permissions(F) 06 January 1993 permissions(F) Name permissions - format of UUCP Permissions file Description The Permissions file (/usr/lib/uucp/Permissions) specifies the permis- sions for remote computers concerning login, file access, and command execution. In the Permissions file, you can specify the commands that a remote computer can execute and restrict its ability to request or receive files queued by the local site. Each entry is a logical line with physical lines terminated by a \ to indicate continuation. Entries are made up of options delimited by white space. Each option is a name-value pair in the following format: name=value Note that no white space is allowed within an option assignment. Comment lines begin with a hash sign (#) and they occupy the entire line up to a newline character. Blank lines are ignored (even within multi- line entries). There are two types of Permissions file entries: LOGNAME specifies the permissions that take effect when a remote computer calls your computer. MACHINE specifies permissions that take effect when your computer calls a remote computer. Options This section describes each option, specifies how they are used, and lists their default values. REQUEST=yes|no Specifies whether the remote computer can request to set up file transfers from your computer. When a remote computer calls your computer and requests to receive a file, this request can be granted or denied. no value is the default value. It will be used if the REQUEST option is not specified. The REQUEST option can appear in either a LOGNAME (remote calls you) entry or a MACHINE (you call remote) entry. SENDFILES=yes|call Specifies whether your computer can send the work queued for the remote computer. When a remote computer calls your computer and completes its work, it may attempt to take work your computer has queued for it. The call value is the default for the SENDFILE option. This option is only significant in LOGNAME entries since MACHINE entries apply when calls are made out to remote computers. If this option is used with a MACHINE entry, it will be ignored. READ and WRITE Specify the various parts of the file system that uucico can read from or write to. The READ and WRITE options can be used with either MACHINE or LOGNAME entries. The default for both the READ and WRITE options is the uucppublic directory as shown in the following example: READ=/usr/spool/uucppublic WRITE=/usr/spool/uucppublic Supplying ``/'' as a pathname gives permission to access any file that can be read by UUCP. Multiple entries must be separated by a colon. The READ option is for requesting files, and the WRITE option for depositing files. One of the values must be the prefix of any full path name of a file coming in or going out. Note that the READ and WRITE options do not affect the actual per- missions of a file or directory. You should be careful what direc- tories you make accessible for reading and writing by remote sys- tems. NOREAD and NOWRITE Specify exceptions to the READ and WRITE options or defaults. NOWRITE works in the same manner as the NOREAD option. NOREAD and NOWRITE can be used in both LOGNAME and MACHINE entries. CALLBACK Specifies in LOGNAME entries that no transaction will take place until the calling system is called back. There are two examples of when you would use CALLBACK. From a security standpoint, if you call back a machine you can be sure it is the machine it says it is. If you are doing long data transmissions, you can choose the machine that will be billed for the longer call. The default for the COMMAND option is no. The CALLBACK option is rarely used. If two sites have this option set for each other, a conversation will never get started. COMMANDS Specifies the commands in MACHINE entries that a remote computer can execute on your computer. This affects the security of your system; use it with extreme care. The uux program will generate remote execution requests and queue them to be transferred to the remote computer. Files and a command are sent to the target computer for remote execution. Note that COMMANDS is not used in a LOGNAME entry; COMMANDS in MACHINE entries define command permissions whether you call the remote sys- tem or it calls you. The default command that a remote computer can execute on your com- puter is rmail. If a command string is used in a MACHINE entry, the default commands are overridden. Full pathnames can also be used. Including the ALL value in the list means that any command from the remote computer specified in the entry will be executed. If you use this value, you give the remote computer full access to your computer. So, be careful; this allows far more access than normal users have. The VALIDATE option should be used with the COMMANDS option whenever potentially dangerous commands like cat and uucp are specified with the COMMANDS option. VALIDATE Used in conjunction with the COMMANDS option when specifying com- mands that are potentially dangerous to your computer's security. It provides a certain degree of verification of the caller's iden- tity. The use of the VALIDATE option requires that privileged com- puters have a unique login/password for UUCP transactions. An important aspect of this validation is that the login/password associated with this entry be protected. If an outsider gets that information, that particular VALIDATE option can no longer be con- sidered secure. (VALIDATE is merely an added level of security to the COMMANDS option, though it is a more secure way to open command access than ALL.) Entries for OTHER systems You may want to specify different option values for machines or logins that are not mentioned in specific MACHINE or LOGNAME entries. This may occur when there are many computers calling in that have the same set of permissions. The special name OTHER for the computer name can be used in a MACHINE or LOGNAME entry as follows: MACHINE=OTHER \ COMMANDS=rmail:/usr/local/bin/lc LOGNAME=OTHER \ REQUEST=yes SENDFILES=yes \ READ=/usr/spool/uucppublic \ WRITE=/usr/spool/uucppublic All options that can be set for specific machines or logins can be used with the OTHER value, although the use of the VALIDATE option makes lit- tle sense. Example This entry is for public login. It provides the default permissions. Note that use of this type of anonymous login is not encouraged. LOGNAME=nuucp \ MACHINE=OTHER \ READ=/usr/spool/uucppublic \ WRITE=/usr/spool/uucppublic \ SENDFILES=call REQUEST=no \ COMMANDS=/bin/rmail See also uucico(ADM), uucp(C), uux(C)