> From: Mimi Zohar [mailto:zohar@xxxxxxxxxxxxx] > Sent: Friday, June 18, 2021 6:04 PM > On Thu, 2021-06-17 at 23:18 -0400, Paul Moore wrote: > > On Thu, Jun 17, 2021 at 11:28 AM Mimi Zohar <zohar@xxxxxxxxxxxxx> > wrote: > > > On Thu, 2021-06-17 at 07:09 +0000, Roberto Sassu wrote: > > > > ... > > > > > > An alternative would be to do the EVM verification twice if the > > > > first time didn't succeed (with vfs_getxattr_alloc() and with the > > > > new function that behaves like vfs_getxattr()). > > > > > > Unfortunately, I don't see an alternative. > > > > ... and while unfortunate, the impact should be non-existant if you > > are using the right tools to label files or ensuring that you are > > formatting labels properly if doing it by hand. > > > > Handling a corner case is good, but I wouldn't add a lot of code > > complexity trying to optimize it. > > From userspace it's really difficult to understand the EVM signature > verification failure is due to the missing NULL. > > Roberto, I just pushed the "evm: output EVM digest calculation info" > patch to the next-integrity-testing branch, which includes some > debugging. Instead of this patch, which returns the raw xattr data, > how about adding additional debugging info in evm_calc_hmac_or_hash() > indicating the size discrepancy between the raw xattr and the LSM > returned xattr? Good idea. Will do it. Roberto HUAWEI TECHNOLOGIES Duesseldorf GmbH, HRB 56063 Managing Director: Li Peng, Li Jian, Shi Yanli > thanks, > > Mimi
