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AUDIT.LOG(5) FreeBSD File Formats Manual AUDIT.LOG(5)
NAME audit - Basic Security Module (BSM) file format
DESCRIPTION The audit file format is based on Sun's Basic Security Module (BSM) file format, a token-based record stream to represent system audit data. This file format is both flexible and extensible, able to describe a broad range of data types, and easily extended to describe new data types in a moderately backward and forward compatible way.
BSM token streams typically begin and end with a "file" token, which provides time stamp and file name information for the stream; when processing a BSM token stream from a stream as opposed to a single file source, file tokens may be seen at any point between ordinary records identifying when particular parts of the stream begin and end. All other tokens will appear in the context of a complete BSM audit record, which begins with a "header" token, and ends with a "trailer" token, which describe the audit record. Between these two tokens will appear a variety of data tokens, such as process information, file path names, IPC object information, MAC labels, socket information, and so on.
The BSM file format defines specific token orders for each record event type; however, some variation may occur depending on the operating system in use, what system options, such as mandatory access control, are present.
This manual page documents the common token types and their binary format, and is intended for reference purposes only. It is recommended that application programmers use the libbsm(3) interface to read and write tokens, rather than parsing or constructing records by hand.
File Token The "file" token is used at the beginning and end of an audit log file to indicate when the audit log begins and ends. It includes a pathname so that, if concatenated together, original file boundaries are still observable, and gaps in the audit log can be identified. A "file" token can be created using au_to_file(3).
Field Bytes Description Token ID 1 byte Token ID Seconds 4 bytes File time stamp Microseconds 4 bytes File time stamp File name length 2 bytes File name of audit trail File pathname N bytes + 1 NUL File name of audit trail
Header Token The "header" token is used to mark the beginning of a complete audit record, and includes the length of the total record in bytes, a version number for the record layout, the event type and subtype, and the time at which the event occurred. A 32-bit "header" token can be created using au_to_header32(3); a 64-bit "header" token can be created using Version Number 1 byte Record version number Event Type 2 bytes Event type Event Modifier 2 bytes Event sub-type Seconds 4/8 bytes Record time stamp (32/64-bits) Nanoseconds 4/8 bytes Record time stamp (32/64-bits)
Expanded Header Token The "expanded header" token is an expanded version of the "header" token, with the addition of a machine IPv4 or IPv6 address. A 32-bit extended "header" token can be created using au_to_header32_ex(3); a 64-bit extended "header" token can be created using au_to_header64_ex(3).
Field Bytes Description Token ID 1 byte Token ID Record Byte Count 4 bytes Number of bytes in record Version Number 1 byte Record version number Event Type 2 bytes Event type Event Modifier 2 bytes Event sub-type Address Type/Length 1 byte Host address type and length Machine Address 4/16 bytes IPv4 or IPv6 address Seconds 4/8 bytes Record time stamp (32/64-bits) Nanoseconds 4/8 bytes Record time stamp (32/64-bits)
Trailer Token The "trailer" terminates a BSM audit record, and contains a magic number, AUT_TRAILER_MAGIC and length that can be used to validate that the record was read properly. A "trailer" token can be created using au_to_trailer(3).
Field Bytes Description Token ID 1 byte Token ID Trailer Magic 2 bytes Trailer magic number Record Byte Count 4 bytes Number of bytes in record

Field Bytes Description Token ID 1 byte Token ID How to Print 1 byte User-defined printing information Basic Unit 1 byte Size of a unit in bytes Unit Count 1 byte Number of units of data present Data Items Variable User data
in_addr Token The "in_addr" token holds a network byte order IPv4 address. An "in_addr" token can be created using au_to_in_addr(3) for an IPv4 address.
Field Bytes Description Token ID 1 byte Token ID IP Address 4 bytes IPv4 address
Expanded in_addr Token The "in_addr_ex" token holds a network byte order IPv4 or IPv6 address. An "in_addr_ex" token can be created using au_to_in_addr_ex(3) for an IPv6 address.
See the BUGS section for information on the storage of this token.
Field Bytes Description Token ID 1 byte Token ID IP Address Type 1 byte Type of address IP Address 4/16 bytes IPv4 or IPv6 address
ip Token The "ip" token contains an IP packet header in network byte order. An "ip" token can be created using au_to_ip(3).
Field Bytes Description Token ID 1 byte Token ID Version and IHL 1 byte Version and IP header length Type of Service 1 byte IP TOS field Length 2 bytes IP packet length in network byte order ID 2 bytes IP header ID for reassembly Offset 2 bytes IP fragment number Checksum 2 bytes IP header checksum, network byte order Source Address 4 bytes IPv4 source address Destination Address 4 bytes IPv4 destination address
iport Token The "iport" token stores an IP port number in network byte order. An "iport" token can be created using au_to_iport(3).
