Ambient authority

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-	If a [[subject]] can [[operation on object|operate]] on all [[object]]s of a given type, we say that it has '''ambient authority'''.	+	The correct interpretation of this page relies on proper interpretation of words: [[subject, object, operation and permission]].
-	Several access control models were invented and implemented to enable restriction of ambient authority (to access all objects of a given type) of subjects. Many of them are:	+	== Definition ==
-	* either weak (we cannot follow the [[POLA|principle of least authority]])	+
-	* or convoluted (it is hard to learn how to work with this model and be sure about achieved security level).	+
-	Things become more "interesting" if we have to consider different security policies enforced via different alternative security mechanisms for the same type of objects and for different type of objects and the relevant transitivity relationship.	+
-	= Examples of ambient authority =	+	IF a subject requests an action, typically by naming an object and an operation on that object, and the action is allowed because the subject has a permission that would allow the action, THEN we say that the subject has '''ambient authority'''.
-	If we consider files owned by some UNIX user as [[object]]s and UNIX processes as [[subject]]s then all processes have ''ambient authority'' to manipulate all those files.	+	== Notes concerning the definition ==
-	If we consider TCP ports 1024--65535 as [[object]]s and and UNIX processes as [[subject]]s then all processes have ''ambient authority'' to listen to any ports.	+	Instead of "naming" an object, capability community often uses the term "designation" of an object.
-	If we consider all executable programs owned by some UNIX user as [[object]]s and all UNIX processes as run by the same user as [[subject]]s then all these processes have ''ambient authority'' to run any of those programs.	+	Whether we can say that some chosen subject has '''ambient authority''' or not is solely determined by the fact HOW are operations allowed or denied. It is independent from the fact WHAT PERMISSIONS a given subject actually has. This matters in case of a term [[excess authority]].
-	If we consider all functions defined in some C program as [[subject]]s and all functions in the same C program as [[object]]s then any function has ''ambient authority'' to call any other function (in C we can cast any integer to a function pointer and perform the call operation with this forged reference to a function).	+	The difference between [[ambient authority system]] and the [[designated authority system]] is that:
		+	* in the first case subjects, when they request some operation with some object, '''do not have to''' specify the permission that allows given operation with given object;
		+	* in the latter case subject, when they request some operation with some object, '''have to''' specify the permission this request with designated the permission that allows given operation with given object.
-	If we consider all functions defined in some C program as [[subject]]s and all regions of the address space of the relevant process as [[object]]s then all these functions have ''ambient authority'' to read from or write to any such memory region.	+	== See also ==
		+
		+	* [[Excess authority]]
		+	* [[Ambient authority system]]
		+
		+	== Examples of ambient authority ==
		+
		+	All UNIX processes run with some effective user id have ambient authority to manipulate all files accessible by that user id.
		+
		+	All UNIX processes have ''ambient authority'' to listen to TCP or UDP ports 1024--65535.
		+
		+	All UNIX processes have ''ambient authority'' to send any signal to any other UNIX process.
		+
		+	== Acknowledgement ==
		+
		+	The term ''ambient authority'' was coined by Dean Tribble and Mark S. Miller.

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Latest revision as of 23:43, 2 January 2011

The correct interpretation of this page relies on proper interpretation of words: subject, object, operation and permission.

Contents 1 Definition 2 Notes concerning the definition 3 See also 4 Examples of ambient authority 5 Acknowledgement

Definition

IF a subject requests an action, typically by naming an object and an operation on that object, and the action is allowed because the subject has a permission that would allow the action, THEN we say that the subject has ambient authority.

Notes concerning the definition

Instead of "naming" an object, capability community often uses the term "designation" of an object.

Whether we can say that some chosen subject has ambient authority or not is solely determined by the fact HOW are operations allowed or denied. It is independent from the fact WHAT PERMISSIONS a given subject actually has. This matters in case of a term excess authority.

The difference between ambient authority system and the designated authority system is that:

• in the first case subjects, when they request some operation with some object, do not have to specify the permission that allows given operation with given object;
• in the latter case subject, when they request some operation with some object, have to specify the permission this request with designated the permission that allows given operation with given object.

See also

• Excess authority
• Ambient authority system

Examples of ambient authority

All UNIX processes run with some effective user id have ambient authority to manipulate all files accessible by that user id.

All UNIX processes have ambient authority to listen to TCP or UDP ports 1024--65535.

All UNIX processes have ambient authority to send any signal to any other UNIX process.

Acknowledgement

The term ambient authority was coined by Dean Tribble and Mark S. Miller.