ssh_hmac_sha256.cpp File Reference

HMAC-SHA2-256 implementation (RFC 2104). More...

#include "network_drivers/presentation/ssh/crypto/ssh_hmac_sha256.h"
#include <string.h>

Go to the source code of this file.

Functions
void	ssh_hmac_sha256_init (SshHmacCtx *ctx, const uint8_t *key, size_t key_len)
	Initialize a streaming HMAC-SHA2-256 context.
void	ssh_hmac_sha256_update (SshHmacCtx *ctx, const uint8_t *data, size_t len)
	Feed len bytes into the running HMAC.
void	ssh_hmac_sha256_final (SshHmacCtx *ctx, uint8_t mac[SSH_HMAC_SHA256_LEN])
	Finalize and write the 32-byte MAC.
void	ssh_hmac_sha256 (const uint8_t *key, size_t key_len, const uint8_t *data, size_t len, uint8_t mac[SSH_HMAC_SHA256_LEN])
	Compute HMAC-SHA2-256 over a single contiguous buffer.

Detailed Description

HMAC-SHA2-256 implementation (RFC 2104).

Implemented in terms of ssh_sha256 streaming functions so it compiles identically on Arduino and native. The inner SHA-256 hardware acceleration (where present) is transparent through the ssh_sha256_* calls.

RFC 2104 construction: HMAC(K, m) = H((K XOR opad) || H((K XOR ipad) || m))

where ipad = 0x36 repeated, opad = 0x5c repeated, H = SHA-256.

Since SSH-derived MAC keys are exactly 32 bytes (< SHA-256 block size of 64 bytes), the key is NOT pre-hashed - it is padded with zeros to 64 bytes internally and used directly as the HMAC key.

Definition in file ssh_hmac_sha256.cpp.

Function Documentation

ssh_hmac_sha256_init()

void ssh_hmac_sha256_init	(	SshHmacCtx *	ctx,
		const uint8_t *	key,
		size_t	key_len
	)

Initialize a streaming HMAC-SHA2-256 context.

Parameters

ctx	Context to initialize.
key	Key bytes (≤ 64; keys > 64 are pre-hashed per RFC 2104).
key_len	Length of key in bytes.

Definition at line 53 of file ssh_hmac_sha256.cpp.

References SshHmacCtx::inner, SshHmacCtx::okey, ssh_sha256_init(), and ssh_sha256_update().

Referenced by ssh_hmac_sha256().

ssh_hmac_sha256_update()

void ssh_hmac_sha256_update	(	SshHmacCtx *	ctx,
		const uint8_t *	data,
		size_t	len
	)

Feed len bytes into the running HMAC.

Definition at line 63 of file ssh_hmac_sha256.cpp.

References SshHmacCtx::inner, and ssh_sha256_update().

Referenced by ssh_hmac_sha256().

ssh_hmac_sha256_final()

void ssh_hmac_sha256_final	(	SshHmacCtx *	ctx,
		uint8_t	mac[SSH_HMAC_SHA256_LEN]
	)

Finalize and write the 32-byte MAC.

Definition at line 68 of file ssh_hmac_sha256.cpp.

References SshHmacCtx::inner, SshHmacCtx::okey, SSH_SHA256_DIGEST_LEN, ssh_sha256_final(), ssh_sha256_init(), and ssh_sha256_update().

Referenced by ssh_hmac_sha256().

ssh_hmac_sha256()

void ssh_hmac_sha256	(	const uint8_t *	key,
		size_t	key_len,
		const uint8_t *	data,
		size_t	len,
		uint8_t	mac[SSH_HMAC_SHA256_LEN]
	)

Compute HMAC-SHA2-256 over a single contiguous buffer.

Equivalent to calling the streaming variant with one update call.

Parameters

key	MAC key bytes.
key_len	Key length in bytes (must be ≤ 64; keys > 64 bytes are pre-hashed per RFC 2104; keys ≤ 64 bytes are zero-padded to the block length). SSH-derived keys are always 32 bytes.
data	Input bytes.
len	Input length.
mac	Output buffer, must be SSH_HMAC_SHA256_LEN bytes.

Definition at line 85 of file ssh_hmac_sha256.cpp.

References ssh_hmac_sha256_final(), ssh_hmac_sha256_init(), and ssh_hmac_sha256_update().