Class ACE
- java.lang.Object
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- jcifs.internal.dtyp.ACE
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public class ACE extends Object implements ACE, Decodable
An Access Control Entry (ACE) is an element in a security descriptor such as those associated with files and directories. The Windows OS determines which users have the necessary permissions to access objects based on these entries.To fully understand the information exposed by this class a description of the access check algorithm used by Windows is required. The following is a basic description of the algorithm. For a more complete description we recommend reading the section on Access Control in Keith Brown's "The .NET Developer's Guide to Windows Security" (which is also available online).
Direct ACEs are evaluated first in order. The SID of the user performing the operation and the desired access bits are compared to the SID and access mask of each ACE. If the SID matches, the allow/deny flags and access mask are considered. If the ACE is a "deny" ACE and any of the desired access bits match bits in the access mask of the ACE, the whole access check fails. If the ACE is an "allow" ACE and all of the bits in the desired access bits match bits in the access mask of the ACE, the access check is successful. Otherwise, more ACEs are evaluated until all desired access bits (combined) are "allowed". If all of the desired access bits are not "allowed" the then same process is repeated for inherited ACEs.
For example, if user WNET\alice tries to open a file with desired access bits 0x00000003 (FILE_READ_DATA | FILE_WRITE_DATA) and the target file has the following security descriptor ACEs:
Allow WNET\alice 0x001200A9 Direct Allow Administrators 0x001F01FF Inherited Allow SYSTEM 0x001F01FF Inherited
the access check would fail because the direct ACE has an access mask of 0x001200A9 which doesn't have the FILE_WRITE_DATA bit on (bit 0x00000002). Actually, this isn't quite correct. If WNET\alice is in the local Administrators group the access check will succeed because the inherited ACE allows local Administrators both FILE_READ_DATA and FILE_WRITE_DATA access.
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Field Summary
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Fields inherited from interface jcifs.ACE
DELETE, FILE_APPEND_DATA, FILE_DELETE, FILE_EXECUTE, FILE_READ_ATTRIBUTES, FILE_READ_DATA, FILE_READ_EA, FILE_WRITE_ATTRIBUTES, FILE_WRITE_DATA, FILE_WRITE_EA, FLAGS_CONTAINER_INHERIT, FLAGS_INHERIT_ONLY, FLAGS_INHERITED, FLAGS_NO_PROPAGATE, FLAGS_OBJECT_INHERIT, GENERIC_ALL, GENERIC_EXECUTE, GENERIC_READ, GENERIC_WRITE, READ_CONTROL, SYNCHRONIZE, WRITE_DAC, WRITE_OWNER
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Constructor Summary
Constructors Constructor Description ACE()
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Method Summary
All Methods Instance Methods Concrete Methods Modifier and Type Method Description int
decode(byte[] buf, int bi, int len)
int
getAccessMask()
Returns the access mask associated with this ACE.String
getApplyToText()
Returns the 'Apply To' text for inheritance of ACEs on directories such as 'This folder, subfolder and files'.int
getFlags()
Returns the flags for this ACE.SID
getSID()
Return the SID associated with this ACE.boolean
isAllow()
Returns true if this ACE is an allow ACE and false if it is a deny ACE.boolean
isInherited()
Returns true if this ACE is an inherited ACE and false if it is a direct ACE.String
toString()
Return a string represeting this ACE.
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Method Detail
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isAllow
public boolean isAllow()
Description copied from interface:ACE
Returns true if this ACE is an allow ACE and false if it is a deny ACE.
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isInherited
public boolean isInherited()
Description copied from interface:ACE
Returns true if this ACE is an inherited ACE and false if it is a direct ACE.Note: For reasons not fully understood, FLAGS_INHERITED may not be set within all security descriptors even though the ACE was in face inherited. If an inherited ACE is added to a parent the Windows ACL editor will rebuild all children ACEs and set this flag accordingly.
- Specified by:
isInherited
in interfaceACE
- Returns:
- whether this is an inherited ACE
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getFlags
public int getFlags()
Description copied from interface:ACE
Returns the flags for this ACE. The isInherited() method checks the FLAGS_INHERITED bit in these flags.
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getApplyToText
public String getApplyToText()
Description copied from interface:ACE
Returns the 'Apply To' text for inheritance of ACEs on directories such as 'This folder, subfolder and files'. For files the text is always 'This object only'.- Specified by:
getApplyToText
in interfaceACE
- Returns:
- descriptive text for the ACE scope
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getAccessMask
public int getAccessMask()
Description copied from interface:ACE
Returns the access mask associated with this ACE. Use the constants for FILE_READ_DATA, FILE_WRITE_DATA, READ_CONTROL, GENERIC_ALL, etc with bitwise operators to determine which bits of the mask are on or off.- Specified by:
getAccessMask
in interfaceACE
- Returns:
- the access mask
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getSID
public SID getSID()
Description copied from interface:ACE
Return the SID associated with this ACE.
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decode
public int decode(byte[] buf, int bi, int len)
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