rexecd - The remote execution server
-s 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 pseu-
The rexecd daemon is the server for the rexec(3) routine. The server pro-
vides remote execution facilities with authentication based on usernames
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:
1. The server reads characters from the socket up to a null (`\0') byte.
The resultant string is interpreted as an ASCII number, base 10.
2. 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
3. A null-terminated username of at most 16 bytes is retrieved on the
4. A null-terminated, unencrypted password of at most 80 bytes is
retrieved on the initial socket.
5. 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.
6. 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 suc-
cessful, 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.
7. 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.
Except for the last diagnostic message listed, 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 bytes.
Password too long.
The password is longer than 80 bytes.
Command too long.
The command line passed exceeds the size of the argument list (as con-
figured into the system).
No password file entry for the username existed.
The wrong password was supplied.
No remote directory.
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
Indicating Login incorrect as opposed to Password incorrect is a security
breach that allows people to probe a system for users with null passwords.
Specifies the command path