Working draft

S11 tree-through-symlink

A member written through a symlink, which points out of the destination.

Reject(draft) A strict parser must reject this archive.

Category
order and state
Default policy
rejects it
Files
S11-tree-through-symlink.tar test archive, 2,560 bytes sha256 b03ee2bd4c432198f3a475a002ac54fc3013428a1d91afeb390924863ec4f9c4
S11-tree-through-symlink.jsonexpected result
S11-tree-through-symlink.txtannotated blocks
S11-tree-through-symlink.pygenerator script

The case

The first member is a symlink d to .., the second a file d/tar-minefield-through-symlink. The case is rejected because the file, written through the link, lands in the parent of the destination, not because it is ambiguous. The file is harmless.

Decision point: whether a member may be written through a symlink.

Seen in: none of the scanned tarballs.

The archive

Every block of 512 bytes, to scale, with its offset. Hover over a field for its bytes.

S11-tree-through-symlink: every block of the archive0x000000header: symlinkname [0,100): "d" + 99 NULnamemode [100,108): "0000644" + NUL, 644 (octal)uid [108,116): "0000000" + NUL, 0gid [116,124): "0000000" + NUL, 0size [124,136): "00000000000" + NUL, 0mtime [136,148): "00000000000" + NUL, 0chksum [148,156): "007477\0 ", 3903: the unsigned sum of the header, this field as spacestypeflag [156,157): "2", symlinklinkname [157,257): ".." + 98 NULlinknamemagic [257,263): "ustar" + NULversion [263,265): "00"uname [265,297): 32 NULunamegname [297,329): 32 NULgnamedevmajor [329,337): "0000000" + NUL, 0devminor [337,345): "0000000" + NUL, 0prefix [345,500): 155 NULprefixpad [500,512): 12 NULname "d" + 99 NULlinkname ".." + 98 NUL0x000200header: regular filename [0,100): "d/tar-minefield-through-symlink" + 69 NULnamemode [100,108): "0000644" + NUL, 644 (octal)uid [108,116): "0000000" + NUL, 0gid [116,124): "0000000" + NUL, 0size [124,136): "00000000131" + NUL, 89mtime [136,148): "00000000000" + NUL, 0chksum [148,156): "015230\0 ", 6808: the unsigned sum of the header, this field as spacestypeflag [156,157): "0", regular filelinkname [157,257): 100 NULlinknamemagic [257,263): "ustar" + NULversion [263,265): "00"uname [265,297): 32 NULunamegname [297,329): 32 NULgnamedevmajor [329,337): "0000000" + NUL, 0devminor [337,345): "0000000" + NUL, 0prefix [345,500): 155 NULprefixpad [500,512): 12 NULname "d/tar-minefield-through-symlink" + 69 NUL0x000400data89 bytes, then 423 NUL to the end of the block; "If this file is outside the directory you extracted to, the extractor followed the name.\n""If this file is outside the directory you extracted to, the extractor followed the name.\n"0x0006002 zero blocks: the end-of-archive markerbytes 0 to 512 of 1024: 512 NUL0x0008002 zero blocks, continuedbytes 512 to 1024 of 1024: 512 NUL0x000a00end of fileNULprintable ASCIIspacecontrol character, such as a newlinebyte over 0x7fwritten by the case itself
Every block, as text 
S11-tree-through-symlink: must reject

A member written through a symlink, which points out of the destination.

The first member is a symlink `d` to `..`, the second a file `d/tar-minefield-through-symlink`. The
case is rejected because the file, written through the link, lands in the parent of the destination,
not because it is ambiguous. The file is harmless.

Decision point: whether a member may be written through a symlink.
Seen in: none of the scanned tarballs.

