Develop Reference

Android Decryption WRONG_FINAL_BLOCK_LENGTH (File Encrypted with Python)

I am trying to get File Decryption working in Android. The file i have has been encrypted from python using Crypto.Cipher AES: full code:
import os, binascii, struct
from Crypto.Cipher import AES
def encrypt_file():
chunksize=64*1024
iv = "96889af65c391c69"
k1 = "cb3a44cf3cb120cc7b8b3ab777f2d912"
file = "tick.png"
out_filename = "entick.png"
dir = os.path.dirname(__file__)+"\\"
print(iv)
encryptor = AES.new(key, AES.MODE_CBC, iv)
in_filename = dir+file
filesize = os.path.getsize(in_filename)
with open(in_filename, 'rb') as infile:
with open(out_filename, 'wb') as outfile:
outfile.write(struct.pack('<Q', filesize))
outfile.write(iv)
while True:
chunk = infile.read(chunksize)
if len(chunk) == 0:
break
elif len(chunk) % 16 != 0:
chunk += ' ' * (16 - len(chunk) % 16)
outfile.write(encryptor.encrypt(chunk))
if __name__ == "__main__":
encrypt_file()
Android Decryption function (main):
private static File main(String fname, File enfile, String IV, String key) {
try {
byte[] bkey = key.getBytes("UTF-8");
byte[] bIV = IV.getBytes("UTF-8");
Log.d("ByteLen","bkey:"+Integer.toString(bkey.length));
Log.d("ByteLen","bIV:"+ Integer.toString(bIV.length));
File aesFile;
aesFile = enfile;
Log.d("AESFILELENGTH", "aes length: " + aesFile.length());
File aesFileBis = new File(String.valueOf(Environment.getExternalStorageDirectory().toPath()), "tick.png"); //to be replaced with fname
FileInputStream fis;
FileOutputStream fos;
CipherInputStream cis;
SecretKeySpec secretKey = new SecretKeySpec(bkey, "AES");
Cipher decrypt = Cipher.getInstance("AES/CBC/PKCS5Padding");
IvParameterSpec ivSpec = new IvParameterSpec(bIV);
decrypt.init(Cipher.DECRYPT_MODE, secretKey, ivSpec);
fis = new FileInputStream(aesFile);
cis = new CipherInputStream(fis, decrypt);
fos = new FileOutputStream(aesFileBis);
try {
byte[] mByte = new byte[8];
int i = cis.read(mByte);
Log.i("MBYTE", "mbyte i: " + i);
while (i != -1) {
fos.write(mByte, 0, i);
i = cis.read(mByte);
}
} catch (IOException e) {
e.printStackTrace();
}
fos.flush();
fos.close();
cis.close();
fis.close();
return aesFileBis;
} catch (Exception e) {
e.printStackTrace();
}
return null;
}
The Crypto.Cipher module inserts the IV into the file as bytes 8-24 so i created this method to extract them:
private String IV(File enfile) throws UnsupportedEncodingException, FileNotFoundException {
int size = 24;
byte bytes[] = new byte[size];
byte tmpBuff[] = new byte[size];
if(enfile.canRead()){
//run decryption code
FileInputStream fis= new FileInputStream(enfile);
try {
int read = fis.read(bytes, 0, size);
if (read < size) {
int remain = size - read;
while (remain > 0) {
read = fis.read(tmpBuff, 0, remain);
System.arraycopy(tmpBuff, 0, bytes, size - remain, read);
remain -= read;
}
}
} catch (FileNotFoundException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}
}
String IV = new String(bytes, "US-ASCII");
IV = IV.substring(8,24);
return IV;
}
From the Decrypt function i have checked and verified the key is 32 bytes long and the iv is 16 bytes long and both are the correct IV and Key. I know I am switching from a byte array to string and back again but that's just for testing.
I have looked at a few posts regarding this issue and so far have only found posts relating to the key being the wrong byte size or for decrpyting Strings and not files and therefor switching base64 encoding doesn't seem to apply. I think the issue is to do with the way Crypto.Cipher is padding the files as the first 8 byes look like junk (SO and NULL bytes) then there are 16 bytes of IV.

