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ns_name.c

/*
 * Copyright (c) 1996,1999 by Internet Software Consortium.
 *
 * Permission to use, copy, modify, and distribute this software for any
 * purpose with or without fee is hereby granted, provided that the above
 * copyright notice and this permission notice appear in all copies.
 *
 * THE SOFTWARE IS PROVIDED "AS IS" AND INTERNET SOFTWARE CONSORTIUM DISCLAIMS
 * ALL WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL INTERNET SOFTWARE
 * CONSORTIUM BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL
 * DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR
 * PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS
 * ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS
 * SOFTWARE.
 */

#if !defined(_LIBC) && !defined(lint)
static const char rcsid[] = "$BINDId: ns_name.c,v 8.15 2000/03/30 22:53:46 vixie Exp $";
#endif

#include <sys/types.h>

#include <netinet/in.h>
#include <arpa/nameser.h>

#include <errno.h>
#include <resolv.h>
#include <string.h>
#include <ctype.h>

/* Data. */

static const char digits[] = "0123456789";

/* Forward. */

static int        special(int);
static int        printable(int);
static int        dn_find(const u_char *, const u_char *,
                        const u_char * const *,
                        const u_char * const *);

/* Public. */

/*
 * ns_name_ntop(src, dst, dstsiz)
 *    Convert an encoded domain name to printable ascii as per RFC1035.
 * return:
 *    Number of bytes written to buffer, or -1 (with errno set)
 * notes:
 *    The root is returned as "."
 *    All other domains are returned in non absolute form
 */
int
ns_name_ntop(const u_char *src, char *dst, size_t dstsiz) {
      const u_char *cp;
      char *dn, *eom;
      u_char c;
      u_int n;

      cp = src;
      dn = dst;
      eom = dst + dstsiz;

      while ((n = *cp++) != 0) {
            if ((n & NS_CMPRSFLGS) != 0) {
                  /* Some kind of compression pointer. */
                  __set_errno (EMSGSIZE);
                  return (-1);
            }
            if (dn != dst) {
                  if (dn >= eom) {
                        __set_errno (EMSGSIZE);
                        return (-1);
                  }
                  *dn++ = '.';
            }
            if (dn + n >= eom) {
                  __set_errno (EMSGSIZE);
                  return (-1);
            }
            for ((void)NULL; n > 0; n--) {
                  c = *cp++;
                  if (special(c)) {
                        if (dn + 1 >= eom) {
                              __set_errno (EMSGSIZE);
                              return (-1);
                        }
                        *dn++ = '\\';
                        *dn++ = (char)c;
                  } else if (!printable(c)) {
                        if (dn + 3 >= eom) {
                              __set_errno (EMSGSIZE);
                              return (-1);
                        }
                        *dn++ = '\\';
                        *dn++ = digits[c / 100];
                        *dn++ = digits[(c % 100) / 10];
                        *dn++ = digits[c % 10];
                  } else {
                        if (dn >= eom) {
                              __set_errno (EMSGSIZE);
                              return (-1);
                        }
                        *dn++ = (char)c;
                  }
            }
      }
      if (dn == dst) {
            if (dn >= eom) {
                  __set_errno (EMSGSIZE);
                  return (-1);
            }
            *dn++ = '.';
      }
      if (dn >= eom) {
            __set_errno (EMSGSIZE);
            return (-1);
      }
      *dn++ = '\0';
      return (dn - dst);
}

/*
 * ns_name_pton(src, dst, dstsiz)
 *    Convert a ascii string into an encoded domain name as per RFC1035.
 * return:
 *    -1 if it fails
 *    1 if string was fully qualified
 *    0 is string was not fully qualified
 * notes:
 *    Enforces label and domain length limits.
 */

int
ns_name_pton(const char *src, u_char *dst, size_t dstsiz) {
      u_char *label, *bp, *eom;
      int c, n, escaped;
      char *cp;

      escaped = 0;
      bp = dst;
      eom = dst + dstsiz;
      label = bp++;

