The following is a description of the elements, types, and attributes that compose the core schema for encoding Open Vulnerability and Assessment Language (OVAL) Definitions. Some of the objects defined here are extended and enhanced by individual component schemas, which are described in separate documents. Each of the elements, types, and attributes that make up the Core Definition Schema are described in detail and should provide the information necessary to understand what each represents. This document is intended for developers and assumes some familiarity with XML. A high level description of the interaction between these objects is not outlined here.
The OVAL Schema is maintained by The MITRE Corporation and developed by the public OVAL Community. For more information, including how to get involved in the project and how to submit change requests, please visit the OVAL website at http://oval.mitre.org.
The oval_definitions element is the root of an OVAL Definition Document. Its purpose is to bind together the major sections of a document - generator, definitions, tests, objects, states, and variables - which are the children of the root element.
Child Elements Type MinOccurs MaxOccurs generator oval:GeneratorType 1 1 definitions oval-def:DefinitionsType 0 1 tests oval-def:TestsType 0 1 objects oval-def:ObjectsType 0 1 states oval-def:StatesType 0 1 variables oval-def:VariablesType 0 1 ds:Signature n/a 0 1
The DefinitionsType complex type is a container for one or more definition elements. Each definition element describes a single OVAL Definition. Please refer to the description of the DefinitionType for more information about an individual definition.
Child Elements Type MinOccurs MaxOccurs definition oval-def:DefinitionType 1 unbounded
The DefinitionType defines a single OVAL Definition. A definition is the key structure in OVAL. It is analogous to the logical sentence or proposition: if a computer's state matches the configuration parameters laid out in the criteria, then that computer exhibits the state described. The DefinitionType contains a section for various metadata related elements that describe the definition. This includes a description, version, affected system types, and reference information. The notes section of a definition should be used to hold information that might be helpful to someone examining the technical aspects of the definition. For example, why certain tests have been included in the criteria, or maybe a link to where further information can be found. The DefinitionType also (unless the definition is deprecated) contains a criteria child element that joins individual tests together with a logical operator to specify the specific computer state being described.
The required id attribute is the OVAL-ID of the Definition. The form of an OVAL-ID must follow the specific format described by the definitionidPattern. The required version attribute holds the current version of the definition. Versions are integers, starting at 1 and incrementing every time a definition is modified. The required class attribute indicates the specific class to which the definition belongs. The class gives a hint to a user so they can know what the definition writer is trying to say. See the definition of classEnumeration for more information about the different valid classes. The optional deprecated attribute signifies that an id is no longer to be used or referenced but the information has been kept around for historic purposes.
Attributes:
- id oval:DefinitionIDPattern (required) - version xsd:nonNegativeInteger (required) - class oval-def:ClassEnumeration (required) - deprecated xsd:boolean (optional -- default='false')
Child Elements Type MinOccurs MaxOccurs ds:Signature n/a 0 1 metadata oval-def:MetadataType 1 1 notes oval-def:NotesType 0 1 criteria oval-def:CriteriaType 0 1
The MetadataType complex type contains all the metadata available to an OVAL Definition. This metadata is for informational purposes only and is not part of the criteria used to evaluate machine state. The required title child element holds a short string that is used to quickly identify the definition to a human user. The affected metadata item contains information about the system(s) for which the definition has been written. Remember that this is just metadata and not part of the criteria. Please refer to the AffectedType description for more information. The required description element contains a textual description of the configuration state being addressed by the OVAL Definition. In the case of a definition from the vulnerability class, the reference is usually the Common Vulnerability and Exposures (CVE) Identifier, and this description field corresponds with the CVE description.
Additional metadata is also allowed although it is not part of the official OVAL Schema. Individual organizations can place metadata items that they feel are important and these will be skipped during the validation. All OVAL really cares about is that the stated metadata items are there.
Child Elements Type MinOccurs MaxOccurs title xsd:string 1 1 affected oval-def:AffectedType 0 unbounded reference oval-def:ReferenceType 0 unbounded description xsd:string 1 1
Each OVAL Definition is written to evaluate a certain type of system(s). The family, platform(s), and product(s) of this target are described by the AffectedType whose main purpose is to provide hints for tools using OVAL Definitions. For instance, to help a reporting tool only use Windows definitions, or to preselect only Red Hat definitions to be evaluated. Note, the inclusion of a particular platform or product does not mean the definition is physically checking for the existence of the platform or product. For the actual test to be performed, the correct test must still be included in the definition's criteria section.
The AffectedType complex type details the specific system, application, subsystem, library, etc. for which a definition has been written. If a definition is not tied to a specific product, then this element should not be included. The absence of the platform or product element can be thought of as definition applying to all platforms or products. The inclusion of a particular platform or product does not mean the definition is physically checking for the existence of the platform or product. For the actual test to be performed, the correct test must still be included in the definition's criteria section. To increase the utility of this element, care should be taken when assigning and using strings for product names. The schema places no restrictions on the values that can be assigned, potentially leading to many different representations of the same value. For example 'Internet Explorer' and 'IE'. The current convention is to fully spell out all terms, and avoid the use of abbreviations at all costs.
Please note that the AffectedType will change in future versions of OVAL in order to support the Common Platform Enumeration (CPE).
Attributes:
- family oval:FamilyEnumeration (required)
Child Elements Type MinOccurs MaxOccurs platform xsd:string 0 unbounded product xsd:string 0 unbounded
The ReferenceType complex type links the OVAL Definition to a definitive external reference. For example, CVE Identifiers for vulnerabilities. The intended purpose for this reference is to link the definition to a variety of other sources that address the same issue being specified by the OVAL Definition.
The required source attribute specifies where the reference is coming from. In other words, it identifies the reference repository being used. The required ref_id attribute is the external id of the reference. The optional ref_url attribute is the URL to the reference.
Attributes:
- source xsd:string (required) - ref_id xsd:string (required) - ref_url xsd:anyURI (optional)
The NotesType complex type is a container for one or more note child elements. Each note contains some information about the definition or tests that it references. A note may record an unresolved question about the definition or test or present the reason as to why a particular approach was taken.
