/*- * SPDX-License-Identifier: BSD-3-Clause * * Copyright (c) 1999-2005 Apple Inc. * Copyright (c) 2006-2007, 2016-2018 Robert N. M. Watson * All rights reserved. * * Portions of this software were developed by BAE Systems, the University of * Cambridge Computer Laboratory, and Memorial University under DARPA/AFRL * contract FA8650-15-C-7558 ("CADETS"), as part of the DARPA Transparent * Computing (TC) research program. * * Redistribution and use in source and binary forms, with or without * modification, are permitted provided that the following conditions * are met: * 1. Redistributions of source code must retain the above copyright * notice, this list of conditions and the following disclaimer. * 2. Redistributions in binary form must reproduce the above copyright * notice, this list of conditions and the following disclaimer in the * documentation and/or other materials provided with the distribution. * 3. Neither the name of Apple Inc. ("Apple") nor the names of * its contributors may be used to endorse or promote products derived * from this software without specific prior written permission. * * THIS SOFTWARE IS PROVIDED BY APPLE AND ITS CONTRIBUTORS "AS IS" AND * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE * ARE DISCLAIMED. IN NO EVENT SHALL APPLE OR ITS CONTRIBUTORS BE LIABLE FOR * ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING * IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE * POSSIBILITY OF SUCH DAMAGE. */ #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include FEATURE(audit, "BSM audit support"); static uma_zone_t audit_record_zone; static MALLOC_DEFINE(M_AUDITCRED, "audit_cred", "Audit cred storage"); MALLOC_DEFINE(M_AUDITDATA, "audit_data", "Audit data storage"); MALLOC_DEFINE(M_AUDITPATH, "audit_path", "Audit path storage"); MALLOC_DEFINE(M_AUDITTEXT, "audit_text", "Audit text storage"); MALLOC_DEFINE(M_AUDITGIDSET, "audit_gidset", "Audit GID set storage"); static SYSCTL_NODE(_security, OID_AUTO, audit, CTLFLAG_RW | CTLFLAG_MPSAFE, 0, "TrustedBSD audit controls"); /* * Audit control settings that are set/read by system calls and are hence * non-static. * * Define the audit control flags. */ int audit_trail_enabled; int audit_trail_suspended; #ifdef KDTRACE_HOOKS u_int audit_dtrace_enabled; #endif bool __read_frequently audit_syscalls_enabled; /* * Flags controlling behavior in low storage situations. Should we panic if * a write fails? Should we fail stop if we're out of disk space? */ int audit_panic_on_write_fail; int audit_fail_stop; int audit_argv; int audit_arge; /* * Are we currently "failing stop" due to out of disk space? */ int audit_in_failure; /* * Global audit statistics. */ struct audit_fstat audit_fstat; /* * Preselection mask for non-attributable events. */ struct au_mask audit_nae_mask; /* * Mutex to protect global variables shared between various threads and * processes. */ struct mtx audit_mtx; /* * Queue of audit records ready for delivery to disk. We insert new records * at the tail, and remove records from the head. Also, a count of the * number of records used for checking queue depth. In addition, a counter * of records that we have allocated but are not yet in the queue, which is * needed to estimate the total size of the combined set of records * outstanding in the system. */ struct kaudit_queue audit_q; int audit_q_len; int audit_pre_q_len; /* * Audit queue control settings (minimum free, low/high water marks, etc.) */ struct au_qctrl audit_qctrl; /* * Condition variable to signal to the worker that it has work to