act/pkg/runner/expression.go

package runner

import (
	"crypto/sha256"
	"encoding/hex"
	"encoding/json"
	"errors"
	"fmt"
	"io"
	"os"
	"path/filepath"
	"regexp"
	"strconv"
	"strings"

	"github.com/robertkrimen/otto"
	log "github.com/sirupsen/logrus"
)

var expressionPattern, operatorPattern *regexp.Regexp

func init() {
	expressionPattern = regexp.MustCompile(`\${{\s*(.+?)\s*}}`)
	operatorPattern = regexp.MustCompile("^[!=><|&]+$")
}

// NewExpressionEvaluator creates a new evaluator
func (rc *RunContext) NewExpressionEvaluator() ExpressionEvaluator {
	vm := rc.newVM()

	return &expressionEvaluator{
		vm,
	}
}

// NewExpressionEvaluator creates a new evaluator
func (sc *StepContext) NewExpressionEvaluator() ExpressionEvaluator {
	vm := sc.RunContext.newVM()
	configers := []func(*otto.Otto){
		sc.vmEnv(),
		sc.vmInputs(),

		sc.vmNeeds(),
		sc.vmSuccess(),
		sc.vmFailure(),
	}
	for _, configer := range configers {
		configer(vm)
	}

	return &expressionEvaluator{
		vm,
	}
}

// ExpressionEvaluator is the interface for evaluating expressions
type ExpressionEvaluator interface {
	Evaluate(string) (string, bool, error)
	Interpolate(string) string
	InterpolateWithStringCheck(string) (string, bool)
	Rewrite(string) string
}

type expressionEvaluator struct {
	vm *otto.Otto
}

func (ee *expressionEvaluator) Evaluate(in string) (string, bool, error) {
	if strings.HasPrefix(in, `secrets.`) {
		in = `secrets.` + strings.ToUpper(strings.SplitN(in, `.`, 2)[1])
	}
	re := ee.Rewrite(in)
	if re != in {
		log.Debugf("Evaluating '%s' instead of '%s'", re, in)
	}

	val, err := ee.vm.Run(re)
	if err != nil {
		return "", false, err
	}
	if val.IsNull() || val.IsUndefined() {
		return "", false, nil
	}
	valAsString, err := val.ToString()
	if err != nil {
		return "", false, err
	}

	return valAsString, val.IsString(), err
}

func (ee *expressionEvaluator) Interpolate(in string) string {
	interpolated, _ := ee.InterpolateWithStringCheck(in)
	return interpolated
}

func (ee *expressionEvaluator) InterpolateWithStringCheck(in string) (string, bool) {
	errList := make([]error, 0)

	out := in
	isString := false
	for {
		out = expressionPattern.ReplaceAllStringFunc(in, func(match string) string {
			// Extract and trim the actual expression inside ${{...}} delimiters
			expression := expressionPattern.ReplaceAllString(match, "$1")

			// Evaluate the expression and retrieve errors if any
			evaluated, evaluatedIsString, err := ee.Evaluate(expression)
			if err != nil {
				errList = append(errList, err)
			}
			isString = evaluatedIsString
			return evaluated
		})
		if len(errList) > 0 {
			log.Errorf("Unable to interpolate string '%s' - %v", in, errList)
			break
		}
		if out == in {
			// No replacement occurred, we're done!
			break
		}
		in = out
	}
	return out, isString
}

// Rewrite tries to transform any javascript property accessor into its bracket notation.
// For instance, "object.property" would become "object['property']".
func (ee *expressionEvaluator) Rewrite(in string) string {
	var buf strings.Builder
	r := strings.NewReader(in)
	for {
		c, _, err := r.ReadRune()
		if err == io.EOF {
			break
		}
		//nolint
		switch {
		default:
			buf.WriteRune(c)
		case c == '\'':
			buf.WriteRune(c)
			ee.advString(&buf, r)
		case c == '.':
			buf.WriteString("['")
			ee.advPropertyName(&buf, r)
			buf.WriteString("']")
		}
	}
	return buf.String()
}

func (*expressionEvaluator) advString(w *strings.Builder, r *strings.Reader) error {
	for {
		c, _, err := r.ReadRune()
		if err != nil {
			return err
		}
		if c != '\'' {
			w.WriteRune(c) //nolint
			continue
		}

