RE: A question about the directory watch in audit_tree.c in kernel

zhangxiliang
2008-05-21T01:47:59Z

Sorry, I think my idea may be not express correctly. A example as follows:
1, mkdir test
2, touch test.c
3, auditctl -w /home/test -k 11
4, auditctl -w /home/test.c -k 11

The audit-log as follows:

node=mydomain type=CONFIG_CHANGE msg=audit(1211331237.488:307618): auid=0
subj=root:system_r:auditctl_t:s0-s0:c0.c1023 op=add rule key="11" list=4 res=1
node=mydomain type=CONFIG_CHANGE msg=audit(1211331242.045:307619): auid=0
subj=root:system_r:auditctl_t:s0-s0:c0.c1023 op=add rule key="11" list=4 res=1

==============>record the add rule operation

node=mydomain type=SYSCALL msg=audit(1211331247.517:307620): arch=40000003
syscall=38 success=yes exit=0 a0=bf974b80 a1=bf974b85 a2=805a8fc a3=bf974b85
items=4 ppid=19616 pid=19895 auid=0 uid=0 gid=0 euid=0 suid=0 fsuid=0 egid=0
sgid=0 fsgid=0 tty=pts3 ses=2689 comm="mv" exe="/bin/mv"
subj=root:system_r:unconfined_t:s0-s0:c0.c1023 key="11"
node=mydomain type=CWD msg=audit(1211331247.517:307620): cwd="/home"
node=mydomain type=PATH msg=audit(1211331247.517:307620): item=0 name="/home"
inode=1532577 dev=03:06 mode=040755 ouid=0 ogid=0 rdev=00:00
obj=system_u:object_r:home_root_t:s0
node=mydomain type=PATH msg=audit(1211331247.517:307620): item=1 name="/home"
inode=1532577 dev=03:06 mode=040755 ouid=0 ogid=0 rdev=00:00
obj=system_u:object_r:home_root_t:s0
node=mydomain type=PATH msg=audit(1211331247.517:307620): item=2 name="test"
inode=1535099 dev=03:06 mode=040755 ouid=0 ogid=0 rdev=00:00
obj=root:object_r:user_home_dir_t:s0
node=mydomain type=PATH msg=audit(1211331247.517:307620): item=3 name="test1"
inode=1535099 dev=03:06 mode=040755 ouid=0 ogid=0 rdev=00:00
obj=root:object_r:user_home_dir_t:s0

===============>record the directory changed(the information supply by kernel
funtion "audit_syscall_exit")

node=mydomain type=CONFIG_CHANGE msg=audit(1211331254.160:307621): op=updated
rules specifying path="/home/test.c" with dev=4294967295 ino=4294967295
list=778332531 res=1
node=mydomain type=SYSCALL msg=audit(1211331254.160:307622): arch=40000003
syscall=38 success=yes exit=0 a0=bff86b7c a1=bff86b83 a2=805a8fc a3=0 items=4
ppid=19616 pid=19897 auid=0 uid=0 gid=0 euid=0 suid=0 fsuid=0 egid=0 sgid=0
fsgid=0 tty=pts3 ses=2689 comm="mv" exe="/bin/mv"
subj=root:system_r:unconfined_t:s0-s0:c0.c1023 key="11"

===============>record the files changed status(the information supply by
kernel inotify hook funtion "fsnotify_move")

node=mydomain type=CWD msg=audit(1211331254.160:307622): cwd="/home"
node=mydomain type=PATH msg=audit(1211331254.160:307622): item=0 name="/home"
inode=1532577 dev=03:06 mode=040755 ouid=0 ogid=0 rdev=00:00
obj=system_u:object_r:home_root_t:s0
node=mydomain type=PATH msg=audit(1211331254.160:307622): item=1 name="/home"
inode=1532577 dev=03:06 mode=040755 ouid=0 ogid=0 rdev=00:00
obj=system_u:object_r:home_root_t:s0
node=mydomain type=PATH msg=audit(1211331254.160:307622): item=2 name="test.c"
inode=1535101 dev=03:06 mode=0100644 ouid=0 ogid=0 rdev=00:00
obj=root:object_r:home_root_t:s0
node=mydomain type=PATH msg=audit(1211331254.160:307622): item=3
name="test1.c" inode=1535101 dev=03:06 mode=0100644 ouid=0 ogid=0 rdev=00:00
obj=root:object_r:home_root_t:s0

=================>record the files changed(the information supply by kernel
funtion "audit_syscall_exit")

My question is why no information will be output by kernel hook funtion?(It
only has some information by "audit_syscall_exit" ) when watch the directory.

