go/nix: teach bnix how to talk to a remote store over SSH

go/nix/bnix/bnix.go

@@ -4,18 +4,25 @@ import (
 	"context"
 	"flag"
 	"fmt"
+	"io"
 	"log"
+	"net/url"
 	"os"
 
+	"golang.org/x/crypto/ssh"
 	"hg.lukegb.com/lukegb/depot/go/nix/nixdrv"
 	"hg.lukegb.com/lukegb/depot/go/nix/nixstore"
 )
 
+var (
+	remoteFlag = flag.String("remote", "unix://", "Remote.")
+)
+
 func ensure(ctx context.Context, d *nixstore.Daemon, at *nixstore.ActivityTracker, path string) error {
 	return d.EnsurePath(at, path)
 }
 
-var rs nixdrv.LocalFSResolver
+var rs nixdrv.Resolver
 
 func loadDerivation(ctx context.Context, path string) (*nixdrv.Derivation, error) {
 	return rs.LoadDerivation(path)
@@ -40,6 +47,115 @@ func buildDerivation(ctx context.Context, d *nixstore.Daemon, at *nixstore.Activ
 	return nil
 }
 
+func connectTo(ctx context.Context, remote string) (*nixstore.Daemon, nixdrv.Resolver, error) {
+	u, err := url.Parse(remote)
+	if err != nil {
+		return nil, nil, fmt.Errorf("parsing remote %q as URL: %w", remote, err)
+	}
+
+	switch u.Scheme {
+	case "unix":
+		if u.Path == "" {
+			u.Path = nixstore.DaemonSock
+		}
+		d, err := nixstore.OpenDaemon(u.Path)
+		if err != nil {
+			return nil, nil, err
+		}
+		return d, nixdrv.LocalFSResolver{}, nil
+	case "ssh-ng":
+		// Construct a ClientConfig from the URL.
+		cfg := &ssh.ClientConfig{}
+		if u.Query().Has("privkey") {
+			var keys []ssh.Signer
+			for _, privkeyPath := range u.Query()["privkey"] {
+				privkeyF, err := os.Open(privkeyPath)
+				if err != nil {
+					return nil, nil, fmt.Errorf("opening privkey %q: %w", privkeyPath, err)
+				}
+				defer privkeyF.Close()
+				privkeyB, err := io.ReadAll(privkeyF)
+				if err != nil {
+					return nil, nil, fmt.Errorf("reading privkey %q: %w", privkeyPath, err)
+				}
+
+				privkey, err := ssh.ParsePrivateKey(privkeyB)
+				if err != nil {
+					return nil, nil, fmt.Errorf("parsing privkey %q: %w", privkeyPath, err)
+				}
+				keys = append(keys, privkey)
+			}
+			cfg.Auth = append(cfg.Auth, ssh.PublicKeys(keys...))
+		}
+		if u.User != nil {
+			cfg.User = u.User.Username()
+			if pw, ok := u.User.Password(); ok {
+				cfg.Auth = append(cfg.Auth, ssh.Password(pw))
+			}
+		}
+		switch {
+		case u.Query().Has("host-key"):
+			hkStr := u.Query().Get("host-key")
+			_, _, hk, _, _, err := ssh.ParseKnownHosts(append([]byte("x "), []byte(hkStr)...))
+			if err != nil {
+				return nil, nil, fmt.Errorf("parsing host-key %q: %w", hkStr, err)
+			}
+			cfg.HostKeyCallback = ssh.FixedHostKey(hk)
+		case u.Query().Has("insecure-allow-any-ssh-host-key"):
+			cfg.HostKeyCallback = ssh.InsecureIgnoreHostKey()
+		default:
+			return nil, nil, fmt.Errorf("some SSH host key configuration is required (?host-key=; ?insecure-allow-any-ssh-host-key)")
+		}
+
+		// Work out other misc parameters.
+		// ...remote command.
+		remoteCmd := "nix-daemon --stdio"
+		if u.Query().Has("remote-cmd") {
+			remoteCmd = u.Query().Get("remote-cmd")
+		}
+
+		// Work out the host:port to connect to.
+		remote := u.Hostname()
+		if portStr := u.Port(); portStr != "" {
+			remote = remote + ":" + portStr
+		} else {
+			remote = remote + ":22"
+		}
+
+		conn, err := ssh.Dial("tcp", remote, cfg)
+		if err != nil {
+			return nil, nil, fmt.Errorf("dialing %v via SSH: %w", remote, err)
+		}
+		sess, err := conn.NewSession()
+		if err != nil {
+			conn.Close()
+			return nil, nil, fmt.Errorf("opening SSH session to %v: %w", remote, err)
+		}
+		stdin, err := sess.StdinPipe()
+		if err != nil {
+			conn.Close()
+			return nil, nil, fmt.Errorf("opening stdin pipe: %w", err)
+		}
+		stdout, err := sess.StdoutPipe()
+		if err != nil {
+			conn.Close()
+			return nil, nil, fmt.Errorf("opening stdout pipe: %w", err)
+		}
+		if err := sess.Start(remoteCmd); err != nil {
+			conn.Close()
+			return nil, nil, fmt.Errorf("starting %q: %w", remoteCmd, err)
+		}
+		d, err := nixstore.OpenDaemonWithIOs(stdout, stdin, conn)
+		if err != nil {
+			conn.Close()
+			return nil, nil, fmt.Errorf("establishing connection to daemon: %w", err)
+		}
+		return d, nixdrv.LocalFSResolver{}, nil // TODO: change from LocalFSResolver?
+	default:
+		return nil, nil, fmt.Errorf("unknown remote %q", remote)
+	}
+}
+
 func main() {
 	flag.Parse()
 
