tor

resolve.c (14099B)

---

/* Copyright (c) 2003-2004, Roger Dingledine
* Copyright (c) 2004-2006, Roger Dingledine, Nick Mathewson.
* Copyright (c) 2007-2021, The Tor Project, Inc. */
/* See LICENSE for licensing information */

/**
* \file resolve.c
* \brief Use the libc DNS resolver to convert hostnames into addresses.
**/

#define RESOLVE_PRIVATE
#include "lib/net/resolve.h"

#include "lib/net/address.h"
#include "lib/net/inaddr.h"
#include "lib/malloc/malloc.h"
#include "lib/string/parse_int.h"
#include "lib/string/util_string.h"

#include "ext/siphash.h"
#include "ext/ht.h"

#ifdef HAVE_SYS_TYPES_H
#include <sys/types.h>
#endif
#ifdef HAVE_SYS_SOCKET_H
#include <sys/socket.h>
#endif
#ifdef HAVE_NETDB_H
#include <netdb.h>
#endif

#include <string.h>

/** Similar behavior to Unix gethostbyname: resolve <b>name</b>, and set
* *<b>addr</b> to the proper IP address, in host byte order.  Returns 0
* on success, -1 on failure; 1 on transient failure.
*
* This function only accepts IPv4 addresses.
*
* (This function exists because standard windows gethostbyname
* doesn't treat raw IP addresses properly.)
*/

MOCK_IMPL(int,
tor_lookup_hostname,(const char *name, uint32_t *addr))
{
 tor_addr_t myaddr;
 int ret;

 if (BUG(!addr))
   return -1;

 *addr = 0;

 if ((ret = tor_addr_lookup(name, AF_INET, &myaddr)))
   return ret;

 if (tor_addr_family(&myaddr) == AF_INET) {
   *addr = tor_addr_to_ipv4h(&myaddr);
   return ret;
 }

 return -1;
}

#ifdef HAVE_GETADDRINFO

/* Host lookup helper for tor_addr_lookup(), when getaddrinfo() is
* available on this system.
*
* See tor_addr_lookup() for details.
*/
MOCK_IMPL(STATIC int,
tor_addr_lookup_host_impl,(const char *name,
                         uint16_t family,
                         tor_addr_t *addr))
{
 int err;
 struct addrinfo *res=NULL, *res_p;
 struct addrinfo *best=NULL;
 struct addrinfo hints;
 int result = -1;
 memset(&hints, 0, sizeof(hints));
 hints.ai_family = family;
 hints.ai_socktype = SOCK_STREAM;
 err = tor_getaddrinfo(name, NULL, &hints, &res);
 /* The check for 'res' here shouldn't be necessary, but it makes static
  * analysis tools happy. */
 if (!err && res) {
   best = NULL;
   for (res_p = res; res_p; res_p = res_p->ai_next) {
     if (family == AF_UNSPEC) {
       if (res_p->ai_family == AF_INET) {
         best = res_p;
         break;
       } else if (res_p->ai_family == AF_INET6 && !best) {
         best = res_p;
       }
     } else if (family == res_p->ai_family) {
       best = res_p;
       break;
     }
   }
   if (!best)
     best = res;
   if (best->ai_family == AF_INET) {
     tor_addr_from_in(addr,
                      &((struct sockaddr_in*)best->ai_addr)->sin_addr);
     result = 0;
   } else if (best->ai_family == AF_INET6) {
     tor_addr_from_in6(addr,
                       &((struct sockaddr_in6*)best->ai_addr)->sin6_addr);
     result = 0;
   }
   tor_freeaddrinfo(res);
   return result;
 }
 return (err == EAI_AGAIN) ? 1 : -1;
}

