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grub/grub-core/net/dns.c
Andrei Borzenkov a01ab69848 net: avoid closing NULL socket in DNS lookup 
Refactor code so that we do not store NULL pointers in array
of in-flight DNS servers.

Reported-By: Josef Bacik <jbacik@fb.com>
2015-10-12 23:16:23 +03:00

770 lines
19 KiB
C
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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/net/udp.h>
#include <grub/command.h>
#include <grub/i18n.h>
#include <grub/err.h>
#include <grub/time.h>
struct dns_cache_element
{
char *name;
grub_size_t naddresses;
struct grub_net_network_level_address *addresses;
grub_uint64_t limit_time;
};
#define DNS_CACHE_SIZE 1021
#define DNS_HASH_BASE 423
typedef enum grub_dns_qtype_id
{
GRUB_DNS_QTYPE_A = 1,
GRUB_DNS_QTYPE_AAAA = 28
} grub_dns_qtype_id_t;
static struct dns_cache_element dns_cache[DNS_CACHE_SIZE];
static struct grub_net_network_level_address *dns_servers;
static grub_size_t dns_nservers, dns_servers_alloc;
grub_err_t
grub_net_add_dns_server (const struct grub_net_network_level_address *s)
{
if (dns_servers_alloc <= dns_nservers)
{
int na = dns_servers_alloc * 2;
struct grub_net_network_level_address *ns;
if (na < 8)
na = 8;
ns = grub_realloc (dns_servers, na * sizeof (ns[0]));
if (!ns)
return grub_errno;
dns_servers_alloc = na;
dns_servers = ns;
}
dns_servers[dns_nservers++] = *s;
return GRUB_ERR_NONE;
}
void
grub_net_remove_dns_server (const struct grub_net_network_level_address *s)
{
grub_size_t i;
for (i = 0; i < dns_nservers; i++)
if (grub_net_addr_cmp (s, &dns_servers[i]) == 0)
break;
if (i < dns_nservers)
{
dns_servers[i] = dns_servers[dns_nservers - 1];
dns_nservers--;
}
}
struct dns_header
{
grub_uint16_t id;
grub_uint8_t flags;
grub_uint8_t ra_z_r_code;
grub_uint16_t qdcount;
grub_uint16_t ancount;
grub_uint16_t nscount;
grub_uint16_t arcount;
} GRUB_PACKED;
enum
{
FLAGS_RESPONSE = 0x80,
FLAGS_OPCODE = 0x78,
FLAGS_RD = 0x01
};
enum
{
ERRCODE_MASK = 0x0f
};
enum
{
DNS_PORT = 53
};
struct recv_data
{
grub_size_t *naddresses;
struct grub_net_network_level_address **addresses;
int cache;
grub_uint16_t id;
int dns_err;
char *name;
const char *oname;
int stop;
};
static inline int
hash (const char *str)
{
unsigned v = 0, xn = 1;
const char *ptr;
for (ptr = str; *ptr; )
{
v = (v + xn * *ptr);
xn = (DNS_HASH_BASE * xn) % DNS_CACHE_SIZE;
ptr++;
if (((ptr - str) & 0x3ff) == 0)
v %= DNS_CACHE_SIZE;
}
return v % DNS_CACHE_SIZE;
}
static int
check_name_real (const grub_uint8_t *name_at, const grub_uint8_t *head,
const grub_uint8_t *tail, const char *check_with,
int *length, char *set)
{
const char *readable_ptr = check_with;
const grub_uint8_t *ptr;
char *optr = set;
int bytes_processed = 0;
if (length)
*length = 0;
for (ptr = name_at; ptr < tail && bytes_processed < tail - head + 2; )
{
/* End marker. */
if (!*ptr)
{
if (length && *length)
(*length)--;
if (optr && optr != set)
optr--;
if (optr)
*optr = 0;
return !readable_ptr || (*readable_ptr == 0);
}
if (*ptr & 0xc0)
{
bytes_processed += 2;
if (ptr + 1 >= tail)
return 0;
ptr = head + (((ptr[0] & 0x3f) << 8) | ptr[1]);
continue;
}
if (readable_ptr && grub_memcmp (ptr + 1, readable_ptr, *ptr) != 0)
return 0;
if (grub_memchr (ptr + 1, 0, *ptr)
