Brijesh Singh <brijesh.singh@xxxxxxx> writes: > On 3/6/20 11:20 AM, Connor Kuehl wrote: >> Instead of using CAP_SYS_ADMIN which is restricted to the root user, >> check the file mode for write permissions before executing commands that >> can affect the platform. This allows for more fine-grained access >> control to the SEV ioctl interface. This would allow a SEV-only user >> or group the ability to administer the platform without requiring them >> to be root or granting them overly powerful permissions. >> >> For example: >> >> chown root:root /dev/sev >> chmod 600 /dev/sev >> setfacl -m g:sev:r /dev/sev >> setfacl -m g:sev-admin:rw /dev/sev >> >> In this instance, members of the "sev-admin" group have the ability to >> perform all ioctl calls (including the ones that modify platform state). >> Members of the "sev" group only have access to the ioctls that do not >> modify the platform state. >> >> This also makes opening "/dev/sev" more consistent with how file >> descriptors are usually handled. By only checking for CAP_SYS_ADMIN, >> the file descriptor could be opened read-only but could still execute >> ioctls that modify the platform state. This patch enforces that the file >> descriptor is opened with write privileges if it is going to be used to >> modify the platform state. >> >> This flexibility is completely opt-in, and if it is not desirable by >> the administrator then they do not need to give anyone else access to >> /dev/sev. >> >> Signed-off-by: Connor Kuehl <ckuehl@xxxxxxxxxx> >> --- >> drivers/crypto/ccp/sev-dev.c | 33 +++++++++++++++++---------------- >> 1 file changed, 17 insertions(+), 16 deletions(-) >> > > Reviewed-by: Brijesh Singh <brijesh.singh@xxxxxxx> > > thanks Reviewed-by: Bandan Das <bsd@xxxxxxxxxx>
