Re: [RFC PATCH] Add SHA1 support
On Tuesday, March 17, 2020 9:17:09 PM CET, Sebastian Andrzej Siewior wrote: On 2020-03-17 00:03:03 [+0100], Dimitrios Apostolou via rsync wrote: On Thursday, February 20, 2020 10:34:53 PM CET, Sebastian Andrzej Siewior via rsync wrote: I'm still not sure if rsync requires a cryptographic hash _or_ if a strong hash like xxHash64 would be just fine for the job. I'm fairly sure the hash should *not* be easy to spoof, so I'd say a cryptographic hash is needed. As an example, if a file is replaced by a file of the same size and same hash, rsync (if -c is in use) will consider the file is the same, and avoid copying it. correct. The same goes for currently used md5 which has known collision attacks. So if you intend to spoo it, you can manufacture the same hash for two different files for both algorithms. This was not the case in 2008 when rsync 3.0.0 came out defaulting to MD5. I still think you need a cryptographic hash, even though I am not sure of how strict the requirement is. MD4 was replaced by MD5 in rsync, despite MD4 being 2x faster. I would guess it was replaced because of its weaknesses. Dimitris -- Please use reply-all for most replies to avoid omitting the mailing list. To unsubscribe or change options: https://lists.samba.org/mailman/listinfo/rsync Before posting, read: http://www.catb.org/~esr/faqs/smart-questions.html
Re: [RFC PATCH] Add SHA1 support
On Thursday, February 20, 2020 10:34:53 PM CET, Sebastian Andrzej Siewior via rsync wrote: I'm still not sure if rsync requires a cryptographic hash _or_ if a strong hash like xxHash64 would be just fine for the job. I'm fairly sure the hash should *not* be easy to spoof, so I'd say a cryptographic hash is needed. As an example, if a file is replaced by a file of the same size and same hash, rsync (if -c is in use) will consider the file is the same, and avoid copying it. Dimitris -- Please use reply-all for most replies to avoid omitting the mailing list. To unsubscribe or change options: https://lists.samba.org/mailman/listinfo/rsync Before posting, read: http://www.catb.org/~esr/faqs/smart-questions.html
Re: Would you expect --perms -M--fake-super to set the file mode to the original one?
According to --help: --fake-superstore/recover privileged attrs using xattrs So I would assume which mode it uses when it reads the file, depends on whether this option is on or off. On Monday, March 16, 2020 9:09:36 PM CET, Kevin Korb via rsync wrote: I don't believe it is possible. I think the misunderstanding stems from the fact that the permissions are even stored in the xattr. They don't need to be there but they may as well be. They don't take much space. The real question would be when rsync reads the file to restore it and the file perms are different than the ones in the xattr which set does it use? On 3/16/20 10:01 AM, Dimitrios Apostolou via rsync wrote: Thanks. This is a bit counter-intuitive to me. So how would you tell rsync to store the original permissions in the xattr, but do not touch the real file mode? On Thursday, March 12, 2020 6:26:18 PM CET, Kevin Korb via rsync wrote: ... -- Please use reply-all for most replies to avoid omitting the mailing list. To unsubscribe or change options: https://lists.samba.org/mailman/listinfo/rsync Before posting, read: http://www.catb.org/~esr/faqs/smart-questions.html
Re: Would you expect --perms -M--fake-super to set the file mode to the original one?
Thanks. This is a bit counter-intuitive to me. So how would you tell rsync to store the original permissions in the xattr, but do not touch the real file mode? On Thursday, March 12, 2020 6:26:18 PM CET, Kevin Korb via rsync wrote: I would expect that the sending rsync would only send the perms provided modified by the --chmod. I wouldn't expect the receiver to even know the other permissions. On 3/12/20 1:23 PM, Dimitrios Apostolou via rsync wrote: Thank you for the feedback, I'm glad to see that different people see the issue differently. As a followup question, what would you expect this to do: rsync --perms --chmod g+rX -M--fake-super src dst I would expect it to store the original permissions in the xattr, while ... -- Please use reply-all for most replies to avoid omitting the mailing list. To unsubscribe or change options: https://lists.samba.org/mailman/listinfo/rsync Before posting, read: http://www.catb.org/~esr/faqs/smart-questions.html
Re: Would you expect --perms -M--fake-super to set the file mode to the original one?
