aes_cmac.h File Reference

AES-128-CMAC (RFC 4493 / NIST SP800-38B) - one-shot MAC. More...

#include "protocore_config.h"

Go to the source code of this file.

Classes
struct	AesCmacNs
	Dispatch table. Addressed by offset, so the layout is asserted below. More...

Macros
#define	PROTOCORE_AES_CMAC_LEN   16
	AES-128-CMAC output length (one AES block).

Functions
	PROTOCORE_NS_LAYOUT (AesCmacNs, mac)
proto_bool	protocore_aes_cmac_mac (uint8_t *work, const uint8_t *key, const uint8_t *msg, size_t msg_len, uint8_t *out)
	Derive K1/K2, CBC-MAC the message, write the 16 bytes out.

Variables
PROTOCORE_NS AesCmacNs AesCmac	PROTOCORE_UNUSED = {.mac = protocore_aes_cmac_mac}
	Module namespace.

Detailed Description

AES-128-CMAC (RFC 4493 / NIST SP800-38B) - one-shot MAC.

The CMAC construction over the AES-128 block cipher: derive two subkeys K1/K2 from AES-128(key, 0^128), CBC-MAC the message, and XOR the final block with K1 (message a whole number of blocks) or the 10*-padded last block with K2. SMB 3.x uses it as the message-signing MAC when the negotiated signing algorithm is AES-CMAC (MS-SMB2 §3.1.4.1, dialects 3.0 / 3.0.2 / 3.1.1); it is a general primitive, not SMB-specific.

The entry below is one surface over both arms: a part with an AES peripheral encrypts a block on it, a part without runs the FIPS 197 rounds.

work is PROTOCORE_AES_CMAC_BORROW secure bytes the CALLER took, at an address it knows. It is not held past the call, so nothing here aliases it. The caller releases it, and the pool wipes on release; this module neither takes it, holds it, releases it, nor wipes it. The borrow carries the round-key schedule and both subkeys, so two MACs are two borrows and never collide.

Author

Douglas Quigg (dstroy0)

Date

2026

Definition in file aes_cmac.h.

Macro Definition Documentation

PROTOCORE_AES_CMAC_LEN

#define PROTOCORE_AES_CMAC_LEN   16

AES-128-CMAC output length (one AES block).

Definition at line 35 of file aes_cmac.h.

Function Documentation

PROTOCORE_NS_LAYOUT()

PROTOCORE_NS_LAYOUT	(	AesCmacNs	,
		mac
	)

protocore_aes_cmac_mac()

proto_bool protocore_aes_cmac_mac	(	uint8_t *	work,
		const uint8_t *	key,
		const uint8_t *	msg,
		size_t	msg_len,
		uint8_t *	out
	)

Derive K1/K2, CBC-MAC the message, write the 16 bytes out.

Parameters

work	PROTOCORE_AES_CMAC_BORROW bytes the caller took. Not held past the call.
key	the 16-byte AES-128 key
msg	the message; null iff msg_len is 0
msg_len	message length in bytes; 0 is the empty-message CMAC
out	PROTOCORE_AES_CMAC_LEN bytes

Returns

PROTO_TRUE on success.

Variable Documentation

PROTOCORE_UNUSED

PROTOCORE_NS AesCmacNs AesCmac PROTOCORE_UNUSED = {.mac = protocore_aes_cmac_mac}

Module namespace.

Definition at line 56 of file aes_cmac.h.