94 lines
2.4 KiB
Go
94 lines
2.4 KiB
Go
/*
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Copyright IBM Corp. All Rights Reserved.
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SPDX-License-Identifier: Apache-2.0
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*/
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package externalbuilder
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import (
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"archive/tar"
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"compress/gzip"
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"io"
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"os"
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"path/filepath"
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"strings"
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"github.com/pkg/errors"
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)
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// Untar takes a gzip-ed tar archive, and extracts it to dst.
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// It returns an error if the tar contains any files which would escape to a
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// parent of dst, or if the archive contains any files whose type is not
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// a regular file or directory.
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func Untar(buffer io.Reader, dst string) error {
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gzr, err := gzip.NewReader(buffer)
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if err != nil {
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return err
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}
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defer gzr.Close()
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tr := tar.NewReader(gzr)
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for {
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header, err := tr.Next()
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if err == io.EOF {
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return nil
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}
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if err != nil {
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return errors.WithMessage(err, "could not get next tar element")
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}
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if !ValidPath(header.Name) {
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return errors.Errorf("tar contains the absolute or escaping path '%s'", header.Name)
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}
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target := filepath.Join(dst, header.Name)
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switch header.Typeflag {
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case tar.TypeDir:
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if err := os.MkdirAll(target, 0o700); err != nil {
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return errors.WithMessagef(err, "could not create directory '%s'", header.Name)
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}
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case tar.TypeReg:
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if err := os.MkdirAll(filepath.Dir(target), 0o700); err != nil {
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return errors.WithMessagef(err, "could not create directory '%s'", filepath.Dir(header.Name))
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}
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f, err := os.OpenFile(target, os.O_CREATE|os.O_RDWR, os.FileMode(header.Mode))
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if err != nil {
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return errors.WithMessagef(err, "could not create file '%s'", header.Name)
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}
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// copy over contents
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if _, err := io.Copy(f, tr); err != nil {
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return err
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}
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f.Close()
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default:
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return errors.Errorf("invalid file type '%v' contained in archive for file '%s'", header.Typeflag, header.Name)
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}
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}
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}
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// ValidPath checks to see if the path is absolute, or if it is a
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// relative path higher in the tree. In these cases it returns false.
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func ValidPath(uncleanPath string) bool {
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// sanitizedPath will eliminate non-prefix instances of '..', as well
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// as strip './'
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sanitizedPath := filepath.Clean(uncleanPath)
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switch {
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case filepath.IsAbs(sanitizedPath):
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return false
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case strings.HasPrefix(sanitizedPath, ".."+string(filepath.Separator)) || sanitizedPath == "..":
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// Path refers either to the parent, or a directory relative to the parent (but allows ..foo or ... for instance)
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return false
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default:
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// Path appears to be relative without escaping higher
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return true
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}
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}
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