58 lines
1.6 KiB
Go
58 lines
1.6 KiB
Go
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package authjwt
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import (
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"crypto/rsa"
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"crypto/x509"
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"encoding/pem"
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"fmt"
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"github.com/golang-jwt/jwt/v5"
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)
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var _ Signer = (*rsaSigner)(nil)
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type rsaSigner struct {
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private *rsa.PrivateKey
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public *rsa.PublicKey
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}
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// NewRSASigner returns a Signer backed by RSA-SHA256 (RS256).
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// The public key is derived from the private key — no separate argument needed.
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func NewRSASigner(privateKey *rsa.PrivateKey) Signer {
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return &rsaSigner{private: privateKey, public: &privateKey.PublicKey}
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}
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// NewRSASignerFromPEM parses a PKCS#8 or PKCS#1 PEM-encoded RSA private key.
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func NewRSASignerFromPEM(pemKey []byte) (Signer, error) {
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block, _ := pem.Decode(pemKey)
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if block == nil {
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return nil, fmt.Errorf("no PEM block found")
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}
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key, err := x509.ParsePKCS8PrivateKey(block.Bytes)
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if err != nil {
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rsaKey, err2 := x509.ParsePKCS1PrivateKey(block.Bytes)
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if err2 != nil {
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return nil, fmt.Errorf("parse RSA private key: %w", err)
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}
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return NewRSASigner(rsaKey), nil
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}
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rsaKey, ok := key.(*rsa.PrivateKey)
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if !ok {
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return nil, fmt.Errorf("PEM key is not an RSA private key")
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}
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return NewRSASigner(rsaKey), nil
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}
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func (s *rsaSigner) Sign(claims jwt.Claims) (string, error) {
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return jwt.NewWithClaims(jwt.SigningMethodRS256, claims).SignedString(s.private)
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}
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func (s *rsaSigner) Verify(tokenString string) (*jwt.Token, error) {
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return jwt.Parse(tokenString, func(t *jwt.Token) (any, error) {
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if _, ok := t.Method.(*jwt.SigningMethodRSA); !ok {
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return nil, fmt.Errorf("unexpected signing method %q", t.Header["alg"])
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}
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return s.public, nil
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}, jwt.WithJSONNumber())
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}
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