Manual Pages — AUDIT.LOG

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 Ta Bytes	Description
Token ID Ta 1 byte	Token ID
Seconds Ta 4 bytes	File time stamp
Microseconds Ta 4 bytes	File time stamp
File name length Ta 2 bytes	File name of audit trail
File pathname Ta 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 au_to_header64(3).

Field Ta Bytes	Description
Token ID Ta 1 byte	Token ID
Record Byte Count Ta 4 bytes	Number of bytes in record
Version Number Ta 2 bytes	Record version number
Event Type Ta 2 bytes	Event type
Event Modifier Ta 2 bytes	Event sub-type
Seconds Ta 4/8 bytes	Record time stamp (32/64-bits)
Nanoseconds Ta 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 Ta Bytes	Description
Token ID Ta 1 byte	Token ID
Record Byte Count Ta 4 bytes	Number of bytes in record
Version Number Ta 2 bytes	Record version number
Event Type Ta 2 bytes	Event type
Event Modifier Ta 2 bytes	Event sub-type
Address Type/Length Ta 1 byte	Host address type and length
Machine Address Ta 4/16 bytes	IPv4 or IPv6 address
Seconds Ta 4/8 bytes	Record time stamp (32/64-bits)
Nanoseconds Ta 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 Ta Bytes	Description
Token ID Ta 1 byte	Token ID
Trailer Magic Ta 2 bytes	Trailer magic number
Record Byte Count Ta 4 bytes	Number of bytes in record

Arbitrary Data Token

The "arbitrary data" token contains a byte stream of opaque (untyped) data. The size of the data is calculated as the size of each unit of data multiplied by the number of units of data. A "How to print" field is present to specify how to print the data, but interpretation of that field is not currently defined. An "arbitrary data" token can be created using au_to_data(3).

Field Ta Bytes	Description
Token ID Ta 1 byte	Token ID
How to Print Ta 1 byte	User-defined printing information
Basic Unit Ta 1 byte	Size of a unit in bytes
Unit Count Ta 1 byte	Number of units of data present
Data Items Ta 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 Ta Bytes	Description
Token ID Ta 1 byte	Token ID
IP Address Ta 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 Ta Bytes Description

Token ID Ta 1 byte Token ID

IP Address Type Ta 1 byte Type of address

IP Address Ta 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 Ta Bytes	Description
Token ID Ta 1 byte	Token ID
Version and IHL Ta 1 byte	Version and IP header length
Type of Service Ta 1 byte	IP TOS field
Length Ta 2 bytes	IP packet length in network byte order
ID Ta 2 bytes	IP header ID for reassembly
Offset Ta 2 bytes	IP fragment offset and flags, network byte order
TTL Ta 1 byte	IP Time-to-Live
Protocol Ta 1 byte	IP protocol number
Checksum Ta 2 bytes	IP header checksum, network byte order
Source Address Ta 4 bytes	IPv4 source address
Destination Address Ta 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 Ta Bytes	Description
Token ID Ta 1 byte	Token ID
Port Number Ta 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 Ta Bytes	Description
Token ID Ta 1 byte	Token ID
Path Length Ta 2 bytes	Length of path in bytes
Path Ta 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 Ta Bytes	Description
Token ID Ta 1 byte	Token ID
Count Ta 2 bytes	Number of NUL-terminated string(s) in token
Path Ta 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 Ta Bytes	Description
Token ID Ta 1 byte	Token ID
Audit ID Ta 4 bytes	Audit user ID
Effective User ID Ta 4 bytes	Effective user ID
Effective Group ID Ta 4 bytes	Effective group ID
Real User ID Ta 4 bytes	Real user ID
Real Group ID Ta 4 bytes	Real group ID
Process ID Ta 4 bytes	Process ID
Session ID Ta 4 bytes	Audit session ID
Terminal Port ID Ta 4/8 bytes	Terminal port ID (32/64-bits)
Terminal Machine Address Ta 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 Ta Bytes	Description
Token ID Ta 1 byte	Token ID
Audit ID Ta 4 bytes	Audit user ID
Effective User ID Ta 4 bytes	Effective user ID
Effective Group ID Ta 4 bytes	Effective group ID
Real User ID Ta 4 bytes	Real user ID
Real Group ID Ta 4 bytes	Real group ID
Process ID Ta 4 bytes	Process ID
Session ID Ta 4 bytes	Audit session ID
Terminal Port ID Ta 4/8 bytes	Terminal port ID (32/64-bits)
Terminal Address Type/Length Ta 1 byte	Length of machine address
Terminal Machine Address Ta 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 Ta Bytes	Description
Token ID Ta 1 byte	Token ID
Error Number Ta 1 byte	Errno value, or 0 if undefined
Return Value Ta 4/8 bytes	Return value (32/64-bits)

Subject Token

The "subject" token contains information on the subject performing the operation described by an audit record, and includes similar information to that found in the "process" and "expanded process" tokens. However, those tokens are used where the process being described is the target of the operation, not the authorizing party. A "subject" token can be created using au_to_subject32(3) and au_to_subject64(3).

