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Session key importing honours MSDN recommendation about exponent-one key usage

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This commit is contained in:
Simon Rozman 2016-08-14 12:44:49 +02:00
parent d1925a0704
commit 47653492a2
3 changed files with 88 additions and 39 deletions
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41
lib/TLS/include/Method.h
View File

@ -443,43 +443,20 @@ namespace eap
///
/// Creates a key
///
/// \sa [How to export and import plain text session keys by using CryptoAPI](https://support.microsoft.com/en-us/kb/228786)
///
/// \param[in] alg Key algorithm
/// \param[in] secret Raw key data
/// \param[in] key Key that decrypts \p secret
/// \param[in] secret Key data
/// \param[in] size_secret \p secret size
///
/// \returns Key
///
inline HCRYPTKEY create_key(
_In_ ALG_ID alg,
_In_bytecount_(size_secret) const void *secret,
_In_ size_t size_secret)
{
assert(size_secret <= 0xffffffff);
// Prepare exported key BLOB.
struct key_blob_prefix {
PUBLICKEYSTRUC header;
DWORD size;
} const prefix = {
{
PLAINTEXTKEYBLOB,
CUR_BLOB_VERSION,
0,
alg,
},
(DWORD)size_secret,
};
sanitizing_blob key_blob;
key_blob.reserve(sizeof(key_blob_prefix) + size_secret);
key_blob.assign((const unsigned char*)&prefix, (const unsigned char*)(&prefix + 1));
key_blob.insert(key_blob.end(), (const unsigned char*)secret, (const unsigned char*)secret + size_secret);
// Import the key.
winstd::crypt_key key;
if (!key.import(m_cp, key_blob.data(), (DWORD)key_blob.size(), NULL, 0))
throw winstd::win_runtime_error(__FUNCTION__ " Error importing key.");
return key.detach();
}
HCRYPTKEY create_key(
_In_ ALG_ID alg,
_In_ HCRYPTKEY key,
_In_bytecount_(size_secret) const void *secret,
_In_ size_t size_secret);
protected:
config_method_tls &m_cfg; ///< EAP-TLS method configuration

