Server: add and support unix listener (UDS) (#18227)

Co-authored-by: shaj13 <[email protected]>

changelog/18227.txt

@@ -0,0 +1,3 @@
+```release-note:feature
+**Server UDS Listener**: Adding listener to Vault server to serve http request via unix domain socket
+```

command/server/listener.go

@@ -20,7 +20,8 @@ type ListenerFactory func(*configutil.Listener, io.Writer, cli.Ui) (net.Listener
 
 // BuiltinListeners is the list of built-in listener types.
 var BuiltinListeners = map[string]ListenerFactory{
-	"tcp": tcpListenerFactory,
+	"tcp":  tcpListenerFactory,
+	"unix": unixListenerFactory,
 }
 
 // NewListener creates a new listener of the given type with the given

command/server/listener_test.go

@@ -26,6 +26,9 @@ func testListenerImpl(t *testing.T, ln net.Listener, connFn testListenerConnFn,
 			tlsConn.Handshake()
 		}
 		serverCh <- server
+		if expectedAddr == "" {
+			return
+		}
 		addr, _, err := net.SplitHostPort(server.RemoteAddr().String())
 		if err != nil {
 			t.Error(err)

command/server/listener_unix.go

@@ -0,0 +1,36 @@
+package server
+
+import (
+	"io"
+	"net"
+
+	"github.com/hashicorp/go-secure-stdlib/reloadutil"
+	"github.com/hashicorp/vault/internalshared/configutil"
+	"github.com/hashicorp/vault/internalshared/listenerutil"
+	"github.com/mitchellh/cli"
+)
+
+func unixListenerFactory(l *configutil.Listener, _ io.Writer, ui cli.Ui) (net.Listener, map[string]string, reloadutil.ReloadFunc, error) {
+	addr := l.Address
+	if addr == "" {
+		addr = "/run/vault.sock"
+	}
+
+	var cfg *listenerutil.UnixSocketsConfig
+	if l.SocketMode != "" &&
+		l.SocketUser != "" &&
+		l.SocketGroup != "" {
+		cfg = &listenerutil.UnixSocketsConfig{
+			Mode:  l.SocketMode,
+			User:  l.SocketUser,
+			Group: l.SocketGroup,
+		}
+	}
+
+	ln, err := listenerutil.UnixSocketListener(addr, cfg)
+	if err != nil {
+		return nil, nil, nil, err
+	}
+
+	return ln, map[string]string{}, nil, nil
+}

command/server/listener_unix_test.go

@@ -0,0 +1,25 @@
+package server
+
+import (
+	"net"
+	"path/filepath"
+	"testing"
+
+	"github.com/hashicorp/vault/internalshared/configutil"
+	"github.com/mitchellh/cli"
+)
+
+func TestUnixListener(t *testing.T) {
+	ln, _, _, err := unixListenerFactory(&configutil.Listener{
+		Address: filepath.Join(t.TempDir(), "/vault.sock"),
+	}, nil, cli.NewMockUi())
+	if err != nil {
+		t.Fatalf("err: %s", err)
+	}
+
+	connFn := func(lnReal net.Listener) (net.Conn, error) {
+		return net.Dial("unix", ln.Addr().String())
+	}
+
+	testListenerImpl(t, ln, connFn, "", 0, "", false)
+}

website/content/docs/configuration/listener/index.mdx

@@ -9,6 +9,9 @@ description: |-
 # `listener` Stanza
 
 The `listener` stanza configures the addresses and ports on which Vault will
-respond to requests. At this time, there is only one listener - [TCP][tcp].
+respond to requests. At this time, there are two listeners: 
+- [TCP][tcp]
+- [Unix Domain Socket][unix]
 
 [tcp]: /docs/configuration/listener/tcp
+[unix]: /docs/configuration/listener/unix

website/content/docs/configuration/listener/unix.mdx

@@ -0,0 +1,69 @@
+---
+layout: docs
+page_title: Unix - Listeners - Configuration
+description: |-
+  The Unix listener configures Vault to listen on the specified Unix domain socket.
+---
+
+# `unix` Listener
+
+The Unix listener configures Vault to listen on the specified Unix domain socket.
+
+```hcl
+listener "unix" {
+  address = "/run/vault.sock"
+}
+```
+
+The `listener` stanza may be specified more than once to make Vault listen on
+multiple sockets.
+
+## `unix` Listener Parameters
+- `address` `(string: "/run/vault.sock", <required>)` – Specifies the address to bind the Unix socket.
+
+- `socket_mode` `(string: "", <optional>)` – Changes the access
+  permissions and the special mode flags of the Unix socket.
+
+- `socket_user` `(string: "", <optional>)` – Changes the user owner of the Unix socket.
+
+- `socket_group` `(string: "", <optional>)` – Changes the group owner of the Unix socket.
+
+
+## `unix` Listener Examples
+
+### Listening on Multiple Sockets
+
+This example shows Vault listening on a specified socket, as well as the default.
+
+```hcl
+listener "unix" {}
+
+listener "unix" {
+  address = "/var/run/vault.sock"
+}
+```
+
+### Listening on Multiple Interfaces
+
+This example shows Vault listening on TCP localhost, as well as Unix socket.
+
+```hcl
+listener "unix" {
+  address = "/var/run/vault.sock"
+}
+
+listener "tcp" {
+  address = "127.0.0.1:8200"
+}
+```
+
+### Configuring Permissions
+This example shows changing access permissions and ownership of the Unix socket.
+```hcl
+listener "unix" {
+  address = "/var/run/vault.sock"
+  socket_mode = "644"
+  socket_user = "1000"
+  socket_group = "1000"
+}
+```

website/data/docs-nav-data.json

@@ -214,6 +214,10 @@
           {
             "title": "TCP",
             "path": "configuration/listener/tcp"
+          },
+          {
+            "title": "Unix",
+            "path": "configuration/listener/unix"
           }
         ]
       },