ocsp.cpp

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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/internal/parsing.h>
 
#if defined(BOTAN_HAS_HTTP_UTIL)
  #include <botan/internal/http_util.h>
#endif
 
namespace Botan::OCSP {
 
namespace {
 
// TODO: should this be in a header somewhere?
void decode_optional_list(BER_Decoder& ber,
                          ASN1_Type tag,
                          std::vector<X509_Certificate>& output)
   {
   BER_Object obj = ber.get_next_object();
 
   if(obj.is_a(tag, ASN1_Class::ContextSpecific | ASN1_Class::Constructed) == false)
      {
      ber.push_back(obj);
      return;
      }
 
   BER_Decoder list(obj);
 
   while(list.more_items())
      {
      BER_Object certbits = list.get_next_object();
      X509_Certificate cert(certbits.bits(), certbits.length());
      output.push_back(std::move(cert));
      }
   }
 
}
 
Request::Request(const X509_Certificate& issuer_cert,
                 const X509_Certificate& subject_cert) :
   m_issuer(issuer_cert),
   m_certid(m_issuer, BigInt::decode(subject_cert.serial_number()))
   {
   if(subject_cert.issuer_dn() != issuer_cert.subject_dn())
      throw Invalid_Argument("Invalid cert pair to OCSP::Request (mismatched issuer,subject args?)");
   }
 
Request::Request(const X509_Certificate& issuer_cert,
                 const BigInt& subject_serial) :
   m_issuer(issuer_cert),
   m_certid(m_issuer, subject_serial)
   {
   }
 
std::vector<uint8_t> Request::BER_encode() const
   {
   std::vector<uint8_t> output;
   DER_Encoder(output).start_sequence()
        .start_sequence()
          .start_explicit(0)
            .encode(static_cast<size_t>(0)) // version #
          .end_explicit()
            .start_sequence()
              .start_sequence()
                .encode(m_certid)
              .end_cons()
            .end_cons()
          .end_cons()
      .end_cons();
 
   return output;
   }
 
std::string Request::base64_encode() const
   {
   return Botan::base64_encode(BER_encode());
   }
 
Response::Response(Certificate_Status_Code status)
   {
   m_status = Response_Status_Code::Successful;
   m_dummy_response_status = status;
   }
 
Response::Response(const uint8_t response_bits[], size_t response_bits_len) :
   m_response_bits(response_bits, response_bits + response_bits_len)
   {
   m_dummy_response_status = Certificate_Status_Code::OCSP_RESPONSE_INVALID;
 
   BER_Decoder response_outer = BER_Decoder(m_response_bits).start_sequence();
 
   size_t resp_status = 0;
 
   response_outer.decode(resp_status, ASN1_Type::Enumerated, ASN1_Class::Universal);
 
   m_status = static_cast<Response_Status_Code>(resp_status);
 
   if(m_status != Response_Status_Code::Successful)
      { return; }
 
   if(response_outer.more_items())
      {
      BER_Decoder response_bytes =
         response_outer.start_context_specific(0).start_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_sequence();
 
      basicresponse.start_sequence()
           .raw_bytes(m_tbs_bits)
         .end_cons()
         .decode(m_sig_algo)
         .decode(m_signature, ASN1_Type::BitString);
      decode_optional_list(basicresponse, ASN1_Type(0), m_certs);
 
      size_t responsedata_version = 0;
      Extensions extensions;
 
      BER_Decoder(m_tbs_bits)
         .decode_optional(responsedata_version, ASN1_Type(0),
                          ASN1_Class::ContextSpecific | ASN1_Class::Constructed)
 
         .decode_optional(m_signer_name, ASN1_Type(1),
                          ASN1_Class::ContextSpecific | ASN1_Class::Constructed)
 
         .decode_optional_string(m_key_hash, ASN1_Type::OctetString, 2,
                                 ASN1_Class::ContextSpecific | ASN1_Class::Constructed)
 
         .decode(m_produced_at)
 
         .decode_list(m_responses)
 
         .decode_optional(extensions, ASN1_Type(1),
                          ASN1_Class::ContextSpecific | ASN1_Class::Constructed);
      }
 
   response_outer.end_cons();
   }
 
Certificate_Status_Code Response::verify_signature(const X509_Certificate& issuer) const
   {
   if (m_responses.empty())
      return m_dummy_response_status;
 
   try
      {
      std::unique_ptr<Public_Key> pub_key(issuer.subject_public_key());
 
      const std::vector<std::string> sig_info =
         split_on(m_sig_algo.get_oid().to_formatted_string(), '/');
 
      if(sig_info.size() != 2 || sig_info[0] != pub_key->algo_name())
         return Certificate_Status_Code::OCSP_RESPONSE_INVALID;
 
      std::string padding = sig_info[1];
      const Signature_Format format = pub_key->default_x509_signature_format();
 
      PK_Verifier verifier(*pub_key, padding, format);
 
      if(verifier.verify_message(ASN1::put_in_sequence(m_tbs_bits), m_signature))
         return Certificate_Status_Code::OCSP_SIGNATURE_OK;
      else
         return Certificate_Status_Code::OCSP_SIGNATURE_ERROR;
      }
   catch(Exception&)
      {
      return Certificate_Status_Code::OCSP_SIGNATURE_ERROR;
      }
   }
 