Child Elements Type MinOccurs MaxOccurs note xsd:string 1 unbounded
The CriteriaType complex type describes the high level container for all the tests and represents the meat of the definition. Each criteria can contain other criteria elements in a recursive structure allowing complex logical trees to be constructed. Each referenced test is represented by a criterion element. Please refer to the description of the CriterionType for more information about and individual criterion element. The optional extend_definition element allows existing definitions to be included in the criteria. Refer to the description of the ExtendDefinitionType for more information.
The required operator attribute provides the logical operator that binds the different statements inside a criteria together. The optional negate attribute signifies that the result of the criteria as a whole should be negated during analysis. For example, consider a criteria that evaluates to TRUE if a certain software is installed. By negating this test, it now evaluates to TRUE if the software is NOT installed. The optional comment attribute provides a short description of the criteria.
Attributes:
- operator oval:OperatorEnumeration (optional -- default='AND') - negate xsd:boolean (optional -- default='false') - comment oval:NonEmptyStringType (optional)
Child Elements Type MinOccurs MaxOccurs criteria oval-def:CriteriaType 1 1 criterion oval-def:CriterionType 1 1 extend_definition oval-def:ExtendDefinitionType 1 1
The CriterionType complex type identifies a specific test to be included in the definition's criteria.
The required test_ref attribute is the actual id of the test being referenced. The optional negate attribute signifies that the result of an individual test should be negated during analysis. For example, consider a test that evaluates to TRUE if a specific patch is installed. By negating this test, it now evaluates to TRUE if the patch is NOT installed. The optional comment attribute provides a short description of the specified test and should mirror the comment attribute of the actual test.
Attributes:
- test_ref oval:TestIDPattern (required) - negate xsd:boolean (optional -- default='false') - comment oval:NonEmptyStringType (optional)
The ExtendDefinitionType complex type allows existing definitions to be extended by another definition. This works by evaluating the extended definition and then using the result within the logical context of the extending definition.
The required definition_ref attribute is the actual id of the definition being extended. The optional negate attribute signifies that the result of an extended definition should be negated during analysis. For example, consider a definition that evaluates TRUE if a certain software is installed. By negating the definition, it now evaluates to TRUE if the software is NOT installed. The optional comment attribute provides a short description of the specified definition and should mirror the title metadata of the extended definition.
Attributes:
- definition_ref oval:DefinitionIDPattern (required) - negate xsd:boolean (optional -- default='false') - comment oval:NonEmptyStringType (optional)
The TestsType complex type is a container for one or more test child elements. Each test element describes a single OVAL Test. Please refer to the description of the TestType for more information about an individual test.
Child Elements Type MinOccurs MaxOccurs oval-def:test n/a 1 unbounded
The test element is an abstract element that is meant to be extended (via substitution groups) by the individual tests found in the component schemas. An OVAL Test is used to compare an object(s) against a defined state. An actual test element is not valid. The use of this abstract class simplifies the OVAL schema by allowing individual tests to inherit the optional notes child element, and the id and comment attributes from the base TestType. Please refer to the description of the TestType complex type for more information.
The base type of every test includes an optional notes element and five attributes. The notes section of a test should be used to hold information that might be helpful to someone examining the technical aspects of the test. For example, why certain values have been used by the test, or maybe a link to where further information can be found. Please refer to the description of the NotesType complex type for more information about the notes element. The required comment attribute provides a short description of the test. The optional deprecated attribute signifies that an id is no longer to be used or referenced but the information has been kept around for historic purposes.
The required id attribute uniquely identifies each test, and must conform to the format specified by the TestIdPattern simple type. The required version attribute holds the current version of the test. Versions are integers, starting at 1 and incrementing every time a test is modified.
The optional check_existence attribute determines how many items in the specified set must exist for the test to evaluate to true. For example, if a value of 'all_exist' is given, every item defined by the OVAL Object must exist on the system for the test to evaluate to true. If the OVAL Object uses a variable reference, then every value of that variable must exist. Note that a pattern match defines a set of matching objects found on a system. So when check_existence = 'all_exist' and a regex matches anything on a system the test will evaluate to true (since all matching objects on the system were found on the system). When check_existence = 'all_exist' and a regex does not match anything on a system the test will evaluate to false. Also note that you only need to evaluate the state condition if the existence check evaluates to true.
The required check attribute determines how many items that match the object definition (ignoring items with a status of Does Not Exist) must satisfy the state requirements. For example: Should the test check that all matching files have a specified version or that at least one file has the specified version? The valid check values are explained in the description of the CheckEnumeration simple type. Note that if the test does not contain any references to OVAL States, then the check attribute has no meaning and can be ignored during evaluation.
The check and check_existence attributes must both be satisfied during evaluation for the test to evaluate to true. For example, if the check_existence fails then there is no need to evaluate the check since the test will have a result of false no matter what.
The optional state_operator attribute provides the logical operator that combines the evaluation results from each referenced state on a per item basis. Each matching item is compared to each referenced state. The result of comparing each state to a single item is combined based on the specified state_operator value to determine one result for each item. Finally, the results for each item are combined based on the specified check value. Note that if the test does not contain any references to OVAL States, then the state_operator attribute has no meaning and can be ignored during evaluation. Referencing multiple states in one test allows ranges of possible values to be expressed. For example, one state can check that a value greater than 8 is found and another state can check that a value of less than 16 is found. In this example the referenced states are combined with a state_operator = 'AND' indicating that the conditions of all referenced states must be satisfied and that the value must be between 8 AND 16. The valid state_operation values are explained in the description of the OperatorEnumeration simple type.
Attributes:
- id oval:TestIDPattern (required) - version xsd:nonNegativeInteger (required) - check_existence oval:ExistenceEnumeration (optional -- default='at_least_one_exists') - check oval:CheckEnumeration (required) - state_operator oval:OperatorEnumeration (optional -- default='AND') - comment oval:NonEmptyStringType (required) - deprecated xsd:boolean (optional -- default='false')
Child Elements Type MinOccurs MaxOccurs ds:Signature n/a 0 1 notes oval-def:NotesType 0 1
The ObjectRefType complex type defines an object reference to be used by OVAL Tests that are defined in the component schemas. The required object_ref attribute specifies the id of the OVAL Object being referenced.
Attributes:
- object_ref oval:ObjectIDPattern (required)
The StateRefType complex type defines a state reference to be used by OVAL Tests that are defined in the component schemas. The required state_ref attribute specifies the id of the OVAL State being referenced.