		// Handles a escaped string: ex. 'It''s ok'
		c, _, err = r.ReadRune()
		if err != nil {
			w.WriteString("'") //nolint
			return err
		}
		if c != '\'' {
			w.WriteString("'") //nolint
			if err := r.UnreadRune(); err != nil {
				return err
			}
			break
		}
		w.WriteString(`\'`) //nolint
	}
	return nil
}

func (*expressionEvaluator) advPropertyName(w *strings.Builder, r *strings.Reader) error {
	for {
		c, _, err := r.ReadRune()
		if err != nil {
			return err
		}
		if !isLetter(c) {
			if err := r.UnreadRune(); err != nil {
				return err
			}
			break
		}
		w.WriteRune(c) //nolint
	}
	return nil
}

func isLetter(c rune) bool {
	switch {
	case c >= 'a' && c <= 'z':
		return true
	case c >= 'A' && c <= 'Z':
		return true
	case c >= '0' && c <= '9':
		return true
	case c == '_' || c == '-':
		return true
	default:
		return false
	}
}

func (rc *RunContext) newVM() *otto.Otto {
	configers := []func(*otto.Otto){
		vmContains,
		vmStartsWith,
		vmEndsWith,
		vmFormat,
		vmJoin,
		vmToJSON,
		vmFromJSON,
		vmAlways,
		rc.vmCancelled(),
		rc.vmSuccess(),
		rc.vmFailure(),
		rc.vmHashFiles(),

		rc.vmGithub(),
		rc.vmJob(),
		rc.vmSteps(),
		rc.vmRunner(),

		rc.vmSecrets(),
		rc.vmStrategy(),
		rc.vmMatrix(),
		rc.vmEnv(),
		rc.vmNeeds(),
	}
	vm := otto.New()
	for _, configer := range configers {
		configer(vm)
	}
	return vm
}

func vmContains(vm *otto.Otto) {
	_ = vm.Set("contains", func(searchString interface{}, searchValue string) bool {
		if searchStringString, ok := searchString.(string); ok {
			return strings.Contains(strings.ToLower(searchStringString), strings.ToLower(searchValue))
		} else if searchStringArray, ok := searchString.([]string); ok {
			for _, s := range searchStringArray {
				if strings.EqualFold(s, searchValue) {
					return true
				}
			}
		}
		return false
	})
}

func vmStartsWith(vm *otto.Otto) {
	_ = vm.Set("startsWith", func(searchString string, searchValue string) bool {
		return strings.HasPrefix(strings.ToLower(searchString), strings.ToLower(searchValue))
	})
}

func vmEndsWith(vm *otto.Otto) {
	_ = vm.Set("endsWith", func(searchString string, searchValue string) bool {
		return strings.HasSuffix(strings.ToLower(searchString), strings.ToLower(searchValue))
	})
}

func vmFormat(vm *otto.Otto) {
	_ = vm.Set("format", func(s string, vals ...otto.Value) string {
		ex := regexp.MustCompile(`(\{[0-9]+\}|\{.?|\}.?)`)
		return ex.ReplaceAllStringFunc(s, func(seg string) string {
			switch seg {
			case "{{":
				return "{"
			case "}}":
				return "}"
			default:
				if len(seg) < 3 || !strings.HasPrefix(seg, "{") {
					log.Errorf("The following format string is invalid: '%v'", s)
					return ""
				}
				_i := seg[1 : len(seg)-1]
				i, err := strconv.ParseInt(_i, 10, 32)
				if err != nil {
					log.Errorf("The following format string is invalid: '%v'. Error: %v", s, err)
					return ""
				}
				if i >= int64(len(vals)) {
					log.Errorf("The following format string references more arguments than were supplied: '%v'", s)
					return ""
				}
				if vals[i].IsNull() || vals[i].IsUndefined() {
					return ""
				}
				return vals[i].String()
			}
		})
	})
}

func vmJoin(vm *otto.Otto) {
	_ = vm.Set("join", func(element interface{}, optionalElem string) string {
		slist := make([]string, 0)
		if elementString, ok := element.(string); ok {
			slist = append(slist, elementString)
		} else if elementArray, ok := element.([]string); ok {
			slist = append(slist, elementArray...)
		}
		if optionalElem != "" {
			slist = append(slist, optionalElem)
		}
		return strings.Join(slist, " ")
	})
}

func vmToJSON(vm *otto.Otto) {
	toJSON := func(o interface{}) string {
		rtn, err := json.MarshalIndent(o, "", "  ")
		if err != nil {
			log.Errorf("Unable to marshal: %v", err)
			return ""
		}
		return string(rtn)
	}
	_ = vm.Set("toJSON", toJSON)
	_ = vm.Set("toJson", toJSON)
}

func vmFromJSON(vm *otto.Otto) {
	fromJSON := func(str string) interface{} {
		var dat interface{}
		err := json.Unmarshal([]byte(str), &dat)
		if err != nil {
			log.Errorf("Unable to unmarshal: %v", err)
			return dat
		}
		return dat
	}
	_ = vm.Set("fromJSON", fromJSON)
	_ = vm.Set("fromJson", fromJSON)
}

