[PATCH v3 3/3] audit: add OPENAT2 record to list how

Richard Guy Briggs
2021-04-30T20:37:00Z

Since the openat2(2) syscall uses a struct open_how pointer to communicate
its parameters they are not usefully recorded by the audit SYSCALL record's
four existing arguments.

Add a new audit record type OPENAT2 that reports the parameters in its
third argument, struct open_how with fields oflag, mode and resolve.

The new record in the context of an event would look like:
time->Wed Mar 17 16:28:53 2021
type=PROCTITLE msg=audit(1616012933.531:184): proctitle=73797363616C6C735F66696C652F6F70656E617432002F746D702F61756469742D7465737473756974652D737641440066696C652D6F70656E617432
type=PATH msg=audit(1616012933.531:184): item=1 name="file-openat2" inode=29 dev=00:1f mode=0100600 ouid=0 ogid=0 rdev=00:00 obj=unconfined_u:object_r:user_tmp_t:s0 nametype=CREATE cap_fp=0 cap_fi=0 cap_fe=0 cap_fver=0 cap_frootid=0
type=PATH msg=audit(1616012933.531:184): item=0 name="/root/rgb/git/audit-testsuite/tests" inode=25 dev=00:1f mode=040700 ouid=0 ogid=0 rdev=00:00 obj=unconfined_u:object_r:user_tmp_t:s0 nametype=PARENT cap_fp=0 cap_fi=0 cap_fe=0 cap_fver=0 cap_frootid=0
type=CWD msg=audit(1616012933.531:184): cwd="/root/rgb/git/audit-testsuite/tests"
type=OPENAT2 msg=audit(1616012933.531:184): oflag=0100302 mode=0600 resolve=0xa
type=SYSCALL msg=audit(1616012933.531:184): arch=c000003e syscall=437 success=yes exit=4 a0=3 a1=7ffe315f1c53 a2=7ffe315f1550 a3=18 items=2 ppid=528 pid=540 auid=0 uid=0 gid=0 euid=0 suid=0 fsuid=0 egid=0 sgid=0 fsgid=0 tty=ttyS0 ses=1 comm="openat2" exe="/root/rgb/git/audit-testsuite/tests/syscalls_file/openat2" subj=unconfined_u:unconfined_r:unconfined_t:s0-s0:c0.c1023 key="testsuite-1616012933-bjAUcEPO"

Signed-off-by: Richard Guy Briggs <rgb@redhat.com>
---
fs/open.c | 2 ++
include/linux/audit.h | 10 ++++++++++
include/uapi/linux/audit.h | 1 +
kernel/audit.h | 2 ++
kernel/auditsc.c | 18 +++++++++++++++++-
5 files changed, 32 insertions(+), 1 deletion(-)

diff --git a/fs/open.c b/fs/open.c
index e53af13b5835..2a15bec0cf6d 100644
--- a/fs/open.c
+++ b/fs/open.c
@@ -1235,6 +1235,8 @@ SYSCALL_DEFINE4(openat2, int, dfd, const char __user *, filename,
if (err)
return err;

+ audit_openat2_how(&tmp);
+
/* O_LARGEFILE is only allowed for non-O_PATH. */
if (!(tmp.flags & O_PATH) && force_o_largefile())
tmp.flags |= O_LARGEFILE;
diff --git a/include/linux/audit.h b/include/linux/audit.h
index 1137df4d4171..32095e1f5bac 100644
--- a/include/linux/audit.h
+++ b/include/linux/audit.h
@@ -399,6 +399,7 @@ extern int __audit_log_bprm_fcaps(struct linux_binprm *bprm,
const struct cred *old);
extern void __audit_log_capset(const struct cred *new, const struct cred *old);
extern void __audit_mmap_fd(int fd, int flags);
+extern void __audit_openat2_how(struct open_how *how);
extern void __audit_log_kern_module(char *name);
extern void __audit_fanotify(unsigned int response);
extern void __audit_tk_injoffset(struct timespec64 offset);
@@ -495,6 +496,12 @@ static inline void audit_mmap_fd(int fd, int flags)
__audit_mmap_fd(fd, flags);
}

