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// Copyright (c) 2011 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/logging.h"
#include "base/strings/string_piece.h"
#include "base/strings/string_util.h"
#include "base/strings/utf_string_conversions.h"
#include "crypto/capi_util.h"
#include "crypto/scoped_capi_types.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,
const_cast<char*>(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,
const_cast<char*>(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 = base::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 = const_cast<char*>(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;
}
// This is a helper struct designed to optionally delete a key after releasing
// the associated provider.
struct KeyContainer {
public:
explicit KeyContainer(bool delete_keyset)
: delete_keyset_(delete_keyset) {}
~KeyContainer() {
if (provider_) {
provider_.reset();
if (delete_keyset_ && !key_id_.empty()) {
HCRYPTPROV provider;
crypto::CryptAcquireContextLocked(&provider, key_id_.c_str(), NULL,
PROV_RSA_FULL, CRYPT_SILENT | CRYPT_DELETEKEYSET);
}
}
}
crypto::ScopedHCRYPTPROV provider_;
std::wstring key_id_;
private:
bool delete_keyset_;
};
std::string KeygenHandler::GenKeyAndSignChallenge() {
KeyContainer key_container(!stores_key_);
// 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;
int attempt;
for (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.
key_container.key_id_ = GetNewKeyContainerId();
if (key_container.key_id_.empty())
return std::string();
// Only create new key containers, so that existing key containers are not
// overwritten.
if (crypto::CryptAcquireContextLocked(key_container.provider_.receive(),
key_container.key_id_.c_str(), NULL, PROV_RSA_FULL,
CRYPT_SILENT | CRYPT_NEWKEYSET))
break;
if (GetLastError() != NTE_BAD_KEYSET) {
LOG(ERROR) << "Keygen failed: Couldn't acquire a CryptoAPI provider "
"context: " << GetLastError();
return std::string();
}
}
if (attempt == kMaxAttempts) {
LOG(ERROR) << "Keygen failed: Couldn't acquire a CryptoAPI provider "
"context: Max retries exceeded";
return std::string();
}
{
crypto::ScopedHCRYPTKEY key;
if (!CryptGenKey(key_container.provider_, CALG_RSA_KEYX,
(key_size_in_bits_ << 16) | CRYPT_EXPORTABLE, key.receive())) {
LOG(ERROR) << "Keygen failed: Couldn't generate an RSA key";
return std::string();
}
std::string spkac;
if (!GetSignedPublicKeyAndChallenge(key_container.provider_, challenge_,
&spkac)) {
LOG(ERROR) << "Keygen failed: Couldn't generate the signed public key "
"and challenge";
return std::string();
}
std::string result;
base::Base64Encode(spkac, &result);
VLOG(1) << "Keygen succeeded";
return result;
}
}
} // namespace net
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