/*
* X.509 Certificates
* (C) 1999-2007 Jack Lloyd
*
* Distributed under the terms of the Botan license
*/

#include <botan/x509cert.h>
#include <botan/x509_ext.h>
#include <botan/der_enc.h>
#include <botan/ber_dec.h>
#include <botan/stl_util.h>
#include <botan/parsing.h>
#include <botan/bigint.h>
#include <botan/oids.h>
#include <botan/pem.h>
#include <algorithm>

namespace Botan {

namespace {

/*
* Lookup each OID in the vector
*/
std::vector<std::string> lookup_oids(const std::vector<std::string>& in)
   {
   std::vector<std::string> out;

   for(auto i = in.begin(); i != in.end(); ++i)
      out.push_back(OIDS::lookup(OID(*i)));
   return out;
   }

}

/*
* X509_Certificate Constructor
*/
X509_Certificate::X509_Certificate(DataSource& in) :
   X509_Object(in, "CERTIFICATE/X509 CERTIFICATE")
   {
   self_signed = false;
   do_decode();
   }

/*
* X509_Certificate Constructor
*/
X509_Certificate::X509_Certificate(const std::string& in) :
   X509_Object(in, "CERTIFICATE/X509 CERTIFICATE")
   {
   self_signed = false;
   do_decode();
   }

/*
* Decode the TBSCertificate data
*/
void X509_Certificate::force_decode()
   {
   u32bit version;
   BigInt serial_bn;
   AlgorithmIdentifier sig_algo_inner;
   X509_DN dn_issuer, dn_subject;
   X509_Time start, end;

   BER_Decoder tbs_cert(tbs_bits);

   tbs_cert.decode_optional(version, ASN1_Tag(0),
                            ASN1_Tag(CONSTRUCTED | CONTEXT_SPECIFIC))
      .decode(serial_bn)
      .decode(sig_algo_inner)
      .decode(dn_issuer)
      .start_cons(SEQUENCE)
         .decode(start)
         .decode(end)
         .verify_end()
      .end_cons()
      .decode(dn_subject);

   if(version > 2)
      throw Decoding_Error("Unknown X.509 cert version " + to_string(version));
   if(sig_algo != sig_algo_inner)
      throw Decoding_Error("Algorithm identifier mismatch");

   self_signed = (dn_subject == dn_issuer);

   subject.add(dn_subject.contents());
   issuer.add(dn_issuer.contents());

   BER_Object public_key = tbs_cert.get_next_object();
   if(public_key.type_tag != SEQUENCE || public_key.class_tag != CONSTRUCTED)
      throw BER_Bad_Tag("X509_Certificate: Unexpected tag for public key",
                        public_key.type_tag, public_key.class_tag);

   MemoryVector<byte> v2_issuer_key_id, v2_subject_key_id;

   tbs_cert.decode_optional_string(v2_issuer_key_id, BIT_STRING, 1);
   tbs_cert.decode_optional_string(v2_subject_key_id, BIT_STRING, 2);

   BER_Object v3_exts_data = tbs_cert.get_next_object();
   if(v3_exts_data.type_tag == 3 &&
      v3_exts_data.class_tag == ASN1_Tag(CONSTRUCTED | CONTEXT_SPECIFIC))
      {
      Extensions extensions;

      BER_Decoder(v3_exts_data.value).decode(extensions).verify_end();

      extensions.contents_to(subject, issuer);
      }
   else if(v3_exts_data.type_tag != NO_OBJECT)
      throw BER_Bad_Tag("Unknown tag in X.509 cert",
                        v3_exts_data.type_tag, v3_exts_data.class_tag);

   if(tbs_cert.more_items())
      throw Decoding_Error("TBSCertificate has more items that expected");

   subject.add("X509.Certificate.version", version);
   subject.add("X509.Certificate.serial", BigInt::encode(serial_bn));
   subject.add("X509.Certificate.start", start.readable_string());
   subject.add("X509.Certificate.end", end.readable_string());

   issuer.add("X509.Certificate.v2.key_id", v2_issuer_key_id);
   subject.add("X509.Certificate.v2.key_id", v2_subject_key_id);

   subject.add("X509.Certificate.public_key",
               PEM_Code::encode(
                  ASN1::put_in_sequence(public_key.value),
                  "PUBLIC KEY"
                  )
      );

   if(is_CA_cert() &&
      !subject.has_value("X509v3.BasicConstraints.path_constraint"))
      {
      u32bit limit = (x509_version() < 3) ? NO_CERT_PATH_LIMIT : 0;
      subject.add("X509v3.BasicConstraints.path_constraint", limit);
      }
   }

