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Rootless extraction and non-writable directories #208

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33 changes: 33 additions & 0 deletions image/manifest.go
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Original file line number Diff line number Diff line change
Expand Up @@ -22,6 +22,7 @@ import (
"compress/gzip"
"encoding/json"
"fmt"
gopath "path"
"io"
"io/ioutil"
"os"
Expand Down Expand Up @@ -229,6 +230,27 @@ loop:
return nil
}


func checkParentDirPerm(parentDir string) (os.FileMode, bool, error) {
altered := false

parentDirInfo, err := os.Stat(parentDir)
if err != nil {
return 0, altered, err
}

parentDirPerm := parentDirInfo.Mode()

/* Check if we will be able to write as user */
if parentDirPerm.Perm() & (1 << (uint(7))) == 0{
os.Chmod(parentDir, parentDirPerm.Perm() | (1 << (uint(7))))
altered = true
}

return parentDirPerm, altered, nil
}


// unpackLayerEntry unpacks a single entry from a layer.
func unpackLayerEntry(dest string, header *tar.Header, reader io.Reader, entries *map[string]bool) (whiteout bool, err error) {
header.Name = filepath.Clean(header.Name)
Expand Down Expand Up @@ -273,6 +295,17 @@ func unpackLayerEntry(dest string, header *tar.Header, reader io.Reader, entries
}
}

parentDir := gopath.Dir(path)
sourceMode, alteredMode, err := checkParentDirPerm(parentDir)

if err != nil {
return false, err
}

if alteredMode {
defer os.Chmod(parentDir, sourceMode)
}

switch header.Typeflag {
case tar.TypeDir:
fi, err := os.Lstat(path)
Expand Down