jwt

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 Go to latest Published: Sep 14, 2016 License: MIT, MIT Imports: 17 Imported by: 0

README

A go (or 'golang' for search engine friendliness) implementation of JSON Web Tokens

Build Status

BREAKING CHANGES:* Version 3.0.0 is here. It includes a lot of changes including a few that break the API. We've tried to break as few things as possible, so there should just be a few type signature changes. A full list of breaking changes is available in VERSION_HISTORY.md. See MIGRATION_GUIDE.md for more information on updating your code.

NOTICE: A vulnerability in JWT was recently published. As this library doesn't force users to validate the alg is what they expected, it's possible your usage is effected. There will be an update soon to remedy this, and it will likey require backwards-incompatible changes to the API. In the short term, please make sure your implementation verifies the alg is what you expect.

What the heck is a JWT?

JWT.io has a great introduction to JSON Web Tokens.

In short, it's a signed JSON object that does something useful (for example, authentication). It's commonly used for Bearer tokens in Oauth 2. A token is made of three parts, separated by .'s. The first two parts are JSON objects, that have been base64url encoded. The last part is the signature, encoded the same way.

The first part is called the header. It contains the necessary information for verifying the last part, the signature. For example, which encryption method was used for signing and what key was used.

The part in the middle is the interesting bit. It's called the Claims and contains the actual stuff you care about. Refer to the RFC for information about reserved keys and the proper way to add your own.

What's in the box?

This library supports the parsing and verification as well as the generation and signing of JWTs. Current supported signing algorithms are HMAC SHA, RSA, RSA-PSS, and ECDSA, though hooks are present for adding your own.

Examples

See the project documentation for examples of usage:

Extensions

This library publishes all the necessary components for adding your own signing methods. Simply implement the SigningMethod interface and register a factory method using RegisterSigningMethod.

Here's an example of an extension that integrates with the Google App Engine signing tools: https://github.com/someone1/gcp-jwt-go

Compliance

This library was last reviewed to comply with RTF 7519 dated May 2015 with a few notable differences:

  • In order to protect against accidental use of Unsecured JWTs, tokens using alg=none will only be accepted if the constant jwt.UnsafeAllowNoneSignatureType is provided as the key.

Project Status & Versioning

This library is considered production ready. Feedback and feature requests are appreciated. The API should be considered stable. There should be very few backwards-incompatible changes outside of major version updates (and only with good reason).

This project uses Semantic Versioning 2.0.0. Accepted pull requests will land on master. Periodically, versions will be tagged from master. You can find all the releases on the project releases page.

While we try to make it obvious when we make breaking changes, there isn't a great mechanism for pushing announcements out to users. You may want to use this alternative package include: gopkg.in/dgrijalva/jwt-go.v2. It will do the right thing WRT semantic versioning.

Usage Tips

Signing vs Encryption

A token is simply a JSON object that is signed by its author. this tells you exactly two things about the data:

  • The author of the token was in the possession of the signing secret
  • The data has not been modified since it was signed

It's important to know that JWT does not provide encryption, which means anyone who has access to the token can read its contents. If you need to protect (encrypt) the data, there is a companion spec, JWE, that provides this functionality. JWE is currently outside the scope of this library.

Choosing a Signing Method

There are several signing methods available, and you should probably take the time to learn about the various options before choosing one. The principal design decision is most likely going to be symmetric vs asymmetric.

Symmetric signing methods, such as HSA, use only a single secret. This is probably the simplest signing method to use since any []byte can be used as a valid secret. They are also slightly computationally faster to use, though this rarely is enough to matter. Symmetric signing methods work the best when both producers and consumers of tokens are trusted, or even the same system. Since the same secret is used to both sign and validate tokens, you can't easily distribute the key for validation.

Asymmetric signing methods, such as RSA, use different keys for signing and verifying tokens. This makes it possible to produce tokens with a private key, and allow any consumer to access the public key for verification.

JWT and OAuth

It's worth mentioning that OAuth and JWT are not the same thing. A JWT token is simply a signed JSON object. It can be used anywhere such a thing is useful. There is some confusion, though, as JWT is the most common type of bearer token used in OAuth2 authentication.

Without going too far down the rabbit hole, here's a description of the interaction of these technologies:

  • OAuth is a protocol for allowing an identity provider to be separate from the service a user is logging in to. For example, whenever you use Facebook to log into a different service (Yelp, Spotify, etc), you are using OAuth.
  • OAuth defines several options for passing around authentication data. One popular method is called a "bearer token". A bearer token is simply a string that should only be held by an authenticated user. Thus, simply presenting this token proves your identity. You can probably derive from here why a JWT might make a good bearer token.
  • Because bearer tokens are used for authentication, it's important they're kept secret. This is why transactions that use bearer tokens typically happen over SSL.

