[issue21207] urandom persistent fd - not re-openned after fd close
Roundup Robot added the comment: New changeset a66524ce9551 by Antoine Pitrou in branch '3.4': Issue #21207: Detect when the os.urandom cached fd has been closed or replaced, and open it anew. http://hg.python.org/cpython/rev/a66524ce9551 New changeset d3e8db93dc18 by Antoine Pitrou in branch 'default': Issue #21207: Detect when the os.urandom cached fd has been closed or replaced, and open it anew. http://hg.python.org/cpython/rev/d3e8db93dc18 -- nosy: +python-dev ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue21207 ___ ___ Python-bugs-list mailing list Unsubscribe: https://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue21207] urandom persistent fd - not re-openned after fd close
Antoine Pitrou added the comment: Ok, I've committed the patch. Hopefully this will also fix any similar issues. -- resolution: - fixed stage: patch review - resolved status: open - closed ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue21207 ___ ___ Python-bugs-list mailing list Unsubscribe: https://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue21207] urandom persistent fd - not re-openned after fd close
Charles-François Natali added the comment: Updated patch using an anonymous struct. LGTM! -- ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue21207 ___ ___ Python-bugs-list mailing list Unsubscribe: https://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue21207] urandom persistent fd - not re-openned after fd close
Antoine Pitrou added the comment: Updated patch using an anonymous struct. -- Added file: http://bugs.python.org/file35006/urandom_fd_reopen2.patch ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue21207 ___ ___ Python-bugs-list mailing list Unsubscribe: https://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue21207] urandom persistent fd - not re-openned after fd close
Daniel Black added the comment: maybe you've thought and dismissed this already but os.close could call dev_urandom_close for the urandom_fd. Then there's no fstat calls in every random access. As a sweeping close all isn't going to occur that often and extra open probably isn't that much overhead. -- ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue21207 ___ ___ Python-bugs-list mailing list Unsubscribe: https://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue21207] urandom persistent fd - not re-openned after fd close
Antoine Pitrou added the comment: maybe you've thought and dismissed this already but os.close could call dev_urandom_close for the urandom_fd. Then there's no fstat calls in every random access. That's fine if os.close() is indeed used to close fd, but not if some third-party library uses the C close() function directly. I don't know how likely that is, but I think it's better to squash the bug completely, rather than 80% of it :-) (also some other stdlib code might (?) also call C close()...) -- ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue21207 ___ ___ Python-bugs-list mailing list Unsubscribe: https://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue21207] urandom persistent fd - not re-openned after fd close
Daniel Black added the comment: fine by me. was just a thought -- ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue21207 ___ ___ Python-bugs-list mailing list Unsubscribe: https://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue21207] urandom persistent fd - not re-openned after fd close
Changes by Alex Gaynor alex.gay...@gmail.com: -- nosy: +alex ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue21207 ___ ___ Python-bugs-list mailing list Unsubscribe: https://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue21207] urandom persistent fd - not re-openned after fd close
Antoine Pitrou added the comment: Here is a proposed patch (with tests). -- keywords: +patch stage: - patch review Added file: http://bugs.python.org/file34965/urandom_fd_reopen.patch ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue21207 ___ ___ Python-bugs-list mailing list Unsubscribe: https://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue21207] urandom persistent fd - not re-openned after fd close
Antoine Pitrou added the comment: Hmm, the patch doesn't release the GIL around the fstat() calls, I wonder if that's necessary. -- ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue21207 ___ ___ Python-bugs-list mailing list Unsubscribe: https://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue21207] urandom persistent fd - not re-openned after fd close
Charles-François Natali added the comment: I was expecting to see such a report :-) I'm al for the st_ino+st_dev check, it can't hurt. But everybody must keep in mind that if another thread messes with the FD between the check and the read, there's nothing we can do... -- ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue21207 ___ ___ Python-bugs-list mailing list Unsubscribe: https://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue21207] urandom persistent fd - not re-openned after fd close
