Linux Security: OS & Service Level Security in Linux Part-2

<div dir="ltr" style="text-align: left;" trbidi="on"> <div class="separator" style="clear: both; text-align: center;"> <a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjGRemCcYh-4YycwIWJZfwSQ4x7AaTjhgjax-1OWCqBgBRAYsVTP-xVSCoSrlwNoRJLyvQXi1EX8MJnEsfdaYekZkmk35D9al7qhQH-uMlOKvmJnqBJV85XaWcmFfiHuiMdb9ZFkz0g134H/s1600/Linux-security-part2-700x454.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjGRemCcYh-4YycwIWJZfwSQ4x7AaTjhgjax-1OWCqBgBRAYsVTP-xVSCoSrlwNoRJLyvQXi1EX8MJnEsfdaYekZkmk35D9al7qhQH-uMlOKvmJnqBJV85XaWcmFfiHuiMdb9ZFkz0g134H/s1600/Linux-security-part2-700x454.jpg" /></a></div> <br /> <div class="wpb_row row-fluid" style="background-color: white; color: #262626; font-family: 'PT Sans', sans-serif; font-size: 15px; line-height: 23px; width: 699.96875px;"> <div class="span12 wpb_column column_container" style="box-sizing: border-box; float: left; margin-left: 0px; min-height: 31px; position: relative; width: 699.96875px;"> <div class="wpb_wrapper"> <div class="wpb_text_column wpb_content_element "> <div class="wpb_wrapper"> <div style="margin-bottom: 23px;"> <strong>Linux Security > OS & Service Level Security in Linux>Samba Server</strong></div> <h6 style="color: #222222; font-size: 22px; line-height: 28px; margin: 25px 0px 27px; text-rendering: optimizeLegibility;"> Samba Server:</h6> <div style="margin-bottom: 23px;"> <strong>About Samba Server:</strong></div> <div style="margin-bottom: 23px;"> Samba is an Open Source/Free Software suite that provides seamless file and print services to SMB/CIFS clients. Samba is freely available, unlike other SMB/CIFS implementations, and allows for interoperability between Linux/Unix servers and Windows-based clients.</div> <div style="margin-bottom: 23px;"> <strong>Service:</strong>  smb,nmb<br /> <strong>Port:</strong> 137,138,139,445<br /> <strong>Config File:</strong> /etc/samba/smb.conf</div> <div style="margin-bottom: 23px;"> <strong>Embeded security with samba serve</strong>r</div> <div style="margin-bottom: 23px;"> <strong>Global parameter</strong><strong> </strong></div> <div style="margin-bottom: 23px;"> <strong>interfaces </strong> = lo eth0 eth1 192.168.0.0/24<span style="color: red;"> <—samba service available on this interfaces only</span><br /> <strong>hosts allow</strong> = 127.  192.168.0. <span style="color: red;"><–samba service can be access through these IP Ranges only </span><br /> </div> <div style="margin-bottom: 23px;"> <strong>Samba Share parameter</strong></div> <div style="margin-bottom: 23px;"> <strong>valid users</strong> = vikas prabhat   <span style="color: red;"><–only these users can access samba share</span><br /> <strong>veto files </strong> = /*.exe/*.pdf/  <span style="color: red;"><—stop saving .exe  and .pdf files</span></div> <div style="margin-bottom: 23px;"> <strong>public = no</strong><br /> <strong>writable = yes</strong><br /> <strong>browseable = yes</strong><br /> <strong>create mask = 0765</strong></div> </div> </div> </div> </div> </div> <div class="wpb_row row-fluid" style="background-color: white; width: 699.96875px;"> <div class="span12 wpb_column column_container" style="box-sizing: border-box; float: left; margin-left: 0px; min-height: 31px; position: relative; width: 699.96875px;"> <div class="wpb_wrapper"> <div class="td_block_wrap td_text_with_title" style="padding-bottom: 20px !important; position: relative;"> <h4 class="block-title" style="border-bottom-color: rgb(77, 178, 236); border-bottom-style: solid; border-bottom-width: 2px; color: #222222; font-family: 'PT Sans', sans-serif; font-size: 28px; line-height: 34px; margin: 25px 0px 27px; position: relative; text-rendering: optimizeLegibility;"> <span style="background-color: #4db2ec; color: white; font-family: 'Roboto Condensed', sans-serif; padding: 3px 10px; z-index: 1;">DNS Server Securities</span></h4> <div class="td_mod_wrap" style="margin-bottom: 15px;"> <strong style="color: #262626; font-family: 'PT Sans', sans-serif; font-size: 15px; line-height: 23px;">Linux Security > OS and Service level Security > DNS Server</strong><br /> <div style="color: #262626; font-family: 'PT Sans', sans-serif; font-size: 15px; line-height: 23px; margin-bottom: 23px; position: relative; top: -9px;"> </div> <div style="color: #262626; font-family: 'PT Sans', sans-serif; font-size: 15px; line-height: 23px; margin-bottom: 23px; position: relative; top: -9px;"> <strong>About DNS Server :</strong></div> <div style="color: #262626; font-family: 'PT Sans', sans-serif; font-size: 15px; line-height: 23px; margin-bottom: 23px; position: relative; top: -9px;"> Domain Name Servers (DNS) are the Internet’s equivalent of a phone book. They maintain a directory of domain names and translate them to Internet Protocol (IP) addresses.