Implement Authorization Callback Function (#108)

* Implement Authorization Callback Function

* Skip new client unit test if knox daemon is running

* add tests for SetAccessCallback

* check if knox daemon is running if on linux and using systemctl instead of pgrep

* add tests for authorizeRequest

* address nits and add testing for panic

* modify requests to return a internal server error if the authorizeRequest returns error

* run all top level tests, reset callback in tests

* Address nits in PR for authorization callback

* make static definition of expected error into testCase field

---------

Co-authored-by: henryluo <henryluo@pinterest.com>

client_test.go

@@ -1,12 +1,15 @@
 package knox
 
 import (
+	"bytes"
 	"encoding/json"
 	"net/http"
 	"net/http/httptest"
 	"os"
+	"os/exec"
 	"path"
 	"reflect"
+	"runtime"
 	"sync/atomic"
 	"testing"
 )
@@ -75,7 +78,7 @@ func buildServer(code int, body []byte, a func(r *http.Request)) *httptest.Serve
 	}))
 }
 
-func buildConcurrentServer(code int, t *testing.T, a func(r *http.Request) []byte) *httptest.Server {
+func buildConcurrentServer(code int, a func(r *http.Request) []byte) *httptest.Server {
 	return httptest.NewTLSServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
 		resp := a(r)
 		w.WriteHeader(code)
@@ -84,6 +87,23 @@ func buildConcurrentServer(code int, t *testing.T, a func(r *http.Request) []byt
 	}))
 }
 
+func isKnoxDaemonRunning() bool {
+	if runtime.GOOS != "linux" {
+		return false
+	}
+
+	cmd := exec.Command("systemctl", "is-active", "--quiet", "knox")
+
+	var out bytes.Buffer
+	cmd.Stdout = &out
+	err := cmd.Run()
+	if err == nil {
+		return true
+	}
+
+	return false
+}
+
 func TestGetKey(t *testing.T) {
 	expected := Key{
 		ID:          "testkey",
@@ -357,7 +377,7 @@ func TestPutAccess(t *testing.T) {
 
 func TestConcurrentDeletes(t *testing.T) {
 	var ops uint64
-	srv := buildConcurrentServer(200, t, func(r *http.Request) []byte {
+	srv := buildConcurrentServer(200, func(r *http.Request) []byte {
 		if r.Method != "DELETE" {
 			t.Fatalf("%s is not DELETE", r.Method)
 		}
@@ -511,6 +531,10 @@ func TestGetInvalidKeys(t *testing.T) {
 }
 
 func TestNewFileClient(t *testing.T) {
+	if isKnoxDaemonRunning() {
+		t.Skip("Knox daemon is running, skipping the test.")
+	}
+
 	_, err := NewFileClient("ThisKeyDoesNotExistSoWeExpectAnError")
 	if (err.Error() != "error getting knox key ThisKeyDoesNotExistSoWeExpectAnError. error: exit status 1") && (err.Error() != "error getting knox key ThisKeyDoesNotExistSoWeExpectAnError. error: exec: \"knox\": executable file not found in $PATH") {
 		t.Fatal("Unexpected error", err.Error())

knox.go

@@ -508,6 +508,14 @@ type Principal interface {
 	CanAccess(ACL, AccessType) bool
 	GetID() string
 	Type() string
+	Raw() []RawPrincipal
+}
+
+// RawPrincipal is a serializable version of a principal for passing to
+// access callbacks.
+type RawPrincipal struct {
+	ID   string `json:"id"`
+	Type string `json:"type"`
 }
 
 // PrincipalMux provides a Principal Interface over multiple Principals.
@@ -564,6 +572,15 @@ func (p PrincipalMux) Default() Principal {
 	return p.defaultPrincipal
 }
 
