// Copyright (c) 2010 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#include "net/base/keygen_handler.h"

#include <windows.h>
#include <wincrypt.h>
#pragma comment(lib, "crypt32.lib")
#include <rpc.h>
#pragma comment(lib, "rpcrt4.lib")

#include <list>
#include <string>
#include <vector>

#include "base/base64.h"
#include "base/basictypes.h"
#include "base/crypto/capi_util.h"
#include "base/logging.h"
#include "base/string_piece.h"
#include "base/string_util.h"
#include "base/utf_string_conversions.h"

namespace net {

// Assigns the contents of a CERT_PUBLIC_KEY_INFO structure for the signing
// key in |prov| to |output|. Returns true if encoding was successful.
bool GetSubjectPublicKeyInfo(HCRYPTPROV prov, std::vector<BYTE>* output) {
  BOOL ok;
  DWORD size = 0;

  // From the private key stored in HCRYPTPROV, obtain the public key, stored
  // as a CERT_PUBLIC_KEY_INFO structure. Currently, only RSA public keys are
  // supported.
  ok = CryptExportPublicKeyInfoEx(prov, AT_KEYEXCHANGE, X509_ASN_ENCODING,
                                  szOID_RSA_RSA, 0, NULL, NULL, &size);
  DCHECK(ok);
  if (!ok)
    return false;

  output->resize(size);

  PCERT_PUBLIC_KEY_INFO public_key_casted =
      reinterpret_cast<PCERT_PUBLIC_KEY_INFO>(&(*output)[0]);
  ok = CryptExportPublicKeyInfoEx(prov, AT_KEYEXCHANGE, X509_ASN_ENCODING,
                                  szOID_RSA_RSA, 0, NULL, public_key_casted,
                                  &size);
  DCHECK(ok);
  if (!ok)
    return false;

  output->resize(size);

  return true;
}

// Generates a DER encoded SignedPublicKeyAndChallenge structure from the
// signing key of |prov| and the specified ASCII |challenge| string and
// appends it to |output|.
// True if the encoding was successfully generated.
bool GetSignedPublicKeyAndChallenge(HCRYPTPROV prov,
                                    const std::string& challenge,
                                    std::string* output) {
  std::wstring wide_challenge = ASCIIToWide(challenge);
  std::vector<BYTE> spki;

  if (!GetSubjectPublicKeyInfo(prov, &spki))
    return false;

  // PublicKeyAndChallenge ::= SEQUENCE {
  //     spki SubjectPublicKeyInfo,
  //     challenge IA5STRING
  // }
  CERT_KEYGEN_REQUEST_INFO pkac;
  pkac.dwVersion = CERT_KEYGEN_REQUEST_V1;
  pkac.SubjectPublicKeyInfo =
      *reinterpret_cast<PCERT_PUBLIC_KEY_INFO>(&spki[0]);
  pkac.pwszChallengeString = const_cast<wchar_t*>(wide_challenge.c_str());

  CRYPT_ALGORITHM_IDENTIFIER sig_alg;
  memset(&sig_alg, 0, sizeof(sig_alg));
  sig_alg.pszObjId = szOID_RSA_MD5RSA;

  BOOL ok;
  DWORD size = 0;
  std::vector<BYTE> signed_pkac;
  ok = CryptSignAndEncodeCertificate(prov, AT_KEYEXCHANGE, X509_ASN_ENCODING,
                                     X509_KEYGEN_REQUEST_TO_BE_SIGNED,
                                     &pkac, &sig_alg, NULL,
                                     NULL, &size);
  DCHECK(ok);
  if (!ok)
    return false;

  signed_pkac.resize(size);
  ok = CryptSignAndEncodeCertificate(prov, AT_KEYEXCHANGE, X509_ASN_ENCODING,
                                     X509_KEYGEN_REQUEST_TO_BE_SIGNED,
                                     &pkac, &sig_alg, NULL,
                                     &signed_pkac[0], &size);
  DCHECK(ok);
  if (!ok)
    return false;

  output->assign(reinterpret_cast<char*>(&signed_pkac[0]), size);
  return true;
}

// Generates a unique name for the container which will store the key that is
// generated. The traditional Windows approach is to use a GUID here.
std::wstring GetNewKeyContainerId() {
  RPC_STATUS status = RPC_S_OK;
  std::wstring result;

