package lazycookie
import "golazy.dev/lazycookie"Variables
var (
// ErrMacInvalid indicates that cookie decoding failed because the HMAC
// could not be extracted and verified. Direct use of this error
// variable is deprecated; it is public only for legacy compatibility,
// and may be privatized in the future, as it is rarely useful to
// distinguish between this error and other Error implementations.
ErrMacInvalid = cookieError{/* contains filtered or unexported fields */}
)Functions
func DecodeMulti
DecodeMulti decodes a cookie value using a group of codecs.
The codecs are tried in order. Multiple codecs are accepted to allow key rotation.
On error, may return a MultiError.
func DecodeMulti(name string, value string, dst interface{}, codecs ...Codec) errorfunc EncodeMulti
EncodeMulti encodes a cookie value using a group of codecs.
The codecs are tried in order. Multiple codecs are accepted to allow key rotation.
On error, may return a MultiError.
func EncodeMulti(name string, value interface{}, codecs ...Codec) (string, error)func GenerateRandomKey
GenerateRandomKey creates a random key with the given length in bytes. On failure, returns nil.
Note that keys created using `GenerateRandomKey()` are not automatically persisted. New keys will be created when the application is restarted, and previously issued cookies will not be able to be decoded.
Callers should explicitly check for the possibility of a nil return, treat it as a failure of the system random number generator, and not continue.
func GenerateRandomKey(length int) []byteTypes
type Codec
Codec defines an interface to encode and decode cookie values.
type Codec interface {
Encode(name string, value interface{}) (string, error)
Decode(name, value string, dst interface{}) error
}func CodecsFromPairs
CodecsFromPairs returns a slice of SecureCookie instances.
It is a convenience function to create a list of codecs for key rotation. Note that the generated Codecs will have the default options applied: callers should iterate over each Codec and type-assert the underlying *SecureCookie to change these.
Example:
codecs := lazycookie.CodecsFromPairs(
[]byte("new-hash-key"),
[]byte("new-block-key"),
[]byte("old-hash-key"),
[]byte("old-block-key"),
)
// Modify each instance.
for _, s := range codecs {
if cookie, ok := s.(*lazycookie.SecureCookie); ok {
cookie.MaxAge(86400 * 7)
cookie.SetSerializer(lazycookie.JSONEncoder{})
cookie.HashFunc(sha512.New512_256)
}
}
func CodecsFromPairs(keyPairs ...[]byte) []Codectype Error
Error is the interface of all errors returned by functions in this library.
type Error interface {
error
// IsUsage returns true for errors indicating the client code probably
// uses this library incorrectly. For example, the client may have
// failed to provide a valid hash key, or may have failed to configure
// the Serializer adequately for encoding value.
IsUsage() bool
// IsDecode returns true for errors indicating that a cookie could not
// be decoded and validated. Since cookies are usually untrusted
// user-provided input, errors of this type should be expected.
// Usually, the proper action is simply to reject the request.
IsDecode() bool
// IsInternal returns true for unexpected errors occurring in the
// securecookie implementation.
IsInternal() bool
// Cause, if it returns a non-nil value, indicates that this error was
// propagated from some underlying library. If this method returns nil,
// this error was raised directly by this library.
//
// Cause is provided principally for debugging/logging purposes; it is
// rare that application logic should perform meaningfully different
// logic based on Cause. See, for example, the caveats described on
// (MultiError).Cause().
Cause() error
}type GobEncoder
GobEncoder encodes cookie values using encoding/gob. This is the simplest encoder and can handle complex types via gob.Register.
type GobEncoder struct{}func (e GobEncoder) Deserialize
Deserialize decodes a value using gob.
func (e GobEncoder) Deserialize(src []byte, dst interface{}) errorfunc (e GobEncoder) Serialize
Serialize encodes a value using gob.
func (e GobEncoder) Serialize(src interface{}) ([]byte, error)type JSONEncoder
JSONEncoder encodes cookie values using encoding/json. Users who wish to encode complex types need to satisfy the json.Marshaller and json.Unmarshaller interfaces.
type JSONEncoder struct{}func (e JSONEncoder) Deserialize
Deserialize decodes a value using encoding/json.
func (e JSONEncoder) Deserialize(src []byte, dst interface{}) errorfunc (e JSONEncoder) Serialize
Serialize encodes a value using encoding/json.
func (e JSONEncoder) Serialize(src interface{}) ([]byte, error)type MultiError
MultiError groups multiple errors.
type MultiError []errorfunc (m MultiError) Cause
Cause returns nil for MultiError; there is no unique underlying cause in the general case.
Note: we could conceivably return a non-nil Cause only when there is exactly one child error with a Cause. However, it would be brittle for client code to rely on the arity of causes inside a MultiError, so we have opted not to provide this functionality. Clients which really wish to access the Causes of the underlying errors are free to iterate through the errors themselves.
func (m MultiError) Cause() errorfunc (m MultiError) Error
func (m MultiError) Error() stringfunc (m MultiError) IsDecode
func (m MultiError) IsDecode() boolfunc (m MultiError) IsInternal
func (m MultiError) IsInternal() boolfunc (m MultiError) IsUsage
func (m MultiError) IsUsage() booltype NopEncoder
NopEncoder does not encode cookie values, and instead simply accepts a []byte (as an interface{}) and returns a []byte. This is particularly useful when you encoding an object upstream and do not wish to re-encode it.
type NopEncoder struct{}func (e NopEncoder) Deserialize
Deserialize passes a []byte through as-is.