+static inline void audit_openat2_how(struct open_how *how)
+{
+ if (unlikely(!audit_dummy_context()))
+ __audit_openat2_how(how);
+}
+
static inline void audit_log_kern_module(char *name)
{
if (!audit_dummy_context())
@@ -646,6 +653,9 @@ static inline void audit_log_capset(const struct cred *new,
static inline void audit_mmap_fd(int fd, int flags)
{ }

+static inline void audit_openat2_how(struct open_how *how)
+{ }
+
static inline void audit_log_kern_module(char *name)
{
}
diff --git a/include/uapi/linux/audit.h b/include/uapi/linux/audit.h
index cd2d8279a5e4..67aea2370c6d 100644
--- a/include/uapi/linux/audit.h
+++ b/include/uapi/linux/audit.h
@@ -118,6 +118,7 @@
#define AUDIT_TIME_ADJNTPVAL 1333 /* NTP value adjustment */
#define AUDIT_BPF 1334 /* BPF subsystem */
#define AUDIT_EVENT_LISTENER 1335 /* Task joined multicast read socket */
+#define AUDIT_OPENAT2 1336 /* Record showing openat2 how args */

#define AUDIT_AVC 1400 /* SE Linux avc denial or grant */
#define AUDIT_SELINUX_ERR 1401 /* Internal SE Linux Errors */
diff --git a/kernel/audit.h b/kernel/audit.h
index 1522e100fd17..c5af17905976 100644
--- a/kernel/audit.h
+++ b/kernel/audit.h
@@ -11,6 +11,7 @@
#include <linux/skbuff.h>
#include <uapi/linux/mqueue.h>
#include <linux/tty.h>
+#include <uapi/linux/openat2.h> // struct open_how

/* AUDIT_NAMES is the number of slots we reserve in the audit_context
* for saving names from getname(). If we get more names we will allocate
@@ -185,6 +186,7 @@ struct audit_context {
int fd;
int flags;
} mmap;
+ struct open_how openat2;
struct {
int argc;
} execve;
diff --git a/kernel/auditsc.c b/kernel/auditsc.c
index 27c747e0d5ab..2e9a1eea8b12 100644
--- a/kernel/auditsc.c
+++ b/kernel/auditsc.c
@@ -76,7 +76,7 @@
#include <linux/fsnotify_backend.h>
#include <uapi/linux/limits.h>
#include <uapi/linux/netfilter/nf_tables.h>
-#include <uapi/linux/openat2.h>
+#include <uapi/linux/openat2.h> // struct open_how

#include "audit.h"

@@ -1310,6 +1310,12 @@ static void show_special(struct audit_context *context, int *call_panic)
audit_log_format(ab, "fd=%d flags=0x%x", context->mmap.fd,
context->mmap.flags);
break;
+ case AUDIT_OPENAT2:
+ audit_log_format(ab, "oflag=0%llo mode=0%llo resolve=0x%llx",
+ context->openat2.flags,
+ context->openat2.mode,
+ context->openat2.resolve);
+ break;
case AUDIT_EXECVE:
audit_log_execve_info(context, &ab);
break;
@@ -2529,6 +2535,16 @@ void __audit_mmap_fd(int fd, int flags)
context->type = AUDIT_MMAP;
}

+void __audit_openat2_how(struct open_how *how)
+{
+ struct audit_context *context = audit_context();
+
+ context->openat2.flags = how->flags;
+ context->openat2.mode = how->mode;
+ context->openat2.resolve = how->resolve;
+ context->type = AUDIT_OPENAT2;
+}
+
void __audit_log_kern_module(char *name)
{
struct audit_context *context = audit_context();
--
2.27.0