  UUID id = { 0 };
  status = UuidCreateSequential(&id);
  if (status != RPC_S_OK && status != RPC_S_UUID_LOCAL_ONLY)
    return result;

  RPC_WSTR rpc_string = NULL;
  status = UuidToString(&id, &rpc_string);
  if (status != RPC_S_OK)
    return result;

  // RPC_WSTR is unsigned short*.  wchar_t is a built-in type of Visual C++,
  // so the type cast is necessary.
  result.assign(reinterpret_cast<wchar_t*>(rpc_string));
  RpcStringFree(&rpc_string);

  return result;
}

std::string KeygenHandler::GenKeyAndSignChallenge() {
  std::string result;

  bool is_success = true;
  HCRYPTPROV prov = NULL;
  HCRYPTKEY key = NULL;
  DWORD flags = (key_size_in_bits_ << 16) | CRYPT_EXPORTABLE;
  std::string spkac;

  std::wstring new_key_id;

  // TODO(rsleevi): Have the user choose which provider they should use, which
  // needs to be filtered by those providers which can provide the key type
  // requested or the key size requested. This is especially important for
  // generating certificates that will be stored on smart cards.
  const int kMaxAttempts = 5;
  BOOL ok = FALSE;
  for (int attempt = 0; attempt < kMaxAttempts; ++attempt) {
    // Per MSDN documentation for CryptAcquireContext, if applications will be
    // creating their own keys, they should ensure unique naming schemes to
    // prevent overlap with any other applications or consumers of CSPs, and
    // *should not* store new keys within the default, NULL key container.
    new_key_id = GetNewKeyContainerId();
    if (new_key_id.empty())
      return result;

    // Only create new key containers, so that existing key containers are not
    // overwritten.
    ok = base::CryptAcquireContextLocked(&prov, new_key_id.c_str(), NULL,
                                         PROV_RSA_FULL,
                                         CRYPT_SILENT | CRYPT_NEWKEYSET);

    if (ok || GetLastError() != NTE_BAD_KEYSET)
      break;
  }
  if (!ok) {
    LOG(ERROR) << "Couldn't acquire a CryptoAPI provider context: "
               << GetLastError();
    is_success = false;
    goto failure;
  }

  if (!CryptGenKey(prov, CALG_RSA_KEYX, flags, &key)) {
    LOG(ERROR) << "Couldn't generate an RSA key";
    is_success = false;
    goto failure;
  }

  if (!GetSignedPublicKeyAndChallenge(prov, challenge_, &spkac)) {
    LOG(ERROR) << "Couldn't generate the signed public key and challenge";
    is_success = false;
    goto failure;
  }

  if (!base::Base64Encode(spkac, &result)) {
    LOG(ERROR) << "Couldn't convert signed key into base64";
    is_success = false;
    goto failure;
  }

 failure:
  if (!is_success) {
    LOG(ERROR) << "SSL Keygen failed";
  } else {
    LOG(INFO) << "SSL Key succeeded";
  }
  if (key) {
    // Securely destroys the handle, but leaves the underlying key alone. The
    // key can be obtained again by resolving the key location. If
    // |stores_key_| is false, the underlying key will be destroyed below.
    CryptDestroyKey(key);
  }

  if (prov) {
    CryptReleaseContext(prov, 0);
    prov = NULL;
    if (!stores_key_) {
      // Fully destroys any of the keys that were created and releases prov.
      base::CryptAcquireContextLocked(&prov, new_key_id.c_str(), NULL,
                                      PROV_RSA_FULL,
                                      CRYPT_SILENT | CRYPT_DELETEKEYSET);
    }
  }

  return result;
}

}  // namespace net