Thanks to the comment i added the Padding module from crypto: https://github.com/dlitz/pycrypto/blob/master/lib/Crypto/Util/Padding.py
im my python code i added:
from Crypto.Util.py3compat import * #solves bchr error
i also copied the pad() function from the Padding.py to the end of my code.
in the file writing function:
with open(in_filename, 'rb') as infile:
with open(out_filename, 'wb') as outfile:
outfile.write(iv) ##IV becomes the first 16 bytes, not using struct.pack() anymore
while True:
chunk = infile.read(chunksize)
if len(chunk) == 0:
break
elif len(chunk) % 16 != 0:
chunk += ' ' * (16 - len(chunk) % 16)
outfile.write(encryptor.encrypt(pad(chunk, 16))) ##added padding here
Finally in the Java code i removed the IV finder function and updated the main function:
private static File main(String fname, File enfile, String key) {
try {
FileInputStream fis;
File aesFile;
aesFile = enfile;
byte[] bkey = key.getBytes("UTF-8");
fis = new FileInputStream(aesFile);
byte[] IV = new byte[16];
for(Integer i =0; i < 16; i++){
IV[i] = (byte) fis.read();
}
Log.e("IV:",""+new String(IV, "US-ASCII"));
Log.d("ByteLen","bkey:"+Integer.toString(bkey.length));
Log.d("ByteLen","bIV:"+ Integer.toString(IV.length));
aesFile = enfile;
Log.d("AESFILELENGTH", "aes length: " + aesFile.length());
File aesFileBis = new File(String.valueOf(Environment.getExternalStorageDirectory().toPath()), "file.png"); //to be replaced with fname
FileOutputStream fos;
CipherInputStream cis;
SecretKeySpec secretKey = new SecretKeySpec(bkey, "AES");
Cipher decrypt = Cipher.getInstance("AES/CBC/PKCS5Padding");
IvParameterSpec ivSpec = new IvParameterSpec(IV);
decrypt.init(Cipher.DECRYPT_MODE, secretKey, ivSpec);
cis = new CipherInputStream(fis, decrypt);
fos = new FileOutputStream(aesFileBis);
try {
byte[] mByte = new byte[8];
int i = cis.read(mByte);
Log.i("MBYTE", "mbyte i: " + i);
while (i != -1) {
fos.write(mByte, 0, i);
i = cis.read(mByte);
}
} catch (IOException e) { e.printStackTrace();}
fos.flush();
fos.close();
cis.close();
fis.close();
return aesFileBis;
}catch(Exception e) {e.printStackTrace(); }
return null;
}
The new parts of the code take the first 16 bytes from the FileInputStream and puts them into a byte array to be used as the IV, the rest are then decrypted using CBC/PKCS5Padding.
Hope this answer can be useful for anyone else.

Android Encrypt video file with Facebook conceal library

I want to encrypt video files stored in SD card
Environment.getExternalStorageDirectory()
I have found that Facebook conceal is good for encrypting large files. I have followed this tutorial Make fast cryptographic operations on Android with Conceal
Here is what i have done up to now.
Encryption method
public void encodeAndSaveFile(File videoFile, String path) {
try {
final byte[] encrypt = new byte[(int) videoFile.length()];
ContextWrapper cw = new ContextWrapper(getApplicationContext());
File directory = cw.getDir(path, Context.MODE_PRIVATE);
File mypath = new File(directory, "en1");
Crypto crypto = new Crypto(new SharedPrefsBackedKeyChain(this), new SystemNativeCryptoLibrary());
if (!crypto.isAvailable()) {
return;
}
OutputStream fileStream = new BufferedOutputStream(
new FileOutputStream(mypath));
OutputStream outputStream = crypto.getCipherOutputStream(
fileStream, new Entity("Passwordd"));
outputStream.write(encrypt);
outputStream.close();
} catch (UnsupportedOperationException e) {
e.printStackTrace();
} catch (FileNotFoundException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
} catch (Exception e) {
e.printStackTrace();
}
Toast.makeText(WebViewActivity.this,"Encrypted",Toast.LENGTH_LONG).show();
}
Decryption method
private void decodeFile(String filename,String path) {
Crypto crypto = new Crypto(new SharedPrefsBackedKeyChain(this),
new SystemNativeCryptoLibrary());
ContextWrapper cw = new ContextWrapper(getApplicationContext());
File directory = cw.getDir(path, Context.MODE_PRIVATE);
File file = new File(directory, filename);
try {
FileInputStream fileStream = new FileInputStream(file);
InputStream inputStream = crypto.getCipherInputStream(fileStream,
new Entity("Password"));
ByteArrayOutputStream out = new ByteArrayOutputStream();
int read;
byte[] buffer = new byte[1024];
while ((read = inputStream.read(buffer)) != -1) {
out.write(buffer, 0, read);
}
inputStream.close();
} catch (Exception e) {
e.printStackTrace();
}
Toast.makeText(WebViewActivity.this,"Decrypted",Toast.LENGTH_LONG).show();
}
But this code throwing following error at the run time
java.lang.illegalArgumentException: File contains a path separator
Then i have changed "mypath: variable of encodeAndSaveFile to this
File mypath = new File(directory, "en1");
and "file" variable of decodeFile to this
File file = new File(directory, filename);
Then no errors but. Encryption is not happening. Please help to solve this or suggest correct method for video encryption with conceal lib.

