cmd/tailscale/cli: Add CLI command to update certs on Synology devices.

Fixes #4674

Signed-off-by: Will Morrison <william.barr.morrison@gmail.com>

cmd/tailscale/cli/configure-synology-cert.go

@@ -0,0 +1,220 @@
+// Copyright (c) Tailscale Inc & AUTHORS
+// SPDX-License-Identifier: BSD-3-Clause
+
+package cli
+
+import (
+	"context"
+	"encoding/json"
+	"errors"
+	"flag"
+	"fmt"
+	"log"
+	"os"
+	"os/exec"
+	"path"
+	"runtime"
+	"strings"
+
+	"github.com/peterbourgon/ff/v3/ffcli"
+	"tailscale.com/hostinfo"
+	"tailscale.com/ipn"
+	"tailscale.com/version/distro"
+)
+
+var synologyConfigureCertCmd = &ffcli.Command{
+	Name:       "synology-cert",
+	Exec:       runConfigureSynologyCert,
+	ShortHelp:  "Configure Synology with a TLS certificate for your tailnet",
+	ShortUsage: "synology-cert [--domain <domain>]",
+	LongHelp: strings.TrimSpace(`
+This command is intended to run periodically as root on a Synology device to
+create or refresh the TLS certificate for the tailnet domain.
+
+See: https://tailscale.com/kb/1153/enabling-https
+`),
+	FlagSet: (func() *flag.FlagSet {
+		fs := newFlagSet("synology-cert")
+		fs.StringVar(&synologyConfigureCertArgs.domain, "domain", "", "Tailnet domain to create or refresh certificates for. Ignored if only one domain exists.")
+		return fs
+	})(),
+}
+
+var synologyConfigureCertArgs struct {
+	domain string
+}
+
+func runConfigureSynologyCert(ctx context.Context, args []string) error {
+	if len(args) > 0 {
+		return errors.New("unknown arguments")
+	}
+	if runtime.GOOS != "linux" || distro.Get() != distro.Synology {
+		return errors.New("only implemented on Synology")
+	}
+	if uid := os.Getuid(); uid != 0 {
+		return fmt.Errorf("must be run as root, not %q (%v)", os.Getenv("USER"), uid)
+	}
+	hi := hostinfo.New()
+	isDSM6 := strings.HasPrefix(hi.DistroVersion, "6.")
+	isDSM7 := strings.HasPrefix(hi.DistroVersion, "7.")
+	if !isDSM6 && !isDSM7 {
+		return fmt.Errorf("unsupported DSM version %q", hi.DistroVersion)
+	}
+
+	domain := synologyConfigureCertArgs.domain
+	if st, err := localClient.Status(ctx); err == nil {
+		if st.BackendState != ipn.Running.String() {
+			return fmt.Errorf("Tailscale is not running.")
+		} else if len(st.CertDomains) == 0 {
+			return fmt.Errorf("TLS certificate support is not enabled/configured for your tailnet.")
+		} else if len(st.CertDomains) == 1 {
+			if domain != "" && domain != st.CertDomains[0] {
+				log.Printf("Ignoring supplied domain %q, TLS certificate will be created for %q.\n", domain, st.CertDomains[0])
+			}
+			domain = st.CertDomains[0]
+		} else {
+			var found bool
+			for _, d := range st.CertDomains {
+				if d == domain {
+					found = true
+					break
+				}
+			}
+			if !found {
+				return fmt.Errorf("Domain %q was not one of the valid domain options: %q.", domain, st.CertDomains)
+			}
+		}
+	}
+
+	// Check for an existing certificate, and replace it if it already exists
+	var id string
+	certs, err := listCerts(ctx, synowebapiCommand{})
+	if err != nil {
+		return err
+	}
+	for _, c := range certs {
+		if c.Subject.CommonName == domain {
+			id = c.ID
+			break
+		}
+	}
+
+	certPEM, keyPEM, err := localClient.CertPair(ctx, domain)
+	if err != nil {
+		return err
+	}
+
+	// Certs have to be written to file for the upload command to work.
+	tmpDir, err := os.MkdirTemp("", "")
