1package jwt
2
3import (
4	"crypto"
5	"crypto/rand"
6	"crypto/rsa"
7)
8
9// SigningMethodRSA implements the RSA family of signing methods.
10// Expects *rsa.PrivateKey for signing and *rsa.PublicKey for validation
11type SigningMethodRSA struct {
12	Name string
13	Hash crypto.Hash
14}
15
16// Specific instances for RS256 and company
17var (
18	SigningMethodRS256 *SigningMethodRSA
19	SigningMethodRS384 *SigningMethodRSA
20	SigningMethodRS512 *SigningMethodRSA
21)
22
23func init() {
24	// RS256
25	SigningMethodRS256 = &SigningMethodRSA{"RS256", crypto.SHA256}
26	RegisterSigningMethod(SigningMethodRS256.Alg(), func() SigningMethod {
27		return SigningMethodRS256
28	})
29
30	// RS384
31	SigningMethodRS384 = &SigningMethodRSA{"RS384", crypto.SHA384}
32	RegisterSigningMethod(SigningMethodRS384.Alg(), func() SigningMethod {
33		return SigningMethodRS384
34	})
35
36	// RS512
37	SigningMethodRS512 = &SigningMethodRSA{"RS512", crypto.SHA512}
38	RegisterSigningMethod(SigningMethodRS512.Alg(), func() SigningMethod {
39		return SigningMethodRS512
40	})
41}
42
43func (m *SigningMethodRSA) Alg() string {
44	return m.Name
45}
46
47// Verify implements token verification for the SigningMethod
48// For this signing method, must be an *rsa.PublicKey structure.
49func (m *SigningMethodRSA) Verify(signingString, signature string, key interface{}) error {
50	var err error
51
52	// Decode the signature
53	var sig []byte
54	if sig, err = DecodeSegment(signature); err != nil {
55		return err
56	}
57
58	var rsaKey *rsa.PublicKey
59	var ok bool
60
61	if rsaKey, ok = key.(*rsa.PublicKey); !ok {
62		return ErrInvalidKeyType
63	}
64
65	// Create hasher
66	if !m.Hash.Available() {
67		return ErrHashUnavailable
68	}
69	hasher := m.Hash.New()
70	hasher.Write([]byte(signingString))
71
72	// Verify the signature
73	return rsa.VerifyPKCS1v15(rsaKey, m.Hash, hasher.Sum(nil), sig)
74}
75
76// Sign implements token signing for the SigningMethod
77// For this signing method, must be an *rsa.PrivateKey structure.
78func (m *SigningMethodRSA) Sign(signingString string, key interface{}) (string, error) {
79	var rsaKey *rsa.PrivateKey
80	var ok bool
81
82	// Validate type of key
83	if rsaKey, ok = key.(*rsa.PrivateKey); !ok {
84		return "", ErrInvalidKey
85	}
86
87	// Create the hasher
88	if !m.Hash.Available() {
89		return "", ErrHashUnavailable
90	}
91
92	hasher := m.Hash.New()
93	hasher.Write([]byte(signingString))
94
95	// Sign the string and return the encoded bytes
96	if sigBytes, err := rsa.SignPKCS1v15(rand.Reader, rsaKey, m.Hash, hasher.Sum(nil)); err == nil {
97		return EncodeSegment(sigBytes), nil
98	} else {
99		return "", err
100	}
101}
102