Updated: 11 December 1998

OpenVMS System Services Reference Manual

Removes all scheduled wakeup requests for a process from the timer queue, including those made by the caller or by other processes. The Schedule Wakeup ($SCHDWK) service makes scheduled wakeup requests.

Format

SYS$CANWAK [pidadr] ,[prcnam]

C Prototype

int sys$canwak (unsigned int *pidadr, void *prcnam);

Arguments

pidadr

OpenVMS usage:	process_id
type:	longword (unsigned)
access:	modify
mechanism:	by reference

Process identification (PID) of the process for which wakeups are to be canceled. The pidadr argument is the address of a longword specifying the PID. The pidadr argument can refer to a process running on the local node or a process running on another node in the OpenVMS Cluster system.

prcnam

OpenVMS usage:	process_name
type:	character-coded text string
access:	read only
mechanism:	by descriptor--fixed-length string descriptor

Name of the process for which wakeups are to be canceled. The prcnam argument is the address of a character string descriptor pointing to the process name string.

A process running on the local node can be identified with a 1- to 15-character string. To identify a process on a specific node in a cluster, specify the full process name, which includes the node name as well as the process name. The full process name can contain up to 23 characters.

The operating system interprets the UIC group number of the calling process as part of the process name; the names of processes are unique to UIC groups. Because of this, you can use the prcnam argument only on behalf of processes in the same group as the calling process.

Description

The Cancel Wakeup service removes from the timer queue all scheduled wakeup requests for a process, including those made by the caller or by other processes. The Schedule Wakeup ($SCHDWK) service makes scheduled wakeup requests.

If the longword at address pidadr is 0, the PID of the target process is returned.

If you specify neither the pidadr nor the prcnam argument, scheduled wakeup requests for the calling process are canceled.

Pending wakeup requests issued by the current image are automatically canceled at image exit.

This service cancels only wakeup requests that have been scheduled; it does not cancel wakeup requests made with the Wake Process from Hibernation ($WAKE) service.

Required Access or Privileges

Depending on the operation, the calling process might need one of the listed privileges to use $CANWAK:

• You need GROUP privilege to cancel wakeups for processes in the same group that do not have the same UIC.
• You need WORLD privilege to cancel wakeups for any process in the system.

Required Quota

Canceled wakeup requests are restored to the process's AST limit (ASTLM) quota.

Related Services

$ASCTIM, $BINTIM, $CANTIM, $GETTIM, $NUMTIM, $SCHDWK, $SETIME, $SETIMR

Condition Values Returned

SS$_NORMAL	The service completed successfully.
SS$_ACCVIO	The process name string or string descriptor cannot be read by the caller, or the process identification cannot be written by the caller.
SS$_INCOMPAT	The remote node is running an incompatible version of the operating system.
SS$_IVLOGNAM	The process name string has a length of 0 or has more than 15 characters.
SS$_NONEXPR	The specified process does not exist, or you specified an invalid process identification.
SS$_NOPRIV	The process does not have the privilege to cancel wakeups for the specified process.
SS$_NOSUCHNODE	The process name refers to a node that is not currently recognized as part of the cluster.
SS$_REMRSRC	The remote node has insufficient resources to respond to the request. (Bring this error to the attention of your system manager.)
SS$_UNREACHABLE	The remote node is a member of the cluster but is not accepting requests. (This is normal for a brief period early in the system boot process.)

Determines on behalf of a third-party user whether a named user can access the object specified.

Format

SYS$CHECK_ACCESS [objtyp], [objnam], [usrnam], itmlst, [contxt], [clsnam], [objpro], [usrpro]

C Prototype

int sys$check_access (unsigned int *objtyp, void *objnam, void *usrnam, void *itmlst, unsigned int *contxt, void *clsnam, void *objpro, void *usrpro);

Arguments

objtyp

OpenVMS usage:	longword_unsigned
type:	longword (unsigned)
access:	read only
mechanism:	by reference

Type of object being accessed. The objtyp argument is the address of a longword containing a value specifying the type of object. The appropriate symbols are listed in the following table and are defined in the system macro $ACLDEF library.

