1.\" Copyright (c) 2006 Robert N. M. Watson 2.\" All rights reserved. 3.\" 4.\" Redistribution and use in source and binary forms, with or without 5.\" modification, are permitted provided that the following conditions 6.\" are met: 7.\" 1. Redistributions of source code must retain the above copyright 8.\" notice, this list of conditions and the following disclaimer. 9.\" 2. Redistributions in binary form must reproduce the above copyright 10.\" notice, this list of conditions and the following disclaimer in the 11.\" documentation and/or other materials provided with the distribution. 12.\" 13.\" THIS SOFTWARE IS PROVIDED BY THE AUTHORS AND CONTRIBUTORS ``AS IS'' AND 14.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 15.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 16.\" ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHORS OR CONTRIBUTORS BE LIABLE 17.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 18.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 19.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 20.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 21.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 22.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 23.\" SUCH DAMAGE. 24.\" 25.\" $FreeBSD$ 26.\" 27.Dd May 30, 2018 28.Dt AUDITPIPE 4 29.Os 30.Sh NAME 31.Nm auditpipe 32.Nd "pseudo-device for live audit event tracking" 33.Sh SYNOPSIS 34.Cd "options AUDIT" 35.Sh DESCRIPTION 36While audit trail files 37generated with 38.Xr audit 4 39and maintained by 40.Xr auditd 8 41provide a reliable long-term store for audit log information, current log 42files are owned by the audit daemon until terminated making them somewhat 43unwieldy for live monitoring applications such as host-based intrusion 44detection. 45For example, the log may be cycled and new records written to a new file 46without notice to applications that may be accessing the file. 47.Pp 48The audit facility provides an audit pipe facility for applications requiring 49direct access to live BSM audit data for the purposes of real-time 50monitoring. 51Audit pipes are available via a clonable special device, 52.Pa /dev/auditpipe , 53subject to the permissions on the device node, and provide a 54.Qq tee 55of the audit event stream. 56As the device is clonable, more than one instance of the device may be opened 57at a time; each device instance will provide independent access to all 58records. 59.Pp 60The audit pipe device provides discrete BSM audit records; if the read buffer 61passed by the application is too small to hold the next record in the 62sequence, it will be dropped. 63Unlike audit data written to the audit trail, the reliability of record 64delivery is not guaranteed. 65In particular, when an audit pipe queue fills, records will be dropped. 66Audit pipe devices are blocking by default, but support non-blocking I/O, 67asynchronous I/O using 68.Dv SIGIO , 69and polled operation via 70.Xr select 2 71and 72.Xr poll 2 . 73.Pp 74Applications may choose to track the global audit trail, or configure local 75preselection parameters independent of the global audit trail parameters. 76.Ss Audit Pipe Queue Ioctls 77The following ioctls retrieve and set various audit pipe record queue 78properties: 79.Bl -tag -width ".Dv AUDITPIPE_GET_MAXAUDITDATA" 80.It Dv AUDITPIPE_GET_QLEN 81Query the current number of records available for reading on the pipe. 82.It Dv AUDITPIPE_GET_QLIMIT 83Retrieve the current maximum number of records that may be queued for reading 84on the pipe. 85.It Dv AUDITPIPE_SET_QLIMIT 86Set the current maximum number of records that may be queued for reading on 87the pipe. 88The new limit must fall between the queue limit minimum and queue limit 89maximum queryable using the following two ioctls. 90.It Dv AUDITPIPE_GET_QLIMIT_MIN 91Query the lowest possible maximum number of records that may be queued for 92reading on the pipe. 93.It Dv AUDITPIPE_GET_QLIMIT_MAX 94Query the highest possible maximum number of records that may be queued for 95reading on the pipe. 96.It Dv AUDITPIPE_FLUSH 97Flush all outstanding records on the audit pipe; useful after setting initial 98preselection properties to delete records queued during the configuration 99process which may not match the interests of the user process. 100.It Dv AUDITPIPE_GET_MAXAUDITDATA 101Query the maximum size of an audit record, which is a useful minimum size for 102a user space buffer intended to hold audit records read from the audit pipe. 103.El 104.Ss Audit Pipe Preselection Mode Ioctls 105By default, the audit pipe facility configures pipes to present records 106matched by the system-wide audit trail, configured by 107.Xr auditd 8 . 108However, the preselection mechanism for audit pipes can be configured using 109alternative criteria, including pipe-local flags and naflags settings, as 110well as auid-specific selection masks. 111This allows applications to track events not captured in the global audit 112trail, as well as limit records presented to those of specific interest to 113the application. 