1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
|
;; disfluid, implementation of the Solid specification
;; Copyright (C) 2020, 2021 Vivien Kraus
;; This program is free software: you can redistribute it and/or modify
;; it under the terms of the GNU Affero General Public License as
;; published by the Free Software Foundation, either version 3 of the
;; License, or (at your option) any later version.
;; This program is distributed in the hope that it will be useful,
;; but WITHOUT ANY WARRANTY; without even the implied warranty of
;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
;; GNU Affero General Public License for more details.
;; You should have received a copy of the GNU Affero General Public License
;; along with this program. If not, see <https://www.gnu.org/licenses/>.
(define-module (webid-oidc jws)
#:use-module (webid-oidc jwk)
#:use-module (webid-oidc errors)
#:use-module (webid-oidc web-i18n)
#:use-module ((webid-oidc stubs) #:prefix stubs:)
#:use-module (rnrs bytevectors)
#:use-module (ice-9 receive)
#:use-module (ice-9 exceptions)
#:use-module (ice-9 match)
#:use-module (oop goops)
#:declarative? #t
#:export
(
&invalid-jws
make-invalid-jws
invalid-jws?
the-jws
jws?
jws-alg
&cannot-query-identity-provider
make-cannot-query-identity-provider
cannot-query-identity-provider?
cannot-query-identity-provider-value
&signed-in-future
make-signed-in-future
signed-in-future?
error-signature-date
error-current-date
&expired
make-expired
expired?
error-expiration-date
;; error-current-date works for that one too
jws-decode
jws-encode
))
(define-exception-type
&invalid-jws
&external-error
make-invalid-jws
invalid-jws?)
(define (the-jws x)
(with-exception-handler
(lambda (error)
(let ((final-message
(if (exception-with-message? error)
(format #f (G_ "the JWS is invalid: ~a")
(exception-message error))
(format #f (G_ "the JWS is invalid")))))
(raise-exception
(make-exception
(make-invalid-jws)
(make-exception-with-message final-message)
error))))
(lambda ()
(match x
((header . payload)
(let examine-header ((header header)
(alg #f)
(other-header-fields '()))
(match header
(()
(let examine-payload ((payload payload)
(other-payload-fields '()))
(match payload
(()
(unless alg
(fail (format #f (G_ "the JWS header does not have an \"alg\" field"))))
`(((alg . ,(symbol->string alg))
,@(reverse other-header-fields))
. ,(reverse other-payload-fields)))
((((? symbol? key) . value) payload ...)
(examine-payload payload
`((,key . ,value) ,@other-payload-fields)))
(else
(fail (format #f (G_ "invalid JSON object as payload")))))))
((('alg . (? string? given-alg)) header ...)
(case (string->symbol given-alg)
((HS256 HS384 HS512
RS256 RS384 RS512
ES256 ES384 ES512
PS256 PS384 PS512)
#t)
(else
(fail (format #f (G_ "invalid signature algorithm: ~s") given-alg))))
(examine-header header (or alg (string->symbol given-alg))
other-header-fields))
((('alg . invalid) header ...)
(fail (format #f (G_ "invalid \"alg\" value: ~s") invalid)))
((((? symbol? key) . value) header ...)
(examine-header header alg
`((,key . ,value) ,@other-header-fields)))
(else
(fail (format #f (G_ "invalid JSON object as header")))))))
(else
(fail (format #f (G_ "this is not a pair"))))))))
(define (jws? x)
(false-if-exception
(the-jws x)))
(define (jws-alg jws)
(match (the-jws jws)
((header . _)
(string->symbol (assq-ref header 'alg)))))
(define (split-in-3-parts string separator)
(match (string-split string separator)
((header payload signature)
(values header payload signature))
(else
(let ((final-message
(format #f (G_ "the encoded JWS is not in 3 parts"))))
(raise-exception
(make-exception
(make-invalid-jws)
(make-exception-with-message final-message)))))))
(define (base64-decode-json str)
(with-exception-handler
(lambda (error)
(let ((final-message
(if (exception-with-message? error)
(format #f (G_ "the encoded JWS header or payload is not a JSON object encoded in base64: ~a")
(exception-message error))
(format #f (G_ "the encoded JWS header or payload is not a JSON object encoded in base64")))))
(raise-exception
(make-exception
(make-invalid-jws)
(make-exception-with-message final-message)
error))))
(lambda ()
(stubs:json-string->scm
(utf8->string (stubs:base64-decode str))))))
(define-exception-type
&cannot-query-identity-provider
&external-error
make-cannot-query-identity-provider
cannot-query-identity-provider?
