README ¶
jwt-go
A go (or 'golang' for search engine friendliness) implementation of JSON Web Tokens
NEW VERSION COMING: There have been a lot of improvements suggested since the version 3.0.0 released in 2016. I'm working now on cutting two different releases: 3.2.0 will contain any non-breaking changes or enhancements. 4.0.0 will follow shortly which will include breaking changes. See the 4.0.0 milestone to get an idea of what's coming. If you have other ideas, or would like to participate in 4.0.0, now's the time. If you depend on this library and don't want to be interrupted, I recommend you use your dependency mangement tool to pin to version 3.
SECURITY NOTICE: Some older versions of Go have a security issue in the cryotp/elliptic. Recommendation is to upgrade to at least 1.8.3. See issue #216 for more detail.
SECURITY NOTICE: It's important that you validate the alg
presented is what you expect. This library attempts to make it easy to do the right thing by requiring key types match the expected alg, but you should take the extra step to verify it in your usage. See the examples provided.
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:
- Simple example of parsing and validating a token
- Simple example of building and signing a token
- Directory of Examples
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 multiple Google Cloud Platform signing tools (AppEngine, IAM API, Cloud KMS): 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 constantjwt.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.v3
. It will do the right thing WRT semantic versioning.
BREAKING CHANGES:*
- Version 3.0.0 includes a lot of changes from the 2.x line, 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
. SeeMIGRATION_GUIDE.md
for more information on updating your code.
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.
Signing Methods and Key Types
Each signing method expects a different object type for its signing keys. See the package documentation for details. Here are the most common ones:
- The HMAC signing method (
HS256
,HS384
,HS512
) expect[]byte
values for signing and validation - The RSA signing method (
RS256
,RS384
,RS512
) expect*rsa.PrivateKey
for signing and*rsa.PublicKey
for validation - The ECDSA signing method (
ES256
,ES384
,ES512
) expect*ecdsa.PrivateKey
for signing and*ecdsa.PublicKey
for validation
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.
Troubleshooting
This library uses descriptive error messages whenever possible. If you are not getting the expected result, have a look at the errors. The most common place people get stuck is providing the correct type of key to the parser. See the above section on signing methods and key types.
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 the 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.
Example (GetTokenViaHTTP) ¶
Output: test
Example (UseTokenViaHTTP) ¶
Output: Welcome, foo
Index ¶
- Constants
- Variables
- func DecodeSegment(seg string) ([]byte, error)
- func EncodeSegment(seg []byte) string
- func ParseECPrivateKeyFromPEM(key []byte) (*ecdsa.PrivateKey, error)
- func ParseECPublicKeyFromPEM(key []byte) (*ecdsa.PublicKey, error)
- func ParseEdPrivateKeyFromPEM(key []byte) (crypto.PrivateKey, error)
- func ParseEdPublicKeyFromPEM(key []byte) (crypto.PublicKey, error)
- func ParseRSAPrivateKeyFromPEM(key []byte) (*rsa.PrivateKey, error)
- func ParseRSAPrivateKeyFromPEMWithPassword(key []byte, password string) (*rsa.PrivateKey, error)
- func ParseRSAPublicKeyFromPEM(key []byte) (*rsa.PublicKey, error)
- func RegisterSigningMethod(alg string, f func() SigningMethod)
- type Claims
- type Keyfunc
- type MapClaims
- func (m MapClaims) Valid() error
- func (m MapClaims) VerifyAudience(cmp string, req bool) bool
- func (m MapClaims) VerifyExpiresAt(cmp int64, req bool) bool
- func (m MapClaims) VerifyIssuedAt(cmp int64, req bool) bool
- func (m MapClaims) VerifyIssuer(cmp string, req bool) bool
- func (m MapClaims) VerifyNotBefore(cmp int64, req bool) bool
- type OI
- type Parser
- type SigningMethod
- type SigningMethodECDSA
- type SigningMethodEd25519
- type SigningMethodHMAC
- type SigningMethodRSA
- type SigningMethodRSAPSS
- type StandardClaims
- func (c StandardClaims) Valid() error
- func (c *StandardClaims) VerifyAudience(cmp string, req bool) bool
- func (c *StandardClaims) VerifyExpiresAt(cmp int64, req bool) bool
- func (c *StandardClaims) VerifyIssuedAt(cmp int64, req bool) bool
- func (c *StandardClaims) VerifyIssuer(cmp string, req bool) bool
- func (c *StandardClaims) VerifyNotBefore(cmp int64, req bool) bool
- type Token
- type ValidationError
Examples ¶
Constants ¶
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
const UnsafeAllowNoneSignatureType unsafeNoneMagicConstant = "none signing method allowed"
Variables ¶
var ( ErrNotECPublicKey = errors.New("Key is not a valid ECDSA public key") ErrNotECPrivateKey = errors.New("Key is not a valid ECDSA private key") )
var ( ErrInvalidKey = errors.New("key is invalid") ErrInvalidKeyType = errors.New("key is of invalid type") )
Error constants
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") )
var ( // Sadly this is missing from crypto/ecdsa compared to crypto/rsa ErrECDSAVerification = errors.New("crypto/ecdsa: verification error") )
var (
ErrEd25519Verification = errors.New("ed25519: verification error")
)
var NoneSignatureTypeDisallowedError error
var SigningMethodNone *signingMethodNone
Implements the none signing method. This is required by the spec but you probably should never use it.
