/* audit.c -- Auditing support * Gateway between the kernel (e.g., selinux) and the user-space audit daemon. * System-call specific features have moved to auditsc.c * * Copyright 2003-2004 Red Hat Inc., Durham, North Carolina. * All Rights Reserved. * * This program is free software; you can redistribute it and/or modify * it under the terms of the GNU General Public License as published by * the Free Software Foundation; either version 2 of the License, or * (at your option) any later version. * * This program is distributed in the hope that it will be useful, * but WITHOUT ANY WARRANTY; without even the implied warranty of * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the * GNU General Public License for more details. * * You should have received a copy of the GNU General Public License * along with this program; if not, write to the Free Software * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA * * Written by Rickard E. (Rik) Faith <faith@redhat.com> * * Goals: 1) Integrate fully with SELinux. * 2) Minimal run-time overhead: * a) Minimal when syscall auditing is disabled (audit_enable=0). * b) Small when syscall auditing is enabled and no audit record * is generated (defer as much work as possible to record * generation time): * i) context is allocated, * ii) names from getname are stored without a copy, and * iii) inode information stored from path_lookup. * 3) Ability to disable syscall auditing at boot time (audit=0). * 4) Usable by other parts of the kernel (if audit_log* is called, * then a syscall record will be generated automatically for the * current syscall). * 5) Netlink interface to user-space. * 6) Support low-overhead kernel-based filtering to minimize the * information that must be passed to user-space. * * Example user-space utilities: http://people.redhat.com/sgrubb/audit/ */ #include <linux/init.h> #include <asm/types.h> #include <asm/atomic.h> #include <linux/mm.h> #include <linux/module.h> #include <linux/err.h> #include <linux/kthread.h> #include <linux/audit.h> #include <net/sock.h> #include <net/netlink.h> #include <linux/skbuff.h> #include <linux/netlink.h> #include <linux/selinux.h> #include <linux/inotify.h> #include "audit.h" /* No auditing will take place until audit_initialized != 0. * (Initialization happens after skb_init is called.) */ static int audit_initialized; /* No syscall auditing will take place unless audit_enabled != 0. */ int audit_enabled; /* Default state when kernel boots without any parameters. */ static int audit_default; /* If auditing cannot proceed, audit_failure selects what happens. */ static int audit_failure = AUDIT_FAIL_PRINTK; /* If audit records are to be written to the netlink socket, audit_pid * contains the (non-zero) pid. */ int audit_pid; /* If audit_rate_limit is non-zero, limit the rate of sending audit records * to that number per second. This prevents DoS attacks, but results in * audit records being dropped. */ static int audit_rate_limit; /* Number of outstanding audit_buffers allowed. */ static int audit_backlog_limit = 64; static int audit_backlog_wait_time = 60 * HZ; static int audit_backlog_wait_overflow = 0; /* The identity of the user shutting down the audit system. */ uid_t audit_sig_uid = -1; pid_t audit_sig_pid = -1; u32 audit_sig_sid = 0; /* Records can be lost in several ways: 0) [suppressed in audit_alloc] 1) out of memory in audit_log_start [kmalloc of struct audit_buffer] 2) out of memory in audit_log_move [alloc_skb] 3) suppressed due to audit_rate_limit 4) suppressed due to audit_backlog_limit */ static atomic_t audit_lost = ATOMIC_INIT(0); /* The netlink socket. */ static struct sock *audit_sock; /* Inotify handle. */ struct inotify_handle *audit_ih; /* Hash for inode-based rules */ struct list_head audit_inode_hash[AUDIT_INODE_BUCKETS]; /* The audit_freelist is a list of