      while ((c = *src++) != 0) {
            if (escaped) {
                  if ((cp = strchr(digits, c)) != NULL) {
                        n = (cp - digits) * 100;
                        if ((c = *src++) == 0 ||
                            (cp = strchr(digits, c)) == NULL) {
                              __set_errno (EMSGSIZE);
                              return (-1);
                        }
                        n += (cp - digits) * 10;
                        if ((c = *src++) == 0 ||
                            (cp = strchr(digits, c)) == NULL) {
                              __set_errno (EMSGSIZE);
                              return (-1);
                        }
                        n += (cp - digits);
                        if (n > 255) {
                              __set_errno (EMSGSIZE);
                              return (-1);
                        }
                        c = n;
                  }
                  escaped = 0;
            } else if (c == '\\') {
                  escaped = 1;
                  continue;
            } else if (c == '.') {
                  c = (bp - label - 1);
                  if ((c & NS_CMPRSFLGS) != 0) {      /* Label too big. */
                        __set_errno (EMSGSIZE);
                        return (-1);
                  }
                  if (label >= eom) {
                        __set_errno (EMSGSIZE);
                        return (-1);
                  }
                  *label = c;
                  /* Fully qualified ? */
                  if (*src == '\0') {
                        if (c != 0) {
                              if (bp >= eom) {
                                    __set_errno (EMSGSIZE);
                                    return (-1);
                              }
                              *bp++ = '\0';
                        }
                        if ((bp - dst) > MAXCDNAME) {
                              __set_errno (EMSGSIZE);
                              return (-1);
                        }
                        return (1);
                  }
                  if (c == 0 || *src == '.') {
                        __set_errno (EMSGSIZE);
                        return (-1);
                  }
                  label = bp++;
                  continue;
            }
            if (bp >= eom) {
                  __set_errno (EMSGSIZE);
                  return (-1);
            }
            *bp++ = (u_char)c;
      }
      c = (bp - label - 1);
      if ((c & NS_CMPRSFLGS) != 0) {            /* Label too big. */
            __set_errno (EMSGSIZE);
            return (-1);
      }
      if (label >= eom) {
            __set_errno (EMSGSIZE);
            return (-1);
      }
      *label = c;
      if (c != 0) {
            if (bp >= eom) {
                  __set_errno (EMSGSIZE);
                  return (-1);
            }
            *bp++ = 0;
      }
      if ((bp - dst) > MAXCDNAME) { /* src too big */
            __set_errno (EMSGSIZE);
            return (-1);
      }
      return (0);
}

/*
 * ns_name_ntol(src, dst, dstsiz)
 *    Convert a network strings labels into all lowercase.
 * return:
 *    Number of bytes written to buffer, or -1 (with errno set)
 * notes:
 *    Enforces label and domain length limits.
 */

int
ns_name_ntol(const u_char *src, u_char *dst, size_t dstsiz) {
      const u_char *cp;
      u_char *dn, *eom;
      u_char c;
      u_int n;

      cp = src;
      dn = dst;
      eom = dst + dstsiz;

      while ((n = *cp++) != 0) {
            if ((n & NS_CMPRSFLGS) != 0) {
                  /* Some kind of compression pointer. */
                  __set_errno (EMSGSIZE);
                  return (-1);
            }
            *dn++ = n;
            if (dn + n >= eom) {
                  __set_errno (EMSGSIZE);
                  return (-1);
            }
            for ((void)NULL; n > 0; n--) {
                  c = *cp++;
                  if (isupper(c))
                        *dn++ = tolower(c);
                  else
                        *dn++ = c;
            }
      }
      *dn++ = '\0';
      return (dn - dst);
}

/*
 * ns_name_unpack(msg, eom, src, dst, dstsiz)
 *    Unpack a domain name from a message, source may be compressed.
 * return:
 *    -1 if it fails, or consumed octets if it succeeds.
 */
int
ns_name_unpack(const u_char *msg, const u_char *eom, const u_char *src,
             u_char *dst, size_t dstsiz)
{
      const u_char *srcp, *dstlim;
      u_char *dstp;
      int n, len, checked;

      len = -1;
      checked = 0;
      dstp = dst;
      srcp = src;
      dstlim = dst + dstsiz;
      if (srcp < msg || srcp >= eom) {
            __set_errno (EMSGSIZE);
            return (-1);
      }
      /* Fetch next label in domain name. */
      while ((n = *srcp++) != 0) {
            /* Check for indirection. */
            switch (n & NS_CMPRSFLGS) {
            case 0:
                  /* Limit checks. */
                  if (dstp + n + 1 >= dstlim || srcp + n >= eom) {
                        __set_errno (EMSGSIZE);
                        return (-1);
                  }
                  checked += n + 1;
                  *dstp++ = n;
                  memcpy(dstp, srcp, n);
                  dstp += n;
                  srcp += n;
                  break;

            case NS_CMPRSFLGS:
                  if (srcp >= eom) {
                        __set_errno (EMSGSIZE);
                        return (-1);
                  }
                  if (len < 0)
                        len = srcp - src + 1;
                  srcp = msg + (((n & 0x3f) << 8) | (*srcp & 0xff));
                  if (srcp < msg || srcp >= eom) {  /* Out of range. */
                        __set_errno (EMSGSIZE);
                        return (-1);
                  }
                  checked += 2;
                  /*
                   * Check for loops in the compressed name;
                   * if we've looked at the whole message,
                   * there must be a loop.
                   */
                  if (checked >= eom - msg) {
                        __set_errno (EMSGSIZE);
                        return (-1);
                  }
                  break;

            default:
                  __set_errno (EMSGSIZE);
                  return (-1);                  /* flag error */
            }
      }
      *dstp = '\0';
      if (len < 0)
            len = srcp - src;
      return (len);
}

