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Compute first pass for encryptedKey if keyType attribute is set

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This commit is contained in:
Grégory Soutadé
2022-08-27 15:44:27 +02:00
parent 56b3231f92
commit 7b8c7acbad
5 changed files with 153 additions and 42 deletions
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104
src/libgourou.cpp
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@@ -945,28 +945,95 @@ namespace gourou
void DRMProcessor::setLogLevel(int logLevel) {gourou::logLevel = (GOUROU_LOG_LEVEL)logLevel;}
void DRMProcessor::decryptADEPTKey(const std::string& encryptedKey, unsigned char* decryptedKey)
{
{
if (encryptedKey.size() != 172)
EXCEPTION(DRM_INVALID_KEY_SIZE, "Invalid encrypted key size (" << encryptedKey.size() << "). DRM version not supported");
ByteArray arrayEncryptedKey = ByteArray::fromBase64(encryptedKey);
std::string privateKeyData = user->getPrivateLicenseKey();
ByteArray privateRSAKey = ByteArray::fromBase64(privateKeyData);
ByteArray deviceKey(device->getDeviceKey(), Device::DEVICE_KEY_SIZE);
std::string pkcs12 = user->getPKCS12();
client->RSAPrivateDecrypt(privateRSAKey.data(), privateRSAKey.length(),
RSAInterface::RSA_KEY_PKCS12, deviceKey.toBase64().data(),
arrayEncryptedKey.data(), arrayEncryptedKey.length(), decryptedKey);
dumpBuffer(gourou::LG_LOG_DEBUG, "To decrypt : ", arrayEncryptedKey.data(), arrayEncryptedKey.length());
if (decryptedKey[0] != 0x00 || decryptedKey[1] != 0x02 ||
decryptedKey[RSA_KEY_SIZE-16-1] != 0x00)
EXCEPTION(DRM_ERR_ENCRYPTION_KEY, "Unable to retrieve encryption key");
client->RSAPrivateDecrypt(privateRSAKey.data(), privateRSAKey.length(),
RSAInterface::RSA_KEY_PKCS8, "",
arrayEncryptedKey.data(), arrayEncryptedKey.length(), decryptedKey);
}
/**
* RSA Key can be over encrypted with AES128-CBC if keyType attribute is set
* Key = SHA256(keyType)[14:22] || SHA256(keyType)[7:13]
* IV = DeviceID ^ FulfillmentId ^ VoucherId
*
* @return Base64 encoded decrypted key
*/
std::string DRMProcessor::encryptedKeyFirstPass(pugi::xml_document& rightsDoc, const std::string& encryptedKey, const std::string& keyType)
{
unsigned char digest[32], key[16], iv[16];
unsigned int dataOutLength;
std::string id;
client->digest("SHA256", (unsigned char*)keyType.c_str(), keyType.size(), digest);
memcpy(key, &digest[14], 9);
memcpy(&key[9], &digest[7], 7);
id = extractTextElem(rightsDoc, "/adept:rights/licenseToken/device");
if (id == "")
EXCEPTION(DRM_ERR_ENCRYPTION_KEY_FP, "Device id not found in rights.xml");
ByteArray deviceId = ByteArray::fromHex(extractIdFromUUID(id));
unsigned char* _deviceId = deviceId.data();
id = extractTextElem(rightsDoc, "/adept:rights/licenseToken/fulfillment");
if (id == "")
EXCEPTION(DRM_ERR_ENCRYPTION_KEY_FP, "Fulfillment id not found in rights.xml");
ByteArray fulfillmentId = ByteArray::fromHex(extractIdFromUUID(id));
unsigned char* _fulfillmentId = fulfillmentId.data();
id = extractTextElem(rightsDoc, "/adept:rights/licenseToken/voucher");
if (id == "")
EXCEPTION(DRM_ERR_ENCRYPTION_KEY_FP, "Voucher id not found in rights.xml");
ByteArray voucherId = ByteArray::fromHex(extractIdFromUUID(id));
unsigned char* _voucherId = voucherId.data();
if (deviceId.size() < sizeof(iv) || fulfillmentId.size() < sizeof(iv) || voucherId.size() < sizeof(iv))
EXCEPTION(DRM_ERR_ENCRYPTION_KEY_FP, "One id has a bad length");
for(unsigned int i=0; i<sizeof(iv); i++)
iv[i] = _deviceId[i] ^ _fulfillmentId[i] ^ _voucherId[i];
ByteArray arrayEncryptedKey = ByteArray::fromBase64(encryptedKey);
dumpBuffer(gourou::LG_LOG_DEBUG, "First pass key : ", key, sizeof(key));
dumpBuffer(gourou::LG_LOG_DEBUG, "First pass IV : ", iv, sizeof(iv));
unsigned char* clearRSAKey = new unsigned char[arrayEncryptedKey.size()];
client->Decrypt(CryptoInterface::ALGO_AES, CryptoInterface::CHAIN_CBC,
(const unsigned char*)key, (unsigned int)sizeof(key),
(const unsigned char*)iv, (unsigned int)sizeof(iv),
(const unsigned char*)arrayEncryptedKey.data(), arrayEncryptedKey.size(),
(unsigned char*)clearRSAKey, &dataOutLength);
dumpBuffer(gourou::LG_LOG_DEBUG, "\nDecrypted key : ", clearRSAKey, dataOutLength);
/* Last block could be 0x10*16 which is OpenSSL padding, remove it if it's the case */
bool skipLastLine = true;
for(unsigned int i=dataOutLength-16; i<dataOutLength; i++)
{
if (clearRSAKey[i] != 0x10)
{
skipLastLine = false;
break;
}
}
ByteArray res(clearRSAKey, (skipLastLine)?dataOutLength-16:dataOutLength);
delete[] clearRSAKey;
return res.toBase64();
}
void DRMProcessor::removeEPubDRM(const std::string& filenameIn, const std::string& filenameOut,
const unsigned char* encryptionKey, unsigned encryptionKeySize)
@@ -983,7 +1050,20 @@ namespace gourou
unsigned char decryptedKey[RSA_KEY_SIZE];
if (!encryptionKey)
{
std::string keyType = extractTextAttribute(rightsDoc, "/adept:rights/licenseToken/encryptedKey", "keyType", false);
if (keyType != "")
encryptedKey = encryptedKeyFirstPass(rightsDoc, encryptedKey, keyType);
decryptADEPTKey(encryptedKey, decryptedKey);
dumpBuffer(gourou::LG_LOG_DEBUG, "Decrypted : ", decryptedKey, RSA_KEY_SIZE);
if (decryptedKey[0] != 0x00 || decryptedKey[1] != 0x02 ||
decryptedKey[RSA_KEY_SIZE-16-1] != 0x00)
EXCEPTION(DRM_ERR_ENCRYPTION_KEY, "Unable to retrieve encryption key");
}
else
{
GOUROU_LOG(DEBUG, "Use provided encryption key");