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grub/grub-core/net/bootp.c
Andrei Borzenkov 6c0969eed5 net/dhcp: Allow overloading legacy bootfile and name field 
DHCP specifies a special dummy option OVERLOAD, to allow DHCP options to
spill over into the (legacy) BOOTFILE and SNAME fields.

Parse and handle this option properly.

Signed-off-by: Andre Przywara <andre.przywara@arm.com>
Reviewed-by: Daniel Kiper <daniel.kiper@oracle.com>
2020-09-21 16:58:21 -04:00

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/*
* GRUB -- GRand Unified Bootloader
* Copyright (C) 2010,2011 Free Software Foundation, Inc.
*
* GRUB is free software: you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation, either version 3 of the License, or
* (at your option) any later version.
*
* GRUB is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with GRUB. If not, see <http://www.gnu.org/licenses/>.
*/
#include <grub/net.h>
#include <grub/env.h>
#include <grub/i18n.h>
#include <grub/command.h>
#include <grub/net/ip.h>
#include <grub/net/netbuff.h>
#include <grub/net/udp.h>
#include <grub/datetime.h>
#if !defined(GRUB_MACHINE_EFI) && (defined(__i386__) || defined(__x86_64__))
#define GRUB_NET_BOOTP_ARCH 0x0000
#elif defined(GRUB_MACHINE_EFI) && defined(__x86_64__)
#define GRUB_NET_BOOTP_ARCH 0x0007
#elif defined(GRUB_MACHINE_EFI) && defined(__aarch64__)
#define GRUB_NET_BOOTP_ARCH 0x000B
#else
#error "unknown bootp architecture"
#endif
static grub_uint8_t dhcp_option_header[] = {GRUB_NET_BOOTP_RFC1048_MAGIC_0,
GRUB_NET_BOOTP_RFC1048_MAGIC_1,
GRUB_NET_BOOTP_RFC1048_MAGIC_2,
GRUB_NET_BOOTP_RFC1048_MAGIC_3};
static grub_uint8_t grub_userclass[] = {0x4D, 0x06, 0x05, 'G', 'R', 'U', 'B', '2'};
static grub_uint8_t grub_dhcpdiscover[] = {0x35, 0x01, 0x01};
static grub_uint8_t grub_dhcptime[] = {0x33, 0x04, 0x00, 0x00, 0x0e, 0x10};
enum
{
GRUB_DHCP_OPT_OVERLOAD_FILE = 1,
GRUB_DHCP_OPT_OVERLOAD_SNAME = 2,
};
static const void *
find_dhcp_option (const struct grub_net_bootp_packet *bp, grub_size_t size,
grub_uint8_t opt_code, grub_uint8_t *opt_len)
{
const grub_uint8_t *ptr;
grub_uint8_t overload = 0;
int end = 0;
grub_size_t i;
if (opt_len)
*opt_len = 0;
/* Is the packet big enough to hold at least the magic cookie? */
if (size < sizeof (*bp) + sizeof (grub_uint32_t))
return NULL;
/*
* Pointer arithmetic to point behind the common stub packet, where
* the options start.
