lib: parse_canframe: guard delimiter reads with length checks

As Alex J pointed out in comment
https://github.com/linux-can/can-utils/issues/632#issuecomment-5746692502
the delimiters to detect CAN CC/FD/XL frames were read from the input
data without checking the length of that input data. This could lead
to an out-of-bounds read and to unintended detection of incorrect content.

Add a length check before reading those delimiters and also add/change
some comments to clarify the reasons for some assignments.

Reported-by: Alex J <jipaionut@gmail.com>
Signed-off-by: Oliver Hartkopp <socketcan@hartkopp.net>

canlogserver.c

@@ -177,7 +177,8 @@ int main(int argc, char **argv)
 	sigset_t sigset;
 	fd_set rdfs;
 	int s[MAXDEV];
-	int socki, accsocket;
+	int socki;
+	int accsocket = -1;
 	canid_t mask[MAXDEV] = {0};
 	canid_t value[MAXDEV] = {0};
 	int inv_filter[MAXDEV] = {0};
@@ -286,7 +287,7 @@ int main(int argc, char **argv)
 	inaddr.sin_addr.s_addr = htonl(INADDR_ANY);
 	inaddr.sin_port = htons(port);
 
-	while(bind(socki, (struct sockaddr*)&inaddr, sizeof(inaddr)) < 0) {
+	while(running && bind(socki, (struct sockaddr*)&inaddr, sizeof(inaddr)) < 0) {
 		struct timespec f = {
 			.tv_nsec = 100 * 1000 * 1000,
 		};
@@ -295,18 +296,28 @@ int main(int argc, char **argv)
 		nanosleep(&f, NULL);
 	}
 
+	/*
+	 * Check if loop exited due to signal (during nanosleep) rather than
+	 * successful bind.
+	 */
+	if (!running) {
+		close(socki);
+		return 128 + signal_num;
+	}
+
 	if (listen(socki, 3) != 0) {
 		perror("listen");
 		exit(1);
 	}
 
-	while(1) {
+	while(running) {
 		accsocket = accept(socki, (struct sockaddr*)&clientaddr, &sin_size);
 		if (accsocket > 0) {
 			//printf("accepted\n");
 			if (!fork())
 				break;
 			close(accsocket);
+			accsocket = -1;
 		}
 		else if (errno != EINTR) {
 			perror("accept");
@@ -314,6 +325,17 @@ int main(int argc, char **argv)
 		}
 	}
 
+	/*
+	 * Check if loop exited due to signal (accept returned EINTR) rather
+	 * than successful fork
+	 */
+	if (!running) {
+		if (accsocket > 0)
+			close(accsocket);
+		close(socki);
+		return 128 + signal_num;
+	}
+
 	for (i=0; i<currmax; i++) {
 
 		pr_debug("open %d '%s' m%08X v%08X i%d e%d.\n",

j1939_timedate/j1939_timedate_srv.c

@@ -41,6 +41,7 @@ static void gmtime_to_j1939_pgn_65254_td(struct j1939_time_date_packet *tdp)
 	utc_tm = gmtime_r(&now, &utc_tm_buf);
 	local_tm = localtime_r(&now, &local_tm_buf);
 
+	if (local_tm) {
 		/* Calculate the offsets */
 		hour_offset = local_tm->tm_hour - utc_tm->tm_hour;
 		minute_offset = local_tm->tm_min - utc_tm->tm_min;
@@ -52,6 +53,11 @@ static void gmtime_to_j1939_pgn_65254_td(struct j1939_time_date_packet *tdp)
 			else
 				hour_offset -= 24;  /* before midnight */
 		}
+	} else {
+		/* The local time offsets cannot be determined at the moment */
+		hour_offset = 0xF9;
+		minute_offset = 0xFF;
+	}		
 
 	/*
 	 * Seconds (spn959):

j1939_vehicle_position/j1939_vehicle_position_cmn.h

@@ -51,7 +51,7 @@ struct j1939_vp_err_msg {
 #define J1939_VP1_PRIO_DEFAULT				6
 #define J1939_VP1_MAX_TRANSFER_LENGH \
 	sizeof(struct j1939_vp1_packet)
-#define J1939_VP1_REPETITION_RATE_MS			5000
+#define J1939_VP1_REPETITION_RATE_MS			1000
 #define J1939_VP1_JITTER_MS				500
 
