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rexecd(8) [osf1 man page]

rexecd(8)						      System Manager's Manual							 rexecd(8)

NAME
rexecd - The remote execution server SYNOPSIS
rexecd [-s] OPTIONS
Causes rexecd to check for the ptys keyword in the /etc/securettys file and to deny execution of the request if it is from root and on a pseudoterminal. DESCRIPTION
The rexecd daemon is the server for the rexec(3) routine. The server provides remote execution facilities with authentication based on usernames and passwords. The rexecd daemon listens for service requests at the port indicated in the exec service specification; see services(4). When a service request is received, the following protocol is initiated: The server reads characters from the socket up to a null (`') byte. The resul- tant string is interpreted as an ASCII number, base 10. If the number received in step 1 is nonzero, it is interpreted as the port number of a secondary stream to be used for the stderr. A second connection is then created to the specified port on the client's machine. A null-terminated username of at most 16 bytes is retrieved on the initial socket. A null-terminated, unencrypted password of at most 80 bytes is retrieved on the initial socket. A null-terminated command to be passed to a shell is retrieved on the initial socket. The length of the command is limited by the upper bound on the size of the system's argument list. The rexecd server then validates the user as is done at login time and, if started with the -s option, verifies that the /etc/securettys file is not setup to deny the user. If the authentication was successful, rexecd changes to the user's home directory, and establishes the user and group protections for the user. If any of these steps fail, the connection is aborted with a diagnostic message returned. A null byte is returned on the initial socket and the command line is passed to the normal login shell of the user. The shell inherits the network connections established by rexecd. DIAGNOSTICS
Except for the last diagnostic message listed, all diagnostic messages are returned on the initial socket, after which any network connec- tions are closed. An error is indicated by a leading byte with a value of 1 (0 is returned in step 7 above upon successful completion of all the steps prior to the command execution). The name is longer than 16 bytes. The password is longer than 80 bytes. The command line passed exceeds the size of the argument list (as configured into the system). No password file entry for the username existed. The wrong password was supplied. The chdir command to the home directory failed. A fork by the server failed. The user's login shell could not be started. This message is returned on the connection associated with stderr and is not preceded by a flag byte. CAUTIONS
IndicatingLogin incorrect as opposed to Password incorrect is a security breach that allows people to probe a system for users with null passwords. FILES
Specifies the command path RELATED INFORMATION
Functions: rexec(3) Files: securettys(4) delim off rexecd(8)

Check Out this Related Man Page

REXECD(8)						    BSD System Manager's Manual 						 REXECD(8)

NAME
rexecd -- remote execution server SYNOPSIS
rexecd DESCRIPTION
Rexecd is the server for the rexec(3) routine. The server provides remote execution facilities with authentication based on user names and passwords. Rexecd listens for service requests at the port indicated in the ``exec'' service specification; see services(5). When a service request is received the following protocol is initiated: 1. The server reads characters from the socket up to a NUL ('') byte. The resultant string is interpreted as an ASCII number, base 10. 2. If the number received in step 1 is non-zero, it is interpreted as the port number of a secondary stream to be used for the stderr. A second connection is then created to the specified port on the client's machine. 3. A NUL terminated user name of at most 16 characters is retrieved on the initial socket. 4. A NUL terminated, unencrypted password of at most 16 characters is retrieved on the initial socket. 5. A NUL terminated command to be passed to a shell is retrieved on the initial socket. The length of the command is limited by the upper bound on the size of the system's argument list. 6. Rexecd then validates the user as is done at login time and, if the authentication was successful, changes to the user's home directory, and establishes the user and group protections of the user. If any of these steps fail the connection is aborted with a diagnostic mes- sage returned. 7. A NUL byte is returned on the initial socket and the command line is passed to the normal login shell of the user. The shell inherits the network connections established by rexecd. DIAGNOSTICS
Except for the last one listed below, all diagnostic messages are returned on the initial socket, after which any network connections are closed. An error is indicated by a leading byte with a value of 1 (0 is returned in step 7 above upon successful completion of all the steps prior to the command execution). username too long The name is longer than 16 characters. password too long The password is longer than 16 characters. command too long The command line passed exceeds the size of the argument list (as configured into the system). Login incorrect. No password file entry for the user name existed. Password incorrect. The wrong password was supplied. No remote directory. The chdir command to the home directory failed. Try again. A fork by the server failed. <shellname>: ... The user's login shell could not be started. This message is returned on the connection associated with the stderr, and is not pre- ceded by a flag byte. SEE ALSO
rexec(3) BUGS
Indicating ``Login incorrect'' as opposed to ``Password incorrect'' is a security breach which allows people to probe a system for users with null passwords. A facility to allow all data and password exchanges to be encrypted should be present. HISTORY
The rexecd command appeared in 4.2BSD. 4.2 Berkeley Distribution June 1, 1994 4.2 Berkeley Distribution
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