*/
ptr = (grub_uint8_t *) (bp + 1);
if (ptr[0] != GRUB_NET_BOOTP_RFC1048_MAGIC_0
|| ptr[1] != GRUB_NET_BOOTP_RFC1048_MAGIC_1
|| ptr[2] != GRUB_NET_BOOTP_RFC1048_MAGIC_2
|| ptr[3] != GRUB_NET_BOOTP_RFC1048_MAGIC_3)
return NULL;
size -= sizeof (*bp);
i = sizeof (grub_uint32_t);
again:
while (i < size)
{
grub_uint8_t tagtype;
grub_uint8_t taglength;
tagtype = ptr[i++];
/* Pad tag. */
if (tagtype == GRUB_NET_BOOTP_PAD)
continue;
/* End tag. */
if (tagtype == GRUB_NET_BOOTP_END)
{
end = 1;
break;
}
if (i >= size)
return NULL;
taglength = ptr[i++];
if (i + taglength >= size)
return NULL;
/* FIXME RFC 3396 options concatentation */
if (tagtype == opt_code)
{
if (opt_len)
*opt_len = taglength;
return &ptr[i];
}
if (tagtype == GRUB_NET_DHCP_OVERLOAD && taglength == 1)
overload = ptr[i];
i += taglength;
}
if (!end)
return NULL;
/* RFC2131, 4.1, 23ff:
* If the options in a DHCP message extend into the 'sname' and 'file'
* fields, the 'option overload' option MUST appear in the 'options'
* field, with value 1, 2 or 3, as specified in RFC 1533. If the
* 'option overload' option is present in the 'options' field, the
* options in the 'options' field MUST be terminated by an 'end' option,
* and MAY contain one or more 'pad' options to fill the options field.
* The options in the 'sname' and 'file' fields (if in use as indicated
* by the 'options overload' option) MUST begin with the first octet of
* the field, MUST be terminated by an 'end' option, and MUST be
* followed by 'pad' options to fill the remainder of the field. Any
* individual option in the 'options', 'sname' and 'file' fields MUST be
* entirely contained in that field. The options in the 'options' field
* MUST be interpreted first, so that any 'option overload' options may
* be interpreted. The 'file' field MUST be interpreted next (if the
* 'option overload' option indicates that the 'file' field contains
* DHCP options), followed by the 'sname' field.
*
* FIXME: We do not explicitly check for trailing 'pad' options here.
*/
end = 0;
if (overload & GRUB_DHCP_OPT_OVERLOAD_FILE)
{
overload &= ~GRUB_DHCP_OPT_OVERLOAD_FILE;
ptr = (grub_uint8_t *) &bp->boot_file[0];
size = sizeof (bp->boot_file);
i = 0;
goto again;
}
if (overload & GRUB_DHCP_OPT_OVERLOAD_SNAME)
{
overload &= ~GRUB_DHCP_OPT_OVERLOAD_SNAME;
ptr = (grub_uint8_t *) &bp->server_name[0];
size = sizeof (bp->server_name);
i = 0;
goto again;
}
return NULL;
}
#define OFFSET_OF(x, y) ((grub_size_t)((grub_uint8_t *)((y)->x) - (grub_uint8_t *)(y)))
struct grub_net_network_level_interface *
grub_net_configure_by_dhcp_ack (const char *name,
struct grub_net_card *card,
grub_net_interface_flags_t flags,
const struct grub_net_bootp_packet *bp,
grub_size_t size,
int is_def, char **device, char **path)
{
grub_net_network_level_address_t addr;
grub_net_link_level_address_t hwaddr;
struct grub_net_network_level_interface *inter;
int mask = -1;
char server_ip[sizeof ("xxx.xxx.xxx.xxx")];
const grub_uint8_t *opt;
grub_uint8_t opt_len;
addr.type = GRUB_NET_NETWORK_LEVEL_PROTOCOL_IPV4;
