Configure a security context for an elastic container instance or a container - Elastic Container Instance

This topic describes how to configure a security context and define permissions and access control settings for an elastic container instance or a container.

Background information

Security contexts define permissions and access control settings for elastic container instances or containers. Examples of security context settings include Discretionary Access Control, Security Enhanced Linux (SELinux), and Linux Capabilities. For more information, see Configure a Security Context for a Pod or Container.

You can configure security contexts at the following levels:

Instances
Elastic Container Instance allows you to modify sysctl parameters by configuring a security context for an instance. The security settings that you specify for an instance apply to all containers and volumes in the instance.
Containers
Elastic Container Instance allows you to modify the runAsUser and capabilities parameters by configuring a security context for a container. The security settings that you specify for a container apply only to the specified container.

Configure a security context for an instance

Feature description

In a Linux system, you can modify runtime kernel parameters by using the sysctl interface. You can view the kernel parameters of an elastic container instance by running the following command. For more information, see sysctl.sh.

sysctl -a

You can modify the sysctl and runAsUser parameters by configuring a security context for a pod.

Warning

To avoid instability in the operating system, you must fully understand the impacts of sysctl parameter modifications before you proceed. For more information, see sysctl.

The following sysctl parameters can be modified in Elastic Container Instance:

kernel.shm * (except kernel.shm_rmid_forced)
kernel.msg*
kernel.sem
fs.mqueue.*
net.* (except net.ipv4.tcp_syncookies)
vm.min_free_kbytes
We recommend that you specify a value for vm.min_free_kbytes that is not greater than 20% of the total memory size.

Configuration description

When you call the CreateContainerGroup API operation to create an elastic container instance, you can use SecurityContext.Sysctl-related parameters or HostSecurityContext.Sysctl-related parameters to configure a security context for the instance. SecurityContext.Sysctl-related parameters are used to modify safe sysctls, and HostSecurityContext.Sysctl-related parameters are used to modify unsafe sysctls. The following table describes the relevant parameters. For more information, see CreateContainerGroup.

Parameter	Type	Example	Description
SecurityContext.Sysctl.N.Name	string	net.ipv4.ping_group_range	The name of the safe sysctl when you modify sysctls by configuring a security context. Valid values: net.ipv4.ping_group_range net.ipv4.ip_unprivileged_port_start
SecurityContext.Sysctl.N.Value	string	1	The value of the safe sysctl when you modify sysctls by configuring a security context.
HostSecurityContext.Sysctl.N.Name	string	kernel.msgmax	The name of the unsafe sysctl when you modify sysctls by configuring a security context. Valid values: kernel.shm * (except kernel.shm_rmid_forced) kernel.msg* kernel.sem fs.mqueue.* net.*(except net.ipv4.ip_local_port_range, net.ipv4.tcp_syncookies, net.ipv4.ping_group_range, and net.ipv4.ip_unprivileged_port_start)
HostSecurityContext.Sysctl.N.Value	string	65536	The value of the unsafe sysctl when you modify sysctls by configuring a security context.

Configure a security context for a container

Feature description

You can configure a security context for a specified container. The following table describes the parameters supported by Elastic Container Instance.

Parameter	Description
runAsUser	The ID of the user who runs the container. The parameter settings override the USER command in the Dockerfile.
runAsGroup	The user group that runs the container.
runAsNonRoot	Specifies whether the user runs the container as a non-root user.
capabilities	The permissions that are granted to processes in the container. For more information, see Linux capabilities. You can configure the following permissions: AUDIT_WRITE CHOWN DAC_OVERRIDE FSETID FOWNER KILL MKNOD NET_ADMIN NET_BIND_SERVICE NET_RAW SETGID SETUID SETFCAP SETPCAP SYS_CHROOT SYS_PTRACE SYS_RAWIO Note You cannot grant the SYS_RAWIO permission to processes. To use SYS_RAWIO, submit a ticket.

The following table describes some parameters that are not supported and the default values of the parameters.

Parameter	Description
privileged	Specifies whether to run the container in privileged mode. Default value: false.
AllowedProcMountTypes	The allowed proc mount types for the container. Default value: DefaultProcMount.
readOnlyRootFilesystem	Species whether the root file system that the container runs is read-only. Default value: true.

Configuration description

When you call the CreateContainerGroup API operation to create an elastic container instance, you can use Container.N.SecurityContext-related parameters to configure a security context for the container. The following table describes the relevant parameters. For more information, see CreateContainerGroup.

Parameter	Type	Example	Description
Container.N.SecurityContext.Capability.Add.N	array	NET_ADMIN	The permissions that you want to grant to the processes in the container.
Container.N.SecurityContext.ReadOnlyRootFilesystem	boolean	true	Specifies whether the root file system on which the container runs is read-only. Set the value to true.
Container.N.SecurityContext.RunAsUser	long	1000	The ID of the user that runs the container.
Container.N.SecurityContextRunAsGroup	long	3000	The user group that runs the container.
Container.N.SecurityContextRunAsNonRoot	boolean	true	Specifies whether to run the container as a non-root user.

Note

You can also configure security contexts for init containers. The parameters that you need to configure are similar to the parameters in the preceding table, but you cannot not configure the SecurityContextRunAsGroup and SecurityContextRunAsNonRoot parameters for init containers.