config.go

package zpa

import (
	"bytes"
	"context"
	"encoding/json"
	"errors"
	"fmt"
	"io"
	"math"
	"net/http"
	"net/url"
	"os"
	"os/user"
	"path/filepath"
	"strconv"
	"strings"
	"sync"
	"time"

	"github.com/hashicorp/go-retryablehttp"
	"github.com/hashicorp/terraform-plugin-sdk/v2/helper/logging"
	logger "github.com/zscaler/zscaler-sdk-go/v2/logger"
	rl "github.com/zscaler/zscaler-sdk-go/v2/ratelimiter"
)

const (
	defaultBaseURL           = "https://config.private.zscaler.com"
	betaBaseURL              = "https://config.zpabeta.net"
	govBaseURL               = "https://config.zpagov.net"
	govUsBaseURL             = "https://config.zpagov.us"
	previewBaseUrl           = "https://config.zpapreview.net"
	devBaseUrl               = "https://public-api.dev.zpath.net"
	devAuthUrl               = "https://authn1.dev.zpath.net/authn/v1/oauth/token?grant_type=CLIENT_CREDENTIALS"
	qaBaseUrl                = "https://config.qa.zpath.net"
	qa2BaseUrl               = "https://pdx2-zpa-config.qa2.zpath.net"
	defaultTimeout           = 240 * time.Second
	loggerPrefix             = "zpa-logger: "
	ZPA_CLIENT_ID            = "ZPA_CLIENT_ID"
	ZPA_CLIENT_SECRET        = "ZPA_CLIENT_SECRET"
	ZPA_CUSTOMER_ID          = "ZPA_CUSTOMER_ID"
	ZPA_CLOUD                = "ZPA_CLOUD"
	configPath        string = ".zpa/credentials.json"
)

var defaultBackoffConf = &BackoffConfig{
	Enabled:             true,
	MaxNumOfRetries:     100,
	RetryWaitMaxSeconds: 10,
	RetryWaitMinSeconds: 2,
}

type BackoffConfig struct {
	Enabled             bool // Set to true to enable backoff and retry mechanism
	RetryWaitMinSeconds int  // Minimum time to wait
	RetryWaitMaxSeconds int  // Maximum time to wait
	MaxNumOfRetries     int  // Maximum number of retries
}

type AuthToken struct {
	TokenType   string `json:"token_type"`
	AccessToken string `json:"access_token"`
}

type CredentialsConfig struct {
	ClientID     string `json:"zpa_client_id"`
	ClientSecret string `json:"zpa_client_secret"`
	CustomerID   string `json:"zpa_customer_id"`
	ZpaCloud     string `json:"zpa_cloud"`
}

// Config contains all the configuration data for the API client
type Config struct {
	BaseURL     *url.URL
	httpClient  *http.Client
	rateLimiter *rl.RateLimiter
	// The logger writer interface to write logging messages to. Defaults to standard out.
	Logger logger.Logger
	// Credentials for basic authentication.
	ClientID, ClientSecret, CustomerID, Cloud string
	// Backoff config
	BackoffConf *BackoffConfig
	AuthToken   *AuthToken
	sync.Mutex
	UserAgent        string
	cacheEnabled     bool
	freshCache       bool
	cacheTtl         time.Duration
	cacheCleanwindow time.Duration
	cacheMaxSizeMB   int
}

