diff options
Diffstat (limited to 'sftp/client.go')
| -rw-r--r-- | sftp/client.go | 1936 |
1 files changed, 1936 insertions, 0 deletions
diff --git a/sftp/client.go b/sftp/client.go new file mode 100644 index 0000000..ce62286 --- /dev/null +++ b/sftp/client.go @@ -0,0 +1,1936 @@ +package sftp + +import ( + "bytes" + "encoding/binary" + "errors" + "io" + "math" + "os" + "path" + "sync" + "sync/atomic" + "syscall" + "time" + + "github.com/kr/fs" + "golang.org/x/crypto/ssh" +) + +var ( + // ErrInternalInconsistency indicates the packets sent and the data queued to be + // written to the file don't match up. It is an unusual error and usually is + // caused by bad behavior server side or connection issues. The error is + // limited in scope to the call where it happened, the client object is still + // OK to use as long as the connection is still open. + ErrInternalInconsistency = errors.New("internal inconsistency") + // InternalInconsistency alias for ErrInternalInconsistency. + // + // Deprecated: please use ErrInternalInconsistency + InternalInconsistency = ErrInternalInconsistency +) + +// A ClientOption is a function which applies configuration to a Client. +type ClientOption func(*Client) error + +// MaxPacketChecked sets the maximum size of the payload, measured in bytes. +// This option only accepts sizes servers should support, ie. <= 32768 bytes. +// +// If you get the error "failed to send packet header: EOF" when copying a +// large file, try lowering this number. +// +// The default packet size is 32768 bytes. +func MaxPacketChecked(size int) ClientOption { + return func(c *Client) error { + if size < 1 { + return errors.New("size must be greater or equal to 1") + } + if size > 32768 { + return errors.New("sizes larger than 32KB might not work with all servers") + } + c.maxPacket = size + return nil + } +} + +// MaxPacketUnchecked sets the maximum size of the payload, measured in bytes. +// It accepts sizes larger than the 32768 bytes all servers should support. +// Only use a setting higher than 32768 if your application always connects to +// the same server or after sufficiently broad testing. +// +// If you get the error "failed to send packet header: EOF" when copying a +// large file, try lowering this number. +// +// The default packet size is 32768 bytes. +func MaxPacketUnchecked(size int) ClientOption { + return func(c *Client) error { + if size < 1 { + return errors.New("size must be greater or equal to 1") + } + c.maxPacket = size + return nil + } +} + +// MaxPacket sets the maximum size of the payload, measured in bytes. +// This option only accepts sizes servers should support, ie. <= 32768 bytes. +// This is a synonym for MaxPacketChecked that provides backward compatibility. +// +// If you get the error "failed to send packet header: EOF" when copying a +// large file, try lowering this number. +// +// The default packet size is 32768 bytes. +func MaxPacket(size int) ClientOption { + return MaxPacketChecked(size) +} + +// MaxConcurrentRequestsPerFile sets the maximum concurrent requests allowed for a single file. +// +// The default maximum concurrent requests is 64. +func MaxConcurrentRequestsPerFile(n int) ClientOption { + return func(c *Client) error { + if n < 1 { + return errors.New("n must be greater or equal to 1") + } + c.maxConcurrentRequests = n + return nil + } +} + +// UseConcurrentWrites allows the Client to perform concurrent Writes. +// +// Using concurrency while doing writes, requires special consideration. +// A write to a later offset in a file after an error, +// could end up with a file length longer than what was successfully written. +// +// When using this option, if you receive an error during `io.Copy` or `io.WriteTo`, +// you may need to `Truncate` the target Writer to avoid “holes” in the data written. +func UseConcurrentWrites(value bool) ClientOption { + return func(c *Client) error { + c.useConcurrentWrites = value + return nil + } +} + +// UseConcurrentReads allows the Client to perform concurrent Reads. +// +// Concurrent reads are generally safe to use and not using them will degrade +// performance, so this option is enabled by default. +// +// When enabled, WriteTo will use Stat/Fstat to get the file size and determines +// how many concurrent workers to use. +// Some "read once" servers will delete the file if they receive a stat call on an +// open file and then the download will fail. +// Disabling concurrent reads you will be able to download files from these servers. +// If concurrent reads are disabled, the UseFstat option is ignored. +func UseConcurrentReads(value bool) ClientOption { + return func(c *Client) error { + c.disableConcurrentReads = !value + return nil + } +} + +// UseFstat sets whether to use Fstat or Stat when File.WriteTo is called +// (usually when copying files). +// Some servers limit the amount of open files and calling Stat after opening +// the file will throw an error From the server. Setting this flag will call +// Fstat instead of Stat which is suppose to be called on an open file handle. +// +// It has been found that that with IBM Sterling SFTP servers which have +// "extractability" level set to 1 which means only 1 file can be opened at +// any given time. +// +// If the server you are working with still has an issue with both Stat and +// Fstat calls you can always open a file and read it until the end. +// +// Another reason to read the file until its end and Fstat doesn't work is +// that in some servers, reading a full file will automatically delete the +// file as some of these mainframes map the file to a message in a queue. +// Once the file has been read it will get deleted. +func UseFstat(value bool) ClientOption { + return func(c *Client) error { + c.useFstat = value + return nil + } +} + +// Client represents an SFTP session on a *ssh.ClientConn SSH connection. +// Multiple Clients can be active on a single SSH connection, and a Client +// may be called concurrently from multiple Goroutines. +// +// Client implements the github.com/kr/fs.FileSystem interface. +type Client struct { + clientConn + + ext map[string]string // Extensions (name -> data). + + maxPacket int // max packet size read or written. + maxConcurrentRequests int + nextid uint32 + + // write concurrency