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[dhcp] fix raw server option bounds checks #11940

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Merged
Rbb666 merged 1 commit into from
Oct 28, 2026
+23 −5
Merged

[dhcp] fix raw server option bounds checks #11940

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28 changes: 23 additions & 5 deletions components/net/lwip-dhcpd/dhcp_server_raw.c
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Original file line number Diff line number Diff line change
Expand Up @@ -35,6 +35,7 @@

#include <stdio.h>
#include <stdint.h>
#include <string.h>

#include <rtthread.h>

Expand Down Expand Up @@ -204,7 +205,7 @@ dhcp_client_find(struct dhcp_server *dhcpserver, struct dhcp_msg *msg,
}

opt = dhcp_server_option_find(opt_buf, len, DHCP_OPTION_REQUESTED_IP);
if (opt != NULL)
if (opt != NULL && opt[1] >= 4)
{
node = dhcp_client_find_by_ip(dhcpserver, (ip4_addr_t *)(&opt[2]));
if (node != NULL)
Expand Down Expand Up @@ -240,7 +241,7 @@ dhcp_client_alloc(struct dhcp_server *dhcpserver, struct dhcp_msg *msg,
}

opt = dhcp_server_option_find(opt_buf, len, DHCP_OPTION_REQUESTED_IP);
if (opt != NULL)
if (opt != NULL && opt[1] >= 4)
{
node = dhcp_client_find_by_ip(dhcpserver, (ip4_addr_t *)(&opt[2]));
if (node != NULL)
Expand Down Expand Up @@ -287,8 +288,24 @@ static u8_t *
dhcp_server_option_find(u8_t *buf, u16_t len, u8_t option)
{
u8_t *end = buf + len;
u16_t remaining;

while ((buf < end) && (*buf != DHCP_OPTION_END))
{
remaining = end - buf;

/* need at least option + length */
if (remaining < 2)
{
break;
}

/* option data must stay within the received packet */
if (buf[1] > remaining - 2)
{
break;
}

if (*buf == option)
{
return buf;
Expand Down Expand Up @@ -321,7 +338,7 @@ dhcp_server_recv(void *arg, struct udp_pcb *pcb, struct pbuf *p, const ip_addr_t
LWIP_UNUSED_ARG(addr);
LWIP_UNUSED_ARG(port);

if (p->len < DHCP_MIN_REQUEST_LEN)
if (p->len < DHCP_MIN_REQUEST_LEN || p->tot_len < DHCP_OPTIONS_OFS)
{
LWIP_DEBUGF(DHCP_DEBUG | LWIP_DBG_TRACE | LWIP_DBG_LEVEL_WARNING, ("DHCP request message or pbuf too short\n"));
pbuf_free(p);
Expand All @@ -343,6 +360,8 @@ dhcp_server_recv(void *arg, struct udp_pcb *pcb, struct pbuf *p, const ip_addr_t
return;
}

/* Parse only bytes actually received, not the whole allocated buffer. */
length = p->tot_len - DHCP_OPTIONS_OFS;
pbuf_copy(q, p);
pbuf_free(p);

Expand All @@ -365,9 +384,8 @@ dhcp_server_recv(void *arg, struct udp_pcb *pcb, struct pbuf *p, const ip_addr_t
}

opt_buf = (u8_t *)msg + DHCP_OPTIONS_OFS;
length = q->tot_len - DHCP_OPTIONS_OFS;
opt = dhcp_server_option_find(opt_buf, length, DHCP_OPTION_MESSAGE_TYPE);
if (opt)
if (opt && opt[1] >= 1)
{
msg_type = *(opt + 2);
if (msg_type == DHCP_DISCOVER)
Expand Down
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