</div> <div style="color: #262626; font-family: 'PT Sans', sans-serif; font-size: 15px; line-height: 23px; margin-bottom: 23px; position: relative; top: -9px;"> This is necessary because, although domain names are easy for people to remember, computers or machines, access websites based on IP addresses.</div> <div style="color: #262626; font-family: 'PT Sans', sans-serif; font-size: 15px; line-height: 23px; margin-bottom: 23px; position: relative; top: -9px;"> <strong>Service: </strong> named<br /> <strong>Port:</strong> 53 UDP<br /> <strong>Config FIle:</strong>  /etc/named.conf</div> <div style="color: #262626; font-family: 'PT Sans', sans-serif; font-size: 15px; line-height: 23px; margin-bottom: 23px; position: relative; top: -9px;"> ———————————————————————————–</div> <div style="color: #262626; font-family: 'PT Sans', sans-serif; font-size: 15px; line-height: 23px; margin-bottom: 23px; position: relative; top: -9px;"> <strong>Basic Configuration</strong>  <strong>/etc/named.conf</strong></div> <div style="margin-bottom: 23px; position: relative; top: -9px;"> <span style="color: #262626; font-family: PT Sans, sans-serif;"><span style="font-size: 15px; line-height: 23px;"><b>options {</b></span></span><span style="color: #262626; font-family: 'PT Sans', sans-serif; font-size: 15px; line-height: 23px;"> listen-on port 53 { 127.0.0.1; };</span><span style="color: #262626; font-family: 'PT Sans', sans-serif; font-size: 15px; line-height: 23px;"> listen-on-v6 port 53 { ::1; };</span><span style="color: #262626; font-family: 'PT Sans', sans-serif; font-size: 15px; line-height: 23px;"> directory "/var/named";</span><span style="color: #262626; font-family: 'PT Sans', sans-serif; font-size: 15px; line-height: 23px;"> dump-file "/var/named/data/cache_dump.db";</span><span style="color: #262626; font-family: 'PT Sans', sans-serif; font-size: 15px; line-height: 23px;"> statistics-file "/var/named/data/named_stats.txt";</span><span style="color: #262626; font-family: 'PT Sans', sans-serif; font-size: 15px; line-height: 23px;"> memstatistics-file "/var/named/data/named_mem_stats.txt";</span><span style="color: #262626; font-family: 'PT Sans', sans-serif; font-size: 15px; line-height: 23px;"> allow-query { localhost; };</span><span style="color: #262626; font-family: 'PT Sans', sans-serif; font-size: 15px; line-height: 23px;"> listen-on port 53 { 127.0.0.1;192.168.1.254; };</span><span style="color: #262626; font-family: 'PT Sans', sans-serif; font-size: 15px; line-height: 23px;"> listen-on-v6 port 53 { ::1; };</span><span style="color: #262626; font-family: 'PT Sans', sans-serif; font-size: 15px; line-height: 23px;"> directory "/var/named";</span><span style="color: #262626; font-family: 'PT Sans', sans-serif; font-size: 15px; line-height: 23px;"> dump-file "/var/named/data/cache_dump.db";</span><span style="color: #262626; font-family: 'PT Sans', sans-serif; font-size: 15px; line-height: 23px;"> statistics-file "/var/named/data/named_stats.txt";</span><span style="color: #262626; font-family: 'PT Sans', sans-serif; font-size: 15px; line-height: 23px;"> memstatistics-file "/var/named/data/named_mem_stats.txt";</span><b style="color: #262626; font-family: 'PT Sans', sans-serif; font-size: 15px; line-height: 23px;"> };</b></div> <div style="color: #262626; font-family: 'PT Sans', sans-serif; font-size: 15px; line-height: 23px; margin-bottom: 23px; position: relative; top: -9px;"> <strong>Restricting zone transfers</strong></div> <div style="color: #262626; font-family: 'PT Sans', sans-serif; font-size: 15px; line-height: 23px; margin-bottom: 23px; position: relative; top: -9px;"> In order for your slave server(s) to be able to answer queries about