litestream: fix CVE-2024-41254 by adding SSH host key verification (#421926)

diff --git a/cmd/litestream/main.go b/cmd/litestream/main.go

index 1234567..abcdefg 100644

--- a/cmd/litestream/main.go

+++ b/cmd/litestream/main.go

@@ -362,6 +362,7 @@ type ReplicaConfig struct {

 	Host     string `yaml:"host"`

 	User     string `yaml:"user"`

 	Password string `yaml:"password"`

 	KeyPath  string `yaml:"key-path"`

+	HostKeyPath string `yaml:"host-key-path"`

 	// Encryption identities and recipients

@@ -664,6 +665,7 @@ func NewReplicaFromConfig(c *ReplicaConfig, dbc *DBConfig) (_ litestream.Replic

 	client.Password = password

 	client.Path = path

 	client.KeyPath = c.KeyPath

+	client.HostKeyPath = c.HostKeyPath

 	return client, nil

 }

diff --git a/sftp/replica_client.go b/sftp/replica_client.go

index 30d8fa87..8b651e97 100644

--- a/sftp/replica_client.go

+++ b/sftp/replica_client.go

@@ -41,6 +41,7 @@ type ReplicaClient struct {

 	Password    string

 	Path        string

 	KeyPath     string

+	HostKeyPath string

 	DialTimeout time.Duration

 }

@@ -71,14 +72,28 @@ func (c *ReplicaClient) Init(ctx context.Context) (_ *sftp.Client, err error) {

 	// Build SSH configuration & auth methods

 	config := &ssh.ClientConfig{

-		User:            c.User,

-		HostKeyCallback: ssh.InsecureIgnoreHostKey(),

-		BannerCallback:  ssh.BannerDisplayStderr(),

+		User:           c.User,

+		BannerCallback: ssh.BannerDisplayStderr(),

 	}

 	if c.Password != "" {

 		config.Auth = append(config.Auth, ssh.Password(c.Password))

 	}

+	if c.HostKeyPath == "" {

+		config.HostKeyCallback = ssh.InsecureIgnoreHostKey()

+	} else {

+		buf, err := os.ReadFile(c.HostKeyPath)

+		if err != nil {

+			return nil, fmt.Errorf("cannot read sftp host key path: %w", err)

+		}

+

+		key, _, _, _, err := ssh.ParseAuthorizedKey(buf)

+		if err != nil {

+			return nil, fmt.Errorf("cannot parse sftp host key path: path=%s len=%d err=%w", c.HostKeyPath, len(buf), err)

+		}

+		config.HostKeyCallback = ssh.FixedHostKey(key)

+	}

+

 	if c.KeyPath != "" {

 		buf, err := os.ReadFile(c.KeyPath)

 		if err != nil {

 No newline at end of file

  vendorHash = "sha256-sYIY3Z3VrCqbjEbQtEY7q6Jljg8jMoa2qWEB/IkDjzM=";

  patches = [ ./fix-cve-2024-41254.patch ];

  passthru.tests = { inherit (nixosTests) litestream; };

  meta = with lib; {

    license = licenses.asl20;

    homepage = "https://litestream.io/";

    maintainers = with maintainers; [ fbrs ];

    knownVulnerabilities = [ "CVE-2024-41254" ];

  };

}