feat: add rbac specificity for dbpurge (#21088)

Related to
[`internal#1139`](https://github.com/coder/internal/issues/1139)

Continuation of #21074 

This implements some RBAC role specificity for `dbpurge`, ensuring that
we follow the least-privileged model for removing data from the
database. It is specified as following.

```go
Site: rbac.Permissions(map[string][]policy.Action{
	// DeleteOldWorkspaceAgentLogs
	// DeleteOldWorkspaceAgentStats
	// DeleteOldProvisionerDaemons
	// DeleteOldTelemetryLocks
	// DeleteOldAuditLogConnectionEvents
	// DeleteOldConnectionLogs
	rbac.ResourceSystem.Type: {policy.ActionDelete},
	// DeleteOldNotificationMessages
	rbac.ResourceNotificationMessage.Type: {policy.ActionDelete},
	// ExpirePrebuildsAPIKeys
	// DeleteExpiredAPIKeys
	rbac.ResourceApiKey.Type: {policy.ActionDelete},
	// DeleteOldAIBridgeRecords
	rbac.ResourceAibridgeInterception.Type: {policy.ActionDelete},
}),
```

| Position | Pull-request |
| -------- | ------------ |
| | [feat: add prometheus observability metrics for
`dbpurge`](https://github.com/coder/coder/pull/21074) |
| ✅ | [feat: add rbac specificity for
`dbpurge`](https://github.com/coder/coder/pull/21088) |

coderd/database/dbauthz/dbauthz.go

@@ -616,6 +616,27 @@ var (
 		}),
 		Scope: rbac.ScopeAll,
 	}.WithCachedASTValue()
+
+	subjectDBPurge = rbac.Subject{
+		Type:         rbac.SubjectTypeDBPurge,
+		FriendlyName: "DB Purge",
+		ID:           uuid.Nil.String(),
+		Roles: rbac.Roles([]rbac.Role{
+			{
+				Identifier:  rbac.RoleIdentifier{Name: "dbpurge"},
+				DisplayName: "DB Purge Daemon",
+				Site: rbac.Permissions(map[string][]policy.Action{
+					rbac.ResourceSystem.Type:               {policy.ActionDelete},
+					rbac.ResourceNotificationMessage.Type:  {policy.ActionDelete},
+					rbac.ResourceApiKey.Type:               {policy.ActionDelete},
+					rbac.ResourceAibridgeInterception.Type: {policy.ActionDelete},
+				}),
+				User:    []rbac.Permission{},
+				ByOrgID: map[string]rbac.OrgPermissions{},
+			},
+		}),
+		Scope: rbac.ScopeAll,
+	}.WithCachedASTValue()
 )
 
 // AsProvisionerd returns a context with an actor that has permissions required
@@ -710,6 +731,12 @@ func AsAIBridged(ctx context.Context) context.Context {
 	return As(ctx, subjectAibridged)
 }
 
+// AsDBPurge returns a context with an actor that has permissions required
+// for dbpurge to delete old database records.
+func AsDBPurge(ctx context.Context) context.Context {
+	return As(ctx, subjectDBPurge)
+}
+
 var AsRemoveActor = rbac.Subject{
 	ID: "remove-actor",
 }

coderd/database/dbpurge/dbpurge.go

@@ -46,8 +46,8 @@ func New(ctx context.Context, logger slog.Logger, db database.Store, vals *coder
 	closed := make(chan struct{})
 
 	ctx, cancelFunc := context.WithCancel(ctx)
-	//nolint:gocritic // The system purges old db records without user input.
+	//nolint:gocritic // Use dbpurge-specific subject with minimal permissions.
-	ctx = dbauthz.AsSystemRestricted(ctx)
+	ctx = dbauthz.AsDBPurge(ctx)
 
 	iterationDuration := prometheus.NewHistogramVec(prometheus.HistogramOpts{
 		Namespace: "coderd",

coderd/database/dbpurge/dbpurge_test.go

@@ -22,8 +22,10 @@ import (
 	"cdr.dev/slog"
 	"cdr.dev/slog/sloggers/slogtest"
 