is… error prone. + // Default behavior should be to not use it. + useConcurrentWrites bool + useFstat bool + disableConcurrentReads bool +} + +// NewClient creates a new SFTP client on conn, using zero or more option +// functions. +func NewClient(conn *ssh.Client, opts ...ClientOption) (*Client, error) { + s, err := conn.NewSession() + if err != nil { + return nil, err + } + if err := s.RequestSubsystem("sftp"); err != nil { + return nil, err + } + pw, err := s.StdinPipe() + if err != nil { + return nil, err + } + pr, err := s.StdoutPipe() + if err != nil { + return nil, err + } + + return NewClientPipe(pr, pw, opts...) +} + +// NewClientPipe creates a new SFTP client given a Reader and a WriteCloser. +// This can be used for connecting to an SFTP server over TCP/TLS or by using +// the system's ssh client program (e.g. via exec.Command). +func NewClientPipe(rd io.Reader, wr io.WriteCloser, opts ...ClientOption) (*Client, error) { + sftp := &Client{ + clientConn: clientConn{ + conn: conn{ + Reader: rd, + WriteCloser: wr, + }, + inflight: make(map[uint32]chan<- result), + closed: make(chan struct{}), + }, + + ext: make(map[string]string), + + maxPacket: 1 << 15, + maxConcurrentRequests: 64, + } + + for _, opt := range opts { + if err := opt(sftp); err != nil { + wr.Close() + return nil, err + } + } + + if err := sftp.sendInit(); err != nil { + wr.Close() + return nil, err + } + if err := sftp.recvVersion(); err != nil { + wr.Close() + return nil, err + } + + sftp.clientConn.wg.Add(1) + go sftp.loop() + + return sftp, nil +} + +// Create creates the named file mode 0666 (before umask), truncating it if it +// already exists. If successful, methods on the returned File can be used for +// I/O; the associated file descriptor has mode O_RDWR. If you need more +// control over the flags/mode used to open the file see client.OpenFile. +// +// Note that some SFTP servers (eg. AWS Transfer) do not support opening files +// read/write at the same time. For those services you will need to use +// `client.OpenFile(os.O_WRONLY|os.O_CREATE|os.O_TRUNC)`. +func (c *Client) Create(path string) (*File, error) { + return c.open(path, flags(os.O_RDWR|os.O_CREATE|os.O_TRUNC)) +} + +const sftpProtocolVersion = 3 // http://tools.ietf.org/html/draft-ietf-secsh-filexfer-02 + +func (c *Client) sendInit() error { + return c.clientConn.conn.sendPacket(&sshFxInitPacket{ + Version: sftpProtocolVersion, // http://tools.ietf.org/html/draft-ietf-secsh-filexfer-02 + }) +} + +// returns the next value of c.nextid +func (c *Client) nextID() uint32 { + return atomic.AddUint32(&c.nextid, 1) +} + +func (c *Client) recvVersion() error { + typ, data, err := c.recvPacket(0) + if err != nil { + return err + } + if typ != sshFxpVersion { + return &unexpectedPacketErr{sshFxpVersion, typ} + } + + version, data, err := unmarshalUint32Safe(data) + if err != nil { + return err + } + if version != sftpProtocolVersion { + return &unexpectedVersionErr{sftpProtocolVersion, version} + } + + for len(data) > 0 { + var ext extensionPair + ext, data, err = unmarshalExtensionPair(data) + if err != nil { + return err + } + c.ext[ext.Name] = ext.Data + } + + return nil +} + +// HasExtension checks whether the server supports a named extension. +// +// The first return value is the extension data reported by the server +// (typically a version number). +func (c *Client) HasExtension(name string) (string, bool) { + data, ok := c.ext[name] + return data, ok +} + +// Walk returns a new Walker rooted at root. +func (c *Client) Walk(root string) *fs.Walker { + return fs.WalkFS(root, c) +} + +// ReadDir reads the directory named by dirname and returns a list of +// directory entries. +func (c *Client) ReadDir(p string) ([]os.FileInfo, error) { + handle, err := c.opendir(p) + if err != nil { + return nil, err + } + defer c.close(handle) // this has to defer earlier than the lock below + var attrs []os.FileInfo + var done = false + for !done { + id := c.nextID() + typ, data, err1 := c.sendPacket(nil, &sshFxpReaddirPacket{ + ID: id, + Handle: handle, + }) + if err1 != nil { + err = err1 + done = true + break + } + switch typ { + case sshFxpName: + sid, data := unmarshalUint32(data) + if sid != id { + return nil, &unexpectedIDErr{id, sid} + } + count, data := unmarshalUint32(data) + for i := uint32(0); i < count; i++ { + var filename string + filename, data = unmarshalString(data) + _, data = unmarshalString(data) // discard longname + var attr *FileStat + attr, data = unmarshalAttrs(data) + if filename == "." || filename == ".." { + continue + } + attrs = append(attrs, fileInfoFromStat(attr, path.Base(filename))) + } + case sshFxpStatus: + // TODO(dfc) scope warning! + err = normaliseError(unmarshalStatus(id, data)) + done = true + default: + return nil, unimplementedPacketErr(typ) + } + } + if err == io.EOF { + err = nil + } + return attrs, err +} + +func (c *Client) opendir(path string) (string, error) { + id := c.nextID() + typ, data, err := c.sendPacket(nil, &sshFxpOpendirPacket{ + ID: id, + Path: path, + }) + if err != nil { + return "", err + } + switch typ { + case sshFxpHandle: + sid, data := unmarshalUint32(data) + if sid != id { + return "", &unexpectedIDErr{id, sid} + } + handle, _ := unmarshalString(data) + return handle, nil + case sshFxpStatus: + return "", normaliseError(unmarshalStatus(id, data)) + default: + return "", unimplementedPacketErr(typ) + } +} + +// Stat returns a FileInfo structure describing the file specified by path 'p'. +// If 'p' is a symbolic link, the returned FileInfo structure describes the referent file. +func (c *Client) Stat(p string) (os.FileInfo, error) { + fs, err := c.stat(p) + if err != nil { + return nil, err + } + return fileInfoFromStat(fs, path.Base(p)), nil +} + +// Lstat returns a FileInfo structure describing the file specified by path 'p'. +// If 'p' is a symbolic link, the returned FileInfo structure describes the symbolic link. +func (c *Client) Lstat(p string) (os.FileInfo, error) { + id := c.nextID() + typ, data, err := c.sendPacket(nil, &sshFxpLstatPacket{ + ID: id, + Path: p, + }) + if err != nil { + return nil, err + } + switch typ { + case sshFxpAttrs: + sid, data := unmarshalUint32(data) + if sid != id { + return nil, &unexpectedIDErr{id, sid} + } + attr, _ := unmarshalAttrs(data) + return