| msg289253 - (view) |
Author: Matt B (posita) * |
Date: 2017-03-08 19:32 |
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| It looks like there's a problem examining ``.tar`` files with no entries: ``` $ # ================================================================== $ # Extract test cases (attached to this bug report) $ tar xpvf tarfail.tar.bz2 x tarfail/ x tarfail/tarfail.py x tarfail/test.tar x tarfail/test.tar.bz2 $ cd tarfail $ # ================================================================== $ # Note that test.tar.bz2 is just test.tar, but bzip2'ed: $ bzip2 -c test.tar | openssl dgst -sha256 ; openssl dgst -sha256 test.tar.bz2 f4fad25a0e7a451ed906b76846efd6d2699a65b40795b29553addc35bf9a75c8 SHA256(test.tar.bz2)= f4fad25a0e7a451ed906b76846efd6d2699a65b40795b29553addc35bf9a75c8 $ wc -c test.tar* # these are not empty files 10240 test.tar 46 test.tar.bz2 10286 total $ tar tpvf test.tar # no entries $ tar tpvf test.tar.bz2 # no entries $ # ================================================================== $ # test.tar.bz2 works, but test.tar causes problems (tested in 2.7, $ # 3.5, and 3.6): $ python2.7 tarfail.py opening /…/tarfail/test.tar.bz2 opening /…/tarfail/test.tar E ====================================================================== ERROR: test_next (__main__.TestTarFileNext) ---------------------------------------------------------------------- Traceback (most recent call last): File "tarfail.py", line 29, in test_next next_info = tar_file.next() File "/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/tarfile.py", line 2350, in next self.fileobj.seek(self.offset - 1) IOError: [Errno 22] Invalid argument ---------------------------------------------------------------------- Ran 1 test in 0.005s FAILED (errors=1) $ python3.5 tarfail.py opening /…/tarfail/test.tar.bz2 opening /…/tarfail/test.tar E ====================================================================== ERROR: test_next (__main__.TestTarFileNext) ---------------------------------------------------------------------- Traceback (most recent call last): File "tarfail.py", line 29, in test_next next_info = tar_file.next() File "/Library/Frameworks/Python.framework/Versions/3.5/lib/python3.5/tarfile.py", line 2273, in next self.fileobj.seek(self.offset - 1) OSError: [Errno 22] Invalid argument ---------------------------------------------------------------------- Ran 1 test in 0.066s FAILED (errors=1) $ python3.6 tarfail.py opening /…/tarfail/test.tar.bz2 opening /…/tarfail/test.tar E ====================================================================== ERROR: test_next (__main__.TestTarFileNext) ---------------------------------------------------------------------- Traceback (most recent call last): File "tarfail.py", line 29, in test_next next_info = tar_file.next() File "/Library/Frameworks/Python.framework/Versions/3.6/lib/python3.6/tarfile.py", line 2279, in next self.fileobj.seek(self.offset - 1) OSError: [Errno 22] Invalid argument ---------------------------------------------------------------------- Ran 1 test in 0.090s FAILED (errors=1) ``` Here's the issue (as far as I can tell): ``` $ ipdb tarfail.py > /…/tarfail/tarfail.py(3)() 2 ----> 3 from __future__ import ( 4 absolute_import, division, print_function, unicode_literals, ipdb> b /Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/tarfile.py:2350 Breakpoint 1 at /Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/tarfile.py:2350 ipdb> c opening /…/tarfail/test.tar.bz2 > /Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/tarfile.py(2350)next() 2349 if self.offset != self.fileobj.tell(): 1> 2350 self.fileobj.seek(self.offset - 1) 2351 if not self.fileobj.read(1): ipdb> self.fileobj <bz2.BZ2File object at 0x1067791d0> ipdb> self.offset, self.fileobj.tell(), self.offset - 1 (0, 512, -1) ipdb> c opening /…/tarfail/test.tar > /Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/tarfile.py(2350)next() 2349 if self.offset != self.fileobj.tell(): 1> 2350 self.fileobj.seek(self.offset - 1) 2351 if not self.fileobj.read(1): ipdb> self.fileobj <open file u'/…/tarfail/test.tar', mode 'rb' at 0x10676dae0> ipdb> self.offset, self.fileobj.tell(), self.offset - 1 (0, 512, -1) ipdb> c E ====================================================================== ERROR: test_next (__main__.TestTarFileNext) ---------------------------------------------------------------------- Traceback (most recent call last): File "tarfail.py", line 29, in test_next next_info = tar_file.next() File "/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/tarfile.py", line 2350, in next