Attributes:
- state_ref oval:StateIDPattern (required)
The ObjectsType complex type is a container for one or more object child elements. Each object element provides details that define a set of matching objects to be used by an OVAL Test. Please refer to the description of the object element for more information about an individual object.
Child Elements Type MinOccurs MaxOccurs oval-def:object n/a 1 unbounded
The object element is an abstract element that is meant to be extended (via substitution groups) by the objects found in the component schemas. An actual object element is not valid. The use of this abstract class simplifies the OVAL schema by allowing individual objects to inherit any common elements and attributes from the base ObjectType. The optional notes child element, and the id and comment attributes from the base testType. A description of the notes element can be found under the definitions section. Please refer to the description of the ObjectType complex type for more information.
An OVAL Object describes a set of items to look for on a system. A simple object will usually result in a single file, process, etc being identified. But through the use pattern matches, sets, and variables, multiple matching objects can be identified. Therefore an OVAL Object can identify a set of many individual items on a system. This set of items defined by the OVAL Object can then be used by an OVAL Test and compared against an OVAL State.
The base type of every object includes an optional notes element. The notes element of an object should be used to hold information that might be helpful to someone examining the technical aspects of the object. For example, why certain values have been used, or maybe a link to where further information can be found. Please refer to the description of the NotesType complex type for more information about the notes element.
The required id attribute uniquely identifies each object, and must conform to the format specified by the objectidPattern simple type. The required version attribute holds the current version of the object element. Versions are integers, starting at 1 and incrementing every time an object is modified. The optional comment attribute provides a short description of the object. The optional deprecated attribute signifies that an id is no longer to be used or referenced but the information has been kept around for historic purposes.
Attributes:
- id oval:ObjectIDPattern (required) - version xsd:nonNegativeInteger (required) - comment oval:NonEmptyStringType (optional) - deprecated xsd:boolean (optional -- default='false')
Child Elements Type MinOccurs MaxOccurs ds:Signature n/a 0 1 notes oval-def:NotesType 0 1
The set element enables complex objects to be described. It is a recursive element in that each set element can contain additional set elements as children. Each set element defines characteristics that produce a matching set of objects. The possible characteristics are an object reference and a collection of filters. The object_reference refers to an existing OVAL Object. The filter element provides a reference to an existing OVAL State. A filter is used to eliminate certain objects from the set. Each filter is applied to each OVAL Object before the set_operator is applied. For example, if an object_reference points to an OVAL Object that is every file in a certain directory, a filter might be set up to limit the object set to only those files with a size less than 10 KB. If multiple filters are provided, then each filter is used separately against the defined object set. In other words, if an object matches any of the supplied filters, then it is thrown out of the set.
The required set_operator attribute defines how different child sets are combined to form the overall set of objects. For example, does one take the union of different sets or the intersection? For a description of the valid values please refer to the SetOperatorEnumeration simple type.
Attributes:
- set_operator oval-def:SetOperatorEnumeration (optional -- default='UNION')
Child Elements Type MinOccurs MaxOccurs object_reference oval:ObjectIDPattern 1 2 filter oval:StateIDPattern 0 unbounded
The StatesType complex type is a container for one or more state child elements. Each state provides details about specific characteristics that can be used during an evaluation of an object. Please refer to the description of the state element for more information about an individual state.
Child Elements Type MinOccurs MaxOccurs oval-def:state n/a 1 unbounded
The state element is an abstract element that is meant to be extended (via substitution groups) by the states found in the component schemas. An actual state element is not valid. The use of this abstract class simplifies the OVAL schema by allowing individual states to inherit the optional notes child element, and the id and operator attributes from the base StateType. Please refer to the description of the StateType complex type for more information.
An OVAL State is a collection of one or more characteristics pertaining to a specific object type. The OVAL State is used by an OVAL Test to determine if a set of items identified on a system meet certain characteristics.
The base type of every state includes an optional notes element and two attributes. The notes section of a state should be used to hold information that might be helpful to someone examining the technical aspects of the state. For example, why certain values have been used by the state, or maybe a link to where further information can be found. Please refer to the description of the NotesType complex type for more information about the notes element.
The required id attribute uniquely identifies each state, and must conform to the format specified by the stateidPattern simple type. The required version attribute holds the current version of the state. Versions are integers, starting at 1 and incrementing every time a state is modified. The required operator attribute provides the logical operator that binds the different characteristics inside a state together. The optional comment attribute provides a short description of the state. The optional deprecated attribute signifies that an id is no longer to be used or referenced but the information has been kept around for historic purposes.
When evaluating a particular state against an object, one should evaluate each individual entity separately. The individual results are then combined by the operator to produce an overall result. This process holds true even when there are multiple instances of the same entity. Evaluate each instance separately, taking the entity check attribute into account, and then combine everything using the operator.
Attributes:
- id oval:StateIDPattern (required) - version xsd:nonNegativeInteger (required) - operator oval:OperatorEnumeration (optional -- default='AND') - comment oval:NonEmptyStringType (optional) - deprecated xsd:boolean (optional -- default='false')
Child Elements Type MinOccurs MaxOccurs ds:Signature n/a 0 1 notes oval-def:NotesType 0 1
The VariablesType complex type is a container for one or more variable child elements. Each variable element is a way to define one or more values to be obtained at the time a definition is evaluated.
Child Elements Type MinOccurs MaxOccurs oval-def:variable n/a 1 unbounded
The variable element is an abstract element that is meant to be extended (via substitution groups) by the different types of variables. An actual variable element is not valid. The different variable types describe different sources for obtaining a value(s) for the variable. There are currently three types of variables; local, external, and constant. Please refer to the description of each one for more specific information. The value(s) of a variable is treated as if it were inserted where referenced. One of the main benefits of variables is that they allow tests to evaluate user-defined policy. For example, an OVAL Test might check to see if a password is at least a certain number of characters long, but this number depends upon the individual policy of the user. To solve this, the test for password length can be written to refer to a variable element that defines the length.