+// Raw returns the raw version of all the principals.
+func (p PrincipalMux) Raw() []RawPrincipal {
+	raw := []RawPrincipal{}
+	for _, principal := range p.allPrincipals {
+		raw = append(raw, principal.Raw()...)
+	}
+	return raw
+}
+
 // NewPrincipalMux returns a Principal that represents many principals.
 func NewPrincipalMux(defaultPrincipal Principal, allPrincipals map[string]Principal) Principal {
 	return PrincipalMux{
@@ -599,3 +616,10 @@ type Response struct {
 	Message   string      `json:"message"`
 	Data      interface{} `json:"data"`
 }
+
+// AccessCallbackInput is the input to the access callback function.
+type AccessCallbackInput struct {
+	Key        Key            `json:"key"`
+	Principals []RawPrincipal `json:"principals"`
+	AccessType AccessType     `json:"access_type"`
+}

server/api.go

@@ -294,6 +294,13 @@ func AddDefaultAccess(a *knox.Access) {
 	defaultAccess = append(defaultAccess, *a)
 }
 
+var accessCallback func(knox.AccessCallbackInput) (bool, error)
+
+// SetAccessCallback adds a callback.
+func SetAccessCallback(callback func(knox.AccessCallbackInput) (bool, error)) {
+	accessCallback = callback
+}
+
 // Extra validators to apply on principals submitted to Knox.
 var extraPrincipalValidators []knox.PrincipalValidator
 

server/api_test.go

@@ -49,6 +49,10 @@ func additionalMockHandler(m KeyManager, principal knox.Principal, parameters ma
 	return "The meaning of life is 42", nil
 }
 
+func mockAccessCallback(input knox.AccessCallbackInput) (bool, error) {
+	return true, nil
+}
+
 func mockRoute() Route {
 	return Route{
 		Method:     "GET",
@@ -105,6 +109,27 @@ func TestAddDefaultAccess(t *testing.T) {
 
 }
 
+func TestSetAccessCallback(t *testing.T) {
+	defer SetAccessCallback(nil)
+
+	SetAccessCallback(mockAccessCallback)
+
+	input := knox.AccessCallbackInput{}
+
+	if accessCallback == nil {
+		t.Fatal("accessCallback should not be nil")
+	}
+
+	canAccess, err := accessCallback(input)
+	if err != nil {
+		t.Fatal("accessCallback should not return an error")
+	}
+
+	if !canAccess {
+		t.Fatal("accessCallback should return true")
+	}
+}
+
 func TestParseFormParameter(t *testing.T) {
 	p := PostParameter("key")
 

server/auth/auth.go

@@ -380,6 +380,15 @@ func (u user) GetID() string {
 	return u.ID
 }
 
+func (u user) Raw() []knox.RawPrincipal {
+	return []knox.RawPrincipal{
+		{
+			ID:   u.GetID(),
+			Type: u.Type(),
+		},
+	}
+}
+
 // Type returns the underlying type of a principal, for logging/debugging purposes.
 func (u user) Type() string {
 	return "user"
@@ -415,6 +424,15 @@ func (m machine) Type() string {
 	return "machine"
 }
 
+func (m machine) Raw() []knox.RawPrincipal {
+	return []knox.RawPrincipal{
+		{
+			ID:   m.GetID(),
+			Type: m.Type(),
+		},
+	}
+}
+
 // CanAccess determines if a Machine can access an object represented by the ACL
 // with a certain AccessType. It compares Machine hostname and hostname prefix.
 func (m machine) CanAccess(acl knox.ACL, t knox.AccessType) bool {
@@ -450,6 +468,15 @@ func (s service) Type() string {
 	return "service"
 }
 
+func (s service) Raw() []knox.RawPrincipal {
+	return []knox.RawPrincipal{
+		{
+			ID:   s.GetID(),
+			Type: s.Type(),
+		},
+	}
+}
+
 // CanAccess determines if a Service can access an object represented by the ACL
 // with a certain AccessType. It compares Service id and id prefix.
 func (s service) CanAccess(acl knox.ACL, t knox.AccessType) bool {

server/routes.go

@@ -8,6 +8,7 @@ import (
 	"strconv"
 
 	"github.com/pinterest/knox"
+	"github.com/pinterest/knox/log"
 	"github.com/pinterest/knox/server/auth"
 )
 