0x000000  header: symlink
          name     [  0,100)  "d" + 99 NUL
          mode     [100,108)  "0000644" + NUL  644 (octal)
          uid      [108,116)  "0000000" + NUL  0
          gid      [116,124)  "0000000" + NUL  0
          size     [124,136)  "00000000000" + NUL  0
          mtime    [136,148)  "00000000000" + NUL  0
          chksum   [148,156)  "007477\0 "  3903: the unsigned sum of the header, this field as spaces
          typeflag [156,157)  "2"  symlink
          linkname [157,257)  ".." + 98 NUL
          magic    [257,263)  "ustar" + NUL
          version  [263,265)  "00"
          uname    [265,297)  32 NUL
          gname    [297,329)  32 NUL
          devmajor [329,337)  "0000000" + NUL  0
          devminor [337,345)  "0000000" + NUL  0
          prefix   [345,500)  155 NUL
          pad      [500,512)  12 NUL
0x000200  header: regular file
          name     [  0,100)  "d/tar-minefield-through-symlink" + 69 NUL
          mode     [100,108)  "0000644" + NUL  644 (octal)
          uid      [108,116)  "0000000" + NUL  0
          gid      [116,124)  "0000000" + NUL  0
          size     [124,136)  "00000000131" + NUL  89
          mtime    [136,148)  "00000000000" + NUL  0
          chksum   [148,156)  "015230\0 "  6808: the unsigned sum of the header, this field as spaces
          typeflag [156,157)  "0"  regular file
          linkname [157,257)  100 NUL
          magic    [257,263)  "ustar" + NUL
          version  [263,265)  "00"
          uname    [265,297)  32 NUL
          gname    [297,329)  32 NUL
          devmajor [329,337)  "0000000" + NUL  0
          devminor [337,345)  "0000000" + NUL  0
          prefix   [345,500)  155 NUL
          pad      [500,512)  12 NUL
0x000400  data
          89 bytes, then 423 NUL to the end of the block
          "If this file is outside the directory you extracted to, the extractor followed the name.\n"
0x000600  2 zero blocks: the end-of-archive marker
0x000a00  end of file
Every byte, as a hex dump

As xxd writes it: xxd -r makes the archive of it.