If a variable defines an array of values, any entity that references the variable will evaluate to true depending on the value of the var_check attribute. For example, if an entity 'size' with an operation of 'less than' references a variable that returns five different integers, and the var_check attribute has a value of 'all', then the 'size' entity returns true only if the actual size is less than each of the five integers defined by the variable. If a variable does not return any value, then an error should be reported during OVAL analysis.
The VariableType complex type defines attributes associated with each OVAL Variable. The required id attribute uniquely identifies each variable, and must conform to the format specified by the VariableIDPattern simple type. The required version attribute holds the current version of the variable. Versions are integers, starting at 1 and incrementing every time a variable is modified. The required comment attribute provides a short description of the variable. The optional deprecated attribute signifies that an id is no longer to be used or referenced but the information has been kept around for historic purposes.
The required datatype attribute specifies the type of value being defined. The set of values identified by a variable must comply with the specified datatype, otherwise an error should be reported. Please see the DatatypeEnumeration for details about each valid datatype. For example, if the datatype of the variable is specified as boolean then the value(s) returned by the component / function should be "true", "false", "1", or "0".
Attributes:
- id oval:VariableIDPattern (required) - version xsd:nonNegativeInteger (required) - datatype oval:DatatypeEnumeration (required) - comment oval:NonEmptyStringType (required) - deprecated xsd:boolean (optional -- default='false')
Child Elements Type MinOccurs MaxOccurs ds:Signature n/a 0 1
The external_variable element extends the VariableType and defines a variable with some external source. The actual value(s) for the variable is not provided within the OVAL file, but rather it is retrieved during the evaluation of the OVAL Definition from an external source. An unbounded set of possible-value and possible_restriction child elements can be specified that together specify the list of all possible values that an external source is allowed to supply for the external variable. In other words, the value assigned by an external source must match one of the possible_value or possible_restriction elements specified. Each possible_value element contains a single value that could be assigned to the given external_variable while each possible_restriction element outlines a range of possible values. Note that it is not necessary to declare a variable's possible values, but the option is available if desired. If no possible child elements are specified, then the valid values are only bound to the specified datatype of the external variable. Please refer to the description of the PossibleValueType and PossibleRestrictionType complex types for more information.
The PossibleValueType complex type is used to outline a single expected value of an external variable. The required hint attribute gives a short description of what the value means or represents.
Attributes:
- hint xsd:string (required)
Simple Content xsd:anySimpleType
The PossibleRestrictionType complex type outlines a range of possible expected value of an external variable. Each possible_restriction element contains an unbounded list of child restriction elements that each specify a range that an actual value may fall in. For example, a restriction element my specify that a value must be less than 10. When multiple restriction elements are present, a valid possible value would have to meet every restriction. One can think of the possible_value and possible_restriction elements as an OR'd list of possible values, and the restriction elements as an AND'd list of value descriptions. Please refer to the description of the RestrictionType complex type for more information. The required hint attribute gives a short description of what the value means or represents.
Attributes:
- hint xsd:string (required)
Child Elements Type MinOccurs MaxOccurs restriction oval-def:RestrictionType 1 unbounded
The RestrictionType complex type outlines a restriction that is placed on expected values for an external variable. For example, a possible value may be restricted to a integer less than 10. Please refer to the operationEnumeration simple type for a description of the valid operations. The required hint attribute gives a short description of what the value means or reporesents.
Attributes:
- operation oval:OperationEnumeration (required)
Simple Content xsd:anySimpleType
The constant_variable element extends the VariableType and defines a variable with a constant value(s). Each constant_variable defines either a single value or an array of values to be used throughout the evaluation of the OVAL Definition File in which it has been defined. Constant variables can not be over-ridden by an external source. The actual value of a constant variable is defined by the required value child element. An array of values can be specified by including multiple instances of the value element. Please refer to the description of the ValueType complex type for more information.
Child Elements Type MinOccurs MaxOccurs value oval-def:ValueType 1 unbounded
The ValueType complex type holds the actual value of the variable when dealing with a constant variable. This value should be used by all tests that reference this variable. The value can not be over-ridden by an external source.
Attributes:
Simple Content xsd:anySimpleType
The local_variable element extends the VariableType and defines a variable with some local source. The actual value(s) for the variable is not provided in the OVAL Definition document but rather it is retrieved during the evaluation of the OVAL Definition. Each local variable is defined by either a single component or a complex function, meaning that a value can be as simple as a literal string or as complex as multiple registry keys concatenated together. Note that if an individual component is used and it returns multiple values, then there will be multiple values associated with the local_variable. For example, if an object_component is used and it references a file object that identifies a set of 5 files, then the local variable would represent these 5 values. Please refer to the description of the ComponentGroup for more information.
Child Elements Type MinOccurs MaxOccurs oval-def:ComponentGroup n/a 1 1
Any value that is pulled directly off the local system is defined by the basic component element. For example, the name of a user or the value of a registry key. Please refer to the definition of the ObjectComponentType for more information. A value can also be obtained from another variable. The variable element identifies a variable id to pull a value(s) from. Please refer to the definition of the VariableComponentType for more information. Literal values can also be specified.
Child Elements Type MinOccurs MaxOccurs object_component oval-def:ObjectComponentType 1 1 variable_component oval-def:VariableComponentType 1 1 literal_component oval-def:LiteralComponentType 1 1 oval-def:FunctionGroup n/a 1 1
The LiteralComponentType complex type defines a literal value to be used as a component. The otpional datatype attribute defines the type of data expected. The default datatype is 'string'.
Attributes:
- datatype oval:DatatypeEnumeration (optional -- default='string')
Simple Content xsd:anySimpleType
The ObjectComponentType complex type defines a specific value on the local system to obtain. The required object_ref attribute provides a reference to an existing OVAL Object declaration. This reference defines the object to examine and eventually pull the value from. The required item_field defines which piece of data to retrieve from the object referenced by the object_ref. For example, if the object_ref references a file_object, the item_field may define the version entity as the piece of information to use as the value of the variable. The types of data to retrieve can be found in the OVAL System Characteristics file under the item associated with the object referenced by object_ref.
Attributes:
- object_ref oval:ObjectIDPattern (required) - item_field xsd:string (required)
The VariableComponentType complex type defines a specific value obtained by looking at the value of another OVAL Variable. The required var_ref attribute provides a reference to the variable. One must make sure that the variable reference does not point to the parent variable that uses this component to avoid a race condition.