Field Bytes Description Token ID 1 byte Token ID Port Number 2 bytes Port number in network byte order
Path Token The "path" token contains a pathname. A "path" token can be created using au_to_path(3).
Field Bytes Description Token ID 1 byte Token ID Path Length 2 bytes Length of path in bytes Path N bytes + 1 NUL Path name
path_attr Token The "path_attr" token contains a set of NUL-terminated path names. The libbsm(3) API cannot currently create a "path_attr" token.
Field Bytes Description Token ID 1 byte Token ID Count 2 bytes Number of NUL-terminated string(s) in token Path Variable count NUL-terminated string(s)
Process Token The "process" token contains a description of the security properties of a process involved as the target of an auditable event, such as the destination for signal delivery. It should not be confused with the "subject" token, which describes the subject performing an auditable event. This includes both the traditional UNIX security properties, such as user IDs and group IDs, but also audit information such as the audit user ID and session. A "process" token can be created using au_to_process32(3) or au_to_process64(3).
Field Bytes Description Token ID 1 byte Token ID Audit ID 4 bytes Audit user Real Group ID 4 bytes Real group ID Process ID 4 bytes Process ID Session ID 4 bytes Audit session ID Terminal Port ID 4/8 bytes Terminal port ID (32/64-bits) Terminal Machine Address 4 bytes IP address of machine
Expanded Process Token The "expanded process" token contains the contents of the "process" token, with the addition of a machine address type and variable length address storage capable of containing IPv6 addresses. An "expanded process" token can be created using au_to_process32_ex(3) or au_to_process64_ex(3).
Field Bytes Description Token ID 1 byte Token ID Audit ID 4 bytes Audit user ID Effective User ID 4 bytes Effective user ID Effective Group ID 4 bytes Effective group ID Real User ID 4 bytes Real user ID Real Group ID 4 bytes Real group ID Process ID 4 bytes Process ID Session ID 4 bytes Audit session ID Terminal Port ID 4/8 bytes Terminal port ID (32/64-bits) Terminal Address Type/Length 4 bytes Length of machine address Terminal Machine Address 4 bytes IPv4 or IPv6 address of machine
Return Token The "return" token contains a system call or library function return condition, including return value and error number associated with the global variable errno. A "return" token can be created using au_to_return32(3) or au_to_return64(3).
Field Bytes Description Token ID 1 byte Token ID Error Number 1 byte Errno value, or 0 if undefined Return Value 4/8 bytes Return value (32/64-bits)
created using au_to_subject32(3) and au_to_subject64(3).
Field Bytes Description Token ID 1 byte Token ID Audit ID 4 bytes Audit user ID Effective User ID 4 bytes Effective user ID Effective Group ID 4 bytes Effective group ID Real User ID 4 bytes Real user ID Real Group ID 4 bytes Real group ID Process ID 4 bytes Process ID Session ID 4 bytes Audit session ID Terminal Port ID 4/8 bytes Terminal port ID (32/64-bits) Terminal Machine Address 4 bytes IP address of machine
Expanded Subject Token The "expanded subject" token consists of the same elements as the "subject" token, with the addition of type/length and variable size machine address information in the terminal ID. An "expanded subject" token can be created using au_to_subject32_ex(3) or au_to_subject64_ex(3).
Field Bytes Description Token ID 1 byte Token ID Audit ID 4 bytes Audit user ID Effective User ID 4 bytes Effective user ID Effective Group ID 4 bytes Effective group ID Real User ID 4 bytes Real user ID Real Group ID 4 bytes Real group ID Process ID 4 bytes Process ID Session ID 4 bytes Audit session ID Terminal Port ID 4/8 bytes Terminal port ID (32/64-bits) Terminal Address Type/Length 1 byte Length of machine address Terminal Machine Address 4 bytes IPv4 or IPv6 address of machine
System V IPC Token The "System V IPC" token contains the System V IPC message handle, semaphore handle or shared memory handle. A System V IPC token may be
Text Token The "text" token contains a single NUL-terminated text string. A "text" token may be created using au_to_text(3).
Field Bytes Description Token ID 1 byte Token ID Text Length 2 bytes Length of text string including NUL Text N bytes + 1 NUL Text string including NUL
Attribute Token The "attribute" token describes the attributes of a file associated with the audit event. As files may be identified by 0, 1, or many path names, a path name is not included with the attribute block for a file; optional "path" tokens may also be present in an audit record indicating which path, if any, was used to reach the object. An "attribute" token can be created using au_to_attr32(3) or au_to_attr64(3).