#else /* !defined(HAVE_GETADDRINFO) */

/* Host lookup helper for tor_addr_lookup(), which calls gethostbyname().
* Used when getaddrinfo() is not available on this system.
*
* See tor_addr_lookup() for details.
*/
MOCK_IMPL(STATIC int,
tor_addr_lookup_host_impl,(const char *name,
                         uint16_t family,
                          tor_addr_t *addr))
{
 (void) family;
 struct hostent *ent;
 int err;
#ifdef HAVE_GETHOSTBYNAME_R_6_ARG
 char buf[2048];
 struct hostent hostent;
 int r;
 r = gethostbyname_r(name, &hostent, buf, sizeof(buf), &ent, &err);
#elif defined(HAVE_GETHOSTBYNAME_R_5_ARG)
 char buf[2048];
 struct hostent hostent;
 ent = gethostbyname_r(name, &hostent, buf, sizeof(buf), &err);
#elif defined(HAVE_GETHOSTBYNAME_R_3_ARG)
 struct hostent_data data;
 struct hostent hent;
 memset(&data, 0, sizeof(data));
 err = gethostbyname_r(name, &hent, &data);
 ent = err ? NULL : &hent;
#else
 ent = gethostbyname(name);
#ifdef _WIN32
 err = WSAGetLastError();
#else
 err = h_errno;
#endif /* defined(_WIN32) */
#endif /* defined(HAVE_GETHOSTBYNAME_R_6_ARG) || ... */
 if (ent) {
   if (ent->h_addrtype == AF_INET) {
     tor_addr_from_in(addr, (struct in_addr*) ent->h_addr);
   } else if (ent->h_addrtype == AF_INET6) {
     tor_addr_from_in6(addr, (struct in6_addr*) ent->h_addr);
   } else {
     tor_assert(0); // LCOV_EXCL_LINE: gethostbyname() returned bizarre type
   }
   return 0;
 }
#ifdef _WIN32
 return (err == WSATRY_AGAIN) ? 1 : -1;
#else
 return (err == TRY_AGAIN) ? 1 : -1;
#endif
}
#endif /* defined(HAVE_GETADDRINFO) */

/** Similar behavior to Unix gethostbyname: resolve <b>name</b>, and set
* *<b>addr</b> to the proper IP address and family. The <b>family</b>
* argument (which must be AF_INET, AF_INET6, or AF_UNSPEC) declares a
* <i>preferred</i> family, though another one may be returned if only one
* family is implemented for this address.
*
* Like tor_addr_parse(), this function accepts IPv6 addresses with or without
* square brackets.
*
* Return 0 on success, -1 on failure; 1 on transient failure.
*/
MOCK_IMPL(int,
tor_addr_lookup,(const char *name, uint16_t family, tor_addr_t *addr))
{
 /* Perhaps eventually this should be replaced by a tor_getaddrinfo or
  * something.
  */
 int parsed_family = 0;
 int result = -1;

 tor_assert(name);
 tor_assert(addr);
 tor_assert(family == AF_INET || family == AF_INET6 || family == AF_UNSPEC);

 if (!*name) {
   /* Empty address is an error. */
   goto permfail;
 }

 /* Is it an IP address? */
 parsed_family = tor_addr_parse(addr, name);

 if (parsed_family >= 0) {
   /* If the IP address family matches, or was unspecified */
   if (parsed_family == family || family == AF_UNSPEC) {
     goto success;
   } else {
     goto permfail;
   }
 } else {
   /* Clear the address after a failed tor_addr_parse(). */
   memset(addr, 0, sizeof(tor_addr_t));
   result = tor_addr_lookup_host_impl(name, family, addr);
   goto done;
 }

/* If we weren't successful, and haven't already set the result,
 * assume it's a permanent failure */
permfail:
 result = -1;
 goto done;
success:
 result = 0;

/* We have set the result, now it's time to clean up */
done:
 if (result) {
   /* Clear the address on error */
   memset(addr, 0, sizeof(tor_addr_t));
 }
 return result;
}

/** Parse an address or address-port combination from <b>s</b>, resolve the
* address as needed, and put the result in <b>addr_out</b> and (optionally)
* <b>port_out</b>.
*
* Like tor_addr_port_parse(), this function accepts:
*  - IPv6 address and port, when the IPv6 address is in square brackets,
*  - IPv6 address with square brackets,
*  - IPv6 address without square brackets.
*
* Return 0 on success, negative on failure. */
int
tor_addr_port_lookup(const char *s, tor_addr_t *addr_out, uint16_t *port_out)
{
 tor_addr_t addr;
 uint16_t portval = 0;
 char *tmp = NULL;
 int rv = 0;
 int result;

 tor_assert(s);
 tor_assert(addr_out);

 s = eat_whitespace(s);