|| grub_memchr (ptr + 1, '.', *ptr))
return 0;
if (readable_ptr)
readable_ptr += *ptr;
if (readable_ptr && *readable_ptr != '.' && *readable_ptr != 0)
return 0;
bytes_processed += *ptr + 1;
if (length)
*length += *ptr + 1;
if (optr)
{
grub_memcpy (optr, ptr + 1, *ptr);
optr += *ptr;
}
if (optr)
*optr++ = '.';
if (readable_ptr && *readable_ptr)
readable_ptr++;
ptr += *ptr + 1;
}
return 0;
}
static int
check_name (const grub_uint8_t *name_at, const grub_uint8_t *head,
const grub_uint8_t *tail, const char *check_with)
{
return check_name_real (name_at, head, tail, check_with, NULL, NULL);
}
static char *
get_name (const grub_uint8_t *name_at, const grub_uint8_t *head,
const grub_uint8_t *tail)
{
int length;
char *ret;
if (!check_name_real (name_at, head, tail, NULL, &length, NULL))
return NULL;
ret = grub_malloc (length + 1);
if (!ret)
return NULL;
if (!check_name_real (name_at, head, tail, NULL, NULL, ret))
{
grub_free (ret);
return NULL;
}
return ret;
}
enum
{
DNS_CLASS_A = 1,
DNS_CLASS_CNAME = 5,
DNS_CLASS_AAAA = 28
};
static grub_err_t
recv_hook (grub_net_udp_socket_t sock __attribute__ ((unused)),
struct grub_net_buff *nb,
void *data_)
{
struct dns_header *head;
struct recv_data *data = data_;
int i, j;
grub_uint8_t *ptr, *reparse_ptr;
int redirect_cnt = 0;
char *redirect_save = NULL;
grub_uint32_t ttl_all = ~0U;
head = (struct dns_header *) nb->data;
ptr = (grub_uint8_t *) (head + 1);
if (ptr >= nb->tail)
{
grub_netbuff_free (nb);
return GRUB_ERR_NONE;
}
if (head->id != data->id)
{
grub_netbuff_free (nb);
return GRUB_ERR_NONE;
}
if (!(head->flags & FLAGS_RESPONSE) || (head->flags & FLAGS_OPCODE))
{
grub_netbuff_free (nb);
return GRUB_ERR_NONE;
}
if (head->ra_z_r_code & ERRCODE_MASK)
{
data->dns_err = 1;
grub_netbuff_free (nb);
return GRUB_ERR_NONE;
}
for (i = 0; i < grub_be_to_cpu16 (head->qdcount); i++)
{
if (ptr >= nb->tail)
{
grub_netbuff_free (nb);
return GRUB_ERR_NONE;
}
while (ptr < nb->tail && !((*ptr & 0xc0) || *ptr == 0))
ptr += *ptr + 1;
if (ptr < nb->tail && (*ptr & 0xc0))
ptr++;
ptr++;
ptr += 4;
}
*data->addresses = grub_malloc (sizeof ((*data->addresses)[0])
* grub_be_to_cpu16 (head->ancount));
if (!*data->addresses)
{
grub_errno = GRUB_ERR_NONE;
grub_netbuff_free (nb);
return GRUB_ERR_NONE;
}
reparse_ptr = ptr;
reparse:
for (i = 0, ptr = reparse_ptr; i < grub_be_to_cpu16 (head->ancount); i++)
{
int ignored = 0;
grub_uint8_t class;
grub_uint32_t ttl = 0;
grub_uint16_t length;
if (ptr >= nb->tail)
{
if (!*data->naddresses)
grub_free (*data->addresses);
return GRUB_ERR_NONE;
}
ignored = !check_name (ptr, nb->data, nb->tail, data->name);
while (ptr < nb->tail && !((*ptr & 0xc0) || *ptr == 0))
ptr += *ptr + 1;
if (ptr < nb->tail && (*ptr & 0xc0))
ptr++;
ptr++;
if (ptr + 10 >= nb->tail)
{
if (!*data->naddresses)
grub_free (*data->addresses);
grub_netbuff_free (nb);
return GRUB_ERR_NONE;
}
if (*ptr++ != 0)
ignored = 1;
class = *ptr++;
if (*ptr++ != 0)
ignored = 1;
if (*ptr++ != 1)
ignored = 1;
for (j = 0; j < 4; j++)
{
ttl <<= 8;
ttl |= *ptr++;
}
length = *ptr++ << 8;
length |= *ptr++;
if (ptr + length > nb->tail)
{
if (!*data->naddresses)
grub_free (*data->addresses);
grub_netbuff_free (nb);
return GRUB_ERR_NONE;
}
if (!ignored)
{
