {option}`listen` is `true`.";
           };
 
-          priority = mkOption {
-            default = "20";
-            type = types.str;
-            description = mdDoc "The order priority used when creating systemd netdev and network files.";
-          };
-
           openFirewall = mkOption {
             default = false;
             type = types.bool;
             description = mdDoc "Whether to open the firewall for the specified `listenPort`, if {option}`listen` is `true`.";
           };
-
-          externalPeers = mkOption {
-            type = types.attrsOf (types.listOf types.str);
-            default = {};
-            example = {my-android-phone = ["10.0.0.97/32"];};
-            description = mdDoc ''
-              Allows defining extra set of external peers that should be added to the configuration.
-              For each external peers you can define one or multiple allowed ips.
-            '';
-          };
         };
-      });
-    };
+
+        priority = mkOption {
+          default = "20";
+          type = types.str;
+          description = mdDoc "The order priority used when creating systemd netdev and network files.";
+        };
+
+        address = mkOption {
+          type = types.listOf types.str;
+          description = mdDoc ''
+            The addresses to configure for this interface. Will automatically be added
+            as this peer's allowed addresses to all other peers.
+          '';
+        };
+
+        externalPeers = mkOption {
+          type = types.attrsOf (types.listOf types.str);
+          default = {};
+          example = {my-android-phone = ["10.0.0.97/32"];};
+          description = mdDoc ''
+            Allows defining extra set of external peers that should be added to the configuration.
+            For each external peers you can define one or multiple allowed ips.
+          '';
+        };
+      };
+    });
   };
 
-  config = mkIf (cfg.networks != {}) (let
-    networkCfgs = mapAttrsToList configForNetwork cfg.networks;
-    collectAttrs = x: foldl' mergeAttrs {} (map (y: y.${x}) networkCfgs);
+  config = mkIf (cfg != {}) (let
+    networkCfgs = mapAttrsToList configForNetwork cfg;
+    collectAllNetworkAttrs = x: concatAttrs (map (y: y.${x}) networkCfgs);
   in {
-    assertions =
-      concatMap (netCfg: let
-        inherit (netCfg) wgName;
-        externalPeers = concatMap (n: attrNames nodes.${n}.config.extra.wireguard.networks.${wgName}.externalPeers) netCfg.nodesWithThisNetwork;
-        duplicatePeers = duplicates externalPeers;
-        usedAddresses =
-          concatMap (n: nodes.${n}.config.extra.wireguard.networks.${wgName}.address) netCfg.nodesWithThisNetwork
-          ++ flatten (concatMap (n: attrValues nodes.${n}.config.extra.wireguard.networks.${wgName}.externalPeers) netCfg.nodesWithThisNetwork);
-        duplicateAddrs = duplicates (map (x: head (splitString "/" x)) usedAddresses);
-      in [
-        {
-          assertion = any (n: nodes.${n}.config.extra.wireguard.networks.${wgName}.listen) netCfg.nodesWithThisNetwork;
-          message = "Wireguard network '${wgName}': At least one node must be listening.";
-        }
-        {
-          assertion = duplicatePeers == [];
-          message = "Wireguard network '${wgName}': Multiple definitions for external peer(s):${concatMapStrings (x: " '${x}'") duplicatePeers}";
-        }
-        {
-          assertion = duplicateAddrs == [];
-          message = "Wireguard network '${wgName}': Addresses used multiple times: ${concatStringsSep ", " duplicateAddrs}";
-        }
-      ])
-      networkCfgs;
+    assertions = concatMap (wgName: let
+      inherit
+        (extraLib.wireguard wgName)
+        externalPeerNamesRaw
+        usedAddresses
+        associatedNodes
+        ;
 
