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jwt.go
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jwt.go
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// Package token wraps jwt-go library and provides higher level abstraction to work with JWT.
package token
import (
"encoding/json"
"fmt"
"net/http"
"strings"
"time"
"github.com/golang-jwt/jwt"
)
// Service wraps jwt operations
// supports both header and cookie tokens
type Service struct {
Opts
}
// Claims stores user info for token and state & from from login
type Claims struct {
jwt.StandardClaims
User *User `json:"user,omitempty"` // user info
SessionOnly bool `json:"sess_only,omitempty"`
Handshake *Handshake `json:"handshake,omitempty"` // used for oauth handshake
NoAva bool `json:"no-ava,omitempty"` // disable avatar, always use identicon
}
// Handshake used for oauth handshake
type Handshake struct {
State string `json:"state,omitempty"`
From string `json:"from,omitempty"`
ID string `json:"id,omitempty"`
}
const (
// default names for cookies and headers
defaultJWTCookieName = "JWT"
defaultJWTCookieDomain = ""
defaultJWTHeaderKey = "X-JWT"
defaultXSRFCookieName = "XSRF-TOKEN"
defaultXSRFHeaderKey = "X-XSRF-TOKEN"
defaultIssuer = "go-pkgz/auth"
defaultTokenDuration = time.Minute * 15
defaultCookieDuration = time.Hour * 24 * 31
defaultTokenQuery = "token"
)
// Opts holds constructor params
type Opts struct {
SecretReader Secret
ClaimsUpd ClaimsUpdater
SecureCookies bool
TokenDuration time.Duration
CookieDuration time.Duration
DisableXSRF bool
DisableIAT bool // disable IssuedAt claim
// optional (custom) names for cookies and headers
JWTCookieName string
JWTCookieDomain string
JWTHeaderKey string
XSRFCookieName string
XSRFHeaderKey string
JWTQuery string
AudienceReader Audience // allowed aud values
Issuer string // optional value for iss claim, usually application name
AudSecrets bool // uses different secret for differed auds. important: adds pre-parsing of unverified token
SendJWTHeader bool // if enabled send JWT as a header instead of cookie
SameSite http.SameSite // define a cookie attribute making it impossible for the browser to send this cookie cross-site
}
// NewService makes JWT service
func NewService(opts Opts) *Service {
res := Service{Opts: opts}
setDefault := func(fld *string, def string) {
if *fld == "" {
*fld = def
}
}
setDefault(&res.JWTCookieName, defaultJWTCookieName)
setDefault(&res.JWTHeaderKey, defaultJWTHeaderKey)
setDefault(&res.XSRFCookieName, defaultXSRFCookieName)
setDefault(&res.XSRFHeaderKey, defaultXSRFHeaderKey)
setDefault(&res.JWTQuery, defaultTokenQuery)
setDefault(&res.Issuer, defaultIssuer)
setDefault(&res.JWTCookieDomain, defaultJWTCookieDomain)
if opts.TokenDuration == 0 {
res.TokenDuration = defaultTokenDuration
}
if opts.CookieDuration == 0 {
res.CookieDuration = defaultCookieDuration
}
return &res
}
// Token makes token with claims
func (j *Service) Token(claims Claims) (string, error) {
// make token for allowed aud values only, rejects others
// update claims with ClaimsUpdFunc defined by consumer
if j.ClaimsUpd != nil {
claims = j.ClaimsUpd.Update(claims)
}
token := jwt.NewWithClaims(jwt.SigningMethodHS256, claims)
if j.SecretReader == nil {
return "", fmt.Errorf("secret reader not defined")
}
if err := j.checkAuds(&claims, j.AudienceReader); err != nil {
return "", fmt.Errorf("aud rejected: %w", err)
}
secret, err := j.SecretReader.Get(claims.Audience) // get secret via consumer defined SecretReader
if err != nil {
return "", fmt.Errorf("can't get secret: %w", err)
}
tokenString, err := token.SignedString([]byte(secret))
if err != nil {
return "", fmt.Errorf("can't sign token: %w", err)
}
return tokenString, nil
}
// Parse token string and verify. Not checking for expiration
func (j *Service) Parse(tokenString string) (Claims, error) {
