262 lines
7.1 KiB
Go
262 lines
7.1 KiB
Go
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package main
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import (
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"bufio"
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"bytes"
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"context"
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"flag"
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"fmt"
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"io"
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"os"
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"os/exec"
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"path/filepath"
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"strings"
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"time"
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"github.com/coreos/go-systemd/v22/dbus"
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log "github.com/golang/glog"
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vapi "github.com/hashicorp/vault/api"
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"golang.org/x/crypto/ssh"
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)
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var (
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signSSHHostKeys = flag.Bool("sign_ssh_host_keys", true, "Sign SSH host keys with CA")
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sshHostKeyCAPath = flag.String("ssh_host_key_ca_path", "ssh-host", "Path that the SSH CA is mounted at")
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sshHostKeyRole = flag.String("ssh_host_key_role", hostname(), "Role to use for signing SSH host keys")
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sshHostKeyPrincipals = flag.String("ssh_host_key_principals", defaultPrincipals(hostname()), "Principals to use for SSH host key certificate")
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sshHostKeyExpiryThreshold = flag.Duration("ssh_host_key_expiry_threshold", 3*24*time.Hour, "Expiry threshold for SSH host key")
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sshHostKeyOutputDir = flag.String("ssh_host_key_output_dir", "/var/lib/secretsmgr/ssh", "Path to SSH host key output dir")
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sshd = flag.String("sshd", "sshd", "Path to sshd")
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)
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func hostname() string {
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name, err := os.Hostname()
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if err != nil {
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return ""
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}
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return name
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}
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func defaultPrincipals(hostname string) string {
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return fmt.Sprintf("%s.as205479.net,%s.int.as205479.net", hostname, hostname)
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}
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func sshHostKeyPaths(ctx context.Context) ([]string, error) {
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out, err := exec.CommandContext(ctx, *sshd, "-T").Output()
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if err != nil {
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return nil, err
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}
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scanner := bufio.NewScanner(bytes.NewReader(out))
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var keys []string
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const hostkeyPrefix = "hostkey "
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for scanner.Scan() {
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t := scanner.Text()
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if strings.HasPrefix(t, hostkeyPrefix) {
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keys = append(keys, fmt.Sprintf("%s.pub", strings.TrimPrefix(t, hostkeyPrefix)))
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}
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}
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if scanner.Err() != nil {
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return nil, scanner.Err()
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}
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return keys, nil
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}
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func readFile(p string) ([]byte, error) {
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f, err := os.Open(p)
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if err != nil {
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return nil, err
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}
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defer f.Close()
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return io.ReadAll(f)
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}
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func writeFile(p string, content []byte) error {
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f, err := os.Create(p)
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if err != nil {
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return err
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}
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if _, err := f.Write(content); err != nil {
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f.Close()
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return err
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}
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if err := f.Close(); err != nil {
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return err
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}
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return nil
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}
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func readSSHPublicKey(p string) (ssh.PublicKey, error) {
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bs, err := readFile(p)
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if err != nil {
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return nil, fmt.Errorf("reading public key from %v: %w", p, err)
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}
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out, _, _, _, err := ssh.ParseAuthorizedKey(bs)
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if err != nil {
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return nil, fmt.Errorf("parsing public key in %v: %w", p, err)
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}
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return out, nil
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}
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func shouldRenewSSHCert(certPath string, publicKey []byte, principals string) (bool, error) {
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certPK, err := readSSHPublicKey(certPath)
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if err != nil {
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return true, err
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}
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cert, ok := certPK.(*ssh.Certificate)
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if !ok {
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return true, fmt.Errorf("file at %v was not an SSH certificate (was a %T)", certPath, certPK)
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}
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pubKey, _, _, _, err := ssh.ParseAuthorizedKey(publicKey)
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if err != nil {
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return false, err
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}
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// Verify that this is the same key.
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if !bytes.Equal(pubKey.Marshal(), cert.Key.Marshal()) {
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return true, fmt.Errorf("certificate key and public key don't match")
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}
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// Verify the certificate isn't expiring too soon.
