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AUDIT: Allow filtering of user messages
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Turn the field from a bitmask to an enumeration and add a list to allow 
filtering of messages generated by userspace. We also define a list for 
file system watches in anticipation of that feature.

Signed-off-by: David Woodhouse <dwmw2@infradead.org>
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David Woodhouse committed Jun 19, 2005
1 parent 0107b3c commit 0f45aa1
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Showing 3 changed files with 85 additions and 58 deletions.
15 changes: 11 additions & 4 deletions include/linux/audit.h
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Original file line number Diff line number Diff line change
Expand Up @@ -75,10 +75,15 @@
#define AUDIT_KERNEL 2000 /* Asynchronous audit record. NOT A REQUEST. */

/* Rule flags */
#define AUDIT_PER_TASK 0x01 /* Apply rule at task creation (not syscall) */
#define AUDIT_AT_ENTRY 0x02 /* Apply rule at syscall entry */
#define AUDIT_AT_EXIT 0x04 /* Apply rule at syscall exit */
#define AUDIT_PREPEND 0x10 /* Prepend to front of list */
#define AUDIT_FILTER_USER 0x00 /* Apply rule to user-generated messages */
#define AUDIT_FILTER_TASK 0x01 /* Apply rule at task creation (not syscall) */
#define AUDIT_FILTER_ENTRY 0x02 /* Apply rule at syscall entry */
#define AUDIT_FILTER_WATCH 0x03 /* Apply rule to file system watches */
#define AUDIT_FILTER_EXIT 0x04 /* Apply rule at syscall exit */

#define AUDIT_NR_FILTERS 5

#define AUDIT_FILTER_PREPEND 0x10 /* Prepend to front of list */

/* Rule actions */
#define AUDIT_NEVER 0 /* Do not build context if rule matches */
Expand Down Expand Up @@ -230,6 +235,7 @@ extern int audit_socketcall(int nargs, unsigned long *args);
extern int audit_sockaddr(int len, void *addr);
extern int audit_avc_path(struct dentry *dentry, struct vfsmount *mnt);
extern void audit_signal_info(int sig, struct task_struct *t);
extern int audit_filter_user(struct task_struct *tsk, int type);
#else
#define audit_alloc(t) ({ 0; })
#define audit_free(t) do { ; } while (0)
Expand All @@ -246,6 +252,7 @@ extern void audit_signal_info(int sig, struct task_struct *t);
#define audit_sockaddr(len, addr) ({ 0; })
#define audit_avc_path(dentry, mnt) ({ 0; })
#define audit_signal_info(s,t) do { ; } while (0)
#define audit_filter_user(struct ({ 1; })
#endif

#ifdef CONFIG_AUDIT
Expand Down
36 changes: 20 additions & 16 deletions kernel/audit.c
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Original file line number Diff line number Diff line change
Expand Up @@ -107,13 +107,6 @@ static struct sk_buff_head audit_skb_queue;
static struct task_struct *kauditd_task;
static DECLARE_WAIT_QUEUE_HEAD(kauditd_wait);

/* There are three lists of rules -- one to search at task creation
* time, one to search at syscall entry time, and another to search at
* syscall exit time. */
static LIST_HEAD(audit_tsklist);
static LIST_HEAD(audit_entlist);
static LIST_HEAD(audit_extlist);

/* The netlink socket is only to be read by 1 CPU, which lets us assume
* that list additions and deletions never happen simultaneously in
* auditsc.c */
Expand Down Expand Up @@ -376,6 +369,7 @@ static int audit_receive_msg(struct sk_buff *skb, struct nlmsghdr *nlh)
u16 msg_type = nlh->nlmsg_type;
uid_t loginuid; /* loginuid of sender */
struct audit_sig_info sig_data;
struct task_struct *tsk;

err = audit_netlink_ok(NETLINK_CB(skb).eff_cap, msg_type);
if (err)
Expand Down Expand Up @@ -435,15 +429,25 @@ static int audit_receive_msg(struct sk_buff *skb, struct nlmsghdr *nlh)
break;
case AUDIT_USER:
case AUDIT_FIRST_USER_MSG...AUDIT_LAST_USER_MSG:
ab = audit_log_start(NULL, msg_type);
if (!ab)
break; /* audit_panic has been called */
audit_log_format(ab,
"user pid=%d uid=%u auid=%u"
" msg='%.1024s'",
pid, uid, loginuid, (char *)data);
audit_set_pid(ab, pid);
audit_log_end(ab);
read_lock(&tasklist_lock);
tsk = find_task_by_pid(pid);
if (tsk)
get_task_struct(tsk);
read_unlock(&tasklist_lock);
if (!tsk)
return -ESRCH;