parser := jwt.Parser{SkipClaimsValidation: true} // allow parsing of expired tokens
if j.SecretReader == nil {
return Claims{}, fmt.Errorf("secret reader not defined")
}
aud := "ignore"
if j.AudSecrets {
var err error
aud, err = j.aud(tokenString)
if err != nil {
return Claims{}, fmt.Errorf("can't retrieve audience from the token")
}
}
secret, err := j.SecretReader.Get(aud)
if err != nil {
return Claims{}, fmt.Errorf("can't get secret: %w", err)
}
token, err := parser.ParseWithClaims(tokenString, &Claims{}, func(token *jwt.Token) (interface{}, error) {
if _, ok := token.Method.(*jwt.SigningMethodHMAC); !ok {
return nil, fmt.Errorf("unexpected signing method: %v", token.Header["alg"])
}
return []byte(secret), nil
})
if err != nil {
return Claims{}, fmt.Errorf("can't parse token: %w", err)
}
claims, ok := token.Claims.(*Claims)
if !ok {
return Claims{}, fmt.Errorf("invalid token")
}
if err = j.checkAuds(claims, j.AudienceReader); err != nil {
return Claims{}, fmt.Errorf("aud rejected: %w", err)
}
return *claims, j.validate(claims)
}
// aud pre-parse token and extracts aud from the claim
// important! this step ignores token verification, should not be used for any validations
func (j *Service) aud(tokenString string) (string, error) {
parser := jwt.Parser{}
token, _, err := parser.ParseUnverified(tokenString, &Claims{})
if err != nil {
return "", fmt.Errorf("can't pre-parse token: %w", err)
}
claims, ok := token.Claims.(*Claims)
if !ok {
return "", fmt.Errorf("invalid token")
}
if strings.TrimSpace(claims.Audience) == "" {
return "", fmt.Errorf("empty aud")
}
return claims.Audience, nil
}
func (j *Service) validate(claims *Claims) error {
cerr := claims.Valid()
if cerr == nil {
return nil
}
if e, ok := cerr.(*jwt.ValidationError); ok {
if e.Errors == jwt.ValidationErrorExpired {
return nil // allow expired tokens
}
}
return cerr
}
// Set creates token cookie with xsrf cookie and put it to ResponseWriter
// accepts claims and sets expiration if none defined. permanent flag means long-living cookie,
// false makes it session only.
func (j *Service) Set(w http.ResponseWriter, claims Claims) (Claims, error) {
if claims.ExpiresAt == 0 {
claims.ExpiresAt = time.Now().Add(j.TokenDuration).Unix()
}
if claims.Issuer == "" {
claims.Issuer = j.Issuer
}
if !j.DisableIAT {
claims.IssuedAt = time.Now().Unix()
}
tokenString, err := j.Token(claims)
if err != nil {
return Claims{}, fmt.Errorf("failed to make token token: %w", err)
}
if j.SendJWTHeader {
w.Header().Set(j.JWTHeaderKey, tokenString)
return claims, nil
}
cookieExpiration := 0 // session cookie
if !claims.SessionOnly && claims.Handshake == nil {
cookieExpiration = int(j.CookieDuration.Seconds())
}
jwtCookie := http.Cookie{Name: j.JWTCookieName, Value: tokenString, HttpOnly: true, Path: "/", Domain: j.JWTCookieDomain,
MaxAge: cookieExpiration, Secure: j.SecureCookies, SameSite: j.SameSite}
http.SetCookie(w, &jwtCookie)
xsrfCookie := http.Cookie{Name: j.XSRFCookieName, Value: claims.Id, HttpOnly: false, Path: "/", Domain: j.JWTCookieDomain,
MaxAge: cookieExpiration, Secure: j.SecureCookies, SameSite: j.SameSite}
http.SetCookie(w, &xsrfCookie)
return claims, nil
}
// Get token from url, header or cookie
// if cookie used, verify xsrf token to match
func (j *Service) Get(r *http.Request) (Claims, string, error) {
fromCookie := false
tokenString := ""
// try to get from "token" query param
if tkQuery := r.URL.Query().Get(j.JWTQuery); tkQuery != "" {
tokenString = tkQuery
}
// try to get from JWT header
if tokenHeader := r.Header.Get(j.JWTHeaderKey); tokenHeader != "" && tokenString == "" {
tokenString = tokenHeader
}
// try to get from JWT cookie
if tokenString == "" {
fromCookie = true
jc, err := r.Cookie(j.JWTCookieName)
if err != nil {
return Claims{}, "", fmt.Errorf("token cookie was not presented: %w", err)