/*
NewConfig returns a default configuration for the client.
By default it will try to read the access and te secret from the environment variable.
*/
// Need to implement exponential back off to comply with the API rate limit. https://help.zscaler.com/zpa/about-rate-limiting
// 20 times in a 10 second interval for a GET call.
// 10 times in a 10 second interval for any POST/PUT/DELETE call.
// TODO Add healthCheck method to NewConfig
func NewConfig(clientID, clientSecret, customerID, cloud, userAgent string) (*Config, error) {
	var logger logger.Logger = logger.GetDefaultLogger(loggerPrefix)
	// if creds not provided in TF config, try loading from env vars
	if clientID == "" || clientSecret == "" || customerID == "" || cloud == "" || userAgent == "" {
		clientID = os.Getenv(ZPA_CLIENT_ID)
		clientSecret = os.Getenv(ZPA_CLIENT_SECRET)
		customerID = os.Getenv(ZPA_CUSTOMER_ID)
		cloud = os.Getenv(ZPA_CLOUD)
	}
	// last resort to configuration file:
	if clientID == "" || clientSecret == "" || customerID == "" {
		creds, err := loadCredentialsFromConfig(logger)
		if err != nil || creds == nil {
			return nil, err
		}
		clientID = creds.ClientID
		clientSecret = creds.ClientSecret
		customerID = creds.CustomerID
		cloud = creds.ZpaCloud
	}
	rawUrl := defaultBaseURL
	if cloud == "" {
		cloud = os.Getenv(ZPA_CLOUD)
	} else if cloud != "" {
		rawUrl = cloud
	}
	if strings.EqualFold(cloud, "PRODUCTION") {
		rawUrl = defaultBaseURL
	} else if strings.EqualFold(cloud, "BETA") {
		rawUrl = betaBaseURL
	} else if strings.EqualFold(cloud, "GOV") {
		rawUrl = govBaseURL
	} else if strings.EqualFold(cloud, "GOVUS") {
		rawUrl = govUsBaseURL
	} else if strings.EqualFold(cloud, "PREVIEW") {
		rawUrl = previewBaseUrl
	} else if strings.EqualFold(cloud, "DEV") {
		rawUrl = devBaseUrl
	} else if strings.EqualFold(cloud, "QA") {
		rawUrl = qaBaseUrl
	} else if strings.EqualFold(cloud, "QA2") {
		rawUrl = qa2BaseUrl
	}

	baseURL, err := url.Parse(rawUrl)
	if err != nil {
		logger.Printf("[ERROR] error occurred while configuring the client: %v", err)
	}
	cacheDisabled, _ := strconv.ParseBool(os.Getenv("ZSCALER_SDK_CACHE_DISABLED"))
	return &Config{
		BaseURL:          baseURL,
		Logger:           logger,
		httpClient:       nil,
		ClientID:         clientID,
		ClientSecret:     clientSecret,
		CustomerID:       customerID,
		Cloud:            cloud,
		BackoffConf:      defaultBackoffConf,
		UserAgent:        userAgent,
		rateLimiter:      rl.NewRateLimiter(20, 10, 10, 10),
		cacheEnabled:     !cacheDisabled,
		cacheTtl:         time.Minute * 10,
		cacheCleanwindow: time.Minute * 8,
		cacheMaxSizeMB:   0,
	}, err
}

func (c *Config) WithCache(cache bool) {
	c.cacheEnabled = cache
}

func (c *Config) WithCacheTtl(i time.Duration) {
	c.cacheTtl = i
}

func (c *Config) WithCacheCleanWindow(i time.Duration) {
	c.cacheCleanwindow = i
}

func (c *Config) SetBackoffConfig(backoffConf BackoffConfig) {
	c.BackoffConf = &backoffConf
}

// loadCredentialsFromConfig Returns the credentials found in a config file
func loadCredentialsFromConfig(logger logger.Logger) (*CredentialsConfig, error) {
	usr, _ := user.Current()
	dir := usr.HomeDir
	path := filepath.Join(dir, configPath)
	logger.Printf("[INFO]Loading configuration file at:%s", path)
	file, err := os.Open(path)
	if err != nil {
		return nil, errors.New("Could not open credentials file, needs to contain one json object with keys: zpa_client_id, zpa_client_secret, zpa_customer_id, and zpa_cloud. " + err.Error())
	}
	configBytes, err := io.ReadAll(file)
	if err != nil {
		return nil, err
	}
	var config CredentialsConfig
	err = json.Unmarshal(configBytes, &config)
	if err != nil || config.ClientID == "" || config.ClientSecret == "" || config.CustomerID == "" || config.ZpaCloud == "" {
		return nil, fmt.Errorf("could not parse credentials file, needs to contain one json object with keys: zpa_client_id, zpa_client_secret, zpa_customer_id, and zpa_cloud. error: %v", err)
	}
	return &config, nil
}

