blob: 91c7af3faecb833d6b83a635d077aa7a4ef250c6 [file] [log] [blame]
// Package auth defines a standard interface for request access controllers.
//
// An access controller has a simple interface with a single `Authorized`
// method which checks that a given request is authorized to perform one or
// more actions on one or more resources. This method should return a non-nil
// error if the request is not authorized.
//
// An implementation registers its access controller by name with a constructor
// which accepts an options map for configuring the access controller.
//
// options := map[string]interface{}{"sillySecret": "whysosilly?"}
// accessController, _ := auth.GetAccessController("silly", options)
//
// This `accessController` can then be used in a request handler like so:
//
// func updateOrder(w http.ResponseWriter, r *http.Request) {
// orderNumber := r.FormValue("orderNumber")
// resource := auth.Resource{Type: "customerOrder", Name: orderNumber}
// access := auth.Access{Resource: resource, Action: "update"}
//
// if ctx, err := accessController.Authorized(ctx, access); err != nil {
// if challenge, ok := err.(auth.Challenge) {
// // Let the challenge write the response.
// challenge.SetHeaders(w)
// w.WriteHeader(http.StatusUnauthorized)
// return
// } else {
// // Some other error.
// }
// }
// }
//
package auth
import (
"context"
"errors"
"fmt"
"net/http"
)
const (
// UserKey is used to get the user object from
// a user context
UserKey = "auth.user"
// UserNameKey is used to get the user name from
// a user context
UserNameKey = "auth.user.name"
)
var (
// ErrInvalidCredential is returned when the auth token does not authenticate correctly.
ErrInvalidCredential = errors.New("invalid authorization credential")
// ErrAuthenticationFailure returned when authentication fails.
ErrAuthenticationFailure = errors.New("authentication failure")
)
// UserInfo carries information about
// an autenticated/authorized client.
type UserInfo struct {
Name string
}
// Resource describes a resource by type and name.
type Resource struct {
Type string
Class string
Name string
}
// Access describes a specific action that is
// requested or allowed for a given resource.
type Access struct {
Resource
Action string
}
// Challenge is a special error type which is used for HTTP 401 Unauthorized
// responses and is able to write the response with WWW-Authenticate challenge
// header values based on the error.
type Challenge interface {
error
// SetHeaders prepares the request to conduct a challenge response by
// adding the an HTTP challenge header on the response message. Callers
// are expected to set the appropriate HTTP status code (e.g. 401)
// themselves.
SetHeaders(w http.ResponseWriter)
}
// AccessController controls access to registry resources based on a request
// and required access levels for a request. Implementations can support both
// complete denial and http authorization challenges.
type AccessController interface {
// Authorized returns a non-nil error if the context is granted access and
// returns a new authorized context. If one or more Access structs are
// provided, the requested access will be compared with what is available
// to the context. The given context will contain a "http.request" key with
// a `*http.Request` value. If the error is non-nil, access should always
// be denied. The error may be of type Challenge, in which case the caller
// may have the Challenge handle the request or choose what action to take
// based on the Challenge header or response status. The returned context
// object should have a "auth.user" value set to a UserInfo struct.
Authorized(ctx context.Context, access ...Access) (context.Context, error)
}
// CredentialAuthenticator is an object which is able to authenticate credentials
type CredentialAuthenticator interface {
AuthenticateUser(username, password string) error
}
// WithUser returns a context with the authorized user info.
func WithUser(ctx context.Context, user UserInfo) context.Context {
return userInfoContext{
Context: ctx,
user: user,
}
}
type userInfoContext struct {
context.Context
user UserInfo
}
func (uic userInfoContext) Value(key interface{}) interface{} {
switch key {
case UserKey:
return uic.user
case UserNameKey:
return uic.user.Name
}
return uic.Context.Value(key)
}
// WithResources returns a context with the authorized resources.
func WithResources(ctx context.Context, resources []Resource) context.Context {
return resourceContext{
Context: ctx,
resources: resources,
}
}
type resourceContext struct {
context.Context
resources []Resource
}
type resourceKey struct{}
func (rc resourceContext) Value(key interface{}) interface{} {
if key == (resourceKey{}) {
return rc.resources
}
return rc.Context.Value(key)
}
// AuthorizedResources returns the list of resources which have
// been authorized for this request.
func AuthorizedResources(ctx context.Context) []Resource {
if resources, ok := ctx.Value(resourceKey{}).([]Resource); ok {
return resources
}
return nil
}
// InitFunc is the type of an AccessController factory function and is used
// to register the constructor for different AccesController backends.
type InitFunc func(options map[string]interface{}) (AccessController, error)
var accessControllers map[string]InitFunc
func init() {
accessControllers = make(map[string]InitFunc)
}
// Register is used to register an InitFunc for
// an AccessController backend with the given name.
func Register(name string, initFunc InitFunc) error {
if _, exists := accessControllers[name]; exists {
return fmt.Errorf("name already registered: %s", name)
}
accessControllers[name] = initFunc
return nil
}
// GetAccessController constructs an AccessController
// with the given options using the named backend.
func GetAccessController(name string, options map[string]interface{}) (AccessController, error) {
if initFunc, exists := accessControllers[name]; exists {
return initFunc(options)
}
return nil, fmt.Errorf("no access controller registered with name: %s", name)
}