func (e NopEncoder) Deserialize(src []byte, dst interface{}) errorfunc (e NopEncoder) Serialize
Serialize passes a []byte through as-is.
func (e NopEncoder) Serialize(src interface{}) ([]byte, error)type SecureCookie
SecureCookie encodes and decodes authenticated and optionally encrypted cookie values.
type SecureCookie struct {
// contains filtered or unexported fields
}func New
New returns a new SecureCookie.
hashKey is required, used to authenticate values using HMAC. Create it using GenerateRandomKey(). It is recommended to use a key with 32 or 64 bytes.
blockKey is optional, used to encrypt values. Create it using GenerateRandomKey(). The key length must correspond to the key size of the encryption algorithm. For AES, used by default, valid lengths are 16, 24, or 32 bytes to select AES-128, AES-192, or AES-256. The default encoder used for cookie serialization is encoding/gob.
Note that keys created using GenerateRandomKey() are not automatically persisted. New keys will be created when the application is restarted, and previously issued cookies will not be able to be decoded.
func New(hashKey, blockKey []byte) *SecureCookiefunc (s *SecureCookie) BlockFunc
BlockFunc sets the encryption function used to create a cipher.Block.
Default is crypto/aes.New.
func (s *SecureCookie) BlockFunc(f func([]byte) (cipher.Block, error)) *SecureCookiefunc (s *SecureCookie) Decode
Decode decodes a cookie value.
It decodes, verifies a message authentication code, optionally decrypts and finally deserializes the value.
The name argument is the cookie name. It must be the same name used when it was stored. The value argument is the encoded cookie value. The dst argument is where the cookie will be decoded. It must be a pointer.
func (s *SecureCookie) Decode(name, value string, dst interface{}) errorfunc (s *SecureCookie) Encode
Encode encodes a cookie value.
It serializes, optionally encrypts, signs with a message authentication code, and finally encodes the value.
The name argument is the cookie name. It is stored with the encoded value. The value argument is the value to be encoded. It can be any value that can be encoded using the currently selected serializer; see SetSerializer().
It is the client's responsibility to ensure that value, when encoded using the current serialization/encryption settings on s and then base64-encoded, is shorter than the maximum permissible length.
func (s *SecureCookie) Encode(name string, value interface{}) (string, error)func (s *SecureCookie) HashFunc
HashFunc sets the hash function used to create HMAC.
Default is crypto/sha256.New.
func (s *SecureCookie) HashFunc(f func() hash.Hash) *SecureCookiefunc (s *SecureCookie) MaxAge
MaxAge restricts the maximum age, in seconds, for the cookie value.
Default is 86400 * 30. Set it to 0 for no restriction.
func (s *SecureCookie) MaxAge(value int) *SecureCookiefunc (s *SecureCookie) MaxLength
MaxLength restricts the maximum length, in bytes, for the cookie value.
Default is 4096, which is the maximum value accepted by Internet Explorer.
func (s *SecureCookie) MaxLength(value int) *SecureCookiefunc (s *SecureCookie) MinAge
MinAge restricts the minimum age, in seconds, for the cookie value.
Default is 0 (no restriction).
func (s *SecureCookie) MinAge(value int) *SecureCookiefunc (s *SecureCookie) SetSerializer
Encoding sets the encoding/serialization method for cookies.
Default is encoding/gob. To encode special structures using encoding/gob, they must be registered first using gob.Register().
func (s *SecureCookie) SetSerializer(sz Serializer) *SecureCookietype Serializer
Serializer provides an interface for providing custom serializers for cookie values.
type Serializer interface {
Serialize(src interface{}) ([]byte, error)
Deserialize(src []byte, dst interface{}) error
}
Package lazycookie encodes and decodes authenticated and optionally encrypted cookie values.
Secure cookies can't be forged, because their values are validated using HMAC. When encrypted, the content is also inaccessible to malicious eyes.
To use it, first create a new SecureCookie instance:
var hashKey = []byte("very-secret") var blockKey = []byte("a-lot-secret") var s = lazycookie.New(hashKey, blockKey)The hashKey is required, used to authenticate the cookie value using HMAC. It is recommended to use a key with 32 or 64 bytes.
The blockKey is optional, used to encrypt the cookie value -- set it to nil to not use encryption. If set, the length must correspond to the block size of the encryption algorithm. For AES, used by default, valid lengths are 16, 24, or 32 bytes to select AES-128, AES-192, or AES-256.
Strong keys can be created using the convenience function GenerateRandomKey().
Once a SecureCookie instance is set, use it to encode a cookie value:
func SetCookieHandler(w http.ResponseWriter, r *http.Request) { value := map[string]string{ "foo": "bar", } if encoded, err := s.Encode("cookie-name", value); err == nil { cookie := &http.Cookie{ Name: "cookie-name", Value: encoded, Path: "/", } http.SetCookie(w, cookie) } }Later, use the same SecureCookie instance to decode and validate a cookie value:
func ReadCookieHandler(w http.ResponseWriter, r *http.Request) { if cookie, err := r.Cookie("cookie-name"); err == nil { value := make(map[string]string) if err = s2.Decode("cookie-name", cookie.Value, &value); err == nil { fmt.Fprintf(w, "The value of foo is %q", value["foo"]) } } }We stored a map[string]string, but secure cookies can hold any value that can be encoded using encoding/gob. To store custom types, they must be registered first using gob.Register(). For basic types this is not needed; it works out of the box.