Maintaining File Security

• Modes of access (for example, reading, writing, or saving).

• Types of user (for example, a user with Account Librarian capability, Group Librarian capability, or a user to whom the access modes specified are permitted.)

When a program opens or creates a file, it can define the way the file can be accessed by specifying a particular access mode for the file (for example, read-only, write-only, update, and so on). These specifications apply to files on any device, and only the creator of file can change or override them.

When specifying the access mode for a file, it is important to know the location of the current end-of-file before and after the file is opened and the location of the logical record pointer that indicates where the next operation will begin. For example, the choice of the correct access mode can write a record to a file and:

For detailed information on this topic, refer to Accessing Files Programmer's Guide (32650-90017).

Table 6-8 “File Access Mode Types” describes the file access mode types.

Restrictions on accessing a file are established when the file is created according to the default established for the group and account where the file resides.

The capabilities of a user who accesses a file can determine the security restrictions applied. Table 6-9 “User Type Definitions” describes the types of users recognized by the MPE/iX Security System, their mnemonic codes, and definitions.

For detailed information on this topic, refer to Accessing Files Programmer's Guide (32650-90017).

The user access modes to a file are determined by four separate levels of security settings. All four levels are checked and must be passed to grant a user access to a file. The only two levels over which a standard user has control are the file and lockword levels. However, it is important for a standard user to understand all levels of the security system, since the combination of all the settings determines the user's access to the file. Figure 6-16 “Security Level for File Access” shows the security levels checked when a user attempts to gain access to a file.

Figure 6-16 Security Level for File Access

The default security at account, group, and file levels are as follows:

At the group level, the MPE/iX Security System recognizes six access modes:

It recognizes seven user types:

For detailed information on this topic, refer to Accessing Files Programmer's Guide (32650-90017).

When a file is created, the security provisions that apply to it are the default provisions assigned by MPE/iX at the file level, coupled with the user-specified or default provisions assigned to the account and group to which the file belongs. At any time, however, the creator of the file can change the file level security provisions. Thus, the total security provisions for a file depend on specifications made at three levels: account, group, and file. A user must pass tests at the account, group, and file levels (in order) to successfully access a file in the requested mode.

If no security provisions are explicitly specified by the user, the following provisions are assigned at the file level by default:

Because the total security for a file always depends on security at all three levels, a file not explicitly protected from a certain access mode at the file level may benefit from the default protection at the group level. For detailed information on this topic, refer to Accessing Files Programmer's Guide (32650-90017).

Similar to the MPE File Access System, ACDs use modes to specify the types of access to grant or refuse to users as follows:

ACDs are defined in a similar manner as file access modes. For example:

   ACD = (R,W:MGR.ACCTING, DENNIS.LEE; R:@.PAYROLL; A:@.@

MGR.ACCTING and DENNIS.LEE can read and write to the file associated with this example ACD. Any user in PAYROLL can read it, and any user on the system can append to it. If a user is not given a permission, the user does not have it.

Use commands to manage ACDs interactively through the command interpreter. Use intrinsics to manage ACDs in a program.

	NOTE: Device ACDs shold not be migrated because they are tied to their system's configuration.

Move file ACDs between MPE V and MPE/iX by using the STORE and RESTORE commands, where COPYACD is the default.

	NOTE: You must have authorization to use the COPYACD parameter of the STORE and RESTORE commands. If you are not an owner of the file and do not have RACD permission, you will get an error.

The security provisions for the account and group levels are managed only by users with System Manager or Account Manager capabilities, respectively. However, you can change the security provisions for any disc file you have created by using the :ALTSEC command. This does not affect any account-level or group-level provisions that may cover the file, and it does not affect the security provided by a lockword. For detailed information on this topic, refer to Accessing Files Programmer's Guide (32650-90017).

You can temporarily suspend the security restrictions on any disc file you create by using the :RELEASE command. This allows any user to access the file in any mode, thus providing unlimited access to the file. It does not remove lockword protection, and it does not modify the file security settings recorded in the system. It merely bypasses them temporarily. :RELEASE remains in effect for a file until you enter the :SECURE command in this or a later job or session or until the file is modified.

For detailed information on this topic, refer to Accessing Files Programmer's Guide (32650-90017).