ip_allow.yaml

The ip_allow.yaml file controls client access to Traffic Server and Traffic Server connections to upstream servers. This control is specified rules. Each rule has

  • A direction (inbound or out).

  • A range of IP address to which the rule applies.

  • An action, either accept or deny.

  • A list of HTTP methods.

Inbound rules control access to Traffic Server from user agents. Outbound rules control access to upstream destinations from Traffic Server. The IP addresses always apply to the remote address for Traffic Server. That is, the user agent IP address for inbound rules and the upstream destination address for outbound rules. The rule can apply at the connection level or just to specific methods.

Traffic Server can be updated for changes to the rules in ip_allow.yaml file, by running the traffic_ctl config reload.

Format

ip_allow.yaml is YAML format. The default configuration is:

# YAML
ip_allow:
  - apply: in
    ip_addrs: 127.0.0.1
    action: allow
    methods: ALL
  - apply: in
    ip_addrs: ::1
    action: allow
    methods: ALL
  - apply: in
    ip_addrs: 0/0
    action: deny
    methods:
      - PURGE
      - PUSH
      - DELETE
  - apply: in
    ip_addrs: ::/0
    action: deny
    methods:
      - PURGE
      - PUSH
      - DELETE

Each rule is a mapping. The YAML data must have a top level key of “ip_allow” and its value must be a mapping or a sequence of mappings, each of those being one rule.

The keys in a rule are

apply

This is where the rule is applied, either in or out. Inbound application means the rule is applied to inbound user agent connections. Outbound application means the rule is applied to outbound connections from Traffic Server to an upstream destination. This is a required key.

ip_addrs

IP addresses to match for the rule to be applied. This can be either an address range or an array of address ranges. This is a required key.

action

The action, which must be allow or deny. This is a required key.

methods

This is optional. If not present, the rule action applies to all methods. If present, the rule action is applied connections using those methods and its opposite to all other connections. The keyword “ALL” means all methods, making the specification of any other method redundant. All methods comparisons are case insensitive. This is an optional key.

An IP address range can be specified in several ways. A range is always IPv4 or IPv6, it is not allowed to have a range that contains addresses from different IP address families.

  • A single address, which specifies a range of size 1, e.g. “127.0.0.1”.

  • A minimum and maximum address separated by a dash, e.g. “10.1.0.0-10.1.255.255”.

  • A CIDR based value, e.g. “10.1.0.0/16”, which is a range containing exactly the specified network.

A rule must have the apply, ip_addrs, and action keys. Rules match based on IP addresses only, and are then applied to all matching sessions. If the rule is an allow rule, the specified methods are allowed and all other methods are denied. If the rule is a deny rule, the specified methods are denied and all other methods are allowed.

For example, from the default configuration, the rule for 127.0.0.1 is allow with all methods. Therefore an inbound connection from the loopback address (127.0.0.1) is allowed to use any method. The general IPv4 rule, covering all IPv4 address, is a deny rule and therefore when it matches the methods “PURGE”, “PUSH”, and “DELETE” are denied, any other method is allowed.

The rules are matched in order, by IP address, therefore the general IPv4 rule does not apply to the loopback address because the latter is matched first.

A major difference in application between in and out rules is that by default, inbound connections are denied and therefore if there is no rule that matches, the connection is denied. Outbound rules allow by default, so the absence of rules in the default configuration enables all methods for all outbound connections.

Examples

The following example enables all clients access.:

apply: in
ip_addrs: 0.0.0.0-255.255.255.255
action: allow

The following example allows access to all clients on addresses in a subnet:

apply: in
ip_addrs: 123.12.3.000-123.12.3.123
action: allow

The following example denies access all clients on addresses in a subnet:

apply: in
ip_addrs: 123.45.6.0-123.45.6.123
action: deny

If the entire subnet were to be denied, that would be:

apply: in
ip_addrs: 123.45.6.0/24
action: deny

The following example allows any method to any upstream servers:

apply: out
ip_addrs: 0.0.0.0-255.255.255.255
action: allow

Alternatively this can be done with:

apply: out
ip_addrs: 0/0
action: allow

Or also by having no rules at all, as outbound by default is allow.

The following example denies to access all servers on a specific subnet:

apply: out
ip_addr: 10.0.0.0-10.0.255.255
action: deny

Alternatively:

apply: out
ip_addrs: 10.0.0.0/16
action: deny

The ip_addrs can be an array of ranges, so that:

- apply: in
  ip_addrs: 10.0.0.0/8
  action: deny
- apply: in
  ip_addrs: 172.16.0.0/20
  action: deny
- apply: in
  ip_addrs: 192.168.1.0/24
  action: deny

can be done more simply as:

apply: in
ip_addrs:
  - 10.0.0.0/8
  - 172.16.0.0/20
  - 192.168.1.0/24
action: deny

If the goal is to allow only GET and HEAD requests to those servers, it would be:

apply: out
ip_addrs: 10.0.0.0/16
methods: [ GET, HEAD ]
action: allow

Alternatively:

apply: out
ip_addrs: 10.0.0.0/16
methods:
- GET
- HEAD
action: allow

This will match the IP address for the target servers on the outbound connection. Then, if the method is GET or HEAD the connection will be allowed, otherwise the connection will be denied.

As a final example, here is the default configuration in compact form:

ip_allow: [
  { apply: in, ip_addrs: 127.0.0.1, action: allow },
  { apply: in, ip_addrs: "::1", action: allow },
  { apply: in, ip_addrs: 0/0, action: deny, methods: [ PURGE, PUSH, DELETE ] },
  { apply: in, ip_addrs: "::/0", action: deny, methods: [ PURGE, PUSH, DELETE ] }
  ]

Note

For ATS 9.0, this file is (almost) backwards compatible. If the first line is a single ‘#’ character, or contains only “# ats”, then the file will be read in the version 8.0 format. This is true for the default format and so if that has not been changed it should still work. This allows a grace period before ATS 10.0 which will drop the old format entirely.