*: switch to golang.org/x/sys/unix

Go modules mean adding dependencies is less painful than it was when we
started this project, and we will need some syscalls from unix for
implementing a safe MkdirAll.

Signed-off-by: Aleksa Sarai <cyphar@cyphar.com>

go.mod

@@ -1,3 +1,5 @@
 module github.com/cyphar/filepath-securejoin
 
 go 1.13
+
+require golang.org/x/sys v0.21.0 // indirect

go.sum

@@ -0,0 +1,2 @@
+golang.org/x/sys v0.21.0 h1:rF+pYz3DAGSQAxAu1CbC7catZg4ebC4UIeIhKxBZvws=
+golang.org/x/sys v0.21.0/go.mod h1:/VUhepiaJMQUp4+oa/7Zr1D23ma6VTLIYjOOTFZPUcA=

join.go

@@ -15,7 +15,8 @@ import (
  "os"
  "path/filepath"
  "strings"
- "syscall"
+
+ "golang.org/x/sys/unix"
 )
 
 const maxSymlinkLimit = 255
@@ -26,7 +27,7 @@ const maxSymlinkLimit = 255
 func IsNotExist(err error) bool {
  // Check that it's not actually an ENOTDIR, which in some cases is a more
  // convoluted case of ENOENT (usually involving weird paths).
- return errors.Is(err, os.ErrNotExist) || errors.Is(err, syscall.ENOTDIR) || errors.Is(err, syscall.ENOENT)
+ return errors.Is(err, os.ErrNotExist) || errors.Is(err, unix.ENOTDIR) || errors.Is(err, unix.ENOENT)
 }
 
 // SecureJoinVFS joins the two given path components (similar to Join) except
@@ -97,7 +98,7 @@ func SecureJoinVFS(root, unsafePath string, vfs VFS) (string, error) {
  // to the yet-unparsed path.
  linksWalked++
  if linksWalked > maxSymlinkLimit {
- return "", &os.PathError{Op: "SecureJoin", Path: root + string(filepath.Separator) + unsafePath, Err: syscall.ELOOP}
+ return "", &os.PathError{Op: "SecureJoin", Path: root + string(filepath.Separator) + unsafePath, Err: unix.ELOOP}
  }
 
  dest, err := vfs.Readlink(fullPath)

join_test.go

@@ -10,8 +10,9 @@ import (
  "os"
  "path/filepath"
  "runtime"
- "syscall"
  "testing"
+
+ "golang.org/x/sys/unix"
 )
 
 // TODO: These tests won't work on plan9 because it doesn't have symlinks, and
@@ -197,7 +198,7 @@ func TestSymlinkLoop(t *testing.T) {
  {dir, "/self/././.."},
  } {
  got, err := SecureJoin(test.root, test.unsafe)
- if !errors.Is(err, syscall.ELOOP) {
+ if !errors.Is(err, unix.ELOOP) {
  t.Errorf("securejoin(%q, %q): expected ELOOP, got %q & %v", test.root, test.unsafe, got, err)
  continue
  }
@@ -241,15 +242,15 @@ func TestIsNotExist(t *testing.T) {
  err error
  expected bool
  }{
- {&os.PathError{Op: "test1", Err: syscall.ENOENT}, true},
- {&os.LinkError{Op: "test1", Err: syscall.ENOENT}, true},
- {&os.SyscallError{Syscall: "test1", Err: syscall.ENOENT}, true},
- {&os.PathError{Op: "test2", Err: syscall.ENOTDIR}, true},
- {&os.LinkError{Op: "test2", Err: syscall.ENOTDIR}, true},
- {&os.SyscallError{Syscall: "test2", Err: syscall.ENOTDIR}, true},
- {&os.PathError{Op: "test3", Err: syscall.EACCES}, false},
- {&os.LinkError{Op: "test3", Err: syscall.EACCES}, false},
- {&os.SyscallError{Syscall: "test3", Err: syscall.EACCES}, false},
+ {&os.PathError{Op: "test1", Err: unix.ENOENT}, true},
+ {&os.LinkError{Op: "test1", Err: unix.ENOENT}, true},
+ {&os.SyscallError{Syscall: "test1", Err: unix.ENOENT}, true},
+ {&os.PathError{Op: "test2", Err: unix.ENOTDIR}, true},
+ {&os.LinkError{Op: "test2", Err: unix.ENOTDIR}, true},
+ {&os.SyscallError{Syscall: "test2", Err: unix.ENOTDIR}, true},
+ {&os.PathError{Op: "test3", Err: unix.EACCES}, false},
+ {&os.LinkError{Op: "test3", Err: unix.EACCES}, false},
+ {&os.SyscallError{Syscall: "test3", Err: unix.EACCES}, false},
  {errors.New("not a proper error"), false},
  } {
  got := IsNotExist(test.err)