Symbol	Meaning
ACL$C_CAPABILITY	Object is a restricted resource; use the reserved name VECTOR.
ACL$C_DEVICE	Object is a device.
ACL$C_FILE	Object is a Files-11 On-Disk Structure Level 2 file.
ACL$C_GROUP_GLOBAL_SECTION	Object is a group global section.
ACL$C_JOBCTL_QUEUE	Object is a batch, print, or server queue.
ACL$C_LOGICAL_NAME_TABLE	Object is a logical name table.
ACL$C_SYSTEM_GLOBAL_SECTION	Object is a system global section.

For further information about these symbols, see the description of the clsnam argument.

objnam

OpenVMS usage:	char_string
type:	character-coded text string
access:	read only
mechanism:	by descriptor--fixed-length string descriptor

Name of the object being accessed. The objnam argument is the address of a character-string descriptor pointing to the object name.

usrnam

OpenVMS usage:	char_string
type:	character-coded text string
access:	read only
mechanism:	by descriptor--fixed-length string descriptor

Name of the user attempting access. The usrnam argument is the address of a descriptor that points to a character string that contains the name of the user attempting to gain access to the specified object. The user name string can contain a maximum of 12 alphanumeric characters.

itmlst

OpenVMS usage:	item_list_3
type:	longword (unsigned)
access:	read only
mechanism:	by reference

Attributes describing how the object is to be accessed and information returned after $CHECK_ACCESS performs the protection check (for instance, security alarm information).

For each item code, you must include a set of four elements and end the list with a longword containing the value 0 (CHP$_END), as shown in the following diagram.

The following table defines the item descriptor fields.

Descriptor Field	Definition
Buffer length	A word containing a user-supplied integer specifying the length (in bytes) of the associated buffer. The length of the buffer needed depends on the item code specified in the item code field of the item descriptor. If the value of buffer length is too small, the service truncates the data.
Item code	A word containing a user-supplied symbolic code specifying the item of information in the associated buffer.
Buffer address	A longword containing the user-supplied address of the buffer.
Return length address	A longword containing the address of a word in which $CHECK_ACCESS writes the number of bytes written to the buffer pointed to by bufadr. If the buffer pointed to by bufadr is used to pass information to $CHECK_ACCESS, retlenadr is ignored but must be included.

contxt

Using the contxt argument keeps the UAF open across all calls, thereby improving the performance of the system on subsequent calls. To close the UAF, you must run down the image.

The resulting contxt value from a $CHECK_ACCESS call can also be used as the input contxt argument to the $GETUAI system service, and vice versa.

clsnam

objpro

Buffer containing an object security profile or object handle. The objpro argument is the address of a descriptor pointing to a buffer that contains an encoded object security profile or the address of a descriptor pointing to an object handle.

Object handles vary according to the associated security object class. Currently, the only supported object handles are for the file and device class objects where the object handle is a word or longword channel.

The objpro and objnam arguments are mutually exclusive unless the objpro argument is a simple object handle. The objpro and usrpro arguments are also mutually exclusive unless the objpro argument is an object handle.

usrpro

The $CREATE_USER_PROFILE service can be used to construct a user security profile. The usrpro and usrnam arguments are mutually exclusive. The objpro and usrpro arguments are also mutually exclusive unless the objpro argument is an object handle.

The item codes used with $CHECK_ACCESS are described in the following list and are defined in the $CHPDEF system macro library.

Item Codes

CHP$_ACCESS

A longword bit mask that represents the desired access ($ARMDEF). Only those bits set in CHP$_ACCESS are checked against the protection of the object to determine whether access is granted.

The default for CHP$_ACCESS is read. Symbolic representations for the access types associated with the built-in protected classes are found in the $ARMDEF macro.

For example, ARM$M_MANAGE specifies Manage access for the queue class object. Access type names are object class specific and vary from class to class. Because $CHECK_ACCESS performs only a bitwise comparison of access desired to object protection, the original Read, Write, Execute, and Delete names can also be used to specify the first four access types for any object class.