self.fileobj.seek(self.offset - 1) IOError: [Errno 22] Invalid argument ---------------------------------------------------------------------- Ran 1 test in 38.300s FAILED (errors=1) The program exited via sys.exit(). Exit status: True > /…/tarfail/tarfail.py(3)() 2 ----> 3 from __future__ import ( 4 absolute_import, division, print_function, unicode_literals, ipdb> EOF ``` Apparently, ``bz2.BZ2File`` allows seeking to pre-0 (negative) values, whereas more primitive files are not so forgiving. The offending line looks like it can be traced back to this commit: https://github.com/python/cpython/blame/2.7/Lib/tarfile.py#L2350 https://github.com/python/cpython/blame/3.3/Lib/tarfile.py#L2252 https://github.com/python/cpython/blame/3.4/Lib/tarfile.py#L2252 https://github.com/python/cpython/blame/3.5/Lib/tarfile.py#L2273 https://github.com/python/cpython/blame/3.6/Lib/tarfile.py#L2286 (My apologies for not catching this sooner.) |
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| msg289265 - (view) |
Author: Matt B (posita) * |
Date: 2017-03-09 01:53 |
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| FWIW, the (offending) fix for #24259 was introduced (e.g., in 2.7) via 2.7.10. I've verified that 2.7.9 works as expected: ``` $ python -V Python 2.7.9 $ python tarfail.py opening /…/tarfail/test.tar.bz2 opening /…/tarfail/test.tar . ---------------------------------------------------------------------- Ran 1 test in 0.010s OK ``` So this should probably be considered a regression. |
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| msg289408 - (view) |
Author: Matt B (posita) * |
Date: 2017-03-10 20:21 |
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| I'm not sure if it helps at this point, but I've tried several "flavors" of apparently legit tar files with zero entries. All fail. ``tarfile`` module: ``` $ ( set -x ; cd /tmp | |
exit 1 ; python -V ; rm -fv test.tar ; python -c 'import os, tarfile ; fd = os.open("test.tar", os.O_WRONLY |
os.O_CREAT |
os.O_EXCL) ; f = os.fdopen(fd, "w") ; f = tarfile.open("test.tar", "w", f) ; f.close() ; f = tarfile.open("test.tar") ; print("okay so far; calling f.next()...") ; f.next()' ; openssl dgst -sha256 test.tar ; rm -fv test.tar ) +/bin/zsh:496> cd /tmp +/bin/zsh:496> python -V Python 2.7.13 +/bin/zsh:496> rm -v -fv test.tar +/bin/zsh:496> python -c 'import os, tarfile ; fd = os.open("test.tar", os.O_WRONLY |
os.O_CREAT |
os.O_EXCL) ; f = os.fdopen(fd, "w") ; f = tarfile.open("test.tar", "w", f) ; f.close() ; f = tarfile.open("test.tar") ; print("okay so far; calling f.next()...") ; f.next()' okay so far; calling f.next()... Traceback (most recent call last): File "", line 1, in File "/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/tarfile.py", line 2350, in next self.fileobj.seek(self.offset - 1) IOError: [Errno 22] Invalid argument +/bin/zsh:496> openssl dgst -sha256 test.tar SHA256(test.tar)= 84ff92691f909a05b224e1c56abb4864f01b4f8e3c854e4bb4c7baf1d3f6d652 +/bin/zsh:496> rm -v -fv test.tar test.tar ``` BSD tar (OS X): ``` $ ( set -x ; cd /tmp |
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| msg289409 - (view) |
Author: Matt B (posita) * |
Date: 2017-03-10 20:31 |
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| This patch (also attached) seems to address this particular use case: ``` --- a/Lib/tarfile.py 2016-12-17 12:41:21.000000000 -0800 +++ b/Lib/tarfile.py 2017-03-10 12:23:34.000000000 -0800 @@ -2347,7 +2347,7 @@ # Advance the file pointer. if self.offset != self.fileobj.tell(): - self.fileobj.seek(self.offset - 1) + self.fileobj.seek(max(self.offset - 1, 0)) if not self.fileobj.read(1): raise ReadError("unexpected end of data") ``` However, I am unfamiliar with the code, especially in light of #24259, and haven't tested it thoroughly. Oversight is needed. |
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| msg289417 - (view) |
Author: Matt B (posita) * |
Date: 2017-03-10 23:00 |
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| After some consideration, I think this is probably more correct: ``` --- /Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/tarfile.py 2016-12-17 12:41:21.000000000 -0800 +++ tarfile.py 2017-03-10 14:57:15.000000000 -0800 @@ -2347,9 +2347,10 @@ # Advance the file pointer. if self.offset != self.fileobj.tell(): - self.fileobj.seek(self.offset - 1) + self.fileobj.seek(max(self.offset - 1, 0)) if not self.fileobj.read(1): raise ReadError("unexpected end of data") + self.fileobj.seek(self.offset) # Read the next block. tarinfo = None ``` But again, I'm no expert here. |
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