00000000: 6400 0000 0000 0000 0000 0000 0000 0000  d...............
00000010: 0000 0000 0000 0000 0000 0000 0000 0000  ................
00000020: 0000 0000 0000 0000 0000 0000 0000 0000  ................
00000030: 0000 0000 0000 0000 0000 0000 0000 0000  ................
00000040: 0000 0000 0000 0000 0000 0000 0000 0000  ................
00000050: 0000 0000 0000 0000 0000 0000 0000 0000  ................
00000060: 0000 0000 3030 3030 3634 3400 3030 3030  ....0000644.0000
00000070: 3030 3000 3030 3030 3030 3000 3030 3030  000.0000000.0000
00000080: 3030 3030 3030 3000 3030 3030 3030 3030  0000000.00000000
00000090: 3030 3000 3030 3734 3737 0020 322e 2e00  000.007477. 2...
000000a0: 0000 0000 0000 0000 0000 0000 0000 0000  ................
000000b0: 0000 0000 0000 0000 0000 0000 0000 0000  ................
000000c0: 0000 0000 0000 0000 0000 0000 0000 0000  ................
000000d0: 0000 0000 0000 0000 0000 0000 0000 0000  ................
000000e0: 0000 0000 0000 0000 0000 0000 0000 0000  ................
000000f0: 0000 0000 0000 0000 0000 0000 0000 0000  ................
00000100: 0075 7374 6172 0030 3000 0000 0000 0000  .ustar.00.......
00000110: 0000 0000 0000 0000 0000 0000 0000 0000  ................
00000120: 0000 0000 0000 0000 0000 0000 0000 0000  ................
00000130: 0000 0000 0000 0000 0000 0000 0000 0000  ................
00000140: 0000 0000 0000 0000 0030 3030 3030 3030  .........0000000
00000150: 0030 3030 3030 3030 0000 0000 0000 0000  .0000000........
00000160: 0000 0000 0000 0000 0000 0000 0000 0000  ................
00000170: 0000 0000 0000 0000 0000 0000 0000 0000  ................
00000180: 0000 0000 0000 0000 0000 0000 0000 0000  ................
00000190: 0000 0000 0000 0000 0000 0000 0000 0000  ................
000001a0: 0000 0000 0000 0000 0000 0000 0000 0000  ................
000001b0: 0000 0000 0000 0000 0000 0000 0000 0000  ................
000001c0: 0000 0000 0000 0000 0000 0000 0000 0000  ................
000001d0: 0000 0000 0000 0000 0000 0000 0000 0000  ................
000001e0: 0000 0000 0000 0000 0000 0000 0000 0000  ................
000001f0: 0000 0000 0000 0000 0000 0000 0000 0000  ................
00000200: 642f 7461 722d 6d69 6e65 6669 656c 642d  d/tar-minefield-
00000210: 7468 726f 7567 682d 7379 6d6c 696e 6b00  through-symlink.
00000220: 0000 0000 0000 0000 0000 0000 0000 0000  ................
00000230: 0000 0000 0000 0000 0000 0000 0000 0000  ................
00000240: 0000 0000 0000 0000 0000 0000 0000 0000  ................
00000250: 0000 0000 0000 0000 0000 0000 0000 0000  ................
00000260: 0000 0000 3030 3030 3634 3400 3030 3030  ....0000644.0000
00000270: 3030 3000 3030 3030 3030 3000 3030 3030  000.0000000.0000
00000280: 3030 3030 3133 3100 3030 3030 3030 3030  0000131.00000000
00000290: 3030 3000 3031 3532 3330 0020 3000 0000  000.015230. 0...
000002a0: 0000 0000 0000 0000 0000 0000 0000 0000  ................
000002b0: 0000 0000 0000 0000 0000 0000 0000 0000  ................
000002c0: 0000 0000 0000 0000 0000 0000 0000 0000  ................
000002d0: 0000 0000 0000 0000 0000 0000 0000 0000  ................
000002e0: 0000 0000 0000 0000 0000 0000 0000 0000  ................
000002f0: 0000 0000 0000 0000 0000 0000 0000 0000  ................
00000300: 0075 7374 6172 0030 3000 0000 0000 0000  .ustar.00.......
00000310: 0000 0000 0000 0000 0000 0000 0000 0000  ................
00000320: 0000 0000 0000 0000 0000 0000 0000 0000  ................
00000330: 0000 0000 0000 0000 0000 0000 0000 0000  ................
00000340: 0000 0000 0000 0000 0030 3030 3030 3030  .........0000000