-    networking.firewall.allowedUDPPorts = mkIf (cfg.listen && cfg.openFirewall) [cfg.listenPort];
-    rekey.secrets = collectAttrs "secrets";
+      duplicatePeers = duplicates (externalPeerNamesRaw nodes);
+      duplicateAddrs = duplicates (map (x: head (splitString "/" x)) (usedAddresses nodes));
+    in [
+      {
+        assertion = any (n: nodes.${n}.config.extra.wireguard.${wgName}.server.enable) (associatedNodes nodes);
+        message = "Wireguard network '${wgName}': At least one node must be a server.";
+      }
+      {
+        assertion = duplicatePeers == [];
+        message = "Wireguard network '${wgName}': Multiple definitions for external peer(s):${concatMapStrings (x: " '${x}'") duplicatePeers}";
+      }
+      {
+        assertion = duplicateAddrs == [];
+        message = "Wireguard network '${wgName}': Addresses used multiple times: ${concatStringsSep ", " duplicateAddrs}";
+      }
+    ]) (attrNames cfg);
+
+    networking.firewall.allowedUDPPorts = mkIf (cfg.server.enable && cfg.server.openFirewall) [cfg.server.port];
+    rekey.secrets = collectAllNetworkAttrs "secrets";
     systemd.network = {
-      netdevs = collectAttrs "netdevs";
-      networks = collectAttrs "networks";
+      netdevs = collectAllNetworkAttrs "netdevs";
+      networks = collectAllNetworkAttrs "networks";
     };
   });
 }
diff --git a/nix/apps/generate-wireguard-keys.nix b/nix/apps/generate-wireguard-keys.nix
index 8342cc1..5efdeb8 100644
--- a/nix/apps/generate-wireguard-keys.nix
+++ b/nix/apps/generate-wireguard-keys.nix
@@ -2,7 +2,7 @@
   self,
   pkgs,
   ...
-}: let
+} @ inputs: let
   inherit
     (pkgs.lib)
     attrNames
@@ -11,10 +11,12 @@
     concatStringsSep
     escapeShellArg
     filter
+    removeSuffix
     substring
     unique
     ;
 
+  extraLib = import ../lib.nix inputs;
   isAbsolutePath = x: substring 0 1 x == "/";
   masterIdentityArgs = concatMapStrings (x: ''-i ${escapeShellArg x} '') self.secrets.masterIdentities;
   extraEncryptionPubkeys =
@@ -26,57 +28,55 @@
     )
     self.secrets.extraEncryptionPubkeys;
 
-  sortedPeers = peerA: peerB:
-    if peerA < peerB
-    then {
-      peer1 = peerA;
-      peer2 = peerB;
-    }
-    else {
-      peer1 = peerB;
-      peer2 = peerA;
-    };
-
   nodeNames = attrNames self.nodes;
-  nodesWithNet = wgName: filter (n: builtins.hasAttr wgName self.nodes.${n}.config.extra.wireguard.networks) nodeNames;
-  wireguardNetworks = unique (concatMap (n: attrNames self.nodes.${n}.config.extra.wireguard.networks) nodeNames);
-  externalPeersForNet = wgName: concatMap (n: attrNames self.nodes.${n}.config.extra.wireguard.networks.${wgName}.externalPeers) (nodesWithNet wgName);
+  wireguardNetworks = unique (concatMap (n: attrNames self.nodes.${n}.config.extra.wireguard) nodeNames);
 
-  externalPeers = wgName: concatMap (n: attrNames self.nodes.${n}.config.extra.wireguard.networks.${wgName}.externalPeers) (nodesWithNet wgName);
-  peers = wgName: nodesWithNet wgName ++ externalPeers wgName;
+  generateNetworkKeys = wgName: let
+    inherit
+      (extraLib.wireguard wgName)
+      allPeers
+      associatedNodes
+      peerPresharedKeyFile
+      peerPrivateKeyFile
+      peerPublicKeyFile
+      ;
 
-  peerKeyBasename = wgName: peerName: "./secrets/wireguard/${wgName}/keys/${peerName}";
-  generatePeerKeys = wgName: peerName: let
-    keyBasename = peerKeyBasename wgName peerName;
-    privkeyFile = escapeShellArg "${keyBasename}.age";
-    pubkeyFile = escapeShellArg "${keyBasename}.pub";
-  in ''
-    if [[ ! -e ${privkeyFile} ]] || [[ ! -e ${pubkeyFile} ]]; then
-      mkdir -p $(dirname ${privkeyFile})
-      echo "Generating "${escapeShellArg keyBasename}".{age,pub}"
-      privkey=$(${pkgs.wireguard-tools}/bin/wg genkey)
-      echo "$privkey" | ${pkgs.wireguard-tools}/bin/wg pubkey > ${pubkeyFile}
-      ${pkgs.rage}/bin/rage -e ${masterIdentityArgs} ${extraEncryptionPubkeys} <<< "$privkey" > ${pubkeyFile} \
-        || { echo "error: Failed to encrypt wireguard private key for peer ${peerName} on network ${wgName}!" >&2; exit 1; }
-    fi
-  '';
+    nodesWithNet = associatedNodes self.nodes;
+    peers = attrNames (allPeers self.nodes);
 
