Restrict Depth Limit (#55)

* refactor: restrict depth limit of queries and mutations

* refactor: 10 limit instead of 20

* refactor: add docs for depth limit

README.md

@@ -114,6 +114,14 @@ Result
 </details>
 <hr/>
 
+## Restrict Query/Mutation depth
+
+Query/Mutation is restricted by default to 10.
+
+You can change the depth limit by setting the site config `frappe_graphql_depth_limit: 15`.
+
+<hr/>
+
 ## Subscriptions
 Get notified instantly of the updates via existing frappe's SocketIO. Please read more on the implementation details [here](./docs/subscriptions.md)
 <hr/>
@@ -223,7 +231,8 @@ def is_introspection_disabled():
     return not cint(frappe.local.conf.get("developer_mode")) and \
         not cint(frappe.local.conf.get("enable_introspection_in_production"))
 ```
-<hr>
+<hr/>
+
 ## Introspection in Production
 Introspection is disabled by default in production mode. You can enable by setting the site config `enable_introspection_in_production: 1`.
 

frappe_graphql/api.py

@@ -1,20 +1,35 @@
-from graphql import GraphQLError
+from graphql import GraphQLError, validate, parse
 from typing import List
 
 import frappe
+from frappe.utils import cint
+from . import get_schema
 from .graphql import execute
+from .utils.depth_limit_validator import depth_limit_validator
 
 from .utils.http import get_masked_variables, get_operation_name
 
 
 @frappe.whitelist(allow_guest=True)
 def execute_gql_query():
     query, variables, operation_name = get_query()
-    output = execute(
-        query=query,
-        variables=variables,
-        operation_name=operation_name
+    validation_errors = validate(
+        schema=get_schema(),
+        document_ast=parse(query),
+        rules=(
+            depth_limit_validator(
+                max_depth=cint(frappe.local.conf.get("frappe_graphql_depth_limit")) or 10
+            ),
+        )
     )
+    if validation_errors:
+        output = frappe._dict(errors=validation_errors)
+    else:
+        output = execute(
+            query=query,
+            variables=variables,
+            operation_name=operation_name
+        )
 
     frappe.clear_messages()
     frappe.local.response = output

frappe_graphql/utils/depth_limit_validator.py

@@ -0,0 +1,164 @@
+from frappe import _
+from graphql import (ValidationRule, ValidationContext, DefinitionNode, FragmentDefinitionNode, OperationDefinitionNode,
+                     Node, GraphQLError, FieldNode, InlineFragmentNode, FragmentSpreadNode)
+from typing import Optional, Union, Callable, Pattern, List, Dict
+
+IgnoreType = Union[Callable[[str], bool], Pattern, str]
+
+"""
+Copied from 
+https://github.com/graphql-python/graphene/blob/a61f0a214d4087acac097ab05f3969d77d0754b5/graphene/validation/depth_limit.py#L108
+"""
+
+
+def depth_limit_validator(
+    max_depth: int,
+    ignore: Optional[List[IgnoreType]] = None,
+    callback: Callable[[Dict[str, int]], None] = None,
+):
+    class DepthLimitValidator(ValidationRule):
+        def __init__(self, validation_context: ValidationContext):
+            document = validation_context.document
+            definitions = document.definitions
+
+            fragments = get_fragments(definitions)
+            queries = get_queries_and_mutations(definitions)
+            query_depths = {}
+
+            for name in queries:
+                query_depths[name] = determine_depth(
+                    node=queries[name],
+                    fragments=fragments,
+                    depth_so_far=0,
+                    max_depth=max_depth,
+                    context=validation_context,
+                    operation_name=name,
+                    ignore=ignore,
+                )
+            if callable(callback):
+                callback(query_depths)
+            super().__init__(validation_context)
+
+    return DepthLimitValidator
+
+
+def get_fragments(
+    definitions: List[DefinitionNode],
+) -> Dict[str, FragmentDefinitionNode]:
+    fragments = {}
+    for definition in definitions:
+        if isinstance(definition, FragmentDefinitionNode):
+            fragments[definition.name.value] = definition
+    return fragments
+
+
+# This will actually get both queries and mutations.
+# We can basically treat those the same
+def get_queries_and_mutations(
+    definitions: List[DefinitionNode],
+) -> Dict[str, OperationDefinitionNode]:
+    operations = {}
+
+    for definition in definitions:
+        if isinstance(definition, OperationDefinitionNode):
+            operation = definition.name.value if definition.name else "anonymous"
+            operations[operation] = definition
+    return operations
+
+
+def determine_depth(
+    node: Node,
+    fragments: Dict[str, FragmentDefinitionNode],
+    depth_so_far: int,
+    max_depth: int,
+    context: ValidationContext,
+    operation_name: str,
+    ignore: Optional[List[IgnoreType]] = None,
+) -> int:
+    if depth_so_far > max_depth:
+        context.report_error(
+            GraphQLError(
+                _("'{0}' exceeds maximum operation depth of {1}.").format(operation_name, max_depth),
+                [node],
+            )
+        )
+        return depth_so_far
+    if isinstance(node, FieldNode):
+        should_ignore = is_introspection_key(node.name.value) or is_ignored(
+            node, ignore
+        )
+
+        if should_ignore or not node.selection_set:
+            return 0
+        return 1 + max(
+            map(
+                lambda selection: determine_depth(
+                    node=selection,
+                    fragments=fragments,
+                    depth_so_far=depth_so_far + 1,
+                    max_depth=max_depth,
+                    context=context,
+                    operation_name=operation_name,
+                    ignore=ignore,
+                ),
+                node.selection_set.selections,
+            )
+        )
+    elif isinstance(node, FragmentSpreadNode):
+        return determine_depth(
+            node=fragments[node.name.value],
+            fragments=fragments,
+            depth_so_far=depth_so_far,
+            max_depth=max_depth,
+            context=context,
+            operation_name=operation_name,
+            ignore=ignore,
+        )
+    elif isinstance(
+        node, (InlineFragmentNode, FragmentDefinitionNode, OperationDefinitionNode)
+    ):
+        return max(
+            map(
+                lambda selection: determine_depth(
+                    node=selection,
+                    fragments=fragments,
+                    depth_so_far=depth_so_far,
+                    max_depth=max_depth,
+                    context=context,
+                    operation_name=operation_name,
+                    ignore=ignore,
+                ),
+                node.selection_set.selections,
+            )
+        )
+    else:
+        raise Exception(
+            _("Depth crawler cannot handle: {0}.").format(node.kind)
+        )
+
+
+def is_introspection_key(key):
+    # from: https://spec.graphql.org/June2018/#sec-Schema
+    # > All types and directives defined within a schema must not have a name which
+    # > begins with "__" (two underscores), as this is used exclusively
+    # > by GraphQL’s introspection system.
+    return str(key).startswith("__")
+
+
+def is_ignored(node: FieldNode, ignore: Optional[List[IgnoreType]] = None) -> bool:
+    if ignore is None:
+        return False
+    for rule in ignore:
+        field_name = node.name.value
+        if isinstance(rule, str):
+            if field_name == rule:
+                return True
+        elif isinstance(rule, Pattern):
+            if rule.match(field_name):
+                return True
+        elif callable(rule):
+            if rule(field_name):
+                return True
+        else:
+            raise ValueError(_("Invalid ignore option: {0}.").format(rule))
+    return False