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Security Groups
---------------

About Security Groups
~~~~~~~~~~~~~~~~~~~~~

Security groups provide a way to isolate traffic to VMs. A security
group is a group of VMs that filter their incoming and outgoing traffic
according to a set of rules, called ingress and egress rules. These
rules filter network traffic according to the IP address that is
attempting to communicate with the VM. Security groups are particularly
useful in zones that use basic networking, because there is a single
guest network for all guest VMs. In advanced zones, security groups are
supported only on the KVM hypervisor.

.. note:: 
   In a zone that uses advanced networking, you can instead define 
   multiple guest networks to isolate traffic to VMs.

Each CloudStack account comes with a default security group that denies
all inbound traffic and allows all outbound traffic. The default
security group can be modified so that all new VMs inherit some other
desired set of rules.

Any CloudStack user can set up any number of additional security groups.
When a new VM is launched, it is assigned to the default security group
unless another user-defined security group is specified. A VM can be a
member of any number of security groups. Once a VM is assigned to a
security group, it remains in that group for its entire lifetime; you
can not move a running VM from one security group to another.

You can modify a security group by deleting or adding any number of
ingress and egress rules. When you do, the new rules apply to all VMs in
the group, whether running or stopped.

If no ingress rules are specified, then no traffic will be allowed in,
except for responses to any traffic that has been allowed out through an
egress rule.


Adding a Security Group
~~~~~~~~~~~~~~~~~~~~~~~

A user or administrator can define a new security group.

#. Log in to the CloudStack UI as an administrator or end user.

#. In the left navigation, choose Network.

#. In Select view, choose Security Groups.

#. Click Add Security Group.

#. Provide a name and description.

#. Click OK.

   The new security group appears in the Security Groups Details tab.

#. To make the security group useful, continue to Adding Ingress and
   Egress Rules to a Security Group.


Security Groups in Advanced Zones (KVM Only)
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

CloudStack provides the ability to use security groups to provide
isolation between guests on a single shared, zone-wide network in an
advanced zone where KVM is the hypervisor. Using security groups in
advanced zones rather than multiple VLANs allows a greater range of
options for setting up guest isolation in a cloud.

Setting for CentOS
^^^^^^^^^^^^^^^^^^

To use security groups on CentOS/RHEL/Fedora please enable bridge based
filtering, ensure that default sysctl configuration file usually at
/usr/lib/sysctl.d/00-system.conf set to following and run 'sysctl -p':

.. note::
   # Enable netfilter on bridges.
   net.bridge.bridge-nf-call-ip6tables = 1
   net.bridge.bridge-nf-call-iptables = 1
   net.bridge.bridge-nf-call-arptables = 1

Limitations
^^^^^^^^^^^

The following are not supported for this feature:

-  Two IP ranges with the same VLAN and different gateway or netmask in
   security group-enabled shared network.

-  Two IP ranges with the same VLAN and different gateway or netmask in
   account-specific shared networks.

-  Multiple VLAN ranges in security group-enabled shared network.

-  Multiple VLAN ranges in account-specific shared networks.

Security groups must be enabled in the zone in order for this feature to
be used.


Enabling Security Groups
~~~~~~~~~~~~~~~~~~~~~~~~

In order for security groups to function in a zone, the security groups
feature must first be enabled for the zone. The administrator can do
this when creating a new zone, by selecting a network offering that
includes security groups. The procedure is described in Basic Zone
Configuration in the Advanced Installation Guide. The administrator can
not enable security groups for an existing zone, only when creating a
new zone.


Adding Ingress and Egress Rules to a Security Group
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

#. Log in to the CloudStack UI as an administrator or end user.

#. In the left navigation, choose Network

#. In Select view, choose Security Groups, then click the security group
   you want.

#. To add an ingress rule, click the Ingress Rules tab and fill out the
   following fields to specify what network traffic is allowed into VM
   instances in this security group. If no ingress rules are specified,
   then no traffic will be allowed in, except for responses to any
   traffic that has been allowed out through an egress rule.

   -  **Add by CIDR/Account**. Indicate whether the source of the
      traffic will be defined by IP address (CIDR) or an existing
      security group in a CloudStack account (Account). Choose Account
      if you want to allow incoming traffic from all VMs in another
      security group

   -  **Protocol**. The networking protocol that sources will use to
      send traffic to the security group. TCP and UDP are typically used
      for data exchange and end-user communications. ICMP is typically
      used to send error messages or network monitoring data.

   -  **Start Port, End Port**. (TCP, UDP only) A range of listening
      ports that are the destination for the incoming traffic. If you
      are opening a single port, use the same number in both fields.

   -  **ICMP Type, ICMP Code**. (ICMP only) The type of message and
      error code that will be accepted.

   -  **CIDR**. (Add by CIDR only) To accept only traffic from IP
      addresses within a particular address block, enter a CIDR or a
      comma-separated list of CIDRs. The CIDR is the base IP address of
      the incoming traffic. For example, 192.168.0.0/22. To allow all
      CIDRs, set to 0.0.0.0/0.

   -  **Account, Security Group**. (Add by Account only) To accept only
      traffic from another security group, enter the CloudStack account
      and name of a security group that has already been defined in that
      account. To allow traffic between VMs within the security group
      you are editing now, enter the same name you used in step 7.

   The following example allows inbound HTTP access from anywhere:

   |httpaccess.png|

#. To add an egress rule, click the Egress Rules tab and fill out the
   following fields to specify what type of traffic is allowed to be
   sent out of VM instances in this security group. If no egress rules
   are specified, then all traffic will be allowed out. Once egress
   rules are specified, the following types of traffic are allowed out:
   traffic specified in egress rules; queries to DNS and DHCP servers;
   and responses to any traffic that has been allowed in through an
   ingress rule

   -  **Add by CIDR/Account**. Indicate whether the destination of the
      traffic will be defined by IP address (CIDR) or an existing
      security group in a CloudStack account (Account). Choose Account
      if you want to allow outgoing traffic to all VMs in another
      security group.

   -  **Protocol**. The networking protocol that VMs will use to send
      outgoing traffic. TCP and UDP are typically used for data exchange
      and end-user communications. ICMP is typically used to send error
      messages or network monitoring data.

   -  **Start Port, End Port**. (TCP, UDP only) A range of listening
      ports that are the destination for the outgoing traffic. If you
      are opening a single port, use the same number in both fields.

   -  **ICMP Type, ICMP Code**. (ICMP only) The type of message and
      error code that will be sent

   -  **CIDR**. (Add by CIDR only) To send traffic only to IP addresses
      within a particular address block, enter a CIDR or a
      comma-separated list of CIDRs. The CIDR is the base IP address of
      the destination. For example, 192.168.0.0/22. To allow all CIDRs,
      set to 0.0.0.0/0.

   -  **Account, Security Group**. (Add by Account only) To allow
      traffic to be sent to another security group, enter the CloudStack
      account and name of a security group that has already been defined
      in that account. To allow traffic between VMs within the security
      group you are editing now, enter its name.

#. Click Add.


.. |httpaccess.png| image:: /_static/images/http-access.png
   :alt: allows inbound HTTP access from anywhere.