Fix local alias processing (#25496)

* Fix local alias processing

* PR feedback

vault/identity_store.go

@@ -21,6 +21,7 @@ import (
 	"github.com/hashicorp/vault/helper/versions"
 	"github.com/hashicorp/vault/sdk/framework"
 	"github.com/hashicorp/vault/sdk/helper/consts"
+	"github.com/hashicorp/vault/sdk/helper/locksutil"
 	"github.com/hashicorp/vault/sdk/logical"
 	"github.com/patrickmn/go-cache"
 )
@@ -66,6 +67,7 @@ func NewIdentityStore(ctx context.Context, core *Core, config *logical.BackendCo
 		entityCreator: core,
 		mountLister:   core,
 		mfaBackend:    core.loginMFABackend,
+		aliasLocks:    locksutil.CreateLocks(),
 	}
 
 	// Create a memdb instance, which by default, operates on lower cased

vault/identity_store_structs.go

@@ -16,6 +16,7 @@ import (
 	"github.com/hashicorp/vault/helper/storagepacker"
 	"github.com/hashicorp/vault/sdk/framework"
 	"github.com/hashicorp/vault/sdk/helper/consts"
+	"github.com/hashicorp/vault/sdk/helper/locksutil"
 	"github.com/hashicorp/vault/sdk/logical"
 )
 
@@ -104,6 +105,10 @@ type IdentityStore struct {
 	entityCreator EntityCreator
 	mountLister   MountLister
 	mfaBackend    *LoginMFABackend
+
+	// aliasLocks is used to protect modifications to alias entries based on the uniqueness factor
+	// which is name + accessor
+	aliasLocks []*locksutil.LockEntry
 }
 
 type groupDiff struct {

vault/request_handling.go

@@ -1659,6 +1659,7 @@ func (c *Core) handleLoginRequest(ctx context.Context, req *logical.Request) (re
 			var err error
 			// Fetch the entity for the alias, or create an entity if one
 			// doesn't exist.
+
 			entity, entityCreated, err := c.identityStore.CreateOrFetchEntity(ctx, auth.Alias)
 			if err != nil {
 				switch auth.Alias.Local {
@@ -1666,7 +1667,7 @@ func (c *Core) handleLoginRequest(ctx context.Context, req *logical.Request) (re
 					// Only create a new entity if the error was a readonly error and the creation flag is true
 					// i.e the entity was in the middle of being created
 					if entityCreated && errors.Is(err, logical.ErrReadOnly) {
-						entity, err = possiblyForwardEntityCreation(ctx, c, err, auth, nil)
+						entity, err = registerLocalAlias(ctx, c, auth.Alias)
 						if err != nil {
 							if strings.Contains(err.Error(), errCreateEntityUnimplemented) {
 								resp.AddWarning("primary cluster doesn't yet issue entities for local auth mounts; falling back to not issuing entities for local auth mounts")
@@ -1676,14 +1677,14 @@ func (c *Core) handleLoginRequest(ctx context.Context, req *logical.Request) (re
 							}
 						}
 					}
-					err = updateLocalAlias(ctx, c, auth, entity)
 				default:
 					entity, entityCreated, err = possiblyForwardAliasCreation(ctx, c, err, auth, entity)
+					if err != nil {
+						return nil, nil, err
+					}
 				}
 			}
-			if err != nil {
-				return nil, nil, err
-			}
+
 			if entity == nil {
 				return nil, nil, fmt.Errorf("failed to create an entity for the authenticated alias")
 			}

vault/request_handling_util.go

@@ -68,12 +68,8 @@ func possiblyForwardAliasCreation(ctx context.Context, c *Core, inErr error, aut
 
 var errCreateEntityUnimplemented = "create entity unimplemented in the server"
 
-func possiblyForwardEntityCreation(ctx context.Context, c *Core, inErr error, auth *logical.Auth, entity *identity.Entity) (*identity.Entity, error) {
-	return entity, inErr
-}
-
-func updateLocalAlias(ctx context.Context, c *Core, auth *logical.Auth, entity *identity.Entity) error {
-	return nil
+func registerLocalAlias(_ context.Context, _ *Core, _ *logical.Alias) (*identity.Entity, error) {
+	return nil, logical.ErrReadOnly
 }
 
 func possiblyForwardSaveCachedAuthResponse(ctx context.Context, c *Core, respAuth *MFACachedAuthResponse) error {