NAME
ausearch-expression - audit search expression format
OVERVIEW
This man page describes the format of "ausearch expressions". Parsing and evaluation of these expressions is provided by libauparse and is common to applications that use this library.
LEXICAL STRUCTURE
White space (ASCII space, tab and new-line characters) between tokens is ignored. The following tokens are recognized:
| Punctuation | |
| ( ) \
| |
| Logical operators | |
| ! && ||
| |
| Comparison operators | |
| < <= == > >= !== i= i!= r= r!=
| |
| Unquoted strings | |
| Any non-empty sequence of ASCII letters, digits, and the
_ symbol.
| |
| Quoted strings | |
| A sequence of characters surrounded by the
\(dq quotes.
The
\ character starts an escape sequence.
The only defined escape sequences are
\\ and \\(dq.
The semantics of other escape sequences is undefined.
| |
EXPRESSION SYNTAX
The primary expression has the following form:
| field comparison-operator value | |
|
field is either a string,
which specifies the first field with that name within the current audit record,
or the
\ escape character followed by a string,
which specifies a virtual field with the specified name
(virtual fields are defined in a later section).
field is a string. operator specifies the comparison to perform
| |
| r= r!= | Get the "raw" string of field,
and compare it to value.
For fields in audit records,
the "raw" string is the exact string stored in the audit record
(with all escaping and unprintable character encoding left alone);
applications can read the "raw" string using
auparse_get_field_str(3).
Each virtual field may define a "raw" string.
If
field is not present or does not define a "raw" string,
the result of the comparison is
false (regardless of the operator).
|
| i= i!= | Get the "interpreted" string of field,
and compare it to value.
For fields in audit records,
the "interpreted" string is an "user-readable" interpretation of the field
value;
applications can read the "interpreted" string using
auparse_interpret_field(3).
Each virtual field may define an "interpreted" string.
If
field is not present or does not define an "interpreted" string,
the result of the comparison is
false (regardless of the operator).
|
| < <= == > >= !== | |
| Evaluate the "value" of field, and compare it to value.
A "value" may be defined for any field or virtual field,
but no "value" is currently defined for any audit record field.
The rules of parsing value for comparing it with the "value" of
field are specific for each field.
If
field is not present,
the result of the comparison is
false (regardless of the operator).
If
field does not define a "value", an error is reported when parsing the expression.
| |
VIRTUAL FIELDS
The following virtual fields are defined:
| \timestamp | |
| The value is the timestamp of the current event.
value must have the ts:seconds.milli format, where
seconds and
milli are decimal numbers specifying the seconds and milliseconds part of the
timestamp, respectively.
| |
| \record_type | |
| The value is the type of the current record.
value is either the record type name, or a decimal number specifying the type.
| |
SEMANTICS
The expression as a whole applies to a single record. The expression is true for a specified event if it is true for any record associated with the event.
EXAMPLES
As a demonstration of the semantics of handling missing fields, the following expression is true if field is present:
| (field r= \(dq\(dq) || (field r!= \(dq\(dq) | |
FUTURE DIRECTIONS
New escape sequences for quoted strings may be defined.
For currently defined virtual fields that do not define a "raw" or "interpreted" string, the definition may be added. Therefore, don’t rely on the fact that comparing the "raw" or "interpreted" string of the field with any value is false.
New formats of value constants for the \timestamp virtual field may be added.
AUTHOR
Miloslav Trmac