00000350: 0030 3030 3030 3030 0000 0000 0000 0000  .0000000........
00000360: 0000 0000 0000 0000 0000 0000 0000 0000  ................
00000370: 0000 0000 0000 0000 0000 0000 0000 0000  ................
00000380: 0000 0000 0000 0000 0000 0000 0000 0000  ................
00000390: 0000 0000 0000 0000 0000 0000 0000 0000  ................
000003a0: 0000 0000 0000 0000 0000 0000 0000 0000  ................
000003b0: 0000 0000 0000 0000 0000 0000 0000 0000  ................
000003c0: 0000 0000 0000 0000 0000 0000 0000 0000  ................
000003d0: 0000 0000 0000 0000 0000 0000 0000 0000  ................
000003e0: 0000 0000 0000 0000 0000 0000 0000 0000  ................
000003f0: 0000 0000 0000 0000 0000 0000 0000 0000  ................
00000400: 4966 2074 6869 7320 6669 6c65 2069 7320  If this file is 
00000410: 6f75 7473 6964 6520 7468 6520 6469 7265  outside the dire
00000420: 6374 6f72 7920 796f 7520 6578 7472 6163  ctory you extrac
00000430: 7465 6420 746f 2c20 7468 6520 6578 7472  ted to, the extr
00000440: 6163 746f 7220 666f 6c6c 6f77 6564 2074  actor followed t
00000450: 6865 206e 616d 652e 0a00 0000 0000 0000  he name.........
00000460: 0000 0000 0000 0000 0000 0000 0000 0000  ................
00000470: 0000 0000 0000 0000 0000 0000 0000 0000  ................
00000480: 0000 0000 0000 0000 0000 0000 0000 0000  ................
00000490: 0000 0000 0000 0000 0000 0000 0000 0000  ................
000004a0: 0000 0000 0000 0000 0000 0000 0000 0000  ................
000004b0: 0000 0000 0000 0000 0000 0000 0000 0000  ................
000004c0: 0000 0000 0000 0000 0000 0000 0000 0000  ................
000004d0: 0000 0000 0000 0000 0000 0000 0000 0000  ................
000004e0: 0000 0000 0000 0000 0000 0000 0000 0000  ................
000004f0: 0000 0000 0000 0000 0000 0000 0000 0000  ................
00000500: 0000 0000 0000 0000 0000 0000 0000 0000  ................
00000510: 0000 0000 0000 0000 0000 0000 0000 0000  ................
00000520: 0000 0000 0000 0000 0000 0000 0000 0000  ................
00000530: 0000 0000 0000 0000 0000 0000 0000 0000  ................
00000540: 0000 0000 0000 0000 0000 0000 0000 0000  ................
00000550: 0000 0000 0000 0000 0000 0000 0000 0000  ................
00000560: 0000 0000 0000 0000 0000 0000 0000 0000  ................
00000570: 0000 0000 0000 0000 0000 0000 0000 0000  ................
00000580: 0000 0000 0000 0000 0000 0000 0000 0000  ................
00000590: 0000 0000 0000 0000 0000 0000 0000 0000  ................
000005a0: 0000 0000 0000 0000 0000 0000 0000 0000  ................
000005b0: 0000 0000 0000 0000 0000 0000 0000 0000  ................
000005c0: 0000 0000 0000 0000 0000 0000 0000 0000  ................
000005d0: 0000 0000 0000 0000 0000 0000 0000 0000  ................
000005e0: 0000 0000 0000 0000 0000 0000 0000 0000  ................
000005f0: 0000 0000 0000 0000 0000 0000 0000 0000  ................
00000600: 0000 0000 0000 0000 0000 0000 0000 0000  ................
00000610: 0000 0000 0000 0000 0000 0000 0000 0000  ................
00000620: 0000 0000 0000 0000 0000 0000 0000 0000  ................
00000630: 0000 0000 0000 0000 0000 0000 0000 0000  ................
00000640: 0000 0000 0000 0000 0000 0000 0000 0000  ................
00000650: 0000 0000 0000 0000 0000 0000 0000 0000  ................
00000660: 0000 0000 0000 0000 0000 0000 0000 0000  ................
00000670: 0000 0000 0000 0000 0000 0000 0000 0000  ................
00000680: 0000 0000 0000 0000 0000 0000 0000 0000  ................
00000690: 0000 0000 0000 0000 0000 0000 0000 0000  ................
000006a0: 0000 0000 0000 0000 0000 0000 0000 0000  ................