@@ -211,9 +212,15 @@ func getKeyHandler(m KeyManager, principal knox.Principal, parameters map[string
 	}
 
 	// Authorize access to data
-	if !principal.CanAccess(key.ACL, knox.Read) {
+	authorized, authzErr := authorizeRequest(key, principal, knox.Read)
+	if authzErr != nil {
+		return nil, errF(knox.InternalServerErrorCode, authzErr.Error())
+	}
+
+	if !authorized {
 		return nil, errF(knox.UnauthorizedCode, fmt.Sprintf("Principal %s not authorized to read %s", principal.GetID(), keyID))
 	}
+
 	// Zero ACL for key response, in order to avoid caching unnecessarily
 	key.ACL = knox.ACL{}
 	return key, nil
@@ -234,7 +241,12 @@ func deleteKeyHandler(m KeyManager, principal knox.Principal, parameters map[str
 	}
 
 	// Authorize
-	if !principal.CanAccess(key.ACL, knox.Admin) {
+	authorized, authzErr := authorizeRequest(key, principal, knox.Admin)
+	if authzErr != nil {
+		return nil, errF(knox.InternalServerErrorCode, authzErr.Error())
+	}
+
+	if !authorized {
 		return nil, errF(knox.UnauthorizedCode, fmt.Sprintf("Principal %s not authorized to delete %s", principal.GetID(), keyID))
 	}
 
@@ -314,7 +326,12 @@ func putAccessHandler(m KeyManager, principal knox.Principal, parameters map[str
 	}
 
 	// Authorize
-	if !principal.CanAccess(key.ACL, knox.Admin) {
+	authorized, authzErr := authorizeRequest(key, principal, knox.Admin)
+	if authzErr != nil {
+		return nil, errF(knox.InternalServerErrorCode, authzErr.Error())
+	}
+
+	if !authorized {
 		return nil, errF(knox.UnauthorizedCode, fmt.Sprintf("Principal %s not authorized to update access for %s", principal.GetID(), keyID))
 	}
 
@@ -371,7 +388,12 @@ func postVersionHandler(m KeyManager, principal knox.Principal, parameters map[s
 	}
 
 	// Authorize
-	if !principal.CanAccess(key.ACL, knox.Write) {
+	authorized, authzErr := authorizeRequest(key, principal, knox.Write)
+	if authzErr != nil {
+		return nil, errF(knox.InternalServerErrorCode, authzErr.Error())
+	}
+
+	if !authorized {
 		return nil, errF(knox.UnauthorizedCode, fmt.Sprintf("Principal %s not authorized to write %s", principal.GetID(), keyID))
 	}
 
@@ -428,7 +450,12 @@ func putVersionsHandler(m KeyManager, principal knox.Principal, parameters map[s
 	}
 
 	// Authorize
-	if !principal.CanAccess(key.ACL, knox.Write) {
+	authorized, authzErr := authorizeRequest(key, principal, knox.Write)
+	if authzErr != nil {
+		return nil, errF(knox.InternalServerErrorCode, authzErr.Error())
+	}
+
+	if !authorized {
 		return nil, errF(knox.UnauthorizedCode, fmt.Sprintf("Principal %s not authorized to write %s", principal.GetID(), keyID))
 	}
 
@@ -445,3 +472,25 @@ func putVersionsHandler(m KeyManager, principal knox.Principal, parameters map[s
 		return nil, errF(knox.InternalServerErrorCode, err.Error())
 	}
 }
+
+func authorizeRequest(key *knox.Key, principal knox.Principal, access knox.AccessType) (allow bool, err error) {
+	defer func() {
+		if r := recover(); r != nil {
+			log.Printf("Recovered from panic in access callback: %v", r)
+
+			err = fmt.Errorf("Recovered from panic in access callback: %v", r)
+		}
+	}()
+
+	allow = principal.CanAccess(key.ACL, access)
+
+	if !allow && accessCallback != nil {
+		allow, err = accessCallback(knox.AccessCallbackInput{
+			Key:        *key,
+			Principals: principal.Raw(),
+			AccessType: access,
+		})
+	}
+
+	return
+}