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Add beginnings of a frama-c proof of the protocol logic

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The proof works
This commit is contained in:
jaseg 2018-12-13 17:43:41 +09:00
parent a818c94fc4
commit 21240ce378
2 changed files with 37 additions and 3 deletions
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38
src/noise.c
View file

@ -8,6 +8,9 @@
#include "crypto/noise-c/src/crypto/blake2/blake2s.h"
#ifdef VERIFICATION
#define HANDLE_NOISE_ERROR(x, msg) if (x) { goto errout; }
#else
#define HANDLE_NOISE_ERROR(x, msg) do { \
err = x; \
if (err != NOISE_ERROR_NONE) { \
@ -17,6 +20,7 @@
goto errout; \
} \
} while(0);
#endif
volatile uint8_t host_packet_buf[MAX_HOST_PACKET_SIZE];
@ -83,7 +87,7 @@ int generate_identity_key(struct NoiseState *st) {
HANDLE_NOISE_ERROR(noise_dhstate_generate_keypair(dh), "generating key pair");
uint8_t unused[CURVE25519_KEY_LEN]; /* the noise api is a bit bad here. */
memset(st->local_key, 0, sizeof(*st->local_key));
memset(st->local_key, 0, sizeof(*st->local_key)); /* FIXME sizeof is wrong here */
HANDLE_NOISE_ERROR(noise_dhstate_get_keypair(dh, st->local_key, CURVE25519_KEY_LEN, unused, sizeof(unused)), "saving key pair");
@ -94,6 +98,15 @@ errout:
return -1;
}
/*@requires \valid(st);
requires new_state == HANDSHAKE_UNINITIALIZED ||
new_state == HANDSHAKE_NOT_STARTED ||
new_state == HANDSHAKE_IN_PROGRESS ||
new_state == HANDSHAKE_DONE_UNKNOWN_HOST ||
new_state == HANDSHAKE_DONE_KNOWN_HOST;
ensures st->handshake_state == new_state;
ensures st->handshake == NULL;
@*/
void uninit_handshake(struct NoiseState *st, enum handshake_state new_state) {
if (st->handshake)
noise_handshakestate_free(st->handshake);
@ -102,7 +115,24 @@ void uninit_handshake(struct NoiseState *st, enum handshake_state new_state) {
arm_key_scrubber();
}
int try_continue_noise_handshake(struct NoiseState *st, uint8_t *buf, size_t len) {
//@ ghost int key_checked_trace = 0;
//@ ghost int key_match_trace = 0;
/*@ requires empty_trace: key_checked_trace == 0;
requires \valid(st);
requires \valid(st->handshake);
requires \valid(st->remote_key + (0..sizeof(st->remote_key)-1));
requires \valid(st->handshake_hash + (0..sizeof(st->handshake_hash)-1));
requires \separated(st, buf);
requires \separated(&usart2_out, \union(st, buf));
requires \separated(&st->handshake, st);
assigns key_checked_trace;
ensures (st->handshake_state == HANDSHAKE_DONE_KNOWN_HOST) ==> key_checked_trace == 1;
ensures (st->handshake_state != HANDSHAKE_IN_PROGRESS) ==>
key_match_trace == 1 || (st->failed_handshakes > \old(st->failed_handshakes));
@*/
int try_continue_noise_handshake(struct NoiseState * const st, uint8_t *buf, size_t len) {
int err;
struct {
struct control_packet header;
@ -140,6 +170,7 @@ int try_continue_noise_handshake(struct NoiseState *st, uint8_t *buf, size_t len
HANDLE_NOISE_ERROR(noise_handshakestate_split(st->handshake, &st->tx_cipher, &st->rx_cipher), "splitting handshake state");
LOG_PRINTF("Noise protocol handshake completed successfully, handshake hash:\n");
//@ assert \valid(&st->handshake);
if (noise_handshakestate_get_handshake_hash(st->handshake, st->handshake_hash, sizeof(st->handshake_hash)) != NOISE_ERROR_NONE) {
LOG_PRINTF("Error fetching noise handshake state\n");
} else {
@ -150,6 +181,7 @@ int try_continue_noise_handshake(struct NoiseState *st, uint8_t *buf, size_t len
}
//@ assert \valid(&st->handshake);
NoiseDHState *remote_dh = noise_handshakestate_get_remote_public_key_dh(st->handshake);
if (!remote_dh) {
LOG_PRINTF("Error: Host has not identified itself\n");
@ -165,7 +197,9 @@ int try_continue_noise_handshake(struct NoiseState *st, uint8_t *buf, size_t len
BLAKE2s_update(&bc, st->remote_key, sizeof(st->remote_key));
BLAKE2s_finish(&bc, remote_fp);
//@ ghost key_checked_trace = 1;
if (!memcmp(remote_fp, st->remote_key_reference, sizeof(remote_fp))) { /* keys match */
//@ ghost key_match_trace = 1;
uint8_t response = REPORT_PAIRING_SUCCESS;
if (send_encrypted_message(st, &response, sizeof(response)))
LOG_PRINTF("Error sending pairing response packet\n");

2
src/noise.h
View file

@ -44,7 +44,7 @@ void persist_remote_key(struct NoiseState *st);
int start_protocol_handshake(struct NoiseState *st);
int reset_protocol_handshake(struct NoiseState *st);
int generate_identity_key(struct NoiseState *st);
int try_continue_noise_handshake(struct NoiseState *st, uint8_t *buf, size_t len);
int try_continue_noise_handshake(struct NoiseState * const st, uint8_t *buf, size_t len);
int send_encrypted_message(struct NoiseState *st, uint8_t *msg, size_t len);
void arm_key_scrubber(void);