Fixed timing attack in cookie validation.
- Changed from using string == to hmac.Equal - See more details here: http://verboselogging.com/2012/08/20/a-timing-attack-in-action
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2f165345a8
commit
ad57a9391f
13
cookies.go
13
cookies.go
@ -18,7 +18,7 @@ func validateCookie(cookie *http.Cookie, seed string) (string, bool) {
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return "", false
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}
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sig := cookieSignature(seed, cookie.Name, parts[0], parts[1])
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if parts[2] == sig {
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if checkHmac(parts[2], sig) {
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ts, err := strconv.Atoi(parts[1])
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if err == nil && int64(ts) > time.Now().Add(time.Duration(24)*7*time.Hour*-1).Unix() {
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// it's a valid cookie. now get the contents
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@ -48,3 +48,14 @@ func cookieSignature(args ...string) string {
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b = h.Sum(b)
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return base64.URLEncoding.EncodeToString(b)
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}
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func checkHmac(input, expected string) bool {
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inputMAC, err1 := base64.URLEncoding.DecodeString(input)
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if err1 == nil {
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expectedMAC, err2 := base64.URLEncoding.DecodeString(expected)
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if err2 == nil {
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return hmac.Equal(inputMAC, expectedMAC)
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}
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}
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return false
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}
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