6.7. Built-in System Access Control#

A system access control plugin enforces authorization at a global level, before any connector level authorization. You can use one of the built-in plugins in Presto, or provide your own by following the guidelines in System Access Control.

Multiple system access control implementations may be configured at once using the access-control.config-files configuration property. It should contain a comma separated list of the access control property files to use (rather than the default etc/access-control.properties).

Presto offers three built-in plugins:

Plugin Name Description
default (default value) All operations are permitted, except for user impersonation.
allow-all All operations are permitted.
read-only Operations that read data or metadata are permitted, but none of the operations that write data or metadata are allowed. See Read Only System Access Control for details.
file Authorization checks are enforced using a config file specified by the configuration property security.config-file. See File Based System Access Control for details.

Default System Access Control#

All operations are permitted, except for user impersonation. This plugin is enabled by default.

Allow All System Access Control#

All operations are permitted under this plugin.

Read Only System Access Control#

Under this plugin, you are allowed to execute any operation that reads data or metadata, such as SELECT or SHOW. Setting system level or catalog level session properties is also permitted. However, any operation that writes data or metadata, such as CREATE, INSERT or DELETE, is prohibited. To use this plugin, add an etc/access-control.properties file with the following contents:

access-control.name=read-only

File Based System Access Control#

This plugin allows you to specify access control rules in a file. To use this plugin, add an etc/access-control.properties file containing two required properties: access-control.name, which must be equal to file, and security.config-file, which must be equal to the location of the config file. For example, if a config file named rules.json resides in etc, add an etc/access-control.properties with the following contents:

access-control.name=file
security.config-file=etc/rules.json

The config file is specified in JSON format.

  • It contains the rules defining which catalog can be accessed by which user (see Catalog Rules below).
  • The query rules specifying which queries can be managed by which user (see Query Rules below).
  • The impersonation rules specify which user impersonations are allowed (see Impersonation Rules below).
  • The principal rules specifying what principals can identify as what users (see Principal Rules below).

This plugin currently supports catalog access, query, impersonation. and principal rules. If you want to limit access on a system level in any other way, you must implement a custom SystemAccessControl plugin (see System Access Control).

Refresh#

By default, when a change is made to the security.config-file, Presto must be restarted to load the changes. There is an optional property to refresh the properties without requiring a Presto restart. The refresh period is specified in the etc/access-control.properties:

security.refresh-period=1s

Catalog Rules#

These rules govern the catalogs particular users can access. The user is granted access to a catalog, based on the first matching rule read from top to bottom. If no rule matches, access is denied. Each rule is composed of the following fields:

  • user (optional): regex to match against user name. Defaults to .*.
  • group (optional): regex to match against group names. Defaults to .*.
  • catalog (optional): regex to match against catalog name. Defaults to .*.
  • allow (required): string indicating whether a user has access to the catalog. This value can be all, read-only or none, and defaults to none. Setting this value to read-only has the same behavior as the read-only system access control plugin.

In order for a rule to apply the user name must match the regular expression specified in user attribute.

For group names, a rule can be applied if at least one group name of this user matches the group regular expression.

Note

By default, all users have access to the system catalog. You can override this behavior by adding a rule.

Boolean true and false are also supported as legacy values for allow, to support backwards compatibility. true maps to all, and false maps to none.

For example, if you want to allow only the user admin to access the mysql and the system catalog, allow users from the finance and admin groups access to postgres catalog, allow all users to access the hive catalog, and deny all other access, you can use the following rules:

{
  "catalogs": [
    {
      "user": "admin",
      "catalog": "(mysql|system)",
      "allow": "all"
    },
    {
      "group": "finance|human_resources",
      "catalog": "postgres",
      "allow": true
    },
    {
      "catalog": "hive",
      "allow": "all"
    },
    {
      "user": "alice",
      "catalog": "postgresql",
      "allow": "read-only"
    },
    {
      "catalog": "system",
      "allow": "none"
    }
  ]
}

For group-based rules to match, users need to be assigned to groups by a Group Provider.