Attributes:
- var_ref oval:VariableIDPattern (required)
Complex functions have been defined that help determine how to manipulate specific values. These functions can be nested together to form complex statements. Each function is designed to work on a specific type of data. If the data being worked on is not of the correct type, a cast should be attempted before reporting an error. For example, if a concat function includes a registry component that returns an integer, then the integer should be cast as a string in order to work with the concat function. Note that if the operation being applied to the variable by the calling entity is "pattern match", then all the functions are performed before the regular expression is evaluated. In short, the variable would produce a value as normal and then any pattern match operation would be performed. It is also important to note that when using these functions with sub-components that return multiple values that the operation will be performed on the Cartesian product of the components and the result is an array of values. For example, assume a local_variable specifies the arithmetic function with an arithmetic_operation of "add" and has two sub-components under this function: the first component returns multiple values "1" and "2", and the second component returns multiple values "3" and "4" and "5". The local_variable element would be evaluated to have six values: 1+3, 1+4, 1+5, 2+3, 2+4, and 2+5. Please refer to the description of a specific function for more details about it.
Child Elements Type MinOccurs MaxOccurs arithmetic oval-def:ArithmeticFunctionType 1 1 begin oval-def:BeginFunctionType 1 1 concat oval-def:ConcatFunctionType 1 1 end oval-def:EndFunctionType 1 1 escape_regex oval-def:EscapeRegexFunctionType 1 1 split oval-def:SplitFunctionType 1 1 substring oval-def:SubstringFunctionType 1 1 time_difference oval-def:TimeDifferenceFunctionType 1 1 regex_capture oval-def:RegexCaptureFunctionType 1 1
The arithmetic function takes two or more integer or float components and performs a basic mathmetical function on them. The result of this function in a single integer or float unless one of the components returns multiple values. In this case the specified arithmetic function would be performed multiple times and the end result would be an array of values for the local variable. For example assume a local_variable specifies the arithmetic function with an arithmetic_operation of "add" and has two sub-components under this function: the first component returns multiple values "1" and "2", and the second component returns multiple values "3" and "4" and "5". The local_variable element would be evaluated to have six values: 1+3, 1+4, 1+5, 2+3, 2+4, and 2+5.
Note that if both an integer and float components are used then the result is a float.
Attributes:
- arithmetic_operation oval-def:ArithmeticEnumeration (required)
Child Elements Type MinOccurs MaxOccurs oval-def:ComponentGroup n/a 1 1
The begin function takes a single string component and defines a character (or string) that the component string should start with. The character attribute defines the specific character (or string). The character (or string) is only added to the component string if the component string doesn't already start with the specified character (or string).
Attributes:
- character xsd:string (required)
Child Elements Type MinOccurs MaxOccurs oval-def:ComponentGroup n/a 1 1
The concat function takes two or more components and concatenates them together to form a single string. The first component makes up the begining of the resulting string and any following components are added to the end it. If one of the components returns multiple values then the concat function would be performed multiple times and the end result would be an array of values for the local variable. For example assume a local variable has two sub-components: a basic component element returns the values "abc" and "def", and a literal component element that has a value of "xyz". The local_variable element would be evaluated to have two values, "abcxyz" and "defxyz". If one of the components does not exist, then the result of the concat operation should be does not exist.
Child Elements Type MinOccurs MaxOccurs oval-def:ComponentGroup n/a 1 1
Below is a chart that specifies how to classify the flag status of a variable using the concat function during evaluation when multiple components are supplied. Both the object and variable component are indirectly associated with collected objects in a system characteristics file. These objects could have been completely collected from the system, or there might have been some type of error that led to the object not being collected, or maybe only a part of the object set was collected. This flag status is important as OVAL Objects or OVAL State that are working with a variable (through the var_ref attribute on an entity) can use this information to report more accurate results. For example, an OVAL Test with a check attribute of 'at least one' that specifies an object with a variable reference, might be able to produce a valid result based on an incomplete object set as long as one of the objects in the set is true.
|| num of components with flag || || || resulting flag is || E | C | I | DNE | NC | NA || ------||-----------------------------------||------------------ || 1+ | 0+ | 0+ | 0+ | 0+ | 0+ || Error || 0 | 1+ | 0 | 0 | 0 | 0 || Complete || 0 | 0+ | 1+ | 0 | 0 | 0 || Incomplete || 0 | 0+ | 0+ | 1+ | 0 | 0 || Does Not Exist || 0 | 0+ | 0+ | 0+ | 1+ | 0 || Not Collected || 0 | 0+ | 0+ | 0+ | 0+ | 1+ || Not Applicable ------||-----------------------------------||------------------
The end function takes a single string component and defines a character (or string) that the component string should end with. The character attribute defines the specific character (or string). The character (or string) is only added to the component string if the component string doesn't already end with the specified character (or string). If the desired end character is a string, then the entire end string must exist at the end if the component string. If the entire end string is not presnet then the entire end string is appended to the component string.
Attributes:
- character xsd:string (required)
Child Elements Type MinOccurs MaxOccurs oval-def:ComponentGroup n/a 1 1
The escape_regex function takes a single string component and escapes all the regular expression characters. The purpose for this is that many times, a component used in pattern match needs to be treated as a literal string and not a regular expression. For example, assume a basic component element that identifies a file path that is held in the Windows registry. This path is a string that might contain regular expression characters. These characters are likely not intended to be treated as regular expression characters and need to be escaped. This function allows a definition writer to mark convert the values of components to regular expression format.
Note that when using regular expressions, OVAL supports a common subset of the regular expression character classes, operations, expressions and other lexical tokens defined within Perl 5's regular expression specification. For more information on the supported regular expression syntax in OVAL see: http://oval.mitre.org/language/about/re_support_5.6.html.
Child Elements Type MinOccurs MaxOccurs oval-def:ComponentGroup n/a 1 1
The split function takes a single string component and turns it into multiple values based on a delimiter string. For example, assume that a basic component element returns the value "a-b-c-d" to the split function with the delimiter set to "-". The local_variable element would be evaluated to have four values "a", "b", "c", and "d". If the basic component returns a value that begins, or ends, with a delimiter, the local_variable element would contain empty string values at the beginning, or end, of the set of values returned for that string component. For example, if the delimiter is "-", and the basic component element returns the value "-a-a-", the local_variable element would be evaluated to have four values "", "a", "a", and "". Likewise, if the basic component element returns a value that contains adjacent delimiters such as "---", the local_variable element would be evaluated to have four values "", "", "", and "". Lastly, if the basic component element used by the split function returns multiple values, then the split function is performed multiple times, and all of the results, from each of the split functions, are returned.
