Datalink using Galois Embedded Crypto. More...

#include "pprzlink/pprzlink_transport.h"
#include "pprzlink/pprz_transport.h"
#include "modules/datalink/gec/gec.h"
#include "pprz_mutex.h"
#include "mcu_periph/uart.h"

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Data Structures
struct	gec_whitelist
	Whitelist for sending and receiving unencrypted messages (mostly for KEY_EXCHANGE messages) More...

struct	message_buffer
	Auxilliary message buffer for storing precomputed key exchange messages. More...

struct	gec_transport

Macros
#define	KEY_EXCHANGE_MSG_ID_UAV 239

#define	KEY_EXCHANGE_MSG_ID_GCS 159

#define	WHITELIST_LEN 20

Functions
void	gec_dl_init (void)
	Init function. More...

void	gec_dl_event (void)
	Datalink Event. More...

void	gec_transport_init (struct gec_transport *t)

void	gec_check_and_parse (struct link_device dev, struct gec_transport trans, uint8_t buf, bool msg_available)
	Parsing a frame data and copy the payload to the datalink buffer. More...

void	gec_process_sts_msg (struct link_device dev, struct gec_transport trans, uint8_t *buf)

void	respond_sts (struct link_device dev, struct gec_transport trans, uint8_t *buf)

void	finish_sts (struct link_device dev, struct gec_transport trans, uint8_t *buf)

void	gec_add_to_whitelist (struct gec_whitelist *whitelist, uint8_t id)

bool	gec_is_in_the_whitelist (struct gec_whitelist *whitelist, uint8_t id)

bool	gec_decrypt_message (uint8_t buf, volatile uint8_t payload_len)
	Attemp message decryption If a message is unencrypted, pass it through only if the MSG_ID is in the whitelist Returns Pprzlink message bytes (source_ID . More...

bool	gec_encrypt_message (uint8_t buf, uint8_t payload_len)
	Attempts message encryption Adds crypto_byte, counter and tag Returns encrypted pprzlink message (crypto_byte . More...

void	gec_process_msg1 (uint8_t *buf)
	NOTE: for RESPONDER party only Process incoming message (expected MSG1) if the right (KEY_EXCHANGE) message received with the right data (P_AE) and the right P_AE.len=PPRZ_KEY_LEN, the internal state of Sts gets updated (key derivation etc), and msg2 is prepared to be sent. More...

bool	gec_process_msg3 (uint8_t *buf)
	Process incoming message (expected MSG3) if the right (KEY_EXCHANGE) message received with the right data (SIG) and the right SIG.len=PPRZ_SIGN_LEN, and the signature is verified, Ok() is returned. More...

Variables
struct gec_transport	gec_tp
	PPRZ transport structure. More...

Detailed Description

Datalink using Galois Embedded Crypto.

Definition in file gec_dl.h.

Data Structure Documentation

struct gec_whitelist

Whitelist for sending and receiving unencrypted messages (mostly for KEY_EXCHANGE messages)

Definition at line 53 of file gec_dl.h.

Data Fields
uint8_t	idx
bool	init
uint8_t	whitelist[WHITELIST_LEN]

struct message_buffer

Auxilliary message buffer for storing precomputed key exchange messages.

Definition at line 63 of file gec_dl.h.

Data Fields
uint8_t	len
bool	message_ready
uint8_t	msg[TRANSPORT_PAYLOAD_LEN]

Macro Definition Documentation

#define KEY_EXCHANGE_MSG_ID_GCS 159

Definition at line 45 of file gec_dl.h.

Referenced by gec_transport_init().

#define KEY_EXCHANGE_MSG_ID_UAV 239

Definition at line 44 of file gec_dl.h.

Referenced by gec_transport_init().

#define WHITELIST_LEN 20

Definition at line 46 of file gec_dl.h.

Referenced by gec_add_to_whitelist().

Function Documentation

void finish_sts	(	struct link_device *	dev,
		struct gec_transport *	trans,
		uint8_t *	buf
	)

void gec_add_to_whitelist	(	struct gec_whitelist *	whitelist,
		uint8_t	id
	)

Definition at line 791 of file gec_dl.c.

References gec_whitelist::idx, gec_whitelist::init, gec_whitelist::whitelist, and WHITELIST_LEN.

Referenced by gec_transport_init().

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void gec_check_and_parse	(	struct link_device *	dev,
		struct gec_transport *	trans,
		uint8_t *	buf,
		bool *	msg_available
	)

Parsing a frame data and copy the payload to the datalink buffer.

bool gec_decrypt_message	(	uint8_t *	buf,
		volatile uint8_t *	payload_len
	)

Attemp message decryption If a message is unencrypted, pass it through only if the MSG_ID is in the whitelist Returns Pprzlink message bytes (source_ID .

. msg payload)

Input: expects (CRYPTO_BYTE .. MSG_DATA .. optional TAG) Output: returns stripped message (SENDER_ID .. MSG_PAYLOAD)

Definition at line 421 of file gec_dl.c.

References counter, gec_sym_key::counter, gec_sts_ctx::decrypt_err, gec_bytes_to_counter(), gec_is_in_the_whitelist(), gec_tp, gec_sym_key::key, gec_sym_key::nonce, PPRZ_AUTH_IDX, PPRZ_CNTR_IDX, PPRZ_CRYPTO_OVERHEAD, PPRZ_GEC_IDX, PPRZ_MAC_LEN, PPRZ_MSG_TYPE_ENCRYPTED, PPRZ_MSG_TYPE_PLAINTEXT, gec_sym_key::ready, gec_sts_ctx::rx_counter_err, gec_sts_ctx::rx_sym_key, gec_transport::sts, and gec_transport::whitelist.

Referenced by gec_dl_event().

