JNI wrapper to openssl AES_ecb_encrypt not working - java-native-interface

Question

I'm doing a JNI wrapper to call AES_ecb_encrypt function from openssl.
The wrapper looks like this:
#include "aes.h"
#include <jni.h>
#include <string.h>
jbyteArray
Java_com_package_AESDecryptionFilterInputStream_encrypt( JNIEnv* env,
jobject this,
jbyte* data,
jbyte* userkey,
jint length,
jint mode)
{
const unsigned char* indata = (unsigned char*)data;
const unsigned char* ukey = (unsigned char*)userkey;
unsigned char *outdata = NULL;
outdata = malloc(length);
AES_KEY key;
memset(&key, 0, sizeof(AES_KEY));
if(mode == AES_ENCRYPT)
AES_set_encrypt_key(ukey, 128, &key);
else
AES_set_decrypt_key(ukey, 128, &key);
AES_ecb_encrypt(indata, outdata, &key, mode);
jbyteArray bArray = (*env)->NewByteArray(env, length);
jboolean isCopy;
void *decrypteddata = (*env)->GetPrimitiveArrayCritical(env, (jarray)bArray, &isCopy);
memcpy(decrypteddata, outdata, length);
(*env)->ReleasePrimitiveArrayCritical(env, bArray, decrypteddata, 0);
return bArray;
}
but, when I call it from java code to encrypt and then decrypt a string, the results aren't correct.
I'm declaring the library like this:
static {
System.loadLibrary("aes_ecb");
}
public native byte[] encrypt(byte[] data, byte[] userkey, int length, int mode);
I'm calling it like this:
byte[] dec = "0123456789012345".getBytes();
byte[] enc = encrypt(dec, decryptionKey.getBytes(), dec.length, 1);
byte[] dec2 = encrypt(enc, decryptionKey.getBytes(), enc.length, 0);
The problem is that the plain text bytes are:
dec = {49, 50, 51, 52, 53, 54, 55, 56, 57, 48, 49, 50, 51, 52, 53}
when I call encrypt:
enc = {4, 106, -41, 38, -127, 71, 33, 77, -125, 105, -57, 82, -13, 93, 44, -125}
and then when I call decrypt I get:
dec2 = {-103, 26, 73, -2, 64, -21, 14, -38, -51, 13, -7, 40, -83, 42, 119, -3}
dec and dec2 should have the same value but they don't!
What am I doing wrong?
I believe it might be something with converting signed char to unsigned char... I'm not sure about that piece of code where I cast directly jbyte* to unsigned char*...
Thank you!

Answer 1

How did you get the function signature ?
"Java_com_package_AESDecryptionFilterInputStream_encrypt( JNIEnv* env,
jobject this,
jbyte* data,
jbyte* userkey,
jint length,
jint mode)"
In JNI byte array will be passed as jbyteArray.
Function should be something like
Java_com_package_AESDecryptionFilterInputStream_encrypt( JNIEnv* env,
jobject this,
jbyteArray data,
jbyteArray userkey,
jint length,
jint mode)
You should use javah to generate the signature
You can get the length of the array passed by (*env)->GetArrayLength(env,data)
Then you have to copy into a byte* by using (*env)->GetByteArrayRegion(env, data, 0, length, nativeBytePointer);
You will probably have to allocate memory for the nativeBytePointer