func (c *Config) GetHTTPClient() *http.Client {
	if c.httpClient == nil {
		if c.BackoffConf != nil && c.BackoffConf.Enabled {
			retryableClient := retryablehttp.NewClient()
			retryableClient.Logger = c.Logger
			retryableClient.RetryWaitMin = time.Second * time.Duration(c.BackoffConf.RetryWaitMinSeconds)
			retryableClient.Backoff = func(min, max time.Duration, attemptNum int, resp *http.Response) time.Duration {
				if resp != nil {
					if resp.StatusCode == http.StatusTooManyRequests || resp.StatusCode == http.StatusServiceUnavailable {
						// TODO: ask backend to implement such header, instead of using the logic below
						if s, ok := resp.Header["Retry-After"]; ok {
							if sleep, err := strconv.ParseInt(s[0], 10, 64); err == nil {
								return time.Second * time.Duration(sleep)
							}
						}
					}
					if resp.Request != nil {
						wait, duration := c.rateLimiter.Wait(resp.Request.Method)
						if wait {
							c.Logger.Printf("[INFO] rate limiter wait duration:%s\n", duration.String())
						} else {
							return 0
						}
					}
				}
				// default to exp backoff
				mult := math.Pow(2, float64(attemptNum)) * float64(min)
				sleep := time.Duration(mult)
				if float64(sleep) != mult || sleep > max {
					sleep = max
				}
				return sleep
			}
			retryableClient.RetryWaitMax = time.Second * time.Duration(c.BackoffConf.RetryWaitMaxSeconds)
			retryableClient.RetryMax = c.BackoffConf.MaxNumOfRetries
			retryableClient.HTTPClient.Transport = logging.NewSubsystemLoggingHTTPTransport("gozscaler", retryableClient.HTTPClient.Transport)
			retryableClient.CheckRetry = checkRetry
			retryableClient.HTTPClient.Timeout = defaultTimeout
			c.httpClient = retryableClient.StandardClient()
		} else {
			c.httpClient = &http.Client{
				Timeout: defaultTimeout,
			}
		}
	}
	return c.httpClient
}

func containsInt(codes []int, code int) bool {
	for _, a := range codes {
		if a == code {
			return true
		}
	}
	return false
}

// getRetryOnStatusCodes return a list of http status codes we want to apply retry on.
// return empty slice to enable retry on all connection & server errors.
// or return []int{429}  to retry on only TooManyRequests error
func getRetryOnStatusCodes() []int {
	return []int{http.StatusTooManyRequests}
}

// Used to make http client retry on provided list of response status codes
func checkRetry(ctx context.Context, resp *http.Response, err error) (bool, error) {
	// do not retry on context.Canceled or context.DeadlineExceeded
	if ctx.Err() != nil {
		return false, ctx.Err()
	}
	if resp != nil && containsInt(getRetryOnStatusCodes(), resp.StatusCode) {
		return true, nil
	}
	if resp != nil && resp.StatusCode == http.StatusBadRequest {
		respMap := map[string]string{}
		data, err := io.ReadAll(resp.Body)
		resp.Body = io.NopCloser(bytes.NewBuffer(data))
		if err == nil {
			_ = json.Unmarshal(data, &respMap)
			if errorID, ok := respMap["id"]; ok && (errorID == "non.restricted.entity.authorization.failed" || errorID == "bad.request") {
				return true, nil
			}
		}
		// Implemented to handle upstream restrictions on simultaneous requests when dealing with CRUD operations, related to ZPA Access policy rule order
		// ET-53585: https://jira.corp.zscaler.com/browse/ET-53585
		// ET-48860: https://confluence.corp.zscaler.com/display/ET/ET-48860+incorrect+rules+order
		if err == nil {
			_ = json.Unmarshal(data, &respMap)
			if errorID, ok := respMap["id"]; ok && (errorID == "db.simultaneous.request" || errorID == "bad.request") {
				return true, nil
			}
		}
	}
	return retryablehttp.DefaultRetryPolicy(ctx, resp, err)
}