glibc/nss/digits_dots.c

/* Copyright (C) 1997-2024 Free Software Foundation, Inc.
   This file is part of the GNU C Library.

   The GNU C Library is free software; you can redistribute it and/or
   modify it under the terms of the GNU Lesser General Public
   License as published by the Free Software Foundation; either
   version 2.1 of the License, or (at your option) any later version.

   The GNU C Library 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
   Lesser General Public License for more details.

   You should have received a copy of the GNU Lesser General Public
   License along with the GNU C Library; if not, see
   <https://www.gnu.org/licenses/>.  */

#include <assert.h>
#include <errno.h>
#include <string.h>
#include <stdlib.h>
#include <ctype.h>
#include <wctype.h>
#include <resolv/resolv-internal.h>
#include <resolv/resolv_context.h>
#include <netdb.h>
#include <arpa/inet.h>
#include "nsswitch.h"

#ifdef USE_NSCD
# include <nscd/nscd_proto.h>
#endif

int
__nss_hostname_digits_dots (const char *name, struct hostent *resbuf,
			    char **buffer, size_t *buffer_size,
			    size_t buflen, struct hostent **result,
			    enum nss_status *status, int af, int *h_errnop)
{
  /* We have to test for the use of IPv6 which can only be done by
     examining `_res'.  */
  struct resolv_context *ctx = __resolv_context_get ();
  if (ctx == NULL)
    {
      if (h_errnop)
	*h_errnop = NETDB_INTERNAL;
      if (buffer_size == NULL)
	*status = NSS_STATUS_TRYAGAIN;
      else
	*result = NULL;
      return -1;
    }
  int ret = __nss_hostname_digits_dots_context
    (ctx, name, resbuf, buffer, buffer_size, buflen,
     result, status, af, h_errnop);
  __resolv_context_put (ctx);
  return ret;
}

int
__nss_hostname_digits_dots_context (struct resolv_context *ctx,
				    const char *name, struct hostent *resbuf,
				    char **buffer, size_t *buffer_size,
				    size_t buflen, struct hostent **result,
				    enum nss_status *status, int af, int *h_errnop)
{
  int save;

  /*
   * disallow names consisting only of digits/dots, unless
   * they end in a dot.
   */
  if (isdigit (name[0]) || isxdigit (name[0]) || name[0] == ':')
    {
      const char *cp;
      char *hostname;
      typedef unsigned char host_addr_t[16];
      host_addr_t *host_addr;
      typedef char *host_addr_list_t[2];
      host_addr_list_t *h_addr_ptrs;
      char **h_alias_ptr;
      size_t size_needed;
      int addr_size;

      switch (af)
	{
	case AF_INET:
	  addr_size = INADDRSZ;
	  break;

	case AF_INET6:
	  addr_size = IN6ADDRSZ;
	  break;

	default:
	  af = res_use_inet6 () ? AF_INET6 : AF_INET;
	  addr_size = af == AF_INET6 ? IN6ADDRSZ : INADDRSZ;
	  break;
	}

      size_needed = (sizeof (*host_addr)
		     + sizeof (*h_addr_ptrs)
		     + sizeof (*h_alias_ptr) + strlen (name) + 1);

      if (buffer_size == NULL)
        {
	  if (buflen < size_needed)
	    {
	      *status = NSS_STATUS_TRYAGAIN;
	      if (h_errnop != NULL)
		*h_errnop = NETDB_INTERNAL;
	      __set_errno (ERANGE);
	      goto done;
	    }
	}
      else if (buffer_size != NULL && *buffer_size < size_needed)
	{
	  char *new_buf;
	  *buffer_size = size_needed;
	  new_buf = (char *) realloc (*buffer, *buffer_size);

	  if (new_buf == NULL)
	    {
	      save = errno;
	      free (*buffer);
	      *buffer = NULL;
	      *buffer_size = 0;
	      __set_errno (save);
	      if (h_errnop != NULL)
		*h_errnop = NETDB_INTERNAL;
	      *result = NULL;
	      goto done;
	    }
	  *buffer = new_buf;
	}

      memset (*buffer, '\0', size_needed);

      host_addr = (host_addr_t *) *buffer;
      h_addr_ptrs = (host_addr_list_t *)
	((char *) host_addr + sizeof (*host_addr));
      h_alias_ptr = (char **) ((char *) h_addr_ptrs + sizeof (*h_addr_ptrs));
      hostname = (char *) h_alias_ptr + sizeof (*h_alias_ptr);

      if (isdigit (name[0]))
	{
	  for (cp = name;; ++cp)
	    {
	      if (*cp == '\0')
		{
		  int ok;

		  if (*--cp == '.')
		    break;