 /* Try parsing s as an address:port first, so we don't have to duplicate
  * the logic that rejects IPv6:Port with no square brackets. */
 rv = tor_addr_port_parse(LOG_WARN, s, &addr, &portval, 0);
 /* That was easy, no DNS required. */
 if (rv == 0)
   goto success;

 /* Now let's check for malformed IPv6 addresses and ports:
  * tor_addr_port_parse() requires squared brackes if there is a port,
  * and we want tor_addr_port_lookup() to have the same requirement.
  * But we strip the port using tor_addr_port_split(), so tor_addr_lookup()
  * only sees the address, and will accept it without square brackets. */
 int family = tor_addr_parse(&addr, s);
 /* If tor_addr_parse() succeeds where tor_addr_port_parse() failed, we need
  * to reject this address as malformed. */
 if (family >= 0) {
   /* Double-check it's an IPv6 address. If not, we have a parsing bug.
    */
   tor_assertf_nonfatal(family == AF_INET6,
                        "Wrong family: %d (should be IPv6: %d) which "
                        "failed IP:port parsing, but passed IP parsing. "
                        "input string: '%s'; parsed address: '%s'.",
                        family, AF_INET6, s, fmt_addr(&addr));
   goto err;
 }

 /* Now we have a hostname. Let's split off the port, if any. */
 rv = tor_addr_port_split(LOG_WARN, s, &tmp, &portval);
 if (rv < 0)
   goto err;

 /* And feed the hostname to the lookup function. */
 if (tor_addr_lookup(tmp, AF_UNSPEC, &addr) != 0)
   goto err;

success:
 if (port_out)
   *port_out = portval;
 tor_addr_copy(addr_out, &addr);
 result = 0;
 goto done;

err:
 /* Clear the address and port on error */
 memset(addr_out, 0, sizeof(tor_addr_t));
 if (port_out)
   *port_out = 0;
 result = -1;

/* We have set the result, now it's time to clean up */
done:
 tor_free(tmp);
 return result;
}

#ifdef USE_SANDBOX_GETADDRINFO
/** True if we should only return cached values */
static int sandbox_getaddrinfo_is_active = 0;

/** Cache entry for getaddrinfo results; used when sandboxing is implemented
* so that we can consult the cache when the sandbox prevents us from doing
* getaddrinfo.
*
* We support only a limited range of getaddrinfo calls, where servname is null
* and hints contains only socktype=SOCK_STREAM, family in INET,INET6,UNSPEC.
*/
typedef struct cached_getaddrinfo_item_t {
 HT_ENTRY(cached_getaddrinfo_item_t) node;
 char *name;
 int family;
 /** set if no error; otherwise NULL */
 struct addrinfo *res;
 /** 0 for no error; otherwise an EAI_* value */
 int err;
} cached_getaddrinfo_item_t;

static unsigned
cached_getaddrinfo_item_hash(const cached_getaddrinfo_item_t *item)
{
 return (unsigned)siphash24g(item->name, strlen(item->name)) + item->family;
}

static unsigned
cached_getaddrinfo_items_eq(const cached_getaddrinfo_item_t *a,
                           const cached_getaddrinfo_item_t *b)
{
 return (a->family == b->family) && 0 == strcmp(a->name, b->name);
}

#define cached_getaddrinfo_item_free(item)              \
 FREE_AND_NULL(cached_getaddrinfo_item_t,              \
               cached_getaddrinfo_item_free_, (item))

static void
cached_getaddrinfo_item_free_(cached_getaddrinfo_item_t *item)
{
 if (item == NULL)
   return;

 tor_free(item->name);
 if (item->res)
   freeaddrinfo(item->res);
 tor_free(item);
}

static HT_HEAD(getaddrinfo_cache, cached_getaddrinfo_item_t)
    getaddrinfo_cache = HT_INITIALIZER();

HT_PROTOTYPE(getaddrinfo_cache, cached_getaddrinfo_item_t, node,
            cached_getaddrinfo_item_hash,
            cached_getaddrinfo_items_eq);
HT_GENERATE2(getaddrinfo_cache, cached_getaddrinfo_item_t, node,
            cached_getaddrinfo_item_hash,
            cached_getaddrinfo_items_eq,
            0.6, tor_reallocarray_, tor_free_);