}
tokenString = jc.Value
}
claims, err := j.Parse(tokenString)
if err != nil {
return Claims{}, "", fmt.Errorf("failed to get token: %w", err)
}
// promote claim's aud to User.Audience
if claims.User != nil {
claims.User.Audience = claims.Audience
}
if !fromCookie && j.IsExpired(claims) {
return Claims{}, "", fmt.Errorf("token expired")
}
if j.DisableXSRF {
return claims, tokenString, nil
}
if fromCookie && claims.User != nil {
xsrf := r.Header.Get(j.XSRFHeaderKey)
if claims.Id != xsrf {
return Claims{}, "", fmt.Errorf("xsrf mismatch")
}
}
return claims, tokenString, nil
}
// IsExpired returns true if claims expired
func (j *Service) IsExpired(claims Claims) bool {
return !claims.VerifyExpiresAt(time.Now().Unix(), true)
}
// Reset token's cookies
func (j *Service) Reset(w http.ResponseWriter) {
jwtCookie := http.Cookie{Name: j.JWTCookieName, Value: "", HttpOnly: false, Path: "/", Domain: j.JWTCookieDomain,
MaxAge: -1, Expires: time.Unix(0, 0), Secure: j.SecureCookies, SameSite: j.SameSite}
http.SetCookie(w, &jwtCookie)
xsrfCookie := http.Cookie{Name: j.XSRFCookieName, Value: "", HttpOnly: false, Path: "/", Domain: j.JWTCookieDomain,
MaxAge: -1, Expires: time.Unix(0, 0), Secure: j.SecureCookies, SameSite: j.SameSite}
http.SetCookie(w, &xsrfCookie)
}
// checkAuds verifies if claims.Audience in the list of allowed by audReader
func (j *Service) checkAuds(claims *Claims, audReader Audience) error {
if audReader == nil { // lack of any allowed means any
return nil
}
auds, err := audReader.Get()
if err != nil {
return fmt.Errorf("failed to get auds: %w", err)
}
for _, a := range auds {
if strings.EqualFold(a, claims.Audience) {
return nil
}
}
return fmt.Errorf("aud %q not allowed", claims.Audience)
}
func (c Claims) String() string {
b, err := json.Marshal(c)
if err != nil {
return fmt.Sprintf("%+v %+v", c.StandardClaims, c.User)
}
return string(b)
}
// Secret defines interface returning secret key for given id (aud)
type Secret interface {
Get(aud string) (string, error) // aud matching is optional. Implementation may decide if supported or ignored
}
// SecretFunc type is an adapter to allow the use of ordinary functions as Secret. If f is a function
// with the appropriate signature, SecretFunc(f) is a Handler that calls f.
type SecretFunc func(aud string) (string, error)
// Get calls f()
func (f SecretFunc) Get(aud string) (string, error) {
return f(aud)
}
// ClaimsUpdater defines interface adding extras to claims
type ClaimsUpdater interface {
Update(claims Claims) Claims
}
// ClaimsUpdFunc type is an adapter to allow the use of ordinary functions as ClaimsUpdater. If f is a function
// with the appropriate signature, ClaimsUpdFunc(f) is a Handler that calls f.
type ClaimsUpdFunc func(claims Claims) Claims
// Update calls f(id)
func (f ClaimsUpdFunc) Update(claims Claims) Claims {
return f(claims)
}
// Validator defines interface to accept o reject claims with consumer defined logic
// It works with valid token and allows to reject some, based on token match or user's fields
type Validator interface {
Validate(token string, claims Claims) bool
}
// ValidatorFunc type is an adapter to allow the use of ordinary functions as Validator. If f is a function
// with the appropriate signature, ValidatorFunc(f) is a Validator that calls f.
type ValidatorFunc func(token string, claims Claims) bool
// Validate calls f(id)
func (f ValidatorFunc) Validate(token string, claims Claims) bool {
return f(token, claims)
}
// Audience defines interface returning list of allowed audiences
type Audience interface {
Get() ([]string, error)
}
// AudienceFunc type is an adapter to allow the use of ordinary functions as Audience.
type AudienceFunc func() ([]string, error)
// Get calls f()
func (f AudienceFunc) Get() ([]string, error) {
return f()
}