1 files changed, 251 insertions, 0 deletions
diff --git a/src/lib/x509/ocsp.cpp b/src/lib/x509/ocsp.cpp
new file mode 100644
index 000000000..761c5b436
--- /dev/null
+++ b/src/lib/x509/ocsp.cpp
@@ -0,0 +1,251 @@
+/*
+* 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<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;
+   }
+
+}
+
+}