114.Pp 115The following ioctls configure the preselection mode on an audit pipe: 116.Bl -tag -width ".Dv AUDITPIPE_GET_PRESELECT_MODE" 117.It Dv AUDITPIPE_GET_PRESELECT_MODE 118Return the current preselect mode on the audit pipe. 119The ioctl argument should be of type 120.Vt int . 121.It Dv AUDITPIPE_SET_PRESELECT_MODE 122Set the current preselection mode on the audit pipe. 123The ioctl argument should be of type 124.Vt int . 125.El 126.Pp 127Possible preselection mode values are: 128.Bl -tag -width ".Dv AUDITPIPE_PRESELECT_MODE_TRAIL" 129.It Dv AUDITPIPE_PRESELECT_MODE_TRAIL 130Use the global audit trail preselection parameters to select records for the 131audit pipe. 132.It Dv AUDITPIPE_PRESELECT_MODE_LOCAL 133Use local audit pipe preselection; this model is similar to the global audit 134trail configuration model, consisting of global flags and naflags parameters, 135as well as a set of per-auid masks. 136These parameters are configured using further ioctls. 137.El 138.Pp 139After changing the audit pipe preselection mode, records selected under 140earlier preselection configuration may still be in the audit pipe queue. 141The application may flush the current record queue after changing the 142configuration to remove possibly undesired records. 143.Ss Audit Pipe Local Preselection Mode Ioctls 144The following ioctls configure the preselection parameters used when an audit 145pipe is configured for the 146.Dv AUDITPIPE_PRESELECT_MODE_LOCAL 147preselection mode. 148.Bl -tag -width ".Dv AUDITPIPE_GET_PRESELECT_NAFLAGS" 149.It Dv AUDITPIPE_GET_PRESELECT_FLAGS 150Retrieve the current default preselection flags for attributable events on 151the pipe. 152These flags correspond to the 153.Va flags 154field in 155.Xr audit_control 5 . 156The ioctl argument should be of type 157.Vt au_mask_t . 158.It Dv AUDITPIPE_SET_PRESELECT_FLAGS 159Set the current default preselection flags for attributable events on the 160pipe. 161These flags correspond to the 162.Va flags 163field in 164.Xr audit_control 5 . 165The ioctl argument should be of type 166.Vt au_mask_t . 167.It Dv AUDITPIPE_GET_PRESELECT_NAFLAGS 168Retrieve the current default preselection flags for non-attributable events 169on the pipe. 170These flags correspond to the 171.Va naflags 172field in 173.Xr audit_control 5 . 174The ioctl argument should be of type 175.Vt au_mask_t . 176.It Dv AUDITPIPE_SET_PRESELECT_NAFLAGS 177Set the current default preselection flags for non-attributable events on the 178pipe. 179These flags correspond to the 180.Va naflags 181field in 182.Xr audit_control 5 . 183The ioctl argument should be of type 184.Vt au_mask_t . 185.It Dv AUDITPIPE_GET_PRESELECT_AUID 186Query the current preselection masks for a specific auid on the pipe. 187The ioctl argument should be of type 188.Vt "struct auditpipe_ioctl_preselect" . 189The auid to query is specified via the 190.Va ap_auid 191field of type 192.Vt au_id_t ; 193the mask will be returned via 194.Va ap_mask 195of type 196.Vt au_mask_t . 197.It Dv AUDITPIPE_SET_PRESELECT_AUID 198Set the current preselection masks for a specific auid on the pipe. 199Arguments are identical to 200.Dv AUDITPIPE_GET_PRESELECT_AUID , 201except that the caller should properly initialize the 202.Va ap_mask 203field to hold the desired preselection mask. 204.It Dv AUDITPIPE_DELETE_PRESELECT_AUID 205Delete the current preselection mask for a specific auid on the pipe. 206Once called, events associated with the specified auid will use the default 207flags mask. 208The ioctl argument should be of type 209.Vt au_id_t . 210.It Dv AUDITPIPE_FLUSH_PRESELECT_AUID 211Delete all auid specific preselection specifications. 212.El 213.Sh EXAMPLES 214The 215.Xr praudit 1 216utility 217may be directly executed on 218.Pa /dev/auditpipe 219to review the default audit trail. 220.Sh SEE ALSO 221.Xr poll 2 , 222.Xr select 2 , 223.Xr audit 4 , 224.Xr audit_control 5 , 225.Xr audit 8 , 226.Xr auditd 8 227.Sh HISTORY 228The OpenBSM implementation was created by McAfee Research, the security 229division of McAfee Inc., under contract to Apple Computer Inc.\& in 2004. 230It was subsequently adopted by the TrustedBSD Project as the foundation for 231the OpenBSM distribution. 232.Pp 233Support for kernel audit first appeared in 234.Fx 6.2 . 235.Sh AUTHORS 236The audit pipe facility was designed and implemented by 237.An Robert Watson Aq Mt rwatson@FreeBSD.org . 238.Pp 239The Basic Security Module (BSM) interface to audit records and audit event 240stream format were defined by Sun Microsystems. 241.Sh BUGS 242See the 243.Xr audit 4 244manual page for information on audit-related bugs and limitations. 245.Pp 246The configurable preselection mechanism mirrors the selection model present 247for the global audit trail. 248It might be desirable to provide a more flexible selection model. 249.Pp 250The per-pipe audit event queue is fifo, with drops occurring if either the 251user thread provides in sufficient for the record on the queue head, or on 252enqueue if there is insufficient room. 253It might be desirable to support partial reads of records, which would be 254more compatible with buffered I/O as implemented in system libraries, and to 255allow applications to select which records are dropped, possibly in the style 256of preselection. 257