Android - Sending file over bluetooth

I'm developing an Android application sending files from one device to another.
Establishing the connection between both devices works perfectly, but there is something going wrong while transferring the file.
On the receiving device, the file gets created but unfortunately it's empty.
This is my code for handling the incoming file:
try {
byte[] buffer = new byte[1024];
int bytes = 0;
boolean eof = false;
File file = new File(Environment.getExternalStoragePublicDirectory(
Environment.DIRECTORY_PICTURES), "test.jpg");
OutputStream os = null;
try {
os = new BufferedOutputStream(new FileOutputStream(file));
} catch (FileNotFoundException e) {
e.printStackTrace();
}
while (!eof) {
bytes = mmInStream.read(buffer);
int offset = bytes - 11;
byte[] eofByte = new byte[11];
eofByte = Arrays.copyOfRange(buffer, offset, bytes);
String message = new String(eofByte, 0, 11);
if(message.equals("end of file")) {
os.flush();
os.close();
eof = true;
} else {
os.write (buffer);
}
}
} catch (IOException e) {
e.printStackTrace();
}

Using the DataInputStream/DataOuputStream solved the problem.

Android: Accessing File from Internal Storage Using RandomAccessFile

I am creating an app that needs to read data from a file. I was initially reading it from the assets folder using a BufferedReader and an InputStreamReader but I was running into memory issues (see Android: File Reading - OutOfMemory Issue). One suggestion was to copy the data from the assets folder to the internal storage (not the SD card) and then access it via RandomAccessFile. So I looked up how to copy files from the assets to internal storage and I found 2 sources:
https://groups.google.com/forum/?fromgroups=#!topic/android-developers/RpXiMYV48Ww
http://developergoodies.blogspot.com/2012/11/copy-android-asset-to-internal-storage.html
I decided to use the code from the second one and modified it for my file. So it looks like this:
public void copyFile() {
//Open your file in assets
Context context = getApplicationContext();
String destinationFile = context.getFilesDir().getPath() + File.separator + "text.txt";
if (!new File(destinationFile).exists()) {
try {
copyFromAssetsToStorage(context, "text.txt", destinationFile);
} catch (IOException e) {
e.printStackTrace();
}
}
}
private void copyStream(InputStream input, OutputStream output) throws IOException {
byte[] buffer = new byte[1024];
int length = Input.read(buffer);
while (length > 0) {
output.write(buffer, 0, length);
length = input.read(buffer);
}
}
private void copyFromAssetsToStorage(Context context, String sourceFile, String destinationFile) throws IOException {
InputStream inputStream = context.getAssets().open(sourceFile);
OutputStream outputStream = new FileOutputStream(destinationFile);
copyStream(inputStream , outputStream );
outputStream.flush();
outputStream.close();
inputStream.close();
}
I am assuming that this copies the file into the app's data directory. I have not been able to test it because I would like to be able to access the file using RandomAccessFile. However, I have never done either one of these two (copying the file from assets and RandomAccessFile) so I am stuck. The work on this app has come to a standstill because this is the only thing that is preventing me from completing it.
Can anyone provide me with corrections, suggestions, and correct implementations of how to access the data using RandomAccessFile? (The data is a list of strings 4-15 characters in length on each line.)
EDIT*
private File createCacheFile(Context context, String filename){
File cacheFile = new File(context.getCacheDir(), filename);
if (cacheFile.exists()) {
return cacheFile ;
}
InputStream inputStream = null;
FileOutputStream fileOutputStream = null;
try {
inputStream = context.getAssets().open(filename);
fileOutputStream = new FileOutputStream(cacheFile);
int bufferSize = 1024;
byte[] buffer = new byte[bufferSize];
int length = -1;
while ( (length = inputStream.read(buffer)) > 0) {
fileOutputStream.write(buffer,0,length);
}
} catch (FileNotFoundException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
finally {
try {
fileOutputStream.close();
} catch (IOException e) {
e.printStackTrace();
}
try {
inputStream.close();
} catch (IOException e) {
e.printStackTrace();
}
}
return cacheFile;
}