(identity-provider cannot-query-identity-provider-value))
(define-exception-type
&signed-in-future
&external-error
make-signed-in-future
signed-in-future?
(signature-date error-signature-date)
(current-date error-current-date*))
(define-exception-type
&expired
&external-error
make-expired
expired?
(expiration-date error-expiration-date)
(current-date error-current-date**))
(define error-current-date
(match-lambda
((or ($ &signed-in-future _ date)
($ &expired _ date)
($ &compound-exception (($ &signed-in-future _ date) _ ...))
($ &compound-exception (($ &expired _ date) _ ...)))
date)
(($ &compound-exception (_ sub-exceptions ...))
(error-current-date (apply make-exception sub-exceptions)))
(else #f)))
(define (parse str verify)
(receive (header payload signature)
(split-in-3-parts str #\.)
(let ((base (string-append header "." payload))
(header (base64-decode-json header))
(payload (base64-decode-json payload)))
(let ((ret `(,header . ,payload)))
(verify ret base signature)
ret))))
(define (verify-any alg keys payload signature)
(let try-with-key ((keys keys))
(match keys
(()
(let ((final-message
(format #f (G_ "the JWS is not signed by any of the expected set of public keys"))))
(raise-exception
(make-exception
(make-invalid-jws)
(make-exception-with-message final-message)))))
((next-key keys ...)
(with-exception-handler
(lambda (error)
(unless (stubs:invalid-signature? error)
(let ((final-message
(if (exception-with-message? error)
(format #f (G_ "while verifying the JWS signature: ~a")
(exception-message error))
(format #f (G_ "an unexpected error happened while verifying a JWS")))))
(raise-exception
(make-exception
(make-invalid-jws)
(make-exception-with-message final-message)
error))))
(try-with-key keys))
(lambda ()
(stubs:verify alg (key->jwk next-key) payload signature))
#:unwind? #t
#:unwind-for-type stubs:&invalid-signature)))))
;; For verification, we can supply a JWKS, or a public key, or a list
;; of public keys. The JWKS case is handled in (webid-oidc jwk).
(define-method (keys (key <public-key>))
(list key))
(define-method (keys (key <key-pair>))
(list (public-key key)))
(define-method (keys (keys <list>))
(map public-key keys))
(define (jws-decode str lookup-keys)
(with-exception-handler
(lambda (error)
(let ((final-message
(if (exception-with-message? error)
(format #f (G_ "cannot decode a JWS: ~a")
(exception-message error))
(format #f (G_ "cannot decode a JWS")))))
(raise-exception
(make-exception
(make-invalid-jws)
(make-exception-with-message final-message)
error))))
(lambda ()
(parse str
(lambda (jws payload signature)
(let ((k (keys (lookup-keys jws))))
(verify-any (jws-alg jws) k payload signature)))))))
(define (jws-encode jws key)
(with-exception-handler
(lambda (error)
(let ((final-message
(if (exception-with-message? error)
(format #f (G_ "cannot encode a JWS: ~a")
(exception-message error))
(format #f (G_ "cannot encode a JWS")))))
(raise-exception
(make-exception
(make-invalid-jws)
(make-exception-with-message final-message)
error))))
(lambda ()
(match jws
((header . payload)
(let ((header (stubs:scm->json-string header))
(payload (stubs:scm->json-string payload)))
(let ((header (stubs:base64-encode header))
(payload (stubs:base64-encode payload)))
(let ((payload (string-append header "." payload)))
(let ((signature (stubs:sign (jws-alg jws) (key->jwk key) payload)))
(string-append payload "." signature))))))))))
|
