1// +build go1.4
2
3package jwt
4
5import (
6	"crypto"
7	"crypto/rand"
8	"crypto/rsa"
9)
10
11// Implements the RSAPSS family of signing methods signing methods
12type SigningMethodRSAPSS struct {
13	*SigningMethodRSA
14	Options *rsa.PSSOptions
15}
16
17// Specific instances for RS/PS and company
18var (
19	SigningMethodPS256 *SigningMethodRSAPSS
20	SigningMethodPS384 *SigningMethodRSAPSS
21	SigningMethodPS512 *SigningMethodRSAPSS
22)
23
24func init() {
25	// PS256
26	SigningMethodPS256 = &SigningMethodRSAPSS{
27		&SigningMethodRSA{
28			Name: "PS256",
29			Hash: crypto.SHA256,
30		},
31		&rsa.PSSOptions{
32			SaltLength: rsa.PSSSaltLengthAuto,
33			Hash:       crypto.SHA256,
34		},
35	}
36	RegisterSigningMethod(SigningMethodPS256.Alg(), func() SigningMethod {
37		return SigningMethodPS256
38	})
39
40	// PS384
41	SigningMethodPS384 = &SigningMethodRSAPSS{
42		&SigningMethodRSA{
43			Name: "PS384",
44			Hash: crypto.SHA384,
45		},
46		&rsa.PSSOptions{
47			SaltLength: rsa.PSSSaltLengthAuto,
48			Hash:       crypto.SHA384,
49		},
50	}
51	RegisterSigningMethod(SigningMethodPS384.Alg(), func() SigningMethod {
52		return SigningMethodPS384
53	})
54
55	// PS512
56	SigningMethodPS512 = &SigningMethodRSAPSS{
57		&SigningMethodRSA{
58			Name: "PS512",
59			Hash: crypto.SHA512,
60		},
61		&rsa.PSSOptions{
62			SaltLength: rsa.PSSSaltLengthAuto,
63			Hash:       crypto.SHA512,
64		},
65	}
66	RegisterSigningMethod(SigningMethodPS512.Alg(), func() SigningMethod {
67		return SigningMethodPS512
68	})
69}
70
71// Implements the Verify method from SigningMethod
72// For this verify method, key must be an rsa.PublicKey struct
73func (m *SigningMethodRSAPSS) Verify(signingString, signature string, key interface{}) error {
74	var err error
75
76	// Decode the signature
77	var sig []byte
78	if sig, err = DecodeSegment(signature); err != nil {
79		return err
80	}
81
82	var rsaKey *rsa.PublicKey
83	switch k := key.(type) {
84	case *rsa.PublicKey:
85		rsaKey = k
86	default:
87		return ErrInvalidKey
88	}
89
90	// Create hasher
91	if !m.Hash.Available() {
92		return ErrHashUnavailable
93	}
94	hasher := m.Hash.New()
95	hasher.Write([]byte(signingString))
96
97	return rsa.VerifyPSS(rsaKey, m.Hash, hasher.Sum(nil), sig, m.Options)
98}
99
100// Implements the Sign method from SigningMethod
101// For this signing method, key must be an rsa.PrivateKey struct
102func (m *SigningMethodRSAPSS) Sign(signingString string, key interface{}) (string, error) {
103	var rsaKey *rsa.PrivateKey
104
105	switch k := key.(type) {
106	case *rsa.PrivateKey:
107		rsaKey = k
108	default:
109		return "", ErrInvalidKeyType
110	}
111
112	// Create the hasher
113	if !m.Hash.Available() {
114		return "", ErrHashUnavailable
115	}
116
117	hasher := m.Hash.New()
118	hasher.Write([]byte(signingString))
119
120	// Sign the string and return the encoded bytes
121	if sigBytes, err := rsa.SignPSS(rand.Reader, rsaKey, m.Hash, hasher.Sum(nil), m.Options); err == nil {
122		return EncodeSegment(sigBytes), nil
123	} else {
124		return "", err
125	}
126}
127