Attributes:
- delimiter xsd:string (required)
Child Elements Type MinOccurs MaxOccurs oval-def:ComponentGroup n/a 1 1
The substring function takes a single string component and produces a single value that contains a portion of the original string. The substring_start attribute defines the starting position in the original string. Note, to include the first character of the string, the start position would be 1. Also note that a value less than one also means starting at the first character of the string. The substring_length attribute defines how many character after and including the starting character to include. Note that a substring_length value greater than the actual length of the string or a negative value means to include all the characters after the starting character. For example assume a basic component element that returns the value "abcdefg" with a substring_start value of 3 and a substring_length value of 2. The local_variable element would be evaluate to have a single value of "cd". If the string component used by the substring function returns multiple values, then the substring operation is performed multiple times and results in multiple values for the component.
Attributes:
- substring_start xsd:int (required) - substring_length xsd:int (required)
Child Elements Type MinOccurs MaxOccurs oval-def:ComponentGroup n/a 1 1
The time_difference function calculates the difference in seconds between date-time values. If one component is specified, the values of that component are subtracted from the current time (UTC). If two components are specified, the value of the second component is subtracted from the value of the first component. If the component(s) contain multiple values, the operation is performed multiple times on the Cartesian product of the component(s) and the result is an array of time difference values. For example, assume a local_variable specifies the time_difference function and has two sub-components under this function: the first component returns multiple values "04/02/2009" and "04/03/2009", and the second component returns multiple values "02/02/2005" and "02/03/2005" and "02/04/2005". The local_variable element would be evaluated to have six values: (ToSeconds("04/02/2009") - ToSeconds("02/02/2005")), (ToSeconds("04/02/2009") - ToSeconds("02/03/2005")), (ToSeconds("04/02/2009") - ToSeconds("02/04/2005")), (ToSeconds("04/03/2009") - ToSeconds("02/02/2005")), (ToSeconds("04/03/2009") - ToSeconds("02/03/2005")), and (ToSeconds("04/03/2009") - ToSeconds("02/04/2005"))..
The date-time format of each component is determined by the two format attributes. The format1 attribute applies to the first component, and the format2 attribute applies to the second component. Valid values for the attributes are 'win_filetime', 'seconds_since_epoch', 'day_month_year', 'year_month_day', and 'month_day_year'. Please see the DateTimeFormatEnumeration for more information about each of these values. If an input value is not understood, the result is an error. If only one input is specified, specify the format with the format2 attribute, as the first input is considered to be the implied 'current time' input.
Note that the datatype associated with the components should be 'string' or 'int' depending on which date time format is specified. The result of this function though is always an integer.
Attributes:
- format_1 oval-def:DateTimeFormatEnumeration (optional -- default='year_month_day') - format_2 oval-def:DateTimeFormatEnumeration (optional -- default='year_month_day')
Child Elements Type MinOccurs MaxOccurs oval-def:ComponentGroup n/a 1 1
The regex_capture function captures a single substring from a string component. The 'pattern' attribute provides a regular expression that must contain a single subexpression (using parentheses). The first match of the subexpression is considered the captured substring. For example, the pattern ^abc(.*)xyz$ would capture a substring from each of the string component's values if the value starts with abc and ends with xyz. In this case the subexpression would be all the characters that exist in between the abc and the xyz. If more than one subexpression is supplied only the first match is considered. If more than one match is identified by a single subexpression only the first match is considered. If no matches are found or a subexpression is not supplied the function will evaluate to an empty string. Note that subexpressions match the longest possible substrings.
Note that when using regular expressions, OVAL supports a common subset of the regular expression character classes, operations, expressions and other lexical tokens defined within Perl 5's regular expression specification. For more information on the supported regular expression syntax in OVAL see: http://oval.mitre.org/language/about/re_support_5.6.html.
Attributes:
- pattern xsd:string
Child Elements Type MinOccurs MaxOccurs oval-def:ComponentGroup n/a 1 1
The ArithmeticEnumeration simple type defines basic arithmetic operations. Currently add and multiply are defined.
Value Description add
multiply
The ClassEnumeration simple type defines the different classes of definitions. Each class defines a certain intent regarding how an OVAL Definition is written and what that definition is describing. The specified class gives a hint about the definition so a user can know what the definition writer is trying to say. Note that the class does not make a statement about whether a true result is good or bad as this depends on the use of an OVAL Definition. These classes are also used to group definitions by the type of system state they are describing. For example, this allows users to find all the vulnerability (or patch, or inventory, etc) definitions.
Value Description compliance
A compliance definition describes the state of a machine as it complies with a specific policy. A definition of this class will evaluate to true when the system is found to be compliant with the stated policy. Another way of thinking about this is that a compliance definition is stating "the system is compliant if ...".
inventory
An inventory definition describes whether a specific piece of software is installed on the system. A definition of this class will evaluate to true when the specified software is found on the system. Another way of thinking about this is that an inventory definition is stating "the software is installed if ...".
miscellaneous
The 'miscellaneous' class is used to identify definitions that do not fall into any of the other defined classes.
patch
A patch definition details the machine state of whether a patch executable should be installed. A definition of this class will evaluate to true when the specified patch is missing from the system. Another way of thinking about this is that a patch definition is stating "the patch should be installed if ...". Note that word SHOULD is intended to mean more than just CAN the patch executable be installed. In other words, if a more recent patch is already installed then the specified patch might not need to be installed.
vulnerability
A vulnerability definition describes the conditions under which a machine is vulnerable. A definition of this class will evaluate to true when the system is found to be vulnerable with the stated issue. Another way of thinking about this is that a vulnerability definition is stating "the system is vulnerable if ...".
The DateTimeFormatEnumeration simple type defines the different date-time formats that are understood by OVAL. Note that in some cases there are a few different possabilities within a given format. Each of these possabilities is unique though and can be distinguished from each other. The different formats are used to clarify the higher level structure of the date-time string being used.
