【发布时间】：2016-04-21 11:22:51
【问题描述】：
我正在开发一个电子阅读器应用程序（使用skyepub），它基本上将加密的书籍下载到文件系统中（并将解密密钥保存在数据库中），当用户尝试阅读它时它会加载书进入内存并解密。
问题是有些书的第一章被截断了（epub 书实际上是 zip 文件，每一章都是一个单独的文件）。这导致了这个可怕的错误：
此 XML 文件似乎没有任何与之关联的样式信息。文档树如下所示
我尝试了什么
我已验证加密的书已正确下载，b/c 如果我将文件复制到我的桌面（从我的根 android）并在其上运行此命令：
openssl aes-192-cbc -d -K *** -iv *** -in test.epub.encrypted -out test.epub
它工作得很好。但是，如果我几乎尝试对以下 android 代码做同样的事情
public ContentData getContentData(String baseDirectory, String contentPath) {
if( contentPath.startsWith("/fonts/")) {
... // handle font suff
}
int secondSlash = contentPath.indexOf('/', 1);
if( secondSlash == -1) return null;
String bookEditionID = contentPath.substring(1,secondSlash);
String zipEntryName = contentPath.substring(secondSlash+1);
final ContentData data = new ContentData();
try {
InputStream stream = dbUtil.getBookStream(bookEditionID);
if( stream == null) return null;
final ZipInputStream zip = new ZipInputStream(stream);
ZipEntry entry;
do {
entry = zip.getNextEntry();
Log.e("Abjjad","looping through entry: "+entry);
if( entry == null) {
zip.close();
return null;
}
} while( !entry.getName().equals(zipEntryName));
Log.e("debug","going through data with entry: " +entry+", contentLength: "+entry.getSize());
见方法dbUtil.getBookStream：
public InputStream getBookStream( String bookEditionId) {
BookInfo book = getBookInfo(bookEditionId);
InputStream origStream = null;
try {
// Open the downloaded ePub
origStream = openFileInput(bookEditionId + ".epub");
// De-obfuscate the key
SecretKeySpec sks = getObfuscationKeySpec(bookEditionId);
Cipher c = Cipher.getInstance("AES/ECB/PKCS5Padding", "BC");
c.init(Cipher.DECRYPT_MODE, sks);
byte[] decodedBytes = c.doFinal(Base64.decode(book.decryptionKey, Base64.DEFAULT));
String keyPair = new String(decodedBytes);
// Split the key and parse into binary
int separator = keyPair.indexOf(':');
byte[] key = DatatypeConverter.parseHexBinary(keyPair.substring(0, separator));
byte[] iv = DatatypeConverter.parseHexBinary(keyPair.substring(separator + 1));
c = Cipher.getInstance("AES/CBC/PKCS7Padding","BC");
c.init(Cipher.DECRYPT_MODE, new SecretKeySpec(key,"AES"), new IvParameterSpec(iv));
return new CipherInputStream(origStream, c);
} catch( Exception e) {
try {
if (origStream != null) origStream.close();
} catch( Exception x) {}
return null;
}
}
然后entry.getSize()的日志在第一个代码块中返回-1。
奖金（适用于 iOS！）
我们在 iOS 中编写了相同的代码，并且运行良好（在同一本书上）：
+ (NSData *)encryptKey:(NSString *)key ivParam:(NSString *)iv bookId:(NSString *)bookId
{
NSString *keyPair = [NSString stringWithFormat:@"%@:%@", key, iv];
NSString *secret = [self getObfuscationSecretWithValue:bookId];
NSData *data = [keyPair dataUsingEncoding:NSASCIIStringEncoding];
char keyPtr[kCCKeySizeAES128];
bzero(keyPtr, sizeof(keyPtr));
[[NSData dataWithHexString:secret] getBytes:keyPtr length:sizeof(keyPtr)];
NSUInteger dataLength = [data length];