Correct me if I am wrong, I think when watch a directory, kernel-audit can
also supply more information by kernel hook funtion as audit files watch and
inotify_user.

Compare the kernel code as file watch and directory watch:

in auditfilter.c:
/* Update watch data in audit rules based on inotify events. */
void audit_handle_ievent(struct inotify_watch *i_watch, u32 wd, u32 mask,
u32 cookie, const char *dname, struct inode *inode)
{
struct audit_parent *parent;

parent = container_of(i_watch, struct audit_parent, wdata);

if (mask & (IN_CREATE|IN_MOVED_TO) && inode)
audit_update_watch(parent, dname, inode->i_sb->s_dev,
inode->i_ino, 0);
else if (mask & (IN_DELETE|IN_MOVED_FROM))
audit_update_watch(parent, dname, (dev_t)-1, (unsigned long)-1, 1);
/* inotify automatically removes the watch and sends IN_IGNORED */
else if (mask & (IN_DELETE_SELF|IN_UNMOUNT))
audit_remove_parent_watches(parent);
/* inotify does not remove the watch, so remove it manually */
else if(mask & IN_MOVE_SELF) {
audit_remove_parent_watches(parent);
inotify_remove_watch_locked(audit_ih, i_watch);
} else if (mask & IN_IGNORED)
put_inotify_watch(i_watch);
}

in audit_tree.c:
static void handle_event(struct inotify_watch *watch, u32 wd, u32 mask,
u32 cookie, const char *dname, struct inode *inode)
{
struct audit_chunk *chunk = container_of(watch, struct audit_chunk, watch);

if (mask & IN_IGNORED) {
evict_chunk(chunk);
put_inotify_watch(watch);
}
}

I can found that "handle_event" in audit_tree.c has no any code with mask
"IN_CREATE, IN_MOVED_TO, IN_DELETE, IN_MOVED_FROM, IN_DELETE_SELF, IN_UNMOUNT,
IN_MOVE_SELF".
So no information will be output by kernel hook funtion when watch a
directory.

--
Regards
Zhang Xiliang

________________________________

From: Kevin Boyce [mailto:kevin.boyce@ngc.com]
Sent: Tuesday, May 20, 2008 8:06 PM
To: zhangxiliang
Cc: 'Steve Grubb'; dwmw2@infradead.org; linux-audit@redhat.com
Subject: Re: A question about the directory watch in audit_tree.c in kernel

Correct me if I am wrong, but in doing the auditctl -w /home, the only thing
that is being audited is the inode entry for the directory itself. You need
to construct an explicit list of each file you want to watch. You can do this
rather easily with a combination of find and awk.

Regards.
Kevin

On Tue, 2008-05-20 at 09:11 +0800, zhangxiliang wrote:

HI,
When I use "auditctl -w /home" to watch a directory, nothing about
the
directory changed can be output.

I found the "audit tree handle_event" in audit_tree.c in kernel. It
implements as follows:

static void handle_event(struct inotify_watch *watch, u32 wd, u32
mask,
u32 cookie, const char *dname, struct inode
*inode)
{
struct audit_chunk *chunk = container_of(watch, struct audit_chunk,
watch);

if (mask & IN_IGNORED) {
evict_chunk(chunk);
put_inotify_watch(watch);
}
}

In "handle_event", the mask can be "IN_MOVED_FROM", "IN_MOVED_TO",
"IN_DELETE_SELF", "IN_IGNORED" and so on.
Why it only deals with the mask " IN_IGNORED" and ignores the
other
mask?

--
Regards
Zhang Xiliang
--------------------------------------------------
Zhang Xiliang
Development Dept.I
Nanjing Fujitsu Nanda Software Tech. Co., Ltd.(FNST) 8/F., Civil Defense
Building, No.189 Guangzhou Road, Nanjing, 210029, China
TEL: +86+25-86630566-838
COINS: 79955-838
FAX: +86+25-83317685
MAIL: zhangxiliang@cn.fujitsu.com
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