Field Ta Bytes	Description
Token ID Ta 1 byte	Token ID
Audit ID Ta 4 bytes	Audit user ID
Effective User ID Ta 4 bytes	Effective user ID
Effective Group ID Ta 4 bytes	Effective group ID
Real User ID Ta 4 bytes	Real user ID
Real Group ID Ta 4 bytes	Real group ID
Process ID Ta 4 bytes	Process ID
Session ID Ta 4 bytes	Audit session ID
Terminal Port ID Ta 4/8 bytes	Terminal port ID (32/64-bits)
Terminal Machine Address Ta 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 Ta Bytes	Description
Token ID Ta 1 byte	Token ID
Audit ID Ta 4 bytes	Audit user ID
Effective User ID Ta 4 bytes	Effective user ID
Effective Group ID Ta 4 bytes	Effective group ID
Real User ID Ta 4 bytes	Real user ID
Real Group ID Ta 4 bytes	Real group ID
Process ID Ta 4 bytes	Process ID
Session ID Ta 4 bytes	Audit session ID
Terminal Port ID Ta 4/8 bytes	Terminal port ID (32/64-bits)
Terminal Address Type/Length Ta 1 byte	Length of machine address
Terminal Machine Address Ta 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 created using +.Xr au_to_ipc 3 .

Field Ta Bytes	Description
Token ID Ta 1 byte	Token ID
Object ID type Ta 1 byte	Object ID
Object ID Ta 4 bytes	Object ID

Text Token

The "text" token contains a single NUL-terminated text string. A "text" token may be created using au_to_text(3).

Field Ta Bytes	Description
Token ID Ta 1 byte	Token ID
Text Length Ta 2 bytes	Length of text string including NUL
Text Ta 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 Ta Bytes	Description
Token ID Ta 1 byte	Token ID
File Access Mode Ta 1 byte	mode_t associated with file
Owner User ID Ta 4 bytes	uid_t associated with file
Owner Group ID Ta 4 bytes	gid_t associated with file
File System ID Ta 4 bytes	fsid_t associated with file
File System Node ID Ta 8 bytes	ino_t associated with file
Device Ta 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 Ta Bytes	Description
Token ID Ta 1 byte	Token ID
Number of Groups Ta 2 bytes	Number of groups in token
Group List Ta 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 au_to_ipc_perm(3).

Field Ta Bytes	Description
Token ID Ta 1 byte	Token ID
`Owner user ID`	4 bytes	User ID of IPC owner
`Owner group ID`	4 bytes	Group ID of 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 Ta Bytes	Description
Token ID Ta 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 Ta Bytes	Description
Token ID Ta 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 Ta Bytes	Description
Token ID Ta 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 Ta Bytes	Description
Token ID Ta 1 byte	Token ID
Status Ta 4 bytes	Process status on exit
Return Value Ta 4 bytes	Process return value on exit

Socket Token

The "socket" token contains information about UNIX domain and Internet 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 Ta 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 Ta Bytes	Description
Token ID Ta 1 byte	Token ID
Sequence Number Ta 4 bytes	Audit event sequence number

privilege Token

The "privilege" token ...

Field Ta Bytes	Description
Token ID Ta 1 byte	Token ID

Use-of-auth Token

The "use-of-auth" token ...

Field Ta Bytes	Description
Token ID Ta 1 byte	Token ID

Command Token

The "command" token ...

Field Ta Bytes	Description
Token ID Ta 1 byte	Token ID

ACL Token

The "ACL" token ...

Field Ta Bytes	Description
Token ID Ta 1 byte	Token ID

Zonename Token

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 Ta Bytes	Description
Token ID Ta 1 byte	Token ID
Zonename length Ta 2 bytes	Length of zonename string including NUL
Zonename Ta N bytes + 1 NUL	Zonename string including NUL

HISTORY

The OpenBSM implementation was created by McAfee Research, the security division of McAfee Inc., under contract to Apple Computer Inc.amp; 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).

AUDIT.LOG (5)

November 5, 2006

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