pre-allocated audit buffers (if more * than AUDIT_MAXFREE are in use, the audit buffer is freed instead of * being placed on the freelist). */ static DEFINE_SPINLOCK(audit_freelist_lock); static int audit_freelist_count; static LIST_HEAD(audit_freelist); static struct sk_buff_head audit_skb_queue; static struct task_struct *kauditd_task; static DECLARE_WAIT_QUEUE_HEAD(kauditd_wait); static DECLARE_WAIT_QUEUE_HEAD(audit_backlog_wait); /* Serialize requests from userspace. */ static DEFINE_MUTEX(audit_cmd_mutex); /* AUDIT_BUFSIZ is the size of the temporary buffer used for formatting * audit records. Since printk uses a 1024 byte buffer, this buffer * should be at least that large. */ #define AUDIT_BUFSIZ 1024 /* AUDIT_MAXFREE is the number of empty audit_buffers we keep on the * audit_freelist. Doing so eliminates many kmalloc/kfree calls. */ #define AUDIT_MAXFREE (2*NR_CPUS) /* The audit_buffer is used when formatting an audit record. The caller * locks briefly to get the record off the freelist or to allocate the * buffer, and locks briefly to send the buffer to the netlink layer or * to place it on a transmit queue. Multiple audit_buffers can be in * use simultaneously. */ struct audit_buffer { struct list_head list; struct sk_buff *skb; /* formatted skb ready to send */ struct audit_context *ctx; /* NULL or associated context */ gfp_t gfp_mask; }; static void audit_set_pid(struct audit_buffer *ab, pid_t pid) { struct nlmsghdr *nlh = (struct nlmsghdr *)ab->skb->data; nlh->nlmsg_pid = pid; } void audit_panic(const char *message) { switch (audit_failure) { case AUDIT_FAIL_SILENT: break; case AUDIT_FAIL_PRINTK: printk(KERN_ERR "audit: %s\n", message); break; case AUDIT_FAIL_PANIC: panic("audit: %s\n", message); break; } } static inline int audit_rate_check(void) { static unsigned long last_check = 0; static int messages = 0; static DEFINE_SPINLOCK(lock); unsigned long flags; unsigned long now; unsigned long elapsed; int retval = 0; if (!audit_rate_limit) return 1; spin_lock_irqsave(&lock, flags); if (++messages < audit_rate_limit) { retval = 1; } else { now = jiffies; elapsed = now - last_check; if (elapsed > HZ) { last_check = now; messages = 0; retval = 1; } } spin_unlock_irqrestore(&lock, flags); return retval; } /** * audit_log_lost - conditionally log lost audit message event * @message: the message stating reason for lost audit message * * Emit at least 1 message per second, even if audit_rate_check is * throttling. * Always increment the lost messages counter. */ void audit_log_lost(const char *message) { static unsigned long last_msg = 0; static DEFINE_SPINLOCK(lock); unsigned long flags; unsigned long now; int print; atomic_inc(&audit_lost); print = (audit_failure == AUDIT_FAIL_PANIC || !audit_rate_limit); if (!print) { spin_lock_irqsave(&lock, flags); now = jiffies; if (now - last_msg > HZ) { print = 1; last_msg = now; } spin_unlock_irqrestore(&lock, flags); } if (print) { printk(KERN_WARNING "audit: audit_lost=%d audit_rate_limit=%d audit_backlog_limit=%d\n", atomic_read(&audit_lost), audit_rate_limit, audit_backlog_limit); audit_panic(message); } } static int audit_set_rate_limit(int limit, uid_t loginuid, u32 sid) { int old = audit_rate_limit; if (sid) { char *ctx = NULL; u32 len; int rc; if ((rc = selinux_ctxid_to_string(sid, &ctx, &len))) return rc; else audit_log(NULL, GFP_KERNEL, AUDIT_CONFIG_CHANGE, "audit_rate_limit=%d old=%d by auid=%u subj=%s", limit, old, loginuid, ctx); kfree(ctx); } else audit_log(NULL, GFP_KERNEL, AUDIT_CONFIG_CHANGE, "audit_rate_limit=%d old=%d by auid=%u", limit, old, loginuid); audit_rate_limit = limit; return 0; } static int audit_set_backlog_limit(int limit, uid_t loginuid, u32 sid) { int old = audit_backlog_limit; if (sid) { char *ctx = NULL; u32 len; int rc; if ((rc = selinux_ctxid_to_string(sid, &ctx, &len))) return rc; else