if (ttl_all > ttl)
ttl_all = ttl;
switch (class)
{
case DNS_CLASS_A:
if (length != 4)
break;
(*data->addresses)[*data->naddresses].type
= GRUB_NET_NETWORK_LEVEL_PROTOCOL_IPV4;
grub_memcpy (&(*data->addresses)[*data->naddresses].ipv4,
ptr, 4);
(*data->naddresses)++;
data->stop = 1;
break;
case DNS_CLASS_AAAA:
if (length != 16)
break;
(*data->addresses)[*data->naddresses].type
= GRUB_NET_NETWORK_LEVEL_PROTOCOL_IPV6;
grub_memcpy (&(*data->addresses)[*data->naddresses].ipv6,
ptr, 16);
(*data->naddresses)++;
data->stop = 1;
break;
case DNS_CLASS_CNAME:
if (!(redirect_cnt & (redirect_cnt - 1)))
{
grub_free (redirect_save);
redirect_save = data->name;
}
else
grub_free (data->name);
redirect_cnt++;
data->name = get_name (ptr, nb->data, nb->tail);
if (!data->name)
{
data->dns_err = 1;
grub_errno = 0;
return GRUB_ERR_NONE;
}
grub_dprintf ("dns", "CNAME %s\n", data->name);
if (grub_strcmp (redirect_save, data->name) == 0)
{
data->dns_err = 1;
grub_free (redirect_save);
return GRUB_ERR_NONE;
}
goto reparse;
}
}
ptr += length;
}
if (ttl_all && *data->naddresses && data->cache)
{
int h;
grub_dprintf ("dns", "caching for %d seconds\n", ttl_all);
h = hash (data->oname);
grub_free (dns_cache[h].name);
dns_cache[h].name = 0;
grub_free (dns_cache[h].addresses);
dns_cache[h].addresses = 0;
dns_cache[h].name = grub_strdup (data->oname);
dns_cache[h].naddresses = *data->naddresses;
dns_cache[h].addresses = grub_malloc (*data->naddresses
* sizeof (dns_cache[h].addresses[0]));
dns_cache[h].limit_time = grub_get_time_ms () + 1000 * ttl_all;
if (!dns_cache[h].addresses || !dns_cache[h].name)
{
grub_free (dns_cache[h].name);
dns_cache[h].name = 0;
grub_free (dns_cache[h].addresses);
dns_cache[h].addresses = 0;
}
grub_memcpy (dns_cache[h].addresses, *data->addresses,
*data->naddresses
* sizeof (dns_cache[h].addresses[0]));
}
grub_netbuff_free (nb);
grub_free (redirect_save);
return GRUB_ERR_NONE;
}
grub_err_t
grub_net_dns_lookup (const char *name,
const struct grub_net_network_level_address *servers,
grub_size_t n_servers,
grub_size_t *naddresses,
struct grub_net_network_level_address **addresses,
int cache)
{
grub_size_t send_servers = 0;
grub_size_t i, j;
struct grub_net_buff *nb;
grub_net_udp_socket_t *sockets;
grub_uint8_t *optr;
const char *iptr;
struct dns_header *head;
static grub_uint16_t id = 1;
grub_uint8_t *qtypeptr;
grub_err_t err = GRUB_ERR_NONE;
struct recv_data data = {naddresses, addresses, cache,
grub_cpu_to_be16 (id++), 0, 0, name, 0};
grub_uint8_t *nbd;
grub_size_t try_server = 0;
if (!servers)
{
servers = dns_servers;
n_servers = dns_nservers;
}
if (!n_servers)
return grub_error (GRUB_ERR_BAD_ARGUMENT,
N_("no DNS servers configured"));
*naddresses = 0;
if (cache)
{
int h;
h = hash (name);
if (dns_cache[h].name && grub_strcmp (dns_cache[h].name, name) == 0
&& grub_get_time_ms () < dns_cache[h].limit_time)
{
grub_dprintf ("dns", "retrieved from cache\n");
*addresses = grub_malloc (dns_cache[h].naddresses
* sizeof ((*addresses)[0]));
if (!*addresses)
return grub_errno;
*naddresses = dns_cache[h].naddresses;
grub_memcpy (*addresses, dns_cache[h].addresses,
dns_cache[h].naddresses
* sizeof ((*addresses)[0]));
return GRUB_ERR_NONE;
}
}
sockets = grub_malloc (sizeof (sockets[0]) * n_servers);
