Hack The Sec-Leading Resource Of Linux Tutorial: FileSystem

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<span style="color: #990000;"><u><i>Configure ACL in Linux FileSystem</i></u></span></h2>
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<span style="font-family: "georgia" , "times new roman" , serif;"><span style="border-image-outset: initial; border-image-repeat: initial; border-image-slice: initial; border-image-source: initial; border-image-width: initial; border: 0px; font-size: inherit; font-weight: 700; margin: 0px; outline: 0px; padding: 0px; vertical-align: baseline;">Ext3</span> and <span style="border-image-outset: initial; border-image-repeat: initial; border-image-slice: initial; border-image-source: initial; border-image-width: initial; border: 0px; font-size: inherit; font-weight: 700; margin: 0px; outline: 0px; padding: 0px; vertical-align: baseline;">Ext4</span> filesystem includes support of ACLs on files and directories. ACL provides more control permissions on file than standard three access categories (owner, group and other ). Using ACL you can provide permission to specific user or group to file.<br /></span></div>
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<a href="https://1.bp.blogspot.com/-zARXjIF1AjM/Vrl2c9mdDnI/AAAAAAAAAUY/5RL7sthZSMo/s1600/acls_map_ext_www.hackthesec.co.in.png" imageanchor="1" style="clear: left; float: left; margin-bottom: 1em; margin-right: 1em;"><img border="0" height="108" src="https://1.bp.blogspot.com/-zARXjIF1AjM/Vrl2c9mdDnI/AAAAAAAAAUY/5RL7sthZSMo/s320/acls_map_ext_www.hackthesec.co.in.png" width="320" /></a><span style="font-family: "georgia" , "times new roman" , serif;">Before working on <b>ACL </b>make sure that <b>ACL </b>is enabled on <b>mounted </b>file system. You can enable it during mounting filesystem with ACL option.</span></div>
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<span style="font-family: "georgia" , "times new roman" , serif;">Use following command Check if ACL is enabled on filesystem or not.</span></div>
<pre style="background: none 0px 0px repeat scroll rgb(60, 60, 60); border-radius: 4px; border: 1px solid rgb(229, 229, 229); line-height: 1.3em; margin-bottom: 20px; outline: 0px; overflow: auto; padding: 20px; vertical-align: baseline;"><span style="font-family: "courier new" , "courier" , monospace; font-size: large;"><span style="color: white;"># </span><span style="color: lime;">mount</span><span style="color: white;">