/*
* Return the X.509 version in use
*/
u32bit X509_Certificate::x509_version() const
   {
   return (subject.get1_u32bit("X509.Certificate.version") + 1);
   }

/*
* Return the time this cert becomes valid
*/
std::string X509_Certificate::start_time() const
   {
   return subject.get1("X509.Certificate.start");
   }

/*
* Return the time this cert becomes invalid
*/
std::string X509_Certificate::end_time() const
   {
   return subject.get1("X509.Certificate.end");
   }

/*
* Return information about the subject
*/
std::vector<std::string>
X509_Certificate::subject_info(const std::string& what) const
   {
   return subject.get(X509_DN::deref_info_field(what));
   }

/*
* Return information about the issuer
*/
std::vector<std::string>
X509_Certificate::issuer_info(const std::string& what) const
   {
   return issuer.get(X509_DN::deref_info_field(what));
   }

/*
* Return the public key in this certificate
*/
Public_Key* X509_Certificate::subject_public_key() const
   {
   DataSource_Memory source(subject.get1("X509.Certificate.public_key"));
   return X509::load_key(source);
   }

/*
* Check if the certificate is for a CA
*/
bool X509_Certificate::is_CA_cert() const
   {
   if(!subject.get1_u32bit("X509v3.BasicConstraints.is_ca"))
      return false;
   if((constraints() & KEY_CERT_SIGN) || (constraints() == NO_CONSTRAINTS))
      return true;
   return false;
   }

/*
* Return the path length constraint
*/
u32bit X509_Certificate::path_limit() const
   {
   return subject.get1_u32bit("X509v3.BasicConstraints.path_constraint", 0);
   }

/*
* Return the key usage constraints
*/
Key_Constraints X509_Certificate::constraints() const
   {
   return Key_Constraints(subject.get1_u32bit("X509v3.KeyUsage",
                                              NO_CONSTRAINTS));
   }

/*
* Return the list of extended key usage OIDs
*/
std::vector<std::string> X509_Certificate::ex_constraints() const
   {
   return lookup_oids(subject.get("X509v3.ExtendedKeyUsage"));
   }

/*
* Return the list of certificate policies
*/
std::vector<std::string> X509_Certificate::policies() const
   {
   return lookup_oids(subject.get("X509v3.CertificatePolicies"));
   }

/*
* Return the authority key id
*/
MemoryVector<byte> X509_Certificate::authority_key_id() const
   {
   return issuer.get1_memvec("X509v3.AuthorityKeyIdentifier");
   }

/*
* Return the subject key id
*/
MemoryVector<byte> X509_Certificate::subject_key_id() const
   {
   return subject.get1_memvec("X509v3.SubjectKeyIdentifier");
   }

/*
* Return the certificate serial number
*/
MemoryVector<byte> X509_Certificate::serial_number() const
   {
   return subject.get1_memvec("X509.Certificate.serial");
   }

/*
* Return the distinguished name of the issuer
*/
X509_DN X509_Certificate::issuer_dn() const
   {
   return create_dn(issuer);
   }

/*
* Return the distinguished name of the subject
*/
X509_DN X509_Certificate::subject_dn() const
   {
   return create_dn(subject);
   }

/*
* Compare two certificates for equality
*/
bool X509_Certificate::operator==(const X509_Certificate& other) const
   {
   return (sig == other.sig &&
           sig_algo == other.sig_algo &&
           self_signed == other.self_signed &&
           issuer == other.issuer &&
           subject == other.subject);
   }

/*
* X.509 Certificate Comparison
*/
bool operator!=(const X509_Certificate& cert1, const X509_Certificate& cert2)
   {
   return !(cert1 == cert2);
   }

/*
* Create and populate a X509_DN
*/
X509_DN create_dn(const Data_Store& info)
   {
   auto names = info.search_for(
      [](const std::string& key, const std::string&)
      {
         return (key.find("X520.") != std::string::npos);
      });

   X509_DN dn;

   for(auto i = names.begin(); i != names.end(); ++i)
      dn.add_attribute(i->first, i->second);

   return dn;
   }

/*
* Create and populate an AlternativeName
*/
AlternativeName create_alt_name(const Data_Store& info)
   {
   auto names = info.search_for(
      [](const std::string& key, const std::string&)
      {
         return (key == "RFC822" ||
                 key == "DNS" ||
                 key == "URI" ||
                 key == "IP");
      });

   AlternativeName alt_name;

   for(auto i = names.begin(); i != names.end(); ++i)
      alt_name.add_attribute(i->first, i->second);

   return alt_name;
   }

}