[systemd-devel] [PATCH 1/2] dhcp-network: add check for DHCP.chaddr
Michal Sekletar
msekleta at redhat.com
Thu Jun 19 13:02:13 PDT 2014
On Thu, Jun 19, 2014 at 12:02:39PM -0500, Dan Williams wrote:
> On Thu, 2014-06-19 at 18:59 +0200, Michal Sekletar wrote:
> > 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.
>
> And if the MAC address is not 48 bits (Infiniband) or the interface type
> doesn't really have a MAC address (PPP/PPPoE)? DHCP can be used in both
> cases... If anything, the code that uses the MAC address should be
> if-ed so it only executes when a MAC address is provided.
Yep, valid concerns indeed. Will post v2 tomorrow. Thanks!
>
> Dan
Michal
>
> > ---
> > src/libsystemd-network/dhcp-internal.h | 3 ++-
> > src/libsystemd-network/dhcp-network.c | 15 +++++++++++++--
> > src/libsystemd-network/sd-dhcp-client.c | 4 ++--
> > src/libsystemd-network/test-dhcp-client.c | 2 +-
> > 4 files changed, 18 insertions(+), 6 deletions(-)
> >
> > diff --git a/src/libsystemd-network/dhcp-internal.h b/src/libsystemd-network/dhcp-internal.h
> > index 03cc824..fd86a70 100644
> > --- a/src/libsystemd-network/dhcp-internal.h
> > +++ b/src/libsystemd-network/dhcp-internal.h
> > @@ -24,12 +24,13 @@
> >
> > #include <stdint.h>
> > #include <linux/if_packet.h>
> > +#include <net/ethernet.h>
> >
> > #include "socket-util.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);
> > diff --git a/src/libsystemd-network/dhcp-network.c b/src/libsystemd-network/dhcp-network.c
> > index d7ba0ef..e5fd6a8 100644
> > --- a/src/libsystemd-network/dhcp-network.c
> > +++ b/src/libsystemd-network/dhcp-network.c
> > @@ -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 ? */
> > @@ -56,7 +56,18 @@ 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 */
> > diff --git a/src/libsystemd-network/sd-dhcp-client.c b/src/libsystemd-network/sd-dhcp-client.c
> > index c1af6df..d44cad2 100644
> > --- a/src/libsystemd-network/sd-dhcp-client.c
> > +++ b/src/libsystemd-network/sd-dhcp-client.c
> > @@ -719,7 +719,7 @@ 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;
> > @@ -761,7 +761,7 @@ 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;
> > diff --git a/src/libsystemd-network/test-dhcp-client.c b/src/libsystemd-network/test-dhcp-client.c
> > index 450b6d4..7cbe10d 100644
> > --- a/src/libsystemd-network/test-dhcp-client.c
> > +++ b/src/libsystemd-network/test-dhcp-client.c
> > @@ -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;
>
>
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