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Compute over encrypted key also for PDF files

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This commit is contained in:
Grégory Soutadé 2022-09-04 09:25:06 +02:00
parent 2dbd4cc343
commit 6e3958f09e
2 changed files with 34 additions and 8 deletions
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2
include/libgourou.h
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@ -231,7 +231,7 @@ namespace gourou
void buildSignInRequest(pugi::xml_document& signInRequest, const std::string& adobeID, const std::string& adobePassword, const std::string& authenticationCertificate);
void fetchLicenseServiceCertificate(const std::string& licenseURL,
const std::string& operatorURL);
std::string encryptedKeyFirstPass(pugi::xml_document& rightsDoc, const std::string& encryptedKey, const std::string& keyType);
std::string encryptedKeyFirstPass(pugi::xml_document& rightsDoc, const std::string& encryptedKey, const std::string& keyType, ITEM_TYPE type);
void decryptADEPTKey(const std::string& encryptedKey, unsigned char* decryptedKey);
void removeEPubDRM(const std::string& filenameIn, const std::string& filenameOut, const unsigned char* encryptionKey, unsigned encryptionKeySize);
void generatePDFObjectKey(int version,

36
src/libgourou.cpp
View File

@ -963,20 +963,33 @@ namespace gourou
/**
* RSA Key can be over encrypted with AES128-CBC if keyType attribute is set
* Key = SHA256(keyType)[14:22] || SHA256(keyType)[7:13]
* For EPUB, Key = SHA256(keyType)[14:22] || SHA256(keyType)[7:13]
* For PDF, Key = SHA256(keyType)[6:19] || SHA256(keyType)[3:6]
* 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)
std::string DRMProcessor::encryptedKeyFirstPass(pugi::xml_document& rightsDoc, const std::string& encryptedKey, const std::string& keyType, ITEM_TYPE type)
{
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);
dumpBuffer(gourou::LG_LOG_DEBUG, "SHA of KeyType : ", digest, sizeof(digest));
switch(type)
{
case EPUB:
memcpy(key, &digest[14], 9);
memcpy(&key[9], &digest[7], 7);
break;
case PDF:
memcpy(key, &digest[6], 13);
memcpy(&key[13], &digest[3], 3);
break;
}
id = extractTextElem(rightsDoc, "/adept:rights/licenseToken/device");
if (id == "")
@ -1054,7 +1067,7 @@ namespace gourou
std::string keyType = extractTextAttribute(rightsDoc, "/adept:rights/licenseToken/encryptedKey", "keyType", false);
if (keyType != "")
encryptedKey = encryptedKeyFirstPass(rightsDoc, encryptedKey, keyType);
encryptedKey = encryptedKeyFirstPass(rightsDoc, encryptedKey, keyType, EPUB);
decryptADEPTKey(encryptedKey, decryptedKey);
@ -1245,7 +1258,20 @@ namespace gourou
std::string encryptedKey = extractTextElem(rightsDoc, "/adept:rights/licenseToken/encryptedKey");
if (!encryptionKey)
{
std::string keyType = extractTextAttribute(rightsDoc, "/adept:rights/licenseToken/encryptedKey", "keyType", false);
if (keyType != "")
encryptedKey = encryptedKeyFirstPass(rightsDoc, encryptedKey, keyType, PDF);
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");
@ -1314,7 +1340,7 @@ namespace gourou
GOUROU_LOG(DEBUG, "Decrypt string " << dictIt->first << " " << dataLength);
client->decrypt(CryptoInterface::ALGO_RC4, CryptoInterface::CHAIN_ECB,
tmpKey, 16, /* Key */
tmpKey, sizeof(tmpKey), /* Key */
NULL, 0, /* IV */
encryptedData, dataLength,
clearData, &dataOutLength);
@ -1347,7 +1373,7 @@ namespace gourou
GOUROU_LOG(DEBUG, "Decrypt stream id " << object->objectId() << ", size " << stream->dataLength());
client->decrypt(CryptoInterface::ALGO_RC4, CryptoInterface::CHAIN_ECB,
tmpKey, 16, /* Key */
tmpKey, sizeof(tmpKey), /* Key */
NULL, 0, /* IV */
encryptedData, dataLength,
clearData, &dataOutLength);