Schema/Metadata API Reference: Permissions¶

Table of contents

create_insert_permission
drop_insert_permission
create_select_permission
drop_select_permission
create_update_permission
drop_update_permission
create_delete_permission
drop_delete_permission
set_permission_comment

The permission layer is designed to restrict the operations that can be performed by various users. Permissions can be defined on various operations (insert/select/update/delete) at a role level granularity. By default, the admin role has unrestricted access to all operations.

Variables in rules

All X-Hasura-* header values can be used in the permission rules. These values can come with the request and can be validated using webhook or can be sent with the JWT token.

create_insert_permission¶

An insert permission is used to enforce constraints on the data that is being inserted.

Let’s look at an example, a permission for the user role to insert into the article table. What is the constraint that we would like to enforce here? A user can only insert articles for themselves .

POST /v1/query HTTP/1.1
Content-Type: application/json
X-Hasura-Role: admin

{
    "type" : "create_insert_permission",
    "args" : {
        "table" : "article",
        "role" : "user",
        "permission" : {
            "check" : {
                "author_id" : "X-HASURA-USER-ID"
            },
            "set":{
                "id":"X-HASURA-USER-ID"
            },
            "columns":["name","author_id"]
        }
    }
}

This reads as follows - for the user role:

For every row that is being inserted into the article table, allow insert only if the check passes i.e. that the author_id column value is the same as the value in the request header X-HASURA-USER-ID”.
If the above check passes, then access for insert will be limited to columns name and author_id only.
When this insert happens, the value of the column id will be automatically set to the value of the resolved session variable X-HASURA-USER-ID.

The argument for check is a boolean expression which has the same syntax as the where clause in the select query, making it extremely expressive.

An example:

POST /v1/query HTTP/1.1
Content-Type: application/json
X-Hasura-Role: admin

{
    "type" : "create_insert_permission",
    "args" : {
        "table" : "article",
        "role" : "user",
        "permission" : {
            "check" : {
                "author_id" : "X-HASURA-USER-ID",
                "$or" : [
                    {
                        "category" : "editorial",
                        "is_reviewed" : false
                    },
                    {
                        "category" : { "$neq" : "editorial"}
                    }
                ]
            }
        }
    }
}

In the above definition, the row is allowed to be inserted if the author_id is the same as the request’s user id and is_reviewed is false when the category is “editorial”.

Args syntax¶

Key	Required	Schema	Description
table	true	TableName	Name of the table
role	true	RoleName	Role
permission	true	InsertPermission	The permission definition
comment	false	text	Comment

InsertPermission¶

Key	Required	Schema	Description
check	true	BoolExp	This expression has to hold true for every new row that is inserted
set	false	ColumnPresetsExp	Preset values for columns that can be sourced from session variables or static values
columns	false	PGColumn array (or) `'*'`	Can insert into only these columns (or all when `'*'` is specified)
backend_only	false	Boolean	When set to `true` the mutation is accessible only if `x-hasura-use-backend-only-permissions` session variable exists and is set to `true` and request is made with `x-hasura-admin-secret` set if any auth is configured

drop_insert_permission¶

The drop_insert_permission API is used to drop an existing insert permission for a role on a table.

An example:

POST /v1/query HTTP/1.1
Content-Type: application/json
X-Hasura-Role: admin

{
    "type" : "drop_insert_permission",
    "args" : {
        "table" : "article",
        "role" : "user"
    }
}

Args syntax¶

Key	Required	Schema	Description
table	true	TableName	Name of the table
role	true	RoleName	Role

create_select_permission¶

A select permission is used to restrict access to only the specified columns and rows.

Let’s look at an example, a permission for the user role to select from the article table: all columns can be read, as well as the rows that have been published or authored by the user themselves.

POST /v1/query HTTP/1.1
Content-Type: application/json
X-Hasura-Role: admin

{
    "type" : "create_select_permission",
    "args" : {
        "table" : "article",
        "role" : "user",
        "permission" : {
            "columns" : "*",
            "filter" : {
                "$or" : [
                    { "author_id" : "X-HASURA-USER-ID" },
                    { "is_published" : true }
                ]
             },
             "limit": 10,
             "allow_aggregations": true
        }
    }
}

This reads as follows - For the user role:

Allow selecting rows where the check passes i.e. is_published is true or the author_id matches the value of the session variable X-HASURA-USER-ID.
Allow selecting all columns (because the columns key is set to *).
limit the numbers of rows returned by a query to the article table by the user role to a maximum of 10.
Allow aggregate queries.

Args syntax¶

Key	Required	Schema	Description
table	true	TableName	Name of the table
role	true	RoleName	Role
permission	true	SelectPermission	The permission definition
comment	false	text	Comment

SelectPermission¶

Key	Required	Schema	Description
columns	true	PGColumn array (or) `'*'`	Only these columns are selectable (or all when `'*'` is specified)
computed_fields	false	ComputedFieldName array	Only these computed fields are selectable
filter	true	BoolExp	Only the rows where this expression holds true are selectable
limit	false	`Integer`	The maximum number of rows that can be returned
allow_aggregations	false	`Boolean`	Toggle allowing aggregate queries

drop_select_permission¶

The drop_select_permission is used to drop an existing select permission for a role on a table.

