github.com/kaisenlinux/docker@v0.0.0-20230510090727-ea55db55fac7/engine/pkg/chrootarchive/archive.go (about)

     1  package chrootarchive // import "github.com/docker/docker/pkg/chrootarchive"
     2  
     3  import (
     4  	"fmt"
     5  	"io"
     6  	"net"
     7  	"os"
     8  	"os/user"
     9  	"path/filepath"
    10  
    11  	"github.com/docker/docker/pkg/archive"
    12  	"github.com/docker/docker/pkg/idtools"
    13  )
    14  
    15  func init() {
    16  	// initialize nss libraries in Glibc so that the dynamic libraries are loaded in the host
    17  	// environment not in the chroot from untrusted files.
    18  	_, _ = user.Lookup("docker")
    19  	_, _ = net.LookupHost("localhost")
    20  }
    21  
    22  // NewArchiver returns a new Archiver which uses chrootarchive.Untar
    23  func NewArchiver(idMapping *idtools.IdentityMapping) *archive.Archiver {
    24  	if idMapping == nil {
    25  		idMapping = &idtools.IdentityMapping{}
    26  	}
    27  	return &archive.Archiver{
    28  		Untar:     Untar,
    29  		IDMapping: idMapping,
    30  	}
    31  }
    32  
    33  // Untar reads a stream of bytes from `archive`, parses it as a tar archive,
    34  // and unpacks it into the directory at `dest`.
    35  // The archive may be compressed with one of the following algorithms:
    36  // identity (uncompressed), gzip, bzip2, xz.
    37  func Untar(tarArchive io.Reader, dest string, options *archive.TarOptions) error {
    38  	return untarHandler(tarArchive, dest, options, true, dest)
    39  }
    40  
    41  // UntarWithRoot is the same as `Untar`, but allows you to pass in a root directory
    42  // The root directory is the directory that will be chrooted to.
    43  // `dest` must be a path within `root`, if it is not an error will be returned.
    44  //
    45  // `root` should set to a directory which is not controlled by any potentially
    46  // malicious process.
    47  //
    48  // This should be used to prevent a potential attacker from manipulating `dest`
    49  // such that it would provide access to files outside of `dest` through things
    50  // like symlinks. Normally `ResolveSymlinksInScope` would handle this, however
    51  // sanitizing symlinks in this manner is inherrently racey:
    52  // ref: CVE-2018-15664
    53  func UntarWithRoot(tarArchive io.Reader, dest string, options *archive.TarOptions, root string) error {
    54  	return untarHandler(tarArchive, dest, options, true, root)
    55  }
    56  
    57  // UntarUncompressed reads a stream of bytes from `archive`, parses it as a tar archive,
    58  // and unpacks it into the directory at `dest`.
    59  // The archive must be an uncompressed stream.
    60  func UntarUncompressed(tarArchive io.Reader, dest string, options *archive.TarOptions) error {
    61  	return untarHandler(tarArchive, dest, options, false, dest)
    62  }
    63  
    64  // Handler for teasing out the automatic decompression
    65  func untarHandler(tarArchive io.Reader, dest string, options *archive.TarOptions, decompress bool, root string) error {
    66  	if tarArchive == nil {
    67  		return fmt.Errorf("Empty archive")
    68  	}
    69  	if options == nil {
    70  		options = &archive.TarOptions{}
    71  	}
    72  	if options.ExcludePatterns == nil {
    73  		options.ExcludePatterns = []string{}
    74  	}
    75  
    76  	// If dest is inside a root then directory is created within chroot by extractor.
    77  	// This case is only currently used by cp.
    78  	if dest == root {
    79  		idMapping := idtools.NewIDMappingsFromMaps(options.UIDMaps, options.GIDMaps)
    80  		rootIDs := idMapping.RootPair()
    81  
    82  		dest = filepath.Clean(dest)
    83  		if _, err := os.Stat(dest); os.IsNotExist(err) {
    84  			if err := idtools.MkdirAllAndChownNew(dest, 0755, rootIDs); err != nil {
    85  				return err
    86  			}
    87  		}
    88  	}
    89  
    90  	r := io.NopCloser(tarArchive)
    91  	if decompress {
    92  		decompressedArchive, err := archive.DecompressStream(tarArchive)
    93  		if err != nil {
    94  			return err
    95  		}
    96  		defer decompressedArchive.Close()
    97  		r = decompressedArchive
    98  	}
    99  
   100  	return invokeUnpack(r, dest, options, root)
   101  }
   102  
   103  // Tar tars the requested path while chrooted to the specified root.
   104  func Tar(srcPath string, options *archive.TarOptions, root string) (io.ReadCloser, error) {
   105  	if options == nil {
   106  		options = &archive.TarOptions{}
   107  	}
   108  	return invokePack(srcPath, options, root)
   109  }