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net/emcute: check value of length field before use

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This commit is contained in:
Hauke Petersen 2017-06-22 13:53:12 +02:00
parent d31d870b26
commit ae367e5537
2 changed files with 24 additions and 9 deletions
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2
sys/include/net/emcute.h
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@ -210,7 +210,7 @@ typedef struct {
* @brief Signature for callbacks fired when publish messages are received * @brief Signature for callbacks fired when publish messages are received
* *
* @param[in] topic topic the received data was published on * @param[in] topic topic the received data was published on
* @param[in] data published data * @param[in] data published data, can be NULL
* @param[in] len length of @p data in bytes * @param[in] len length of @p data in bytes
*/ */
typedef void(*emcute_cb_t)(const emcute_topic_t *topic, void *data, size_t len); typedef void(*emcute_cb_t)(const emcute_topic_t *topic, void *data, size_t len);

31
sys/net/application_layer/emcute/emcute.c
View File

@ -165,21 +165,24 @@ static void on_ack(uint8_t type, int id_pos, int ret_pos, int res_pos)
} }
} }
static void on_publish(void) static void on_publish(uint16_t len, int pos)
{ {
/* make sure packet length is valid - if not, drop packet silently */
if ((int)len < (pos + 6)) {
return;
}
emcute_sub_t *sub; emcute_sub_t *sub;
uint16_t len;
int pos = get_len(rbuf, &len);
uint16_t tid = get_u16(&rbuf[pos + 2]); uint16_t tid = get_u16(&rbuf[pos + 2]);
/* allocate a response packet */ /* allocate a response packet */
uint8_t buf[7] = { 7, PUBACK, 0, 0, 0, 0, ACCEPT }; uint8_t buf[7] = { 7, PUBACK, 0, 0, 0, 0, ACCEPT };
/* and populate message ID and topic ID fields */ /* and populate message ID and topic ID fields */
memcpy(&buf[2], &rbuf[3], 4); memcpy(&buf[2], &rbuf[pos + 2], 4);
/* return error code in case we don't support/understand active flags. So /* return error code in case we don't support/understand active flags. So
* far we only understand QoS 1... */ * far we only understand QoS 1... */
if (rbuf[2] & ~(EMCUTE_QOS_1 | EMCUTE_TIT_SHORT)) { if (rbuf[pos + 1] & ~(EMCUTE_QOS_1 | EMCUTE_TIT_SHORT)) {
buf[6] = REJ_NOTSUP; buf[6] = REJ_NOTSUP;
sock_udp_send(&sock, &buf, 7, &gateway); sock_udp_send(&sock, &buf, 7, &gateway);
return; return;
@ -193,11 +196,13 @@ static void on_publish(void)
DEBUG("[emcute] on pub: no subscription found\n"); DEBUG("[emcute] on pub: no subscription found\n");
} }
else { else {
if (rbuf[2] & EMCUTE_QOS_1) { if (rbuf[pos + 1] & EMCUTE_QOS_1) {
sock_udp_send(&sock, &buf, 7, &gateway); sock_udp_send(&sock, &buf, 7, &gateway);
} }
DEBUG("[emcute] on pub: got %i bytes of data\n", (int)(len - pos - 6)); DEBUG("[emcute] on pub: got %i bytes of data\n", (int)(len - pos - 6));
sub->cb(&sub->topic, &rbuf[pos + 6], (size_t)(len - pos - 6)); size_t dat_len = (len - pos - 6);
void *dat = (dat_len > 0) ? &rbuf[pos + 6] : NULL;
sub->cb(&sub->topic, dat, dat_len);
} }
} }
@ -532,7 +537,17 @@ void emcute_run(uint16_t port, const char *id)
if (len >= 2) { if (len >= 2) {
/* handle the packet */ /* handle the packet */
uint16_t pkt_len; uint16_t pkt_len;
/* catch invalid length field */
if ((len == 2) && (rbuf[0] == 0x01)) {
continue;
}
/* parse length field */
int pos = get_len(rbuf, &pkt_len); int pos = get_len(rbuf, &pkt_len);
/* verify length to prevent overflows */
if (((ssize_t)pkt_len > len) || ((ssize_t)pos >= len)) {
continue;
}
/* get packet type */
uint8_t type = rbuf[pos]; uint8_t type = rbuf[pos];
switch (type) { switch (type) {
@ -540,7 +555,7 @@ void emcute_run(uint16_t port, const char *id)
case WILLTOPICREQ: on_ack(type, 0, 0, 0); break; case WILLTOPICREQ: on_ack(type, 0, 0, 0); break;
case WILLMSGREQ: on_ack(type, 0, 0, 0); break; case WILLMSGREQ: on_ack(type, 0, 0, 0); break;
case REGACK: on_ack(type, 4, 6, 2); break; case REGACK: on_ack(type, 4, 6, 2); break;
case PUBLISH: on_publish(); break; case PUBLISH: on_publish(len, pos); break;
case PUBACK: on_ack(type, 4, 6, 0); break; case PUBACK: on_ack(type, 4, 6, 0); break;
case SUBACK: on_ack(type, 5, 7, 3); break; case SUBACK: on_ack(type, 5, 7, 3); break;
case UNSUBACK: on_ack(type, 2, 0, 0); break; case UNSUBACK: on_ack(type, 2, 0, 0); break;