Query Rules#

These rules control the ability of a user to execute, view, or kill a query. The user is granted or denied access, based on the first matching rule read from top to bottom. If no rules are specified, all users are allowed to execute queries, and to view or kill queries owned by any user. If no rule matches, query management is denied. Each rule is composed of the following fields:

  • user (optional): regex to match against user name. Defaults to .*.
  • owner (optional): regex to match against the query owner name. Defaults to .*.
  • allow (required): set of query permissions granted to user. Values: execute, view, kill

Note

Users always have permission to view or kill their own queries.

For example, if you want to allow the user admin full query access, allow the user alice to execute and kill queries, any user to execute queries, and deny all other access, you can use the following rules:

{
  "catalogs": [
    {
      "allow": true
    }
  ],
  "queries": [
    {
      "user": "admin",
      "allow": ["execute", "kill", "view"]
    },
    {
      "user": "alice",
      "allow": ["execute", "kill"]
    },
    {
      "allow": ["execute"]
    }
  ]
}

Impersonation Rules#

These rules control the ability of a user to impersonate another user. In some environments it is desirable for an administrator (or managed system) to run queries on behalf of other users. In these cases, the administrator authenticates using their credentials, and then submits a query as a different user. When the user context is changed, Presto will verify the administrator is authorized to run queries as the target user.

When these rules are present, the authorization is based on the first matching rule, processed from top to bottom. If no rules match, the authorization is denied. If impersonation rules are not present but the legacy principal rules are specified, it is assumed impersonation access control is being handled by the principal rules, so impersonation is allowed. If neither impersonation nor principal rules are defined, impersonation is not allowed.

Each impersonation rule is composed of the following fields:

  • originalUser (required): regex to match against the user requesting the impersonation.
  • newUser (required): regex to match against the user that will be impersonated.
  • allow (optional): boolean indicating if the authentication should be allowed.

The following example allows the two admins, alice and bob, to impersonate any user, except they may not impersonate each other. It also allows any user to impersonate the test user:

{
    "catalogs": [
        {
            "allow": true
        }
    ],
    "impersonation": [
        {
            "originalUser": "alice",
            "newUser": "bob",
            "allow": false
        },
        {
            "originalUser": "bob",
            "newUser": "alice",
            "allow": false
        },
        {
            "originalUser": "alice|bob",
            "newUser": ".*"
        },
        {
            "originalUser": ".*",
            "newUser": "test"
        }
    ]
}

Principal Rules#

Warning

Principal rules are deprecated and will be removed in a future release. These rules have been replaced with User Mapping, which specifies how a complex authentication user name is mapped to a simple user name for Presto, and impersonation rules defined above.

These rules serve to enforce a specific matching between a principal and a specified user name. The principal is granted authorization as a user, based on the first matching rule read from top to bottom. If no rules are specified, no checks are performed. If no rule matches, user authorization is denied. Each rule is composed of the following fields:

  • principal (required): regex to match and group against principal.
  • user (optional): regex to match against user name. If matched, it will grant or deny the authorization based on the value of allow.
  • principal_to_user (optional): replacement string to substitute against principal. If the result of the substitution is same as the user name, it will grant or deny the authorization based on the value of allow.
  • allow (required): boolean indicating whether a principal can be authorized as a user.

Note

You would at least specify one criterion in a principal rule. If you specify both criteria in a principal rule, it returns the desired conclusion when either of criteria is satisfied.

The following implements an exact matching of the full principal name for LDAP and Kerberos authentication:

{
  "catalogs": [
    {
      "allow": true
    }
  ],
  "principals": [
    {
      "principal": "(.*)",
      "principal_to_user": "$1",
      "allow": true
    },
    {
      "principal": "([^/]+)(/.*)?@.*",
      "principal_to_user": "$1",
      "allow": true
    }
  ]
}

If you want to allow users to use the exact same name as their Kerberos principal name, and allow alice and bob to use a group principal named as group@example.net, you can use the following rules.

{
  "catalogs": [
    {
      "allow": true
    }
  ],
  "principals": [
    {
      "principal": "([^/]+)/?.*@example.net",
      "principal_to_user": "$1",
      "allow": true
    },
    {
      "principal": "group@example.net",
      "user": "alice|bob",
      "allow": true
    }
  ]
}