VERIEXEC(9) | Kernel Developer's Manual | VERIEXEC(9) |
veriexec
—
#include <sys/verified_exec.h>
void
veriexec_init
(void);
bool
veriexec_lookup
(struct
vnode *vp);
int
veriexec_verify
(struct
lwp *l, struct vnode
*vp, const u_char
*name, int flag,
bool *found);
void
veriexec_purge
(struct
vnode *vp);
int
veriexec_fpops_add
(const
char *fp_type, size_t
hash_len, size_t
ctx_size,
veriexec_fpop_init_t
init,
veriexec_fpop_update_t
update,
veriexec_fpop_final_t
final);
int
veriexec_file_add
(struct
lwp *l, prop_dictionary_t
dict);
int
veriexec_file_delete
(struct
lwp *l, struct vnode
*vp);
int
veriexec_table_delete
(struct
lwp *l, struct mount
*mp);
int
veriexec_flush
(struct
lwp *l);
int
veriexec_openchk
(struct
lwp *l, struct vnode
*vp, const char
*path, int
fmode);
int
veriexec_renamechk
(struct
lwp *l, struct vnode
*fromvp, const char
*fromname, struct vnode
*tovp, const char
*toname);
int
veriexec_removechk
(struct
lwp *l, struct vnode
*vp, const char
*name);
int
veriexec_unmountchk
(struct
mount *mp);
int
veriexec_convert
(struct
vnode *vp,
prop_dictionary_t
rdict);
int
veriexec_dump
(struct
lwp *l, prop_array_t
rarray);
veriexec
is the KPI for Veriexec, the
NetBSD in-kernel file integrity subsystem. It is
responsible for managing the supported hashing algorithms, fingerprint
calculation and comparison, file monitoring tables, and relevant hooks to
enforce the Veriexec policy.
veriexec_init
(void)veriexec_lookup
(vp)true
if it is,
or false
otherwise.veriexec_verify
(l,
vp, name,
flag, found)VERIEXEC_DIRECT
VERIEXEC_INDIRECT
VERIEXEC_FILE
l is the LWP for the request context.
An optional argument, found, is a pointer to a boolean indicating whether an entry for the file was found in the Veriexec tables.
veriexec_purge
(vp)veriexec_fpops_add
(fp_type,
hash_len, ctx_size,
init, update,
final)veriexec_file_add
(l,
dict)dict is expected to have the following:
Name | Type | Purpose |
file | string | filename |
entry-type | uint8 | entry type flags (see veriexec(4)) |
fp-type | string | fingerprint hashing algorithm |
fp | data | the fingerprint |
veriexec_file_delete
(l,
vp)veriexec_table_delete
(l,
mp)veriexec_flush
(l)veriexec_openchk
(l,
vp, path,
fmode)l is the LWP opening the file,
vp is a vnode for the file being opened as
returned from namei(9). If
NULL
, the file is being created.
path is the pathname for the file (not necessarily
a full path), and fmode are the mode bits with
which the file was opened.
veriexec_renamechk
(l,
fromvp, fromname,
tovp, toname)fromvp and fromname are the vnode and filename of the file being renamed. tovp and toname are the vnode and filename of the target file. l is the LWP renaming the file.
Depending on the strict level,
veriexec
will either track changes appropriately
or prevent the rename.
veriexec_removechk
(l,
vp, name)vp is the vnode of the file being removed, and name is the filename. l is the LWP removing the file,
Depending on the strict level,
veriexec
will either clean-up after the file or
prevent its removal.
veriexec_unmountchk
(mp)veriexec_convert
(vp,
rdict)Name | Type | Purpose |
entry-type | uint8 | entry type flags (see veriexec(4)) |
status | uint8 | entry status (see below) |
fp-type | string | fingerprint hashing algorithm |
fp | data | the fingerprint |
The “status” can be one of the following:
Status | Meaning |
FINGERPRINT_NOTEVAL | not evaluated |
FINGERPRINT_VALID | fingerprint match |
FINGERPRINT_MISMATCH | fingerprint mismatch |
If no entry was found, ENOENT
is
returned. Otherwise, zero.
veriexec_dump
(l,
rarray)Each element in rarray is a dictionary
with the same elements as filled by
veriexec_convert
(), with an additional field,
“file”, containing the filename.
Path | Purpose |
src/sys/dev/veriexec.c | driver for userland communication |
src/sys/sys/verified_exec.h | shared (userland/kernel) header file |
src/sys/kern/kern_veriexec.c | subsystem code |
src/sys/kern/vfs_syscalls.c | rename, remove, and unmount policies |
src/sys/kern/vfs_vnops.c | regular file access policy |
veriexec
, there is no way to track on-disk changes.
While it is possible to minimize the effect by evaluating the file's
fingerprint on each access without caching the result, a problem arises when a
file is overwritten after its fingerprint has been evaluated and it is running
on the local host.
An attacker could potentially overwrite the file contents in the remote host at that point, and force a flush on the local host, resulting in paging in of the files from the disk, introducing malicious code into a supposedly safe address space.
There is a fix for this issue, however due to dependencies on other work that is still in progress it has not been committed yet.
veriexec
cannot track the same
on-disk file across multiple layers of overlay file-systems. Therefore, you
cannot expect changes to files on overlay mounts will be detected simply
because the underlying mount is monitored by veriexec
.
A workaround for this issue is listing all files, under all mounts, you want monitored in the signature file.
December 9, 2015 | NetBSD 9.2 |