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unixNow := time.Now().Unix()
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expiryThreshold := uint64(unixNow + int64(sshHostKeyExpiryThreshold.Seconds()))
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certExpiryDate := time.Unix(int64(cert.ValidBefore), 0)
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log.Infof("certificate %v expires at %v (in %v)", certPath, certExpiryDate, certExpiryDate.Sub(time.Now()))
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if cert.ValidBefore != uint64(ssh.CertTimeInfinity) && cert.ValidBefore < expiryThreshold {
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return true, fmt.Errorf("certificate expires at %v, which is earlier than our threshold of %v", certExpiryDate, time.Unix(int64(expiryThreshold), 0))
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}
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hasPrincipals := map[string]bool{}
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for _, p := range cert.ValidPrincipals {
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hasPrincipals[p] = true
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}
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for _, wantP := range strings.Split(principals, ",") {
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if !hasPrincipals[wantP] {
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return true, fmt.Errorf("certificate missing principal %v (has principals %v; want principals %v)", wantP, cert.ValidPrincipals, principals)
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}
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}
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return false, nil
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}
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func reloadOrTryRestartServices(ctx context.Context, services []string) error {
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sd, err := dbus.NewSystemdConnection()
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if err != nil {
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return fmt.Errorf("failed to connect to systemd: %w", err)
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}
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defer sd.Close()
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var failedUnits []string
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for _, service := range services {
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_, err := sd.ReloadOrTryRestartUnit(service, "replace", nil)
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if err != nil {
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log.Errorf("unit %v failed to reload-or-try-restart: %v", service, err)
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failedUnits = append(failedUnits, service)
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}
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}
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if len(failedUnits) != 0 {
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return fmt.Errorf("some units failed to restart: %v", failedUnits)
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}
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return nil
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}
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func checkAndRenewSSHCertificates(ctx context.Context, c *vapi.Client) bool {
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sshHostKeys, err := sshHostKeyPaths(ctx)
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if err != nil {
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log.Errorf("sshHostKeyPaths: %v", err)
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return true
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}
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cs := c.SSHWithMountPoint(*sshHostKeyCAPath)
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var hadErr bool
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var didRenew bool
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for _, sshHostKeyPath := range sshHostKeys {
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outPath := filepath.Join(*sshHostKeyOutputDir, fmt.Sprintf("%s-cert.pub", strings.TrimSuffix(filepath.Base(sshHostKeyPath), ".pub")))
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log.Infof("might sign %v into %v", sshHostKeyPath, outPath)
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sshHostKey, err := readFile(sshHostKeyPath)
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if err != nil {
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log.Errorf("reading host key %v: %v", sshHostKeyPath, err)
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hadErr = true
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continue
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}
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if shouldRenew, err := shouldRenewSSHCert(outPath, sshHostKey, *sshHostKeyPrincipals); shouldRenew && err == nil {
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log.Infof("shouldRenewSSHCert for %v returned true with no reason", outPath)
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} else if shouldRenew {
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log.Infof("shouldRenewSSHCert for %v returned true: %v", outPath, err)
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} else if err != nil {
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log.Errorf("shouldRenewSSHCert for %v returned false and an error: %v", outPath, err)
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hadErr = true
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continue
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} else if !shouldRenew {
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log.Infof("shouldRenewSSHCert for %v returned false", outPath)
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continue
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}
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secret, err := cs.SignKey(*sshHostKeyRole, map[string]interface{}{
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"cert_type": "host",
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"public_key": string(sshHostKey),
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"valid_principals": *sshHostKeyPrincipals,
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})
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if err != nil {
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log.Errorf("signing %v: %v", sshHostKeyPath, err)
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hadErr = true
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continue
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}
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if err := writeFile(outPath, []byte(secret.Data["signed_key"].(string))); err != nil {
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log.Errorf("writing signed certificate to %v: %v", outPath, err)
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hadErr = true
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continue
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}
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log.Infof("renewed %v", outPath)
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didRenew = true
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}
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if didRenew {
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log.Infof("completed renewals; restarting SSHd")
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if err := reloadOrTryRestartServices(ctx, []string{"sshd.service"}); err != nil {
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log.Errorf("failed to restart sshd: %v", err)
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hadErr = true
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}
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}
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return hadErr
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}
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func checkAndRenewACMECertificates(ctx context.Context, c *vapi.Client) bool {
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return false
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}
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func main() {
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flag.Parse()
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cfg := vapi.DefaultConfig()
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cfg.Address = "https://vault.int.lukegb.com"
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cfg.AgentAddress = "http://localhost:8200"
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cfg.MaxRetries = 0
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c, err := vapi.NewClient(cfg)
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if err != nil {
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log.Exitf("failed to create vault client: %v", err)
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}
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ctx := context.Background()
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var hadErr bool
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hadErr = checkAndRenewSSHCertificates(ctx, c) || hadErr
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hadErr = checkAndRenewACMECertificates(ctx, c) || hadErr
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if hadErr {
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os.Exit(1)
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}
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}
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