your domain, they must be able to transfer the zone information from your primary server. Very few others have a need to do so. Therefore restrict zone transfers using the allow-transfer option, assuming 192.168.1.4 is the IP address of ns.linuxgateway.fake and adding yourself for debugging purposes:</div> <div style="color: #262626; font-family: 'PT Sans', sans-serif; font-size: 15px; line-height: 23px; margin-bottom: 23px; position: relative; top: -9px;"> zone “linuxgateway.fake” {<br /> allow-transfer { 192.168.1.4; localhost; };<br /> };</div> <div style="color: #262626; font-family: 'PT Sans', sans-serif; font-size: 15px; line-height: 23px; margin-bottom: 23px; position: relative; top: -9px;"> By restricting zone transfers you ensure that the only information available to people is that which they ask for directly – no one can just ask for all the details about your set-up.</div> <div style="color: #262626; font-family: 'PT Sans', sans-serif; font-size: 15px; line-height: 23px; margin-bottom: 23px; position: relative; top: -9px;"> ——————————————————————–</div> <h2 style="color: #222222; font-family: 'PT Sans', sans-serif; font-size: 36px; line-height: 42px; margin: 25px 0px 27px; text-rendering: optimizeLegibility;"> Protecting against spoofing</h2> <div style="color: #262626; font-family: 'PT Sans', sans-serif; font-size: 15px; line-height: 23px; margin-bottom: 23px; position: relative; top: -9px;"> Firstly, disable any queries for domains you don’t own, except from your internal/local machines. This not only helps prevent malicious use of your DNS server, but also reduces unnecessary use of your server.</div> <div style="color: #262626; font-family: 'PT Sans', sans-serif; font-size: 15px; line-height: 23px; margin-bottom: 23px; position: relative; top: -9px;"> Further, disable recursive queries except from internal/local sources. This reduces the risk of cache poisoning attacks (where false data is fed to your server).</div> <table class="crayon-table" style="background-attachment: initial !important; background-clip: initial !important; background-color: black; background-image: none !important; background-origin: initial !important; background-position: initial !important; background-repeat: initial !important; background-size: initial !important; border-collapse: collapse !important; border-image-outset: initial !important; border-image-repeat: initial !important; border-image-slice: initial !important; border-image-source: initial !important; border-image-width: initial !important; border-spacing: 0px !important; border: none !important; color: #262626; font-family: 'Ubuntu Mono', UbuntuMonoRegular, 'Courier New', monospace; font-size: 12px; line-height: 15px; margin-bottom: 0px !important; margin-left: -26px; margin-right: 0px !important; margin-top: 0px !important; max-width: 100%; padding: 0px !important; table-layout: auto !important; width: auto !important;"><tbody> <tr class="crayon-row" style="background: 0px 50%; border: none !important; margin: 0px !important; padding: 0px !important; vertical-align: top !important;"><td class="crayon-nums " data-settings="hide" style="background-attachment: initial !important; background-clip: initial !important; background-image: initial !important; background-origin: initial !important; background-position: initial !important; background-repeat: initial !important; background-size: initial !important; border-bottom-width: 0px; border-left-width: 0px; border-right-color: rgb(255, 255, 255) !important; border-right-width: 1px !important; border-style: initial; border-top-width: 0px; color: rgb(73, 73, 73) !important; margin: 0px !important; padding: 0px !important; vertical-align: top !important;"><div class="crayon-nums-content" style="background: 0px 50%; border: 0px; font-size: 15px !important; margin: 0px; padding: 0px; white-space: nowrap;"> <div class="crayon-num" data-line="crayon-55a9629c2715a059304565-3" style="background: 0px 50%; border: 0px; font-family: inherit; font-size: inherit !important; font-weight: inherit !important; height: inherit; line-height: inherit !important; margin: 0px; padding: 0px 5px; text-align: center;"> 3</div> <div class="crayon-num crayon-striped-num" data-line="crayon-55a9629c2715a059304565-4" style="background-attachment: initial !important; background-clip: initial !important; background-image: initial !important; background-origin: initial !important; background-position: initial !important; background-repeat: initial !important; background-size: initial !important; border: 0px; font-family: inherit; font-size: inherit !important; font-weight: inherit !important; height: inherit; line-height: inherit !important; margin: 0px; padding: 0px 5px; text-align: center;"> 4</div> <div class="crayon-num" data-line="crayon-55a9629c2715a059304565-5" style="background: 0px 50%; border: 0px; font-family: inherit; font-size: inherit !important; font-weight: inherit !important; height: inherit; line-height: inherit !important; margin: 0px; padding: 0px 5px; text-align: center;"> 5</div> <div class="crayon-num crayon-striped-num" data-line="crayon-55a9629c2715a059304565-6" style="background-attachment: initial !important; background-clip: initial !important; background-image: initial !important; background-origin: initial !important; background-position: initial !important; background-repeat: initial !important; background-size: initial !important; border: 0px; font-family: inherit; font-size: inherit !important; font-weight: inherit !important; height: inherit; line-height: inherit !important; margin: 0px; padding: 0px 5px; text-align: center;"> 6</div> <div class="crayon-num" data-line="crayon-55a9629c2715a059304565-7" style="background: 0px 50%; border: 0px; font-family: inherit; font-size: inherit !important; font-weight: inherit !important; height: inherit; line-height: inherit !important; margin: 0px; padding: 0px 5px; text-align: center;"> 7</div> <div class="crayon-num crayon-striped-num" data-line="crayon-55a9629c2715a059304565-8" style="background-attachment: initial !important; background-clip: initial !important; background-image: initial !important; background-origin: initial !important; background-position: initial !important; background-repeat: initial !important; background-size: initial !important; border: 0px; font-family: inherit; font-size: inherit !important; font-weight: inherit !important; height: inherit; line-height: inherit !important; margin: 0px; padding: 0px 5px; text-align: center;"> 8</div> <div class="crayon-num" data-line="crayon-55a9629c2715a059304565-9" style="background: 0px 50%; border: 0px; font-family: inherit; font-size: inherit !important; font-weight: inherit !important; height: inherit; line-height: inherit !important; margin: 0px; padding: 0px 5px; text-align: center;"> 9</div> <div class="crayon-num crayon-striped-num" data-line="crayon-55a9629c2715a059304565-10" style="background-attachment: initial !important; background-clip: initial !important; background-image: initial !important; background-origin: initial !important; background-position: initial !important; background-repeat: initial !important; background-size: initial !important; border: 0px; font-family: inherit; font-size: inherit !important; font-weight: inherit !important; height: inherit; line-height: inherit !important; margin: 0px; padding: 0px 5px; text-align: center;"> 10</div> <div class="crayon-num" data-line="crayon-55a9629c2715a059304565-11" style="background: 0px 50%; border: 0px; font-family: inherit; font-size: inherit !important; font-weight: inherit !important; height: inherit; line-height: inherit !important; margin: 0px; padding: 0px 5px; text-align: center;"> 11</div> </div> </td><td class="crayon-code" style="background: 0px 50%; border: 0px; margin: 0px !important; padding: 0px !important; vertical-align: top !important; width: 672px;"><div class="crayon-pre" style="background: none !important; border: none !important; color: rgb(255, 255, 255) !important; font-size: 15px !important; margin: 0px; overflow: visible; padding: 0px; tab-size: 4; white-space: pre;"> <div class="crayon-line" id="crayon-55a9629c2715a059304565-1" style="background: 0px 50%; border: 0px; font-family: inherit; font-size: inherit !important; font-weight: inherit !important; height: inherit; line-height: inherit !important; margin: 0px; padding: 0px 5px;"> <span class="crayon-e" style="font-family: inherit; font-size: inherit !important; font-weight: inherit !important; height: inherit; line-height: inherit !important;">options</span><span class="crayon-h" style="font-family: inherit; font-size: inherit !important; font-weight: inherit !important; height: inherit; line-height: inherit !important;"> </span><span class="crayon-sy" style="font-family: inherit; font-size: inherit !important; font-weight: inherit !important; height: inherit; line-height: inherit !important;">{</span></div> <div class="crayon-line crayon-striped-line" id="crayon-55a9629c2715a059304565-2" style="background-attachment: initial !important; background-clip: initial !important; background-image: initial !important; background-origin: initial !important; background-position: initial !important; background-repeat: initial !important; background-size: initial !important; border: 0px; font-family: inherit; font-size: inherit !important; font-weight: inherit !important; height: inherit; line-height: inherit !important; margin: 0px; padding: 0px 5px;"> <span class="crayon-h" style="font-family: inherit; font-size: inherit !important; font-weight: inherit !important; height: inherit; line-height: inherit !important;">      </span><span class="crayon-e" style="font-family: inherit; font-size: inherit !important; font-weight: inherit !important; height: inherit; line-height: inherit !important;">allow</span><span class="crayon-o" style="font-family: inherit; font-size: inherit !important; font-weight: inherit !important; height: inherit; line-height: inherit !important;">-</span><span class="crayon-e" style="font-family: inherit; font-size: inherit !important; font-weight: inherit !important; height: inherit; line-height: inherit !important;">query</span><span class="crayon-h" style="font-family: inherit; font-size: inherit !important; font-weight: inherit !important; height: inherit; line-height: inherit !important;"> </span><span class="crayon-sy" style="font-family: inherit; font-size: inherit !important; font-weight: inherit !important; height: inherit; line-height: inherit !important;">{</span><span class="crayon-h" style="font-family: inherit; font-size: inherit !important; font-weight: inherit !important; height: inherit; line-height: inherit !important;"> </span><span class="crayon-cn" style="font-family: inherit; font-size: inherit !important; font-weight: inherit !important; height: inherit; line-height: inherit !important;">192.168.1.0</span><span class="crayon-o" style="font-family: inherit; font-size: inherit !important; font-weight: inherit !important; height: inherit; line-height: inherit !important;">/</span><span class="crayon-cn" style="font-family: inherit; font-size: inherit !important; font-weight: inherit !important; height: inherit; line-height: inherit !important;">24</span><span class="crayon-sy" style="font-family: inherit; font-size: inherit !important; font-weight: inherit !important; height: inherit; line-height: inherit !important;">;</span><span class="crayon-h" style="font-family: inherit; font-size: inherit !important; font-weight: inherit !important; height: inherit; line-height: inherit !important;"> </span><span class="crayon-v" style="font-family: inherit; font-size: inherit !important; font-weight: inherit !important; height: inherit; line-height: inherit !important;">localhost</span><span class="crayon-sy" style="font-family: inherit; font-size: inherit !important; font-weight: inherit !important; height: inherit; line-height: inherit !important;">;</span><span class="crayon-h" style="font-family: inherit; font-size: inherit !important; font-weight: inherit !important; height: inherit; line-height: inherit !important;"> </span><span class="crayon-sy" style="font-family: inherit; font-size: inherit !important; font-weight: inherit !important; height: inherit; line-height: inherit !important;">}</span><span class="crayon-sy" style="font-family: inherit; font-size: inherit !important; font-weight: inherit !important; height: inherit; line-height: inherit !important;">;</span></div> <div class="crayon-line" id="crayon-55a9629c2715a059304565-3" style="background: 0px 50%; border: 0px; font-family: inherit; font-size: inherit !important; font-weight: inherit !important; height: inherit; line-height: inherit !important; margin: 0px; padding: 0px 5px;"> <span