Re: [nfsv4] Re: NFSv4 ACL and POSIX interaction / mask, draft-ietf-nfsv4-acls-00 not ready

[Lisa Week <Lisa.Week@Sun.COM>]

Hi,

Both Sam and I will be in Montreal and can lead a discussion.

Thanks,
Lisa

Noveck, Dave wrote On 07/08/06 09:04,:

>Andreas has asked that we consider his proposal when disucssing 
>where to go with regard to ACL in v4.1, at the Montreal IETF
>meeting.
>
>I'm wondering whether we should be discussing specific mechanisms.
>It would help me if we could have a discussion of what the goals
>should be for ACL's in v4.1.  This isn't resally clear to me but
>it could be due to my lack of attention to the matter.
>
>Is there anybody who's going to be at Montreal who could lead such
>a discussion (I'm thinking 10 minutes worth)?  Or are the goals
>already clear in which case somebody can explain things to me 
>offline and we can avoid wasting other people's time. 
>
>-----Original Message-----
>From: Sam Falkner [mailto:Sam.Falkner@Sun.COM] 
>Sent: Saturday, July 08, 2006 10:32 AM
>To: Sam Falkner
>Cc: nfs@lists.sourceforge.net; Spencer Shepler; Pawlowski, Brian;
>nfsv4@ietf.org; Lisa Week
>Subject: Re: [nfsv4] Re: NFSv4 ACL and POSIX interaction /
>mask,draft-ietf-nfsv4-acls-00 not ready
>
>On Jul 7, 2006, at 9:45 PM, Sam Falkner wrote:
>
>  
>
>>On Jul 7, 2006, at 5:55 AM, Andreas Gruenbacher wrote:
>>    
>>
>>>Alternative Proposal
>>>====================
>>>
>>>Instead of adding DENY entries to the ACL for the purpose of masking,
>>>      
>>>
>
>  
>
>>>attach three optional attributes to each file: owner_class_mask, 
>>>group_class_mask, and other_class_mask. When those attributes are 
>>>present, they define which permissions in an ACE are effective.
>>>
>>>Each ACE is is restricted by one of these mask attributes in each 
>>>access
>>>check:
>>>
>>> - OWNER@ entries and entries for the user@domain that currently owns
>>>      
>>>
>
>  
>
>>>the file
>>>   are restricted by owner_class_mask.
>>>
>>> - EVERYONE@ entries are restricted by other_class_mask.
>>>
>>> - All other entries are restricted by group_class_mask.
>>>
>>>The effective permissions are computed as the bitwise and (&) of the 
>>>ACE mask and the associated class_mask attribute.
>>>      
>>>
>>I take it you mean that "the effective access mask bits for ACEs of 
>>type ALLOW"?
>>
>>    
>>
>>>When doing a chmod(2) or when applying a create mask, the 
>>>owner_class_mask, group_class_mask, and other_class_mask attributes 
>>>are modified according to the owner class, group class, and other 
>>>class permissions of the mode parameter as follows:
>>>
>>> - The POSIX read permission implies the ACE4_READ_DATA, 
>>>ACE4_READ_ATTRIBUTES, ACE4_READ_ACL, and ACE4_SYNCHRONIZE bitmask 
>>>flags.
>>>
>>> - The POSIX write permission implies the ACE4_WRITE_DATA, 
>>>ACE4_APPEND_DATA, ACE4_WRITE_ATTRIBUTES, ACE4_DELETE_CHILD, and 
>>>ACE4_SYNCHRONIZE bitmask flags.
>>>      
>>>
>>I'm not sure I agree about ACE4_WRITE_ATTRIBUTES, but that's a minor 
>>detail.
>>
>>    
>>
>>> - The POSIX execute permission implies the ACE4_EXECUTE mask.
>>>      
>>>
>>>This saves us from bloating ACLs with DENY entries, is more efficient
>>>      
>>>
>
>  
>
>>>when doing a chmod, and also saves us from destroying permissions in 
>>>user provided DENY entries.
>>>      
>>>
>>Yes, but at the cost of adding new file attributes...  Don't get me 
>>wrong, I do see merit in this proposal, but I don't know if it'll be 
>>acceptable.
>>
>>    
>>
>>>When an ACL is set, then set all mask attributes to the values 
>>>provided in the same SETATTR operation, and set the remaining mask 
>>>attributes to the union of all ALLOW ACL entries in the ACL that the 
>>>class applies to.
>>>      
>>>
>>This doesn't take the ordering of the ACL into account; is this your 
>>intention?  So
>>
>>GROUP@:read_data/write_data:DENY
>>GROUP@:read_data/write_data:ALLOW
>>
>>would result in a group_class_mask of read_data|write_data, right?   
>>(I'm not saying it's wrong, I'm just making sure I understand.)
>>
>>    
>>
>>>Without any further changes, NFSv4 clients not aware of the three 
>>>optional attributes would not be aware of the restrictions imposed by
>>>      
>>>
>
>  
>
>>>those masks when querying for the ACL. This would create an 