/dev/mapper/VolGroup00-LogVol00 on / type ext3 (</span><span style="color: lime;">rw,noatime,<span style="border-image-outset: initial; border-image-repeat: initial; border-image-slice: initial; border-image-source: initial; border-image-width: initial; border: 0px; font-weight: 700; margin: 0px; outline: 0px; padding: 0px; vertical-align: baseline;">acl</span></span><span style="color: white;">)</span></span><span style="color: white; font-size: 0.9em;">
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<span style="font-family: "georgia" , "times new roman" , serif;">Enable ACL by remounting file system using following command.</span></div>
<pre style="background: none 0px 0px repeat scroll rgb(60, 60, 60); border-radius: 4px; border: 1px solid rgb(229, 229, 229); line-height: 1.3em; margin-bottom: 20px; outline: 0px; overflow: auto; padding: 20px; vertical-align: baseline;"><span style="color: lime; font-family: "courier new" , "courier" , monospace; font-size: large;"># mount -o remount,acl  /
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<span style="font-family: "georgia" , "times new roman" , serif;">To enable ACL default on system bootup update following entry in <span style="color: #990000;">/etc/fstab</span> file.</span></div>
<pre style="background: none 0px 0px repeat scroll rgb(60, 60, 60); border-radius: 4px; border: 1px solid rgb(229, 229, 229); line-height: 1.3em; margin-bottom: 20px; outline: 0px; overflow: auto; padding: 20px; vertical-align: baseline;"><span style="font-family: "courier new" , "courier" , monospace; font-size: large;"><span style="color: white;">/dev/VolGroup00/LogVol00    /    ext3  defaults,</span><span style="color: lime;"><orange>acl</orange>  </span><span style="color: white;">1 1
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<span style="color: #0b5394;">Configure ACL on File</span></h4>
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<span style="font-family: "georgia" , "times new roman" , serif;">If we want that user Bob to have all permissions on a file. Use following command.</span></div>
<pre style="background: none 0px 0px repeat scroll rgb(60, 60, 60); border-radius: 4px; border: 1px solid rgb(229, 229, 229); line-height: 1.3em; margin-bottom: 20px; outline: 0px; overflow: auto; padding: 20px; vertical-align: baseline;"><span style="font-family: "courier new" , "courier" , monospace; font-size: large;"><span style="color: white;"># setfacl -m u:Bob:rwx </span><span style="color: lime;">hackthesec.txt</span><span style="color: white;">
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<span style="font-family: "georgia" , "times new roman" , serif;">Details of parameters:</span></div>
<pre style="background: none 0px 0px repeat scroll rgb(60, 60, 60); border-radius: 4px; border: 1px solid rgb(229, 229, 229); line-height: 1.3em; margin-bottom: 20px; outline: 0px; overflow: auto; padding: 20px; vertical-align: baseline;"><span style="font-family: "courier new" , "courier" , monospace; font-size: large;"><span style="color: lime;">setfacel</span><span style="color: white;">:  is a command itself
 -m : is used to modify ACL.
  u : it denotes to assign permission to a user
bob : a system user
</span><span style="color: lime;">rwx : file permissions.
</span><span style="color: white;">hackthesec.txt: file on which bob will get access.</span></span><span style="color: white; font-size: 0.9em;">
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<span style="color: #0b5394;">Check ACL on File</span></h4>
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<span style="font-family: "georgia" , "times new roman" , serif;">Use following command to check ACL configured on a file.</span></div>
<pre style="background: none 0px 0px repeat scroll rgb(60, 60, 60); border-radius: 4px; border: 1px solid rgb(229, 229, 229); line-height: 1.3em; margin-bottom: 20px; outline: 0px; overflow: auto; padding: 20px; vertical-align: baseline;"><span style="font-family: "courier new" , "courier" , monospace; font-size: large;"><span style="color: white;"># </span><span style="color: lime;">getfacl</span><span style="color: white;"> hackthesec.txt
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<span style="font-family: "georgia" , "times new roman" , serif;">Output:</span></div>
<pre style="background: none 0px 0px repeat scroll rgb(60, 60, 60); border-radius: 4px; border: 1px solid rgb(229, 229, 229); line-height: 1.3em; margin-bottom: 20px; outline: 0px; overflow: auto; padding: 20px; vertical-align: baseline;"><span style="font-family: "courier new" , "courier" , monospace; font-size: large;"><span style="color: white;"># file: hackthesec.txt
# owner: root
# group: root
user::rw-
</span><span style="color: lime;"><span style="border-image-outset: initial; border-image-repeat: initial; border-image-slice: initial; border-image-source: initial; border-image-width: initial; border: 0px; font-weight: 700; margin: 0px; outline: 0px; padding: 0px; vertical-align: baseline;">user:Bob:rwx</span>
</span><span style="color: white;">group::r--
mask::rwx
other::r--</span></span><span style="color: white; font-size: 0.9em;">
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<span style="color: #0b5394;">Remove ACL from File</span></h4>
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<span style="font-family: "georgia" , "times new roman" , serif;">If we don’t need the ACL in file, we can simply remove using following command.</span></div>
<pre style="background: none 0px 0px repeat scroll rgb(60, 60, 60); border-radius: 4px; border: 1px solid rgb(229, 229, 229); line-height: 1.3em; margin-bottom: 20px; outline: 0px; overflow: auto; padding: 20px; vertical-align: baseline;"><span style="font-family: "courier new" , "courier" , monospace; font-size: large;"><span style="color: white;"># </span><span style="color: lime;">setfacl -x u:Bob</span><span style="color: white;"> hackthesec.txt

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How to Configure ACL in Linux FileSystem

Configure ACL in Linux FileSystem Ext3 and Ext4 filesystem includes support of ACLs on files and directories. ACL provides more cont...