addr.ipv4 = bp->your_ip;
if (device)
*device = 0;
if (path)
*path = 0;
grub_memcpy (hwaddr.mac, bp->mac_addr,
bp->hw_len < sizeof (hwaddr.mac) ? bp->hw_len
: sizeof (hwaddr.mac));
hwaddr.type = GRUB_NET_LINK_LEVEL_PROTOCOL_ETHERNET;
inter = grub_net_add_addr (name, card, &addr, &hwaddr, flags);
if (!inter)
return 0;
if (size > OFFSET_OF (boot_file, bp))
grub_env_set_net_property (name, "boot_file", bp->boot_file,
sizeof (bp->boot_file));
if (bp->server_ip)
{
grub_snprintf (server_ip, sizeof (server_ip), "%d.%d.%d.%d",
((grub_uint8_t *) &bp->server_ip)[0],
((grub_uint8_t *) &bp->server_ip)[1],
((grub_uint8_t *) &bp->server_ip)[2],
((grub_uint8_t *) &bp->server_ip)[3]);
grub_env_set_net_property (name, "next_server", server_ip, sizeof (server_ip));
grub_print_error ();
}
if (is_def)
grub_net_default_server = 0;
if (is_def && !grub_net_default_server && bp->server_ip)
{
grub_net_default_server = grub_strdup (server_ip);
grub_print_error ();
}
if (is_def)
{
grub_env_set ("net_default_interface", name);
grub_env_export ("net_default_interface");
}
if (device && !*device && bp->server_ip)
{
*device = grub_xasprintf ("tftp,%s", server_ip);
grub_print_error ();
}
if (size > OFFSET_OF (server_name, bp)
&& bp->server_name[0])
{
grub_env_set_net_property (name, "dhcp_server_name", bp->server_name,
sizeof (bp->server_name));
if (is_def && !grub_net_default_server)
{
grub_net_default_server = grub_strdup (bp->server_name);
grub_print_error ();
}
if (device && !*device)
{
*device = grub_xasprintf ("tftp,%s", bp->server_name);
grub_print_error ();
}
}
if (size > OFFSET_OF (boot_file, bp) && path)
{
*path = grub_strndup (bp->boot_file, sizeof (bp->boot_file));
grub_print_error ();
if (*path)
{
char *slash;
slash = grub_strrchr (*path, '/');
if (slash)
*slash = 0;
else
**path = 0;
}
}
opt = find_dhcp_option (bp, size, GRUB_NET_BOOTP_NETMASK, &opt_len);
if (opt && opt_len == 4)
{
int i;
for (i = 0; i < 32; i++)
if (!(opt[i / 8] & (1 << (7 - (i % 8)))))
break;
mask = i;
}
grub_net_add_ipv4_local (inter, mask);
/* We do not implement dead gateway detection and the first entry SHOULD
be preferred one */
opt = find_dhcp_option (bp, size, GRUB_NET_BOOTP_ROUTER, &opt_len);
if (opt && opt_len && !(opt_len & 3))
{
grub_net_network_level_netaddress_t target;
grub_net_network_level_address_t gw;
char *rname;
target.type = GRUB_NET_NETWORK_LEVEL_PROTOCOL_IPV4;
target.ipv4.base = 0;
target.ipv4.masksize = 0;
gw.type = GRUB_NET_NETWORK_LEVEL_PROTOCOL_IPV4;
gw.ipv4 = grub_get_unaligned32 (opt);
rname = grub_xasprintf ("%s:default", name);
if (rname)
grub_net_add_route_gw (rname, target, gw, 0);
grub_free (rname);
}
opt = find_dhcp_option (bp, size, GRUB_NET_BOOTP_DNS, &opt_len);
if (opt && opt_len && !(opt_len & 3))
{
int i;
for (i = 0; i < opt_len / 4; i++)
{
struct grub_net_network_level_address s;
s.type = GRUB_NET_NETWORK_LEVEL_PROTOCOL_IPV4;
s.ipv4 = grub_get_unaligned32 (opt);
s.option = DNS_OPTION_PREFER_IPV4;
grub_net_add_dns_server (&s);
opt += 4;
}
}
opt = find_dhcp_option (bp, size, GRUB_NET_BOOTP_HOSTNAME, &opt_len);