if (audit_filter_user(tsk, msg_type)) {
ab = audit_log_start(NULL, msg_type);
if (ab) {
audit_log_format(ab,
"user pid=%d uid=%u auid=%u msg='%.1024s'",
pid, uid, loginuid, (char *)data);
audit_set_pid(ab, pid);
audit_log_end(ab);
}
}
put_task_struct(tsk);
break;
case AUDIT_ADD:
case AUDIT_DEL:
Expand Down
92 changes: 54 additions & 38 deletions kernel/auditsc.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -167,9 +167,16 @@ struct audit_context {
/* There are three lists of rules -- one to search at task creation
* time, one to search at syscall entry time, and another to search at
* syscall exit time. */
static LIST_HEAD(audit_tsklist);
static LIST_HEAD(audit_entlist);
static LIST_HEAD(audit_extlist);
static struct list_head audit_filter_list[AUDIT_NR_FILTERS] = {
LIST_HEAD_INIT(audit_filter_list[0]),
LIST_HEAD_INIT(audit_filter_list[1]),
LIST_HEAD_INIT(audit_filter_list[2]),
LIST_HEAD_INIT(audit_filter_list[3]),
LIST_HEAD_INIT(audit_filter_list[4]),
#if AUDIT_NR_FILTERS != 5
#error Fix audit_filter_list initialiser
#endif
};

struct audit_entry {
struct list_head list;
Expand Down Expand Up @@ -210,16 +217,15 @@ static int audit_compare_rule(struct audit_rule *a, struct audit_rule *b)
/* Note that audit_add_rule and audit_del_rule are called via
* audit_receive() in audit.c, and are protected by
* audit_netlink_sem. */
static inline int audit_add_rule(struct audit_entry *entry,
struct list_head *list)
static inline void audit_add_rule(struct audit_entry *entry,
struct list_head *list)
{
if (entry->rule.flags & AUDIT_PREPEND) {
entry->rule.flags &= ~AUDIT_PREPEND;
if (entry->rule.flags & AUDIT_FILTER_PREPEND) {
entry->rule.flags &= ~AUDIT_FILTER_PREPEND;
list_add_rcu(&entry->list, list);
} else {
list_add_tail_rcu(&entry->list, list);
}
return 0;
}

static void audit_free_rule(struct rcu_head *head)
Expand All @@ -245,7 +251,7 @@ static inline int audit_del_rule(struct audit_rule *rule,
return 0;
}
}
return -EFAULT; /* No matching rule */
return -ENOENT; /* No matching rule */
}

/* Copy rule from user-space to kernel-space. Called during
Expand All @@ -260,6 +266,8 @@ static int audit_copy_rule(struct audit_rule *d, struct audit_rule *s)
return -1;
if (s->field_count < 0 || s->field_count > AUDIT_MAX_FIELDS)
return -1;
if ((s->flags & ~AUDIT_FILTER_PREPEND) >= AUDIT_NR_FILTERS)
return -1;

d->flags = s->flags;
d->action = s->action;
Expand All @@ -275,23 +283,20 @@ static int audit_copy_rule(struct audit_rule *d, struct audit_rule *s)
int audit_receive_filter(int type, int pid, int uid, int seq, void *data,
uid_t loginuid)
{
u32 flags;
struct audit_entry *entry;
int err = 0;
int i;
unsigned listnr;

