[runx+envsec] Use same cache location as auth pkg (#154)

## Summary

Use consistent cache locations everywhere.

Fix envsec aws credentials cache bug where cache key did not take into
account changing organizations.

## How was it tested?

internal/awsfed/awsfed.go

@@ -2,6 +2,7 @@ package awsfed
 
 import (
 	"context"
+	"crypto/sha256"
 	"encoding/json"
 	"fmt"
 
@@ -12,7 +13,7 @@ import (
 	"go.jetpack.io/pkg/sandbox/auth/session"
 )
 
-const cacheKey = "awsfed"
+const cacheKeyPrefix = "awsfed"
 
 type AWSFed struct {
 	AccountID      string
@@ -39,8 +40,8 @@ func (a *AWSFed) AWSCreds(
 	ctx context.Context,
 	tok *session.Token,
 ) (*types.Credentials, error) {
-	cache := filecache.New("envsec")
-	if cachedCreds, err := cache.Get(cacheKey); err == nil {
+	cache := filecache.New("jetpack.io/envsec")
+	if cachedCreds, err := cache.Get(cacheKey(tok)); err == nil {
 		var creds types.Credentials
 		if err := json.Unmarshal(cachedCreds, &creds); err == nil {
 			return &creds, nil
@@ -86,7 +87,7 @@ func (a *AWSFed) AWSCreds(
 	if creds, err := json.Marshal(output.Credentials); err != nil {
 		return nil, err
 	} else if err := cache.SetT(
-		cacheKey,
+		cacheKey(tok),
 		creds,
 		*output.Credentials.Expiration,
 	); err != nil {
@@ -95,3 +96,14 @@ func (a *AWSFed) AWSCreds(
 
 	return output.Credentials, nil
 }
+
+func cacheKey(t *session.Token) string {
+	id := ""
+	if claims := t.IDClaims(); claims != nil && claims.OrgID != "" {
+		id = claims.OrgID
+	} else {
+		id = fmt.Sprintf("%x", sha256.Sum256([]byte(t.IDToken)))
+	}
+
+	return fmt.Sprintf("%s-%s", cacheKeyPrefix, id)
+}

internal/filecache/filecache.go

@@ -8,20 +8,17 @@ import (
 	"time"
 
 	"github.com/pkg/errors"
-	"go.jetpack.io/envsec/internal/xdg"
 )
 
 var NotFound = errors.New("not found")
 var Expired = errors.New("expired")
 
-const prefix = "filecache-"
-
 type cache struct {
-	appName string
+	domain string
 }
 
-func New(appName string) *cache {
-	return &cache{appName: appName}
+func New(domain string) *cache {
+	return &cache{domain: domain}
 }
 
 type data struct {
@@ -68,7 +65,11 @@ func (c *cache) Get(key string) ([]byte, error) {
 }
 
 func (c *cache) filename(key string) string {
-	dir := xdg.CacheSubpath(c.appName)
+	cacheDir, err := os.UserCacheDir()
+	if err != nil {
+		cacheDir = "~/.cache"
+	}
+	dir := filepath.Join(cacheDir, c.domain)
 	_ = os.MkdirAll(dir, 0755)
-	return xdg.CacheSubpath(filepath.Join(c.appName, prefix+key))
+	return filepath.Join(dir, key)
 }