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
|
/*
* OCSP
* (C) 2012,2013 Jack Lloyd
*
* Botan is released under the Simplified BSD License (see license.txt)
*/
#include <botan/ocsp.h>
#include <botan/certstor.h>
#include <botan/der_enc.h>
#include <botan/ber_dec.h>
#include <botan/x509_ext.h>
#include <botan/oids.h>
#include <botan/base64.h>
#include <botan/pubkey.h>
#include <botan/x509path.h>
#include <botan/http_util.h>
namespace Botan {
namespace OCSP {
namespace {
void decode_optional_list(BER_Decoder& ber,
ASN1_Tag tag,
std::vector<X509_Certificate>& output)
{
BER_Object obj = ber.get_next_object();
if(obj.type_tag != tag || obj.class_tag != (CONTEXT_SPECIFIC | CONSTRUCTED))
{
ber.push_back(obj);
return;
}
BER_Decoder list(obj.value);
while(list.more_items())
{
BER_Object certbits = list.get_next_object();
X509_Certificate cert(unlock(certbits.value));
output.push_back(std::move(cert));
}
}
void check_signature(const std::vector<byte>& tbs_response,
const AlgorithmIdentifier& sig_algo,
const std::vector<byte>& signature,
const X509_Certificate& cert)
{
std::unique_ptr<Public_Key> pub_key(cert.subject_public_key());
const std::vector<std::string> sig_info =
split_on(OIDS::lookup(sig_algo.oid), '/');
if(sig_info.size() != 2 || sig_info[0] != pub_key->algo_name())
throw Exception("Information in OCSP response does not match cert");
std::string padding = sig_info[1];
Signature_Format format =
(pub_key->message_parts() >= 2) ? DER_SEQUENCE : IEEE_1363;
PK_Verifier verifier(*pub_key, padding, format);
if(!verifier.verify_message(ASN1::put_in_sequence(tbs_response), signature))
throw Exception("Signature on OCSP response does not verify");
}
void check_signature(const std::vector<byte>& tbs_response,
const AlgorithmIdentifier& sig_algo,
const std::vector<byte>& signature,
const Certificate_Store& trusted_roots,
const std::vector<X509_Certificate>& certs)
{
if(certs.size() < 1)
throw Invalid_Argument("Short cert chain for check_signature");
if(trusted_roots.certificate_known(certs[0]))
return check_signature(tbs_response, sig_algo, signature, certs[0]);
// Otherwise attempt to chain the signing cert to a trust root
if(!certs[0].allowed_extended_usage("PKIX.OCSPSigning"))
throw Exception("OCSP response cert does not allow OCSP signing");
auto result = x509_path_validate(certs, Path_Validation_Restrictions(), trusted_roots);
if(!result.successful_validation())
throw Exception("Certificate validation failure: " + result.result_string());
if(!trusted_roots.certificate_known(result.trust_root())) // not needed anymore?
throw Exception("Certificate chain roots in unknown/untrusted CA");
const std::vector<X509_Certificate>& cert_path = result.cert_path();
check_signature(tbs_response, sig_algo, signature, cert_path[0]);
}
}
std::vector<byte> Request::BER_encode() const
{
CertID certid(m_issuer, m_subject);
return DER_Encoder().start_cons(SEQUENCE)
.start_cons(SEQUENCE)
.start_explicit(0)
.encode(static_cast<size_t>(0)) // version #
.end_explicit()
.start_cons(SEQUENCE)
.start_cons(SEQUENCE)
.encode(certid)
.end_cons()
.end_cons()
.end_cons()
.end_cons().get_contents_unlocked();
}
std::string Request::base64_encode() const
{
return Botan::base64_encode(BER_encode());
}
Response::Response(const Certificate_Store& trusted_roots,
const std::vector<byte>& response_bits)
{
BER_Decoder response_outer = BER_Decoder(response_bits).start_cons(SEQUENCE);
size_t resp_status = 0;
response_outer.decode(resp_status, ENUMERATED, UNIVERSAL);
if(resp_status != 0)
throw Exception("OCSP response status " + std::to_string(resp_status));
if(response_outer.more_items())
{
BER_Decoder response_bytes =
response_outer.start_cons(ASN1_Tag(0), CONTEXT_SPECIFIC).start_cons(SEQUENCE);
response_bytes.decode_and_check(OID("1.3.6.1.5.5.7.48.1.1"),
"Unknown response type in OCSP response");
BER_Decoder basicresponse =
BER_Decoder(response_bytes.get_next_octet_string()).start_cons(SEQUENCE);
std::vector<byte> tbs_bits;
AlgorithmIdentifier sig_algo;
std::vector<byte> signature;
std::vector<X509_Certificate> certs;
basicresponse.start_cons(SEQUENCE)
.raw_bytes(tbs_bits)
.end_cons()
.decode(sig_algo)
.decode(signature, BIT_STRING);
decode_optional_list(basicresponse, ASN1_Tag(0), certs);
size_t responsedata_version = 0;
X509_DN name;
std::vector<byte> key_hash;
X509_Time produced_at;
Extensions extensions;
BER_Decoder(tbs_bits)
.decode_optional(responsedata_version, ASN1_Tag(0),
ASN1_Tag(CONSTRUCTED | CONTEXT_SPECIFIC))
.decode_optional(name, ASN1_Tag(1),
ASN1_Tag(CONSTRUCTED | CONTEXT_SPECIFIC))
.decode_optional_string(key_hash, OCTET_STRING, 2,
ASN1_Tag(CONSTRUCTED | CONTEXT_SPECIFIC))
.decode(produced_at)
.decode_list(m_responses)
.decode_optional(extensions, ASN1_Tag(1),
ASN1_Tag(CONSTRUCTED | CONTEXT_SPECIFIC));
if(certs.empty())
{
if(auto cert = trusted_roots.find_cert(name, std::vector<byte>()))
certs.push_back(*cert);
else
throw Exception("Could not find certificate that signed OCSP response");
}
check_signature(tbs_bits, sig_algo, signature, trusted_roots, certs);
}
response_outer.end_cons();
}
Certificate_Status_Code Response::status_for(const X509_Certificate& issuer,
const X509_Certificate& subject) const
{
for(const auto& response : m_responses)
{
if(response.certid().is_id_for(issuer, subject))
{
X509_Time current_time(std::chrono::system_clock::now());
if(response.cert_status() == 1)
return Certificate_Status_Code::CERT_IS_REVOKED;
if(response.this_update() > current_time)
return Certificate_Status_Code::OCSP_NOT_YET_VALID;
if(response.next_update().time_is_set() && current_time > response.next_update())
return Certificate_Status_Code::OCSP_HAS_EXPIRED;
if(response.cert_status() == 0)
return Certificate_Status_Code::OCSP_RESPONSE_GOOD;
else
return Certificate_Status_Code::OCSP_BAD_STATUS;
}
}
return Certificate_Status_Code::OCSP_CERT_NOT_LISTED;
}
Response online_check(const X509_Certificate& issuer,
const X509_Certificate& subject,
const Certificate_Store* trusted_roots)
{
const std::string responder_url = subject.ocsp_responder();
if(responder_url.empty())
throw Exception("No OCSP responder specified");
OCSP::Request req(issuer, subject);
auto http = HTTP::POST_sync(responder_url,
"application/ocsp-request",
req.BER_encode());
http.throw_unless_ok();
// Check the MIME type?
OCSP::Response response(*trusted_roots, http.body());
return response;
}
}
}
|