fileInfoFromStat(attr, path.Base(p)), nil + case sshFxpStatus: + return nil, normaliseError(unmarshalStatus(id, data)) + default: + return nil, unimplementedPacketErr(typ) + } +} + +// ReadLink reads the target of a symbolic link. +func (c *Client) ReadLink(p string) (string, error) { + id := c.nextID() + typ, data, err := c.sendPacket(nil, &sshFxpReadlinkPacket{ + ID: id, + Path: p, + }) + if err != nil { + return "", err + } + switch typ { + case sshFxpName: + sid, data := unmarshalUint32(data) + if sid != id { + return "", &unexpectedIDErr{id, sid} + } + count, data := unmarshalUint32(data) + if count != 1 { + return "", unexpectedCount(1, count) + } + filename, _ := unmarshalString(data) // ignore dummy attributes + return filename, nil + case sshFxpStatus: + return "", normaliseError(unmarshalStatus(id, data)) + default: + return "", unimplementedPacketErr(typ) + } +} + +// Link creates a hard link at 'newname', pointing at the same inode as 'oldname' +func (c *Client) Link(oldname, newname string) error { + id := c.nextID() + typ, data, err := c.sendPacket(nil, &sshFxpHardlinkPacket{ + ID: id, + Oldpath: oldname, + Newpath: newname, + }) + if err != nil { + return err + } + switch typ { + case sshFxpStatus: + return normaliseError(unmarshalStatus(id, data)) + default: + return unimplementedPacketErr(typ) + } +} + +// Symlink creates a symbolic link at 'newname', pointing at target 'oldname' +func (c *Client) Symlink(oldname, newname string) error { + id := c.nextID() + typ, data, err := c.sendPacket(nil, &sshFxpSymlinkPacket{ + ID: id, + Linkpath: newname, + Targetpath: oldname, + }) + if err != nil { + return err + } + switch typ { + case sshFxpStatus: + return normaliseError(unmarshalStatus(id, data)) + default: + return unimplementedPacketErr(typ) + } +} + +func (c *Client) setfstat(handle string, flags uint32, attrs interface{}) error { + id := c.nextID() + typ, data, err := c.sendPacket(nil, &sshFxpFsetstatPacket{ + ID: id, + Handle: handle, + Flags: flags, + Attrs: attrs, + }) + if err != nil { + return err + } + switch typ { + case sshFxpStatus: + return normaliseError(unmarshalStatus(id, data)) + default: + return unimplementedPacketErr(typ) + } +} + +// setstat is a convience wrapper to allow for changing of various parts of the file descriptor. +func (c *Client) setstat(path string, flags uint32, attrs interface{}) error { + id := c.nextID() + typ, data, err := c.sendPacket(nil, &sshFxpSetstatPacket{ + ID: id, + Path: path, + Flags: flags, + Attrs: attrs, + }) + if err != nil { + return err + } + switch typ { + case sshFxpStatus: + return normaliseError(unmarshalStatus(id, data)) + default: + return unimplementedPacketErr(typ) + } +} + +// Chtimes changes the access and modification times of the named file. +func (c *Client) Chtimes(path string, atime time.Time, mtime time.Time) error { + type times struct { + Atime uint32 + Mtime uint32 + } + attrs := times{uint32(atime.Unix()), uint32(mtime.Unix())} + return c.setstat(path, sshFileXferAttrACmodTime, attrs) +} + +// Chown changes the user and group owners of the named file. +func (c *Client) Chown(path string, uid, gid int) error { + type owner struct { + UID uint32 + GID uint32 + } + attrs := owner{uint32(uid), uint32(gid)} + return c.setstat(path, sshFileXferAttrUIDGID, attrs) +} + +// Chmod changes the permissions of the named file. +// +// Chmod does not apply a umask, because even retrieving the umask is not +// possible in a portable way without causing a race condition. Callers +// should mask off umask bits, if desired. +func (c *Client) Chmod(path string, mode os.FileMode) error { + return c.setstat(path, sshFileXferAttrPermissions, toChmodPerm(mode)) +} + +// Truncate sets the size of the named file. Although it may be safely assumed +// that if the size is less than its current size it will be truncated to fit, +// the SFTP protocol does not specify what behavior the server should do when setting +// size greater than the current size. +func (c *Client) Truncate(path string, size int64) error { + return c.setstat(path, sshFileXferAttrSize, uint64(size)) +} + +// Open opens the named file for reading. If successful, methods on the +// returned file can be used for reading; the associated file descriptor +// has mode O_RDONLY. +func (c *Client) Open(path string) (*File, error) { + return c.open(path, flags(os.O_RDONLY)) +} + +// OpenFile is the generalized open call; most users will use Open or +// Create instead. It opens the named file with specified flag (O_RDONLY +// etc.). If successful, methods on the returned File can be used for I/O. +func (c *Client) OpenFile(path string, f int) (*File, error) { + return c.open(path, flags(f)) +} + +func (c *Client) open(path string, pflags uint32) (*File, error) { + id := c.nextID() + typ, data, err := c.sendPacket(nil, &sshFxpOpenPacket{ + ID: id, + Path: path, + Pflags: pflags, + }) + if err != nil { + return nil, err + } + switch typ { + case sshFxpHandle: + sid, data := unmarshalUint32(data) + if sid != id { + return nil, &unexpectedIDErr{id, sid} + } + handle, _ := unmarshalString(data) + return &File{c: c, path: path, handle: handle}, nil + case sshFxpStatus: + return nil, normaliseError(unmarshalStatus(id, data)) + default: + return nil, unimplementedPacketErr(typ) + } +} + +// close closes a handle handle previously returned in the response +// to SSH_FXP_OPEN or SSH_FXP_OPENDIR. The handle becomes invalid +// immediately after this request has been sent. +func (c *Client) close(handle string) error { + id := c.nextID() + typ, data, err := c.sendPacket(nil, &sshFxpClosePacket{ + ID: id, + Handle: handle, + }) + if err != nil { + return err + } + switch typ { + case sshFxpStatus: + return normaliseError(unmarshalStatus(id, data)) + default: + return unimplementedPacketErr(typ) + } +} + +func (c *Client) stat(path string) (*FileStat, error) { + id := c.nextID() + typ, data, err := c.sendPacket(nil, &sshFxpStatPacket{ + ID: id, + Path: path, + }) + if err != nil { + return nil, err + } + switch typ { + case sshFxpAttrs: + sid, data := unmarshalUint32(data) + if sid != id { + return nil, &unexpectedIDErr{id, sid} + } + attr, _ := unmarshalAttrs(data) + return attr, nil + case sshFxpStatus: + return nil, normaliseError(unmarshalStatus(id, data)) + default: + return nil, unimplementedPacketErr(typ) + } +} + +func (c *Client) fstat(handle string) (*FileStat, error) { + id := c.nextID() + typ, data, err := c.sendPacket(nil, &sshFxpFstatPacket{ + ID: id, + Handle: handle, + }) + if err != nil { + return nil, err + } + switch typ { + case sshFxpAttrs: + sid, data := unmarshalUint32(data) + if sid != id { + return nil, &unexpectedIDErr{id, sid} + } + attr, _ := unmarshalAttrs(data) + return attr, nil + case sshFxpStatus: + return nil, normaliseError(unmarshalStatus(id, data)) + default: + return nil, unimplementedPacketErr(typ) + } +} + +// StatVFS retrieves VFS statistics from a remote host. +// +// It implements the statvfs@openssh.com SSH_FXP_EXTENDED feature +// from http://www.opensource.apple.com/source/OpenSSH/OpenSSH-175/openssh/PROTOCOL?txt. +func (c *Client) StatVFS(path string) (*StatVFS, error) { + // send the StatVFS packet to the server + id := c.nextID() + typ, data, err := c.sendPacket(nil, &sshFxpStatvfsPacket{ + ID: id, + Path: path, + }) + if err != nil { + return nil, err + } + + switch typ { + // server responded with valid data + case sshFxpExtendedReply: + var response StatVFS + err = binary.Read(bytes.NewReader(data), binary.BigEndian, &response) + if err != nil { + return nil, errors.New("can not parse reply") + } + + return &response, nil + + // the resquest failed + case sshFxpStatus: + return nil, normaliseError(unmarshalStatus(id, data)) + + default: + return nil, unimplementedPacketErr(typ) + } +} + +// Join joins any number of path elements into a single path, adding a +// separating slash if necessary. The result is Cleaned; in particular, all +// empty strings are ignored. +func (c *Client) Join(elem ...string) string { return path.Join(elem...) } + +// Remove removes the specified file or directory. An error will be returned if no +// file or directory with the specified path exists, or if the specified directory +// is not empty. +func (c *Client) Remove(path string) error { + err := c.removeFile(path) + // some servers, *cough* osx *cough*, return EPERM, not ENODIR. + // serv-u returns ssh_FX_FILE_IS_A_DIRECTORY + // EPERM is converted to os.ErrPermission so it is not a StatusError + if err, ok := err.(*StatusError); ok { + switch err.Code { + case sshFxFailure, sshFxFileIsADirectory: + return c.RemoveDirectory(path) + } + } + if os.IsPermission(err) { + return c.RemoveDirectory(path) + } + return err +} + +func (c *Client) removeFile(path string) error { + id := c.nextID() + typ, data, err := c.sendPacket(nil, &sshFxpRemovePacket{ + ID: id, + Filename: path, + }) + if err != nil { + return err + } + switch typ { + case sshFxpStatus: + return normaliseError(unmarshalStatus(id, data)) + default: + return unimplementedPacketErr(typ) + } +} + +// RemoveDirectory removes a directory path. +func (c *Client) RemoveDirectory(path string) error { + id := c.nextID() + typ, data, err := c.sendPacket(nil, &sshFxpRmdirPacket{ + ID: id, + Path: path, + }) + if err != nil { + return err + } + switch typ { + case sshFxpStatus: + return normaliseError(unmarshalStatus(id, data)) + default: + return unimplementedPacketErr(typ) + } +} + +// Rename renames a file. +func (c *Client) Rename(oldname, newname string) error { + id := c.nextID() + typ, data, err := c.sendPacket(nil, &sshFxpRenamePacket{ + ID: id, + Oldpath: oldname, + Newpath: newname, + }) + if err != nil { + return err + } + switch typ { + case sshFxpStatus: + return normaliseError(unmarshalStatus(id, data)) + default: + return unimplementedPacketErr(typ) + } +} + +// PosixRename renames a file using the posix-rename@openssh.com extension +// which will replace newname if it already exists. +func (c *Client) PosixRename(oldname, newname string) error { + id := c.nextID() + typ, data, err := c.sendPacket(nil, &sshFxpPosixRenamePacket{ + ID: id, + Oldpath: oldname, + Newpath: newname, + }) + if err != nil { + return err + } + switch typ { + case sshFxpStatus: + return normaliseError(unmarshalStatus(id, data)) + default: + return unimplementedPacketErr(typ) + } +} + +// RealPath can be used to have the server canonicalize any given path name to an absolute path. +// +// This is useful for converting path names containing ".." components, +// or relative pathnames without a leading slash into absolute paths. +func (c *Client) RealPath(path string) (string, error) { + id := c.nextID() + typ, data, err := c.sendPacket(nil, &sshFxpRealpathPacket{ + ID: id, + Path: path, + }) + if err != nil { + return "", err + } + switch typ { + case sshFxpName: + sid, data := unmarshalUint32(data) + if sid != id { + return "", &unexpectedIDErr{id, sid} + } + count, data := unmarshalUint32(data) + if count != 1 { + return "", unexpectedCount(1, count) + } + filename, _ := unmarshalString(data) // ignore attributes + return filename, nil + case sshFxpStatus: + return "", normaliseError(unmarshalStatus(id, data)) + default: + return "", unimplementedPacketErr(typ) + } +} + +// Getwd returns the current working directory of the server. Operations +// involving relative paths will be based at this location. +func (c *Client) Getwd() (string, error) { + return c.RealPath(".") +} + +// Mkdir creates the specified directory. An error will be returned if a file or +// directory with the specified path already exists, or if the directory's +// parent folder does not exist (the method cannot create complete paths). +func (c *Client) Mkdir(path string) error { + id := c.nextID() + typ, data, err := c.sendPacket(nil, &sshFxpMkdirPacket{ + ID: id, + Path: path, + }) + if err != nil { + return err + } + switch typ { + case sshFxpStatus: + return normaliseError(unmarshalStatus(id, data)) + default: + return unimplementedPacketErr(typ) + } +} + +// MkdirAll creates a directory named path, along with any necessary parents, +// and returns nil, or else returns an error. +// If path is already a directory, MkdirAll does nothing and returns nil. +// If path contains a regular file, an error is returned +func (c *Client) MkdirAll(path string) error { + // Most of this code mimics https://golang.org/src/os/path.go?s=514:561#L13 + // Fast path: if we can tell whether path is a directory or file, stop with success or error. + dir, err := c.Stat(path) + if err == nil { + if dir.IsDir() { + return