+	"github.com/coder/coder/v2/coderd/coderdtest"
 	"github.com/coder/coder/v2/coderd/coderdtest/promhelp"
 	"github.com/coder/coder/v2/coderd/database"
+	"github.com/coder/coder/v2/coderd/database/dbauthz"
 	"github.com/coder/coder/v2/coderd/database/dbgen"
 	"github.com/coder/coder/v2/coderd/database/dbmock"
 	"github.com/coder/coder/v2/coderd/database/dbpurge"
@@ -31,6 +33,7 @@ import (
 	"github.com/coder/coder/v2/coderd/database/dbtestutil"
 	"github.com/coder/coder/v2/coderd/database/dbtime"
 	"github.com/coder/coder/v2/coderd/provisionerdserver"
+	"github.com/coder/coder/v2/coderd/rbac"
 	"github.com/coder/coder/v2/codersdk"
 	"github.com/coder/coder/v2/provisionerd/proto"
 	"github.com/coder/coder/v2/provisionersdk"
@@ -1631,6 +1634,62 @@ func TestDeleteExpiredAPIKeys(t *testing.T) {
 	}
 }
 
+func TestDBPurgeAuthorization(t *testing.T) {
+	t.Parallel()
+
+	t.Run("DBPurgeActorCanCallPurgeOperations", func(t *testing.T) {
+		t.Parallel()
+
+		ctx := testutil.Context(t, testutil.WaitShort)
+		rawDB, _ := dbtestutil.NewDB(t)
+
+		authz := rbac.NewAuthorizer(prometheus.NewRegistry())
+		db := dbauthz.New(rawDB, authz, testutil.Logger(t), coderdtest.AccessControlStorePointer())
+
+		ctx = dbauthz.AsDBPurge(ctx)
+
+		actor, ok := dbauthz.ActorFromContext(ctx)
+		require.True(t, ok, "actor should be present")
+		require.Equal(t, rbac.SubjectTypeDBPurge, actor.Type, "should be DBPurge type")
+		require.Contains(t, actor.Roles.Names(), rbac.RoleIdentifier{Name: "dbpurge"},
+			"should have dbpurge role")
+
+		_, err := db.DeleteOldWorkspaceAgentLogs(ctx, time.Now().Add(-24*time.Hour))
+		require.NoError(t, err)
+
+		err = db.DeleteOldWorkspaceAgentStats(ctx)
+		require.NoError(t, err)
+
+		err = db.DeleteOldProvisionerDaemons(ctx)
+		require.NoError(t, err)
+
+		err = db.DeleteOldNotificationMessages(ctx)
+		require.NoError(t, err)
+
+		err = db.ExpirePrebuildsAPIKeys(ctx, time.Now().Add(-24*time.Hour))
+		require.NoError(t, err)
+
+		params := database.DeleteExpiredAPIKeysParams{
+			Before:     time.Now().Add(-24 * time.Hour),
+			LimitCount: 100,
+		}
+		_, err = db.DeleteExpiredAPIKeys(ctx, params)
+		require.NoError(t, err)
+
+		err = db.DeleteOldAuditLogConnectionEvents(ctx, database.DeleteOldAuditLogConnectionEventsParams{
+			BeforeTime: time.Now().Add(-24 * time.Hour),
+			LimitCount: 100,
+		})
+		require.NoError(t, err)
+
+		_, err = db.DeleteOldAuditLogs(ctx, database.DeleteOldAuditLogsParams{
+			BeforeTime: time.Now().Add(-24 * time.Hour),
+			LimitCount: 100,
+		})
+		require.NoError(t, err)
+	})
+}
+
 // ptr is a helper to create a pointer to a value.
 func ptr[T any](v T) *T {
 	return &v

coderd/httpmw/loggermw/logger_full.go

@@ -50,6 +50,7 @@ var actorLogOrder = []rbac.SubjectType{
 	rbac.SubjectTypeAutostart,
 	rbac.SubjectTypeCryptoKeyReader,
 	rbac.SubjectTypeCryptoKeyRotator,
+	rbac.SubjectTypeDBPurge,
 	rbac.SubjectTypeJobReaper,
 	rbac.SubjectTypeNotifier,
 	rbac.SubjectTypePrebuildsOrchestrator,

coderd/rbac/authz.go

@@ -79,6 +79,7 @@ const (
 	SubjectTypeFileReader                   SubjectType = "file_reader"
 	SubjectTypeUsagePublisher               SubjectType = "usage_publisher"
 	SubjectAibridged                        SubjectType = "aibridged"
+	SubjectTypeDBPurge                      SubjectType = "dbpurge"
 )
 
 const (