feat(gopass): load SSH keys from gopass for git platforms

- Add security.gopass.ssh-agent.enable option
- Create gopass-ssh-load systemd oneshot service
- Remove identityFile and placeholder files from SSH git host configs
- Enable ssh-agent for the user

3 files changed, 60 insertions, 34 deletions

diff --git a/modules/security/gopass/default.nix b/modules/security/gopass/default.nix
index 19191ff..a121022 100644
--- a/modules/security/gopass/default.nix
+++ b/modules/security/gopass/default.nix
@@ -8,15 +8,16 @@
 {
   options.security.gopass = {
     enable = lib.mkEnableOption "Enables gopass.";
-
     package = lib.mkOption {
       type = lib.types.package;
       default = pkgs.gopass.override { passAlias = true; };
       defaultText = lib.literalExpression "pkgs.gopass.override { passAlias = true; }";
       description = "The gopass package to use.";
     };
+    ssh-agent = {
+      enable = lib.mkEnableOption "gopass-backed SSH keys for git";
+    };
   };
-
   config = lib.mkIf config.security.gopass.enable {
     programs.password-store = {
       enable = true;
@@ -25,5 +26,55 @@
         PASSWORD_STORE_DIR = "${config.home.homeDirectory}/.local/share/pass";
       };
     };
+    systemd.user.services.gopass-ssh-load = lib.mkIf config.security.gopass.ssh-agent.enable {
+      Unit = {
+        Description = "Load SSH keys from gopass into SSH agent for git";
+        After = [
+          "gpg-agent.socket"
+          "graphical-session.target"
+        ];
+        Requires = [
+          "gpg-agent.socket"
+        ];
+        PartOf = [
+          "graphical-session.target"
+        ];
+      };
+      Service = {
+        Type = "oneshot";
+        ExecStart = "${pkgs.writeShellScript "gopass-ssh-load" ''
+          export SSH_AUTH_SOCK="$(${pkgs.gnupg}/bin/gpgconf --list-dirs agent-ssh-socket)"
+
+          if [ -z "$SSH_AUTH_SOCK" ] || [ ! -S "$SSH_AUTH_SOCK" ]; then
+            exit 1
+          fi
+
+          for key in github gitlab bitbucket codeberg sourcehut; do
+            if ${config.security.gopass.package}/bin/gopass cat "ssh/$key" > /dev/null 2>&1; then
+              tmpdir=$(mktemp -d)
+              keyfile="$tmpdir/key"
+              ${config.security.gopass.package}/bin/gopass cat "ssh/$key" > "$keyfile" 2>/dev/null
+              chmod 600 "$keyfile"
+              if ! ${pkgs.openssh}/bin/ssh-add "$keyfile" 2>/dev/null; then
+                passphrase=$(${config.security.gopass.package}/bin/gopass cat "ssh/$key/passphrase" 2>/dev/null)
+                if [ -n "$passphrase" ]; then
+                  tmpcopy=$(mktemp)
+                  cp "$keyfile" "$tmpcopy"
+                  chmod 600 "$tmpcopy"
+                  if ${pkgs.openssh}/bin/ssh-keygen -p -P "$passphrase" -N "" -f "$tmpcopy" 2>/dev/null; then
+                    ${pkgs.openssh}/bin/ssh-add "$tmpcopy" 2>/dev/null
+                  fi
+                  rm -f "$tmpcopy"
+                fi
+              fi
+              rm -rf "$tmpdir"
+            fi
+          done
+        ''}";
+      };
+      Install = {
+        WantedBy = [ "graphical-session.target" ];
+      };
+    };
   };
 }
diff --git a/modules/security/ssh/git.nix b/modules/security/ssh/git.nix
index 88bd713..23b52ab 100644
--- a/modules/security/ssh/git.nix
+++ b/modules/security/ssh/git.nix
@@ -2,48 +2,22 @@
 { config, lib, ... }:
 let
   hosts = [
-    {
-      domain = "github.com";
-      identityName = "github";
-    }
-    {
-      domain = "gitlab.com";
-      identityName = "gitlab";
-    }
-    {
-      domain = "bitbucket.org";
-      identityName = "bitbucket";
-    }
-    {
-      domain = "codeberg.org";
-      identityName = "codeberg";
-    }
-    {
-      domain = "git.sr.ht";
-      identityName = "sourcehut";
-    }
+    "github.com"
+    "gitlab.com"
+    "bitbucket.org"
+    "codeberg.org"
+    "git.sr.ht"
   ];
 
   mkGitHost =
-    { domain, identityName }:
+    domain:
     lib.nameValuePair domain {
       hostname = domain;
       user = "git";
-      identityFile = "${config.home.homeDirectory}/.local/share/ssh/git/${identityName}";
-    };
-
-  mkKeyFile =
-    { identityName, ... }:
-    lib.nameValuePair identityName {
-      enable = true;
-      text = "";
-      force = false;
     };
 in
 {
   config = lib.mkIf (config.security.ssh.enable && config.development.git.useSSH) {
-    home.file = builtins.listToAttrs (map mkKeyFile hosts);
-
     programs.ssh.settings = builtins.listToAttrs (map mkGitHost hosts);
   };
 }
diff --git a/users/arpit.nix b/users/arpit.nix
index ab89546..d2803d6 100644
--- a/users/arpit.nix
+++ b/users/arpit.nix
@@ -57,6 +57,7 @@
   # Security
   security.enteauth.enable = true;
   security.gopass.enable = true;
+  security.gopass.ssh-agent.enable = true;
   security.gpg.enable = true;
   security.openvpn.enable = true;
   security.ssh.enable = true;