 /**
@@ -63,8 +63,8 @@ struct j1939_vp_err_msg {
  *           - Data Length: 4 bytes
  *           - Resolution: 10^-7 deg/bit
  *           - Offset: -210 degrees
- *           - Range: -210 to +211.1008122 degrees
+ *           - Range: -210 to +211.10081215 degrees
- *           - Operating Range: -210 degrees (SOUTH) to +211.108122 degrees
+ *           - Operating Range: -210 degrees (SOUTH) to +211.1081215 degrees
  *             (NORTH)
  *
  * @longitude: Raw longitude position of the vehicle
@@ -72,8 +72,8 @@ struct j1939_vp_err_msg {
  *           - Data Length: 4 bytes
  *           - Resolution: 10^-7 deg/bit
  *           - Offset: -210 degrees
- *           - Range: -210 to +211.1008122 degrees
+ *           - Range: -210 to +211.10081215 degrees
- *           - Operating Range: -210 degrees (WEST) to +211.108122 degrees
+ *           - Operating Range: -210 degrees (WEST) to +211.1081215 degrees
  *             (EAST)
  *
  * This structure defines each component of the Vehicle Position as described in
@@ -142,32 +142,35 @@ j1939_vp1_set_longitude(struct j1939_vp1_packet *packet, int32_t longitude)
 /**
  * struct j1939_vp2_packet - Represents the PGN 64502 Vehicle
  *                                         Position 2 packet
- * FIXME: current packet layout is guessed based on limited information:
- * https://www.isobus.net/isobus/pGNAndSPN/10801?type=PGN
  *
  * @total_satellites: Total number of satellites in view
  *           - SPN: 8128
  *           - Data Length: 1 byte
+ *           - Range: 0 to 250
  *
  * @hdop: Horizontal dilution of precision
  *           - SPN: 8129
  *           - Data Length: 1 byte
  *           - Resolution: 0.1
+ *           - Range: 0.0 to 25.0
  *
  * @vdop: Vertical dilution of precision
  *           - SPN: 8130
  *           - Data Length: 1 byte
  *           - Resolution: 0.1
+ *           - Range: 0.0 to 25.0
  *
  * @pdop: Position dilution of precision
  *           - SPN: 8131
  *           - Data Length: 1 byte
  *           - Resolution: 0.1
+ *           - Range: 0.0 to 25.0
  *
  * @tdop: Time dilution of precision
  *           - SPN: 8132
  *           - Data Length: 1 byte
  *           - Resolution: 0.1
+ *           - Range: 0.0 to 25.0
  *
  * This structure defines each component of the Vehicle Position 2 as described
  * in PGN 64502.
@@ -178,6 +181,9 @@ struct j1939_vp2_packet {
 	uint8_t vdop;             /* SPN 8130 */
 	uint8_t pdop;             /* SPN 8131 */
 	uint8_t tdop;             /* SPN 8132 */
+	uint8_t unused5;          /* Always 0xFF */
+	uint8_t unused6;          /* Always 0xFF */
+	uint8_t unused7;          /* Always 0xFF */
 } __attribute__((__packed__));
 
 /**

j1939_vehicle_position/j1939_vehicle_position_srv.c

@@ -270,6 +270,12 @@ static int j1939_vp2_get_data(struct j1939_vp_srv_priv *priv,
 	j1939_vp2_set_pdop(vp2p, pdop);
 	j1939_vp2_set_tdop(vp2p, tdop);
 
+	/* This PG's last 3 bytes are not assigned and hence must be set
+	 * to 0xFF as per J1939-71, section 5.2 */
+	vp2p->unused5 = 0xFF;
+	vp2p->unused6 = 0xFF;
+	vp2p->unused7 = 0xFF;
+
 	return 0;
 }
 

lib.c

@@ -170,21 +170,23 @@ int parse_canframe(char *cs, union cfu *cu)
 
 	memset(cu, 0, sizeof(*cu)); /* init CAN CC/FD/XL frame, e.g. LEN = 0 */
 
-	if (len < 4)
+	if (len >= 4 && cs[3] == CANID_DELIM) { /* 3 digits SFF CAN ID */
-		return 0;
 
-	if (cs[3] == CANID_DELIM) { /* 3 digits SFF */
+		idx = 4; /* start of frame data */
 
-		idx = 4;
+		/* get 3 digits SFF CAN ID value */
 		for (i = 0; i < 3; i++) {
 			if ((tmp = asc2nibble(cs[i])) > 0x0F)
 				return 0;
 			cu->cc.can_id |= tmp << (2 - i) * 4;
 		}
 
-	} else if (cs[5] == CANID_DELIM) { /* 5 digits CAN XL VCID/PRIO*/
+	} else if (len >= 21 && cs[5] == CANID_DELIM && cs[20] == CANID_DELIM) {
+		/* 5 digits CAN XL VCID/PRIO - but also check for 2nd '#' here */
 
-		idx = 6;
+		idx = 6; /* start of CAN XL frame extra content (AF, SDT, etc) */
+
+		/* get 5 digits CAN XL VCID/PRIO */
 		for (i = 0; i < 5; i++) {
 			if ((tmp = asc2nibble(cs[i])) > 0x0F)
 				return 0;
@@ -196,9 +198,11 @@ int parse_canframe(char *cs, union cfu *cu)
 		cu->xl.prio &= CANXL_PRIO_MASK;
 		cu->xl.prio |= tmp;
 
-	} else if (cs[8] == CANID_DELIM) { /* 8 digits EFF */
+	} else if (len >= 9 && cs[8] == CANID_DELIM) { /* 8 digits EFF CAN ID */
 
-		idx = 9;
+		idx = 9; /* start of frame data */
+
+		/* get 8 digits EFF CAN ID value */
 		for (i = 0; i < 8; i++) {
 			if ((tmp = asc2nibble(cs[i])) > 0x0F)
 				return 0;
@@ -239,11 +243,12 @@ int parse_canframe(char *cs, union cfu *cu)
 		cu->fd.flags |= CANFD_FDF; /* dual-use */
 		idx += 2;
 
-	} else if (cs[idx + 14] == CANID_DELIM) { /* CAN XL frame '#80:00:11223344#' */
+	} else if (idx == 6) { /* CAN XL frame extra content '#80:00:11223344#' */
 		maxdlen = CANXL_MAX_DLEN;
 		mtu = CANXL_MTU;
-		data = cu->xl.data; /* fill CAN XL data */
+		data = cu->xl.data; /* overwrite pointer to CAN XL data */
 
+		/* get CAN XL frame extra content */
 		if ((cs[idx + 2] != XL_HDR_DELIM) || (cs[idx + 5] != XL_HDR_DELIM))
 			return 0;
 
@@ -277,6 +282,7 @@ int parse_canframe(char *cs, union cfu *cu)
 		idx++; /* skip CANID_DELIM */
 	}
 
+	/* copy CAN frame data content */
 	for (i = 0, dlen = 0; i < maxdlen; i++) {
 		if (cs[idx] == DATA_SEPERATOR) /* skip (optional) separator */
 			idx++;