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package utils
import (
"encoding/binary"
"encoding/json"
"fmt"
"io"
"os"
"path/filepath"
"strconv"
"strings"
"unsafe"
securejoin "github.com/cyphar/filepath-securejoin"
"golang.org/x/sys/unix"
)
const (
exitSignalOffset = 128
)
// NativeEndian is the native byte order of the host system.
var NativeEndian binary.ByteOrder
func init() {
// Copied from <golang.org/x/net/internal/socket/sys.go>.
i := uint32(1)
b := (*[4]byte)(unsafe.Pointer(&i))
if b[0] == 1 {
NativeEndian = binary.LittleEndian
} else {
NativeEndian = binary.BigEndian
}
}
// ExitStatus returns the correct exit status for a process based on if it
// was signaled or exited cleanly
func ExitStatus(status unix.WaitStatus) int {
if status.Signaled() {
return exitSignalOffset + int(status.Signal())
}
return status.ExitStatus()
}
// WriteJSON writes the provided struct v to w using standard json marshaling
func WriteJSON(w io.Writer, v interface{}) error {
data, err := json.Marshal(v)
if err != nil {
return err
}
_, err = w.Write(data)
return err
}
// CleanPath makes a path safe for use with filepath.Join. This is done by not
// only cleaning the path, but also (if the path is relative) adding a leading
// '/' and cleaning it (then removing the leading '/'). This ensures that a
// path resulting from prepending another path will always resolve to lexically
// be a subdirectory of the prefixed path. This is all done lexically, so paths
// that include symlinks won't be safe as a result of using CleanPath.
func CleanPath(path string) string {
// Deal with empty strings nicely.
if path == "" {
return ""
}
// Ensure that all paths are cleaned (especially problematic ones like
// "/../../../../../" which can cause lots of issues).
path = filepath.Clean(path)
// If the path isn't absolute, we need to do more processing to fix paths
// such as "../../../../<etc>/some/path". We also shouldn't convert absolute
// paths to relative ones.
if !filepath.IsAbs(path) {
path = filepath.Clean(string(os.PathSeparator) + path)
// This can't fail, as (by definition) all paths are relative to root.
path, _ = filepath.Rel(string(os.PathSeparator), path)
}
// Clean the path again for good measure.
return filepath.Clean(path)
}
// stripRoot returns the passed path, stripping the root path if it was
// (lexicially) inside it. Note that both passed paths will always be treated
// as absolute, and the returned path will also always be absolute. In
// addition, the paths are cleaned before stripping the root.
func stripRoot(root, path string) string {
// Make the paths clean and absolute.
root, path = CleanPath("/"+root), CleanPath("/"+path)
switch {
case path == root:
path = "/"
case root == "/":
// do nothing
case strings.HasPrefix(path, root+"/"):
path = strings.TrimPrefix(path, root+"/")
}
return CleanPath("/" + path)
}
// WithProcfd runs the passed closure with a procfd path (/proc/self/fd/...)
// corresponding to the unsafePath resolved within the root. Before passing the
// fd, this path is verified to have been inside the root -- so operating on it
// through the passed fdpath should be safe. Do not access this path through
// the original path strings, and do not attempt to use the pathname outside of
// the passed closure (the file handle will be freed once the closure returns).
func WithProcfd(root, unsafePath string, fn func(procfd string) error) error {
// Remove the root then forcefully resolve inside the root.
unsafePath = stripRoot(root, unsafePath)
path, err := securejoin.SecureJoin(root, unsafePath)
if err != nil {
return fmt.Errorf("resolving path inside rootfs failed: %w", err)
}
// Open the target path.
fh, err := os.OpenFile(path, unix.O_PATH|unix.O_CLOEXEC, 0)
if err != nil {
return fmt.Errorf("open o_path procfd: %w", err)
}
defer fh.Close()
// Double-check the path is the one we expected.
procfd := "/proc/self/fd/" + strconv.Itoa(int(fh.Fd()))
if realpath, err := os.Readlink(procfd); err != nil {
return fmt.Errorf("procfd verification failed: %w", err)
} else if realpath != path {
return fmt.Errorf("possibly malicious path detected -- refusing to operate on %s", realpath)
}
// Run the closure.
return fn(procfd)
}
// SearchLabels searches a list of key-value pairs for the provided key and
// returns the corresponding value. The pairs must be separated with '='.
func SearchLabels(labels []string, query string) string {
for _, l := range labels {
parts := strings.SplitN(l, "=", 2)
if len(parts) < 2 {
continue
}
if parts[0] == query {
return parts[1]
}
}
return ""
}
// Annotations returns the bundle path and user defined annotations from the
// libcontainer state. We need to remove the bundle because that is a label
// added by libcontainer.
func Annotations(labels []string) (bundle string, userAnnotations map[string]string) {
userAnnotations = make(map[string]string)
for _, l := range labels {
parts := strings.SplitN(l, "=", 2)
if len(parts) < 2 {
continue
}
if parts[0] == "bundle" {
bundle = parts[1]
} else {
userAnnotations[parts[0]] = parts[1]
}
}
return
}
|
