Hello, The fanotify interface allows user space daemons to make access control decisions. Under common criteria requirements, we need to optionally record decisions based on policy. This patch adds a bit mask, FAN_AUDIT, that a user space daemon can 'or' into the response decision which will tell the kernel that it made a decision and record it. It would be used something like this in user space code: response.response = FAN_DENY | FAN_AUDIT; write(fd, &response, sizeof(struct fanotify_response)); When the syscall ends, the audit system will record the decision as a AUDIT_FANOTIFY auxiliary record to denote that the reason this event occurred is the result of an access control decision from fanotify rather than DAC or MAC policy. A sample event looks like this: type=PATH msg=audit(1504310584.332:290): item=0 name="./evil-ls" inode=1319561 dev=fc:03 mode=0100755 ouid=1000 ogid=1000 rdev=00:00 obj=unconfined_u:object_r:user_home_t:s0 nametype=NORMAL type=CWD msg=audit(1504310584.332:290): cwd="/home/sgrubb" type=SYSCALL msg=audit(1504310584.332:290): arch=c000003e syscall=2 success=no exit=-1 a0=32cb3fca90 a1=0 a2=43 a3=8 items=1 ppid=901 pid=959 auid=1000 uid=1000 gid=1000 euid=1000 suid=1000 fsuid=1000 egid=1000 sgid=1000 fsgid=1000 tty=pts1 ses=3 comm="bash" exe="/usr/bin/bash" subj=unconfined_u:unconfined_r:unconfined_t: s0-s0:c0.c1023 key=(null) type=FANOTIFY msg=audit(1504310584.332:290): resp=2 Prior to using the audit flag, the developer needs to call fanotify_init or'ing in FAN_ENABLE_AUDIT to ensure that the kernel supports auditing. The calling process must also have the CAP_AUDIT_WRITE capability. * v5 remove ifdef around code block and == 0 from boolean check * v6 update adds empty inline audit_fanotify function for when CONFIG_AUDITSYSCALL is not defined. * v7 rename audit_enabled variable to "audit" to avoid symbol collision Signed-off-by: sgrubb <sgrubb(a)redhat.com&gt; Reviewed-by: Amir Goldstein <amir73il(a)gmail.com&gt; --- fs/notify/fanotify/fanotify.c | 8 +++++++- fs/notify/fanotify/fanotify_user.c | 16 +++++++++++++++- fs/notify/fdinfo.c | 3 +++ include/linux/audit.h | 10 ++++++++++ include/linux/fsnotify_backend.h | 1 + include/uapi/linux/audit.h | 1 + include/uapi/linux/fanotify.h | 3 +++ kernel/auditsc.c | 6 ++++++ 8 files changed, 46 insertions(+), 2 deletions(-) diff --git a/fs/notify/fanotify/fanotify.c b/fs/notify/fanotify/fanotify.c index 2fa99ae..1968d21 100644 --- a/fs/notify/fanotify/fanotify.c +++ b/fs/notify/fanotify/fanotify.c @@ -9,6 +9,7 @@ #include <linux/sched/user.h> #include <linux/types.h> #include <linux/wait.h> +#include <linux/audit.h> #include "fanotify.h" @@ -78,7 +79,7 @@ static int fanotify_get_response(struct fsnotify_group *group, fsnotify_finish_user_wait(iter_info); out: /* userspace responded, convert to something usable */ - switch (event->response) { + switch (event->response & ~FAN_AUDIT) { case FAN_ALLOW: ret = 0; break; @@ -86,6 +87,11 @@ static int fanotify_get_response(struct fsnotify_group *group, default: ret = -EPERM; } + + /* Check if the response should be audited */ + if (event->response & FAN_AUDIT) + audit_fanotify(event->response & ~FAN_AUDIT); + event->response = 0; pr_debug("%s: group=%p event=%p about to return ret=%d\n", __func__, diff --git a/fs/notify/fanotify/fanotify_user.c b/fs/notify/fanotify/fanotify_user.c index 907a481..ea3c458 100644 --- a/fs/notify/fanotify/fanotify_user.c +++ b/fs/notify/fanotify/fanotify_user.c @@ -179,7 +179,7 @@ static int process_access_response(struct fsnotify_group *group, * userspace can send a valid response or we will clean it up after the * timeout */ - switch (response) { + switch (response & ~FAN_AUDIT) { case FAN_ALLOW: case FAN_DENY: break; @@ -190,6 +190,9 @@ static int process_access_response(struct fsnotify_group *group, if (fd < 0) return -EINVAL; + if ((response & FAN_AUDIT) && !group->fanotify_data.audit) + return -EINVAL; + event = dequeue_event(group, fd); if (!event) return -ENOENT; @@ -721,7 +724,11 @@ SYSCALL_DEFINE2(fanotify_init, unsigned int, flags, unsigned int, event_f_flags) if (!capable(CAP_SYS_ADMIN)) return -EPERM; +#ifdef CONFIG_AUDITSYSCALL + if (flags & ~(FAN_ALL_INIT_FLAGS | FAN_ENABLE_AUDIT)) +#else if (flags & ~FAN_ALL_INIT_FLAGS) +#endif return -EINVAL; if (event_f_flags & ~FANOTIFY_INIT_ALL_EVENT_F_BITS) @@ -805,6 +812,13 @@ SYSCALL_DEFINE2(fanotify_init, unsigned int, flags, unsigned int, event_f_flags) group->fanotify_data.max_marks = FANOTIFY_DEFAULT_MAX_MARKS; } + if (flags & FAN_ENABLE_AUDIT) { + fd = -EPERM; + if (!capable(CAP_AUDIT_WRITE)) + goto out_destroy_group; + group->fanotify_data.audit = true; + } + fd = anon_inode_getfd("[fanotify]", &fanotify_fops, group, f_flags); if (fd < 0) goto out_destroy_group; diff --git a/fs/notify/fdinfo.c b/fs/notify/fdinfo.c index dd63aa9..ed311e3 100644 --- a/fs/notify/fdinfo.c +++ b/fs/notify/fdinfo.c @@ -156,6 +156,9 @@ void fanotify_show_fdinfo(struct seq_file *m, struct file *f) if (group->fanotify_data.max_marks == UINT_MAX) flags |= FAN_UNLIMITED_MARKS; + if (group->fanotify_data.audit) + flags |= FAN_ENABLE_AUDIT; + seq_printf(m, "fanotify flags:%x event-flags:%x\n", flags, group->fanotify_data.f_flags); diff --git a/include/linux/audit.h b/include/linux/audit.h index 2150bdc..9095617 100644 --- a/include/linux/audit.h +++ b/include/linux/audit.h @@ -360,6 +360,7 @@ extern int __audit_log_bprm_fcaps(struct linux_binprm *bprm, 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_log_kern_module(char *name); +extern void __audit_fanotify(unsigned int response); static inline void audit_ipc_obj(struct kern_ipc_perm *ipcp) { @@ -456,6 +457,12 @@ static inline void audit_log_kern_module(char *name) __audit_log_kern_module(name); } +static inline void audit_fanotify(unsigned int response) +{ + if (!audit_dummy_context()) + __audit_fanotify(response); +} + extern int audit_n_rules; extern int audit_signals; #else /* CONFIG_AUDITSYSCALL */ @@ -572,6 +579,9 @@ static inline void audit_log_kern_module(char *name) { } +static inline void audit_fanotify(unsigned int response) +{ } + static inline void audit_ptrace(struct task_struct *t) { } #define audit_n_rules 0 diff --git a/include/linux/fsnotify_backend.h b/include/linux/fsnotify_backend.h index c6c6931..f4131f2 100644 --- a/include/linux/fsnotify_backend.h +++ b/include/linux/fsnotify_backend.h @@ -190,6 +190,7 @@ struct fsnotify_group { int f_flags; unsigned int max_marks; struct user_struct *user; + bool audit; } fanotify_data; #endif /* CONFIG_FANOTIFY */ }; diff --git a/include/uapi/linux/audit.h b/include/uapi/linux/audit.h index 0714a66..221f8b7 100644 --- a/include/uapi/linux/audit.h +++ b/include/uapi/linux/audit.h @@ -112,6 +112,7 @@ #define AUDIT_FEATURE_CHANGE 1328 /* audit log listing feature changes */ #define AUDIT_REPLACE 1329 /* Replace auditd if this packet unanswerd */ #define AUDIT_KERN_MODULE 1330 /* Kernel Module events */ +#define AUDIT_FANOTIFY 1331 /* Fanotify access decision */ #define AUDIT_AVC 1400 /* SE Linux avc denial or grant */ #define AUDIT_SELINUX_ERR 1401 /* Internal SE Linux Errors */ diff --git a/include/uapi/linux/fanotify.h b/include/uapi/linux/fanotify.h index 030508d..5dda19a 100644 --- a/include/uapi/linux/fanotify.h +++ b/include/uapi/linux/fanotify.h @@ -35,6 +35,7 @@ #define FAN_UNLIMITED_QUEUE 0x00000010 #define FAN_UNLIMITED_MARKS 0x00000020 +#define FAN_ENABLE_AUDIT 0x00000040 #define FAN_ALL_INIT_FLAGS (FAN_CLOEXEC | FAN_NONBLOCK | \ FAN_ALL_CLASS_BITS | FAN_UNLIMITED_QUEUE |\ @@ -99,6 +100,8 @@ struct fanotify_response { /* Legit userspace responses to a _PERM event */ #define FAN_ALLOW 0x01 #define FAN_DENY 0x02 +#define FAN_AUDIT 0x10 /* Bit mask to create audit record for result */ + /* No fd set in event */ #define FAN_NOFD -1 diff --git a/kernel/auditsc.c b/kernel/auditsc.c index 3260ba2..e046de8 100644 --- a/kernel/auditsc.c +++ b/kernel/auditsc.c @@ -2390,6 +2390,12 @@ void __audit_log_kern_module(char *name) context->type = AUDIT_KERN_MODULE; } +void __audit_fanotify(unsigned int response) +{ + audit_log(current->audit_context, GFP_KERNEL, + AUDIT_FANOTIFY, "resp=%u", response); +} + static void audit_log_task(struct audit_buffer *ab) { kuid_t auid, uid; -- 2.9.5