shaba/systemd-stable
1
1
Fork 0
mirror of https://github.com/systemd/systemd-stable.git synced 2024-10-28 20:25:25 +03:00
Code

dhcp-network: add check for DHCP.chaddr

Browse Source 
Check that received DHCP packets actually include our MAC address in
chaddr field. BPF interpreter has 32 bit wide registers but MAC address
is 48 bits long so we have to do check in two steps.
This commit is contained in:
Michal Sekletar 2014-06-19 15:14:14 +02:00
parent 31cda3d175
commit 58587a7a0c
4 changed files with 18 additions and 6 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

3
src/libsystemd-network/dhcp-internal.h
View File

@ -24,13 +24,14 @@
#include <stdint.h>
#include <linux/if_packet.h>
#include <net/ethernet.h>
#include "socket-util.h"
#include "sd-dhcp-client.h"
#include "dhcp-protocol.h"
int dhcp_network_bind_raw_socket(int index, union sockaddr_union *link, uint32_t xid);
int dhcp_network_bind_raw_socket(int index, union sockaddr_union *link, uint32_t xid, struct ether_addr mac_addr);
int dhcp_network_bind_udp_socket(be32_t address, uint16_t port);
int dhcp_network_send_raw_socket(int s, const union sockaddr_union *link,
const void *packet, size_t len);

15
src/libsystemd-network/dhcp-network.c
View File

@ -33,7 +33,7 @@
#include "dhcp-internal.h"
int dhcp_network_bind_raw_socket(int index, union sockaddr_union *link,
uint32_t xid) {
uint32_t xid, struct ether_addr mac_addr) {
struct sock_filter filter[] = {
BPF_STMT(BPF_LD + BPF_W + BPF_LEN, 0), /* A <- packet length */
BPF_JUMP(BPF_JMP + BPF_JGE + BPF_K, sizeof(DHCPPacket), 1, 0), /* packet >= DHCPPacket ? */
@ -60,7 +60,18 @@ int dhcp_network_bind_raw_socket(int index, union sockaddr_union *link,
BPF_STMT(BPF_LD + BPF_W + BPF_ABS, offsetof(DHCPPacket, dhcp.xid)), /* A <- client identifier */
BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, xid, 1, 0), /* client identifier == xid ? */
BPF_STMT(BPF_RET + BPF_K, 0), /* ignore */
/* TODO: match chaddr */
BPF_STMT(BPF_LD + BPF_IMM, htobe32(*((unsigned int *) &mac_addr))), /* A <- 4 bytes of client's MAC */
BPF_STMT(BPF_MISC + BPF_TAX, 0), /* X <- A */
BPF_STMT(BPF_LD + BPF_W + BPF_ABS, offsetof(DHCPPacket, dhcp.chaddr)), /* A <- 4 bytes of MAC from dhcp.chaddr */
BPF_STMT(BPF_ALU + BPF_XOR + BPF_X, 0), /* A xor X */
BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, 0, 1, 0), /* A == 0 ? */
BPF_STMT(BPF_RET + BPF_K, 0), /* ignore */
BPF_STMT(BPF_LD + BPF_IMM, htobe16(*((unsigned short *) (((char *) &mac_addr) + 4)))), /* A <- remainder of client's MAC */
BPF_STMT(BPF_MISC + BPF_TAX, 0), /* X <- A */
BPF_STMT(BPF_LD + BPF_H + BPF_ABS, offsetof(DHCPPacket, dhcp.chaddr) + 4), /* A <- remainder of MAC from dhcp.chaddr */
BPF_STMT(BPF_ALU + BPF_XOR + BPF_X, 0), /* A xor X */
BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, 0, 1, 0), /* A == 0 ? */
BPF_STMT(BPF_RET + BPF_K, 0), /* ignore */
BPF_STMT(BPF_LD + BPF_W + BPF_ABS, offsetof(DHCPPacket, dhcp.magic)), /* A <- DHCP magic cookie */
BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, DHCP_MAGIC_COOKIE, 1, 0), /* cookie == DHCP magic cookie ? */
BPF_STMT(BPF_RET + BPF_K, 0), /* ignore */

4
src/libsystemd-network/sd-dhcp-client.c
View File

@ -751,7 +751,7 @@ static int client_start(sd_dhcp_client *client) {
client->xid = random_u32();
r = dhcp_network_bind_raw_socket(client->index, &client->link, client->xid);
r = dhcp_network_bind_raw_socket(client->index, &client->link, client->xid, client->client_id.mac_addr);
if (r < 0) {
client_stop(client, r);
return r;
@ -795,7 +795,7 @@ static int client_timeout_t2(sd_event_source *s, uint64_t usec, void *userdata)
client->state = DHCP_STATE_REBINDING;
client->attempt = 1;
r = dhcp_network_bind_raw_socket(client->index, &client->link, client->xid);
r = dhcp_network_bind_raw_socket(client->index, &client->link, client->xid, client->client_id.mac_addr);
if (r < 0) {
client_stop(client, r);
return 0;

2
src/libsystemd-network/test-dhcp-client.c
View File

@ -196,7 +196,7 @@ int dhcp_network_send_raw_socket(int s, const union sockaddr_union *link,
return 575;
}
int dhcp_network_bind_raw_socket(int index, union sockaddr_union *link, uint32_t id)
int dhcp_network_bind_raw_socket(int index, union sockaddr_union *link, uint32_t id, struct ether_addr mac)
{
if (socketpair(AF_UNIX, SOCK_STREAM, 0, test_fd) < 0)
return -errno;