do: either * new records are in the queue, or a log replacement is taking place. */ struct cv audit_worker_cv; /* * Condition variable to flag when crossing the low watermark, meaning that * threads blocked due to hitting the high watermark can wake up and continue * to commit records. */ struct cv audit_watermark_cv; /* * Condition variable for auditing threads wait on when in fail-stop mode. * Threads wait on this CV forever (and ever), never seeing the light of day * again. */ static struct cv audit_fail_cv; /* * Optional DTrace audit provider support: function pointers for preselection * and commit events. */ #ifdef KDTRACE_HOOKS void *(*dtaudit_hook_preselect)(au_id_t auid, au_event_t event, au_class_t class); int (*dtaudit_hook_commit)(struct kaudit_record *kar, au_id_t auid, au_event_t event, au_class_t class, int sorf); void (*dtaudit_hook_bsm)(struct kaudit_record *kar, au_id_t auid, au_event_t event, au_class_t class, int sorf, void *bsm_data, size_t bsm_lenlen); #endif /* * Kernel audit information. This will store the current audit address * or host information that the kernel will use when it's generating * audit records. This data is modified by the A_GET{SET}KAUDIT auditon(2) * command. */ static struct auditinfo_addr audit_kinfo; static struct rwlock audit_kinfo_lock; #define KINFO_LOCK_INIT() rw_init(&audit_kinfo_lock, \ "audit_kinfo_lock") #define KINFO_RLOCK() rw_rlock(&audit_kinfo_lock) #define KINFO_WLOCK() rw_wlock(&audit_kinfo_lock) #define KINFO_RUNLOCK() rw_runlock(&audit_kinfo_lock) #define KINFO_WUNLOCK() rw_wunlock(&audit_kinfo_lock) /* * Check various policies to see if we should enable system-call audit hooks. * Note that despite the mutex being held, we want to assign a value exactly * once, as checks of the flag are performed lock-free for performance * reasons. The mutex is used to get a consistent snapshot of policy state -- * e.g., safely accessing the two audit_trail flags. */ void audit_syscalls_enabled_update(void) { mtx_lock(&audit_mtx); #ifdef KDTRACE_HOOKS if (audit_dtrace_enabled) audit_syscalls_enabled = true; else { #endif if (audit_trail_enabled && !audit_trail_suspended) audit_syscalls_enabled = true; else audit_syscalls_enabled = false; #ifdef KDTRACE_HOOKS } #endif mtx_unlock(&audit_mtx); } void audit_set_kinfo(struct auditinfo_addr *ak) { KASSERT(ak->ai_termid.at_type == AU_IPv4 || ak->ai_termid.at_type == AU_IPv6, ("audit_set_kinfo: invalid address type")); KINFO_WLOCK(); audit_kinfo = *ak; KINFO_WUNLOCK(); } void audit_get_kinfo(struct auditinfo_addr *ak) { KASSERT(audit_kinfo.ai_termid.at_type == AU_IPv4 || audit_kinfo.ai_termid.at_type == AU_IPv6, ("audit_set_kinfo: invalid address type")); KINFO_RLOCK(); *ak = audit_kinfo; KINFO_RUNLOCK(); } /* * Construct an audit record for the passed thread. */ static int audit_record_ctor(void *mem, int size, void *arg, int flags) { struct kaudit_record *ar; struct thread *td; struct ucred *cred; struct prison *pr; KASSERT(sizeof(*ar) == size, ("audit_record_ctor: wrong size")); td = arg; ar = mem; bzero(ar, sizeof(*ar)); ar->k_ar.ar_magic = AUDIT_RECORD_MAGIC; nanotime(&ar->k_ar.ar_starttime); /* * Export the subject credential. */ cred = td->td_ucred; cru2x(cred, &ar->k_ar.ar_subj_cred); ar->k_ar.ar_subj_ruid = cred->cr_ruid; ar->k_ar.ar_subj_rgid = cred->cr_rgid; ar->k_ar.ar_subj_egid = cred->cr_groups[0]; ar->k_ar.ar_subj_auid = cred->cr_audit.ai_auid; ar->k_ar.ar_subj_asid = cred->cr_audit.ai_asid; ar->k_ar.ar_subj_pid = td->td_proc->p_pid; ar->k_ar.ar_subj_amask = cred->cr_audit.ai_mask; ar->k_ar.ar_subj_term_addr = cred->cr_audit.ai_termid; /* * If this process is jailed, make sure we capture the name of the * jail so we can use it to generate a zonename token when we covert * this record to BSM. */ if (jailed(cred)) { pr = cred->cr_prison; (void) strlcpy(ar->k_ar.ar_jailname, pr->pr_name, sizeof(ar->k_ar.ar_jailname)); } else ar->k_ar.ar_jailname[0] = '\0'; return (0); } static void audit_record_dtor(void *mem, int size, void *arg) { struct kaudit_record *ar; KASSERT(sizeof(*ar) == size, ("audit_record_dtor: wrong size")); ar = mem; if (ar->k_ar.ar_arg_upath1 != NULL) free(ar->k_ar.ar_arg_upath1, M_AUDITPATH); if (ar->k_ar.ar_arg_upath2 != NULL) free(ar->k_ar.ar_arg_upath2, M_AUDITPATH); if (ar->k_ar.ar_arg_text != NULL) free(ar->k_ar.ar_arg_text, M_AUDITTEXT); if (ar->k_udata != NULL) free(ar->k_udata, M_AUDITDATA); if (ar->k_ar.ar_arg_argv != NULL) free(ar->k_ar.ar_arg_argv, M_AUDITTEXT); if (ar->k_ar.ar_arg_envv != NULL) free(ar->k_ar.ar_arg_envv, M_AUDITTEXT); if (ar->k_ar.ar_arg_groups.gidset != NULL) free(ar->k_ar.ar_arg_groups.gidset, M_AUDITGIDSET); } /* * Initialize the Audit subsystem: configuration state, work queue, * synchronization primitives, worker thread, and trigger device node. Also * call into the BSM assembly code to initialize it. */ static void audit_init(void) { audit_trail_enabled = 0; audit_trail_suspended = 0; audit_syscalls_enabled = false; audit_panic_on_write_fail = 0; audit_fail_stop = 0; audit_in_failure = 0; audit_argv = 0; audit_arge = 0; audit_fstat.af_filesz = 0; /* '0' means unset, unbounded. */ audit_fstat.af_currsz = 0; audit_nae_mask.am_success = 0; audit_nae_mask.am_failure = 0; TAILQ_INIT(&audit_q); audit_q_len = 0; audit_pre_q_len = 0; audit_qctrl.aq_hiwater = AQ_HIWATER; audit_qctrl.aq_lowater = AQ_LOWATER; audit_qctrl.aq_bufsz = AQ_BUFSZ; audit_qctrl.aq_minfree = AU_FS_MINFREE; audit_kinfo.ai_termid.at_type = AU_IPv4; audit_kinfo.ai_termid.at_addr[0] = INADDR_ANY; mtx_init(&audit_mtx, "audit_mtx", NULL, MTX_DEF); KINFO_LOCK_INIT(); cv_init(&audit_worker_cv, "audit_worker_cv"); cv_init(&audit_watermark_cv, "audit_watermark_cv"); cv_init(&audit_fail_cv, "audit_fail_cv"); audit_record_zone = uma_zcreate("audit_record", sizeof(struct kaudit_record), audit_record_ctor, audit_record_dtor, NULL, NULL, UMA_ALIGN_PTR, 0); /* First initialisation of audit_syscalls_enabled. */ audit_syscalls_enabled_update(); /* Initialize the BSM audit subsystem. */ kau_init(); audit_trigger_init(); /* Register shutdown handler. */ EVENTHANDLER_REGISTER(shutdown_pre_sync, audit_shutdown, NULL, SHUTDOWN_PRI_FIRST); /* Start audit worker thread. */ audit_worker_init(); } SYSINIT(audit_init, SI_SUB_AUDIT, SI_ORDER_FIRST, audit_init, NULL); /* * Drain the audit queue and close the log at shutdown. Note that this can * be called both from the system shutdown path and also from audit * configuration syscalls, so 'arg' and 'howto' are ignored. * * XXXRW: In FreeBSD 7.x and 8.x, this fails to wait for the record queue to * drain before returning, which could lead to lost records on shutdown. */ void audit_shutdown(void *arg, int howto) { audit_rotate_vnode(NULL, NULL); } /* * Return the current thread's audit record, if any. */ struct kaudit_record * currecord(void) { return (curthread->td_ar); } /* * XXXAUDIT: Shouldn't there be logic here to sleep waiting on available * pre_q space, suspending the system call until there is room? */ struct kaudit_record * audit_new(int event, struct thread *td) { struct kaudit_record *ar; /* * Note: the number of outstanding uncommitted