audit_log(NULL, GFP_KERNEL, AUDIT_CONFIG_CHANGE, "audit_backlog_limit=%d old=%d by auid=%u subj=%s", limit, old, loginuid, ctx); kfree(ctx); } else audit_log(NULL, GFP_KERNEL, AUDIT_CONFIG_CHANGE, "audit_backlog_limit=%d old=%d by auid=%u", limit, old, loginuid); audit_backlog_limit = limit; return 0; } static int audit_set_enabled(int state, uid_t loginuid, u32 sid) { int old = audit_enabled; if (state != 0 && state != 1) return -EINVAL; if (sid) { char *ctx = NULL; u32 len; int rc; if ((rc = selinux_ctxid_to_string(sid, &ctx, &len))) return rc; else audit_log(NULL, GFP_KERNEL, AUDIT_CONFIG_CHANGE, "audit_enabled=%d old=%d by auid=%u subj=%s", state, old, loginuid, ctx); kfree(ctx); } else audit_log(NULL, GFP_KERNEL, AUDIT_CONFIG_CHANGE, "audit_enabled=%d old=%d by auid=%u", state, old, loginuid); audit_enabled = state; return 0; } static int audit_set_failure(int state, uid_t loginuid, u32 sid) { int old = audit_failure; if (state != AUDIT_FAIL_SILENT && state != AUDIT_FAIL_PRINTK && state != AUDIT_FAIL_PANIC) return -EINVAL; if (sid) { char *ctx = NULL; u32 len; int rc; if ((rc = selinux_ctxid_to_string(sid, &ctx, &len))) return rc; else audit_log(NULL, GFP_KERNEL, AUDIT_CONFIG_CHANGE, "audit_failure=%d old=%d by auid=%u subj=%s", state, old, loginuid, ctx); kfree(ctx); } else audit_log(NULL, GFP_KERNEL, AUDIT_CONFIG_CHANGE, "audit_failure=%d old=%d by auid=%u", state, old, loginuid); audit_failure = state; return 0; } static int kauditd_thread(void *dummy) { struct sk_buff *skb; while (1) { skb = skb_dequeue(&audit_skb_queue); wake_up(&audit_backlog_wait); if (skb) { if (audit_pid) { int err = netlink_unicast(audit_sock, skb, audit_pid, 0); if (err < 0) { BUG_ON(err != -ECONNREFUSED); /* Shoudn't happen */ printk(KERN_ERR "audit: *NO* daemon at audit_pid=%d\n", audit_pid); audit_pid = 0; } } else { printk(KERN_NOTICE "%s\n", skb->data + NLMSG_SPACE(0)); kfree_skb(skb); } } else { DECLARE_WAITQUEUE(wait, current); set_current_state(TASK_INTERRUPTIBLE); add_wait_queue(&kauditd_wait, &wait); if (!skb_queue_len(&audit_skb_queue)) { try_to_freeze(); schedule(); } __set_current_state(TASK_RUNNING); remove_wait_queue(&kauditd_wait, &wait); } } } int audit_send_list(void *_dest) { struct audit_netlink_list *dest = _dest; int pid = dest->pid; struct sk_buff *skb; /* wait for parent to finish and send an ACK */ mutex_lock(&audit_cmd_mutex); mutex_unlock(&audit_cmd_mutex); while ((skb = __skb_dequeue(&dest->q)) != NULL) netlink_unicast(audit_sock, skb, pid, 0); kfree(dest); return 0; } struct sk_buff *audit_make_reply(int pid, int seq, int type, int done, int multi, void *payload, int size) { struct sk_buff *skb; struct nlmsghdr *nlh; int len = NLMSG_SPACE(size); void *data; int flags = multi ? NLM_F_MULTI : 0; int t = done ? NLMSG_DONE : type; skb = alloc_skb(len, GFP_KERNEL); if (!skb) return NULL; nlh = NLMSG_PUT(skb, pid, seq, t, size); nlh->nlmsg_flags = flags; data = NLMSG_DATA(nlh); memcpy(data, payload, size); return skb; nlmsg_failure: /* Used by NLMSG_PUT */ if (skb) kfree_skb(skb); return NULL; } /** * audit_send_reply - send an audit reply message via netlink * @pid: process id to send reply to * @seq: sequence number * @type: audit message type * @done: done (last) flag * @multi: multi-part message flag * @payload: payload data * @size: payload size * * Allocates an skb, builds the netlink message, and sends it to the pid. * No failure notifications. */ void audit_send_reply(int pid, int seq, int type, int done, int multi, void *payload, int size) { struct sk_buff *skb; skb = audit_make_reply(pid, seq, type, done, multi, payload, size); if (!skb) return; /* Ignore failure. It'll only happen if the sender goes away, because our timeout is set to infinite. */ netlink_unicast(audit_sock, skb, pid, 0); return; } /* * Check for appropriate CAP_AUDIT_ capabilities on incoming