switch (type) {
case AUDIT_LIST:
/* The *_rcu iterators not needed here because we are
always called with audit_netlink_sem held. */
list_for_each_entry(entry, &audit_tsklist, list)
audit_send_reply(pid, seq, AUDIT_LIST, 0, 1,
&entry->rule, sizeof(entry->rule));
list_for_each_entry(entry, &audit_entlist, list)
audit_send_reply(pid, seq, AUDIT_LIST, 0, 1,
&entry->rule, sizeof(entry->rule));
list_for_each_entry(entry, &audit_extlist, list)
audit_send_reply(pid, seq, AUDIT_LIST, 0, 1,
&entry->rule, sizeof(entry->rule));
for (i=0; i<AUDIT_NR_FILTERS; i++) {
list_for_each_entry(entry, &audit_filter_list[i], list)
audit_send_reply(pid, seq, AUDIT_LIST, 0, 1,
&entry->rule, sizeof(entry->rule));
}
audit_send_reply(pid, seq, AUDIT_LIST, 1, 1, NULL, 0);
break;
case AUDIT_ADD:
Expand All @@ -301,26 +306,20 @@ int audit_receive_filter(int type, int pid, int uid, int seq, void *data,
kfree(entry);
return -EINVAL;
}
flags = entry->rule.flags;
if (!err && (flags & AUDIT_PER_TASK))
err = audit_add_rule(entry, &audit_tsklist);
if (!err && (flags & AUDIT_AT_ENTRY))
err = audit_add_rule(entry, &audit_entlist);
if (!err && (flags & AUDIT_AT_EXIT))
err = audit_add_rule(entry, &audit_extlist);
listnr = entry->rule.flags & ~AUDIT_FILTER_PREPEND;
audit_add_rule(entry, &audit_filter_list[listnr]);
audit_log(NULL, AUDIT_CONFIG_CHANGE,
"auid=%u added an audit rule\n", loginuid);
break;
case AUDIT_DEL:
flags =((struct audit_rule *)data)->flags;
if (!err && (flags & AUDIT_PER_TASK))
err = audit_del_rule(data, &audit_tsklist);
if (!err && (flags & AUDIT_AT_ENTRY))
err = audit_del_rule(data, &audit_entlist);
if (!err && (flags & AUDIT_AT_EXIT))
err = audit_del_rule(data, &audit_extlist);
audit_log(NULL, AUDIT_CONFIG_CHANGE,
"auid=%u removed an audit rule\n", loginuid);
listnr =((struct audit_rule *)data)->flags & ~AUDIT_FILTER_PREPEND;
if (listnr >= AUDIT_NR_FILTERS)
return -EINVAL;

err = audit_del_rule(data, &audit_filter_list[listnr]);
if (!err)
audit_log(NULL, AUDIT_CONFIG_CHANGE,
"auid=%u removed an audit rule\n", loginuid);
break;
default:
return -EINVAL;
Expand Down Expand Up @@ -454,7 +453,7 @@ static enum audit_state audit_filter_task(struct task_struct *tsk)
enum audit_state state;

rcu_read_lock();
list_for_each_entry_rcu(e, &audit_tsklist, list) {
list_for_each_entry_rcu(e, &audit_filter_list[AUDIT_FILTER_TASK], list) {
if (audit_filter_rules(tsk, &e->rule, NULL, &state)) {
rcu_read_unlock();
return state;
Expand Down Expand Up @@ -490,6 +489,23 @@ static enum audit_state audit_filter_syscall(struct task_struct *tsk,
return AUDIT_BUILD_CONTEXT;
}

int audit_filter_user(struct task_struct *tsk, int type)
{
struct audit_entry *e;
enum audit_state state;

rcu_read_lock();
list_for_each_entry_rcu(e, &audit_filter_list[AUDIT_FILTER_USER], list) {
if (audit_filter_rules(tsk, &e->rule, NULL, &state)) {
rcu_read_unlock();
return state != AUDIT_DISABLED;
}
}
rcu_read_unlock();
return 1; /* Audit by default */

}

/* This should be called with task_lock() held. */
static inline struct audit_context *audit_get_context(struct task_struct *tsk,
int return_valid,
Expand All @@ -504,7 +520,7 @@ static inline struct audit_context *audit_get_context(struct task_struct *tsk,

if (context->in_syscall && !context->auditable) {
enum audit_state state;
state = audit_filter_syscall(tsk, context, &audit_extlist);
state = audit_filter_syscall(tsk, context, &audit_filter_list[AUDIT_FILTER_EXIT]);
if (state == AUDIT_RECORD_CONTEXT)
context->auditable = 1;
}
Expand Down Expand Up @@ -876,7 +892,7 @@ void audit_syscall_entry(struct task_struct *tsk, int arch, int major,

state = context->state;
if (state == AUDIT_SETUP_CONTEXT || state == AUDIT_BUILD_CONTEXT)
state = audit_filter_syscall(tsk, context, &audit_entlist);
state = audit_filter_syscall(tsk, context, &audit_filter_list[AUDIT_FILTER_ENTRY]);
if (likely(state == AUDIT_DISABLED))
return;

Expand Down

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