func (rc *RunContext) vmHashFiles() func(*otto.Otto) {
	return func(vm *otto.Otto) {
		_ = vm.Set("hashFiles", func(paths ...string) string {
			var files []string
			for i := range paths {
				newFiles, err := filepath.Glob(filepath.Join(rc.Config.Workdir, paths[i]))
				if err != nil {
					log.Errorf("Unable to glob.Glob: %v", err)
					return ""
				}
				files = append(files, newFiles...)
			}
			hasher := sha256.New()
			for _, file := range files {
				f, err := os.Open(file)
				if err != nil {
					log.Errorf("Unable to os.Open: %v", err)
				}
				if _, err := io.Copy(hasher, f); err != nil {
					log.Errorf("Unable to io.Copy: %v", err)
				}
				if err := f.Close(); err != nil {
					log.Errorf("Unable to Close file: %v", err)
				}
			}
			return hex.EncodeToString(hasher.Sum(nil))
		})
	}
}

func (rc *RunContext) vmSuccess() func(*otto.Otto) {
	return func(vm *otto.Otto) {
		_ = vm.Set("success", func() bool {
			jobs := rc.Run.Workflow.Jobs
			jobNeeds := rc.getNeedsTransitive(rc.Run.Job())

			for _, needs := range jobNeeds {
				if jobs[needs].Result != "success" {
					return false
				}
			}

			return true
		})
	}
}

func (rc *RunContext) vmFailure() func(*otto.Otto) {
	return func(vm *otto.Otto) {
		_ = vm.Set("failure", func() bool {
			jobs := rc.Run.Workflow.Jobs
			jobNeeds := rc.getNeedsTransitive(rc.Run.Job())

			for _, needs := range jobNeeds {
				if jobs[needs].Result == "failure" {
					return true
				}
			}

			return false
		})
	}
}

func vmAlways(vm *otto.Otto) {
	_ = vm.Set("always", func() bool {
		return true
	})
}
func (rc *RunContext) vmCancelled() func(vm *otto.Otto) {
	return func(vm *otto.Otto) {
		_ = vm.Set("cancelled", func() bool {
			return rc.getJobContext().Status == "cancelled"
		})
	}
}

func (rc *RunContext) vmGithub() func(*otto.Otto) {
	github := rc.getGithubContext()

	return func(vm *otto.Otto) {
		_ = vm.Set("github", github)
	}
}

func (rc *RunContext) vmEnv() func(*otto.Otto) {
	return func(vm *otto.Otto) {
		env := rc.GetEnv()
		log.Debugf("context env => %v", env)
		_ = vm.Set("env", env)
	}
}

func (sc *StepContext) vmEnv() func(*otto.Otto) {
	return func(vm *otto.Otto) {
		log.Debugf("context env => %v", sc.Env)
		_ = vm.Set("env", sc.Env)
	}
}

func (sc *StepContext) vmInputs() func(*otto.Otto) {
	inputs := make(map[string]string)

	// Set Defaults
	if sc.Action != nil {
		for k, input := range sc.Action.Inputs {
			inputs[k] = sc.RunContext.NewExpressionEvaluator().Interpolate(input.Default)
		}
	}

	for k, v := range sc.Step.With {
		inputs[k] = sc.RunContext.NewExpressionEvaluator().Interpolate(v)
	}

	return func(vm *otto.Otto) {
		_ = vm.Set("inputs", inputs)
	}
}

func (sc *StepContext) vmNeeds() func(*otto.Otto) {
	jobs := sc.RunContext.Run.Workflow.Jobs
	jobNeeds := sc.RunContext.Run.Job().Needs()

	using := make(map[string]map[string]map[string]string)
	for _, needs := range jobNeeds {
		using[needs] = map[string]map[string]string{
			"outputs": jobs[needs].Outputs,
		}
	}

	return func(vm *otto.Otto) {
		log.Debugf("context needs => %v", using)
		_ = vm.Set("needs", using)
	}
}

func (sc *StepContext) vmSuccess() func(*otto.Otto) {
	return func(vm *otto.Otto) {
		_ = vm.Set("success", func() bool {
			return sc.RunContext.getJobContext().Status == "success"
		})
	}
}

func (sc *StepContext) vmFailure() func(*otto.Otto) {
	return func(vm *otto.Otto) {
		_ = vm.Set("failure", func() bool {
			return sc.RunContext.getJobContext().Status == "failure"
		})
	}
}

type vmNeedsStruct struct {
	Outputs map[string]string `json:"outputs"`
	Result  string            `json:"result"`
}

func (rc *RunContext) vmNeeds() func(*otto.Otto) {
	return func(vm *otto.Otto) {
		needsFunc := func() otto.Value {
			jobs := rc.Run.Workflow.Jobs
			jobNeeds := rc.Run.Job().Needs()

