lwIP - A Lightweight TCP/IP stack - Bugs: bug #61479, MQTT: DoS caused by unsigned...
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bug #61479: MQTT: DoS caused by unsigned integer overflow
Submitter: | Hyeonsu Kim <icekrim> | ||
Submitted: | Sun 14 Nov 2021 06:31:19 AM UTC | ||
Category: | Security-related | Severity: | 3 - Normal |
Item Group: | Crash Error | Status: | None |
Privacy: | Public | Assigned to: | None |
Open/Closed: | Open | Planned Release: | None |
lwIP version: | git head |
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Depends on the following items: None found
Items that depend on this one: None found
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Corresponding source code
Summary:
Integer overflow in mqtt_parse_incoming of src/apps/mqtt/mqtt.c allows attackers to perform a Denial of Service via MQTT packet with fixed header length of 256 bytes or more
Description:
mqtt.c 866
while (p->tot_len > in_offset) {
if ((fixed_hdr_len < 2) || ((b & 0x80) != 0)) {
if (fixed_hdr_len < client->msg_idx) {
b = client->rx_buffer[fixed_hdr_len];
} else {
b = pbuf_get_at(p, in_offset++);
client->rx_buffer[client->msg_idx++] = b;
}
fixed_hdr_len++;
if (fixed_hdr_len >= 2) {
msg_rem_len |= (u32_t)(b & 0x7f) << ((fixed_hdr_len - 2) * 7);
if ((b & 0x80) == 0) {
....
If it receives a packet of 256 bytes with b & 80 == 1, it goes into an infinite loop and the device stops. (like [0x80]*256)
This is because fixed_hdr_len, which is a u8 type, can never be larger than client->msg_idx (in this case 256), so in_offset cannot be increased.
I have completed the POC on the stm32 board I have personally, and I will prepare linux porting if necessary. Thank you.