Privatae
49 lines
1.2 KiB
Go
49 lines
1.2 KiB
Go
//go:build linux
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package main
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import (
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"errors"
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"os"
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"strings"
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"golang.org/x/sys/unix"
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)
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// dcnNoLinkStat describes the directory at p (absolute, clean) reached one
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// component at a time with O_NOFOLLOW, so a link anywhere in the path fails
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// instead of being followed. O_PATH: a component the bastion may traverse but
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// not list (a home at 0711) still opens.
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func dcnNoLinkStat(p string) (os.FileInfo, error) {
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if !strings.HasPrefix(p, "/") {
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return nil, errors.New("not an absolute path")
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}
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fd, err := unix.Open("/", unix.O_PATH|unix.O_DIRECTORY|unix.O_CLOEXEC, 0)
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if err != nil {
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return nil, err
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}
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for _, c := range strings.Split(p, "/") {
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if c == "" {
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continue
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}
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if c == "." || c == ".." {
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_ = unix.Close(fd)
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return nil, errors.New("not a clean path")
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}
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next, err := unix.Openat(fd, c, unix.O_PATH|unix.O_NOFOLLOW|unix.O_DIRECTORY|unix.O_CLOEXEC, 0)
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_ = unix.Close(fd)
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if err != nil {
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return nil, err
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}
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var st unix.Stat_t
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if err := unix.Fstat(next, &st); err != nil || st.Mode&unix.S_IFMT != unix.S_IFDIR {
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_ = unix.Close(next)
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return nil, errors.New("a component is not a directory")
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}
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fd = next
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}
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f := os.NewFile(uintptr(fd), p)
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defer f.Close()
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return f.Stat()
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}
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