+	if err != nil {
+		return fmt.Errorf("can't create temp dir: %w", err)
+	}
+	defer os.RemoveAll(tmpDir)
+	keyFile := path.Join(tmpDir, "key.pem")
+	os.WriteFile(keyFile, keyPEM, 0600)
+	certFile := path.Join(tmpDir, "cert.pem")
+	os.WriteFile(certFile, certPEM, 0600)
+
+	if err := uploadCert(ctx, synowebapiCommand{}, certFile, keyFile, id); err != nil {
+		return err
+	}
+
+	return nil
+}
+
+type subject struct {
+	CommonName string `json:"common_name"`
+}
+
+type certificateInfo struct {
+	ID      string  `json:"id"`
+	Desc    string  `json:"desc"`
+	Subject subject `json:"subject"`
+}
+
+// listCerts fetches a list of the certificates that DSM knows about
+func listCerts(ctx context.Context, c synoAPICaller) ([]certificateInfo, error) {
+	rawData, err := c.Call(ctx, "SYNO.Core.Certificate.CRT", "list", nil)
+	if err != nil {
+		return nil, err
+	}
+
+	var payload struct {
+		Certificates []certificateInfo `json:"certificates"`
+	}
+	if err := json.Unmarshal(rawData, &payload); err != nil {
+		return nil, fmt.Errorf("decoding certificate list response payload: %w", err)
+	}
+
+	return payload.Certificates, nil
+}
+
+// uploadCert creates or replaces a certificate. If id is given, it will attempt to replace the certificate with that ID.
+func uploadCert(ctx context.Context, c synoAPICaller, certFile, keyFile string, id string) error {
+	params := map[string]string{
+		"key_tmp":  keyFile,
+		"cert_tmp": certFile,
+		"desc":     "Tailnet Certificate",
+	}
+	if id != "" {
+		params["id"] = id
+	}
+
+	rawData, err := c.Call(ctx, "SYNO.Core.Certificate", "import", params)
+	if err != nil {
+		return err
+	}
+
+	var payload struct {
+		NewID string `json:"id"`
+	}
+	if err := json.Unmarshal(rawData, &payload); err != nil {
+		return fmt.Errorf("decoding certificate upload response payload: %w", err)
+	}
+	log.Printf("Tailnet Certificate uploaded with ID %q.", payload.NewID)
+
+	return nil
+
+}
+
+type synoAPICaller interface {
+	Call(context.Context, string, string, map[string]string) (json.RawMessage, error)
+}
+
+type apiResponse struct {
+	Success bool            `json:"success"`
+	Error   *apiError       `json:"error,omitempty"`
+	Data    json.RawMessage `json:"data"`
+}
+
+type apiError struct {
+	Code   int64  `json:"code"`
+	Errors string `json:"errors"`
+}
+
+// synowebapiCommand implements synoAPICaller using the /usr/syno/bin/synowebapi binary. Must be run as root.
+type synowebapiCommand struct{}
+
+func (s synowebapiCommand) Call(ctx context.Context, api, method string, params map[string]string) (json.RawMessage, error) {
+	args := []string{"--exec", fmt.Sprintf("api=%s", api), fmt.Sprintf("method=%s", method)}
+
+	for k, v := range params {
+		args = append(args, fmt.Sprintf("%s=%q", k, v))
+	}
+
+	out, err := exec.CommandContext(ctx, "/usr/syno/bin/synowebapi", args...).Output()
+	if err != nil {
+		return nil, fmt.Errorf("calling %q method of %q API: %v, %s", method, api, err, out)
+	}
+
+	var payload apiResponse
+	if err := json.Unmarshal(out, &payload); err != nil {
+		return nil, fmt.Errorf("decoding response json from %q method of %q API: %w", method, api, err)
+	}
+
+	if payload.Error != nil {
+		return nil, fmt.Errorf("error response from %q method of %q API: %v", method, api, payload.Error)
+	}
+
+	return payload.Data, nil
+}

