claims.go

/*-
 * Copyright 2016 Zbigniew Mandziejewicz
 * Copyright 2016 Square, Inc.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package jwt

import (
	"strconv"
	"time"

	"github.com/go-jose/go-jose/v3/json"
)

// Claims represents public claim values (as specified in RFC 7519).
type Claims struct {
	Issuer    string       `json:"iss,omitempty"`
	Subject   string       `json:"sub,omitempty"`
	Audience  Audience     `json:"aud,omitempty"`
	Expiry    *NumericDate `json:"exp,omitempty"`
	NotBefore *NumericDate `json:"nbf,omitempty"`
	IssuedAt  *NumericDate `json:"iat,omitempty"`
	ID        string       `json:"jti,omitempty"`
}

// NumericDate represents date and time as the number of seconds since the
// epoch, ignoring leap seconds. Non-integer values can be represented
// in the serialized format, but we round to the nearest second.
// See RFC7519 Section 2: https://tools.ietf.org/html/rfc7519#section-2
type NumericDate int64

// NewNumericDate constructs NumericDate from time.Time value.
func NewNumericDate(t time.Time) *NumericDate {
	if t.IsZero() {
		return nil
	}

	// While RFC 7519 technically states that NumericDate values may be
	// non-integer values, we don't bother serializing timestamps in
	// claims with sub-second accurancy and just round to the nearest
	// second instead. Not convined sub-second accuracy is useful here.
	out := NumericDate(t.Unix())
	return &out
}

// MarshalJSON serializes the given NumericDate into its JSON representation.
func (n NumericDate) MarshalJSON() ([]byte, error) {
	return []byte(strconv.FormatInt(int64(n), 10)), nil
}

// UnmarshalJSON reads a date from its JSON representation.
func (n *NumericDate) UnmarshalJSON(b []byte) error {
	s := string(b)

	f, err := strconv.ParseFloat(s, 64)
	if err != nil {
		return ErrUnmarshalNumericDate
	}

	*n = NumericDate(f)
	return nil
}

// Time returns time.Time representation of NumericDate.
func (n *NumericDate) Time() time.Time {
	if n == nil {
		return time.Time{}
	}
	return time.Unix(int64(*n), 0)
}

// Audience represents the recipients that the token is intended for.
type Audience []string

// UnmarshalJSON reads an audience from its JSON representation.
func (s *Audience) UnmarshalJSON(b []byte) error {
	var v interface{}
	if err := json.Unmarshal(b, &v); err != nil {
		return err
	}

	switch v := v.(type) {
	case string:
		*s = []string{v}
	case []interface{}:
		a := make([]string, len(v))
		for i, e := range v {
			s, ok := e.(string)
			if !ok {
				return ErrUnmarshalAudience
			}
			a[i] = s
		}
		*s = a
	default:
		return ErrUnmarshalAudience
	}

	return nil
}

// MarshalJSON converts audience to json representation.
func (s Audience) MarshalJSON() ([]byte, error) {
	if len(s) == 1 {
		return json.Marshal(s[0])
	}
	return json.Marshal([]string(s))
}

// Contains checks whether a given string is included in the Audience
func (s Audience) Contains(v string) bool {
	for _, a := range s {
		if a == v {
			return true
		}
	}
	return false
}