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tokens.go
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tokens.go
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package manager
import (
"encoding/base64"
"hash/crc32"
"strconv"
"strings"
"github.com/krixlion/dev_forum-auth/pkg/entity"
"github.com/krixlion/dev_forum-auth/pkg/tokens"
"github.com/krixlion/dev_forum-lib/str"
"github.com/lestrrat-go/jwx/jwa"
"github.com/lestrrat-go/jwx/jws"
"github.com/lestrrat-go/jwx/jwt"
)
// GenerateAccessToken returns an access token following this package's
// specification or a non-nil error on validation failure.
func (m StdTokenManager) Encode(privateKey entity.Key, token entity.Token) ([]byte, error) {
b := jwt.NewBuilder()
b.Expiration(token.ExpiresAt)
b.IssuedAt(token.IssuedAt)
b.Issuer(m.config.Issuer)
b.Subject(token.UserId)
b.JwtID(token.Id)
b.Claim("type", token.Type)
jwtoken, err := b.Build()
if err != nil {
return nil, err
}
headers := jws.NewHeaders()
if err := headers.Set("kid", privateKey.Id); err != nil {
return nil, err
}
algo, err := toJwaAlgorithm(privateKey.Algorithm)
if err != nil {
return nil, err
}
signedJWT, err := jwt.Sign(jwtoken, algo, privateKey.Raw, jwt.WithHeaders(headers))
if err != nil {
return nil, err
}
return signedJWT, nil
}
// GenerateOpaque generates an opaque token. It returns an
// encoded token, a random string used as a token's base and an err.
func (StdTokenManager) GenerateOpaque(typ tokens.OpaqueTokenPrefix) (string, string, error) {
randomString, err := str.RandomAlphaString(16)
if err != nil {
return "", "", err
}
checksum := crc32.ChecksumIEEE([]byte(randomString))
suffix := strconv.FormatUint(uint64(checksum), 16)
encoded := base64.URLEncoding.EncodeToString([]byte(randomString + "_" + suffix))
prefixType, err := typ.String()
if err != nil {
return "", "", err
}
token := prefixType + "_" + encoded
return token, randomString, nil
}
// DecodeOpaque decodes a opaque AccessToken and returns a non-nil error if it's invalid.
func (StdTokenManager) DecodeOpaque(typ tokens.OpaqueTokenPrefix, encodedOpaqueToken string) (string, error) {
if len(encodedOpaqueToken) < 4 {
// Token is shorter than prefix.
return "", tokens.ErrMalformedToken
}
typePrefix, err := typ.String()
if err != nil {
return "", err
}
if prefix := encodedOpaqueToken[:4]; prefix != typePrefix+"_" {
// Invalid prefix.
return "", tokens.ErrMalformedToken
}
// Decode token part without its prefix.
return decodeAndValidateOpaque(encodedOpaqueToken[4:])
}
func toJwaAlgorithm(algo entity.Algorithm) (jwa.SignatureAlgorithm, error) {
switch algo {
case entity.RS256:
return jwa.RS256, nil
case entity.HS256:
return jwa.HS256, nil
case entity.ES256:
return jwa.ES256, nil
default:
return "", tokens.ErrInvalidAlgorithm
}
}
// decodeAndValidateOpaque takes a base64 encoded token without it's prefix, decodes and returns it.
// Returns tokens.ErrInvalidToken on invalid checksum or length or any errors during decoding.
func decodeAndValidateOpaque(encodedToken string) (string, error) {
decodedToken, err := base64.URLEncoding.DecodeString(encodedToken)
if err != nil {
return "", err
}
// Extract token's value and checksum.
token, extractedChecksum, ok := strings.Cut(string(decodedToken), "_")
if !ok {
return "", tokens.ErrMalformedToken
}
// Convert to HEX for comparison with extracted checksum.
// Use strconv.FormatUint instead of fmt.Sprintf("%x") for better performance.
receivedChecksum := strconv.FormatUint(uint64(crc32.ChecksumIEEE([]byte(token))), 16)
if receivedChecksum != string(extractedChecksum) {
return "", tokens.ErrMalformedToken
}
return string(token), nil
}