Value Description year_month_day
The year_month_day value specifies date-time strings that follow the formats: 'yyyymmdd', 'yyyymmddThhmmss', 'yyyy/mm/dd hh:mm:ss', 'yyyy/mm/dd', 'yyyy-mm-dd hh:mm:ss', or 'yyyy-mm-dd'
month_day_year
The month_day_year value specifies date-time strings that follow the formats: 'mm/dd/yyyy hh:mm:ss', 'mm/dd/yyyy', 'mm-dd-yyyy hh:mm:ss', 'mm-dd-yyyy', 'NameOfMonth, dd yyyy hh:mm:ss' or 'NameOfMonth, dd yyyy', 'AbreviatedNameOfMonth, dd yyyy hh:mm:ss', or 'AbreviatedNameOfMonth, dd yyyy'
day_month_year
The day_month_year value specifies date-time strings that follow the formats: 'dd/mm/yyyy hh:mm:ss', 'dd/mm/yyyy', 'dd-mm-yyyy hh:mm:ss', or 'dd-mm-yyyy'
win_filetime
The win_filetime value specifies date-time strings that follow the windows file time format.
seconds_since_epoch
The seconds_since_epoch value specifies date-time values that represent the time in seconds since the UNIX epoch. The Unix epoch is the time 00:00:00 UTC on January 1, 1970.
The SetOperatorEnumeration simple type defines acceptable set operations. Set operations are used to take multiple different sets of objects within OVAL and merge them into a single set. The different operators that guide this merge are defined below. For each operator, if only a single object has been supplied, then the resulting set is simply that complete object.
Value Description COMPLEMENT
The complement operator is defined in OVAL as a relative complement. The resulting set contains everything that belongs to the first declared set that is not part of the second declared set. If A and B are sets (with A being the first declared set), then the relative complement is the set of elements in A, but not in B.
INTERSECTION
The intersection of two sets in OVAL results in a set that contains everything that belongs both sets in the collection, but nothing else. If A and B are sets, then the intersection of A and B contains all the elements of A that also belong to B, but no other elements.
UNION
The union of two sets in OVAL results in a set that contains everything that belongs to either of the original sets. If A and B are sets, then the union of A and B contains all the elements of A and all elements of B, with the duplicates removed.
Below are some tables that outline how different flags are combined with a given set_operator to return a new flag. These tables are needed when computing the flag for collected objects that represent object sets in an OVAL Definition. The top row identifies the flag associated with the first set or object reference. The left column identifies the flag associated with the second set or object reference. The matrix inside the table represent the resulting flag when the given set_operator is applied. (E=error, C=complete, I=incomplete, DNE=does not exist, NC=not collected, NA=not applicable)
|| || set_operator is || obj 1 flag || union || || || E | C | I | DNE | NC | NA || -----------------||-----------------------------------|| E || E | E | E | E | E | E || obj C || E | C | I | C | I | C || 2 I || E | I | I | I | I | I || flag DNE || E | C | I | DNE | I | DNE || NC || E | I | I | I | NC | NC || NA || E | C | I | DNE | NC | NA || -----------------||-----------------------------------||
|| || set_operator is || obj 1 flag || intersection || || || E | C | I | DNE | NC | NA || -----------------||-----------------------------------|| E || E | E | E | DNE | E | E || obj C || E | C | I | DNE | NC | C || 2 I || E | I | I | DNE | NC | I || flag DNE || DNE | DNE | DNE | DNE | DNE | DNE || NC || E | NC | NC | DNE | NC | NC || NA || E | C | I | DNE | NC | NA || -----------------||-----------------------------------||
|| || set_operator is || obj 1 flag || complement || || || E | C | I | DNE | NC | NA || -----------------||-----------------------------------|| E || E | E | E | DNE | E | E || obj C || E | C | I | DNE | NC | E || 2 I || E | E | E | DNE | NC | E || flag DNE || E | C | I | DNE | NC | E || NC || E | NC | NC | DNE | NC | E || NA || E | E | E | E | E | E || -----------------||-----------------------------------||
The EntityBaseType complex type is an abstract type that defines the default attributes associated with every entity. Entities can be found in both OVAL Objects and OVAL States and represent the individual properties associated with items found on a system. An example of a single entity would be the path of a file. Another example would be the version of the file.
The optional datatype attribute specifies how the given operation should be applied to the data. Since we are dealing with XML everything is technically a string, but often the entity value is meant to represent some other datatype and this affects the way an operation is performed. An example is with the statement 'is 123 less than 98'. If the data is treated as integers the answer is no, but if the data is treated as strings, then the answer is yes. Specifying a datatype defines how the less than operation should be performed. Another way of thinking of things is that the datatype attribute specifies how the data should be cast before performing the operation (note that the default datatype is 'string'). In the previous example, if the datatype is set to int, then '123' and '98' should be cast as integers. Another example is applying the 'equal' operation to '1.0.0.0' and '1.0'. With datatype 'string' they are not equal, with datatype 'version' they are. Note that there are certain cases where a cast from one datatype to another is not possible. If a cast cannot be made, (trying to cast 'abc' to an integer) then an error should be reported. For example, if the datatype is set to 'integer' and the value of the entity is empty. There is no way to cast the empty string (or NULL) to an integer, and in cases like this an error should be reported.
The optional operation determines how the individual entities should be evaluated. (the default operator is 'equals') Both of these attributes are optional in order to keep the XML clean and readable. The default values are used most of the time and putting datatype="string" and operator="equals" for each element would muddy up the XML.
The optional mask attribute can be used in situations where information is needed for evaluation, but this information should not be disclosed in the results file. (maybe due to sensitivity concerns) If the mask attribute is set to 'true', then the value of this field, along with the operation used, should not appear in the results file. Note that this value would appear in the copy of the system characteristics contained in the results file. In this case the results file should make use of the corresponding mask attribute in the system characteristics schema should be set to true and the value should be omitted. In addition to the value being omitted from the copy of the system characteristics file, the copy of the definition file should also omit the value and operation used for testing.
