generate barcode in asp.net c# Tuning Access to Services with TCP Wrapper in Font

Generate Data Matrix 2d barcode in Font Tuning Access to Services with TCP Wrapper

Tuning Access to Services with TCP Wrapper
Generating ECC200 In None
Using Barcode encoder for Font Control to generate, create Data Matrix ECC200 image in Font applications.
www.OnBarcode.com
Printing PDF-417 2d Barcode In None
Using Barcode encoder for Font Control to generate, create PDF 417 image in Font applications.
www.OnBarcode.com
If a service runs from xinetd, it can be secured with TCP Wrapper. To ensure that you can use it, install TCP wrapper using apt-get install tcpd as root. Stated in a more general way, if a service is using the libwrap.so library module, you can secure it with TCP Wrapper. Because
Painting Code-39 In None
Using Barcode creator for Font Control to generate, create Code 3 of 9 image in Font applications.
www.OnBarcode.com
Creating Code 128 In None
Using Barcode printer for Font Control to generate, create Code 128 Code Set A image in Font applications.
www.OnBarcode.com
CHAPTER 9 CONFIGURING NETWORK INFRASTRUCTURE SERVICES
Draw Data Matrix ECC200 In None
Using Barcode generation for Font Control to generate, create Data Matrix ECC200 image in Font applications.
www.OnBarcode.com
USS-128 Creator In None
Using Barcode creation for Font Control to generate, create EAN / UCC - 13 image in Font applications.
www.OnBarcode.com
xinetd uses this module, you can secure it this way. Other services that aren t started with xinetd but do use this library can be secured with TCP Wrapper as well. To check whether a service is capable of working with TCP Wrapper, use the ldd command followed by the complete name of the service you want to check. If libwrap.so is listed, TCP Wrapper works for the service. If it isn t, use a generic firewall such as iptables. See Listing 9-18 for an example. Listing 9-18. Checking Whether a Service Can Be Secured with TCP Wrapper root@RNA:~# ldd /usr/sbin/xinetd linux-gate.so.1 => (0xffffe000) libwrap.so.0 => /lib/libwrap.so.0 (0xb7fd0000) libnsl.so.1 => /lib/tls/i686/cmov/libnsl.so.1 (0xb7fb9000) libm.so.6 => /lib/tls/i686/cmov/libm.so.6 (0xb7f91000) libcrypt.so.1 => /lib/tls/i686/cmov/libcrypt.so.1 (0xb7f63000) libc.so.6 => /lib/tls/i686/cmov/libc.so.6 (0xb7e22000) /lib/ld-linux.so.2 (0xb7fe3000) TCP Wrapper was developed before xinetd existed and when only its predecessor inetd was available. This service didn t include any way of regulating access to services, so inetd could be used to start tcpd, TCP Wrapper, which in turn could be configured to start the necessary service. The task of tcpd was to check whether a host trying to connect to the service was allowed access or not. The nice thing about tcpd is that it sits between (x)inetd and the service a client is connecting to. Therefore, from the outside it s not possible to see whether tcpd is blocking access to a service or whether the service simply isn t there.
Encoding Denso QR Bar Code In None
Using Barcode generator for Font Control to generate, create QR Code ISO/IEC18004 image in Font applications.
www.OnBarcode.com
USD - 8 Maker In None
Using Barcode creator for Font Control to generate, create USD8 image in Font applications.
www.OnBarcode.com
Working with the /etc/hosts.allow and /etc/hosts.deny Configuration Files
Generate ECC200 In Java
Using Barcode drawer for Java Control to generate, create Data Matrix 2d barcode image in Java applications.
www.OnBarcode.com
Data Matrix Maker In Objective-C
Using Barcode maker for iPad Control to generate, create Data Matrix 2d barcode image in iPad applications.
www.OnBarcode.com
TCP Wrapper works with two configuration files to determine whether access is allowed or not: /etc/hosts.allow and /etc/hosts.deny. The first has a list of all hosts that can access a service, and the second contains a list of hosts for which access is denied. TCP Wrapper always first reads the /etc/hosts.allow file. If the host that tries to connect is in there, access is allowed. Only if the name of the hosts is not in /etc/hosts.allow does tcpd check /etc/hosts. deny. If the host is in there, access is blocked; if it isn t, access is allowed. Access is also allowed if one of the two configuration files is empty or does not exist.