Field Bytes Description Token ID 1 byte Token ID File Access Mode 1 byte mode_t associated with file Owner User ID 4 bytes uid_t associated with file Owner Group ID 4 bytes gid_t associated with file File System ID 4 bytes fsid_t associated with file File System Node ID 8 bytes ino_t associated with file Device 4/8 bytes Device major/minor number (32/64-bit)
Groups Token The "groups" token contains a list of group IDs associated with the audit event. A "groups" token can be created using au_to_groups(3).
Field Bytes Description Token ID 1 byte Token ID Number of Groups 2 bytes Number of groups in token Group List N * 4 bytes List of N group IDs
System V IPC Permission Token The "System V IPC permission" token contains a System V IPC access permissions. A System V IPC permission token may be created using IPC owner Creator user ID 4 bytes User ID of IPC creator Creator group ID 4 bytes Group ID of IPC creator Access mode 4 bytes Access mode Sequence number 4 bytes Sequence number Key 4 bytes IPC key
Arg Token The "arg" token contains information about arguments of the system call. Depending on the size of the desired argument value, an Arg token may be created using au_to_arg32(3) or au_to_arg64(3).
Field Bytes Description Token ID 1 byte Token ID Argument ID 1 byte Argument ID Argument value 4/8 bytes Argument value Length 2 bytes Length of the text Text N bytes + 1 nul The string including nul
exec_args Token The "exec_args" token contains information about arguments of the exec() system call. An exec_args token may be created using au_to_exec_args(3).
Field Bytes Description Token ID 1 byte Token ID Count 4 bytes Number of arguments Text * bytes Count nul-terminated strings
exec_env Token The "exec_env" token contains current environment variables to an exec() system call. An exec_args token may be created using au_to_exec_env(3).
Field Bytes Description Token ID 1 byte Token ID Count ID 4 bytes Number of variables Text * bytes Count nul-terminated strings
Exit Token The "exit" token contains process exit/return code information. An "exit" token can be created using au_to_exit(3).
Field Bytes Description Token ID 1 byte Token ID Status 4 bytes Process status on exit
sockets. Each token has four or eight fields. Depending on the type of socket, a socket token may be created using au_to_sock_unix(3), au_to_sock_inet32(3) or au_to_sock_inet128(3).
Field Bytes Description Token ID 1 byte Token ID Socket family 2 bytes Socket family Local port 2 bytes Local port Socket address 4 bytes Socket address
Expanded Socket Token The "expanded socket" token contains information about IPv4 and IPv6 sockets. A "expanded socket" token can be created using au_to_socket_ex(3).
Field Bytes Description Token ID 1 byte Token ID Socket domain 2 bytes Socket domain Socket type 2 bytes Socket type Address type 2 byte Address type (IPv4/IPv6) Local port 2 bytes Local port Local IP address 4/16 bytes Local IP address Remote port 2 bytes Remote port Remote IP address 4/16 bytes Remote IP address
Seq Token The "seq" token contains a unique and monotonically increasing audit event sequence ID. Due to the limited range of 32 bits, serial number arithmetic and caution should be used when comparing sequence numbers.
Field Bytes Description Token ID 1 byte Token ID Sequence Number 4 bytes Audit event sequence number
privilege Token The "privilege" token ...
Field Bytes Description Token ID 1 byte Token ID
Use-of-auth Token The "use-of-auth" token ...
Field Bytes Description Token ID 1 byte Token ID
Command Token The "command" token ...
Field Bytes Description Token ID 1 byte Token ID
The "zonename" token holds a NUL-terminated string with the name of the zone or jail from which the record originated. A "zonename" token can be created using au_to_zonename(3).
Field Bytes Description Token ID 1 byte Token ID Zonename length 2 bytes Length of zonename string including NUL Zonename N bytes + 1 NUL Zonename string including NUL
SEE ALSO auditreduce(1), praudit(1), libbsm(3), audit(4), auditpipe(4), audit(8)
HISTORY The OpenBSM implementation was created by McAfee Research, the security division of McAfee Inc., under contract to Apple Computer Inc. in 2004. It was subsequently adopted by the TrustedBSD Project as the foundation for the OpenBSM distribution.
AUTHORS The Basic Security Module (BSM) interface to audit records and audit event stream format were defined by Sun Microsystems.
This manual page was written by Robert Watson <rwatson@FreeBSD.org>.
BUGS The "How to print" field in the "arbitrary data" token has undefined values.
The "in_addr" and "in_addr_ex" token layout documented here appears to be in conflict with the libbsm(3) implementation of au_to_in_addr_ex(3).
FreeBSD 14.0-RELEASE-p6 November 5, 2006 FreeBSD 14.0-RELEASE-p6