/*
 * ns_name_pack(src, dst, dstsiz, dnptrs, lastdnptr)
 *    Pack domain name 'domain' into 'comp_dn'.
 * return:
 *    Size of the compressed name, or -1.
 * notes:
 *    'dnptrs' is an array of pointers to previous compressed names.
 *    dnptrs[0] is a pointer to the beginning of the message. The array
 *    ends with NULL.
 *    'lastdnptr' is a pointer to the end of the array pointed to
 *    by 'dnptrs'.
 * Side effects:
 *    The list of pointers in dnptrs is updated for labels inserted into
 *    the message as we compress the name.  If 'dnptr' is NULL, we don't
 *    try to compress names. If 'lastdnptr' is NULL, we don't update the
 *    list.
 */
int
ns_name_pack(const u_char *src, u_char *dst, int dstsiz,
           const u_char **dnptrs, const u_char **lastdnptr)
{
      u_char *dstp;
      const u_char **cpp, **lpp, *eob, *msg;
      const u_char *srcp;
      int n, l, first = 1;

      srcp = src;
      dstp = dst;
      eob = dstp + dstsiz;
      lpp = cpp = NULL;
      if (dnptrs != NULL) {
            if ((msg = *dnptrs++) != NULL) {
                  for (cpp = dnptrs; *cpp != NULL; cpp++)
                        (void)NULL;
                  lpp = cpp;  /* end of list to search */
            }
      } else
            msg = NULL;

      /* make sure the domain we are about to add is legal */
      l = 0;
      do {
            n = *srcp;
            if ((n & NS_CMPRSFLGS) != 0) {
                  __set_errno (EMSGSIZE);
                  return (-1);
            }
            l += n + 1;
            if (l > MAXCDNAME) {
                  __set_errno (EMSGSIZE);
                  return (-1);
            }
            srcp += n + 1;
      } while (n != 0);

      /* from here on we need to reset compression pointer array on error */
      srcp = src;
      do {
            /* Look to see if we can use pointers. */
            n = *srcp;
            if (n != 0 && msg != NULL) {
                  l = dn_find(srcp, msg, (const u_char * const *)dnptrs,
                            (const u_char * const *)lpp);
                  if (l >= 0) {
                        if (dstp + 1 >= eob) {
                              goto cleanup;
                        }
                        *dstp++ = (l >> 8) | NS_CMPRSFLGS;
                        *dstp++ = l % 256;
                        return (dstp - dst);
                  }
                  /* Not found, save it. */
                  if (lastdnptr != NULL && cpp < lastdnptr - 1 &&
                      (dstp - msg) < 0x4000 && first) {
                        *cpp++ = dstp;
                        *cpp = NULL;
                        first = 0;
                  }
            }
            /* copy label to buffer */
            if (n & NS_CMPRSFLGS) {       /* Should not happen. */
                  goto cleanup;
            }
            if (dstp + 1 + n >= eob) {
                  goto cleanup;
            }
            memcpy(dstp, srcp, n + 1);
            srcp += n + 1;
            dstp += n + 1;
      } while (n != 0);

      if (dstp > eob) {
cleanup:
            if (msg != NULL)
                  *lpp = NULL;
            __set_errno (EMSGSIZE);
            return (-1);
      } 
      return (dstp - dst);
}

/*
 * ns_name_uncompress(msg, eom, src, dst, dstsiz)
 *    Expand compressed domain name to presentation format.
 * return:
 *    Number of bytes read out of `src', or -1 (with errno set).
 * note:
 *    Root domain returns as "." not "".
 */
int
ns_name_uncompress(const u_char *msg, const u_char *eom, const u_char *src,
               char *dst, size_t dstsiz)
{
      u_char tmp[NS_MAXCDNAME];
      int n;
      
      if ((n = ns_name_unpack(msg, eom, src, tmp, sizeof tmp)) == -1)
            return (-1);
      if (ns_name_ntop(tmp, dst, dstsiz) == -1)
            return (-1);
      return (n);
}

/*
 * ns_name_compress(src, dst, dstsiz, dnptrs, lastdnptr)
 *    Compress a domain name into wire format, using compression pointers.
 * return:
 *    Number of bytes consumed in `dst' or -1 (with errno set).
 * notes:
 *    'dnptrs' is an array of pointers to previous compressed names.
 *    dnptrs[0] is a pointer to the beginning of the message.
 *    The list ends with NULL.  'lastdnptr' is a pointer to the end of the
 *    array pointed to by 'dnptrs'. Side effect is to update the list of
 *    pointers for labels inserted into the message as we compress the name.
 *    If 'dnptr' is NULL, we don't try to compress names. If 'lastdnptr'
 *    is NULL, we don't update the list.
 */
int
ns_name_compress(const char *src, u_char *dst, size_t dstsiz,
             const u_char **dnptrs, const u_char **lastdnptr)
{
      u_char tmp[NS_MAXCDNAME];

      if (ns_name_pton(src, tmp, sizeof tmp) == -1)
            return (-1);
      return (ns_name_pack(tmp, dst, dstsiz, dnptrs, lastdnptr));
}