>>>interoperability problem, and possible security holes. To solve this 
>>>problem, we can extend the GETATTR operation as follows:
>>>
>>>When a client requests the ACL attribute, check if it also requests 
>>>one or more of the three optional owner_class_mask, group_class_mask,
>>>      
>>>
>
>  
>
>>>or other_class_mask attributes. If it does, then send the requested 
>>>attributes as they are. If the client requests only the ACL without 
>>>any of the masks, return an ACL with only effective mask flags set, 
>>>and with all other flags removed.
>>>      
>>>
>>I assume you mean in the ALLOW ACEs only, right?
>>    
>>
>
>More thoughts on this model and getattr.  Giving different versions of
>the ACL depending on how it's requested leads to problems.  To recap, if
>NFSv4.0 client asks for the post-chmod ACL, it'll get the inhibited
>version of the ACL.  Tools for modifying an ACL invariably do
>read/modify/write.  So NFSv4.0 client reads the stripped down ACL,
>modifies it, and writes it back.  At this point, information is lost
>-- the stripped down ACL is now the only ACL we have.  This leads to
>future environments where some classes of clients inadvertently do bad
>things, while others behave more correctly.
>
>The ACL model in draft-ietf-nfsv4-minorversion1-03.txt always shows
>every client the entire, correct ACL, every time.
>
>- Sam
>
>  
>
>>>Alternate permissions in the ACL can be enabled by either setting an 
>>>ACL without providing full mask entries, or by setting the 
>>>appropriate
>>>bit(s) in
>>>the corresponding mask entry or entries.
>>>      
>>>
>>Yes, I think I understand.
>>
>>    
>>
>>>When comparing POSIX ACLs and the NFSv4 ACL + mask attributes as 
>>>proposed here, one obvious difference is that POSIX ACLs have only 
>>>one mask entry, while I propose three mask entries here. The reason 
>>>for this is that POSIX ACLs can at most grant read, write, and 
>>>execute permissions, and so with POSIX ACLs, the File Owner Class 
>>>permissions are always identical to the permissions granted to the 
>>>owner, and the File Other Class permissions are always identical to 
>>>the permissions granted to others. With NFSv4 ACLs, OWNER@ and 
>>>EVERYONE@ entries may grant additional permissions that go beyond 
>>>what POSIX read, write, and execute can grant, and we need a 
>>>mechanism so that those alternate permissions can be turned off by 
>>>chmod and during file create without destroying the permissions.
>>>      
>>>
>>Given that EVERYONE@ is not equivalent to the POSIX "other" class, it 
>>could be trimmed down to two.
>>
>>    
>>
>>>I would appreciate if you could take this alternative proposal into 
>>>consideration when deciding how to proceed with NFSv4 Minor Version 1
>>>      
>>>
>
>  
>
>>>at next week's IETF 66 meeting.
>>>      
>>>
>>This proposal certainly has its merits.  I have doubts about the 
>>feasibility of adding two or three new file attributes, and new as- 
>>yet-unimplemented semantics, into the minorversion1 draft.  I have 
>>doubts about how this would be implemented on a Windows-based server.
>>
>>The current design specified in draft-ietf-nfsv4- minorversion1-03.txt
>>    
>>
>
>  
>
>>has implementation experience -- it's released in Solaris 10 update 3,
>>    
>>
>
>  
>
>>a shipping product.  It meets strict POSIX requirements for those 
>>implementations that choose to conform to POSIX.  I believe it's fully
>>    
>>
>
>  
>
>>implementable on a Windows-based server.
>>
>>I too hope that this can be discussed at IETF 66.
>>
>>- Sam
>>
>>    
>>
>>>Thanks and best regards,
>>>Andreas
>>>
>>>      
>>>
>>>>REFERENCES
>>>>
>>>>[1] Sam Falkner et al.: NFS Version 4 ACLs, draft-ietf-nfsv4- 
>>>>acls-00.txt
>>>>
>>>>[2] POSIX 1003.1e/2c draft 17 (withdrawn), 
>>>>http://wt.xpilot.org/publications/posix.1e
>>>>
>>>>[3] Marius Aamodt Eriksen et al.: Mapping Between NFSv4 and Posix 
>>>>Draft ACLs, draft-ietf-nfsv4-acl-mapping-04.txt
>>>>
>>>>[4] Spencer Shepler (editor): NFSv4 Minor Version 1, 
>>>>draft-ietf-nfsv4-minorversion1-03.txt
>>>>        
>>>>
>>>--
>>>Andreas Gruenbacher <agruen@suse.de>
>>>Novell / SUSE Labs
>>>      
>>>
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>>    
>>
>
>
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