framework.
The code is organized into a few distinct pieces:
* The meta-data store (in veriexec_metadata.c) which maps a file system
identifier, file identifier, and generation key tuple to veriexec
meta-data record.
* Fingerprint management (in veriexec_fingerprint.c) which deals with
calculating the cryptographic hash for a file and verifying it. It also
manages the loadable fingerprint modules.
* MAC policy implementation (in mac_veriexec.c) which implements the
following MAC methods:
mpo_init
Initializes the veriexec state, meta-data store, fingerprint modules,
and registers mount and unmount EVENTHANDLERs
mpo_syscall
Implements the following per-policy system calls:
MAC_VERIEXEC_CHECK_FD_SYSCALL
Check a file descriptor to see if the referenced file has a valid
fingerprint.
MAC_VERIEXEC_CHECK_PATH_SYSCALL
Check a path to see if the referenced file has a valid fingerprint.
mpo_kld_check_load
Check if loading a kld is allowed. This checks if the referenced vnode
has a valid fingerprint.
mpo_mount_destroy_label
Clears the veriexec slot data in a mount point label.
mpo_mount_init_label
Initializes the veriexec slot data in a mount point label.
The file system identifier is saved in the veriexec slot data.
mpo_priv_check
Check if a process is allowed to write to /dev/kmem and /dev/mem
devices.
If a process is flagged as trusted, it is allowed to write.
mpo_proc_check_debug
Check if a process is allowed to be debugged. If a process is not
flagged with VERIEXEC_NOTRACE, then debugging is allowed.
mpo_vnode_check_exec
Check is an exectuable is allowed to run. If veriexec is not enforcing
or the executable has a valid fingerprint, then it is allowed to run.
NOTE: veriexec will complain about mismatched fingerprints if it is
active, regardless of the state of the enforcement.
mpo_vnode_check_open
Check is a file is allowed to be opened. If verification was not
requested, veriexec is not enforcing, or the file has a valid
fingerprint, then veriexec will allow the file to be opened.
mpo_vnode_copy_label
Copies the veriexec slot data from one label to another.
mpo_vnode_destroy_label
Clears the veriexec slot data in a vnode label.
mpo_vnode_init_label
Initializes the veriexec slot data in a vnode label.
The fingerprint status for the file is stored in the veriexec slot data.
* Some sysctls, under security.mac.veriexec, for setting debug level,
fetching the current state in a human-readable form, and dumping the
fingerprint database are implemented.
* The MAC policy implementation source file also contains some utility
functions.
* A set of fingerprint modules for the following cryptographic hash
algorithms:
RIPEMD-160, SHA1, SHA2-256, SHA2-384, SHA2-512
* Loadable module builds for MAC/veriexec and fingerprint modules.
WARNING: Using veriexec with NFS (or other network-based) file systems is
not recommended as one cannot guarantee the integrity of the files
served, nor the uniqueness of file system identifiers which are
used as key in the meta-data store.
Reviewed by: ian, jtl
Obtained from: Juniper Networks, Inc.
Differential Revision: https://reviews.freebsd.org/D8554
ccddba56e4