Make runs-on support variable expression (#29468)

As title.
Close issue: https://gitea.com/gitea/act_runner/issues/445
Follow: https://gitea.com/gitea/act/pulls/91

Move `getSecretsOfTask` and `getVariablesOfTask` under `models` because
of circular dependency issues.

models/actions/variable.go

@@ -10,6 +10,7 @@ import (
 	"strings"
 
 	"code.gitea.io/gitea/models/db"
+	"code.gitea.io/gitea/modules/log"
 	"code.gitea.io/gitea/modules/timeutil"
 	"code.gitea.io/gitea/modules/util"
 
@@ -82,3 +83,35 @@ func UpdateVariable(ctx context.Context, variable *ActionVariable) (bool, error)
 		})
 	return count != 0, err
 }
+
+func GetVariablesOfRun(ctx context.Context, run *ActionRun) (map[string]string, error) {
+	variables := map[string]string{}
+
+	// Global
+	globalVariables, err := db.Find[ActionVariable](ctx, FindVariablesOpts{})
+	if err != nil {
+		log.Error("find global variables: %v", err)
+		return nil, err
+	}
+
+	// Org / User level
+	ownerVariables, err := db.Find[ActionVariable](ctx, FindVariablesOpts{OwnerID: run.Repo.OwnerID})
+	if err != nil {
+		log.Error("find variables of org: %d, error: %v", run.Repo.OwnerID, err)
+		return nil, err
+	}
+
+	// Repo level
+	repoVariables, err := db.Find[ActionVariable](ctx, FindVariablesOpts{RepoID: run.RepoID})
+	if err != nil {
+		log.Error("find variables of repo: %d, error: %v", run.RepoID, err)
+		return nil, err
+	}
+
+	// Level precedence: Repo > Org / User > Global
+	for _, v := range append(globalVariables, append(ownerVariables, repoVariables...)...) {
+		variables[v.Name] = v.Data
+	}
+
+	return variables, nil
+}

models/secret/secret.go

@@ -9,7 +9,10 @@ import (
 	"fmt"
 	"strings"
 
+	actions_model "code.gitea.io/gitea/models/actions"
 	"code.gitea.io/gitea/models/db"
+	actions_module "code.gitea.io/gitea/modules/actions"
+	"code.gitea.io/gitea/modules/log"
 	secret_module "code.gitea.io/gitea/modules/secret"
 	"code.gitea.io/gitea/modules/setting"
 	"code.gitea.io/gitea/modules/timeutil"
@@ -112,3 +115,39 @@ func UpdateSecret(ctx context.Context, secretID int64, data string) error {
 	}
 	return err
 }
+
+func GetSecretsOfTask(ctx context.Context, task *actions_model.ActionTask) (map[string]string, error) {
+	secrets := map[string]string{}
+
+	secrets["GITHUB_TOKEN"] = task.Token
+	secrets["GITEA_TOKEN"] = task.Token
+
+	if task.Job.Run.IsForkPullRequest && task.Job.Run.TriggerEvent != actions_module.GithubEventPullRequestTarget {
+		// ignore secrets for fork pull request, except GITHUB_TOKEN and GITEA_TOKEN which are automatically generated.
+		// for the tasks triggered by pull_request_target event, they could access the secrets because they will run in the context of the base branch
+		// see the documentation: https://docs.github.com/en/actions/using-workflows/events-that-trigger-workflows#pull_request_target
+		return secrets, nil
+	}
+
+	ownerSecrets, err := db.Find[Secret](ctx, FindSecretsOptions{OwnerID: task.Job.Run.Repo.OwnerID})
+	if err != nil {
+		log.Error("find secrets of owner %v: %v", task.Job.Run.Repo.OwnerID, err)
+		return nil, err
+	}
+	repoSecrets, err := db.Find[Secret](ctx, FindSecretsOptions{RepoID: task.Job.Run.RepoID})
+	if err != nil {
+		log.Error("find secrets of repo %v: %v", task.Job.Run.RepoID, err)
+		return nil, err
+	}
+
+	for _, secret := range append(ownerSecrets, repoSecrets...) {
+		v, err := secret_module.DecryptSecret(setting.SecretKey, secret.Data)
+		if err != nil {
+			log.Error("decrypt secret %v %q: %v", secret.ID, secret.Name, err)
+			return nil, err
+		}
+		secrets[secret.Name] = v
+	}
+
+	return secrets, nil
+}