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-rw-r--r--include/cobs.h6
-rw-r--r--src/cobs.c115
-rw-r--r--src/noise.c2
-rw-r--r--src/packet_interface.c20
4 files changed, 117 insertions, 26 deletions
diff --git a/include/cobs.h b/include/cobs.h
index 6c70c02..1cc2681 100644
--- a/include/cobs.h
+++ b/include/cobs.h
@@ -17,7 +17,11 @@ ssize_t cobs_decode(char *dst, size_t dstlen, char *src, size_t srclen);
int cobs_encode_incremental(void *f, int (*output)(void *, char), char *src, size_t srclen);
+/*@ requires \valid(state);
+ ensures state->p == 0 && state->c == 0;
+ assigns *state;
+ @*/
void cobs_decode_incremental_initialize(struct cobs_decode_state *state);
-int cobs_decode_incremental(struct cobs_decode_state *state, char *dst, size_t dstlen, char src);
+int cobs_decode_incremental(struct cobs_decode_state *state, unsigned char *dst, size_t dstlen, unsigned char src);
#endif//__COBS_H__
diff --git a/src/cobs.c b/src/cobs.c
index 27bc24d..0d60517 100644
--- a/src/cobs.c
+++ b/src/cobs.c
@@ -213,20 +213,66 @@ void cobs_decode_incremental_initialize(struct cobs_decode_state *state) {
state->c = 0;
}
-int cobs_decode_incremental(struct cobs_decode_state *state, char *dst, size_t dstlen, char src) {
+/*@ requires \separated(state, dst + (0..dstlen-1));
+ requires \valid(state);
+ requires \valid(dst + (0..dstlen-1));
+ requires 0 < dstlen <= 65535;
+ requires 0 <= state->p <= dstlen+1;
+ requires state->p != 0 ==> 1 <= state->c <= 255;
+
+ ensures state->p != 0 ==> 1 <= state->c <= 255;
+ ensures 0 <= state->p <= dstlen+1;
+ ensures 0 <= \result <= dstlen || \result \in {-1, -2, -3, -4};
+ ensures \result < -1 ==> state->p == 0 && state->c == 0;
+ assigns *state, dst[0..dstlen-1];
+
+ behavior eof_bad_empty_frame:
+ assumes state->p == 0 && src == 0;
+ ensures \result == -3;
+ assigns *state;
+
+ behavior eof_good_frame:
+ assumes state->p != 0 && src == 0;
+ ensures \result >= 0 || \result == -2;
+ assigns *state;
+
+ behavior decoding_no_overflow:
+ assumes src != 0 && state->p <= dstlen;
+ ensures \result == -1;
+ assigns *state, dst[0..dstlen-1];
+
+ behavior decoding_overflow:
+ assumes src != 0 && state->p > dstlen;
+ ensures \result == -4;
+ assigns *state;
+
+ complete behaviors;
+ disjoint behaviors;
+ @*/
+int cobs_decode_incremental(struct cobs_decode_state *state, unsigned char *dst, size_t dstlen, unsigned char src) {
if (state->p == 0) {
- if (src == 0)
- goto empty_errout; /* invalid framing. An empty frame would be [...] 00 01 00, not [...] 00 00 */
- state->c = (unsigned char)src;
+ if (src == 0) {
+ /* invalid framing. An empty frame would be [...] 00 01 00, not [...] 00 00 */
+ cobs_decode_incremental_initialize(state);
+ //@ assert 0 <= state->p <= dstlen;
+ return -3;
+ }
+ state->c = src;
state->p++;
- return 0;
+ //@ assert 0 <= state->p <= dstlen;
+ return -1;
}
if (!src) {
- if (state->c != 1)
- goto errout; /* Invalid framing. The skip counter does not hit the end of the frame. */
- int rv = state->p-1;
+ if (state->c != 1) {
+ /* Invalid framing. The skip counter does not hit the end of the frame. */
+ cobs_decode_incremental_initialize(state);
+ //@ assert 0 <= state->p <= dstlen;
+ return -2;
+ }
+ size_t rv = state->p-1;
cobs_decode_incremental_initialize(state);
+ //@ assert 0 <= state->p <= dstlen;
return rv;
}
