The hosts. When the optional username is specified, only users with entries on the specified host may log in to the local machine. When username is not specified, any user that has the same user name on both the remote and local machines may log in to the local machine. Note: Because the rsh and rcp utilities resend the current without the domain if it is too long and the rlogin utility does not, a user may require two entries in the hosts.
If the full name including domain is too long for the rshd service or daemon being used, the user needs one entry with the full user name including domain for use with rlogind and a second with the the same user name minus the domain for use with rshd. Here are some examples of hosts. Allows any user from the remote hosts tiny or big to connect to colossus. Allows the user forbin to connect to colossus from any remote host. Here are some examples of. In these examples, the. Trusted users are allowed to access the local system without supplying a password.
These files bypass the standard password-based user authentication mechanism. To maintain system security, care must be taken in creating and maintaining these files. The remote authentication procedure determines whether a user from a remote host should be allowed to access the local system with the identity of a local user.
Entries in these files can be of two forms. Positive entries allow access, while negative entries deny access. The authentication succeeds when a matching positive entry is found. The procedure fails when the first matching negative entry is found, or if no matching entries are found in either file. The order of entries is important. If the files contain both positive and negative entries, the entry that appears first will prevail.
In this case, the user sbob when logged in on eggs will be able to issue rsh commands for jdoe's account. Let's say that shs logged in to eggs issues the command:.
In order to open up your account in this way, jdoe not only has to trust sbob to behave himself, he has to believe that sbob's account on the remote system is fairly secure. Otherwise, he's opening his account up to a lot more potential trouble than he likely bargained for. Most of the time, users only include themselves in their. It is also possible for a user to open his account to everyone on a remote system or everyone on any remote system.
Both of these options are NOT recommended, as you would probably imagine. Many Unix sysadmins will either outlaw and often proactively remove such files. Others will shut down the rsh service altogether.
Rsh and related commands are generally disabled on systems by security conscious sysadmins because of the potential abuses. The rsh family of commands are, as you can probably surmise, vulnerable to spoofing attacks -- when someone on another system attempts to run an rsh command by pretending to be a trusted user or tries to pass off his system as a trusted host.
Ssh uses tightly coupled private and public keys that are virtually impossible to counterfeit. This means that you must have the files in place ahead of time, but the connection is considerably more secure and the connection is encrypted. If the rightmost column says " eggs. If it says "eggs", then that's all you should need. This story, "The Ins and Outs of. Sandra Henry-Stocker has been administering Unix systems for more than 30 years.
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