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 ¶
Decode JWT specific base64url encoding with padding stripped
func EncodeSegment ¶
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 ¶
Parse PEM encoded PKCS1 or PKCS8 public key
func ParseEdPrivateKeyFromPEM ¶
func ParseEdPrivateKeyFromPEM(key []byte) (crypto.PrivateKey, error)
Parse PEM-encoded Edwards curve private key
func ParseEdPublicKeyFromPEM ¶
Parse PEM-encoded Edwards curve public key
func ParseRSAPrivateKeyFromPEM ¶
func ParseRSAPrivateKeyFromPEM(key []byte) (*rsa.PrivateKey, error)
Parse PEM encoded PKCS1 or PKCS8 private key
func ParseRSAPrivateKeyFromPEMWithPassword ¶
func ParseRSAPrivateKeyFromPEMWithPassword(key []byte, password string) (*rsa.PrivateKey, error)
Parse PEM encoded PKCS1 or PKCS8 private key protected with password
func ParseRSAPublicKeyFromPEM ¶
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 ¶
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 ¶
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 ¶
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 ¶
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 ¶
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 ¶
Compares the iss claim against cmp. If required is false, this method will return true if the value matches or is unset
type OI ¶
type OI struct {
ObjectIdentifier asn1.ObjectIdentifier
}
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 SkipClaimsValidation bool // Skip claims validation during token parsing }
func (*Parser) Parse ¶
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) ParseUnverified ¶
func (p *Parser) ParseUnverified(tokenString string, claims Claims) (token *Token, parts []string, err error)
WARNING: Don't use this method unless you know what you're doing
This method parses the token but doesn't validate the signature. It's only ever useful in cases where you know the signature is valid (because it has been checked previously in the stack) and you want to extract values from it.
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 ¶
Implements the ECDSA family of signing methods signing methods Expects *ecdsa.PrivateKey for signing and *ecdsa.PublicKey for verification
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 SigningMethodEd25519 ¶
type SigningMethodEd25519 struct{}
Implements the EdDSA family Expects *ed25519.PrivateKey for signing and *ed25519.PublicKey for verification
var (
SigningMethodEdDSA *SigningMethodEd25519
)
Specific instance for EdDSA
func (*SigningMethodEd25519) Alg ¶
func (m *SigningMethodEd25519) Alg() string
func (*SigningMethodEd25519) Sign ¶
func (m *SigningMethodEd25519) Sign(signingString string, key interface{}) (string, error)
Implements the Sign method from SigningMethod For this signing method, key must be an Ed25519.PrivateKey struct
func (*SigningMethodEd25519) Verify ¶
func (m *SigningMethodEd25519) Verify(signingString, signature string, key interface{}) error
Implements the Verify method from SigningMethod For this verify method, key must be an Ed25519.PublicKey struct
type SigningMethodHMAC ¶
Implements the HMAC-SHA family of signing methods signing methods Expects key type of []byte for both signing and validation
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 ¶
Implements the RSA family of signing methods signing methods Expects *rsa.PrivateKey for signing and *rsa.PublicKey for validation
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
Example (Hmac) ¶
Example creating, signing, and encoding a JWT token using the HMAC signing method
Output: eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJmb28iOiJiYXIiLCJuYmYiOjE0NDQ0Nzg0MDB9.u1riaD1rW97opCoAuRCTy4w58Br-Zk-bh7vLiRIsrpU <nil>
func NewWithClaims ¶
func NewWithClaims(method SigningMethod, claims Claims) *Token
Example (CustomClaimsType) ¶
Example creating a token using a custom claims type. The StandardClaim is embedded in the custom type to allow for easy encoding, parsing and validation of standard claims.
Output: eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJmb28iOiJiYXIiLCJleHAiOjE1MDAwLCJpc3MiOiJ0ZXN0In0.HE7fK0xOQwFEr4WDgRWj4teRPZ6i3GLwD5YCm6Pwu_c <nil>
Example (StandardClaims) ¶
Example (atypical) using the StandardClaims type by itself to parse a token. The StandardClaims type is designed to be embedded into your custom types to provide standard validation features. You can use it alone, but there's no way to retrieve other fields after parsing. See the CustomClaimsType example for intended usage.
Output: eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJleHAiOjE1MDAwLCJpc3MiOiJ0ZXN0In0.QsODzZu3lUZMVdhbO76u3Jv02iYCvEHcYVUI1kOWEU0 <nil>
func Parse ¶
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
Example (ErrorChecking) ¶
An example of parsing the error types using bitfield checks
Output: Timing is everything
Example (Hmac) ¶
Example parsing and validating a token using the HMAC signing method
Output: bar 1.4444784e+09
func ParseWithClaims ¶
Example (CustomClaimsType) ¶
Example creating a token using a custom claims type. The StandardClaim is embedded in the custom type to allow for easy encoding, parsing and validation of standard claims.
Output: bar 15000
func (*Token) SignedString ¶
Get the complete, signed token
func (*Token) SigningString ¶
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