if (opt && opt_len)
grub_env_set_net_property (name, "hostname", (const char *) opt, opt_len);
opt = find_dhcp_option (bp, size, GRUB_NET_BOOTP_DOMAIN, &opt_len);
if (opt && opt_len)
grub_env_set_net_property (name, "domain", (const char *) opt, opt_len);
opt = find_dhcp_option (bp, size, GRUB_NET_BOOTP_ROOT_PATH, &opt_len);
if (opt && opt_len)
grub_env_set_net_property (name, "rootpath", (const char *) opt, opt_len);
opt = find_dhcp_option (bp, size, GRUB_NET_BOOTP_EXTENSIONS_PATH, &opt_len);
if (opt && opt_len)
grub_env_set_net_property (name, "extensionspath", (const char *) opt, opt_len);
inter->dhcp_ack = grub_malloc (size);
if (inter->dhcp_ack)
{
grub_memcpy (inter->dhcp_ack, bp, size);
inter->dhcp_acklen = size;
}
else
grub_errno = GRUB_ERR_NONE;
return inter;
}
void
grub_net_process_dhcp (struct grub_net_buff *nb,
struct grub_net_card *card)
{
char *name;
struct grub_net_network_level_interface *inf;
name = grub_xasprintf ("%s:dhcp", card->name);
if (!name)
{
grub_print_error ();
return;
}
grub_net_configure_by_dhcp_ack (name, card,
0, (const struct grub_net_bootp_packet *) nb->data,
(nb->tail - nb->data), 0, 0, 0);
grub_free (name);
if (grub_errno)
grub_print_error ();
else
{
FOR_NET_NETWORK_LEVEL_INTERFACES(inf)
if (grub_memcmp (inf->name, card->name, grub_strlen (card->name)) == 0
&& grub_memcmp (inf->name + grub_strlen (card->name),
":dhcp_tmp", sizeof (":dhcp_tmp") - 1) == 0)
{
grub_net_network_level_interface_unregister (inf);
break;
}
}
}
static char
hexdigit (grub_uint8_t val)
{
if (val < 10)
return val + '0';
return val + 'a' - 10;
}
static grub_err_t
grub_cmd_dhcpopt (struct grub_command *cmd __attribute__ ((unused)),
int argc, char **args)
{
struct grub_net_network_level_interface *inter;
unsigned num;
const grub_uint8_t *ptr;
grub_uint8_t taglength;
if (argc < 4)
return grub_error (GRUB_ERR_BAD_ARGUMENT,
N_("four arguments expected"));
FOR_NET_NETWORK_LEVEL_INTERFACES (inter)
if (grub_strcmp (inter->name, args[1]) == 0)
break;
if (!inter)
return grub_error (GRUB_ERR_BAD_ARGUMENT,
N_("unrecognised network interface `%s'"), args[1]);
if (!inter->dhcp_ack)
return grub_error (GRUB_ERR_IO, N_("no DHCP info found"));
ptr = inter->dhcp_ack->vendor;
/* This duplicates check in find_dhcp_option to preserve previous error return */
if (inter->dhcp_acklen < OFFSET_OF (vendor, inter->dhcp_ack) + sizeof (grub_uint32_t)
|| ptr[0] != GRUB_NET_BOOTP_RFC1048_MAGIC_0
|| ptr[1] != GRUB_NET_BOOTP_RFC1048_MAGIC_1
|| ptr[2] != GRUB_NET_BOOTP_RFC1048_MAGIC_2
|| ptr[3] != GRUB_NET_BOOTP_RFC1048_MAGIC_3)
return grub_error (GRUB_ERR_IO, N_("no DHCP options found"));
num = grub_strtoul (args[2], 0, 0);
if (grub_errno)
return grub_errno;
/* Exclude PAD (0) and END (255) option codes */
if (num == 0 || num > 254)
return grub_error (GRUB_ERR_BAD_ARGUMENT, N_("invalid DHCP option code"));
ptr = find_dhcp_option (inter->dhcp_ack, inter->dhcp_acklen, num, &taglength);
if (!ptr)
return grub_error (GRUB_ERR_IO, N_("no DHCP option %u found"), num);
if (grub_strcmp (args[3], "string") == 0)