The optional var_ref attribute refers the value of the entity to a variable element. When supplied, the value(s) associated with the OVAL Variable should be used as the value(s) of the entity. If there is an error computing the value of the variable, then that error should be passed up to the entity referencing it. If the variable being referenced does not have a value (for example, if the variable pertains to the size of a file, but the file does not exist) then one of two results are possible. If the entity is part of an object declaration, then the object is considered to not exist. If the entity is part of a state declaration, then the state comparison should result in an error.
Attributes:
- datatype oval:DatatypeEnumeration (optional -- default='string') - operation oval:OperationEnumeration (optional -- default='equals') - mask xsd:boolean (optional -- default='false') - var_ref oval:VariableIDPattern (optional)
Simple Content xsd:anySimpleType
The EntityObjectBaseType complex type is an abstract type that extends the EntityBaseType and is used by the entities within an OVAL Objects.
If the entity uses a var_ref and the associated variable defines more than one value, the optional var_check attribute defines how the data collection should proceed. For example, if an object entity 'filename' with an operation of 'does not equal' references a variable that returns five different values, and the var_check attribute has a value of 'all', then an actual file on the system matches only if the actual filename does not equal any of the variable values. If a variable does not return any value, then an error should be reported during OVAL analysis.
Attributes:
- var_check oval:CheckEnumeration (optional -- default='all')
Simple Content oval-def:EntityBaseType
The EntityObjectAnyType type is extended by the entities of an individual OVAL Object. This type provides uniformity to each object entity by including the attributes found in the EntityObjectBaseType. This specific type describes any simple data.
Attributes:
Simple Content oval-def:EntityObjectBaseType
The EntityBinaryType type is extended by the entities of an individual OVAL Object. This type provides uniformity to each object entity by including the attributes found in the EntityObjectBaseType. This specific type describes simple binary data. The empty string is also allowed when using a variable reference with an element.
The EntityBoolType type is extended by the entities of an individual OVAL Object. This type provides uniformity to each object entity by including the attributes found in the EntityObjectBaseType. This specific type describes simple boolean data. The empty string is also allowed when using a variable reference with an element.
The EntityObjectFloatType type is extended by the entities of an individual OVAL Object. This type provides uniformity to each object entity by including the attributes found in the EntityObjectBaseType. This specific type describes simple float data. The empty string is also allowed when using a variable reference with an element.
The EntityIntType type is extended by the entities of an individual OVAL Object. This type provides uniformity to each object entity by including the attributes found in the EntityObjectBaseType. This specific type describes simple integer data. The empty string is also allowed when using a variable reference with an element.
The EntityStringType type is extended by the entities of an individual OVAL Object. This type provides uniformity to each object entity by including the attributes found in the EntityObjectBaseType. This specific type describes simple string data.
The EntityStateBaseType complex type is an abstract type that extends the EntityBaseType and is used by the entities within an OVAL State.
The optional entity_check attribute specifies how to handle multiple item entities with the same name in the OVAL Systems Characteristics file. For example, suppose we are dealing with a Group Test and an entity in the state is related to the user. It is very likely that when information about the group is collected off the system (and represented in the OVAL System Characteristics file) that there will be multiple users associated with the group, i.e. multiple ‘user’ item entities associated with the same ‘user’ state entity. If the OVAL State defines the value of the user entity to equal ‘Fred', then the entity_check attribute determines if all values for ‘user’ item entities must be equal to ‘Fred’, or at least one value must be equal to ‘Fred’, etc. Note that with the exception of the ‘none_satisfy’ check value, the entity_check attribute can only affect the result of the test if the corresponding OVAL Item allows more than one occurrence of the entity (e.g. ‘maxOccurs’ is some value greater than one).
If the state entity uses a var_ref attribute, and the associated variable defines more than one value, the optional var_check attribute defines how the evaluation should proceed. For example, if a state entity 'size' with an operation of 'less than' references a variable that has five different integer values, and the var_check attribute has a value of 'all', then the 'size' state entity evaluates to true only if the corresponding ‘size’ item entity is less than each of the five integers defined by the variable. If a variable does not have any value, then an error should be reported during OVAL analysis. If both the state entity and a corresponding item entity have multiple values, the var_check is applied to each value of the item entity individually, and all must evaluate to true for the state entity to evaluate to true. There is no value of var_check which enables an element-wise comparison, and so there is no way to determine whether two multi-valued entities are truly 'equal' in that sense.
The entity_check and var_check attributes are considered together when evaluating a single state entity. When a variable identifies more than one value and multiple item entities with the same name exist for a single state entity, a many-to-many comparison must be conducted. In this situation, there are many values for the state entity that must be compared to many item entities. Each item entity is compared to the state entity. For each item entity, an interim result is calculated by using the var_check attribute to combine the result of comparing each variable value with a single system value. Then these interim results are combined for each system value using the entity_check attribute.
Attributes:
- entity_check oval:CheckEnumeration (optional -- default='all') - var_check oval:CheckEnumeration (optional -- default='all')
Simple Content oval-def:EntityBaseType
The EntityStateAnyType type is extended by the entities of an individual OVAL State. This type provides uniformity to each state entity by including the attributes found in the EntityStateBaseType. This specific type describes any simple data.
Attributes:
Simple Content oval-def:EntityStateBaseType
The EntityStateBinaryType type is extended by the entities of an individual OVAL State. This type provides uniformity to each state entity by including the attributes found in the EntityStateBaseType. This specific type describes simple binary data. The empty string is also allowed when using a variable reference with an element.
The EntityStateBoolType type is extended by the entities of an individual OVAL State. This type provides uniformity to each state entity by including the attributes found in the EntityStateBaseType. This specific type describes simple boolean data. The empty string is also allowed when using a variable reference with an element.
The EntityStateFloatType type is extended by the entities of an individual OVAL State. This type provides uniformity to each state entity by including the attributes found in the EntityStateBaseType. This specific type describes simple float data. The empty string is also allowed when using a variable reference with an element.
The EntityStateIntType type is extended by the entities of an individual OVAL State. This type provides uniformity to each state entity by including the attributes found in the EntityStateBaseType. This specific type describes simple integer data. The empty string is also allowed when using a variable reference with an element.
The EntityStateStringType type is extended by the entities of an individual OVAL State. This type provides uniformity to each state entity by including the attributes found in the EntityStateBaseType. This specific type describes simple string data.