/*
 * Reset dnptrs so that there are no active references to pointers at or
 * after src.
 */
void
ns_name_rollback(const u_char *src, const u_char **dnptrs,
             const u_char **lastdnptr)
{
      while (dnptrs < lastdnptr && *dnptrs != NULL) {
            if (*dnptrs >= src) {
                  *dnptrs = NULL;
                  break;
            }
            dnptrs++;
      }
}

/*
 * ns_name_skip(ptrptr, eom)
 *    Advance *ptrptr to skip over the compressed name it points at.
 * return:
 *    0 on success, -1 (with errno set) on failure.
 */
int
ns_name_skip(const u_char **ptrptr, const u_char *eom) {
      const u_char *cp;
      u_int n;

      cp = *ptrptr;
      while (cp < eom && (n = *cp++) != 0) {
            /* Check for indirection. */
            switch (n & NS_CMPRSFLGS) {
            case 0:                 /* normal case, n == len */
                  cp += n;
                  continue;
            case NS_CMPRSFLGS:      /* indirection */
                  cp++;
                  break;
            default:          /* illegal type */
                  __set_errno (EMSGSIZE);
                  return (-1);
            }
            break;
      }
      if (cp > eom) {
            __set_errno (EMSGSIZE);
            return (-1);
      }
      *ptrptr = cp;
      return (0);
}

/* Private. */

/*
 * special(ch)
 *    Thinking in noninternationalized USASCII (per the DNS spec),
 *    is this characted special ("in need of quoting") ?
 * return:
 *    boolean.
 */
static int
special(int ch) {
      switch (ch) {
      case 0x22: /* '"' */
      case 0x2E: /* '.' */
      case 0x3B: /* ';' */
      case 0x5C: /* '\\' */
      /* Special modifiers in zone files. */
      case 0x40: /* '@' */
      case 0x24: /* '$' */
            return (1);
      default:
            return (0);
      }
}

/*
 * printable(ch)
 *    Thinking in noninternationalized USASCII (per the DNS spec),
 *    is this character visible and not a space when printed ?
 * return:
 *    boolean.
 */
static int
printable(int ch) {
      return (ch > 0x20 && ch < 0x7f);
}

/*
 *    Thinking in noninternationalized USASCII (per the DNS spec),
 *    convert this character to lower case if it's upper case.
 */
static int
mklower(int ch) {
      if (ch >= 0x41 && ch <= 0x5A)
            return (ch + 0x20);
      return (ch);
}

/*
 * dn_find(domain, msg, dnptrs, lastdnptr)
 *    Search for the counted-label name in an array of compressed names.
 * return:
 *    offset from msg if found, or -1.
 * notes:
 *    dnptrs is the pointer to the first name on the list,
 *    not the pointer to the start of the message.
 */
static int
dn_find(const u_char *domain, const u_char *msg,
      const u_char * const *dnptrs,
      const u_char * const *lastdnptr)
{
      const u_char *dn, *cp, *sp;
      const u_char * const *cpp;
      u_int n;

      for (cpp = dnptrs; cpp < lastdnptr; cpp++) {
            sp = *cpp;
            /*
             * terminate search on:
             * root label
             * compression pointer
             * unusable offset
             */
            while (*sp != 0 && (*sp & NS_CMPRSFLGS) == 0 &&
                   (sp - msg) < 0x4000) {
                  dn = domain;
                  cp = sp;
                  while ((n = *cp++) != 0) {
                        /*
                         * check for indirection
                         */
                        switch (n & NS_CMPRSFLGS) {
                        case 0:           /* normal case, n == len */
                              if (n != *dn++)
                                    goto next;
                              for ((void)NULL; n > 0; n--)
                                    if (mklower(*dn++) !=
                                        mklower(*cp++))
                                          goto next;
                              /* Is next root for both ? */
                              if (*dn == '\0' && *cp == '\0')
                                    return (sp - msg);
                              if (*dn)
                                    continue;
                              goto next;

                        case NS_CMPRSFLGS:      /* indirection */
                              cp = msg + (((n & 0x3f) << 8) | *cp);
                              break;

                        default:    /* illegal type */
                              __set_errno (EMSGSIZE);
                              return (-1);
                        }
                  }
 next:
                  sp += *sp + 1;
            }
      }
      __set_errno (ENOENT);
      return (-1);
}

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