{
grub_err_t err = GRUB_ERR_NONE;
char *val = grub_malloc (taglength + 1);
if (!val)
return grub_errno;
grub_memcpy (val, ptr, taglength);
val[taglength] = 0;
if (args[0][0] == '-' && args[0][1] == 0)
grub_printf ("%s\n", val);
else
err = grub_env_set (args[0], val);
grub_free (val);
return err;
}
if (grub_strcmp (args[3], "number") == 0)
{
grub_uint64_t val = 0;
int i;
for (i = 0; i < taglength; i++)
val = (val << 8) | ptr[i];
if (args[0][0] == '-' && args[0][1] == 0)
grub_printf ("%llu\n", (unsigned long long) val);
else
{
char valn[64];
grub_snprintf (valn, sizeof (valn), "%lld\n", (unsigned long long) val);
return grub_env_set (args[0], valn);
}
return GRUB_ERR_NONE;
}
if (grub_strcmp (args[3], "hex") == 0)
{
grub_err_t err = GRUB_ERR_NONE;
char *val = grub_malloc (2 * taglength + 1);
int i;
if (!val)
return grub_errno;
for (i = 0; i < taglength; i++)
{
val[2 * i] = hexdigit (ptr[i] >> 4);
val[2 * i + 1] = hexdigit (ptr[i] & 0xf);
}
val[2 * taglength] = 0;
if (args[0][0] == '-' && args[0][1] == 0)
grub_printf ("%s\n", val);
else
err = grub_env_set (args[0], val);
grub_free (val);
return err;
}
return grub_error (GRUB_ERR_BAD_ARGUMENT,
N_("unrecognised DHCP option format specification `%s'"),
args[3]);
}
/* FIXME: allow to specify mac address. */
static grub_err_t
grub_cmd_bootp (struct grub_command *cmd __attribute__ ((unused)),
int argc, char **args)
{
struct grub_net_card *card;
struct grub_net_network_level_interface *ifaces;
grub_size_t ncards = 0;
unsigned j = 0;
int interval;
grub_err_t err;
FOR_NET_CARDS (card)
{
if (argc > 0 && grub_strcmp (card->name, args[0]) != 0)
continue;
ncards++;
}
if (ncards == 0)
return grub_error (GRUB_ERR_NET_NO_CARD, N_("no network card found"));
ifaces = grub_zalloc (ncards * sizeof (ifaces[0]));
if (!ifaces)
return grub_errno;
j = 0;
FOR_NET_CARDS (card)
{
if (argc > 0 && grub_strcmp (card->name, args[0]) != 0)
continue;
ifaces[j].card = card;
ifaces[j].next = &ifaces[j+1];
if (j)
ifaces[j].prev = &ifaces[j-1].next;
ifaces[j].name = grub_xasprintf ("%s:dhcp_tmp", card->name);
card->num_ifaces++;
if (!ifaces[j].name)
{
unsigned i;
for (i = 0; i < j; i++)
grub_free (ifaces[i].name);
grub_free (ifaces);
return grub_errno;
}
ifaces[j].address.type = GRUB_NET_NETWORK_LEVEL_PROTOCOL_DHCP_RECV;
grub_memcpy (&ifaces[j].hwaddress, &card->default_address,
sizeof (ifaces[j].hwaddress));
j++;
}
ifaces[ncards - 1].next = grub_net_network_level_interfaces;
if (grub_net_network_level_interfaces)
grub_net_network_level_interfaces->prev = & ifaces[ncards - 1].next;
grub_net_network_level_interfaces = &ifaces[0];
ifaces[0].prev = &grub_net_network_level_interfaces;
for (interval = 200; interval < 10000; interval *= 2)
{
int done = 0;
for (j = 0; j < ncards; j++)
{
struct grub_net_bootp_packet *pack;
struct grub_datetime date;
grub_int32_t t = 0;
struct grub_net_buff *nb;
struct udphdr *udph;
grub_net_network_level_address_t target;
grub_net_link_level_address_t ll_target;
grub_uint8_t *offset;
if (!ifaces[j].prev)
continue;