Encoding Barcode In Java
Using Barcode generator for Java Control to generate, create Barcode image in Java applications.
www.OnBarcode.com
EAN-13 Recognizer In None
Using Barcode recognizer for Software Control to read, scan read, scan image in Software applications.
www.OnBarcode.com
Caution Test before you trust that TCP Wrapper is really protecting your services. A small error in the
Data Matrix ECC200 Creator In .NET Framework
Using Barcode drawer for Visual Studio .NET Control to generate, create ECC200 image in VS .NET applications.
www.OnBarcode.com
Decode EAN 13 In .NET
Using Barcode decoder for .NET Control to read, scan read, scan image in VS .NET applications.
www.OnBarcode.com
configuration can have the result that TCP Wrapper doesn t work.
Barcode Maker In Objective-C
Using Barcode printer for iPhone Control to generate, create Barcode image in iPhone applications.
www.OnBarcode.com
EAN / UCC - 13 Drawer In None
Using Barcode drawer for Microsoft Excel Control to generate, create EAN-13 Supplement 5 image in Excel applications.
www.OnBarcode.com
The generic syntax of the lines that you can include in the /etc/hosts.allow and /etc/hosts.deny files is not hard to understand: daemon:host[:option : option ...] Of these, daemon is the process involved, host is the list of hosts that you want to allow or deny access to, and option is a list of options you want to include. Note that instead of
Barcode Scanner In .NET Framework
Using Barcode decoder for .NET framework Control to read, scan read, scan image in Visual Studio .NET applications.
www.OnBarcode.com
QR-Code Generator In Java
Using Barcode maker for Java Control to generate, create QR Code 2d barcode image in Java applications.
www.OnBarcode.com
CHAPTER 9 CONFIGURING NETWORK INFRASTRUCTURE SERVICES
Encoding USS Code 39 In Objective-C
Using Barcode creator for iPhone Control to generate, create Code 3/9 image in iPhone applications.
www.OnBarcode.com
Linear Barcode Encoder In Visual Studio .NET
Using Barcode maker for ASP.NET Control to generate, create 1D Barcode image in ASP.NET applications.
www.OnBarcode.com
referring to a specific host or daemon, some generic keywords can be used as well. Table 9-2 summarizes these TCP Wrapper keywords. Table 9-2. TCP Wrapper Keywords
Keyword
ALL LOCAL UNKNOWN KNOWN PARANOID
Description
Refers to all daemons or all hosts. Note that you can define an exception to ALL by using the keyword EXCEPT. This option can be used for host names only and refers to all host names that do not have a dot in their name. All host names for which tcpd cannot identify the name. All host names that could be identified by their name and matching IP address. All hosts for which the host name does not match the given IP address.
Let s start with the example shown in Listing 9-19. Listing 9-19. Simple Example of /etc/hosts.allow and /etc/hosts.deny RNA: ~ # cat /etc/hosts.allow ALL: LOCAL RNA: ~ # cat /etc/hosts.deny famd, netstatd, ps: ALL In this example, incoming hosts are first matched against the /etc/hosts.allow file, in which access to all services is granted for everything coming in from the localhost. Local processes look no further. For connections coming in from remote hosts, now the /etc/hosts. deny file is checked. In this file, you can see that access is denied to the famd, netstatd, and ps services for all hosts. So, in this example, all other services that are controlled by tcpd can also be accessed by all external hosts. As you notice, this example doesn t show anything very secure, but it s possible to create a more secure configuration (see Listing 9-20). Listing 9-20. More Complex Example of /etc/hosts.allow and /etc/hosts.deny RNA: ~ # cat /etc/hosts.allow ALL: SFO.sandervanvugt.com in.telnetd: 192.168.1.1 ALL EXCEPT in.telnetd: 192.168. RNA ~ # cat /etc/hosts.deny ALL: ALL In this example, you should first notice that a policy is set to specifically deny access for all hosts to all services in /etc/hosts.deny. This is good because it creates a mechanism to control access; if the host doesn t have an entry in /etc/hosts.allow, it doesn t get access to the services that are controlled by tcpd. Three different lines are specified in the /etc/hosts.allow file in Listing 9-20. The first line grants access to all services for the host SFO.sandervanvugt.com. Then 192.168.1.1 gets access to only the telnet service, and in the third line all other hosts whose IP address starts with 192.168 get access to all services except telnet. Note that order matters in this example:
Copyright © OnBarcode.com . All rights reserved.