audit * control messages. */ static int audit_netlink_ok(struct sk_buff *skb, u16 msg_type) { int err = 0; switch (msg_type) { case AUDIT_GET: case AUDIT_LIST: case AUDIT_LIST_RULES: case AUDIT_SET: case AUDIT_ADD: case AUDIT_ADD_RULE: case AUDIT_DEL: case AUDIT_DEL_RULE: case AUDIT_SIGNAL_INFO: if (security_netlink_recv(skb, CAP_AUDIT_CONTROL)) err = -EPERM; break; case AUDIT_USER: case AUDIT_FIRST_USER_MSG...AUDIT_LAST_USER_MSG: case AUDIT_FIRST_USER_MSG2...AUDIT_LAST_USER_MSG2: if (security_netlink_recv(skb, CAP_AUDIT_WRITE)) err = -EPERM; break; default: /* bad msg */ err = -EINVAL; } return err; } static int audit_receive_msg(struct sk_buff *skb, struct nlmsghdr *nlh) { u32 uid, pid, seq, sid; void *data; struct audit_status *status_get, status_set; int err; struct audit_buffer *ab; u16 msg_type = nlh->nlmsg_type; uid_t loginuid; /* loginuid of sender */ struct audit_sig_info *sig_data; char *ctx; u32 len; err = audit_netlink_ok(skb, msg_type); if (err) return err; /* As soon as there's any sign of userspace auditd, * start kauditd to talk to it */ if (!kauditd_task) kauditd_task = kthread_run(kauditd_thread, NULL, "kauditd"); if (IS_ERR(kauditd_task)) { err = PTR_ERR(kauditd_task); kauditd_task = NULL; return err; } pid = NETLINK_CREDS(skb)->pid; uid = NETLINK_CREDS(skb)->uid; loginuid = NETLINK_CB(skb).loginuid; sid = NETLINK_CB(skb).sid; seq = nlh->nlmsg_seq; data = NLMSG_DATA(nlh); switch (msg_type) { case AUDIT_GET: status_set.enabled = audit_enabled; status_set.failure = audit_failure; status_set.pid = audit_pid; status_set.rate_limit = audit_rate_limit; status_set.backlog_limit = audit_backlog_limit; status_set.lost = atomic_read(&audit_lost); status_set.backlog = skb_queue_len(&audit_skb_queue); audit_send_reply(NETLINK_CB(skb).pid, seq, AUDIT_GET, 0, 0, &status_set, sizeof(status_set)); break; case AUDIT_SET: if (nlh->nlmsg_len < sizeof(struct audit_status)) return -EINVAL; status_get = (struct audit_status *)data; if (status_get->mask & AUDIT_STATUS_ENABLED) { err = audit_set_enabled(status_get->enabled, loginuid, sid); if (err < 0) return err; } if (status_get->mask & AUDIT_STATUS_FAILURE) { err = audit_set_failure(status_get->failure, loginuid, sid); if (err < 0) return err; } if (status_get->mask & AUDIT_STATUS_PID) { int old = audit_pid; if (sid) { if ((err = selinux_ctxid_to_string( sid, &ctx, &len))) return err; else audit_log(NULL, GFP_KERNEL, AUDIT_CONFIG_CHANGE, "audit_pid=%d old=%d by auid=%u subj=%s", status_get->pid, old, loginuid, ctx); kfree(ctx); } else audit_log(NULL, GFP_KERNEL, AUDIT_CONFIG_CHANGE, "audit_pid=%d old=%d by auid=%u", status_get->pid, old, loginuid); audit_pid = status_get->pid; } if (status_get->mask & AUDIT_STATUS_RATE_LIMIT) err = audit_set_rate_limit(status_get->rate_limit, loginuid, sid); if (status_get->mask & AUDIT_STATUS_BACKLOG_LIMIT) err = audit_set_backlog_limit(status_get->backlog_limit, loginuid, sid); break; case AUDIT_USER: case AUDIT_FIRST_USER_MSG...AUDIT_LAST_USER_MSG: case AUDIT_FIRST_USER_MSG2...AUDIT_LAST_USER_MSG2: if (!audit_enabled && msg_type != AUDIT_USER_AVC) return 0; err = audit_filter_user(&NETLINK_CB(skb), msg_type); if (err == 1) { err = 0; ab = audit_log_start(NULL, GFP_KERNEL, msg_type); if (ab) { audit_log_format(ab, "user pid=%d uid=%u auid=%u", pid, uid, loginuid); if (sid) { if (selinux_ctxid_to_string( sid, &ctx, &len)) { audit_log_format(ab, " ssid=%u", sid); /* Maybe call audit_panic? */ } else audit_log_format(ab, " subj=%s", ctx); kfree(ctx); } audit_log_format(ab, " msg='%.1024s'", (char *)data); audit_set_pid(ab, pid); audit_log_end(ab); } } break; case AUDIT_ADD: case AUDIT_DEL: if (nlmsg_len(nlh) < sizeof(struct audit_rule)) return -EINVAL; /* fallthrough */ case AUDIT_LIST: err = audit_receive_filter(nlh->nlmsg_type, NETLINK_CB(skb).pid, uid, seq, data, nlmsg_len(nlh), loginuid, sid); break; case