//key:128
//encrypt output:nonce(12)+tag(16)+cipher_text
//no aad
//
int Encrypt_AesGcm128(const uint8_t * plain_text, uint32_t plain_text_len,
const SecureString & key, string & cipher_text){
cipher_text.clear();
EVP_CIPHER_CTX ctx;
EVP_CIPHER_CTX_init(&ctx);
EVP_CIPHER * cipher=EVP_aes_128_gcm();
if(1 != EVP_EncryptInit_ex(&ctx, cipher, NULL, NULL, NULL))
return LIB_ERR;
unsigned char nonce[GCM_NONCE_LENGTH]={};
RAND_bytes(nonce,4);
struct timeval t={0,0};
if(0==gettimeofday(&t,NULL)){
memcpy(&nonce[4],&t.tv_sec,4);
memcpy(&nonce[8],&t.tv_nsec,4);
}else{
RAND_bytes(&nonce[4],GCM_NONCE_LENGTH-4);
}
if(1 != EVP_CIPHER_CTX_ctrl(&ctx, EVP_CTRL_GCM_SET_IVLEN, GCM_NONCE_LENGTH, NULL))
return LIB_ERR;
if(1 != EVP_EncryptInit_ex(&ctx, NULL, NULL, key.data(), &nonce[0]))
return LIB_ERR;
cipher_text.reserve(GCM_NONCE_LENGTH+GCM_TAG_LENGTH+plain_text_len);
cipher_text.append(&nonce[0],GCM_NONCE_LENGTH);
cipher_text.append(GCM_TAG_LENGTH,0);//fill tag later
cipher_text.resize(GCM_NONCE_LENGTH+GCM_TAG_LENGTH+plain_text_len);
//do the real encryption.
int out_len=plain_text_len;
const int ret = EVP_CipherUpdate(&ctx,&cipher_text[GCM_NONCE_LENGTH+GCM_TAG_LENGTH],&out_len, plain_text,plain_text_len);
if(1!=ret){
cipher_text.clear();
return LIB_ERR;
}
out_len=0;
if(1 != EVP_CipherFinal_ex(&ctx,cipher_text.end(),out_len) ){
cipher_text.clear();
return LIB_ERR;
}
/* Get the tag */
if(1 != EVP_CIPHER_CTX_ctrl(ctx, EVP_CTRL_GCM_GET_TAG, 16, &cipher_text[GCM_NONCE_LENGTH])){
cipher_text.clear();
return LIB_ERR;
}
return OK;
}
int Decrypt_AesGcm128(const uint8_t * cipher_text, uint32_t cipher_text_len,
const SecureString & key, string & plain_text){
EVP_CIPHER_CTX ctx;
EVP_CIPHER_CTX_init(&ctx);
EVP_CIPHER * cipher=EVP_aes_128_gcm();
if(1 != EVP_DecryptInit_ex(&ctx, cipher, NULL, NULL, NULL))
return false;
if(1 != EVP_CIPHER_CTX_ctrl(&ctx, EVP_CTRL_GCM_SET_IVLEN, GCM_NONCE_LENGTH, NULL))
return false;
unsigned char nonce[GCM_NONCE_LENGTH]={};
if(1 != EVP_EncryptInit_ex(&ctx, NULL, NULL, key.data(), cipher_text))
return false;
int outl=out.size();
const int ret = EVP_CipherUpdate(&ctx,&out[0],outl,&in[0],in.size());
if(1==ret){
out.resize(outl);
return true;
}
out.resize(EVP_CIPHER_CTX_block_size(&ctx));
/* Set expected tag value. Works in OpenSSL 1.0.1d and later */
if(!EVP_CIPHER_CTX_ctrl(ctx, EVP_CTRL_GCM_SET_TAG, 16, tag))
return false;
if(1 != EVP_CipherFinal_ex(&ctx,out.data(),outl) ){
return false;
}
out.resize(outl);
return OK;
}
