I am trying to do aes encryption/decryption in native code C. Encryption does work but when I try to decrypt the string. It doesn't end up as original string. Here is the JNI method which does encrypt/decrpt based on mode param:
jbyteArray Java_com_example_hellojni_HelloJni_encrypt( JNIEnv* env,
jobject this,
jbyteArray srcData,
jint mode)
{
// get length of bytes
int srcLen=(*env)->GetArrayLength(env,srcData);
//convert jbyteArray to byte []
jbyte data[srcLen];
(*env)->GetByteArrayRegion(env, srcData, 0, srcLen, data);
(*env)->ReleaseByteArrayElements(env, srcData,data , 0);
unsigned char* indata=(unsigned char*)data;
const unsigned char ukey[] = { 'H','A','R','D','C','O','D','E','D',' ','K','E','Y','1','2','3'};
unsigned char *outdata = NULL;
outdata = malloc(srcLen);
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, srcLen);
jboolean isCopy;
void *decrypteddata = (*env)->GetPrimitiveArrayCritical(env, (jarray)bArray, &isCopy);
memcpy(decrypteddata, outdata, srcLen);
(*env)->ReleasePrimitiveArrayCritical(env, bArray, decrypteddata, 0);
return bArray;
}
Any ideas why decrypting the encrypted bytes are not the same as the original?
As suggested by Codo and owlstead I tried higher level implementation which still has the same issue.
Here is the code from saju.net.in/code/misc/openssl_aes.c.txt
/**
* Create an 256 bit key and IV using the supplied key_data. salt can be added for taste.
* Fills in the encryption and decryption ctx objects and returns 0 on success
**/
int aes_init(unsigned char *key_data, int key_data_len, unsigned char *salt, EVP_CIPHER_CTX *e_ctx,
EVP_CIPHER_CTX *d_ctx)
{
int i, nrounds = 5;
unsigned char key[32], iv[32];
/*
* Gen key & IV for AES 256 CBC mode. A SHA1 digest is used to hash the supplied key material.
* nrounds is the number of times the we hash the material. More rounds are more secure but
* slower.
*/
i = EVP_BytesToKey(EVP_aes_256_cbc(), EVP_sha1(), salt, key_data, key_data_len, nrounds, key, iv);
if (i != 32) {
printf("Key size is %d bits - should be 256 bits\n", i);
return -1;
}
EVP_CIPHER_CTX_init(e_ctx);
EVP_EncryptInit_ex(e_ctx, EVP_aes_256_cbc(), NULL, key, iv);
EVP_CIPHER_CTX_init(d_ctx);
EVP_DecryptInit_ex(d_ctx, EVP_aes_256_cbc(), NULL, key, iv);
return 0;
}
/*
* Encrypt *len bytes of data
* All data going in & out is considered binary (unsigned char[])
*/
unsigned char *aes_encrypt(EVP_CIPHER_CTX *e, unsigned char *plaintext, int *len)
{
/* max ciphertext len for a n bytes of plaintext is n + AES_BLOCK_SIZE -1 bytes */
int c_len = *len + AES_BLOCK_SIZE, f_len = 0;
unsigned char *ciphertext = malloc(c_len);
/* allows reusing of 'e' for multiple encryption cycles */
EVP_EncryptInit_ex(e, NULL, NULL, NULL, NULL);
/* update ciphertext, c_len is filled with the length of ciphertext generated,
*len is the size of plaintext in bytes */
EVP_EncryptUpdate(e, ciphertext, &c_len, plaintext, *len);
/* update ciphertext with the final remaining bytes */
EVP_EncryptFinal_ex(e, ciphertext+c_len, &f_len);
*len = c_len + f_len;
return ciphertext;
}
/*
* Decrypt *len bytes of ciphertext
*/
unsigned char *aes_decrypt(EVP_CIPHER_CTX *e, const unsigned char *ciphertext, int *len)
{
/* because we have padding ON, we must allocate an extra cipher block size of memory */
int p_len = *len, f_len = 0;
unsigned char *plaintext = malloc(p_len + AES_BLOCK_SIZE);
EVP_DecryptInit_ex(e, NULL, NULL, NULL, NULL);
EVP_DecryptUpdate(e, plaintext, &p_len, ciphertext, *len);
EVP_DecryptFinal_ex(e, plaintext+p_len, &f_len);
*len = p_len + f_len;
return plaintext;
}
here are my methods that are called form java:
/* "opaque" encryption, decryption ctx structures that libcrypto uses to record
status of enc/dec operations */
EVP_CIPHER_CTX en, de;
jint
Java_com_example_hellojni_HelloJni_aesinit( JNIEnv* env,
jobject obj)
{
unsigned int salt[] = {12345, 54321};
unsigned char key_data[]={ 'G','X','8','j','E','r','0','4','o','6','P','C','+','I','E','+'};
int key_data_len;
key_data_len = strlen(key_data);
/* gen key and iv. init the cipher ctx object */
if (aes_init(key_data, key_data_len, (unsigned char *)&salt, &en, &de)) {
printf("Couldn't initialize AES cipher\n");
__android_log_print(ANDROID_LOG_VERBOSE, APPNAME, "initializing aes failed");
return 0;
}
__android_log_print(ANDROID_LOG_VERBOSE, APPNAME, "initializing aes success");
return 1;
}
jint
Java_com_example_hellojni_HelloJni_aesCleanup( JNIEnv* env,
jobject obj)
{
EVP_CIPHER_CTX_cleanup(&en);
EVP_CIPHER_CTX_cleanup(&de);
return 1;
}
jbyteArray
Java_com_example_hellojni_HelloJni_encrypt( JNIEnv* env,
jobject obj, jstring textToEncrypt)
{
const char *plainText = (*env)->GetStringUTFChars(env, textToEncrypt, 0);
int len = strlen(plainText)+1;
unsigned char *ciphertext = aes_encrypt(&en, (unsigned char *)plainText, &len);
jbyteArray byteArray=(*env)->NewByteArray(env, strlen(ciphertext));
(*env)->SetByteArrayRegion(env, byteArray, 0, strlen(ciphertext), (const jbyte*)ciphertext);
(*env)->ReleaseStringUTFChars(env, textToEncrypt, plainText);
return byteArray;
}
jbyteArray
Java_com_example_hellojni_HelloJni_decrypt( JNIEnv* env,
jobject obj, jstring textToDecrypt)
{
const unsigned char *cipherText = (*env)->GetStringUTFChars(env, textToDecrypt, NULL);
int len = strlen(cipherText)+1;
char *plainText = (char *)aes_decrypt(&de, cipherText, &len);
jbyteArray byteArray=(*env)->NewByteArray(env, strlen(plainText));
(*env)->SetByteArrayRegion(env, byteArray, 0, strlen(plainText), (const jbyte*)plainText);
(*env)->ReleaseStringUTFChars(env, textToDecrypt, cipherText);
return byteArray;
}