cmd/tailscale/cli/configure-synology-cert_test.go

@@ -0,0 +1,140 @@
+// Copyright (c) Tailscale Inc & AUTHORS
+// SPDX-License-Identifier: BSD-3-Clause
+
+package cli
+
+import (
+	"context"
+	"encoding/json"
+	"fmt"
+	"reflect"
+	"testing"
+)
+
+type fakeAPICaller struct {
+	Data  json.RawMessage
+	Error error
+}
+
+func (c fakeAPICaller) Call(_ context.Context, _, _ string, _ map[string]string) (json.RawMessage, error) {
+	return c.Data, c.Error
+}
+
+func Test_listCerts(t *testing.T) {
+	tests := []struct {
+		name    string
+		caller  synoAPICaller
+		want    []certificateInfo
+		wantErr bool
+	}{
+		{
+			name: "normal response",
+			caller: fakeAPICaller{
+				Data: json.RawMessage(`{
+"certificates" : [
+	{
+		"desc" : "Tailnet Certificate",
+		"id" : "cG2XBt",
+		"is_broken" : false,
+		"is_default" : false,
+		"issuer" : {
+			"common_name" : "R3",
+			"country" : "US",
+			"organization" : "Let's Encrypt"
+		},
+		"key_types" : "ECC",
+		"renewable" : false,
+		"services" : [
+			{
+			"display_name" : "DSM Desktop Service",
+			"display_name_i18n" : "common:web_desktop",
+			"isPkg" : false,
+			"multiple_cert" : true,
+			"owner" : "root",
+			"service" : "default",
+			"subscriber" : "system",
+			"user_setable" : true
+			}
+		],
+		"signature_algorithm" : "sha256WithRSAEncryption",
+		"subject" : {
+			"common_name" : "foo.tailscale.ts.net",
+			"sub_alt_name" : [ "foo.tailscale.ts.net" ]
+		},
+		"user_deletable" : true,
+		"valid_from" : "Sep 26 11:39:43 2023 GMT",
+		"valid_till" : "Dec 25 11:39:42 2023 GMT"
+	},
+	{
+		"desc" : "",
+		"id" : "sgmnpb",
+		"is_broken" : false,
+		"is_default" : false,
+		"issuer" : {
+			"city" : "Taipei",
+			"common_name" : "Synology Inc. CA",
+			"country" : "TW",
+			"organization" : "Synology Inc."
+		},
+		"key_types" : "",
+		"renewable" : false,
+		"self_signed_cacrt_info" : {
+			"issuer" : {
+			"city" : "Taipei",
+			"common_name" : "Synology Inc. CA",
+			"country" : "TW",
+			"organization" : "Synology Inc."
+			},
+			"subject" : {
+			"city" : "Taipei",
+			"common_name" : "Synology Inc. CA",
+			"country" : "TW",
+			"organization" : "Synology Inc."
+			}
+		},
+		"services" : [],
+		"signature_algorithm" : "sha256WithRSAEncryption",
+		"subject" : {
+			"city" : "Taipei",
+			"common_name" : "synology.com",
+			"country" : "TW",
+			"organization" : "Synology Inc.",
+			"sub_alt_name" : []
+		},
+		"user_deletable" : true,
+		"valid_from" : "May 27 00:23:19 2019 GMT",
+		"valid_till" : "Feb 11 00:23:19 2039 GMT"
+	}
+]
+}`),
+				Error: nil,
+			},
+			want: []certificateInfo{
+				{Desc: "Tailnet Certificate", ID: "cG2XBt", Subject: subject{CommonName: "foo.tailscale.ts.net"}},
+				{Desc: "", ID: "sgmnpb", Subject: subject{CommonName: "synology.com"}},
+			},
+		},
+		{
+			name:    "call error",
+			caller:  fakeAPICaller{nil, fmt.Errorf("caller failed")},
+			wantErr: true,
+		},
+		{
+			name:    "payload decode error",
+			caller:  fakeAPICaller{json.RawMessage("This isn't JSON!"), nil},
+			wantErr: true,
+		},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			got, err := listCerts(context.Background(), tt.caller)
+			if (err != nil) != tt.wantErr {
+				t.Errorf("listCerts() error = %v, wantErr %v", err, tt.wantErr)
+				return
+			}
+			if !reflect.DeepEqual(got, tt.want) {
+				t.Errorf("listCerts() = %v, want %v", got, tt.want)
+			}
+		})
+	}
+}

cmd/tailscale/cli/configure.go

@@ -33,6 +33,7 @@
 func configureSubcommands() (out []*ffcli.Command) {
 	if runtime.GOOS == "linux" && distro.Get() == distro.Synology {
 		out = append(out, synologyConfigureCmd)
+		out = append(out, synologyConfigureCertCmd)
 	}
 	return out
 }