nb = grub_netbuff_alloc (sizeof (*pack) + sizeof(dhcp_option_header)
+ sizeof(grub_userclass)
+ sizeof(grub_dhcpdiscover)
+ sizeof(grub_dhcptime) + 64 + 128);
if (!nb)
{
grub_netbuff_free (nb);
return grub_errno;
}
err = grub_netbuff_reserve (nb, sizeof (*pack) + 64 + 128);
if (err)
{
grub_netbuff_free (nb);
return err;
}
err = grub_netbuff_push (nb, sizeof (*pack) + 64);
if (err)
{
grub_netbuff_free (nb);
return err;
}
pack = (void *) nb->data;
done = 1;
grub_memset (pack, 0, sizeof (*pack) + 64);
pack->opcode = 1;
pack->hw_type = 1;
pack->hw_len = 6;
err = grub_get_datetime (&date);
if (err || !grub_datetime2unixtime (&date, &t))
{
grub_errno = GRUB_ERR_NONE;
t = 0;
}
pack->ident = grub_cpu_to_be32 (t);
pack->seconds = grub_cpu_to_be16 (t);
grub_memcpy (&pack->mac_addr, &ifaces[j].hwaddress.mac, 6);
offset = (grub_uint8_t *)&pack->vendor;
grub_memcpy (offset, dhcp_option_header, sizeof(dhcp_option_header));
offset += sizeof(dhcp_option_header);
grub_memcpy (offset, grub_dhcpdiscover, sizeof(grub_dhcpdiscover));
offset += sizeof(grub_dhcpdiscover);
grub_memcpy (offset, grub_userclass, sizeof(grub_userclass));
offset += sizeof(grub_userclass);
grub_memcpy (offset, grub_dhcptime, sizeof(grub_dhcptime));
/* insert Client System Architecture (option 93) */
offset += sizeof(grub_dhcptime);
offset[0] = 93;
offset[1] = 2;
offset[2] = (GRUB_NET_BOOTP_ARCH >> 8);
offset[3] = (GRUB_NET_BOOTP_ARCH & 0xFF);
/* option terminator */
offset[4] = 255;
grub_netbuff_push (nb, sizeof (*udph));
udph = (struct udphdr *) nb->data;
udph->src = grub_cpu_to_be16_compile_time (68);
udph->dst = grub_cpu_to_be16_compile_time (67);
udph->chksum = 0;
udph->len = grub_cpu_to_be16 (nb->tail - nb->data);
target.type = GRUB_NET_NETWORK_LEVEL_PROTOCOL_IPV4;
target.ipv4 = 0xffffffff;
err = grub_net_link_layer_resolve (&ifaces[j], &target, &ll_target);
if (err)
return err;
udph->chksum = grub_net_ip_transport_checksum (nb, GRUB_NET_IP_UDP,
&ifaces[j].address,
&target);
err = grub_net_send_ip_packet (&ifaces[j], &target, &ll_target, nb,
GRUB_NET_IP_UDP);
grub_netbuff_free (nb);
if (err)
return err;
}
if (!done)
break;
grub_net_poll_cards (interval, 0);
}
err = GRUB_ERR_NONE;
for (j = 0; j < ncards; j++)
{
grub_free (ifaces[j].name);
if (!ifaces[j].prev)
continue;
grub_error_push ();
grub_net_network_level_interface_unregister (&ifaces[j]);
err = grub_error (GRUB_ERR_FILE_NOT_FOUND,
N_("couldn't autoconfigure %s"),
ifaces[j].card->name);
}
grub_free (ifaces);
return err;
}
static grub_command_t cmd_getdhcp, cmd_bootp;
void
grub_bootp_init (void)
{
cmd_bootp = grub_register_command ("net_bootp", grub_cmd_bootp,
N_("[CARD]"),
N_("perform a bootp autoconfiguration"));
cmd_getdhcp = grub_register_command ("net_get_dhcp_option", grub_cmd_dhcpopt,
N_("VAR INTERFACE NUMBER DESCRIPTION"),
N_("retrieve DHCP option and save it into VAR. If VAR is - then print the value."));
}
void
grub_bootp_fini (void)
{
grub_unregister_command (cmd_getdhcp);
grub_unregister_command (cmd_bootp);
}
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