[client,management] Rewrite the SSH feature (#4015)

client/ssh/common.go

@@ -0,0 +1,171 @@
+package ssh
+
+import (
+	"bytes"
+	"context"
+	"errors"
+	"fmt"
+	"io"
+	"net"
+	"time"
+
+	log "github.com/sirupsen/logrus"
+	"golang.org/x/crypto/ssh"
+
+	"github.com/netbirdio/netbird/client/proto"
+)
+
+const (
+	NetBirdSSHConfigFile = "99-netbird.conf"
+
+	UnixSSHConfigDir    = "/etc/ssh/ssh_config.d"
+	WindowsSSHConfigDir = "ssh/ssh_config.d"
+)
+
+var (
+	// ErrPeerNotFound indicates the peer was not found in the network
+	ErrPeerNotFound = errors.New("peer not found in network")
+	// ErrNoStoredKey indicates the peer has no stored SSH host key
+	ErrNoStoredKey = errors.New("peer has no stored SSH host key")
+)
+
+// HostKeyVerifier provides SSH host key verification
+type HostKeyVerifier interface {
+	VerifySSHHostKey(peerAddress string, key []byte) error
+}
+
+// DaemonHostKeyVerifier implements HostKeyVerifier using the NetBird daemon
+type DaemonHostKeyVerifier struct {
+	client proto.DaemonServiceClient
+}
+
+// NewDaemonHostKeyVerifier creates a new daemon-based host key verifier
+func NewDaemonHostKeyVerifier(client proto.DaemonServiceClient) *DaemonHostKeyVerifier {
+	return &DaemonHostKeyVerifier{
+		client: client,
+	}
+}
+
+// VerifySSHHostKey verifies an SSH host key by querying the NetBird daemon
+func (d *DaemonHostKeyVerifier) VerifySSHHostKey(peerAddress string, presentedKey []byte) error {
+	ctx, cancel := context.WithTimeout(context.Background(), 5*time.Second)
+	defer cancel()
+
+	response, err := d.client.GetPeerSSHHostKey(ctx, &proto.GetPeerSSHHostKeyRequest{
+		PeerAddress: peerAddress,
+	})
+	if err != nil {
+		return err
+	}
+
+	if !response.GetFound() {
+		return ErrPeerNotFound
+	}
+
+	storedKeyData := response.GetSshHostKey()
+
+	return VerifyHostKey(storedKeyData, presentedKey, peerAddress)
+}
+
+// RequestJWTToken requests or retrieves a JWT token for SSH authentication
+func RequestJWTToken(ctx context.Context, client proto.DaemonServiceClient, stdout, stderr io.Writer, useCache bool, hint string) (string, error) {
+	req := &proto.RequestJWTAuthRequest{}
+	if hint != "" {
+		req.Hint = &hint
+	}
+	authResponse, err := client.RequestJWTAuth(ctx, req)
+	if err != nil {
+		return "", fmt.Errorf("request JWT auth: %w", err)
+	}
+
+	if useCache && authResponse.CachedToken != "" {
+		log.Debug("Using cached authentication token")
+		return authResponse.CachedToken, nil
+	}
+
+	if stderr != nil {
+		_, _ = fmt.Fprintln(stderr, "SSH authentication required.")
+		_, _ = fmt.Fprintf(stderr, "Please visit: %s\n", authResponse.VerificationURIComplete)
+		if authResponse.UserCode != "" {
+			_, _ = fmt.Fprintf(stderr, "Or visit: %s and enter code: %s\n", authResponse.VerificationURI, authResponse.UserCode)
+		}
+		_, _ = fmt.Fprintln(stderr, "Waiting for authentication...")
+	}
+
+	tokenResponse, err := client.WaitJWTToken(ctx, &proto.WaitJWTTokenRequest{
+		DeviceCode: authResponse.DeviceCode,
+		UserCode:   authResponse.UserCode,
+	})
+	if err != nil {
+		return "", fmt.Errorf("wait for JWT token: %w", err)
+	}
+
+	if stdout != nil {
+		_, _ = fmt.Fprintln(stdout, "Authentication successful!")
+	}
+	return tokenResponse.Token, nil
+}
+
+// VerifyHostKey verifies an SSH host key against stored peer key data.
+// Returns nil only if the presented key matches the stored key.
+// Returns ErrNoStoredKey if storedKeyData is empty.
+// Returns an error if the keys don't match or if parsing fails.
+func VerifyHostKey(storedKeyData []byte, presentedKey []byte, peerAddress string) error {
+	if len(storedKeyData) == 0 {
+		return ErrNoStoredKey
+	}
+
+	storedPubKey, _, _, _, err := ssh.ParseAuthorizedKey(storedKeyData)
+	if err != nil {
+		return fmt.Errorf("parse stored SSH key for %s: %w", peerAddress, err)
+	}
+
+	if !bytes.Equal(presentedKey, storedPubKey.Marshal()) {
+		return fmt.Errorf("SSH host key mismatch for %s", peerAddress)
+	}
+
+	return nil
+}
+
+// AddJWTAuth prepends JWT password authentication to existing auth methods.
+// This ensures JWT auth is tried first while preserving any existing auth methods.
+func AddJWTAuth(config *ssh.ClientConfig, jwtToken string) *ssh.ClientConfig {
+	configWithJWT := *config
+	configWithJWT.Auth = append([]ssh.AuthMethod{ssh.Password(jwtToken)}, config.Auth...)
+	return &configWithJWT
+}
+
+// CreateHostKeyCallback creates an SSH host key verification callback using the provided verifier.
+// It tries multiple addresses (hostname, IP) for the peer before failing.
+func CreateHostKeyCallback(verifier HostKeyVerifier) ssh.HostKeyCallback {
+	return func(hostname string, remote net.Addr, key ssh.PublicKey) error {
+		addresses := buildAddressList(hostname, remote)
+		presentedKey := key.Marshal()
+
+		for _, addr := range addresses {
+			if err := verifier.VerifySSHHostKey(addr, presentedKey); err != nil {
+				if errors.Is(err, ErrPeerNotFound) {
+					// Try other addresses for this peer
+					continue
+				}
+				return err
+			}
+			// Verified
+			return nil
+		}
+
+		return fmt.Errorf("SSH host key verification failed: peer %s not found in network", hostname)
+	}
+}
+
+// buildAddressList creates a list of addresses to check for host key verification.
+// It includes the original hostname and extracts the host part from the remote address if different.
+func buildAddressList(hostname string, remote net.Addr) []string {
+	addresses := []string{hostname}
+	if host, _, err := net.SplitHostPort(remote.String()); err == nil {
+		if host != hostname {
+			addresses = append(addresses, host)
+		}
+	}
+	return addresses
+}