Re: [PATCH v3] audit: add fields to exclude filter by reusing user filter

From: Paul Moore
Date: Fri Jun 24 2016 - 12:52:17 EST

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On Tue, Jun 21, 2016 at 10:38 PM, Richard Guy Briggs <rgb@xxxxxxxxxx> wrote:
> RFE: add additional fields for use in audit filter exclude rules
> https://github.com/linux-audit/audit-kernel/issues/5
>
> Re-factor and combine audit_filter_type() with audit_filter_user() to
> use audit_filter_user_rules() to enable the exclude filter to
> additionally filter on PID, UID, GID, AUID, LOGINUID_SET, SUBJ_*.
>
> The process of combining the similar audit_filter_user() and
> audit_filter_type() functions, required inverting the meaning and
> including the ALWAYS action of the latter.
>
> Include audit_filter_user_rules() into audit_filter(), removing unneeded
> logic in the process.
>
> Keep the check to quit early if the list is empty.
>
> Signed-off-by: Richard Guy Briggs <rgb@xxxxxxxxxx>
> ---
> v3: pull audit_filter_user_rules() into audit_filter() and simplify
> logic.
>
> v2: combine audit_filter_user() and audit_filter_type() into
> audit_filter().
> ---
> include/linux/audit.h | 2 -
> kernel/audit.c | 4 +-
> kernel/audit.h | 2 +
> kernel/auditfilter.c | 147 ++++++++++++++++++-------------------------------
> 4 files changed, 57 insertions(+), 98 deletions(-)

Look at all those deleted lines ;)

Out of curiosity, what tree is this patch based on? I've tried
applying it on top of the various audit branches as well as Linus'
upstream and v4.6 tags, and I always get a lot of rejects.