audit records is * limited to the number of concurrent threads servicing system calls * in the kernel. */ ar = uma_zalloc_arg(audit_record_zone, td, M_WAITOK); ar->k_ar.ar_event = event; mtx_lock(&audit_mtx); audit_pre_q_len++; mtx_unlock(&audit_mtx); return (ar); } void audit_free(struct kaudit_record *ar) { uma_zfree(audit_record_zone, ar); } void audit_commit(struct kaudit_record *ar, int error, int retval) { au_event_t event; au_class_t class; au_id_t auid; int sorf; struct au_mask *aumask; if (ar == NULL) return; ar->k_ar.ar_errno = error; ar->k_ar.ar_retval = retval; nanotime(&ar->k_ar.ar_endtime); /* * Decide whether to commit the audit record by checking the error * value from the system call and using the appropriate audit mask. */ if (ar->k_ar.ar_subj_auid == AU_DEFAUDITID) aumask = &audit_nae_mask; else aumask = &ar->k_ar.ar_subj_amask; if (error) sorf = AU_PRS_FAILURE; else sorf = AU_PRS_SUCCESS; /* * syscalls.master sometimes contains a prototype event number, which * we will transform into a more specific event number now that we * have more complete information gathered during the system call. */ switch(ar->k_ar.ar_event) { case AUE_OPEN_RWTC: ar->k_ar.ar_event = audit_flags_and_error_to_openevent( ar->k_ar.ar_arg_fflags, error); break; case AUE_OPENAT_RWTC: ar->k_ar.ar_event = audit_flags_and_error_to_openatevent( ar->k_ar.ar_arg_fflags, error); break; case AUE_SYSCTL: ar->k_ar.ar_event = audit_ctlname_to_sysctlevent( ar->k_ar.ar_arg_ctlname, ar->k_ar.ar_valid_arg); break; case AUE_AUDITON: /* Convert the auditon() command to an event. */ ar->k_ar.ar_event = auditon_command_event(ar->k_ar.ar_arg_cmd); break; case AUE_MSGSYS: if (ARG_IS_VALID(ar, ARG_SVIPC_WHICH)) ar->k_ar.ar_event = audit_msgsys_to_event(ar->k_ar.ar_arg_svipc_which); break; case AUE_SEMSYS: if (ARG_IS_VALID(ar, ARG_SVIPC_WHICH)) ar->k_ar.ar_event = audit_semsys_to_event(ar->k_ar.ar_arg_svipc_which); break; case AUE_SHMSYS: if (ARG_IS_VALID(ar, ARG_SVIPC_WHICH)) ar->k_ar.ar_event = audit_shmsys_to_event(ar->k_ar.ar_arg_svipc_which); break; } auid = ar->k_ar.ar_subj_auid; event = ar->k_ar.ar_event; class = au_event_class(event); ar->k_ar_commit |= AR_COMMIT_KERNEL; if (au_preselect(event, class, aumask, sorf) != 0) ar->k_ar_commit |= AR_PRESELECT_TRAIL; if (audit_pipe_preselect(auid, event, class, sorf, ar->k_ar_commit & AR_PRESELECT_TRAIL) != 0) ar->k_ar_commit |= AR_PRESELECT_PIPE; #ifdef KDTRACE_HOOKS /* * Expose the audit record to DTrace, both to allow the "commit" probe * to fire if it's desirable, and also to allow a decision to be made * about later firing with BSM in the audit worker. */ if (dtaudit_hook_commit != NULL) { if (dtaudit_hook_commit(ar, auid, event, class, sorf) != 0) ar->k_ar_commit |= AR_PRESELECT_DTRACE; } #endif if ((ar->k_ar_commit & (AR_PRESELECT_TRAIL | AR_PRESELECT_PIPE | AR_PRESELECT_USER_TRAIL | AR_PRESELECT_USER_PIPE | AR_PRESELECT_DTRACE)) == 0) { mtx_lock(&audit_mtx); audit_pre_q_len--; mtx_unlock(&audit_mtx); audit_free(ar); return; } /* * Note: it could be that some records initiated while audit was * enabled should still be committed? * * NB: The check here is not for audit_syscalls because any * DTrace-related obligations have been fulfilled above -- we're just * down to the trail and pipes now. */ mtx_lock(&audit_mtx); if (audit_trail_suspended || !audit_trail_enabled) { audit_pre_q_len--; mtx_unlock(&audit_mtx); audit_free(ar); return; } /* * Constrain the number of committed audit records based on the * configurable parameter. */ while (audit_q_len >= audit_qctrl.aq_hiwater) cv_wait(&audit_watermark_cv, &audit_mtx); TAILQ_INSERT_TAIL(&audit_q, ar, k_q); audit_q_len++; audit_pre_q_len--; cv_signal(&audit_worker_cv); mtx_unlock(&audit_mtx); } /* * audit_syscall_enter() is called on entry to each system call. It is * responsible for deciding whether or not to audit the call (preselection), * and if so, allocating a per-thread audit record. audit_new() will fill in * basic thread/credential properties. * * This function will be entered only if audit_syscalls_enabled was set in the * macro wrapper for this function. It could be cleared by the time this * function runs, but that is an acceptable race. */ void audit_syscall_enter(unsigned short code, struct thread *td) { struct au_mask *aumask; #ifdef KDTRACE_HOOKS void *dtaudit_state; #endif au_class_t class; au_event_t event; au_id_t auid; int record_needed; KASSERT(td->td_ar == NULL, ("audit_syscall_enter: td->td_ar != NULL")); KASSERT((td->td_pflags & TDP_AUDITREC) == 0, ("audit_syscall_enter: TDP_AUDITREC set")); /* * In FreeBSD, each ABI has its own system call table, and hence * mapping of system call codes to audit events. Convert the code to * an audit event identifier using the process system call table * reference. In Darwin, there's only one, so we use the global * symbol for the system call table. No audit record is generated * for bad system calls, as no operation has been performed. */ if (code >= td->td_proc->p_sysent->sv_size) return; event = td->td_proc->p_sysent->sv_table[code].sy_auevent; if (event == AUE_NULL) return; /* * Check which audit mask to use; either the kernel non-attributable * event mask or the process audit mask. */ auid = td->td_ucred->cr_audit.ai_auid; if (auid == AU_DEFAUDITID) aumask = &audit_nae_mask; else aumask = &td->td_ucred->cr_audit.ai_mask; /* * Determine whether trail or pipe preselection would like an audit * record allocated for this system call. */ class = au_event_class(event); if (au_preselect(event, class, aumask, AU_PRS_BOTH)) { /* * If we're out of space and need to suspend unprivileged * processes, do that here rather than trying to allocate * another audit record. * * Note: we might wish to be able to continue here in the * future, if the system recovers. That should be possible * by means of checking the condition in a loop around * cv_wait(). It might be desirable to reevaluate whether an * audit record is still required for this event by * re-calling au_preselect(). */ if (audit_in_failure && priv_check(td, PRIV_AUDIT_FAILSTOP) != 0) { cv_wait(&audit_fail_cv, &audit_mtx); panic("audit_failing_stop: thread continued"); } record_needed = 1; } else if (audit_pipe_preselect(auid, event, class, AU_PRS_BOTH, 0)) { record_needed = 1; } else { record_needed = 0; } /* * After audit trails and pipes have made their policy choices, DTrace * may request that records be generated as well. This is a slightly * complex affair, as the DTrace audit provider needs the audit * framework to maintain some state on the audit record, which has not * been allocated at the point where the decision has to be made. * This hook must run even if we are not changing the decision, as * DTrace may want to stick event state onto a record we were going to * produce due to the trail or pipes. The event state returned by the * DTrace provider must be safe without locks held between here and * below -- i.e., dtaudit_state must must refer to stable memory. */ #ifdef KDTRACE_HOOKS dtaudit_state = NULL; if (dtaudit_hook_preselect != NULL) { dtaudit_state = dtaudit_hook_preselect(auid, event, class); if (dtaudit_state != NULL) record_needed = 1; } #endif /* * If a record is required, allocate it and attach it to the thread * for use throughout the system call. Also attach DTrace state if * required. * * XXXRW: If we decide to reference count the evname_elem underlying * dtaudit_state, we will need to free here if no record is allocated * or allocatable. */ if (record_needed) { td->td_ar = audit_new(event, td); if (td->td_ar != NULL) { td->td_pflags |= TDP_AUDITREC; #ifdef KDTRACE_HOOKS td->td_ar->k_dtaudit_state = dtaudit_state; #endif } } else td->td_ar = NULL; } /* * audit_syscall_exit() is called from the return of every system call, or in * the event of exit1(), during the execution of exit1(). It is responsible * for committing the audit record, if any, along with return condition. */ void audit_syscall_exit(int error, struct thread *td) { int retval; /* * Commit the audit record as desired; once we pass the record into * audit_commit(), the memory is owned by the audit subsystem. The * return value from the system call is stored on the user thread. * If there was an error, the return value is set to -1, imitating * the behavior of the cerror routine. */ if (error) retval = -1; else retval = td->td_retval[0]; audit_commit(td->td_ar, error, retval); td->td_ar = NULL; td->td_pflags &= ~TDP_AUDITREC; } void audit_cred_copy(struct ucred *src, struct ucred *dest) { bcopy(&src->cr_audit, &dest->cr_audit, sizeof(dest->cr_audit)); } void audit_cred_destroy(struct ucred *cred) { } void audit_cred_init(struct ucred *cred) { bzero(&cred->cr_audit, sizeof(cred->cr_audit)); } /* * Initialize audit information for the first kernel process (proc 0) and for * the first user process (init). */ void audit_cred_kproc0(struct ucred *cred) { cred->cr_audit.ai_auid = AU_DEFAUDITID; cred->cr_audit.ai_termid.at_type = AU_IPv4; } void audit_cred_proc1(struct ucred *cred) { cred->cr_audit.ai_auid = AU_DEFAUDITID; cred->cr_audit.ai_termid.at_type = AU_IPv4; } void audit_thread_alloc(struct thread *td) { td->td_ar = NULL; } void audit_thread_free(struct thread *td) { KASSERT(td->td_ar == NULL, ("audit_thread_free: td_ar != NULL")); KASSERT((td->td_pflags & TDP_AUDITREC) == 0, ("audit_thread_free: TDP_AUDITREC set")); } void audit_proc_coredump(struct thread *td, char *path, int errcode) { struct kaudit_record *ar; struct au_mask *aumask; struct ucred *cred; au_class_t class; int ret, sorf; char **pathp; au_id_t auid; ret = 0; /* * Make sure we are using the correct preselection mask. */ cred = td->td_ucred; auid = cred->cr_audit.ai_auid; if (auid == AU_DEFAUDITID) aumask = &audit_nae_mask; else aumask = &cred->cr_audit.ai_mask; /* * It's possible for coredump(9) generation to fail. Make sure that * we handle this case correctly for preselection. */ if (errcode != 0) sorf = AU_PRS_FAILURE; else sorf = AU_PRS_SUCCESS; class = au_event_class(AUE_CORE); if (au_preselect(AUE_CORE, class, aumask, sorf) == 0 && audit_pipe_preselect(auid, AUE_CORE, class, sorf, 0) == 0) return; /* * If we are interested in seeing this audit record, allocate it. * Where possible coredump records should contain a pathname and arg32 * (signal) tokens. */ ar = audit_new(AUE_CORE, td); if (ar == NULL) return; if (path != NULL) { pathp = &ar->k_ar.ar_arg_upath1; *pathp = malloc(MAXPATHLEN, M_AUDITPATH, M_WAITOK); audit_canon_path(td, AT_FDCWD, path, *pathp); ARG_SET_VALID(ar, ARG_UPATH1); } ar->k_ar.ar_arg_signum = td->td_proc->p_sig; ARG_SET_VALID(ar, ARG_SIGNUM); if (errcode != 0) ret = 1; audit_commit(ar, errcode, ret); }