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
