On Thu 27-09-18 23:05:14, Matthew Bobrowski wrote: > This is a reduced version of a patch that I originally submitted a while ago. > > In short, the fanotify API currently does not provide any means for user space > programs to receive events specifically when a file has been opened with the > intent to be executed. The FAN_EXEC flag will be set within the event mask when > a object has been opened with one of the open flags being __FMODE_EXEC. > > Linux is used as an Operating System in some products, with an environment that > can be certified under the Common Criteria Operating System Protection Profile > (OSPP). This is a formal threat model for a class of technology. It requires > specific countermeasures to mitigate threats. It requires documentation to > explain how a product implements these countermeasures. It requires proof via a > test suite to demonstrate that the requirements are met, observed and checked by > an independent qualified third party. The latest set of requirements for OSPP > v4.2 can be found here: > > https://www.niap-ccevs.org/Profile/Info.cfm?PPID=424&id=424 > > If you look on page 58, you will see the following requirement: > > FPT_SRP_EXT.1 Software Restriction Policies FPT_SRP_EXT.1.1 > > The OS shall restrict execution to only programs which match an administrator > specified [selection: > file path, > file digital signature, > version, > hash, > [assignment: other characteristics] > ] > > This patch is to help aid in meeting this requirement. > > Signed-off-by: Matthew Bobrowski <mbobrowski@xxxxxxxxxxxxxx> I agree with Amir's points wrt API so I won't repeat those. But I have one more API question: You implement FS_EXEC as a flag that can get set for certain FAN_OPEN events. That is a new API concept for fanotify. So far you can only request event of a certain type and then you get the same flag back when the event happens. There is also a case of FAN_ONDIR where you can restrict set of events only to events on a particular inode type but that's again different. Hence my question: Is there a good reason why we don't create FAN_OPEN_EXEC event that would trigger only on executable opens? If someone is interested only in executable opens, he'd have less events to care about. OTOH additional FS_EXEC flag is probably more flexible (e.g. you can easily implement equivalent of FAN_OPEN_NOEXEC in userspace if you wished). Just the inconsistency of the FS_EXEC and e.g. how we handle FAN_CLOSE_NOWRITE & FAN_CLOSE_WRITE is bothering me... Honza -- Jan Kara <jack@xxxxxxxx> SUSE Labs, CR
