Isn't libwrap the old way of doing things? Would using iptables not be faster?
Tom Dwight Victor <[EMAIL PROTECTED]> Sent by: [EMAIL PROTECTED] 12/01/2005 02:27 PM Please respond to Dwight Victor <[EMAIL PROTECTED]>; Please respond to LUAU <[email protected]> To LUAU <[email protected]> cc Subject Re: [LUAU] Excellent SSH advice Are you sure about that Vince? The way I understand how tcp_wrappers works is that the wrapper is actually listening on the service port and when the attempt is successfully authenticated against the /etc/hosts.allow and /etc/hosts.deny files, the wrapper passes control to the actual service. A quick google gives me this from Red Hat: http://www.redhat.com/docs/manuals/linux/RHL-8.0-Manual/ref-guide/ch-tcpwrappers.html The tcpd manpage says this: --- TCPD(8) TCPD(8) NAME tcpd - access control facility for internet services DESCRIPTION The tcpd program can be set up to monitor incoming requests for telnet, finger, ftp, exec, rsh, rlogin, tftp, talk, comsat and other services that have a one-to-one mapping onto executable files. The program supports both 4.3BSD-style sockets and System V.4-style TLI. Functionality may be limited when the protocol underneath TLI is not an internet protocol. Operation is as follows: whenever a request for service arrives, the inetd daemon is tricked into running the tcpd program instead of the desired server. tcpd logs the request and does some additional checks. When all is well, tcpd runs the appropriate server program and goes away. Optional features are: pattern-based access control, client username lookups with the RFC 931 etc. protocol, protection against hosts that pre tend to have someone elses host name, and protection against hosts that pretend to have someone elses network address. LOGGING Connections that are monitored by tcpd are reported through the syslog(3) facility. Each record contains a time stamp, the client host name and the name of the requested service. The information can be useful to detect unwanted activities, especially when logfile information from sev eral hosts is merged. In order to find out where your logs are going, examine the syslog configuration file, usually /etc/syslog.conf. ACCESS CONTROL Optionally, tcpd supports a simple form of access control that is based on pattern matching. The access-control software provides hooks for the execution of shell commands when a pattern fires. For details, see the hosts_access(5) manual page. HOST NAME VERIFICATION The authentication scheme of some protocols (rlogin, rsh) relies on host names. Some implementations believe the host name that they get from any random name server; other implementations are more careful but use a flawed algorithm. tcpd verifies the client host name that is returned by the address->name DNS server by looking at the host name and address that are returned by the name->address DNS server. If any discrepancy is detected, tcpd concludes that it is dealing with a host that pretends to have someone elses host name. If the sources are compiled with -DPARANOID, tcpd will drop the connection in case of a host name/address mismatch. Otherwise, the hostname can be matched with the PARANOID wildcard, after which suitable action can be taken. HOST ADDRESS SPOOFING Optionally, tcpd disables source-routing socket options on every connection that it deals with. This will take care of most attacks from hosts that pretend to have an address that belongs to someone elses network. UDP services do not benefit from this protection. This feature must be turned on at compile time. RFC 931 When RFC 931 etc. lookups are enabled (compile-time option) tcpd will attempt to establish the name of the client user. This will succeed only if the client host runs an RFC 931-compliant daemon. Client user name lookups will not work for datagram-oriented connections, and may cause noticeable delays in the case of connections from PCs. --- If I'm wrong, then I'm wrong...but I don't think so. Dwight... On Wed, 12 Jan 2005 10:39:35 -1000, Vince Hoang <[EMAIL PROTECTED]> wrote: > On Wed, Jan 12, 2005 at 09:31:56AM -1000, Dwight Victor wrote: > > If you know the IP addresses of the machines that you'll be > > SSHing from...it's best to compile your version of SSH to > > support tcp_wrappers and configure your /etc/hosts.allow and > > /etc/hosts.deny files to only allow SSH access from your know > > IP addresses. > > I believe most packaged versions of OpenSSH come prebuilt with > tcp-wrappers, so no recompilation is needed. > > > This also helps cut down on those irritating automated SSH > > attacks. > > When using the built-in tcp-wrapper support, the attack will > still hit the sshd before the attack host is dropped, and > potentially leave you open to an undocumented buffer overflow. > > Instead, if you limit host access at the firewall level, the > attack will never reach the sshd. > > Another alternative is to move your sshd to a different port. > This will thwart the attacks that only look at tcp/22 for a > running SSH server, but this relies on security through obscurity > alone. > > -Vince > _______________________________________________ > [email protected] mailing list > http://lists.hosef.org/cgi-bin/mailman/listinfo/luau > -- Dwight Victor Resident Mad Scientist and All Around Good Guy [EMAIL PROTECTED] _______________________________________________ [email protected] mailing list http://lists.hosef.org/cgi-bin/mailman/listinfo/luau