Certificate_Status_Code Response::check_signature(const std::vector<Certificate_Store*>& trusted_roots,
                                                  const std::vector<X509_Certificate>& ee_cert_path) const
   {
   if (m_responses.empty())
      return m_dummy_response_status;
 
   std::optional<X509_Certificate> signing_cert;
 
   for(const auto& trusted_root : trusted_roots)
      {
      if(m_signer_name.empty() && m_key_hash.empty())
         return Certificate_Status_Code::OCSP_RESPONSE_INVALID;
 
      if(!m_signer_name.empty())
         {
         signing_cert = trusted_root->find_cert(m_signer_name, std::vector<uint8_t>());
         if(signing_cert)
            {
            break;
            }
         }
 
      if(!m_key_hash.empty())
         {
         signing_cert = trusted_root->find_cert_by_pubkey_sha1(m_key_hash);
         if(signing_cert)
            {
            break;
            }
         }
      }
 
   if(!signing_cert && ee_cert_path.size() > 1)
      {
      // End entity cert is not allowed to sign their own OCSP request :)
      for(size_t i = 1; i < ee_cert_path.size(); ++i)
         {
         // Check all CA certificates in the (assumed validated) EE cert path
         if(!m_signer_name.empty() && ee_cert_path[i].subject_dn() == m_signer_name)
            {
            signing_cert = ee_cert_path[i];
            break;
            }
 
         if(!m_key_hash.empty() && ee_cert_path[i].subject_public_key_bitstring_sha1() == m_key_hash)
            {
            signing_cert = ee_cert_path[i];
            break;
            }
         }
      }
 
   if(!signing_cert && !m_certs.empty())
      {
      for(const auto& cert : m_certs)
         {
         // Check all CA certificates in the (assumed validated) EE cert path
         if(!m_signer_name.empty() && cert.subject_dn() == m_signer_name)
            {
            signing_cert = cert;
            break;
            }
 
         if(!m_key_hash.empty() && cert.subject_public_key_bitstring_sha1() == m_key_hash)
            {
            signing_cert = cert;
            break;
            }
         }
      }
 
   if(!signing_cert)
      return Certificate_Status_Code::OCSP_ISSUER_NOT_FOUND;
 
   if(!signing_cert->allowed_usage(CRL_SIGN) &&
      !signing_cert->allowed_extended_usage("PKIX.OCSPSigning"))
      {
      return Certificate_Status_Code::OCSP_RESPONSE_MISSING_KEYUSAGE;
      }
 
   return this->verify_signature(*signing_cert);
   }
 
Certificate_Status_Code Response::status_for(const X509_Certificate& issuer,
      const X509_Certificate& subject,
      std::chrono::system_clock::time_point ref_time,
      std::chrono::seconds max_age) const
   {
   if(m_responses.empty())
      { return m_dummy_response_status; }
 
   for(const auto& response : m_responses)
      {
      if(response.certid().is_id_for(issuer, subject))
         {
         X509_Time x509_ref_time(ref_time);
 
         if(response.cert_status() == 1)
            { return Certificate_Status_Code::CERT_IS_REVOKED; }
 
         if(response.this_update() > x509_ref_time)
            { return Certificate_Status_Code::OCSP_NOT_YET_VALID; }
 
         if(response.next_update().time_is_set())
            {
            if(x509_ref_time > response.next_update())
               { return Certificate_Status_Code::OCSP_HAS_EXPIRED; }
            }
         else if(max_age > std::chrono::seconds::zero() && ref_time - response.this_update().to_std_timepoint() > max_age)
            { return Certificate_Status_Code::OCSP_IS_TOO_OLD; }
 
         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;
   }
 
#if defined(BOTAN_HAS_HTTP_UTIL)
 
Response online_check(const X509_Certificate& issuer,
                      const BigInt& subject_serial,
                      const std::string& ocsp_responder,
                      Certificate_Store* trusted_roots,
                      std::chrono::milliseconds timeout)
   {
   if(ocsp_responder.empty())
      throw Invalid_Argument("No OCSP responder specified");
 
   OCSP::Request req(issuer, subject_serial);
 
   auto http = HTTP::POST_sync(ocsp_responder,
                               "application/ocsp-request",
                               req.BER_encode(),
                               1,
                               timeout);
 
   http.throw_unless_ok();
 
   // Check the MIME type?
 
   OCSP::Response response(http.body());
 
   std::vector<Certificate_Store*> trusted_roots_vec;
   trusted_roots_vec.push_back(trusted_roots);
 
   if(trusted_roots)
      response.check_signature(trusted_roots_vec);
 
   return response;
   }
 
 
Response online_check(const X509_Certificate& issuer,
                      const X509_Certificate& subject,
                      Certificate_Store* trusted_roots,
                      std::chrono::milliseconds timeout)
   {
   if(subject.issuer_dn() != issuer.subject_dn())
      throw Invalid_Argument("Invalid cert pair to OCSP::online_check (mismatched issuer,subject args?)");
 
   return online_check(issuer,
                       BigInt::decode(subject.serial_number()),
                       subject.ocsp_responder(),
                       trusted_roots,
                       timeout);
   }
 
#endif
 
}