-  generatePeerPsks = wgName: nodePeerName:
-    concatStringsSep "\n" (map (peerName: let
-      inherit (sortedPeers nodePeerName peerName) peer1 peer2;
-      pskFile = "./secrets/wireguard/${wgName}/psks/${peer1}-${peer2}.age";
+    generatePeerKeys = peerName: let
+      keyBasename = escapeShellArg ("./" + removeSuffix ".pub" (peerPublicKeyFile peerName));
+      pubkeyFile = escapeShellArg ("./" + peerPublicKeyFile peerName);
+      privkeyFile = escapeShellArg ("./" + peerPrivateKeyFile peerName);
     in ''
-      if [[ ! -e ${pskFile} ]]; then
-        mkdir -p $(dirname ${pskFile})
-        echo "Generating "${pskFile}""
-        psk=$(${pkgs.wireguard-tools}/bin/wg genpsk)
-        ${pkgs.rage}/bin/rage -e ${masterIdentityArgs} ${extraEncryptionPubkeys} <<< "$psk" > ${pskFile} \
-          || { echo "error: Failed to encrypt wireguard psk for peers ${peer1} and ${peer2} on network ${wgName}!" >&2; exit 1; }
+      if [[ ! -e ${privkeyFile} ]] || [[ ! -e ${pubkeyFile} ]]; then
+        mkdir -p $(dirname ${privkeyFile})
+        echo "Generating "${keyBasename}".{age,pub}"
+        privkey=$(${pkgs.wireguard-tools}/bin/wg genkey)
+        echo "$privkey" | ${pkgs.wireguard-tools}/bin/wg pubkey > ${pubkeyFile}
+        ${pkgs.rage}/bin/rage -e ${masterIdentityArgs} ${extraEncryptionPubkeys} <<< "$privkey" > ${privkeyFile} \
+          || { echo "error: Failed to encrypt wireguard private key for peer ${peerName} on network ${wgName}!" >&2; exit 1; }
       fi
-    '') (filter (x: x != nodePeerName) (peers wgName)));
+    '';
+
+    generatePeerPsks = nodePeerName:
+      map (peerName: let
+        pskFile = escapeShellArg ("./" + peerPresharedKeyFile nodePeerName peerName);
+      in ''
+        if [[ ! -e ${pskFile} ]]; then
+          mkdir -p $(dirname ${pskFile})
+          echo "Generating "${pskFile}""
+          psk=$(${pkgs.wireguard-tools}/bin/wg genpsk)
+          ${pkgs.rage}/bin/rage -e ${masterIdentityArgs} ${extraEncryptionPubkeys} <<< "$psk" > ${pskFile} \
+            || { echo "error: Failed to encrypt wireguard psk for peers ${nodePeerName} and ${peerName} on network ${wgName}!" >&2; exit 1; }
+        fi
+      '') (filter (x: x != nodePeerName) peers);
+  in
+    ["echo ==== ${wgName} ===="]
+    ++ map generatePeerKeys peers
+    ++ concatMap generatePeerPsks nodesWithNet;
 in
   pkgs.writeShellScript "generate-wireguard-keys" ''
     set -euo pipefail
-    ${concatStringsSep "\n" (concatMap (wgName: map (generatePeerKeys wgName) (peers wgName)) wireguardNetworks)}
-    ${concatStringsSep "\n" (concatMap (wgName: map (generatePeerPsks wgName) (nodesWithNet wgName)) wireguardNetworks)}
+    ${concatStringsSep "\n" (concatMap generateNetworkKeys wireguardNetworks)}
   ''
diff --git a/nix/apps/show-wireguard-qr.nix b/nix/apps/show-wireguard-qr.nix
index 756bbb9..0a5da1f 100644
--- a/nix/apps/show-wireguard-qr.nix
+++ b/nix/apps/show-wireguard-qr.nix
@@ -2,7 +2,7 @@
   self,
   pkgs,
   ...
-}: let
+} @ inputs: let
   inherit
     (pkgs.lib)
     attrNames
@@ -13,14 +13,18 @@
     unique
     ;
 