More

Documentation can be found on godoc.org.

The command line utility included in this project (cmd/jwt) provides a straightforward example of token creation and parsing as well as a useful tool for debugging your own integration. You'll also find several implementation examples in to documentation.

Documentation

Overview

Package jwt is a Go implementation of JSON Web Tokens: http://self-issued.info/docs/draft-jones-json-web-token.html

See README.md for more info.

Index

Constants

View Source 
const (
	ValidationErrorMalformed        uint32 = 1 << iota // Token is malformed
	ValidationErrorUnverifiable                        // Token could not be verified because of signing problems
	ValidationErrorSignatureInvalid                    // Signature validation failed

	// Standard Claim validation errors
	ValidationErrorAudience      // AUD validation failed
	ValidationErrorExpired       // EXP validation failed
	ValidationErrorIssuedAt      // IAT validation failed
	ValidationErrorIssuer        // ISS validation failed
	ValidationErrorNotValidYet   // NBF validation failed
	ValidationErrorId            // JTI validation failed
	ValidationErrorClaimsInvalid // Generic claims validation error
)

The errors that might occur when parsing and validating a token

View Source 
const UnsafeAllowNoneSignatureType unsafeNoneMagicConstant = "none signing method allowed"

Variables

View Source 
var (
	ErrNotECPublicKey  = errors.New("Key is not a valid ECDSA public key")
	ErrNotECPrivateKey = errors.New("Key is not a valid ECDSA private key")
)
View Source 
var (
	ErrInvalidKey      = errors.New("key is invalid")
	ErrInvalidKeyType  = errors.New("key is of invalid type")
	ErrHashUnavailable = errors.New("the requested hash function is unavailable")
)

Error constants

View Source 
var (
	ErrKeyMustBePEMEncoded = errors.New("Invalid Key: Key must be PEM encoded PKCS1 or PKCS8 private key")
	ErrNotRSAPrivateKey    = errors.New("Key is not a valid RSA private key")
	ErrNotRSAPublicKey     = errors.New("Key is not a valid RSA public key")
)
View Source 
var (
	// Sadly this is missing from crypto/ecdsa compared to crypto/rsa
	ErrECDSAVerification = errors.New("crypto/ecdsa: verification error")
)
View Source 
var NoneSignatureTypeDisallowedError error
View Source 
var SigningMethodNone *signingMethodNone

Implements the none signing method. This is required by the spec but you probably should never use it.

View Source 
var TimeFunc = time.Now

TimeFunc provides the current time when parsing token to validate "exp" claim (expiration time). You can override it to use another time value. This is useful for testing or if your server uses a different time zone than your tokens.

Functions

func DecodeSegment 

func DecodeSegment(seg string) ([]byte, error)

Decode JWT specific base64url encoding with padding stripped

func EncodeSegment 

func EncodeSegment(seg []byte) string

Encode JWT specific base64url encoding with padding stripped

func ParseECPrivateKeyFromPEM 

func ParseECPrivateKeyFromPEM(key []byte) (*ecdsa.PrivateKey, error)

Parse PEM encoded Elliptic Curve Private Key Structure

func ParseECPublicKeyFromPEM 

func ParseECPublicKeyFromPEM(key []byte) (*ecdsa.PublicKey, error)

Parse PEM encoded PKCS1 or PKCS8 public key

func ParseRSAPrivateKeyFromPEM 

func ParseRSAPrivateKeyFromPEM(key []byte) (*rsa.PrivateKey, error)

Parse PEM encoded PKCS1 or PKCS8 private key

func ParseRSAPublicKeyFromPEM 

func ParseRSAPublicKeyFromPEM(key []byte) (*rsa.PublicKey, error)

Parse PEM encoded PKCS1 or PKCS8 public key

func RegisterSigningMethod 

func RegisterSigningMethod(alg string, f func() SigningMethod)

Register the "alg" name and a factory function for signing method. This is typically done during init() in the method's implementation

Types

type Claims 

type Claims interface {
	Valid() error
}

For a type to be a Claims object, it must just have a Valid method that determines if the token is invalid for any supported reason

type Keyfunc 

type Keyfunc func(*Token) (interface{}, error)

Parse methods use this callback function to supply the key for verification. The function receives the parsed, but unverified Token. This allows you to use properties in the Header of the token (such as `kid`) to identify which key to use.

type MapClaims 

type MapClaims map[string]interface{}

Claims type that uses the map[string]interface{} for JSON decoding This is the default claims type if you don't supply one

func (MapClaims) Valid 

func (m MapClaims) Valid() error

Validates time based claims "exp, iat, nbf". There is no accounting for clock skew. As well, if any of the above claims are not in the token, it will still be considered a valid claim.