AUDIT_ADD_RULE: case AUDIT_DEL_RULE: if (nlmsg_len(nlh) < sizeof(struct audit_rule_data)) return -EINVAL; /* fallthrough */ case AUDIT_LIST_RULES: err = audit_receive_filter(nlh->nlmsg_type, NETLINK_CB(skb).pid, uid, seq, data, nlmsg_len(nlh), loginuid, sid); break; case AUDIT_SIGNAL_INFO: err = selinux_ctxid_to_string(audit_sig_sid, &ctx, &len); if (err) return err; sig_data = kmalloc(sizeof(*sig_data) + len, GFP_KERNEL); if (!sig_data) { kfree(ctx); return -ENOMEM; } sig_data->uid = audit_sig_uid; sig_data->pid = audit_sig_pid; memcpy(sig_data->ctx, ctx, len); kfree(ctx); audit_send_reply(NETLINK_CB(skb).pid, seq, AUDIT_SIGNAL_INFO, 0, 0, sig_data, sizeof(*sig_data) + len); kfree(sig_data); break; default: err = -EINVAL; break; } return err < 0 ? err : 0; } /* * Get message from skb (based on rtnetlink_rcv_skb). Each message is * processed by audit_receive_msg. Malformed skbs with wrong length are * discarded silently. */ static void audit_receive_skb(struct sk_buff *skb) { int err; struct nlmsghdr *nlh; u32 rlen; while (skb->len >= NLMSG_SPACE(0)) { nlh = (struct nlmsghdr *)skb->data; if (nlh->nlmsg_len < sizeof(*nlh) || skb->len < nlh->nlmsg_len) return; rlen = NLMSG_ALIGN(nlh->nlmsg_len); if (rlen > skb->len) rlen = skb->len; if ((err = audit_receive_msg(skb, nlh))) { netlink_ack(skb, nlh, err); } else if (nlh->nlmsg_flags & NLM_F_ACK) netlink_ack(skb, nlh, 0); skb_pull(skb, rlen); } } /* Receive messages from netlink socket. */ static void audit_receive(struct sock *sk, int length) { struct sk_buff *skb; unsigned int qlen; mutex_lock(&audit_cmd_mutex); for (qlen = skb_queue_len(&sk->sk_receive_queue); qlen; qlen--) { skb = skb_dequeue(&sk->sk_receive_queue); audit_receive_skb(skb); kfree_skb(skb); } mutex_unlock(&audit_cmd_mutex); } #ifdef CONFIG_AUDITSYSCALL static const struct inotify_operations audit_inotify_ops = { .handle_event = audit_handle_ievent, .destroy_watch = audit_free_parent, }; #endif /* Initialize audit support at boot time. */ static int __init audit_init(void) { int i; printk(KERN_INFO "audit: initializing netlink socket (%s)\n", audit_default ? "enabled" : "disabled"); audit_sock = netlink_kernel_create(NETLINK_AUDIT, 0, audit_receive, THIS_MODULE); if (!audit_sock) audit_panic("cannot initialize netlink socket"); else audit_sock->sk_sndtimeo = MAX_SCHEDULE_TIMEOUT; skb_queue_head_init(&audit_skb_queue); audit_initialized = 1; audit_enabled = audit_default; /* Register the callback with selinux. This callback will be invoked * when a new policy is loaded. */ selinux_audit_set_callback(&selinux_audit_rule_update); audit_log(NULL, GFP_KERNEL, AUDIT_KERNEL, "initialized"); #ifdef CONFIG_AUDITSYSCALL audit_ih = inotify_init(&audit_inotify_ops); if (IS_ERR(audit_ih)) audit_panic("cannot initialize inotify handle"); #endif for (i = 0; i < AUDIT_INODE_BUCKETS; i++) INIT_LIST_HEAD(&audit_inode_hash[i]); return 0; } __initcall(audit_init); /* Process kernel command-line parameter at boot time. audit=0 or audit=1. */ static int __init audit_enable(char *str) { audit_default = !!simple_strtol(str, NULL, 0); printk(KERN_INFO "audit: %s%s\n", audit_default ? "enabled" : "disabled", audit_initialized ? "" : " (after initialization)"); if (audit_initialized) audit_enabled = audit_default; return 1; } __setup("audit=", audit_enable); static void audit_buffer_free(struct audit_buffer *ab) { unsigned long flags; if (!ab) return; if (ab->skb) kfree_skb(ab->skb); spin_lock_irqsave(&audit_freelist_lock, flags); if (audit_freelist_count > AUDIT_MAXFREE) kfree(ab); else { audit_freelist_count++; list_add(&ab->list, &audit_freelist); } spin_unlock_irqrestore(&audit_freelist_lock, flags); } static struct audit_buffer * audit_buffer_alloc(struct audit_context *ctx, gfp_t gfp_mask, int type) { unsigned long flags; struct audit_buffer *ab = NULL; struct nlmsghdr *nlh; spin_lock_irqsave(&audit_freelist_lock, flags); if (!list_empty(&audit_freelist)) { ab = list_entry(audit_freelist.next, struct audit_buffer, list); list_del(&ab->list); --audit_freelist_count; } spin_unlock_irqrestore(&audit_freelist_lock, flags); if (!ab) { ab = kmalloc(sizeof(*ab), gfp_mask); if (!ab) goto err; } ab->skb = alloc_skb(AUDIT_BUFSIZ, gfp_mask); if (!ab->skb) goto err; ab->ctx = ctx; ab->gfp_mask = gfp_mask; nlh = (struct nlmsghdr *)skb_put(ab->skb, NLMSG_SPACE(0)); nlh->nlmsg_type = type; nlh->nlmsg_flags = 0; nlh->nlmsg_pid = 0; nlh->nlmsg_seq = 0; return ab; err: audit_buffer_free(ab); return NULL; } /** * audit_serial - compute a serial number for the audit record * * Compute a serial number for the audit record. Audit records are * written to user-space as soon as they are generated, so a complete * audit record may be written in several pieces. The timestamp of the * record and this serial number are used by the user-space tools to * determine which pieces belong to the same audit record. The * (timestamp,serial) tuple is unique for each syscall and is live from * syscall entry to syscall exit. * * NOTE: Another possibility is to store the formatted records off the * audit context (for those records that have a context), and emit them * all at syscall exit. However, this could delay the reporting of * significant errors until syscall exit (or never, if the system * halts). */ unsigned int audit_serial(void) { static DEFINE_SPINLOCK(serial_lock); static unsigned int serial = 0; unsigned long flags; unsigned int ret; spin_lock_irqsave(&serial_lock, flags); do { ret = ++serial; } while (unlikely(!ret)); spin_unlock_irqrestore(&serial_lock, flags); return ret; } static inline void audit_get_stamp(struct audit_context *ctx, struct timespec *t, unsigned int *serial) { if (ctx) auditsc_get_stamp(ctx, t, serial); else { *t = CURRENT_TIME; *serial = audit_serial(); } } /* Obtain an audit buffer. This routine does locking to obtain the * audit buffer, but then no locking is required for calls to * audit_log_*format. If the tsk is a task that is currently in a * syscall, then the syscall is marked as auditable and an audit record * will be written at syscall exit. If there is no associated task, tsk * should be NULL. */ /** * audit_log_start - obtain an audit buffer * @ctx: audit_context (may be NULL) * @gfp_mask: type of allocation * @type: audit message type * * Returns audit_buffer pointer on success or NULL on error. * * Obtain an audit buffer. This routine does locking to obtain the * audit buffer, but then no locking is required for calls to * audit_log_*format. If the task (ctx) is a task that is currently in a * syscall, then the syscall is marked as auditable and an audit record * will be written at syscall exit. If there is no associated task, then * task context (ctx) should be NULL. */ struct audit_buffer *audit_log_start(struct audit_context *ctx, gfp_t gfp_mask, int type) { struct audit_buffer *ab = NULL; struct timespec t; unsigned int serial; int reserve; unsigned long timeout_start = jiffies; if (!audit_initialized) return NULL; if (unlikely(audit_filter_type(type))) return NULL; if (gfp_mask & __GFP_WAIT) reserve = 0; else reserve = 5; /* Allow atomic callers to go up to five entries over the normal backlog limit */ while (audit_backlog_limit && skb_queue_len(&audit_skb_queue) > audit_backlog_limit + reserve) { if (gfp_mask & __GFP_WAIT && audit_backlog_wait_time && time_before(jiffies, timeout_start + audit_backlog_wait_time)) { /* Wait for auditd to drain the queue a little */ DECLARE_WAITQUEUE(wait, current); set_current_state(TASK_INTERRUPTIBLE); add_wait_queue(&audit_backlog_wait, &wait); if (audit_backlog_limit && skb_queue_len(&audit_skb_queue) > audit_backlog_limit) schedule_timeout(timeout_start + audit_backlog_wait_time - jiffies); __set_current_state(TASK_RUNNING); remove_wait_queue(&audit_backlog_wait, &wait); continue; } if (audit_rate_check()) printk(KERN_WARNING "audit: audit_backlog=%d > " "audit_backlog_limit=%d\n", skb_queue_len(&audit_skb_queue), audit_backlog_limit); audit_log_lost("backlog limit exceeded"); audit_backlog_wait_time = audit_backlog_wait_overflow; wake_up(&audit_backlog_wait); return NULL; } ab = audit_buffer_alloc(ctx, gfp_mask, type); if (!ab) { audit_log_lost("out of memory in audit_log_start"); return NULL; } audit_get_stamp(ab->ctx, &t, &serial); audit_log_format(ab, "audit(%lu.%03lu:%u): ", t.tv_sec, t.tv_nsec/1000000, serial); return ab; } /** * audit_expand - expand skb in the audit buffer * @ab: audit_buffer * @extra: space to add at tail of the skb * * Returns 0 (no space) on failed expansion, or available space if * successful. */ static inline int audit_expand(struct audit_buffer *ab, int extra) { struct sk_buff *skb = ab->skb; int ret = pskb_expand_head(skb, skb_headroom(skb), extra, ab->gfp_mask); if (ret < 0) { audit_log_lost("out of memory in audit_expand"); return 0; } return skb_tailroom(skb); } /* * Format an audit message into the audit buffer. If there isn't enough * room in the audit buffer, more room will be allocated and vsnprint * will be called a second time. Currently, we assume that a printk * can't format message larger than 1024 bytes, so we don't either. */ static void audit_log_vformat(struct audit_buffer *ab, const char *fmt, va_list args) { int len, avail; struct sk_buff *skb; va_list args2; if (!ab) return; BUG_ON(!ab->skb); skb = ab->skb; avail = skb_tailroom(skb); if (avail == 0) { avail = audit_expand(ab, AUDIT_BUFSIZ); if (!avail) goto out; } va_copy(args2, args); len = vsnprintf(skb->tail, avail, fmt, args); if (len >= avail) { /* The printk buffer is 1024 bytes long, so if we get * here and AUDIT_BUFSIZ is at least 1024, then we can * log everything that printk could have logged. */ avail = audit_expand(ab, max_t(unsigned, AUDIT_BUFSIZ, 1+len-avail)); if (!avail) goto out; len = vsnprintf(skb->tail, avail, fmt, args2); } if (len > 0) skb_put(skb, len); out: return; } /** * audit_log_format - format a message into the audit buffer. * @ab: audit_buffer * @fmt: format string * @...: optional parameters matching @fmt string * * All the work is done in audit_log_vformat. */ void audit_log_format(struct audit_buffer *ab, const char *fmt, ...) { va_list args; if (!ab) return; va_start(args, fmt); audit_log_vformat(ab, fmt, args); va_end(args); } /** * audit_log_hex - convert a buffer to hex and append it to the audit skb * @ab: the audit_buffer * @buf: buffer to convert to hex * @len: length of @buf to be converted * * No return value; failure to expand is silently ignored. * * This function will take the passed buf and convert it into a string of * ascii hex digits. The new string is placed onto the skb. */ void audit_log_hex(struct audit_buffer *ab, const unsigned char *buf, size_t len) { int i, avail, new_len; unsigned char *ptr; struct sk_buff *skb; static const unsigned char *hex = "0123456789ABCDEF"; if (!ab) return; BUG_ON(!ab->skb); skb = ab->skb; avail = skb_tailroom(skb); new_len = len<<1; if (new_len >= avail) { /* Round the buffer request up to the next multiple */ new_len = AUDIT_BUFSIZ*(((new_len-avail)/AUDIT_BUFSIZ) + 1); avail = audit_expand(ab, new_len); if (!avail) return; } ptr = skb->tail; for (i=0; i<len; i++) { *ptr++ = hex[(buf[i] & 0xF0)>>4]; /* Upper nibble */ *ptr++ = hex[buf[i] & 0x0F]; /* Lower nibble */ } *ptr = 0; skb_put(skb, len << 1); /* new string is twice the old string */ } /* * Format a string of no more than slen characters into the audit buffer, * enclosed in quote marks. */ static void audit_log_n_string(struct audit_buffer *ab, size_t slen, const char *string) { int avail, new_len; unsigned char *ptr; struct sk_buff *skb; if (!ab) return; BUG_ON(!ab->skb); skb = ab->skb; avail = skb_tailroom(skb); new_len = slen + 3; /* enclosing quotes + null terminator */ if (new_len > avail) { avail = audit_expand(ab, new_len); if (!avail) return; } ptr = skb->tail; *ptr++ = '"'; memcpy(ptr, string, slen); ptr += slen; *ptr++ = '"'; *ptr = 0; skb_put(skb, slen + 2); /* don't include null terminator */ } /** * audit_log_n_unstrustedstring - log a string that may contain random characters * @ab: audit_buffer * @len: lenth of string (not including trailing null) * @string: string to be logged * * This code will escape a string that is passed to it if the string * contains a control character, unprintable character, double quote mark, * or a space. Unescaped strings will start and end with a double quote mark. * Strings that are escaped are printed in hex (2 digits per char). * * The caller specifies the number of characters in the string to log, which may * or may not be the entire string. */ const char *audit_log_n_untrustedstring(struct audit_buffer *ab, size_t len, const char *string) { const unsigned char *p = string; while (*p) { if (*p == '"' || *p < 0x21 || *p > 0x7f) { audit_log_hex(ab, string, len); return string + len + 1; } p++; } audit_log_n_string(ab, len, string); return p + 1; } /** * audit_log_unstrustedstring - log a string that may contain random characters * @ab: audit_buffer * @string: string to be logged * * Same as audit_log_n_unstrustedstring(), except that strlen is used to * determine string length. */ const char *audit_log_untrustedstring(struct audit_buffer *ab, const char *string) { return audit_log_n_untrustedstring(ab, strlen(string), string); } /* This is a helper-function to print the escaped d_path */ void audit_log_d_path(struct audit_buffer *ab, const char *prefix, struct dentry *dentry, struct vfsmount *vfsmnt) { char *p, *path; if (prefix) audit_log_format(ab, " %s", prefix); /* We will allow 11 spaces for ' (deleted)' to be appended */ path = kmalloc(PATH_MAX+11, ab->gfp_mask); if (!path) { audit_log_format(ab, "<no memory>"); return; } p = d_path(dentry, vfsmnt, path, PATH_MAX+11); if (IS_ERR(p)) { /* Should never happen since we send PATH_MAX */ /* FIXME: can we save some information here? */ audit_log_format(ab, "<too long>"); } else audit_log_untrustedstring(ab, p); kfree(path); } /** * audit_log_end - end one audit record * @ab: the audit_buffer * * The netlink_* functions cannot be called inside an irq context, so * the audit buffer is placed on a queue and a tasklet is scheduled to * remove them from the queue outside the irq context. May be called in * any context. */ void audit_log_end(struct audit_buffer *ab) { if (!ab) return; if (!audit_rate_check()) { audit_log_lost("rate limit exceeded"); } else { if (audit_pid) { struct nlmsghdr *nlh = (struct nlmsghdr *)ab->skb->data; nlh->nlmsg_len = ab->skb->len - NLMSG_SPACE(0); skb_queue_tail(&audit_skb_queue, ab->skb); ab->skb = NULL; wake_up_interruptible(&kauditd_wait); } else { printk(KERN_NOTICE "%s\n", ab->skb->data + NLMSG_SPACE(0)); } } audit_buffer_free(ab); } /** * audit_log - Log an audit record * @ctx: audit context * @gfp_mask: type of allocation * @type: audit message type * @fmt: format string to use * @...: variable parameters matching the format string * * This is a convenience function that calls audit_log_start, * audit_log_vformat, and audit_log_end. It may be called * in any context. */ void audit_log(struct audit_context *ctx, gfp_t gfp_mask, int type, const char *fmt, ...) { struct audit_buffer *ab; va_list args; ab = audit_log_start(ctx, gfp_mask, type); if (ab) { va_start(args, fmt); audit_log_vformat(ab, fmt, args); va_end(args); audit_log_end(ab); } } EXPORT_SYMBOL(audit_log_start); EXPORT_SYMBOL(audit_log_end); EXPORT_SYMBOL(audit_log_format); EXPORT_SYMBOL(audit_log);