/**
* @brief CBC Encrypt data stream with null padding at the end.
*
* This function preforms CBC Encryption in the actual mode with actual key
* and portions of AES_BLOCKSIZE length.
* If the last block has less than AES_BLOCKSIZE bytes, it is padded with
* null bytes to this length and then encrypted.
*
* No result is return; the CBC-MAC must be read separately.
*
* @param start Pointer to start address
* @param buflen Number of bytes to be encrypted; if 0, nothing happens
*/
void encrypt_with_padding(uint8_t *start, uint8_t buflen)
{
/* Encrypt the "full blocks". */
while (buflen >= AES_BLOCKSIZE) {
#if (SAL_TYPE == AT86RF2xx)
sal_aes_wrrd(start, NULL);
#else
sal_aes_exec(start);
#endif
start += AES_BLOCKSIZE;
buflen -= AES_BLOCKSIZE;
}
/* Pad the possible rest and encrypt it. */
if (buflen) {
uint8_t locbuf[AES_BLOCKSIZE];
memcpy(locbuf, start, buflen);
memset(locbuf + buflen, 0, AES_BLOCKSIZE - buflen);
#if (SAL_TYPE == AT86RF2xx)
sal_aes_wrrd(locbuf, NULL);
#else
sal_aes_exec(locbuf);
#endif
}
}
/**
* \brief AES-ECB block encryption/decryption
*
* \param ctx AES context
* \param mode MBEDTLS_AES_ENCRYPT or MBEDTLS_AES_DECRYPT
* \param input 16-byte input block
* \param output 16-byte output block
*
* \return 0 if successful
*/
int mbedtls_aes_crypt_ecb(mbedtls_aes_context *ctx, int mode, const unsigned char input[16], unsigned char output[16])
{
int retval = 0;
sal_aes_wrrd((uint8_t *)input, NULL);
sal_aes_read((uint8_t *)output);
return retval;
}
/**
* @brief Computes MIC
*
* This function computes the MIC according to CCM.
*
* The key was initialized in other functions before.
*
* @param[in] buffer Input data (frame, not padded yet)
* @param[out] mic Computed MIC of size AES_BLOCKSIZE
* @param[in] nonce The nonce: Initialization Vector (IV) as used in
* cryptography; the ZigBee nonce are the bytes 2...14
* of this nonce
* @param[in] hdr_len Size of plain text header in bytes (may be 0)
* @param[in] pld_len Length of payload in bytes (may be 0)
*/
void compute_mic(uint8_t *buffer,
uint8_t *mic,
uint8_t *nonce,
uint8_t hdr_len,
uint8_t pld_len)
{
sal_aes_setup(NULL, AES_MODE_ECB, AES_DIR_ENCRYPT);
#if (SAL_TYPE == AT86RF2xx)
sal_aes_wrrd(nonce, NULL);
#else
sal_aes_exec(nonce);
#endif
sal_aes_setup(NULL, AES_MODE_CBC, AES_DIR_ENCRYPT);
if (hdr_len) {
uint8_t locbuf[AES_BLOCKSIZE];
uint8_t firstlen;
firstlen = MIN(AES_BLOCKSIZE - 2, hdr_len);
/* Prepend L(a). */
locbuf[0] = 0;
locbuf[1] = hdr_len;
memcpy(locbuf + 2, buffer, firstlen);
encrypt_with_padding(locbuf, firstlen + 2);
if (firstlen < hdr_len) {
/* No padding up to now since firstlen is AES_BLOCKSIZE
*- 2. */
encrypt_with_padding(buffer + firstlen,
hdr_len - firstlen);
}
}
encrypt_with_padding(buffer + hdr_len, pld_len);
sal_aes_read(mic);
}
/**
* @brief Encrypts and decrypts payload and MIC
*
* This function perform encryption and decryption of the payload and the MIC.
*
* @param[in] buffer Input data (frame, not padded yet)
* @param[in] nonce The nonce
* @param[in] mic_len Size of MIC in bytes (may be 0)
* @param[in] pld_len Length of payload in bytes (may be 0)
*/
void encrypt_pldmic(uint8_t *buffer,
uint8_t *nonce,
uint8_t mic_len,
uint8_t pld_len)
{
uint8_t ctr;
uint8_t i;
uint8_t keystream[AES_BLOCKSIZE];
uint8_t *keystreamptr;
sal_aes_setup(NULL, AES_MODE_ECB, AES_DIR_ENCRYPT);
/* Init first keystream block. */
nonce[AES_BLOCKSIZE - 1] = ctr = 1;
if (pld_len > 0) {
sal_aes_wrrd(nonce, NULL);
}
while (true) {
/* Compute next keystream block and get the previous one. */
if (pld_len <= AES_BLOCKSIZE) { /* Last block */
if (mic_len) {
/* Prepare the keystream for MIC. */
nonce[AES_BLOCKSIZE - 1] = 0;
sal_aes_wrrd(nonce, keystream);
} else {
sal_aes_read(keystream);
}
} else {
/* Prepare the next keystream block. */
nonce[AES_BLOCKSIZE - 1] = ++ctr;
sal_aes_wrrd(nonce, keystream);
}
/* En/decrypt payload. */
for (i = MIN(pld_len, AES_BLOCKSIZE), keystreamptr = keystream;
i--;
/* */) {
*buffer++ ^= *keystreamptr++;
}
if (pld_len <= AES_BLOCKSIZE) {
break;
}
pld_len -= AES_BLOCKSIZE;
}
/* En/decrypt MIC. */
if (mic_len) {
sal_aes_read(keystream);
for (i = mic_len, keystreamptr = keystream; i--; /* */) {
*buffer++ ^= *keystreamptr++;
}
}
}