func (MapClaims) VerifyAudience 

func (m MapClaims) VerifyAudience(cmp string, req bool) bool

Compares the aud claim against cmp. If required is false, this method will return true if the value matches or is unset

func (MapClaims) VerifyExpiresAt 

func (m MapClaims) VerifyExpiresAt(cmp int64, req bool) bool

Compares the exp claim against cmp. If required is false, this method will return true if the value matches or is unset

func (MapClaims) VerifyIssuedAt 

func (m MapClaims) VerifyIssuedAt(cmp int64, req bool) bool

Compares the iat claim against cmp. If required is false, this method will return true if the value matches or is unset

func (MapClaims) VerifyIssuer 

func (m MapClaims) VerifyIssuer(cmp string, req bool) bool

Compares the iss claim against cmp. If required is false, this method will return true if the value matches or is unset

func (MapClaims) VerifyNotBefore 

func (m MapClaims) VerifyNotBefore(cmp int64, req bool) bool

Compares the nbf claim against cmp. If required is false, this method will return true if the value matches or is unset

type Parser 

type Parser struct {
	ValidMethods  []string // If populated, only these methods will be considered valid
	UseJSONNumber bool     // Use JSON Number format in JSON decoder
}

func (*Parser) Parse 

func (p *Parser) Parse(tokenString string, keyFunc Keyfunc) (*Token, error)

Parse, validate, and return a token. keyFunc will receive the parsed token and should return the key for validating. If everything is kosher, err will be nil

func (*Parser) ParseWithClaims 

func (p *Parser) ParseWithClaims(tokenString string, claims Claims, keyFunc Keyfunc) (*Token, error)

type SigningMethod 

type SigningMethod interface {
	Verify(signingString, signature string, key interface{}) error // Returns nil if signature is valid
	Sign(signingString string, key interface{}) (string, error)    // Returns encoded signature or error
	Alg() string                                                   // returns the alg identifier for this method (example: 'HS256')
}

Implement SigningMethod to add new methods for signing or verifying tokens.

func GetSigningMethod 

func GetSigningMethod(alg string) (method SigningMethod)

Get a signing method from an "alg" string

type SigningMethodECDSA 

type SigningMethodECDSA struct {
	Name      string
	Hash      crypto.Hash
	KeySize   int
	CurveBits int
}

Implements the ECDSA family of signing methods signing methods 

var (
	SigningMethodES256 *SigningMethodECDSA
	SigningMethodES384 *SigningMethodECDSA
	SigningMethodES512 *SigningMethodECDSA
)

Specific instances for EC256 and company

func (*SigningMethodECDSA) Alg 

func (m *SigningMethodECDSA) Alg() string

func (*SigningMethodECDSA) Sign 

func (m *SigningMethodECDSA) Sign(signingString string, key interface{}) (string, error)

Implements the Sign method from SigningMethod For this signing method, key must be an ecdsa.PrivateKey struct

func (*SigningMethodECDSA) Verify 

func (m *SigningMethodECDSA) Verify(signingString, signature string, key interface{}) error

Implements the Verify method from SigningMethod For this verify method, key must be an ecdsa.PublicKey struct

type SigningMethodHMAC 

type SigningMethodHMAC struct {
	Name string
	Hash crypto.Hash
}

Implements the HMAC-SHA family of signing methods signing methods 

var (
	SigningMethodHS256  *SigningMethodHMAC
	SigningMethodHS384  *SigningMethodHMAC
	SigningMethodHS512  *SigningMethodHMAC
	ErrSignatureInvalid = errors.New("signature is invalid")
)

Specific instances for HS256 and company

func (*SigningMethodHMAC) Alg 

func (m *SigningMethodHMAC) Alg() string

func (*SigningMethodHMAC) Sign 

func (m *SigningMethodHMAC) Sign(signingString string, key interface{}) (string, error)

Implements the Sign method from SigningMethod for this signing method. Key must be []byte

func (*SigningMethodHMAC) Verify 

func (m *SigningMethodHMAC) Verify(signingString, signature string, key interface{}) error

Verify the signature of HSXXX tokens. Returns nil if the signature is valid.

type SigningMethodRSA 

type SigningMethodRSA struct {
	Name string
	Hash crypto.Hash
}

Implements the RSA family of signing methods signing methods 

var (
	SigningMethodRS256 *SigningMethodRSA
	SigningMethodRS384 *SigningMethodRSA
	SigningMethodRS512 *SigningMethodRSA
)

Specific instances for RS256 and company

func (*SigningMethodRSA) Alg 

func (m *SigningMethodRSA) Alg() string

func (*SigningMethodRSA) Sign 

func (m *SigningMethodRSA) Sign(signingString string, key interface{}) (string, error)

Implements the Sign method from SigningMethod For this signing method, must be an rsa.PrivateKey structure.

func (*SigningMethodRSA) Verify 

func (m *SigningMethodRSA) Verify(signingString, signature string, key interface{}) error