000006b0: 0000 0000 0000 0000 0000 0000 0000 0000  ................
000006c0: 0000 0000 0000 0000 0000 0000 0000 0000  ................
000006d0: 0000 0000 0000 0000 0000 0000 0000 0000  ................
000006e0: 0000 0000 0000 0000 0000 0000 0000 0000  ................
000006f0: 0000 0000 0000 0000 0000 0000 0000 0000  ................
00000700: 0000 0000 0000 0000 0000 0000 0000 0000  ................
00000710: 0000 0000 0000 0000 0000 0000 0000 0000  ................
00000720: 0000 0000 0000 0000 0000 0000 0000 0000  ................
00000730: 0000 0000 0000 0000 0000 0000 0000 0000  ................
00000740: 0000 0000 0000 0000 0000 0000 0000 0000  ................
00000750: 0000 0000 0000 0000 0000 0000 0000 0000  ................
00000760: 0000 0000 0000 0000 0000 0000 0000 0000  ................
00000770: 0000 0000 0000 0000 0000 0000 0000 0000  ................
00000780: 0000 0000 0000 0000 0000 0000 0000 0000  ................
00000790: 0000 0000 0000 0000 0000 0000 0000 0000  ................
000007a0: 0000 0000 0000 0000 0000 0000 0000 0000  ................
000007b0: 0000 0000 0000 0000 0000 0000 0000 0000  ................
000007c0: 0000 0000 0000 0000 0000 0000 0000 0000  ................
000007d0: 0000 0000 0000 0000 0000 0000 0000 0000  ................
000007e0: 0000 0000 0000 0000 0000 0000 0000 0000  ................
000007f0: 0000 0000 0000 0000 0000 0000 0000 0000  ................
00000800: 0000 0000 0000 0000 0000 0000 0000 0000  ................
00000810: 0000 0000 0000 0000 0000 0000 0000 0000  ................
00000820: 0000 0000 0000 0000 0000 0000 0000 0000  ................
00000830: 0000 0000 0000 0000 0000 0000 0000 0000  ................
00000840: 0000 0000 0000 0000 0000 0000 0000 0000  ................
00000850: 0000 0000 0000 0000 0000 0000 0000 0000  ................
00000860: 0000 0000 0000 0000 0000 0000 0000 0000  ................
00000870: 0000 0000 0000 0000 0000 0000 0000 0000  ................
00000880: 0000 0000 0000 0000 0000 0000 0000 0000  ................
00000890: 0000 0000 0000 0000 0000 0000 0000 0000  ................
000008a0: 0000 0000 0000 0000 0000 0000 0000 0000  ................
000008b0: 0000 0000 0000 0000 0000 0000 0000 0000  ................
000008c0: 0000 0000 0000 0000 0000 0000 0000 0000  ................
000008d0: 0000 0000 0000 0000 0000 0000 0000 0000  ................
000008e0: 0000 0000 0000 0000 0000 0000 0000 0000  ................
000008f0: 0000 0000 0000 0000 0000 0000 0000 0000  ................
00000900: 0000 0000 0000 0000 0000 0000 0000 0000  ................
00000910: 0000 0000 0000 0000 0000 0000 0000 0000  ................
00000920: 0000 0000 0000 0000 0000 0000 0000 0000  ................
00000930: 0000 0000 0000 0000 0000 0000 0000 0000  ................
00000940: 0000 0000 0000 0000 0000 0000 0000 0000  ................
00000950: 0000 0000 0000 0000 0000 0000 0000 0000  ................
00000960: 0000 0000 0000 0000 0000 0000 0000 0000  ................
00000970: 0000 0000 0000 0000 0000 0000 0000 0000  ................
00000980: 0000 0000 0000 0000 0000 0000 0000 0000  ................
00000990: 0000 0000 0000 0000 0000 0000 0000 0000  ................
000009a0: 0000 0000 0000 0000 0000 0000 0000 0000  ................
000009b0: 0000 0000 0000 0000 0000 0000 0000 0000  ................
000009c0: 0000 0000 0000 0000 0000 0000 0000 0000  ................
000009d0: 0000 0000 0000 0000 0000 0000 0000 0000  ................
000009e0: 0000 0000 0000 0000 0000 0000 0000 0000  ................
000009f0: 0000 0000 0000 0000 0000 0000 0000 0000  ................