The following table shows the access types available and lists their common interpretations. These symbols are defined in the $ARMDEF system macro library. For more information, see the OpenVMS Guide to System Security.

Access Type	Access Permitted
ARM$M_READ	Allows holders to read an object, perform wildcard directory lookups, display jobs in a queue, or use an associated vector processor.
ARM$M_WRITE	Allows holders to alter the contents of an object, remove a directory entry, write or extend existing files on a volume, or submit a job to a queue.
ARM$M_EXECUTE	Allows holders to run an image or command procedure, perform exact directory lookups, issue physical I/O requests to a device, create new files on a volume, or act as operator for a queue.
ARM$M_DELETE	Allows holders to delete an object, perform logical I/O to a device, or delete a job in a queue.
ARM$M_CONTROL	Allows holders to display or alter the security characteristics of an object.

CHP$_ACMODE

A byte that defines the accessor's processor access mode ($PSLDEF). The following access modes and their symbols are defined in the system macro library ($PSLDEF). Objects supported by the operating system do not consider access mode in determining object access.

Symbol	Access Mode
PSL$C_USER	User
PSL$C_SUPER	Supervisor
PSL$C_EXEC	Executive
PSL$C_KERNEL	Kernel

If CHP$_ACMODE is not specified, access mode is not used to determine access.

CHP$_ALARMNAME

Address of a buffer to receive the alarm name from any Alarm ACE contained in the object's ACL. Currently, if a matching Alarm ACE exists, the string SECURITY will be returned. The string returned by CHP$_ALARMNAME can be used as input to the $AUDIT_EVENT system service, using the NSA$_ALARM_NAME item code.

CHP$_AUDIT_LIST

A list containing information to be added to any resulting security audit. The bufadr argument points to the beginning of an $AUDIT_EVENT item list. See the itmlst argument of the $AUDIT_EVENT system service for a list of valid security auditing item codes. Note that the NSA$_EVENT_TYPE and NSA$_EVENT_SUBTYPE items are ignored when auditing with $CHECK_ACCESS. The CHP$V_AUDIT flag must be specified.

CHP$_AUDITNAME

Address of a buffer to receive the audit name from any Audit ACE contained in the object's ACL. Currently, if a matching Audit ACE exists, the string SECURITY will be returned. The string returned by CHP$_AUDITNAME can be used as input to the $AUDIT_EVENT system service, using the NSA$_AUDIT_NAME item code.

CHP$_FLAG

A longword that controls various aspects of the protection check. The symbols in the following table are offsets to the bits within the longword. You can also obtain the values as masks with the appropriate bit set by using the prefix CHP$M rather than CHP$V. These symbols are defined in the system macro library ($CHPDEF).

Symbol	Access
CHP$V_ALTER	Accessor desires write access to object.
CHP$V_AUDIT	Access audit requested.
CHP$V_CREATE	Perform the audit as an object creation event.
CHP$V_DELETE	Perform the audit as an object deletion event.
CHP$V_FLUSH	Force audit buffer flush.
CHP$V_INTERNAL	Audit on behalf of the Trusted Computing Base (TCB). Reserved to Compaq.
CHP$V_MANDATORY	Force the object access event to be audited.
CHP$V_NOFAILAUD	Do not perform audits for failed access.
CHP$V_NOSUCCAUD	Do not perform audits for successful access.
CHP$V_OBSERVE	Accessor desires read access to object.
CHP$V_SERVER	Audit on behalf of a TCB server process.
CHP$V_USEREADALL	Accessor is eligible for READALL privilege.

The default for CHP$_FLAG is CHP$V_OBSERVE.

The primary purpose of the CHP$V_OBSERVE and CHP$V_ALTER flags is as latent support for a mandatory (lattice) security policy, such as that provided by the Security Enhanced VMS (SEVMS) offering.

CHP$_MATCHEDACE

A variable-length data structure containing the first Identifier ACE in the ACL that granted or denied access to the object. The $FORMAT_ACL system service describes the format of an Identifier ACE.