Implements the Verify method from SigningMethod For this signing method, must be an rsa.PublicKey structure.

type SigningMethodRSAPSS 

type SigningMethodRSAPSS struct {
	*SigningMethodRSA
	Options *rsa.PSSOptions
}

Implements the RSAPSS family of signing methods signing methods 

var (
	SigningMethodPS256 *SigningMethodRSAPSS
	SigningMethodPS384 *SigningMethodRSAPSS
	SigningMethodPS512 *SigningMethodRSAPSS
)

Specific instances for RS/PS and company

func (*SigningMethodRSAPSS) Sign 

func (m *SigningMethodRSAPSS) Sign(signingString string, key interface{}) (string, error)

Implements the Sign method from SigningMethod For this signing method, key must be an rsa.PrivateKey struct

func (*SigningMethodRSAPSS) Verify 

func (m *SigningMethodRSAPSS) Verify(signingString, signature string, key interface{}) error

Implements the Verify method from SigningMethod For this verify method, key must be an rsa.PublicKey struct

type StandardClaims 

type StandardClaims struct {
	Audience  string `json:"aud,omitempty"`
	ExpiresAt int64  `json:"exp,omitempty"`
	Id        string `json:"jti,omitempty"`
	IssuedAt  int64  `json:"iat,omitempty"`
	Issuer    string `json:"iss,omitempty"`
	NotBefore int64  `json:"nbf,omitempty"`
	Subject   string `json:"sub,omitempty"`
}

Structured version of Claims Section, as referenced at https://tools.ietf.org/html/rfc7519#section-4.1 See examples for how to use this with your own claim types

func (StandardClaims) Valid 

func (c StandardClaims) Valid() error

Validates time based claims "exp, iat, nbf". There is no accounting for clock skew. As well, if any of the above claims are not in the token, it will still be considered a valid claim.

func (*StandardClaims) VerifyAudience 

func (c *StandardClaims) VerifyAudience(cmp string, req bool) bool

Compares the aud claim against cmp. If required is false, this method will return true if the value matches or is unset

func (*StandardClaims) VerifyExpiresAt 

func (c *StandardClaims) VerifyExpiresAt(cmp int64, req bool) bool

Compares the exp claim against cmp. If required is false, this method will return true if the value matches or is unset

func (*StandardClaims) VerifyIssuedAt 

func (c *StandardClaims) VerifyIssuedAt(cmp int64, req bool) bool

Compares the iat claim against cmp. If required is false, this method will return true if the value matches or is unset

func (*StandardClaims) VerifyIssuer 

func (c *StandardClaims) VerifyIssuer(cmp string, req bool) bool

Compares the iss claim against cmp. If required is false, this method will return true if the value matches or is unset

func (*StandardClaims) VerifyNotBefore 

func (c *StandardClaims) VerifyNotBefore(cmp int64, req bool) bool

Compares the nbf claim against cmp. If required is false, this method will return true if the value matches or is unset

type Token 

type Token struct {
	Raw       string                 // The raw token.  Populated when you Parse a token
	Method    SigningMethod          // The signing method used or to be used
	Header    map[string]interface{} // The first segment of the token
	Claims    Claims                 // The second segment of the token
	Signature string                 // The third segment of the token.  Populated when you Parse a token
	Valid     bool                   // Is the token valid?  Populated when you Parse/Verify a token
}

A JWT Token. Different fields will be used depending on whether you're creating or parsing/verifying a token.

func New 

func New(method SigningMethod) *Token

Create a new Token. Takes a signing method

func NewWithClaims 

func NewWithClaims(method SigningMethod, claims Claims) *Token

func Parse 

func Parse(tokenString string, keyFunc Keyfunc) (*Token, error)

Parse, validate, and return a token. keyFunc will receive the parsed token and should return the key for validating. If everything is kosher, err will be nil

func ParseWithClaims 

func ParseWithClaims(tokenString string, claims Claims, keyFunc Keyfunc) (*Token, error)

func (*Token) SignedString 

func (t *Token) SignedString(key interface{}) (string, error)

Get the complete, signed token

func (*Token) SigningString 

func (t *Token) SigningString() (string, error)

Generate the signing string. This is the most expensive part of the whole deal. Unless you need this for something special, just go straight for the SignedString.

type ValidationError 

type ValidationError struct {
	Inner  error  // stores the error returned by external dependencies, i.e.: KeyFunc
	Errors uint32 // bitfield.  see ValidationError... constants
	// contains filtered or unexported fields
}

The error from Parse if token is not valid

func NewValidationError 

func NewValidationError(errorText string, errorFlags uint32) *ValidationError

Helper for constructing a ValidationError with a string error message

func (ValidationError) Error 

func (e ValidationError) Error() string

Validation error is an error type

Source Files

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