1- Copy the file from assets to the cache directory
This code just for illustration, you have to do appropriate exception handling and close resources
private File createCacheFile(Context context, String filename){
File cacheFile = new File(context.getCacheDir(), filename);
if (cacheFile.exists()) {
return cacheFile ;
}
InputStream inputStream = context.getAssets().open(filename);
FileOutputStream fileOutputStream = new FileOutputStream(cacheFile);
int bufferSize = 1024;
byte[] buffer = new byte[bufferSize];
int length = -1;
while ( (length = inputStream.read(buffer)) > 0) {
fileOutputStream.write(buffer,0,length);
}
fileOutputStream.close();
inputStream.close();
return cacheFile;
}
2- Open the file using RandomAccessFile
File cacheFile = createCacheFile(context, "text.txt");
RandomAccessFile randomAccessFile = new RandomAccessFile(cacheFile, "r");
// Process the file
randomAccessFile.close();
On a side note, you should follow Java naming conventions, e.g. your method and variable name should start with small letter such as copyFromAssetsToStorage and destinationFile
Edit:
You should make a separate try/catch for each close() operation, so if one fails the other still get executed and check that they are not null
finally {
try {
if(fileOutputStream!=null){
fileOutputStream.close();
}
} catch (IOException e) {
e.printStackTrace();
}
try {
if(inputStream!=null){
inputStream.close();
}
} catch (IOException e) {
e.printStackTrace();
}
}

Diffrent signatures for a file based on freshly createted vs. longer persistence

Context
I am copying a sqlite db file out of the assets to internal storage.
The file opens fine, but I wanted a additional layer of safety. There is
a slim possibility that when the file gets copied out it doesn't complete.
I decided to favor a check sum technique: specifically the MessageDigest
Java thing. so here's the code:
public ZipCode(Context ctx) {
this.ctx = ctx;
if (!databaseExist(ctx)) {
Log.d("ZipCode", "DB DNE");
inflate_db(ctx);
check_DB(ctx);
} else {
Log.d("ZipCode", "DB Exsits");
check_DB(ctx);
}
}
private static void inflate_db(Context ctx) {
byte[] buffer = new byte[2048];
int length;
AssetManager am = ctx.getAssets();
try {
BufferedInputStream is = new BufferedInputStream(
am.open(ZIPCODE_SQLITE_FAUX_FILE));
GZIPInputStream zis = new GZIPInputStream(is);
File dbfile = ctx.getDatabasePath(ZIPCODE_SQLITE);
FileOutputStream out = new FileOutputStream(dbfile);
while ((length = zis.read(buffer, 0, buffer.length)) > 0) {
out.write(buffer, 0, length);
}
out.flush();
out.close();
zis.close();
} catch (IOException e) {
e.printStackTrace();
Log.d("ERROR", e.getMessage());
}
}
private static void check_DB(Context ctx) {
File dbfile = ctx.getDatabasePath(ZIPCODE_SQLITE);
FileInputStream fis;
MessageDigest digester;
byte[] bytes = new byte[8192];
int byteCount;
try {
digester = MessageDigest.getInstance("MD5");
fis = new FileInputStream(dbfile);
while ((byteCount = fis.read(bytes)) > 0) {
digester.update(bytes, 0, byteCount);
}
String digest = Base64.encodeBytes(digester.digest());
Log.d("MD5 Sum", digest);
fis.close();
return;
} catch (FileNotFoundException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}
catch (NoSuchAlgorithmException e1) {
e1.printStackTrace();
}
}
Now for the Question
Why is it that on fresh creation the check_DB's Log.d("MD5 Sum", digest);
has one output and say on relaunch (i.e. the DB file exists in internal storage)
the check_DB's Log.d("MD5 Sum", digest); has a different output.
Note:
databaseExist(ctx) checks for the DB file's existence per Android conventions.
private static boolean databaseExist(Context ctx) {
File dbFile = ctx.getDatabasePath(ZIPCODE_SQLITE);
return dbFile.exists();
}

why don't you calculate MD5 of your asset file (in your project directory) to find out which MD5 is right and which is wrong? then it'll be easier to find the problem part.
also, i'd suggest to replace (byteCount = fis.read(bytes)) > 0 with (byteCount = fis.read(bytes)) != -1 according to the FileInputStream reference manual.