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void gec_dl_event ( void )

Datalink Event.

While the status != Crypto_OK no message is returned, and all logic is handled internally. Returned message has format of Pprzlink 2.0 ```ignore payload[0] source SENDER_ID payload[1] destination ID payload[2] class/component payload[3] MSG_ID payload[4-end] MSG_PAYLOAD ``` or Pprzlink 1.0 ```ignore payload[0] source SENDER_ID payload[1] MSG_ID payload[2-end] MSG_PAYLOAD ``` and can be directly processed by a parser

NOTE: the KEY_EXCHANGE messages are whitelisted and thus pass through the "decryption" even if they are in plaintext and after the key exchange is established. This is not a problem, because we don't act on them. It would be good to limit "sending" them from other processes, but for now lets assume nobody will want to send this message.

In the future, the KEY_EXCHANGE messages should be handled even in CRYPTO_OK mode and acted upon accordingly (i.e. the key renegotiation will be possible). For now, I am keeping this note here as a reminder.

Definition at line 524 of file gec_dl.c.

References CRYPTO_OK, DatalinkFillDlBuffer, dl_buffer, dl_msg_available, DlCheckAndParse(), DOWNLINK_DEVICE, gec_decrypt_message(), gec_process_msg1(), gec_process_msg3(), gec_tp, LED_ON, gec_transport::pprz_tp, gec_sts_ctx::protocol_stage, gec_transport::sts, gec_transport::trans_rx, gec_transport::trans_tx, WAIT_MSG1, and WAIT_MSG3.

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void gec_dl_init ( void )

Init function.

Definition at line 336 of file gec_dl.c.

References DefaultPeriodic, gec_sts_init(), gec_tp, gec_transport_init(), LED_OFF, gec_transport::pprz_tp, register_periodic_telemetry(), send_secure_link_info(), and gec_transport::sts.

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bool gec_encrypt_message	(	uint8_t *	buf,
		uint8_t *	payload_len
	)

Attempts message encryption Adds crypto_byte, counter and tag Returns encrypted pprzlink message (crypto_byte .

. tag) in the same buffer as was the incoming message

Definition at line 362 of file gec_dl.c.

References counter, gec_sym_key::counter, gec_sts_ctx::encrypt_err, gec_counter_to_bytes(), gec_tp, gec_sym_key::key, gec_sym_key::nonce, PPRZ_AUTH_IDX, PPRZ_CNTR_IDX, PPRZ_CRYPTO_OVERHEAD, PPRZ_GEC_IDX, PPRZ_MAC_LEN, PPRZ_MSG_TYPE_ENCRYPTED, gec_sym_key::ready, gec_transport::sts, and gec_sts_ctx::tx_sym_key.

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bool gec_is_in_the_whitelist	(	struct gec_whitelist *	whitelist,
		uint8_t	id
	)

Definition at line 805 of file gec_dl.c.

References gec_whitelist::idx, gec_whitelist::init, and gec_whitelist::whitelist.

Referenced by gec_decrypt_message().

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void gec_process_msg1 ( uint8_t * buf )

NOTE: for RESPONDER party only Process incoming message (expected MSG1) if the right (KEY_EXCHANGE) message received with the right data (P_AE) and the right P_AE.len=PPRZ_KEY_LEN, the internal state of Sts gets updated (key derivation etc), and msg2 is prepared to be sent.

Input: decrypted message (source_ID .. msg payload) If all good, it sends response message

Definition at line 588 of file gec_dl.c.

References DOWNLINK_DEVICE, gec_derive_key_material(), gec_generate_ephemeral_keys(), gec_tp, gec_sym_key::key, gec_sts_ctx::last_error, MSG1_ENCRYPT_ERROR, gec_sts_ctx::my_private_ephemeral, gec_sts_ctx::my_private_key, gec_sym_key::nonce, P_AE, P_BE, PPRZ_GEC_IDX, PPRZ_KEY_LEN, PPRZ_MAC_LEN, PPRZ_MSG_TYPE_PLAINTEXT, PPRZ_SIGN_LEN, gec_transport::pprz_tp, gec_privkey::priv, gec_sts_ctx::protocol_stage, gec_privkey::pub, gec_pubkey::pub, gec_privkey::ready, gec_pubkey::ready, gec_transport::sts, gec_sts_ctx::their_public_ephemeral, gec_transport::tx_msg, gec_transport::tx_msg_idx, gec_sts_ctx::tx_sym_key, UNEXPECTED_MSG_DATA_ERROR, UNEXPECTED_MSG_ERROR, UNEXPECTED_MSG_TYPE_ERROR, and WAIT_MSG3.

Referenced by gec_dl_event().

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bool gec_process_msg3 ( uint8_t * buf )

Process incoming message (expected MSG3) if the right (KEY_EXCHANGE) message received with the right data (SIG) and the right SIG.len=PPRZ_SIGN_LEN, and the signature is verified, Ok() is returned.

Input: decrypted message (source_ID .. msg payload) Returns true if this party is ready for communication

Definition at line 735 of file gec_dl.c.

References gec_tp, gec_sym_key::key, gec_sts_ctx::last_error, MSG3_DECRYPT_ERROR, MSG3_SIGNVERIFY_ERROR, gec_sts_ctx::my_private_ephemeral, gec_sym_key::nonce, PPRZ_KEY_LEN, PPRZ_MAC_LEN, PPRZ_SIGN_LEN, gec_privkey::pub, gec_pubkey::pub, gec_sts_ctx::rx_sym_key, SIG, gec_transport::sts, gec_sts_ctx::their_public_ephemeral, gec_sts_ctx::their_public_key, UNEXPECTED_MSG_DATA_ERROR, UNEXPECTED_MSG_ERROR, and UNEXPECTED_MSG_TYPE_ERROR.