Handle cookie signing errors

pkg/encryption/utils.go

@@ -2,19 +2,16 @@ package encryption
 
 import (
 	"crypto/hmac"
-	"crypto/rand"
+	// TODO (@NickMeves): Remove SHA1 signed cookie support in V7
 	"crypto/sha1" // #nosec G505
 	"crypto/sha256"
 	"encoding/base64"
 	"fmt"
 	"hash"
-	"io"
 	"net/http"
 	"strconv"
 	"strings"
 	"time"
-
-	"github.com/oauth2-proxy/oauth2-proxy/pkg/logger"
 )
 
 // SecretBytes attempts to base64 decode the secret, if that fails it treats the secret as binary
@@ -69,40 +66,44 @@ func Validate(cookie *http.Cookie, seed string, expiration time.Duration) (value
 }
 
 // SignedValue returns a cookie that is signed and can later be checked with Validate
-func SignedValue(seed string, key string, value []byte, now time.Time) string {
+func SignedValue(seed string, key string, value []byte, now time.Time) (string, error) {
 	encodedValue := base64.URLEncoding.EncodeToString(value)
 	timeStr := fmt.Sprintf("%d", now.Unix())
-	sig := cookieSignature(sha256.New, seed, key, encodedValue, timeStr)
+	sig, err := cookieSignature(sha256.New, seed, key, encodedValue, timeStr)
+	if err != nil {
+		return "", err
+	}
 	cookieVal := fmt.Sprintf("%s|%s|%s", encodedValue, timeStr, sig)
-	return cookieVal
+	return cookieVal, nil
 }
 
-func cookieSignature(signer func() hash.Hash, args ...string) string {
+func cookieSignature(signer func() hash.Hash, args ...string) (string, error) {
 	h := hmac.New(signer, []byte(args[0]))
 	for _, arg := range args[1:] {
 		_, err := h.Write([]byte(arg))
-		// If signing fails, fail closed and return something that won't validate
 		if err != nil {
-			garbage := make([]byte, 16)
-			if _, err := io.ReadFull(rand.Reader, garbage); err != nil {
-				logger.Fatal("HMAC & RNG functions both failing. Shutting down for security")
-			}
-			return base64.URLEncoding.EncodeToString(garbage)
+			return "", err
 		}
 	}
 	var b []byte
 	b = h.Sum(b)
-	return base64.URLEncoding.EncodeToString(b)
+	return base64.URLEncoding.EncodeToString(b), nil
 }
 
 func checkSignature(signature string, args ...string) bool {
-	checkSig := cookieSignature(sha256.New, args...)
+	checkSig, err := cookieSignature(sha256.New, args...)
+	if err != nil {
+		return false
+	}
 	if checkHmac(signature, checkSig) {
 		return true
 	}
 
-	// TODO: After appropriate rollout window, remove support for SHA1
-	legacySig := cookieSignature(sha1.New, args...)
+	// TODO (@NickMeves): Remove SHA1 signed cookie support in V7
+	legacySig, err := cookieSignature(sha1.New, args...)
+	if err != nil {
+		return false
+	}
 	return checkHmac(signature, legacySig)
 }
 

pkg/encryption/utils_test.go

@@ -88,8 +88,10 @@ func TestSignAndValidate(t *testing.T) {
 	value := base64.URLEncoding.EncodeToString([]byte("I am soooo encoded"))
 	epoch := "123456789"
 
-	sha256sig := cookieSignature(sha256.New, seed, key, value, epoch)
-	sha1sig := cookieSignature(sha1.New, seed, key, value, epoch)
+	sha256sig, err := cookieSignature(sha256.New, seed, key, value, epoch)
+	assert.NoError(t, err)
+	sha1sig, err := cookieSignature(sha1.New, seed, key, value, epoch)
+	assert.NoError(t, err)
 
 	assert.True(t, checkSignature(sha256sig, seed, key, value, epoch))
 	// This should be switched to False after fully deprecating SHA1