nil + } + return &os.PathError{Op: "mkdir", Path: path, Err: syscall.ENOTDIR} + } + + // Slow path: make sure parent exists and then call Mkdir for path. + i := len(path) + for i > 0 && path[i-1] == '/' { // Skip trailing path separator. + i-- + } + + j := i + for j > 0 && path[j-1] != '/' { // Scan backward over element. + j-- + } + + if j > 1 { + // Create parent + err = c.MkdirAll(path[0 : j-1]) + if err != nil { + return err + } + } + + // Parent now exists; invoke Mkdir and use its result. + err = c.Mkdir(path) + if err != nil { + // Handle arguments like "foo/." by + // double-checking that directory doesn't exist. + dir, err1 := c.Lstat(path) + if err1 == nil && dir.IsDir() { + return nil + } + return err + } + return nil +} + +// File represents a remote file. +type File struct { + c *Client + path string + handle string + + mu sync.Mutex + offset int64 // current offset within remote file +} + +// Close closes the File, rendering it unusable for I/O. It returns an +// error, if any. +func (f *File) Close() error { + return f.c.close(f.handle) +} + +// Name returns the name of the file as presented to Open or Create. +func (f *File) Name() string { + return f.path +} + +// Read reads up to len(b) bytes from the File. It returns the number of bytes +// read and an error, if any. Read follows io.Reader semantics, so when Read +// encounters an error or EOF condition after successfully reading n > 0 bytes, +// it returns the number of bytes read. +// +// To maximise throughput for transferring the entire file (especially +// over high latency links) it is recommended to use WriteTo rather +// than calling Read multiple times. io.Copy will do this +// automatically. +func (f *File) Read(b []byte) (int, error) { + f.mu.Lock() + defer f.mu.Unlock() + + n, err := f.ReadAt(b, f.offset) + f.offset += int64(n) + return n, err +} + +// readChunkAt attempts to read the whole entire length of the buffer from the file starting at the offset. +// It will continue progressively reading into the buffer until it fills the whole buffer, or an error occurs. +func (f *File) readChunkAt(ch chan result, b []byte, off int64) (n int, err error) { + for err == nil && n < len(b) { + id := f.c.nextID() + typ, data, err := f.c.sendPacket(ch, &sshFxpReadPacket{ + ID: id, + Handle: f.handle, + Offset: uint64(off) + uint64(n), + Len: uint32(len(b) - n), + }) + if err != nil { + return n, err + } + + switch typ { + case sshFxpStatus: + return n, normaliseError(unmarshalStatus(id, data)) + + case sshFxpData: + sid, data := unmarshalUint32(data) + if id != sid { + return n, &unexpectedIDErr{id, sid} + } + + l, data := unmarshalUint32(data) + n += copy(b[n:], data[:l]) + + default: + return n, unimplementedPacketErr(typ) + } + } + + return +} + +func (f *File) readAtSequential(b []byte, off int64) (read int, err error) { + for read < len(b) { + rb := b[read:] + if len(rb) > f.c.maxPacket { + rb = rb[:f.c.maxPacket] + } + n, err := f.readChunkAt(nil, rb, off+int64(read)) + if n < 0 { + panic("sftp.File: returned negative count from readChunkAt") + } + if n > 0 { + read += n + } + if err != nil { + if errors.Is(err, io.EOF) { + return read, nil // return nil explicitly. + } + return read, err + } + } + return read, nil +} + +// ReadAt reads up to len(b) byte from the File at a given offset `off`. It returns +// the number of bytes read and an error, if any. ReadAt follows io.ReaderAt semantics, +// so the file offset is not altered during the read. +func (f *File) ReadAt(b []byte, off int64) (int, error) { + if len(b) <= f.c.maxPacket { + // This should be able to be serviced with 1/2 requests. + // So, just do it directly. + return f.readChunkAt(nil, b, off) + } + + if f.c.disableConcurrentReads { + return f.readAtSequential(b, off) + } + + // Split the read into multiple maxPacket-sized concurrent reads bounded by maxConcurrentRequests. + // This allows writes with a suitably large buffer to transfer data at a much faster rate + // by overlapping round trip times. + + cancel := make(chan struct{}) + + concurrency := len(b)/f.c.maxPacket + 1 + if concurrency > f.c.maxConcurrentRequests || concurrency < 1 { + concurrency = f.c.maxConcurrentRequests + } + + resPool := newResChanPool(concurrency) + + type work struct { + id uint32 + res chan result + + b []byte + off int64 + } + workCh := make(chan work) + + // Slice: cut up the Read into any number of buffers of length <= f.c.maxPacket, and at appropriate offsets. + go func() { + defer close(workCh) + + b := b + offset := off + chunkSize := f.c.maxPacket + + for len(b) > 0 { + rb := b + if len(rb) > chunkSize { + rb = rb[:chunkSize] + } + + id := f.c.nextID() + res := resPool.Get() + + f.c.dispatchRequest(res, &sshFxpReadPacket{ + ID: id, + Handle: f.handle, + Offset: uint64(offset), + Len: uint32(chunkSize), + }) + + select { + case workCh <- work{id, res, rb, offset}: + case <-cancel: + return + } + + offset += int64(len(rb)) + b = b[len(rb):] + } + }() + + type rErr struct { + off int64 + err error + } + errCh := make(chan rErr) + + var wg sync.WaitGroup + wg.Add(concurrency) + for i := 0; i < concurrency; i++ { + // Map_i: each worker gets work, and then performs the Read into its buffer from its respective offset. + go func() { + defer wg.Done() + + for packet := range workCh { + var n int + + s := <-packet.res + resPool.Put(packet.res) + + err := s.err + if err == nil { + switch s.typ { + case sshFxpStatus: + err = normaliseError(unmarshalStatus(packet.id, s.data)) + + case sshFxpData: + sid, data := unmarshalUint32(s.data) + if packet.id != sid { + err = &unexpectedIDErr{packet.id, sid} + + } else { + l, data := unmarshalUint32(data) + n = copy(packet.b, data[:l]) + + // For normal disk files, it is guaranteed that this will read + // the specified number of bytes, or up to end of file. + // This implies, if we have a short read, that means EOF. + if n < len(packet.b) { + err = io.EOF + } + } + + default: + err = unimplementedPacketErr(s.typ) + } + } + + if err != nil { + // return the offset as the start + how much we read before the error. + errCh <- rErr{packet.off + int64(n), err} + return + } + } + }() + } + + // Wait for long tail, before closing results. + go func() { + wg.Wait() + close(errCh) + }() + + // Reduce: collect all the results