if (!sockets)
return grub_errno;
data.name = grub_strdup (name);
if (!data.name)
{
grub_free (sockets);
return grub_errno;
}
nb = grub_netbuff_alloc (GRUB_NET_OUR_MAX_IP_HEADER_SIZE
+ GRUB_NET_MAX_LINK_HEADER_SIZE
+ GRUB_NET_UDP_HEADER_SIZE
+ sizeof (struct dns_header)
+ grub_strlen (name) + 2 + 4);
if (!nb)
{
grub_free (sockets);
grub_free (data.name);
return grub_errno;
}
grub_netbuff_reserve (nb, GRUB_NET_OUR_MAX_IP_HEADER_SIZE
+ GRUB_NET_MAX_LINK_HEADER_SIZE
+ GRUB_NET_UDP_HEADER_SIZE);
grub_netbuff_put (nb, sizeof (struct dns_header)
+ grub_strlen (name) + 2 + 4);
head = (struct dns_header *) nb->data;
optr = (grub_uint8_t *) (head + 1);
for (iptr = name; *iptr; )
{
const char *dot;
dot = grub_strchr (iptr, '.');
if (!dot)
dot = iptr + grub_strlen (iptr);
if ((dot - iptr) >= 64)
{
grub_free (sockets);
grub_free (data.name);
return grub_error (GRUB_ERR_BAD_ARGUMENT,
N_("domain name component is too long"));
}
*optr = (dot - iptr);
optr++;
grub_memcpy (optr, iptr, dot - iptr);
optr += dot - iptr;
iptr = dot;
if (*iptr)
iptr++;
}
*optr++ = 0;
/* Type. */
*optr++ = 0;
qtypeptr = optr++;
/* Class. */
*optr++ = 0;
*optr++ = 1;
head->id = data.id;
head->flags = FLAGS_RD;
head->ra_z_r_code = 0;
head->qdcount = grub_cpu_to_be16_compile_time (1);
head->ancount = grub_cpu_to_be16_compile_time (0);
head->nscount = grub_cpu_to_be16_compile_time (0);
head->arcount = grub_cpu_to_be16_compile_time (0);
nbd = nb->data;
for (i = 0; i < n_servers * 4; i++)
{
/* Connect to a next server. */
while (!(i & 1) && try_server < n_servers)
{
sockets[send_servers] = grub_net_udp_open (servers[try_server++],
DNS_PORT,
recv_hook,
&data);
if (!sockets[send_servers])
{
err = grub_errno;
grub_errno = GRUB_ERR_NONE;
}
else
{
send_servers++;
break;
}
}
if (!send_servers)
goto out;
if (*data.naddresses)
goto out;
for (j = 0; j < send_servers; j++)
{
grub_err_t err2;
nb->data = nbd;
grub_size_t t = 0;
do
{
if (servers[j].option == DNS_OPTION_IPV4 ||
((servers[j].option == DNS_OPTION_PREFER_IPV4) && (t++ == 0)) ||
((servers[j].option == DNS_OPTION_PREFER_IPV6) && (t++ == 1)))
*qtypeptr = GRUB_DNS_QTYPE_A;
else
*qtypeptr = GRUB_DNS_QTYPE_AAAA;
grub_dprintf ("dns", "QTYPE: %u QNAME: %s\n", *qtypeptr, name);
err2 = grub_net_send_udp_packet (sockets[j], nb);
if (err2)
{
grub_errno = GRUB_ERR_NONE;
err = err2;
}
if (*data.naddresses)
goto out;
}
while (t == 1);
}
grub_net_poll_cards (200, &data.stop);
}
out:
grub_free (data.name);
grub_netbuff_free (nb);
for (j = 0; j < send_servers; j++)
grub_net_udp_close (sockets[j]);
grub_free (sockets);
if (*data.naddresses)
return GRUB_ERR_NONE;
if (data.dns_err)
return grub_error (GRUB_ERR_NET_NO_DOMAIN,
N_("no DNS record found"));
if (err)
{
grub_errno = err;
return err;
}
return grub_error (GRUB_ERR_TIMEOUT,
N_("no DNS reply received"));
}
static grub_err_t
grub_cmd_nslookup (struct grub_command *cmd __attribute__ ((unused)),
int argc, char **args)
{
grub_err_t err;
struct grub_net_network_level_address cmd_server;
struct grub_net_network_level_address *servers;
grub_size_t nservers, i, naddresses = 0;
struct grub_net_network_level_address *addresses = 0;
if (argc != 2 && argc != 1)
return grub_error (GRUB_ERR_BAD_ARGUMENT, N_("two arguments expected"));
