syscallcompat

Documentation

Overview

Package syscallcompat wraps Linux-specific syscalls.

Index

• Constants
• func Dup3(oldfd int, newfd int, flags int) (err error)
• func EnospcPrealloc(fd int, off int64, len int64) (err error)
• func Faccessat(dirfd int, path string, mode uint32) error
• func Fallocate(fd int, mode uint32, off int64, len int64) (err error)
• func FchmodatNofollow(dirfd int, path string, mode uint32) (err error)
• func Fchownat(dirfd int, path string, uid int, gid int, flags int) (err error)
• func Fgetxattr(fd int, attr string) (val []byte, err error)
• func Flistxattr(fd int) (attrs []string, err error)
• func Fstatat(dirfd int, path string, stat *unix.Stat_t, flags int) (err error)
• func FutimesNano(fd int, a *time.Time, m *time.Time) (err error)
• func IsENOSPC(err error) bool
• func Lgetxattr(path string, attr string) (val []byte, err error)
• func Linkat(olddirfd int, oldpath string, newdirfd int, newpath string, flags int) (err error)
• func Llistxattr(path string) (attrs []string, err error)
• func Mkdirat(dirfd int, path string, mode uint32) (err error)
• func Mknodat(dirfd int, path string, mode uint32, dev int) (err error)
• func OpenDirNofollow(baseDir string, relPath string) (fd int, err error)
• func Openat(dirfd int, path string, flags int, mode uint32) (fd int, err error)
• func Readlinkat(dirfd int, path string) (string, error)
• func Renameat(olddirfd int, oldpath string, newdirfd int, newpath string) (err error)
• func Symlinkat(oldpath string, newdirfd int, newpath string) (err error)
• func Unix2syscall(u unix.Stat_t) syscall.Stat_t
• func Unlinkat(dirfd int, path string, flags int) (err error)
• func UtimesNanoAtNofollow(dirfd int, path string, a *time.Time, m *time.Time) (err error)
• type DirEntry
  • func Getdents(fd int) ([]DirEntry, error)

Constants

const (

	// O_DIRECT means oncached I/O on Linux. No direct equivalent on MacOS and defined
	// to zero there.
	O_DIRECT = syscall.O_DIRECT

	// O_PATH is only defined on Linux
	O_PATH = unix.O_PATH
)

const PATH_MAX = 4096

PATH_MAX is the maximum allowed path length on Linux. It is not defined on Darwin, so we use the Linux value.

const XATTR_BUFSZ = XATTR_SIZE_MAX + 1024

Make the buffer 1kB bigger so we can detect overflows

const XATTR_SIZE_MAX = 65536

Functions

func Dup3

func Dup3(oldfd int, newfd int, flags int) (err error)

Dup3 wraps the Dup3 syscall. We want to use Dup3 rather than Dup2 because Dup2 is not implemented on arm64.

func EnospcPrealloc

func EnospcPrealloc(fd int, off int64, len int64) (err error)

EnospcPrealloc preallocates ciphertext space without changing the file size. This guarantees that we don't run out of space while writing a ciphertext block (that would corrupt the block).

func Faccessat

func Faccessat(dirfd int, path string, mode uint32) error

Faccessat exists both in Linux and in MacOS 10.10+, but the Linux version DOES NOT support any flags. Emulate AT_SYMLINK_NOFOLLOW like glibc does.

func Fallocate

func Fallocate(fd int, mode uint32, off int64, len int64) (err error)

Fallocate wraps the Fallocate syscall.

func FchmodatNofollow

func FchmodatNofollow(dirfd int, path string, mode uint32) (err error)

FchmodatNofollow is like Fchmodat but never follows symlinks.

This should be handled by the AT_SYMLINK_NOFOLLOW flag, but Linux does not implement it, so we have to perform an elaborate dance with O_PATH and /proc/self/fd.

See also: Qemu implemented the same logic as fchmodat_nofollow(): https://git.qemu.org/?p=qemu.git;a=blob;f=hw/9pfs/9p-local.c#l335

func Fchownat

func Fchownat(dirfd int, path string, uid int, gid int, flags int) (err error)

Fchownat syscall.

func Fgetxattr

func Fgetxattr(fd int, attr string) (val []byte, err error)

Fgetxattr is a wrapper around unix.Fgetxattr that handles the buffer sizing.

func Flistxattr

func Flistxattr(fd int) (attrs []string, err error)

Flistxattr is a wrapper for unix.Flistxattr that handles buffer sizing and parsing the returned blob to a string slice.

func Fstatat

func Fstatat(dirfd int, path string, stat *unix.Stat_t, flags int) (err error)

Fstatat syscall.

func FutimesNano

func FutimesNano(fd int, a *time.Time, m *time.Time) (err error)

FutimesNano syscall.

func IsENOSPC

func IsENOSPC(err error) bool

IsENOSPC tries to find out if "err" is a (potentially wrapped) ENOSPC error.

func Lgetxattr

func Lgetxattr(path string, attr string) (val []byte, err error)

Lgetxattr is a wrapper around unix.Lgetxattr that handles the buffer sizing.

func Linkat

func Linkat(olddirfd int, oldpath string, newdirfd int, newpath string, flags int) (err error)

Linkat exists both in Linux and in MacOS 10.10+.

func Llistxattr

func Llistxattr(path string) (attrs []string, err error)

Llistxattr is a wrapper for unix.Llistxattr that handles buffer sizing and parsing the returned blob to a string slice.

func Mkdirat

func Mkdirat(dirfd int, path string, mode uint32) (err error)

Mkdirat syscall.

func Mknodat

func Mknodat(dirfd int, path string, mode uint32, dev int) (err error)

Mknodat wraps the Mknodat syscall.

func OpenDirNofollow

func OpenDirNofollow(baseDir string, relPath string) (fd int, err error)

OpenDirNofollow opens the dir at "relPath" in a way that is secure against symlink attacks. Symlinks that are part of "relPath" are never followed. This function is implemented by walking the directory tree, starting at "baseDir", using the Openat syscall with the O_NOFOLLOW flag. Symlinks that are part of the "baseDir" path are followed.

func Openat

func Openat(dirfd int, path string, flags int, mode uint32) (fd int, err error)

Openat wraps the Openat syscall.

func Readlinkat

func Readlinkat(dirfd int, path string) (string, error)

Readlinkat is a convenience wrapper around unix.Readlinkat() that takes care of buffer sizing. Implemented like os.Readlink().

func Renameat

func Renameat(olddirfd int, oldpath string, newdirfd int, newpath string) (err error)

Renameat wraps the Renameat syscall.

func Symlinkat

func Symlinkat(oldpath string, newdirfd int, newpath string) (err error)

Symlinkat syscall.

func Unix2syscall

func Unix2syscall(u unix.Stat_t) syscall.Stat_t

Unix2syscall converts a unix.Stat_t struct to a syscall.Stat_t struct. A direct cast does not work because the padding is named differently in unix.Stat_t for some reason ("X__unused" in syscall, "_" in unix).

func Unlinkat

func Unlinkat(dirfd int, path string, flags int) (err error)

Unlinkat syscall.

func UtimesNanoAtNofollow

func UtimesNanoAtNofollow(dirfd int, path string, a *time.Time, m *time.Time) (err error)

UtimesNanoAtNofollow is like UtimesNanoAt but never follows symlinks.

Types

type DirEntry

type DirEntry struct {
	Name string
	Mode uint32
}

func Getdents

func Getdents(fd int) ([]DirEntry, error)