			using := make(map[string]vmNeedsStruct)
			for _, needs := range jobNeeds {
				using[needs] = vmNeedsStruct{
					Outputs: jobs[needs].Outputs,
					Result:  jobs[needs].Result,
				}
			}

			log.Debugf("context needs => %+v", using)

			value, err := vm.ToValue(using)
			if err != nil {
				return vm.MakeTypeError(err.Error())
			}

			return value
		}

		// Results might change after the Otto VM was created
		// and initialized. To access the current state
		// we can't just pass a copy to Otto - instead we
		// created a 'live-binding'.
		// Technical Note: We don't want to pollute the global
		// js namespace (and add things github actions hasn't)
		// we delete the helper function after installing it
		// as a getter.
		global, _ := vm.Run("this")
		_ = global.Object().Set("__needs__", needsFunc)
		_, _ = vm.Run(`
			(function (global) {
				Object.defineProperty(global, 'needs', { get: global.__needs__ });
				delete global.__needs__;
			})(this)
		`)
	}
}

func (rc *RunContext) vmJob() func(*otto.Otto) {
	job := rc.getJobContext()

	return func(vm *otto.Otto) {
		_ = vm.Set("job", job)
	}
}

func (rc *RunContext) vmSteps() func(*otto.Otto) {
	ctxSteps := rc.getStepsContext()

	steps := make(map[string]interface{})
	for id, ctxStep := range ctxSteps {
		steps[id] = map[string]interface{}{
			"conclusion": ctxStep.Conclusion.String(),
			"outcome":    ctxStep.Outcome.String(),
			"outputs":    ctxStep.Outputs,
		}
	}

	return func(vm *otto.Otto) {
		log.Debugf("context steps => %v", steps)
		_ = vm.Set("steps", steps)
	}
}

func (rc *RunContext) vmRunner() func(*otto.Otto) {
	runner := map[string]interface{}{
		"os":         "Linux",
		"temp":       "/tmp",
		"tool_cache": "/opt/hostedtoolcache",
	}

	return func(vm *otto.Otto) {
		_ = vm.Set("runner", runner)
	}
}

func (rc *RunContext) vmSecrets() func(*otto.Otto) {
	return func(vm *otto.Otto) {
		_ = vm.Set("secrets", rc.Config.Secrets)
	}
}

func (rc *RunContext) vmStrategy() func(*otto.Otto) {
	job := rc.Run.Job()
	strategy := make(map[string]interface{})
	if job.Strategy != nil {
		strategy["fail-fast"] = job.Strategy.FailFast
		strategy["max-parallel"] = job.Strategy.MaxParallel
	}
	return func(vm *otto.Otto) {
		_ = vm.Set("strategy", strategy)
	}
}

func (rc *RunContext) vmMatrix() func(*otto.Otto) {
	return func(vm *otto.Otto) {
		_ = vm.Set("matrix", rc.Matrix)
	}
}

// EvalBool evaluates an expression against given evaluator
func EvalBool(evaluator ExpressionEvaluator, expr string) (bool, error) {
	if splitPattern == nil {
		splitPattern = regexp.MustCompile(fmt.Sprintf(`%s|%s|\S+`, expressionPattern.String(), operatorPattern.String()))
	}
	if strings.HasPrefix(strings.TrimSpace(expr), "!") {
		return false, errors.New("expressions starting with ! must be wrapped in ${{ }}")
	}
	if expr != "" {
		parts := splitPattern.FindAllString(expr, -1)
		var evaluatedParts []string
		for i, part := range parts {
			if operatorPattern.MatchString(part) {
				evaluatedParts = append(evaluatedParts, part)
				continue
			}

			interpolatedPart, isString := evaluator.InterpolateWithStringCheck(part)

			// This peculiar transformation has to be done because the GitHub parser
			// treats false returned from contexts as a string, not a boolean.
			// Hence env.SOMETHING will be evaluated to true in an if: expression
			// regardless if SOMETHING is set to false, true or any other string.
			// It also handles some other weirdness that I found by trial and error.
			if (expressionPattern.MatchString(part) && // it is an expression
				!strings.Contains(part, "!")) && // but it's not negated
				interpolatedPart == "false" && // and the interpolated string is false
				(isString || previousOrNextPartIsAnOperator(i, parts)) { // and it's of type string or has an logical operator before or after
				interpolatedPart = fmt.Sprintf("'%s'", interpolatedPart) // then we have to quote the false expression
			}

			evaluatedParts = append(evaluatedParts, interpolatedPart)
		}

		joined := strings.Join(evaluatedParts, " ")
		v, _, err := evaluator.Evaluate(fmt.Sprintf("Boolean(%s)", joined))
		if err != nil {
			return false, err
		}
		log.Debugf("expression '%s' evaluated to '%s'", expr, v)
		return v == "true", nil
	}
	return true, nil
}