if (argc == 2)
{
err = grub_net_resolve_address (args[1], &cmd_server);
if (err)
return err;
servers = &cmd_server;
nservers = 1;
}
else
{
servers = dns_servers;
nservers = dns_nservers;
}
grub_net_dns_lookup (args[0], servers, nservers, &naddresses,
&addresses, 0);
for (i = 0; i < naddresses; i++)
{
char buf[GRUB_NET_MAX_STR_ADDR_LEN];
grub_net_addr_to_str (&addresses[i], buf);
grub_printf ("%s\n", buf);
}
grub_free (addresses);
if (naddresses)
return GRUB_ERR_NONE;
return grub_error (GRUB_ERR_NET_NO_DOMAIN, N_("no DNS record found"));
}
static grub_err_t
grub_cmd_list_dns (struct grub_command *cmd __attribute__ ((unused)),
int argc __attribute__ ((unused)),
char **args __attribute__ ((unused)))
{
grub_size_t i;
const char *strtype = "";
for (i = 0; i < dns_nservers; i++)
{
switch (dns_servers[i].option)
{
case DNS_OPTION_IPV4:
strtype = _("only ipv4");
break;
case DNS_OPTION_IPV6:
strtype = _("only ipv6");
break;
case DNS_OPTION_PREFER_IPV4:
strtype = _("prefer ipv4");
break;
case DNS_OPTION_PREFER_IPV6:
strtype = _("prefer ipv6");
break;
}
char buf[GRUB_NET_MAX_STR_ADDR_LEN];
grub_net_addr_to_str (&dns_servers[i], buf);
grub_printf ("%s (%s)\n", buf, strtype);
}
return GRUB_ERR_NONE;
}
static grub_err_t
grub_cmd_add_dns (struct grub_command *cmd __attribute__ ((unused)),
int argc, char **args)
{
grub_err_t err;
struct grub_net_network_level_address server;
if ((argc < 1) || (argc > 2))
return grub_error (GRUB_ERR_BAD_ARGUMENT, N_("one argument expected"));
else if (argc == 1)
server.option = DNS_OPTION_PREFER_IPV4;
else
{
if (grub_strcmp (args[1], "--only-ipv4") == 0)
server.option = DNS_OPTION_IPV4;
else if (grub_strcmp (args[1], "--only-ipv6") == 0)
server.option = DNS_OPTION_IPV6;
else if (grub_strcmp (args[1], "--prefer-ipv4") == 0)
server.option = DNS_OPTION_PREFER_IPV4;
else if (grub_strcmp (args[1], "--prefer-ipv6") == 0)
server.option = DNS_OPTION_PREFER_IPV6;
else
return grub_error (GRUB_ERR_BAD_ARGUMENT, N_("invalid argument"));
}
err = grub_net_resolve_address (args[0], &server);
if (err)
return err;
return grub_net_add_dns_server (&server);
}
static grub_err_t
grub_cmd_del_dns (struct grub_command *cmd __attribute__ ((unused)),
int argc, char **args)
{
grub_err_t err;
struct grub_net_network_level_address server;
if (argc != 1)
return grub_error (GRUB_ERR_BAD_ARGUMENT, N_("one argument expected"));
err = grub_net_resolve_address (args[1], &server);
if (err)
return err;
return grub_net_add_dns_server (&server);
}
static grub_command_t cmd, cmd_add, cmd_del, cmd_list;
void
grub_dns_init (void)
{
cmd = grub_register_command ("net_nslookup", grub_cmd_nslookup,
N_("ADDRESS DNSSERVER"),
N_("Perform a DNS lookup"));
cmd_add = grub_register_command ("net_add_dns", grub_cmd_add_dns,
N_("DNSSERVER"),
N_("Add a DNS server"));
cmd_del = grub_register_command ("net_del_dns", grub_cmd_del_dns,
N_("DNSSERVER"),
N_("Remove a DNS server"));
cmd_list = grub_register_command ("net_ls_dns", grub_cmd_list_dns,
NULL, N_("List DNS servers"));
}
void
grub_dns_fini (void)
{
grub_unregister_command (cmd);
grub_unregister_command (cmd_add);
grub_unregister_command (cmd_del);
grub_unregister_command (cmd_list);
}
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