+  extraLib = import ../lib.nix inputs;
+
   nodeNames = attrNames self.nodes;
-  nodesWithNet = net: filter (n: builtins.hasAttr net self.nodes.${n}.config.extra.wireguard.networks) nodeNames;
-  wireguardNetworks = unique (concatMap (n: attrNames self.nodes.${n}.config.extra.wireguard.networks) nodeNames);
-  externalPeersForNet = net: concatMap (n: attrNames self.nodes.${n}.config.extra.wireguard.networks.${net}.externalPeers) (nodesWithNet net);
-  externalPeers = concatMap (net: map (peer: {inherit net peer;}) (externalPeersForNet net)) wireguardNetworks;
+  wireguardNetworks = unique (concatMap (n: attrNames self.nodes.${n}.config.extra.wireguard) nodeNames);
+
+  externalPeersForNet = wgName:
+    map (peer: {inherit wgName peer;})
+    (attrNames ((extraLib.wireguard wgName).externalPeers self.nodes));
+  allExternalPeers = concatMap externalPeersForNet wireguardNetworks;
 in
   # TODO generate "classic" config and run qrencode
   pkgs.writeShellScript "show-wireguard-qr" ''
     set -euo pipefail
-    echo ${escapeShellArg (concatStringsSep "\n" (map (x: "${x.net}.${x.peer}") externalPeers))} | fzf
+    echo ${escapeShellArg (concatStringsSep "\n" (map (x: "${x.wgName}.${x.peer}") allExternalPeers))} | ${pkgs.fzf}/bin/fzf
   ''
diff --git a/nix/lib.nix b/nix/lib.nix
index 20bea90..fa51204 100644
--- a/nix/lib.nix
+++ b/nix/lib.nix
@@ -1,8 +1,16 @@
 {nixpkgs, ...}: let
   inherit
     (nixpkgs.lib)
+    attrNames
+    attrValues
+    concatMap
     filter
+    flatten
     foldl'
+    genAttrs
+    mapAttrs'
+    mergeAttrs
+    nameValuePair
     unique
     ;
 in rec {
@@ -20,4 +28,57 @@ in rec {
     occurrences = countOccurrences xs;
   in
     unique (filter (x: occurrences.${x} > 1) xs);
+
+  # Concatenates all given attrsets as if calling a // b in order.
+  concatAttrs = foldl' mergeAttrs {};
+
+  # Wireguard related functions that are reused in several files of this flake
+  wireguard = wgName: rec {
+    _sortedPeers = peerA: peerB:
+      if peerA < peerB
+      then {
+        peer1 = peerA;
+        peer2 = peerB;
+      }
+      else {
+        peer1 = peerB;
+        peer2 = peerA;
+      };
+
+    peerPublicKeyFile = peerName: "secrets/wireguard/${wgName}/keys/${peerName}.pub";
+    peerPublicKeyPath = peerName: "${../.}/" + peerPublicKeyFile peerName;
+
+    peerPrivateKeyFile = peerName: "secrets/wireguard/${wgName}/keys/${peerName}.age";
+    peerPrivateKeyPath = peerName: "${../.}/" + peerPrivateKeyFile peerName;
+    peerPrivateKeySecret = peerName: "wireguard-${wgName}-priv-${peerName}";
+
+    peerPresharedKeyFile = peerA: peerB: let
+      inherit (_sortedPeers peerA peerB) peer1 peer2;
+    in "secrets/wireguard/${wgName}/psks/${peer1}+${peer2}.age";
+    peerPresharedKeyPath = peerA: peerB: "${../.}/" + peerPresharedKeyFile peerA peerB;
+    peerPresharedKeySecret = peerA: peerB: let
+      inherit (_sortedPeers peerA peerB) peer1 peer2;
+    in "wireguard-${wgName}-psks-${peer1}+${peer2}";
+
+    # All nodes that are part of this network
+    associatedNodes = nodes: filter (n: builtins.hasAttr wgName nodes.${n}.config.extra.wireguard) (attrNames nodes);
+    nodePeers = nodes: genAttrs (associatedNodes nodes) (n: nodes.${n}.config.extra.wireguard.${wgName}.address);
+    # All peers that are defined as externalPeers on any node.
+    # Prepends "external-" to their name.
+    externalPeers = nodes:
+      concatAttrs (
+        map (n: mapAttrs' (extPeerName: nameValuePair "external-${extPeerName}") nodes.${n}.config.extra.wireguard.${wgName}.externalPeers)
+        (associatedNodes nodes)
+      );
+    # Concatenation of all external peer names names without any transformations.
+    externalPeerNamesRaw = nodes: concatMap (n: attrNames nodes.${n}.config.extra.wireguard.${wgName}.externalPeers) (associatedNodes nodes);
+    # A list of all occurring addresses.
+    usedAddresses = nodes: let
+      nodesWithNet = associatedNodes nodes;
+    in
+      concatMap (n: nodes.${n}.config.extra.wireguard.${wgName}.address) nodesWithNet
+      ++ flatten (concatMap (n: attrValues nodes.${n}.config.extra.wireguard.${wgName}.externalPeers) nodesWithNet);
+
+    allPeers = nodes: nodePeers nodes // externalPeers nodes;
+  };
 }