nil pointer panic validating simple enum schema against invalid value

[mcottrell1]

I am trying to use the schema_validation module to validate against a schema containing a single string enum property. Validation succeeds when one of the enum values is provided, but instead of giving an error when validation fails there's a nil pointer panic.

Here's a full example:

package main

import (
	"fmt"

	"github.com/pb33f/libopenapi"
	validator "github.com/pb33f/libopenapi-validator"
	"github.com/pb33f/libopenapi-validator/schema_validation"
)

const yamlSchema = `
openapi: 3.1.0
info:
  version: v1
  title: test API
  description: test api
servers:
  - url: https://localhost/api/v1
    description: test api
components:
  schemas:
    Logging:
      properties:
        logLevel:
          type: string
          enum: [critical, error, info, debug]
`

func main() {
	doc, err := libopenapi.NewDocument([]byte(yamlSchema))
	if err != nil {
		panic(err)
	}

	docValidator, errs := validator.NewValidator(doc)
	if len(errs) > 0 {
		panic(errs)
	}
	valid, docErrors := docValidator.ValidateDocument()
	if !valid {
		fmt.Printf("document validation failed: %v\n", docErrors)
	}

	model, errs := doc.BuildV3Model()
	if len(errs) > 0 {
		panic(errs)
	}
	fmt.Println(model.Model.Components.Schemas)
	schemaProxy := model.Model.Components.Schemas["Logging"]
	schema := schemaProxy.Schema()
	low := schema.GoLow()
	fmt.Println(low.Type.KeyNode)

	validator := schema_validation.NewSchemaValidator()
	obj := map[string]interface{}{"logLevel": "invalid"}
	valid, errors := validator.ValidateSchemaObject(schema, obj)
	if !valid {
		fmt.Printf("schema validation failed: %v\n", errors)
	}
}

and the output:

map[Logging:0xc00011a300]
<nil>
panic: runtime error: invalid memory address or nil pointer dereference
[signal SIGSEGV: segmentation violation code=0x1 addr=0x88 pc=0x7802a4]

goroutine 1 [running]:
github.com/pb33f/libopenapi-validator/schema_validation.validateSchema(0xc0000b9b80, {0x0, 0x0, 0x0}, {0x7c9600, 0xc0003410e0}, 0xc0000ce000?)
	<path>/go/pkg/mod/github.com/pb33f/libopenapi-validator@v0.0.13/schema_validation/validate_schema.go:170 +0x524
github.com/pb33f/libopenapi-validator/schema_validation.(*schemaValidator).ValidateSchemaObject(0x7c9600?, 0xc0003410e0?, {0x7c9600?, 0xc0003410e0?})
	<path>/go/pkg/mod/github.com/pb33f/libopenapi-validator@v0.0.13/schema_validation/validate_schema.go:59 +0x36
main.main()
	<path>/main.go:56 +0x276
exit status 2

It appears that schema.GoLow().Type.KeyNode is nil and the code trying to add the error attempts to use it without a nil check. Is it expected that KeyNode should ever be nil?

[daveshanley]

This looks like a bug, but I can't be sure - I need to run this in my test-rig to see what the problem is. Thanks for finding this!

[daveshanley]

OK, so after looking at this, the issue lies with the assumption I made that all schemas put into the validator, will contain a type property, which is always required. Your test obj := map[string]interface{}{"logLevel": "invalid"} causes a panic, because it does not contain a type.

So the solution here is to not assume that the schema is even a schema. Because the Type property on the low-level object is always going to be nil unless that is set on the object passed in.

[daveshanley]

I will create a fix and publish a new version shortly.

[daveshanley]

fixed in v0.0.14

[mcottrell1]

thanks for the fix and explanation, Dave. I now see that adding type: object under Logging: in the schema avoids the panic (as does your fix, of course).