An example:

POST /v1/query HTTP/1.1
Content-Type: application/json
X-Hasura-Role: admin

{
    "type" : "drop_select_permission",
    "args" : {
        "table" : "article",
        "role" : "user"
    }
}

Args syntax¶

Key	Required	Schema	Description
table	true	TableName	Name of the table
role	true	RoleName	Role

create_update_permission¶

An update permission is used to restrict the columns and rows that can be updated. Its structure is quite similar to the select permission.

An example:

POST /v1/query HTTP/1.1
Content-Type: application/json
X-Hasura-Role: admin

{
    "type" : "create_update_permission",
    "args" : {
        "table" : "article",
        "role" : "user",
        "permission" : {
            "columns" : ["title", "content", "category"],
            "filter" : {
                "author_id" : "X-HASURA-USER-ID"
            },
            "check" : {
                "content" : {
                  "_ne": ""
                }
            },
            "set":{
                "updated_at" : "NOW()"
            }
        }
    }
}

This reads as follows - for the user role:

Allow updating only those rows where the filter passes i.e. the value of the author_id column of a row matches the value of the session variable X-HASURA-USER-ID.
If the above filter passes for a given row, allow updating only the title, content and category columns (as specified in the columns key).
After the update happens, verify that the check condition holds for the updated row i.e. that the value in the content column is not empty.
When this update happens, the value of the column updated_at will be automatically set to the current timestamp.

Note

It is important to deny updates to columns that will determine the row ownership. In the above example, the author_id column determines the ownership of a row in the article table. Columns such as this should never be allowed to be updated.

Args syntax¶

Key	Required	Schema	Description
table	true	TableName	Name of the table
role	true	RoleName	Role
permission	true	UpdatePermission	The permission definition
comment	false	text	Comment

UpdatePermission¶

Key	Required	Schema	Description
columns	true	PGColumn array (or) `'*'`	Only these columns are selectable (or all when `'*'` is specified)
filter	true	BoolExp	Only the rows where this precondition holds true are updatable
check	false	BoolExp	Postcondition which must be satisfied by rows which have been updated
set	false	ColumnPresetsExp	Preset values for columns that can be sourced from session variables or static values.

drop_update_permission¶

The drop_update_permission API is used to drop an existing update permission for a role on a table.

An example:

POST /v1/query HTTP/1.1
Content-Type: application/json
X-Hasura-Role: admin

{
    "type" : "drop_update_permission",
    "args" : {
        "table" : "article",
        "role" : "user"
    }
}

Args syntax¶

Key	Required	Schema	Description
table	true	TableName	Name of the table
role	true	RoleName	Role

create_delete_permission¶

A delete permission is used to restrict the rows that can be deleted.

An example:

POST /v1/query HTTP/1.1
Content-Type: application/json
X-Hasura-Role: admin

{
    "type" : "create_delete_permission",
    "args" : {
        "table" : "article",
        "role" : "user",
        "permission" : {
            "filter" : {
                "author_id" : "X-HASURA-USER-ID"
            }
        }
    }
}

This reads as follows:

“delete for the user role on the article table is allowed on rows where author_id is the same as the request header X-HASURA-USER-ID value.”

Args syntax¶

Key	Required	Schema	Description
table	true	TableName	Name of the table
role	true	RoleName	Role
permission	true	DeletePermission	The permission definition
comment	false	text	Comment

DeletePermission¶

Key	Required	Schema	Description
filter	true	BoolExp	Only the rows where this expression holds true are deletable

drop_delete_permission¶

The drop_delete_permission API is used to drop an existing delete permission for a role on a table.

An example:

POST /v1/query HTTP/1.1
Content-Type: application/json
X-Hasura-Role: admin

{
    "type" : "drop_delete_permission",
    "args" : {
        "table" : "article",
        "role" : "user"
    }
}

Args syntax¶

Key	Required	Schema	Description
table	true	TableName	Name of the table
role	true	RoleName	Role

set_permission_comment¶

set_permission_comment is used to set/update the comment on a permission. Setting the comment to null removes it.

An example:

POST /v1/query HTTP/1.1
Content-Type: application/json
Authorization: Bearer <auth-token> # optional if cookie is set
X-Hasura-Role: admin

{
    "type": "set_permission_comment",
    "args": {
        "table": "article",
        "role": "user",
        "type" : "update",
        "comment" : "can only modify his/her own rows"
    }
}

Args syntax¶

Key	Required	Schema	Description
table	true	TableName	Name of the table
role	true	RoleName	The role in the permission
type	true	permission type (one of select/update/delete/insert)	The type of the permission
comment	false	Text	Comment

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