Thank you for the feedback, I'm glad to see that different people see the issue differently. As a followup question, what would you expect this to do: rsync --perms --chmod g+rX -M--fake-super src dst I would expect it to store the original permissions in the xattr, while modifying the real file mode according to the chmod. On Thursday, March 12, 2020 6:06:34 PM CET, Kevin Korb via rsync wrote: Permissions don't require super. Any place where permissions can't be stored certainly can't handle xattrs either. So, I wouldn't expect --fake-super to affect --perms at all. On 3/12/20 12:46 PM, Dimitrios Apostolou via rsync wrote: rsync --perms -M--fake-super src dst For me, this command means that rsync should save the original perms in the xattr, and leave the real file mode to the umask default. Currently it also modifies the real file mode, and there is no way to store something different ... -- Please use reply-all for most replies to avoid omitting the mailing list. To unsubscribe or change options: https://lists.samba.org/mailman/listinfo/rsync Before posting, read: http://www.catb.org/~esr/faqs/smart-questions.html
Would you expect --perms -M--fake-super to set the file mode to the original one?
rsync --perms -M--fake-super src dst For me, this command means that rsync should save the original perms in the xattr, and leave the real file mode to the umask default. Currently it also modifies the real file mode, and there is no way to store something different in the xattr. According to an old bug report that I found, more people would like --fake-super to be a complete attribute emulation layer. https://bugzilla.samba.org/show_bug.cgi?id=7112 Do you agree? I'm in the process of implementing this as a bug fix to rsync, and would like to know if everybody agrees with this behaviour. The patch would also modify the man page to document it under --perms. Regards, Dimitris -- Please use reply-all for most replies to avoid omitting the mailing list. To unsubscribe or change options: https://lists.samba.org/mailman/listinfo/rsync Before posting, read: http://www.catb.org/~esr/faqs/smart-questions.html
Re: How Can I save the original permissions while setting g+rX for all files
Yes indeed, it is setting both the permissions. So it sets the desirable access rights to the file, but does not save the original mode in the xattr. So it's not really working out for me. On Monday, December 9, 2019 2:11:23 AM CET, Kevin Korb via rsync wrote: When I try it the chmod works on both the real permissions and the permissions in the xatttr. Maybe the behavior has changed since whatever version you have (3.1.3 here) but this probably wouldn't help you either. On 12/8/19 7:56 PM, Dimitrios Apostolou via rsync wrote: Hello list! Combining -M--fake-super with --chmod ends up changing the permissions stored in the fake-super xattrs. I.e. the permissions stored in the xattr, are affected by --chmod. ... -- Please use reply-all for most replies to avoid omitting the mailing list. To unsubscribe or change options: https://lists.samba.org/mailman/listinfo/rsync Before posting, read: http://www.catb.org/~esr/faqs/smart-questions.html
How Can I save the original permissions while setting g+rX for all files
Hello list! Combining -M--fake-super with --chmod ends up changing the permissions stored in the fake-super xattrs. I.e. the permissions stored in the xattr, are affected by --chmod. The desirable behaviour for me would be for --chmod to modify the real permissions of the destination files. The use case is writing a backup as a non-root user, having it readable by the group (g+rX), while also saving the original permissions in the xattr. Is it a bug? Any suggestions on how I can achieve what I want? Thanks in advance, Dimitris -- Please use reply-all for most replies to avoid omitting the mailing list. To unsubscribe or change options: https://lists.samba.org/mailman/listinfo/rsync Before posting, read: http://www.catb.org/~esr/faqs/smart-questions.html
