ssize_t kcapi_aead_decrypt(struct kcapi_handle * handle, const uint8_t * in, size_t inlen, const uint8_t * iv, uint8_t * out, size_t outlen, int access);
[in] cipher handle
[in] ciphertext data buffer
[in] length of in buffer
[in] IV to be used for cipher operation
[out] plaintext data buffer
[in] length of out buffer
[in] kernel access type (KCAPI_ACCESS_HEURISTIC - use internal heuristic for fastest kernel access; KCAPI_ACCESS_VMSPLICE use vmsplice access; KCAPI_ACCESS_SENDMSG sendmsg access)
The AEAD cipher operation requires the furnishing of the associated authentication data. In case such data is not required, it can be set to NULL and length value must be set to zero.
It is perfectly legal to use the same buffer as the plaintext and ciphertext pointers. That would mean that after the encryption operation, the ciphertext is overwritten with the plaintext.
The memory should be aligned at the page boundary using posix_memalign(sysconf(_SC_PAGESIZE)), If it is not aligned at the page boundary, the vmsplice call may not send all data to the kernel.
The IV buffer must be exactly kcapi_cipher_ivsize bytes in size.
To catch authentication errors (i.e. integrity violations) during the decryption operation, the return value of this call should be checked. If this function returns -EBADMSG, an authentication error was detected.
The kernel will only process sysconf(_SC_PAGESIZE) * ALG_MAX_PAGES at one time. Longer input data cannot be handled by the kernel.
return number of bytes decrypted upon success; a negative errno-style error code if an error occurred
Stephan Mueller <firstname.lastname@example.org>