		  /* All-numeric, no dot at the end. Fake up a hostent as if
		     we'd actually done a lookup.  What if someone types
		     255.255.255.255?  The test below will succeed
		     spuriously... ???  */
		  if (af == AF_INET)
		    ok = __inet_aton_exact (name, (struct in_addr *) host_addr);
		  else
		    {
		      assert (af == AF_INET6);
		      ok = inet_pton (af, name, host_addr) > 0;
		    }
		  if (! ok)
		    {
		      *h_errnop = HOST_NOT_FOUND;
		      if (buffer_size == NULL)
			*status = NSS_STATUS_NOTFOUND;
		      else
			*result = NULL;
		      goto done;
		    }

		  resbuf->h_name = strcpy (hostname, name);
		  h_alias_ptr[0] = NULL;
		  resbuf->h_aliases = h_alias_ptr;
		  (*h_addr_ptrs)[0] = (char *) host_addr;
		  (*h_addr_ptrs)[1] = NULL;
		  resbuf->h_addr_list = *h_addr_ptrs;
		  if (af == AF_INET && res_use_inet6 ())
		    {
		      /* We need to change the IP v4 address into the
			 IP v6 address.  */
		      char tmp[INADDRSZ];
		      char *p = (char *) host_addr;
		      int i;

		      /* Save a copy of the IP v4 address. */
		      memcpy (tmp, host_addr, INADDRSZ);
		      /* Mark this ipv6 addr as a mapped ipv4. */
		      for (i = 0; i < 10; i++)
			*p++ = 0x00;
		      *p++ = 0xff;
		      *p++ = 0xff;
		      /* Copy the IP v4 address. */
		      memcpy (p, tmp, INADDRSZ);
		      resbuf->h_addrtype = AF_INET6;
		      resbuf->h_length = IN6ADDRSZ;
		    }
		  else
		    {
		      resbuf->h_addrtype = af;
		      resbuf->h_length = addr_size;
		    }
		  if (h_errnop != NULL)
		    *h_errnop = NETDB_SUCCESS;
		  if (buffer_size == NULL)
		    *status = NSS_STATUS_SUCCESS;
		  else
		    *result = resbuf;
		  goto done;
		}

	      if (!isdigit (*cp) && *cp != '.')
		break;
	    }
	}

      if ((isxdigit (name[0]) && strchr (name, ':') != NULL) || name[0] == ':')
	{
	  switch (af)
	    {
	    default:
	      af = res_use_inet6 () ? AF_INET6 : AF_INET;
	      if (af == AF_INET6)
		{
		  addr_size = IN6ADDRSZ;
		  break;
		}
	      /* FALLTHROUGH */

	    case AF_INET:
	      /* This is not possible.  We cannot represent an IPv6 address
		 in an `struct in_addr' variable.  */
	      *h_errnop = HOST_NOT_FOUND;
	      if (buffer_size == NULL)
		*status = NSS_STATUS_NOTFOUND;
	      else
		*result = NULL;
	      goto done;

	    case AF_INET6:
	      addr_size = IN6ADDRSZ;
	      break;
	    }

	  for (cp = name;; ++cp)
	    {
	      if (!*cp)
		{
		  if (*--cp == '.')
		    break;

		  /* All-IPv6-legal, no dot at the end. Fake up a
		     hostent as if we'd actually done a lookup.  */
		  if (inet_pton (AF_INET6, name, host_addr) <= 0)
		    {
		      *h_errnop = HOST_NOT_FOUND;
		      if (buffer_size == NULL)
			*status = NSS_STATUS_NOTFOUND;
		      else
			*result = NULL;
		      goto done;
		    }

		  resbuf->h_name = strcpy (hostname, name);
		  h_alias_ptr[0] = NULL;
		  resbuf->h_aliases = h_alias_ptr;
		  (*h_addr_ptrs)[0] = (char *) host_addr;
		  (*h_addr_ptrs)[1] = (char *) 0;
		  resbuf->h_addr_list = *h_addr_ptrs;
		  resbuf->h_addrtype = AF_INET6;
		  resbuf->h_length = addr_size;
		  *h_errnop = NETDB_SUCCESS;
		  if (buffer_size == NULL)
		    *status = NSS_STATUS_SUCCESS;
		  else
		    *result = resbuf;
		  goto done;
		}

	      if (!isxdigit (*cp) && *cp != ':' && *cp != '.')
		break;
	    }
	}
    }

  return 0;

done:
  return 1;
}
libc_hidden_def (__nss_hostname_digits_dots)