class="crayon-sy" style="font-family: inherit; font-size: inherit !important; font-weight: inherit !important; height: inherit; line-height: inherit !important;">}</span><span class="crayon-sy" style="font-family: inherit; font-size: inherit !important; font-weight: inherit !important; height: inherit; line-height: inherit !important;">;</span></div> <div class="crayon-line crayon-striped-line" id="crayon-55a9629c2715a059304565-4" style="background-attachment: initial !important; background-clip: initial !important; background-image: initial !important; background-origin: initial !important; background-position: initial !important; background-repeat: initial !important; background-size: initial !important; border: 0px; font-family: inherit; font-size: inherit !important; font-weight: inherit !important; height: inherit; line-height: inherit !important; margin: 0px; padding: 0px 5px;"> </div> <div class="crayon-line" id="crayon-55a9629c2715a059304565-5" style="background: 0px 50%; border: 0px; font-family: inherit; font-size: inherit !important; font-weight: inherit !important; height: inherit; line-height: inherit !important; margin: 0px; padding: 0px 5px;"> <span class="crayon-i" style="font-family: inherit; font-size: inherit !important; font-weight: inherit !important; height: inherit; line-height: inherit !important;">zone</span><span class="crayon-h" style="font-family: inherit; font-size: inherit !important; font-weight: inherit !important; height: inherit; line-height: inherit !important;"> </span><span class="crayon-s" style="font-family: inherit; font-size: inherit !important; font-weight: inherit !important; height: inherit; line-height: inherit !important;">"linuxgateway.fake"</span><span class="crayon-h" style="font-family: inherit; font-size: inherit !important; font-weight: inherit !important; height: inherit; line-height: inherit !important;"> </span><span class="crayon-sy" style="font-family: inherit; font-size: inherit !important; font-weight: inherit !important; height: inherit; line-height: inherit !important;">{</span></div> <div class="crayon-line crayon-striped-line" id="crayon-55a9629c2715a059304565-6" style="background-attachment: initial !important; background-clip: initial !important; background-image: initial !important; background-origin: initial !important; background-position: initial !important; background-repeat: initial !important; background-size: initial !important; border: 0px; font-family: inherit; font-size: inherit !important; font-weight: inherit !important; height: inherit; line-height: inherit !important; margin: 0px; padding: 0px 5px;"> <span class="crayon-h" style="font-family: inherit; font-size: inherit !important; font-weight: inherit !important; height: inherit; line-height: inherit !important;">      </span><span class="crayon-e" style="font-family: inherit; font-size: inherit !important; font-weight: inherit !important; height: inherit; line-height: inherit !important;">allow</span><span class="crayon-o" style="font-family: inherit; font-size: inherit !important; font-weight: inherit !important; height: inherit; line-height: inherit !important;">-</span><span class="crayon-e" style="font-family: inherit; font-size: inherit !important; font-weight: inherit !important; height: inherit; line-height: inherit !important;">query</span><span class="crayon-h" style="font-family: inherit; font-size: inherit !important; font-weight: inherit !important; height: inherit; line-height: inherit !important;"> </span><span class="crayon-sy" style="font-family: inherit; font-size: inherit !important; font-weight: inherit !important; height: inherit; line-height: inherit !important;">{</span><span class="crayon-h" style="font-family: inherit; font-size: inherit !important; font-weight: inherit !important; height: inherit; line-height: inherit !important;"> </span><span class="crayon-v" style="font-family: inherit; font-size: inherit !important; font-weight: inherit !important; height: inherit; line-height: inherit !important;">any</span><span class="crayon-sy" style="font-family: inherit; font-size: inherit !important; font-weight: inherit !important; height: inherit; line-height: inherit !important;">;</span><span class="crayon-h" style="font-family: inherit; font-size: inherit !important; font-weight: inherit !important; height: inherit; line-height: inherit !important;"> </span><span class="crayon-sy" style="font-family: inherit; font-size: inherit !important; font-weight: inherit !important; height: inherit; line-height: inherit !important;">}</span><span class="crayon-sy" style="font-family: inherit; font-size: inherit !important; font-weight: inherit !important; height: inherit; line-height: inherit !important;">;</span></div> <div class="crayon-line" id="crayon-55a9629c2715a059304565-7" style="background: 0px 50%; border: 0px; font-family: inherit; font-size: inherit !important; font-weight: inherit !important; height: inherit; line-height: inherit !important; margin: 0px; padding: 0px 5px;"> <span class="crayon-sy" style="font-family: inherit; font-size: inherit !important; font-weight: inherit !important; height: inherit; line-height: inherit !important;">}</span><span class="crayon-sy" style="font-family: inherit; font-size: inherit !important; font-weight: inherit !important; height: inherit; line-height: inherit !important;">;</span></div> <div class="crayon-line crayon-striped-line" id="crayon-55a9629c2715a059304565-8" style="background-attachment: initial !important; background-clip: initial !important; background-image: initial !important; background-origin: initial !important; background-position: initial !important; background-repeat: initial !important; background-size: initial !important; border: 0px; font-family: inherit; font-size: inherit !important; font-weight: inherit !important; height: inherit; line-height: inherit !important; margin: 0px; padding: 0px 5px;"> </div> <div class="crayon-line" id="crayon-55a9629c2715a059304565-9" style="background: 0px 50%; border: 0px; font-family: inherit; font-size: inherit !important; font-weight: inherit !important; height: inherit; line-height: inherit !important; margin: 0px; padding: 0px 5px;"> <span class="crayon-i" style="font-family: inherit; font-size: inherit !important; font-weight: inherit !important; height: inherit; line-height: inherit !important;">zone</span><span class="crayon-h" style="font-family: inherit; font-size: inherit !important; font-weight: inherit !important; height: inherit; line-height: inherit !important;"> </span><span class="crayon-s" style="font-family: inherit; font-size: inherit !important; font-weight: inherit !important; height: inherit; line-height: inherit !important;">"196.168.2.in-addr.arpa"</span><span class="crayon-h" style="font-family: inherit; font-size: inherit !important; font-weight: inherit !important; height: inherit; line-height: inherit !important;"> </span><span class="crayon-sy" style="font-family: inherit; font-size: inherit !important; font-weight: inherit !important; height: inherit; line-height: inherit !important;">{</span></div> <div class="crayon-line crayon-striped-line" id="crayon-55a9629c2715a059304565-10" style="background-attachment: initial !important; background-clip: initial !important; background-image: initial !important; background-origin: initial !important; background-position: initial !important; background-repeat: initial !important; background-size: initial !important; border: 0px; font-family: inherit; font-size: inherit !important; font-weight: inherit !important; height: inherit; line-height: inherit !important; margin: 0px; padding: 0px 5px;"> <span class="crayon-h" style="font-family: inherit; font-size: inherit !important; font-weight: inherit !important; height: inherit; line-height: inherit !important;">      </span><span class="crayon-e" style="font-family: inherit; font-size: inherit !important; font-weight: inherit !important; height: inherit; line-height: inherit !important;">allow</span><span class="crayon-o" style="font-family: inherit; font-size: inherit !important; font-weight: inherit !important; height: inherit; line-height: inherit !important;">-</span><span class="crayon-e" style="font-family: inherit; font-size: inherit !important; font-weight: inherit !important; height: inherit; line-height: inherit !important;">query</span><span class="crayon-h" style="font-family: inherit; font-size: inherit !important; font-weight: inherit !important; height: inherit; line-height: inherit !important;"> </span><span class="crayon-sy" style="font-family: inherit; font-size: inherit !important; font-weight: inherit !important; height: inherit; line-height: inherit !important;">{</span><span class="crayon-h" style="font-family: inherit; font-size: inherit !important; font-weight: inherit !important; height: inherit; line-height: inherit !important;"> </span><span class="crayon-v" style="font-family: inherit; font-size: inherit !important; font-weight: inherit !important; height: inherit; line-height: inherit !important;">any</span><span class="crayon-sy" style="font-family: inherit; font-size: inherit !important; font-weight: inherit !important; height: inherit; line-height: inherit !important;">;</span><span class="crayon-h" style="font-family: inherit; font-size: inherit !important; font-weight: inherit !important; height: inherit; line-height: inherit !important;"> </span><span class="crayon-sy" style="font-family: inherit; font-size: inherit !important; font-weight: inherit !important; height: inherit; line-height: inherit !important;">}</span><span class="crayon-sy" style="font-family: inherit; font-size: inherit !important; font-weight: inherit !important; height: inherit; line-height: inherit !important;">;</span></div> <div class="crayon-line" id="crayon-55a9629c2715a059304565-11" style="background: 0px 50%; border: 0px; font-family: inherit; font-size: inherit !important; font-weight: inherit !important; height: inherit; line-height: inherit !important; margin: 0px; padding: 0px 5px;"> <span class="crayon-sy" style="font-family: inherit; font-size: inherit !important; font-weight: inherit !important; height: inherit; line-height: inherit !important;">}</span><span class="crayon-sy" style="font-family: inherit; font-size: inherit !important; font-weight: inherit !important; height: inherit; line-height: inherit !important;">;</span></div> </div> </td></tr> </tbody></table> <hr style="border-bottom-color: rgb(255, 255, 255); border-bottom-style: solid; border-left-width: 0px; border-right-width: 0px; border-top-color: rgb(238, 238, 238); border-top-style: solid; color: #262626; font-family: 'PT Sans', sans-serif; font-size: 15px; line-height: 23px; margin: 21px 0px;" /> <h6 style="color: #222222; font-family: 'PT Sans', sans-serif; font-size: 22px; line-height: 28px; margin: 25px 0px 27px; text-rendering: optimizeLegibility;"> options { allow-recursion { 192.168.2.0/24; localhost; }; }; —————————————————–</h6> <div style="color: #262626; font-family: 'PT Sans', sans-serif; font-size: 15px; line-height: 23px; margin-bottom: 23px; position: relative; top: -9px;"> chroot jail</div> <div style="color: #262626; font-family: 'PT Sans', sans-serif; font-size: 15px; line-height: 23px; margin-bottom: 23px; position: relative; top: -9px;"> A “jail” is a software mechanism for limiting the ability of a process to access resources outside a very limited area, and it’s done with security in mind. A nameserver often talks to the outside world, and time has shown that “the public internet” is a very hostile environment. Should a flaw in BIND be discovered, it could be exploited by one located anywhere on the planet: by isolating the process inside a jail, this restricts the harm that can be done to a compromised system.</div> <div style="color: #262626; font-family: 'PT Sans', sans-serif; font-size: 15px; line-height: 23px; margin-bottom: 23px; position: relative; top: -9px;"> A jail is created using the chroot() system call (named for “change root”), and it’s given a directory name as a parameter. Once this call is made, the root – the top of the directory tree – for this process is changed from / to the directory given, and there is no way for the process to get outside this area. We typically use /chroot/named to jail our nameservers, but we’ll note that the “chroot” in the directory name is just a convention: this is not required (e.g., “/usr/local/named” would make a fine jail location too).</div> </div> </div> </div> </div> </div> </div>

Linux Security: OS & Service Level Security in Linux Part-2

Linux Security > OS & Service Level Security in Linux>Samba Server Samba Server: About Samba Server: Samba is an O...

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