@@ -87,13 +203,14 @@ func main() {
 
 	at := nixstore.NewActivityTracker()
 
-	d, err := nixstore.OpenDaemon(nixstore.DaemonSock)
+	ctx := context.Background()
+	d, rss, err := connectTo(ctx, *remoteFlag)
 	if err != nil {
-		log.Fatalf("OpenDaemon: %v", err)
+		log.Fatalf("connectTo(%q): %v", *remoteFlag, err)
 	}
 	defer d.Close()
+	rs = rss
 
-	ctx := context.Background()
 	if err := cmd(ctx, d, at); err != nil {
 		log.Fatalf("%s: %s", flag.Arg(0), err)
 	}

go/nix/default.nix

@@ -5,6 +5,7 @@
 args:
 {
   nar = import ./nar args;
+  nixdrv = import ./nixdrv args;
   nixstore = import ./nixstore args;
   nixwire = import ./nixwire args;
   bcachegc = import ./bcachegc args;

go/nix/nixdrv/default.nix

@@ -0,0 +1,15 @@
+# SPDX-FileCopyrightText: 2023 Luke Granger-Brown <depot@lukegb.com>
+#
+# SPDX-License-Identifier: Apache-2.0
+
+{ depot, ... }:
+depot.third_party.buildGo.package {
+  name = "nixdrv";
+  path = "hg.lukegb.com/lukegb/depot/go/nix/nixdrv";
+  srcs = [
+    ./nixdrv.go
+    ./localfs.go
+  ];
+  deps = with depot; [
+  ];
+}

go/nix/nixstore/default.nix

@@ -7,6 +7,7 @@ depot.third_party.buildGo.package {
   name = "nixstore";
   path = "hg.lukegb.com/lukegb/depot/go/nix/nixstore";
   srcs = [
+    ./activities.go
     ./nixstore.go
     ./remotestore.go
     ./sqlitestore.go

go/nix/nixstore/remotestore.go

@@ -29,7 +29,7 @@ const (
 )
 
 type Daemon struct {
-	conn net.Conn
+	conn io.Closer
 	w    *nixwire.Serializer
 	r    *nixwire.Deserializer
 	mu   sync.Mutex
@@ -453,6 +453,15 @@ func OpenDaemon(path string) (*Daemon, error) {
 		return nil, fmt.Errorf("sending hello to %v: %w", path, err)
 	}
 
-	// /nix/var/nix/daemon-socket/socket
+	return d, nil
+}
+
+func OpenDaemonWithIOs(r io.Reader, w io.Writer, c io.Closer) (*Daemon, error) {
+	d := &Daemon{conn: c, w: &nixwire.Serializer{w}, r: &nixwire.Deserializer{r}}
+	if err := d.hello(); err != nil {
+		d.Close()
+		return nil, fmt.Errorf("sending hello: %w", err)
+	}
+
 	return d, nil
 }

go/nix/nixwire/default.nix

@@ -9,4 +9,7 @@ depot.third_party.buildGo.package {
   srcs = [
     ./nixwire.go
   ];
+  deps = with depot; [
+    go.nix.nixdrv
+  ];
 }