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/*
* 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;
Null_RNG null_rng;
PK_Verifier verifier(*pub_key, null_rng, 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<std::shared_ptr<const 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;
}
}
}
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