> diff --git a/include/linux/audit.h b/include/linux/audit.h
> index 32cdafb..539c1d9 100644
> --- a/include/linux/audit.h
> +++ b/include/linux/audit.h
> @@ -160,8 +160,6 @@ extern void audit_log_task_info(struct audit_buffer *ab,
> extern int audit_update_lsm_rules(void);
>
> /* Private API (for audit.c only) */
> -extern int audit_filter_user(int type);
> -extern int audit_filter_type(int type);
> extern int audit_rule_change(int type, __u32 portid, int seq,
> void *data, size_t datasz);
> extern int audit_list_rules_send(struct sk_buff *request_skb, int seq);
> diff --git a/kernel/audit.c b/kernel/audit.c
> index 384374a..2dfaa19 100644
> --- a/kernel/audit.c
> +++ b/kernel/audit.c
> @@ -914,7 +914,7 @@ static int audit_receive_msg(struct sk_buff *skb, struct nlmsghdr *nlh)
> if (!audit_enabled && msg_type != AUDIT_USER_AVC)
> return 0;
>
> - err = audit_filter_user(msg_type);
> + err = audit_filter(msg_type, AUDIT_FILTER_USER);
> if (err == 1) { /* match or error */
> err = 0;
> if (msg_type == AUDIT_USER_TTY) {
> @@ -1362,7 +1362,7 @@ struct audit_buffer *audit_log_start(struct audit_context *ctx, gfp_t gfp_mask,
> if (audit_initialized != AUDIT_INITIALIZED)
> return NULL;
>
> - if (unlikely(audit_filter_type(type)))
> + if (unlikely(!audit_filter(type, AUDIT_FILTER_TYPE)))
> return NULL;
>
> if (gfp_mask & __GFP_DIRECT_RECLAIM) {
> diff --git a/kernel/audit.h b/kernel/audit.h
> index cbbe6bb..1879f02 100644
> --- a/kernel/audit.h
> +++ b/kernel/audit.h
> @@ -327,6 +327,8 @@ extern pid_t audit_sig_pid;
> extern kuid_t audit_sig_uid;
> extern u32 audit_sig_sid;
>
> +extern int audit_filter(int msgtype, unsigned int listtype);
> +
> #ifdef CONFIG_AUDITSYSCALL
> extern int __audit_signal_info(int sig, struct task_struct *t);
> static inline int audit_signal_info(int sig, struct task_struct *t)
> diff --git a/kernel/auditfilter.c b/kernel/auditfilter.c
> index 96c9a1b..60579ec 100644
> --- a/kernel/auditfilter.c
> +++ b/kernel/auditfilter.c
> @@ -1290,113 +1290,72 @@ int audit_compare_dname_path(const char *dname, const char *path, int parentlen)
> return strncmp(p, dname, dlen);
> }
>
> -static int audit_filter_user_rules(struct audit_krule *rule, int type,
> - enum audit_state *state)
> +int audit_filter(int msgtype, unsigned int listtype)
> {
> - int i;
> -
> - for (i = 0; i < rule->field_count; i++) {
> - struct audit_field *f = &rule->fields[i];
> - pid_t pid;
> - int result = 0;
> - u32 sid;
> -
> - switch (f->type) {
> - case AUDIT_PID:
> - pid = task_pid_nr(current);
> - result = audit_comparator(pid, f->op, f->val);
> - break;
> - case AUDIT_UID:
> - result = audit_uid_comparator(current_uid(), f->op, f->uid);
> - break;
> - case AUDIT_GID:
> - result = audit_gid_comparator(current_gid(), f->op, f->gid);
> - break;
> - case AUDIT_LOGINUID:
> - result = audit_uid_comparator(audit_get_loginuid(current),
> - f->op, f->uid);
> - break;
> - case AUDIT_LOGINUID_SET:
> - result = audit_comparator(audit_loginuid_set(current),
> - f->op, f->val);
> - break;
> - case AUDIT_MSGTYPE:
> - result = audit_comparator(type, f->op, f->val);
> - break;
> - case AUDIT_SUBJ_USER:
> - case AUDIT_SUBJ_ROLE:
> - case AUDIT_SUBJ_TYPE:
> - case AUDIT_SUBJ_SEN:
> - case AUDIT_SUBJ_CLR:
> - if (f->lsm_rule) {
> - security_task_getsecid(current, &sid);
> - result = security_audit_rule_match(sid,
> - f->type,
> - f->op,
> - f->lsm_rule,
> - NULL);
> - }
> - break;
> - }
> -
> - if (result <= 0)
> - return result;
> - }
> - switch (rule->action) {
> - case AUDIT_NEVER: *state = AUDIT_DISABLED; break;
> - case AUDIT_ALWAYS: *state = AUDIT_RECORD_CONTEXT; break;
> - }
> - return 1;
> -}
> -
> -int audit_filter_user(int type)
> -{
> - enum audit_state state = AUDIT_DISABLED;
> struct audit_entry *e;
> - int rc, ret;
> -
> - ret = 1; /* Audit by default */
> -
> - rcu_read_lock();
> - list_for_each_entry_rcu(e, &audit_filter_list[AUDIT_FILTER_USER], list) {
> - rc = audit_filter_user_rules(&e->rule, type, &state);
> - if (rc) {
> - if (rc > 0 && state == AUDIT_DISABLED)
> - ret = 0;
> - break;
> - }
> - }
> - rcu_read_unlock();
> -
> - return ret;
> -}
> -
> -int audit_filter_type(int type)
> -{
> - struct audit_entry *e;
> - int result = 0;
> + int ret = 1; /* Audit by default */
>
> rcu_read_lock();
> - if (list_empty(&audit_filter_list[AUDIT_FILTER_TYPE]))
> + if (list_empty(&audit_filter_list[listtype]))
> goto unlock_and_return;
> + list_for_each_entry_rcu(e, &audit_filter_list[listtype], list) {
> + int i, result = 0;
>
> - list_for_each_entry_rcu(e, &audit_filter_list[AUDIT_FILTER_TYPE],
> - list) {
> - int i;
> for (i = 0; i < e->rule.field_count; i++) {
> struct audit_field *f = &e->rule.fields[i];
> - if (f->type == AUDIT_MSGTYPE) {
> - result = audit_comparator(type, f->op, f->val);
> - if (!result)
> - break;
> + pid_t pid;
> + u32 sid;
> +
> + switch (f->type) {
> + case AUDIT_PID:
> + pid = task_pid_nr(current);
> + result = audit_comparator(pid, f->op, f->val);
> + break;
> + case AUDIT_UID:
> + result = audit_uid_comparator(current_uid(), f->op, f->uid);
> + break;
> + case AUDIT_GID:
> + result = audit_gid_comparator(current_gid(), f->op, f->gid);
> + break;
> + case AUDIT_LOGINUID:
> + result = audit_uid_comparator(audit_get_loginuid(current),
> + f->op, f->uid);
> + break;
> + case AUDIT_LOGINUID_SET:
> + result = audit_comparator(audit_loginuid_set(current),
> + f->op, f->val);
> + break;
> + case AUDIT_MSGTYPE:
> + result = audit_comparator(msgtype, f->op, f->val);
> + break;
> + case AUDIT_SUBJ_USER:
> + case AUDIT_SUBJ_ROLE:
> + case AUDIT_SUBJ_TYPE:
> + case AUDIT_SUBJ_SEN:
> + case AUDIT_SUBJ_CLR:
> + if (f->lsm_rule) {
> + security_task_getsecid(current, &sid);
> + result = security_audit_rule_match(sid,
> + f->type, f->op, f->lsm_rule, NULL);
> + }
> + break;
> + default:
> + goto unlock_and_return;
> }
> + if (result < 0) /* error */
> + goto unlock_and_return;
> + if (!result)
> + break;
> + }
> + if (result > 0) {
> + if (e->rule.action == AUDIT_NEVER || listtype == AUDIT_FILTER_TYPE)
> + ret = 0;
> + break;
> }
> - if (result)
> - goto unlock_and_return;
> }
> unlock_and_return:
> rcu_read_unlock();
> - return result;
> + return ret;
> }
>
> static int update_lsm_rule(struct audit_krule *r)
> --
> 1.7.1
>
> --
> Linux-audit mailing list
> Linux-audit@xxxxxxxxxx
> https://www.redhat.com/mailman/listinfo/linux-audit

--
paul moore
www.paul-moore.com

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