STINNER Victor added the comment: I agree in part, but it's quite common to close fd's in some cases like in a child process after using os.fork() Which project or Python module does that? Can you show me the code? -- nosy: +haypo ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue21207 ___ ___ Python-bugs-list mailing list Unsubscribe: https://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue21207] urandom persistent fd - not re-openned after fd close
Steven Hiscocks added the comment: Issue where I hit this is in Fail2Ban: https://github.com/fail2ban/fail2ban/issues/687 Lines of code where this occurs: https://github.com/fail2ban/fail2ban/blob/1c65b946171c3bbc626ddcd9320ea2515018677b/fail2ban/server/server.py#L518-530 There are other examples of closing file descriptors in other packages which create daemon processes, as well as code snippets about, as it is typical behaviour to close files. (http://en.wikipedia.org/wiki/Daemon_%28computing%29#Creation) -- ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue21207 ___ ___ Python-bugs-list mailing list Unsubscribe: https://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue21207] urandom persistent fd - not re-openned after fd close
Antoine Pitrou added the comment: Well, on the one hand this does sound like a valid use case. On the other hand, once the urandom file descriptor is closed by third-party code, it can very well be re-opened to point to another file, and then os.urandom() will start behaving in a very bad way. Here is a possible solution in Python: - when opening the urandom fd for the first time, record its st_ino and st_dev - when calling urandom() a second time, call fstat() on the fd and check the st_ino and st_dev with the known values - if the values have changed (or if fstat() fails with EBADF), open a new fd to /dev/urandom, again -- nosy: +neologix type: crash - behavior versions: +Python 3.5 ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue21207 ___ ___ Python-bugs-list mailing list Unsubscribe: https://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue21207] urandom persistent fd - not re-openned after fd close
Raymond Hettinger added the comment: Christian, do you see a security risk with the proposed change? -- nosy: +christian.heimes, rhettinger ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue21207 ___ ___ Python-bugs-list mailing list Unsubscribe: https://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue21207] urandom persistent fd - not re-openned after fd close
Changes by Daniel Black daniel.s...@internode.on.net: -- nosy: +grooverdan ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue21207 ___ ___ Python-bugs-list mailing list Unsubscribe: https://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue21207] urandom persistent fd - not re-openned after fd close
Steven Hiscocks added the comment:
Just to add for those interested: a possible work around solution is using
os.path.sameopenfile to check fds against another known fd for urandom.
And for those wish to have a bit of fun (and maybe a security consideration):
python -c import os;os.urandom(1);os.closerange(3,256);fd =
open('/dev/zero');print(os.urandom(10))
b'\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00'
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[issue21207] urandom persistent fd - not re-openned after fd close
New submission from Steven Hiscocks: I've seen an issue with using urandom on Python 3.4. I've traced down to fd being closed (not by core CPython, but by third party library code). After this, access to urandom fails. I assume this is related to persistent fd for urandom in http://bugs.python.org/issue18756 $ python -c import os;os.urandom(1);os.closerange(3,256);os.urandom(1) Traceback (most recent call last): File string, line 1, in module OSError: [Errno 9] Bad file descriptor -- messages: 215973 nosy: kwirk priority: normal severity: normal status: open title: urandom persistent fd - not re-openned after fd close type: crash versions: Python 3.4 ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue21207 ___ ___ Python-bugs-list mailing list Unsubscribe: https://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue21207] urandom persistent fd - not re-openned after fd close
Changes by STINNER Victor victor.stin...@gmail.com: -- nosy: +pitrou ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue21207 ___ ___ Python-bugs-list mailing list Unsubscribe: https://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue21207] urandom persistent fd - not re-openned after fd close
Antoine Pitrou added the comment: Well, if a third-party library decides to close fds it doesn't own, that library should have a bug reported to it. -- ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue21207 ___ ___ Python-bugs-list mailing list Unsubscribe: https://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue21207] urandom persistent fd - not re-openned after fd close
Steven Hiscocks added the comment: I agree in part, but it's quite common to close fd's in some cases like in a child process after using os.fork(). There is no way, as far as I'm aware, to identify which fd is associated with /dev/urandom to keep it open; or anyway to reopen it such that other libraries which depend on it can use it (for example tempfile.TemporaryFile). -- ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue21207 ___ ___ Python-bugs-list mailing list Unsubscribe: https://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
