Bug 1056672
| Summary: | tar uses wrong magic number for xz archives | ||
|---|---|---|---|
| Product: | Red Hat Enterprise Linux 6 | Reporter: | Bryn M. Reeves <bmr> |
| Component: | tar | Assignee: | Pavel Raiskup <praiskup> |
| Status: | CLOSED ERRATA | QA Contact: | qe-baseos-daemons |
| Severity: | medium | Docs Contact: | |
| Priority: | medium | ||
| Version: | 6.5 | CC: | dkutalek, jpopelka, ovasik, psklenar |
| Target Milestone: | rc | Keywords: | EasyFix |
| Target Release: | --- | ||
| Hardware: | All | ||
| OS: | Linux | ||
| Whiteboard: | |||
| Fixed In Version: | tar-1.23-12.el6 | Doc Type: | Bug Fix |
| Doc Text: |
Previously, tar did not automatically detect archives compressed by the xz program if the user did not specify the "-J" or "--xz" option on the command line. As a consequence, if the processed archive had the ".xz" extension, tar extracted or listed the contents of the archive but printed an error message and eventually exited with a non-zero exit status. If the archive did not have this extension, tar failed. With this update, the automatic recognition mechanism has been improved. As a result, tar no longer prints an error message in this scenario, and it extracts or lists the contents of such archives correctly regardless of the extension.
|
Story Points: | --- |
| Clone Of: | Environment: | ||
| Last Closed: | 2015-07-22 06:13:30 UTC | Type: | Bug |
| Regression: | --- | Mount Type: | --- |
| Documentation: | --- | CRM: | |
| Verified Versions: | Category: | --- | |
| oVirt Team: | --- | RHEL 7.3 requirements from Atomic Host: | |
| Cloudforms Team: | --- | Target Upstream Version: | |
| Embargoed: | |||
| Bug Depends On: | |||
| Bug Blocks: | 1070830, 1159820 | ||
Turns out this was already fixed upstream in a couple of commits in 2010:
commit 80a6ef7d94ce144db0249384e55846baa404f4dd
Author: Sergey Poznyakoff <gray.ua>
Date: Mon Jun 28 00:04:49 2010 +0300
Minor fix.
* src/buffer.c (magic): Split the character constant to help
cc recognize character boundaries (7 is a valid hex character).
diff --git a/src/buffer.c b/src/buffer.c
index 5b7cbc7..444f612 100644
--- a/src/buffer.c
+++ b/src/buffer.c
@@ -225,7 +225,7 @@ static struct zip_magic const magic[] = {
{ ct_lzip, 4, "LZIP", LZIP_PROGRAM, "--lzip" },
{ ct_lzma, 6, "\xFFLZMA", LZMA_PROGRAM, "--lzma" },
{ ct_lzop, 4, "\211LZO", LZOP_PROGRAM, "--lzop" },
- { ct_xz, 6, "\xFD7zXZ", XZ_PROGRAM, "-J" },
+ { ct_xz, 6, "\xFD" "7zXZ", XZ_PROGRAM, "-J" },
};
commit 9b31db388e6af753ec2e1c84db53a5d47e94ec15
Author: Sergey Poznyakoff <gray.ua>
Date: Sun Jun 27 23:42:08 2010 +0300
Minor fix.
* src/buffer.c (magic): Fix xz magic.
diff --git a/src/buffer.c b/src/buffer.c
index 239d3f1..5b7cbc7 100644
--- a/src/buffer.c
+++ b/src/buffer.c
@@ -225,7 +225,7 @@ static struct zip_magic const magic[] = {
{ ct_lzip, 4, "LZIP", LZIP_PROGRAM, "--lzip" },
{ ct_lzma, 6, "\xFFLZMA", LZMA_PROGRAM, "--lzma" },
{ ct_lzop, 4, "\211LZO", LZOP_PROGRAM, "--lzop" },
- { ct_xz, 6, "\0xFD7zXZ", XZ_PROGRAM, "-J" },
+ { ct_xz, 6, "\xFD7zXZ", XZ_PROGRAM, "-J" },
};
Since the problem described in this bug report should be resolved in a recent advisory, it has been closed with a resolution of ERRATA. For information on the advisory, and where to find the updated files, follow the link below. If the solution does not work for you, open a new bug report. https://rhn.redhat.com/errata/RHBA-2015-1285.html |
Description of problem: The tar program uses a built-in table of magic numbers to identify compressed archives. If the table fails to match a given file then tar will still attempt to open it by assuming the compression type based on file extension: 219 static struct zip_magic const magic[] = { 220 { ct_tar }, 221 { ct_none, }, 222 { ct_compress, 2, "\037\235", COMPRESS_PROGRAM, "-Z" }, 223 { ct_gzip, 2, "\037\213", GZIP_PROGRAM, "-z" }, 224 { ct_bzip2, 3, "BZh", BZIP2_PROGRAM, "-j" }, 225 { ct_lzip, 4, "LZIP", LZIP_PROGRAM, "--lzip" }, 226 { ct_lzma, 6, "\xFFLZMA", LZMA_PROGRAM, "--lzma" }, 227 { ct_lzop, 4, "\211LZO", LZOP_PROGRAM, "--lzop" }, 228 { ct_xz, 6, "\0xFD7zXZ", XZ_PROGRAM, "-J" }, 229 }; [...] 324 case ct_none: 325 if (shortfile) 326 ERROR ((0, 0, _("This does not look like a tar archive"))); 327 set_comression_program_by_suffix (archive_name_array[0], NULL); 328 if (!use_compress_program_option) 329 return archive; 330 break; An exception is for "short" files; in this case an error message is logged and tar will eventually exit with failure status: # tar tf foo.tar.xz tar: This does not look like a tar archive foo/ foo/bar tar: Exiting with failure status due to previous errors # echo $? 2 This is misleading as tar has guessed the compression type and successfully processed the archive. Version-Release number of selected component (if applicable): tar-1.23-11.el6 How reproducible: 100% Steps to Reproduce: 1. Create an xz compressed archive that is < 1 block in size 2. Run tar on the resulting archive (t/x/whatever) Actual results: # rm -rf foo # mkdir foo # touch foo/bar # tar cf foo.tar foo # xz foo.tar # tar tf foo.tar.xz tar: This does not look like a tar archive foo/ foo/bar tar: Exiting with failure status due to previous errors # echo $? 2 Expected results: # rm -rf foo # mkdir foo # touch foo/bar # tar cf foo.tar foo # xz foo.tar # tar tf foo.tar.xz foo/ foo/bar # echo $? 0 Additional info: This happens because tar uses an invalid magic number for XZ files in its magic table: 228 { ct_xz, 6, "\0xFD7zXZ", XZ_PROGRAM, "-J" }, The correct magic string for XZ is "fd37 7a58 5a" (\xfd7zXZ). The '\0' encodes a null byte causing the rest of the magic string to appear empty: (gdb) p *p ----------- $38 = {type = ct_xz, length = 6, magic = 0x445e20 "", program = 0x44596a "xz", rpl_option = 0x44596d "-J"} 'FD' is then encoded as ASCII etc. It seems like the intent was to avoid gcc treating '\xfd7' as a single hex escape this will cause a "hex escape sequence out of range" warning as the 7 is interpreted as part of the escape. It seems like the simplest way to solve this is to also use a hex escape for the '7' char; this leaves the string unambiguous and fixes the problem with very small tar archives for me: { ct_xz, 6, "\xFD\x37zXZ", XZ_PROGRAM, "-J" },