@@ -234,26 +280,59 @@ int cobs_decode_incremental(struct cobs_decode_state *state, char *dst, size_t d
state->c--;
if (state->c == 0) {
- state->c = (unsigned char)src;
+ state->c = src;
val = 0;
} else {
val = src;
}
size_t pos = state->p-1;
- if (pos >= dstlen)
- return -2; /* output buffer too small */
+ if (pos >= dstlen) {
+ cobs_decode_incremental_initialize(state);
+ //@ assert 0 <= state->p <= dstlen+1;
+ return -4; /* output buffer too small */
+ }
dst[pos] = val;
+ //@ assert 0 <= state->p <= dstlen;
state->p++;
- return 0;
-
-errout:
- cobs_decode_incremental_initialize(state);
+ //@ assert 0 <= state->p <= dstlen+1;
return -1;
+}
+
+/*@ requires \valid_read(buf + (0..len-1));
+ assigns \nothing;
+ @*/
+void handle_packet(unsigned char *buf, size_t len);
-empty_errout:
- cobs_decode_incremental_initialize(state);
- return -3;
+/*@ requires \valid(dst + (0..dstlen-1));
+ requires \valid_read(src + (0..srclen-1));
+ requires 0 < dstlen <= 65535;
+ assigns dst[0..dstlen-1];
+ @*/
+void cobs_decode_test(unsigned char *src, size_t srclen, unsigned char *dst, size_t dstlen) {
+ struct cobs_decode_state state;
+ cobs_decode_incremental_initialize(&state);
+ //@ assert state.p == 0;
+ //@ assert state.c == 0;
+ //@ assert state.p != 0 ==> 1 <= state.c <= 255;
+ /*@ loop invariant \separated(&state, dst + (0..dstlen-1), &i);
+ loop invariant \valid(&state);
+ loop invariant \valid(dst + (0..dstlen-1));
+ loop invariant 0 < dstlen <= 65535;
+ loop invariant 0 <= state.p <= dstlen+1;
+ loop invariant state.p != 0 ==> 1 <= state.c <= 255;
+ loop assigns dst[0..dstlen-1], state, i;
+ loop variant srclen-i;
+ @*/
+ for (size_t i=0; i<srclen; i++) {
+ int rv = cobs_decode_incremental(&state, dst, dstlen, src[i]);
+ if (rv >= 0)
+ handle_packet(dst, rv);
+ if (rv == -1)
+ continue;
+ if (rv < -1)
+ continue;
+ }
}
#ifdef VALIDATION
diff --git a/src/noise.c b/src/noise.c
index 890b5b5..949a68d 100644
--- a/src/noise.c
+++ b/src/noise.c
@@ -199,8 +199,6 @@ void uninit_handshake(struct NoiseState *st, enum handshake_state new_state) {
requires \separated(&usart2_out, st, buf, st->handshake, &st->handshake_hash);
- 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));
diff --git a/src/packet_interface.c b/src/packet_interface.c
index 441fff9..98a1ef2 100644
--- a/src/packet_interface.c
+++ b/src/packet_interface.c
@@ -66,17 +66,27 @@ void usart2_isr(void) {
}
ssize_t rv = cobs_decode_incremental(&host_cobs_state, (char *)host_packet_buf, sizeof(host_packet_buf), data);
- if (rv == -2) {
- LOG_PRINTF("Host interface COBS packet too large\n");
+ if (rv == 0) {
+ /* good, empty frame */
+ LOG_PRINTF("Got empty frame from host\n");
+ host_packet_length = -1;
+ } else if (rv == -1) {
+ /* Decoding frame, wait for next byte */
+ } else if (rv == -2) {
+ LOG_PRINTF("Host interface COBS framing error\n");
host_packet_length = -1;
} else if (rv == -3) {
+ /* invalid empty frame */
LOG_PRINTF("Got double null byte from host\n");
- } else if (rv < 0) {
- LOG_PRINTF("Host interface COBS framing error\n");
+ host_packet_length = -1;
+ } else if (rv == -4) {
+ /* frame too large */
+ LOG_PRINTF("Got too large frame from host\n");
host_packet_length = -1;
} else if (rv > 0) {
+ /* Good, non-empty frame */
host_packet_length = rv;
- } /* else just return and wait for next byte */
+ }
TRACING_CLEAR(TR_HOST_IF_USART_IRQ);
}