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Top Forums UNIX for Dummies Questions & Answers telnet refused / reverse DNS issue? Post 56507 by rm -r * on Monday 4th of October 2004 05:38:04 PM
Old 10-04-2004
I'm close to getting this resolved, thanks to your initial response, Hassan2.

I checked the man page on tcpd, which reports the following:

When looking up the client host name corresponding to an IP address, tcpd verifies the name that is returned by the DNS server by comparing it with the host name and address that are returned when the name is used to look up the corresponding IP address. This is know as a ``double reverse lookup''. If any discrepancy is detected, tcpd concludes that it is dealing with a host that is pretending to have someone else's host name.

The supplied version of tcpd was compiled with PARANOID defined, so that it will drop the connection in case of a host name/address mismatch.

Is it possible to edit hosts.allow with a valid subnet (or LIST of valid subnets) rather than each individual IP address?


Last edited by rm -r *; 10-04-2004 at 07:06 PM..
 

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

NAME
tcpdmatch - tcp wrapper oracle SYNOPSIS
tcpdmatch [-d] [-i inet_conf] daemon client tcpdmatch [-d] [-i inet_conf] daemon[@server] [user@]client DESCRIPTION
tcpdmatch predicts how the tcp wrapper would handle a specific request for service. Examples are given below. The program examines the tcpd access control tables (default /etc/hosts.allow and /etc/hosts.deny) and prints its conclusion. For maximal accuracy, it extracts additional information from your inetd network configuration file. When tcpdmatch finds a match in the access control tables, it identifies the matched rule. In addition, it displays the optional shell com- mands or options in a pretty-printed format; this makes it easier for you to spot any discrepancies between what you want and what the pro- gram understands. ARGUMENTS
The following two arguments are always required: daemon A daemon process name. Typically, the last component of a daemon executable pathname. client A host name or network address, or one of the `unknown' or `paranoid' wildcard patterns. When a client host name is specified, tcpdmatch gives a prediction for each address listed for that client. When a client address is specified, tcpdmatch predicts what tcpd would do when client name lookup fails. Optional information specified with the daemon@server form: server A host name or network address, or one of the `unknown' or `paranoid' wildcard patterns. The default server name is `unknown'. Optional information specified with the user@client form: user A client user identifier. Typically, a login name or a numeric userid. The default user name is `unknown'. OPTIONS
-d Examine hosts.allow and hosts.deny files in the current directory instead of the default ones. -i inet_conf Specify this option when tcpdmatch is unable to find your inetd.conf network configuration file, or when you suspect that the pro- gram uses the wrong one. EXAMPLES
To predict how tcpd would handle a telnet request from the local system: tcpdmatch in.telnetd localhost The same request, pretending that hostname lookup failed: tcpdmatch in.telnetd 127.0.0.1 To predict what tcpd would do when the client name does not match the client address: tcpdmatch in.telnetd paranoid On some systems, daemon names have no `in.' prefix, or tcpdmatch may need some help to locate the inetd configuration file. FILES
The default locations of the tcpd access control tables are: /etc/hosts.allow /etc/hosts.deny SEE ALSO
tcpdchk(8), tcpd configuration checker hosts_access(5), format of the tcpd access control tables. hosts_options(5), format of the language extensions. inetd.conf(5), format of the inetd control file. AUTHORS
Wietse Venema (wietse@wzv.win.tue.nl), Department of Mathematics and Computing Science, Eindhoven University of Technology Den Dolech 2, P.O. Box 513, 5600 MB Eindhoven, The Netherlands TCPDMATCH(8)
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