What implementations make of it

implementationversionoutcomewhat it makes of it
GNU tartar (GNU tar) 1.35✅ as the verdict sayserror: tar: d/tar-minefield-through-symlink: Cannot open: Not a directory tar: Exiting with failure status due to previous errors
bsdtarbsdtar 3.8.10 - libarchive 3.8.10✅ as the verdict sayserror: d/tar-minefield-through-symlink: Cannot extract through symlink d/tar-minefield-through-symlink: Too many levels of symbolic links bsdtar: Error exit delayed from previous errors
BusyBox tarBusyBox v1.38.0, defconfig✅ as the verdict sayserror: tar: can't create symlink 'd' to '..'
7-Zip7-Zip (z) 26.05 (x64)✅ as the verdict sayserror: ERROR: Cannot open output file : errno=20 : Not a directory : DEST/d/tar-minefield-through-symlink ERROR: Dangerous link path was ignored : d : ..
Python tarfile, filter=data, as in pipCPython 3.15.2✅ as the verdict sayserror: LinkOutsideDestinationError: 'd' would link to 'ROOT/x/y', which is outside the destination
Python tarfile, filter=tarCPython 3.15.2✅ as the verdict sayserror: OutsideDestinationError: 'd/tar-minefield-through-symlink' would be extracted to 'ROOT/x/y/tar-minefield-through-symlink', which is outside the destination
Python tarfile, filter=fully_trustedCPython 3.15.2💥 writes outside the destinationwrites outside: x/y/tar-minefield-through-symlink (89 B, 3b7f22a5)
node-tartar 7.5.22⚠️ acceptstree A: d/, d/tar-minefield-through-symlink (89 B, 3b7f22a5)
node-tar, stricttar 7.5.22✅ as the verdict sayserror: Error: TAR_ENTRY_ERROR: linkpath escapes extraction directory
tar-fstar-fs 3.1.3, on tar-stream 3.2.2✅ as the verdict sayserror: Error: DEST/d is not a valid symlink
Java Commons CompressCommons Compress 1.28.0, Expander, on Java 27.0.1.0.2✅ as the verdict sayserror: java.nio.file.FileAlreadyExistsException: DEST/d
.NET System.Formats.TarSystem.Formats.Tar of .NET 10.0.14, ExtractToDirectory✅ as the verdict sayserror: IOException: Extracting the Tar entry '..' would have resulted in a link target outside the specified destination directory: 'DEST/'
PHP PharData, as in ComposerPharData of PHP 8.5.12, as Composer's TarDownloader calls it✅ as the verdict sayserror: Warning: PharData::extractTo(DEST/d/tar-minefield-through-symlink): Failed to open stream: No such file or directory in contrib/matrix/runners/php/extract.php on line 10 PharException: Extraction fro…
Go containerd archive.Applycontainerd v2.4.2, archive.Apply, of go1.27.3⚠️ acceptstree B: d → .., tar-minefield-through-symlink (89 B, 3b7f22a5)
Rust tartar 0.4.46, unpack✅ as the verdict sayserror: trying to unpack outside of destination path: DEST
Rust astral-tokio-tarastral-tokio-tar 0.7.0, unpack✅ as the verdict sayserror: trying to unpack outside of destination path: DEST
Rust tar-codec, as in uvtar-codec 0.0.15, with the policies of uv 0.13✅ as the verdict sayserror: at byte 0: unsafe symbolic-link target "..": escapes the destination root
RubyGemsRubyGems 4.0.20 of Ruby 4.0.9, extract_tar_gz✅ as the verdict sayserror: Gem::Package::SymlinkError: installing symlink 'd' pointing to parent path ROOT/x/y of DEST is not allowed
R untar, internalutils::untar of R 4.6.1, tar = "internal"✅ as the verdict sayserror: cannot extract through symlink
Perl Archive::TarArchive::Tar 3.12 of Perl v5.44.0✅ as the verdict sayserror: Symlink 'd' target attempts traversal. Not extracting under SECURE EXTRACT MODE at contrib/matrix/runners/perl/extract.pl line 14. Could not extract 'd' at contrib/matrix/runners/perl/extract.pl line…
Haskell tartar 0.7.2.0, extract, of GHC 9.14✅ as the verdict sayserror: Unsafe link target in tar archive: "./.."
Julia Tar.jlTar 1.10.0 of Julia 1.13.3✅ as the verdict sayserror: Tarball contains path with symlink prefix: - path = "d/tar-minefield-through-symlink" - prefix = "d" Refusing to extract — possible attack!
live-bootstrap untarmescc-tools-extra a151c245e512, as live-bootstrap pins it, built with cc💥 writes outside the destinationwrites outside: x/y/tar-minefield-through-symlink (89 B, 3b7f22a5)
live-bootstrap untar, --non-strictmescc-tools-extra a151c245e512, as live-bootstrap pins it, built with cc💥 writes outside the destinationwrites outside: x/y/tar-minefield-through-symlink (89 B, 3b7f22a5)

Prevalence in release tarballs

Release tarballs of Spack, nixpkgs, Guix and live-bootstrap, and samples of PyPI, crates.io and RubyGems with tree.through-symlink.

ecosystemtarballswith itshare
Spack37,5530none
nixpkgs18,9900none
Guix10,1680none
PyPI10,0000none
crates.io5,0000none
RubyGems5,0000none
live-bootstrap1710none
total (distinct)82,5860none