forked from TrueCloudLab/distribution
142 lines
4.7 KiB
Go
142 lines
4.7 KiB
Go
// Package auth defines a standard interface for request access controllers.
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//
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// An access controller has a simple interface with a single `Authorized`
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// method which checks that a given request is authorized to perform one or
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// more actions on one or more resources. This method should return a non-nil
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// error if the requset is not authorized.
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//
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// An implementation registers its access controller by name with a constructor
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// which accepts an options map for configuring the access controller.
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//
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// options := map[string]interface{}{"sillySecret": "whysosilly?"}
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// accessController, _ := auth.GetAccessController("silly", options)
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//
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// This `accessController` can then be used in a request handler like so:
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//
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// func updateOrder(w http.ResponseWriter, r *http.Request) {
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// orderNumber := r.FormValue("orderNumber")
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// resource := auth.Resource{Type: "customerOrder", Name: orderNumber}
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// access := auth.Access{Resource: resource, Action: "update"}
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//
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// if ctx, err := accessController.Authorized(ctx, access); err != nil {
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// if challenge, ok := err.(auth.Challenge) {
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// // Let the challenge write the response.
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// challenge.ServeHTTP(w, r)
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// } else {
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// // Some other error.
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// }
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// }
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// }
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//
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package auth
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import (
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"fmt"
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"net/http"
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"golang.org/x/net/context"
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)
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// UserInfo carries information about
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// an autenticated/authorized client.
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type UserInfo struct {
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Name string
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}
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// Resource describes a resource by type and name.
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type Resource struct {
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Type string
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Name string
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}
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// Access describes a specific action that is
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// requested or allowed for a given recource.
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type Access struct {
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Resource
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Action string
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}
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// Challenge is a special error type which is used for HTTP 401 Unauthorized
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// responses and is able to write the response with WWW-Authenticate challenge
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// header values based on the error.
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type Challenge interface {
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error
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// ServeHTTP prepares the request to conduct the appropriate challenge
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// response. For most implementations, simply calling ServeHTTP should be
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// sufficient. Because no body is written, users may write a custom body after
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// calling ServeHTTP, but any headers must be written before the call and may
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// be overwritten.
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ServeHTTP(w http.ResponseWriter, r *http.Request)
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}
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// AccessController controls access to registry resources based on a request
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// and required access levels for a request. Implementations can support both
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// complete denial and http authorization challenges.
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type AccessController interface {
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// Authorized returns a non-nil error if the context is granted access and
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// returns a new authorized context. If one or more Access structs are
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// provided, the requested access will be compared with what is available
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// to the context. The given context will contain a "http.request" key with
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// a `*http.Request` value. If the error is non-nil, access should always
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// be denied. The error may be of type Challenge, in which case the caller
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// may have the Challenge handle the request or choose what action to take
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// based on the Challenge header or response status. The returned context
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// object should have a "auth.user" value set to a UserInfo struct.
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Authorized(ctx context.Context, access ...Access) (context.Context, error)
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}
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// WithUser returns a context with the authorized user info.
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func WithUser(ctx context.Context, user UserInfo) context.Context {
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return userInfoContext{
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Context: ctx,
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user: user,
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}
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}
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type userInfoContext struct {
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context.Context
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user UserInfo
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}
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func (uic userInfoContext) Value(key interface{}) interface{} {
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switch key {
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case "auth.user":
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return uic.user
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case "auth.user.name":
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return uic.user.Name
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}
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return uic.Context.Value(key)
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}
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// InitFunc is the type of an AccessController factory function and is used
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// to register the contsructor for different AccesController backends.
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type InitFunc func(options map[string]interface{}) (AccessController, error)
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var accessControllers map[string]InitFunc
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func init() {
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accessControllers = make(map[string]InitFunc)
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}
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// Register is used to register an InitFunc for
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// an AccessController backend with the given name.
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func Register(name string, initFunc InitFunc) error {
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if _, exists := accessControllers[name]; exists {
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return fmt.Errorf("name already registered: %s", name)
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}
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accessControllers[name] = initFunc
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return nil
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}
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// GetAccessController constructs an AccessController
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// with the given options using the named backend.
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func GetAccessController(name string, options map[string]interface{}) (AccessController, error) {
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if initFunc, exists := accessControllers[name]; exists {
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return initFunc(options)
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}
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return nil, fmt.Errorf("no access controller registered with name: %s", name)
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}
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