84
lib/TLS/src/Method.cpp
View File

@ -811,9 +811,8 @@ eap::sanitizing_blob eap::method_tls::make_message(_In_ tls_message_type_t type,
void eap::method_tls::derive_keys()
{
sanitizing_blob seed;
static const unsigned char s_label[] = "key expansion";
seed.assign(s_label, s_label + _countof(s_label) - 1);
sanitizing_blob seed(s_label, s_label + _countof(s_label) - 1);
seed.insert(seed.end(), (const unsigned char*)&m_state.m_random_server, (const unsigned char*)(&m_state.m_random_server + 1));
seed.insert(seed.end(), (const unsigned char*)&m_state.m_random_client, (const unsigned char*)(&m_state.m_random_client + 1));
@ -833,12 +832,18 @@ void eap::method_tls::derive_keys()
//hash_hmac::inner_padding(m_cp, m_state.m_alg_mac, _key_block, m_state.m_size_mac_key, m_padding_hmac_server.data());
_key_block += m_state.m_size_mac_key;
// Microsoft CryptoAPI does not support importing clear text session keys.
// Therefore, we trick it to say the session key is "encrypted" with an exponent-of-one key.
crypt_key key_exp1;
if (!key_exp1.create_exp1(m_cp, AT_KEYEXCHANGE))
throw win_runtime_error(__FUNCTION__ " Error creating exponent-of-one key.");
// client_write_key
m_key_client = create_key(m_state.m_alg_encrypt, _key_block, m_state.m_size_enc_key);
m_key_client = create_key(m_state.m_alg_encrypt, key_exp1, _key_block, m_state.m_size_enc_key);
_key_block += m_state.m_size_enc_key;
// server_write_key
m_key_server = create_key(m_state.m_alg_encrypt, _key_block, m_state.m_size_enc_key);
m_key_server = create_key(m_state.m_alg_encrypt, key_exp1, _key_block, m_state.m_size_enc_key);
_key_block += m_state.m_size_enc_key;
// client_write_IV
@ -855,9 +860,8 @@ void eap::method_tls::derive_keys()
void eap::method_tls::derive_msk()
{
sanitizing_blob seed;
static const unsigned char s_label[] = "client EAP encryption";
seed.assign(s_label, s_label + _countof(s_label) - 1);
sanitizing_blob seed(s_label, s_label + _countof(s_label) - 1);
seed.insert(seed.end(), (const unsigned char*)&m_state.m_random_client, (const unsigned char*)(&m_state.m_random_client + 1));
seed.insert(seed.end(), (const unsigned char*)&m_state.m_random_server, (const unsigned char*)(&m_state.m_random_server + 1));
sanitizing_blob key_block(prf(m_state.m_master_secret, seed, 2*sizeof(tls_random)));
@ -1388,3 +1392,71 @@ eap::sanitizing_blob eap::method_tls::prf(
return data;
}
HCRYPTKEY eap::method_tls::create_key(
_In_ ALG_ID alg,
_In_ HCRYPTKEY key,
_In_bytecount_(size_secret) const void *secret,
_In_ size_t size_secret)
{
if (size_secret > m_state.m_size_enc_key)
throw invalid_argument(__FUNCTION__ " Secret too big to fit the key.");
// Get private key's algorithm.
ALG_ID alg_key;
if (!CryptGetKeyParam(key, KP_ALGID, alg_key, 0))
throw win_runtime_error(__FUNCTION__ " Error getting key's algorithm.'");
// Get private key's length in bytes.
DWORD size_key = CryptGetKeyParam(key, KP_KEYLEN, size_key, 0) ? size_key/8 : 0;
// SIMPLEBLOB Format is documented in SDK
// Copy header to buffer
#pragma pack(push)
#pragma pack(1)
struct key_blob_prefix {
PUBLICKEYSTRUC header;
ALG_ID alg;
} const prefix = {
{
SIMPLEBLOB,
CUR_BLOB_VERSION,
0,
alg,
},
alg_key,
};
#pragma pack(pop)
sanitizing_blob key_blob;
key_blob.reserve(sizeof(key_blob_prefix) + size_key);
key_blob.assign((const unsigned char*)&prefix, (const unsigned char*)(&prefix + 1));
// Key in EME-PKCS1-v1_5 (RFC 3447).
key_blob.push_back(0); // Initial zero
key_blob.push_back(2); // PKCS #1 block type = 2
// PS
size_t size_ps = size_key - size_secret - 3;
assert(size_ps >= 8);
key_blob.insert(key_blob.end(), size_ps, 0);
unsigned char *ps = &*(key_blob.end() - size_ps);
CryptGenRandom(m_cp, (DWORD)size_ps, ps);
for (size_t i = 0; i < size_ps; i++)
if (ps[i] == 0) ps[i] = 1;
key_blob.push_back(0); // PS and M zero delimiter
// M
key_blob.insert(key_blob.end(), (const unsigned char*)secret, (const unsigned char*)secret + size_secret);
#ifdef _HOST_LOW_ENDIAN
std::reverse(key_blob.end() - size_key, key_blob.end());
#endif
// Import the key.
winstd::crypt_key key_out;
if (!key_out.import(m_cp, key_blob.data(), (DWORD)key_blob.size(), key, CRYPT_NO_SALT))
throw winstd::win_runtime_error(__FUNCTION__ " Error importing key.");
return key_out.detach();
}

2
lib/WinStd

@ -1 +1 @@
Subproject commit 84e544c2f6dbf14f76b930b2672c3cc2b77bfc3f
Subproject commit 25c886754dafdf0d7fef2dc9d28f5328d2bf7ddd