/** If true, don't try to cache getaddrinfo results. */
static int sandbox_getaddrinfo_cache_disabled = 0;

/** Tell the sandbox layer not to try to cache getaddrinfo results. Used as in
* tor-resolve, when we have no intention of initializing crypto or of
* installing the sandbox.*/
void
sandbox_disable_getaddrinfo_cache(void)
{
 sandbox_getaddrinfo_cache_disabled = 1;
}

void
tor_freeaddrinfo(struct addrinfo *ai)
{
 if (sandbox_getaddrinfo_cache_disabled)
   freeaddrinfo(ai);
}

int
tor_getaddrinfo(const char *name, const char *servname,
               const struct addrinfo *hints,
               struct addrinfo **res)
{
 int err;
 struct cached_getaddrinfo_item_t search, *item;

 if (sandbox_getaddrinfo_cache_disabled) {
   return getaddrinfo(name, NULL, hints, res);
 }

 if (servname != NULL) {
   log_warn(LD_BUG, "called with non-NULL servname");
   return EAI_NONAME;
 }
 if (name == NULL) {
   log_warn(LD_BUG, "called with NULL name");
   return EAI_NONAME;
 }

 *res = NULL;

 memset(&search, 0, sizeof(search));
 search.name = (char *) name;
 search.family = hints ? hints->ai_family : AF_UNSPEC;
 item = HT_FIND(getaddrinfo_cache, &getaddrinfo_cache, &search);

 if (! sandbox_getaddrinfo_is_active) {
   /* If the sandbox is not turned on yet, then getaddrinfo and store the
      result. */

   err = getaddrinfo(name, NULL, hints, res);
   log_info(LD_NET,"(Sandbox) getaddrinfo %s.", err ? "failed" : "succeeded");

   if (! item) {
     item = tor_malloc_zero(sizeof(*item));
     item->name = tor_strdup(name);
     item->family = hints ? hints->ai_family : AF_UNSPEC;
     HT_INSERT(getaddrinfo_cache, &getaddrinfo_cache, item);
   }

   if (item->res) {
     freeaddrinfo(item->res);
     item->res = NULL;
   }
   item->res = *res;
   item->err = err;
   return err;
 }

 /* Otherwise, the sandbox is on.  If we have an item, yield its cached
    result. */
 if (item) {
   *res = item->res;
   return item->err;
 }

 /* getting here means something went wrong */
 log_err(LD_BUG,"(Sandbox) failed to get address %s!", name);
 return EAI_NONAME;
}

int
tor_add_addrinfo(const char *name)
{
 struct addrinfo *res;
 struct addrinfo hints;
 int i;
 static const int families[] = { AF_INET, AF_INET6, AF_UNSPEC };

 memset(&hints, 0, sizeof(hints));
 hints.ai_socktype = SOCK_STREAM;
 for (i = 0; i < 3; ++i) {
   hints.ai_family = families[i];

   res = NULL;
   (void) tor_getaddrinfo(name, NULL, &hints, &res);
   if (res)
     tor_freeaddrinfo(res);
 }

 return 0;
}

void
tor_free_getaddrinfo_cache(void)
{
 cached_getaddrinfo_item_t **next, **item, *this;

 for (item = HT_START(getaddrinfo_cache, &getaddrinfo_cache);
      item;
      item = next) {
   this = *item;
   next = HT_NEXT_RMV(getaddrinfo_cache, &getaddrinfo_cache, item);
   cached_getaddrinfo_item_free(this);
 }

 HT_CLEAR(getaddrinfo_cache, &getaddrinfo_cache);
}

void
tor_make_getaddrinfo_cache_active(void)
{
 sandbox_getaddrinfo_is_active = 1;
}
#else /* !defined(USE_SANDBOX_GETADDRINFO) */
void
sandbox_disable_getaddrinfo_cache(void)
{
}
void
tor_make_getaddrinfo_cache_active(void)
{
}
#endif /* defined(USE_SANDBOX_GETADDRINFO) */