into a relevant return: the earliest offset to return an error. + firstErr := rErr{math.MaxInt64, nil} + for rErr := range errCh { + if rErr.off <= firstErr.off { + firstErr = rErr + } + + select { + case <-cancel: + default: + // stop any more work from being distributed. (Just in case.) + close(cancel) + } + } + + if firstErr.err != nil { + // firstErr.err != nil if and only if firstErr.off > our starting offset. + return int(firstErr.off - off), firstErr.err + } + + // As per spec for io.ReaderAt, we return nil error if and only if we read everything. + return len(b), nil +} + +// writeToSequential implements WriteTo, but works sequentially with no parallelism. +func (f *File) writeToSequential(w io.Writer) (written int64, err error) { + b := make([]byte, f.c.maxPacket) + ch := make(chan result, 1) // reusable channel + + for { + n, err := f.readChunkAt(ch, b, f.offset) + if n < 0 { + panic("sftp.File: returned negative count from readChunkAt") + } + + if n > 0 { + f.offset += int64(n) + + m, err2 := w.Write(b[:n]) + written += int64(m) + + if err == nil { + err = err2 + } + } + + if err != nil { + if err == io.EOF { + return written, nil // return nil explicitly. + } + + return written, err + } + } +} + +// WriteTo writes the file to the given Writer. +// The return value is the number of bytes written. +// Any error encountered during the write is also returned. +// +// This method is preferred over calling Read multiple times +// to maximise throughput for transferring the entire file, +// especially over high latency links. +func (f *File) WriteTo(w io.Writer) (written int64, err error) { + f.mu.Lock() + defer f.mu.Unlock() + + if f.c.disableConcurrentReads { + return f.writeToSequential(w) + } + + // For concurrency, we want to guess how many concurrent workers we should use. + var fileStat *FileStat + if f.c.useFstat { + fileStat, err = f.c.fstat(f.handle) + } else { + fileStat, err = f.c.stat(f.path) + } + if err != nil { + return 0, err + } + + fileSize := fileStat.Size + if fileSize <= uint64(f.c.maxPacket) || !isRegular(fileStat.Mode) { + // only regular files are guaranteed to return (full read) xor (partial read, next error) + return f.writeToSequential(w) + } + + concurrency64 := fileSize/uint64(f.c.maxPacket) + 1 // a bad guess, but better than no guess + if concurrency64 > uint64(f.c.maxConcurrentRequests) || concurrency64 < 1 { + concurrency64 = uint64(f.c.maxConcurrentRequests) + } + // Now that concurrency64 is saturated to an int value, we know this assignment cannot possibly overflow. + concurrency := int(concurrency64) + + chunkSize := f.c.maxPacket + pool := newBufPool(concurrency, chunkSize) + resPool := newResChanPool(concurrency) + + cancel := make(chan struct{}) + var wg sync.WaitGroup + defer func() { + // Once the writing Reduce phase has ended, all the feed work needs to unconditionally stop. + close(cancel) + + // We want to wait until all outstanding goroutines with an `f` or `f.c` reference have completed. + // Just to be sure we don’t orphan any goroutines any hanging references. + wg.Wait() + }() + + type writeWork struct { + b []byte + off int64 + err error + + next chan writeWork + } + writeCh := make(chan writeWork) + + type readWork struct { + id uint32 + res chan result + off int64 + + cur, next chan writeWork + } + readCh := make(chan readWork) + + // Slice: hand out chunks of work on demand, with a `cur` and `next` channel built-in for sequencing. + go func() { + defer close(readCh) + + off := f.offset + + cur := writeCh + for { + id := f.c.nextID() + res := resPool.Get() + + next := make(chan writeWork) + readWork := readWork{ + id: id, + res: res, + off: off, + + cur: cur, + next: next, + } + + f.c.dispatchRequest(res, &sshFxpReadPacket{ + ID: id, + Handle: f.handle, + Offset: uint64(off), + Len: uint32(chunkSize), + }) + + select { + case readCh <- readWork: + case <-cancel: + return + } + + off += int64(chunkSize) + cur = next + } + }() + + wg.Add(concurrency) + for i := 0; i < concurrency; i++ { + // Map_i: each worker gets readWork, and does the Read into a buffer at the given offset. + go func() { + defer wg.Done() + + for readWork := range readCh { + var b []byte + var n int + + s := <-readWork.res + resPool.Put(readWork.res) + + err := s.err + if err == nil { + switch s.typ { + case sshFxpStatus: + err = normaliseError(unmarshalStatus(readWork.id, s.data)) + + case sshFxpData: + sid, data := unmarshalUint32(s.data) + if readWork.id != sid { + err = &unexpectedIDErr{readWork.id, sid} + + } else { + l, data := unmarshalUint32(data) + b = pool.Get()[:l] + n = copy(b, data[:l]) + b = b[:n] + } + + default: + err = unimplementedPacketErr(s.typ) + } + } + + writeWork := writeWork{ + b: b, + off: readWork.off, + err: err, + + next: readWork.next, + } + + select { + case readWork.cur <- writeWork: + case <-cancel: + return + } + + if err != nil { + return + } + } + }() + } + + // Reduce: serialize the results from the reads into sequential writes. + cur := writeCh + for { + packet, ok := <-cur + if !ok { + return written, errors.New("sftp.File.WriteTo: unexpectedly closed channel") + } + + // Because writes are serialized, this will always be the last successfully read byte. + f.offset = packet.off + int64(len(packet.b)) + + if len(packet.b) > 0 { + n, err := w.Write(packet.b) + written += int64(n) + if err != nil { + return written, err + } + } + + if packet.err != nil { + if packet.err == io.EOF { + return written, nil + } + + return written, packet.err + } + + pool.Put(packet.b) + cur = packet.next + } +} + +// Stat returns the FileInfo structure describing file. If there is an +// error. +func (f *File) Stat() (os.FileInfo, error) { + fs, err := f.c.fstat(f.handle) + if err != nil { + return nil, err + } + return fileInfoFromStat(fs, path.Base(f.path)), nil +} + +// Write writes len(b) bytes to the File. It returns the number of bytes +// written and an error, if any. Write returns a non-nil error when n != +// len(b). +// +// To maximise throughput for transferring the entire file (especially +// over high latency links) it is recommended to use ReadFrom rather +// than calling Write multiple times. io.Copy will do this +// automatically. +func (f *File) Write(b []byte) (int, error) { + f.mu.Lock() + defer f.mu.Unlock() + + n, err := f.WriteAt(b, f.offset) + f.offset += int64(n) + return n, err +} + +func (f *File) writeChunkAt(ch chan result, b []byte, off int64) (int, error) { + typ, data, err := f.c.sendPacket(ch, &sshFxpWritePacket{ + ID: f.c.nextID(), + Handle: f.handle, + Offset: uint64(off), + Length: uint32(len(b)), + Data: b, + }) + if err != nil { + return 0, err + } + + switch typ { + case sshFxpStatus: + id, _ := unmarshalUint32(data) + err := normaliseError(unmarshalStatus(id, data)) + if err != nil { + return 0, err + } + + default: + return 0, unimplementedPacketErr(typ) + } + + return len(b), nil +} + +// writeAtConcurrent implements WriterAt, but works concurrently rather than sequentially. +func (f *File) writeAtConcurrent(b []byte, off int64) (int, error) { + // Split the write into multiple maxPacket sized concurrent writes + // bounded by maxConcurrentRequests. This allows writes with a suitably + // large buffer to transfer data at a much faster rate due to + // overlapping round trip times. + + cancel := make(chan struct{}) + + type work struct { + b []byte + off int64 + } + workCh := make(chan work) + + // Slice: cut up the Read into any number of buffers of length <= f.c.maxPacket, and at appropriate offsets. + go func() { + defer close(workCh) + + var read int + chunkSize := f.c.maxPacket + + for read < len(b) { + wb := b[read:] + if len(wb) > chunkSize { + wb = wb[:chunkSize] + } + + select { + case workCh <- work{wb, off + int64(read)}: + case <-cancel: + return + } + + read += len(wb) + } + }() + + type wErr struct { + off int64 + err error + } + errCh := make(chan wErr) + + concurrency := len(b)/f.c.maxPacket + 1 + if concurrency > f.c.maxConcurrentRequests || concurrency < 1 { + concurrency = f.c.maxConcurrentRequests + } + + var wg sync.WaitGroup + wg.Add(concurrency) + for i := 0; i < concurrency; i++ { + // Map_i: each worker gets work, and does the Write from each buffer to its respective offset. + go func() { + defer wg.Done() + + ch := make(chan result, 1) // reusable channel per mapper. + + for packet := range workCh { + n, err := f.writeChunkAt(ch, packet.b, packet.off) + if err != nil { + // return the offset as the start + how much we wrote before the error. + errCh <- wErr{packet.off + int64(n), err} + } + } + }() + } + + // Wait for long tail, before closing results. + go func() { + wg.Wait() + close(errCh) + }() + + // Reduce: collect all the results into a relevant return: the earliest offset to return an error. + firstErr := wErr{math.MaxInt64, nil} + for wErr := range errCh { + if wErr.off <= firstErr.off { + firstErr = wErr + } + + select { + case <-cancel: + default: + // stop any more work from being distributed. (Just in case.) + close(cancel) + } + } + + if firstErr.err != nil { + // firstErr.err != nil if and only if firstErr.off >= our starting offset. + return int(firstErr.off - off), firstErr.err + } + + return len(b), nil +} + +// WriteAt writes up to len(b) byte to the File at a given offset `off`. It returns +// the number of bytes written and an error, if any. WriteAt follows io.WriterAt semantics, +// so the file offset is not altered during the write. +func (f *File) WriteAt(b []byte, off int64) (written int, err error) { + if len(b) <= f.c.maxPacket { + // We can do this in one write. + return f.writeChunkAt(nil, b, off) + } + + if f.c.useConcurrentWrites { + return f.writeAtConcurrent(b, off) + } + + ch := make(chan result, 1) // reusable channel + + chunkSize := f.c.maxPacket + + for written < len(b) { + wb := b[written:] + if len(wb) > chunkSize { + wb = wb[:chunkSize] + } + + n, err := f.writeChunkAt(ch, wb, off+int64(written)) + if n > 0 { + written += n + } + + if err != nil { + return written, err + } + } + + return len(b), nil +} + +// ReadFromWithConcurrency implements ReaderFrom, +// but uses the given concurrency to issue multiple requests at the same time. +// +// Giving a concurrency of less than one will default to the Client’s max concurrency. +// +// Otherwise, the given concurrency will be capped by the Client's max concurrency. +func (f *File) ReadFromWithConcurrency(r io.Reader, concurrency int) (read int64, err error) { + // Split the write into multiple maxPacket sized concurrent writes. + // This allows writes with a suitably large reader + // to transfer data at a much faster rate due to overlapping round trip times. + + cancel := make(chan struct{}) + + type work struct { + b []byte + n int + off int64 + } + workCh := make(chan work) + + type rwErr struct { + off int64 + err error + } + errCh := make(chan rwErr) + + if concurrency > f.c.maxConcurrentRequests || concurrency < 1 { + concurrency = f.c.maxConcurrentRequests + } + + pool := newBufPool(concurrency, f.c.maxPacket) + + // Slice: cut up the Read into any number of buffers of length <= f.c.maxPacket, and at appropriate offsets. + go func() { + defer close(workCh) + + off := f.offset + + for { + b := pool.Get() + + n, err := r.Read(b) + if n > 0 { + read += int64(n) + + select { + case workCh <- work{b, n, off}: + // We need the pool.Put(b) to put the whole slice, not just trunced. + case <-cancel: + return + } + + off += int64(n) + } + + if err != nil { + if err != io.EOF { + errCh <- rwErr{off, err} + } + return + } + } + }() + + var wg sync.WaitGroup + wg.Add(concurrency) + for i := 0; i < concurrency; i++ { + // Map_i: each worker gets work, and does the Write from each buffer to its respective offset. + go func() { + defer wg.Done() + + ch := make(chan result, 1) // reusable channel per mapper. + + for packet := range workCh { + n, err := f.writeChunkAt(ch, packet.b[:packet.n], packet.off) + if err != nil { + // return the offset as the start + how much we wrote before the error. + errCh <- rwErr{packet.off + int64(n), err} + } + pool.Put(packet.b) + } + }() + } + + // Wait for long tail, before closing results. + go func() { + wg.Wait() + close(errCh) + }() + + // Reduce: Collect all the results into a relevant return: the earliest offset to return an error. + firstErr := rwErr{math.MaxInt64, nil} + for rwErr := range errCh { + if rwErr.off <= firstErr.off { + firstErr = rwErr + } + + select { + case <-cancel: + default: + // stop any more work from being distributed. + close(cancel) + } + } + + if firstErr.err != nil { + // firstErr.err != nil