size_t bufferSize = dataLength + kCCBlockSizeAES128;
void *buffer = malloc(bufferSize);
size_t numBytesEncrypted;
CCCryptorStatus status = CCCrypt(kCCEncrypt, kCCAlgorithmAES, kCCOptionPKCS7Padding | kCCOptionECBMode, keyPtr, kCCKeySizeAES128,
NULL,
[data bytes], [data length],
buffer, bufferSize, &numBytesEncrypted);
if (status == kCCSuccess) {
return [NSData dataWithBytes:buffer length:numBytesEncrypted];
}
else {
free(buffer);
return nil;
}
}
更新
我注意到这种截断仅在阅读目录后发生（这似乎是上面的 最后一个章？）..来自日志：
:::::::::::::::::::::::::::::::
getInputStream: /24748681/OEBPS/toc.ncx
:::::::::::::::::::::::::::::::
looping through entry: mimetype
looping through entry: OEBPS/hayat-ghayr.html
looping through entry: OEBPS/content.opf
looping through entry: OEBPS/images/978-614-425-313-7-hayat-ghayr-cover.png
looping through entry: OEBPS/images/978-614-425-313-7-hayat_fmt.png
looping through entry: OEBPS/template.css
looping through entry: OEBPS/hayat-ghayr-2.html
looping through entry: OEBPS/hayat-ghayr-1.html
looping through entry: OEBPS/hayat-ghayr-3.html
looping through entry: OEBPS/hayat-ghayr-4.html
looping through entry: OEBPS/hayat-ghayr-5.html
looping through entry: OEBPS/hayat-ghayr-6.html
looping through entry: OEBPS/hayat-ghayr-7.html
looping through entry: OEBPS/hayat-ghayr-8.html
looping through entry: OEBPS/hayat-ghayr-9.html
looping through entry: OEBPS/hayat-ghayr-10.html
looping through entry: OEBPS/hayat-ghayr-11.html
looping through entry: OEBPS/hayat-ghayr-12.html
looping through entry: OEBPS/hayat-ghayr-13.html
looping through entry: OEBPS/hayat-ghayr-14.html
looping through entry: OEBPS/hayat-ghayr-15.html
looping through entry: OEBPS/hayat-ghayr-16.html
looping through entry: OEBPS/hayat-ghayr-17.html
looping through entry: OEBPS/hayat-ghayr-18.html
looping through entry: OEBPS/hayat-ghayr-19.html
looping through entry: OEBPS/hayat-ghayr-20.html
looping through entry: OEBPS/hayat-ghayr-21.html
looping through entry: OEBPS/hayat-ghayr-22.html
looping through entry: META-INF/container.xml
looping through entry: OEBPS/images/277.png
looping through entry: OEBPS/toc.ncx
going through data with entry: OEBPS/toc.ncx, contentLength: 5549
returning data
:::::::::::::::::::::::::::::::
getInputStream: /24748681/OEBPS/hayat-ghayr.html
:::::::::::::::::::::::::::::::
looping through entry: mimetype
looping through entry: OEBPS/hayat-ghayr.html
going through data with entry: OEBPS/hayat-ghayr.html, contentLength: -1
returning data
【问题讨论】：
-
它是
ord('-')ord('.')，所以你认为它是zip文件中的最后一个，而不是第一个吗？ -
@tynn 这绝对是第一个，基于手动探索 epub 文件的内容.. 但是这有什么区别呢？
-
想知道您是如何使用
dataWithHexString，什么库/框架？ -
您发布的代码有些奇怪。在您的台式机上，您使用
aes-192-cbc和一个单独的 IV 进行解密。在 Android 上，您使用的是AES/ECB/PKCS5Padding，而在 iOS 上，它看起来像带有 ECB 和 PKCS7Padding 的 AES。 CBC 和 ECB 完全不兼容，因此肯定有问题...... -
@Robert 你的意思是在 android 上我使用的是 CBC 对吗？
c = Cipher.getInstance("AES/CBC/PKCS7Padding","BC");
标签： java android encryption epub skyepub