CHP$_PRIVUSED

A longword mask of flags that represent the privileges used to gain access.

You can also obtain the values as masks with the appropriate bit set by using the prefix CHP$M rather than CHP$V. The symbols are defined in the system macro library ($CHPDEF). The following symbols are offsets to the bits within the longword.

Symbol	Meaning
CHP$V_SYSPRV	SYSPRV was used to gain the requested access.
CHP$V_GRPPRV	GRPPRV was used to gain the requested access.
CHP$V_BYPASS	BYPASS was used to gain the requested access.
CHP$V_READALL	READALL was used to gain the requested access.
CHP$V_OPER	OPER was used to gain the requested access.
CHP$V_GRPNAM	GRPNAM was used to gain the requested access.
CHP$V_SYSNAM	SYSNAM was used to gain the requested access.
CHP$V_GROUP	GROUP was used to gain the requested access.
CHP$V_WORLD	WORLD was used to gain the requested access.
CHP$V_PRMCEB	PRMCEB was used to gain the requested access.
CHP$V_UPGRADE	UPGRADE was used to gain the requested access.
CHP$V_DOWNGRADE	DOWNGRADE was used to gain the requested access.

Description

The Check Access service invokes the operating system control protection check mechanism, $CHKPRO, to determine whether a named user is allowed the described access to the named object. A file server, for example, might check the access attributes of a user who attempts to access a file (the object).

If the user can access the object, $CHECK_ACCESS returns the SS$_NORMAL status code; otherwise, $CHECK_ACCESS returns SS$_NOPRIV.

The arguments accepted by this service specify the name and class of object being accessed, the name of the user requesting access to the object, the type of access desired, and the type of information to be returned.

The caller can also request that an object access audit be performed if security auditing has been enabled for the object class or if Audit ACEs are contained in the object's ACL. Auditing ACEs include both Alarm ACEs and Audit ACEs. The CHP$V_AUDIT flag requests an access audit. This requires that the caller be in executive or kernel mode or possess the AUDIT privilege.

Normally, $CHECK_ACCESS generates an object access audit when an audit is required. The caller can specify the CHP$V_CREATE flag to force an object creation audit instead of an object access audit. Similarly, the CHP$V_DELETE flag forces an object deletion audit. The CHP$_AUDIT_LIST item code can be used to specify additional information to be included in any resulting audit records.

With certain types of devices, $CHECK_ACCESS can return a false negative, but never a false positive. This is due to additional LOG_IO and PHY_IO privilege checking in the $QIO system service that might override an otherwise unsuccessful access attempt. These privilege checks are not mirrored by the $CHECK_ACCESS system service. The affected devices are those that are non-file-structured or mounted foreign and also either spooled, file-oriented, or shareable. For example, mailbox devices fall into this category because they are non-file-structured and shareable. To accurately duplicate the result that would be obtained if the user had issued a read or write against these devices, it might be necessary to test for these additional privileges using the $CHECK_PRIVILEGE system service. See the OpenVMS I/O User's Reference Manual for further information on access requirements for devices.

Required Access or Privileges

Access to SYSUAF.DAT and RIGHTSLIST.DAT is required. AUDIT privilege is required when requesting a user mode audit.

Required Quota

None

Related Services

$CHKPRO, $CREATE_USER_PROFILE, $FORMAT_ACL

Condition Values Returned

SS$_NORMAL	The service completed successfully; the desired access is granted.
SS$_ACCVIO	The item list cannot be read by the caller, one of the buffers specified in the item list cannot be written by the caller, or one of the arguments could not be read or written.
SS$_BADPARAM	Invalid or conflicting combination of parameters.
SS$_INSFARG	Insufficient information to identify object or user.
SS$_INSFMEM	Insufficient process memory to execute service.
SS$_NOAUDIT	Caller lacks privilege to request audit.
SS$_NOCALLPRIV	Caller lacks privilege to access authorization database.
SS$_NOCLASS	No matching object class was located.
SS$_NOPRIV	The desired access is not granted.
SS$_UNSUPPORTED	Operations on remote object are not supported.

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