if and only if firstErr.off is a valid offset. + // + // firstErr.off will then be the lesser of: + // * the offset of the first error from writing, + // * the last successfully read offset. + // + // This could be less than the last successfully written offset, + // which is the whole reason for the UseConcurrentWrites() ClientOption. + // + // Callers are responsible for truncating any SFTP files to a safe length. + f.offset = firstErr.off + + // ReadFrom is defined to return the read bytes, regardless of any writer errors. + return read, firstErr.err + } + + f.offset += read + return read, nil +} + +// ReadFrom reads data from r until EOF and writes it to the file. The return +// value is the number of bytes read. Any error except io.EOF encountered +// during the read is also returned. +// +// This method is preferred over calling Write multiple times +// to maximise throughput for transferring the entire file, +// especially over high-latency links. +func (f *File) ReadFrom(r io.Reader) (int64, error) { + f.mu.Lock() + defer f.mu.Unlock() + + if f.c.useConcurrentWrites { + var remain int64 + switch r := r.(type) { + case interface{ Len() int }: + remain = int64(r.Len()) + + case interface{ Size() int64 }: + remain = r.Size() + + case *io.LimitedReader: + remain = r.N + + case interface{ Stat() (os.FileInfo, error) }: + info, err := r.Stat() + if err == nil { + remain = info.Size() + } + } + + if remain < 0 { + // We can strongly assert that we want default max concurrency here. + return f.ReadFromWithConcurrency(r, f.c.maxConcurrentRequests) + } + + if remain > int64(f.c.maxPacket) { + // Otherwise, only use concurrency, if it would be at least two packets. + + // This is the best reasonable guess we can make. + concurrency64 := remain/int64(f.c.maxPacket) + 1 + + // We need to cap this value to an `int` size value to avoid overflow on 32-bit machines. + // So, we may as well pre-cap it to `f.c.maxConcurrentRequests`. + if concurrency64 > int64(f.c.maxConcurrentRequests) { + concurrency64 = int64(f.c.maxConcurrentRequests) + } + + return f.ReadFromWithConcurrency(r, int(concurrency64)) + } + } + + ch := make(chan result, 1) // reusable channel + + b := make([]byte, f.c.maxPacket) + + var read int64 + for { + n, err := r.Read(b) + if n < 0 { + panic("sftp.File: reader returned negative count from Read") + } + + if n > 0 { + read += int64(n) + + m, err2 := f.writeChunkAt(ch, b[:n], f.offset) + f.offset += int64(m) + + if err == nil { + err = err2 + } + } + + if err != nil { + if err == io.EOF { + return read, nil // return nil explicitly. + } + + return read, err + } + } +} + +// Seek implements io.Seeker by setting the client offset for the next Read or +// Write. It returns the next offset read. Seeking before or after the end of +// the file is undefined. Seeking relative to the end calls Stat. +func (f *File) Seek(offset int64, whence int) (int64, error) { + f.mu.Lock() + defer f.mu.Unlock() + + switch whence { + case io.SeekStart: + case io.SeekCurrent: + offset += f.offset + case io.SeekEnd: + fi, err := f.Stat() + if err != nil { + return f.offset, err + } + offset += fi.Size() + default: + return f.offset, unimplementedSeekWhence(whence) + } + + if offset < 0 { + return f.offset, os.ErrInvalid + } + + f.offset = offset + return f.offset, nil +} + +// Chown changes the uid/gid of the current file. +func (f *File) Chown(uid, gid int) error { + return f.c.Chown(f.path, uid, gid) +} + +// Chmod changes the permissions of the current file. +// +// See Client.Chmod for details. +func (f *File) Chmod(mode os.FileMode) error { + return f.c.setfstat(f.handle, sshFileXferAttrPermissions, toChmodPerm(mode)) +} + +// Sync requests a flush of the contents of a File to stable storage. +// +// Sync requires the server to support the fsync@openssh.com extension. +func (f *File) Sync() error { + id := f.c.nextID() + typ, data, err := f.c.sendPacket(nil, &sshFxpFsyncPacket{ + ID: id, + Handle: f.handle, + }) + + switch { + case err != nil: + return err + case typ == sshFxpStatus: + return normaliseError(unmarshalStatus(id, data)) + default: + return &unexpectedPacketErr{want: sshFxpStatus, got: typ} + } +} + +// Truncate sets the size of the current file. Although it may be safely assumed +// that if the size is less than its current size it will be truncated to fit, +// the SFTP protocol does not specify what behavior the server should do when setting +// size greater than the current size. +// We send a SSH_FXP_FSETSTAT here since we have a file handle +func (f *File) Truncate(size int64) error { + return f.c.setfstat(f.handle, sshFileXferAttrSize, uint64(size)) +} + +// normaliseError normalises an error into a more standard form that can be +// checked against stdlib errors like io.EOF or os.ErrNotExist. +func normaliseError(err error) error { + switch err := err.(type) { + case *StatusError: + switch err.Code { + case sshFxEOF: + return io.EOF + case sshFxNoSuchFile: + return os.ErrNotExist + case sshFxPermissionDenied: + return os.ErrPermission + case sshFxOk: + return nil + default: + return err + } + default: + return err + } +} + +// flags converts the flags passed to OpenFile into ssh flags. +// Unsupported flags are ignored. +func flags(f int) uint32 { + var out uint32 + switch f & os.O_WRONLY { + case os.O_WRONLY: + out |= sshFxfWrite + case os.O_RDONLY: + out |= sshFxfRead + } + if f&os.O_RDWR == os.O_RDWR { + out |= sshFxfRead | sshFxfWrite + } + if f&os.O_APPEND == os.O_APPEND { + out |= sshFxfAppend + } + if f&os.O_CREATE == os.O_CREATE { + out |= sshFxfCreat + } + if f&os.O_TRUNC == os.O_TRUNC { + out |= sshFxfTrunc + } + if f&os.O_EXCL == os.O_EXCL { + out |= sshFxfExcl + } + return out +} + +// toChmodPerm converts Go permission bits to POSIX permission bits. +// +// This differs from fromFileMode in that we preserve the POSIX versions of +// setuid, setgid and sticky in m, because we've historically supported those +// bits, and we mask off any non-permission bits. +func toChmodPerm(m os.FileMode) (perm uint32) { + const mask = os.ModePerm | s_ISUID | s_ISGID | s_ISVTX + perm = uint32(m & mask) + + if m&os.ModeSetuid != 0 { + perm |= s_ISUID + } + if m&os.ModeSetgid != 0 { + perm |= s_ISGID + } + if m&os.ModeSticky != 0 { + perm |= s_ISVTX + } + + return perm +} |