forked from ebhomengo/niki
170 lines
3.3 KiB
Go
170 lines
3.3 KiB
Go
package jwt
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import (
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"crypto"
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"crypto/hmac"
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"errors"
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)
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// SigningMethodHMAC implements the HMAC-SHA family of signing methods.
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// Expects key type of []byte for both signing and validation
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type SigningMethodHMAC struct {
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Name string
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Hash crypto.Hash
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}
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// Specific instances for HS256 and company
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var (
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SigningMethodHS256 *SigningMethodHMAC
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SigningMethodHS384 *SigningMethodHMAC
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SigningMethodHS512 *SigningMethodHMAC
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ErrSignatureInvalid = errors.New("signature is invalid")
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)
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func init() {
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// HS256
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SigningMethodHS256 = &SigningMethodHMAC{"HS256", crypto.SHA256}
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RegisterSigningMethod(SigningMethodHS256.Alg(), func() SigningMethod {
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return SigningMethodHS256
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})
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// HS384
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SigningMethodHS384 = &SigningMethodHMAC{"HS384", crypto.SHA384}
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RegisterSigningMethod(SigningMethodHS384.Alg(), func() SigningMethod {
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return SigningMethodHS384
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})
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// HS512
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SigningMethodHS512 = &SigningMethodHMAC{"HS512", crypto.SHA512}
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RegisterSigningMethod(SigningMethodHS512.Alg(), func() SigningMethod {
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return SigningMethodHS512
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})
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}
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func (m *SigningMethodHMAC) Alg() string {
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return m.Name
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}
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// Verify implements token verification for the SigningMethod. Returns nil if
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// the signature is valid. Key must be []byte.
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//
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// Note it is not advised to provide a []byte which was converted from a 'human
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// readable' string using a subset of ASCII characters. To maximize entropy, you
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// should ideally be providing a []byte key which was produced from a
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// cryptographically random source, e.g. crypto/rand. Additional information
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// about this, and why we intentionally are not supporting string as a key can
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// be found on our usage guide
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// https://golang-jwt.github.io/jwt/usage/signing_methods/#signing-methods-and-key-types.
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func (m *SigningMethodHMAC) Verify(signingString string, sig []byte, key interface{}) error {
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// Verify the key is the right type
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keyBytes, ok := key.([]byte)
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if !ok {
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return ErrInvalidKeyType
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}
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// Can we use the specified hashing method?
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if !m.Hash.Available() {
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return ErrHashUnavailable
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}
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// This signing method is symmetric, so we validate the signature
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// by reproducing the signature from the signing string and key, then
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// comparing that against the provided signature.
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hasher := hmac.New(m.Hash.New, keyBytes)
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hasher.Write([]byte(signingString))
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if !hmac.Equal(sig, hasher.Sum(nil)) {
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return ErrSignatureInvalid
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}
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// No validation errors. Signature is good.
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return nil
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}
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// Sign implements token signing for the SigningMethod. Key must be []byte.
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//
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// Note it is not advised to provide a []byte which was converted from a 'human
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// readable' string using a subset of ASCII characters. To maximize entropy, you
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// should ideally be providing a []byte key which was produced from a
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// cryptographically random source, e.g. crypto/rand. Additional information
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// about this, and why we intentionally are not supporting string as a key can
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// be found on our usage guide https://golang-jwt.github.io/jwt/usage/signing_methods/.
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func (m *SigningMethodHMAC) Sign(signingString string, key interface{}) ([]byte, error) {
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if keyBytes, ok := key.([]byte); ok {
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if !m.Hash.Available() {
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return nil, ErrHashUnavailable
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}
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hasher := hmac.New(m.Hash.New, keyBytes)
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hasher.Write([]byte(signingString))
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return hasher.Sum(nil), nil
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}
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return nil, ErrInvalidKeyType
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}
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