text: /*
   * Copyright (c) 2004,2009,2014 by Internet Systems Consortium, Inc. ("ISC")
   * Copyright (c) 1996-2003 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 ISC DISCLAIMS ALL WARRANTIES
   * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
   * MERCHANTABILITY AND FITNESS.  IN NO EVENT SHALL ISC 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.
   *
   *   Internet Systems Consortium, Inc.
   *   950 Charter Street
   *   Redwood City, CA 94063
   *   <info@isc.org>
   *   http://www.isc.org/
   */
  
  #include <sys/types.h>
  
  #include <netinet/in.h>
  #include <sys/socket.h>
  
  #include <errno.h>
  #include <string.h>
  #include <ctype.h>
  
  #include "minires.h"
  #include "arpa/nameser.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. */
  
  /*
   * MRns_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
  MRns_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. */
  			errno = EMSGSIZE;
  			return (-1);
  		}
  		if (dn != dst) {
  			if (dn >= eom) {
  				errno = EMSGSIZE;
  				return (-1);
  			}
  			*dn++ = '.';
  		}
  		if (dn + n >= eom) {
  			errno = EMSGSIZE;
  			return (-1);
  		}
  		for ((void)NULL; n > 0; n--) {
  			c = *cp++;
  			if (special(c)) {
  				if (dn + 1 >= eom) {
  					errno = EMSGSIZE;
  					return (-1);
  				}
  				*dn++ = '\\';
  				*dn++ = (char)c;
  			} else if (!printable(c)) {
  				if (dn + 3 >= eom) {
  					errno = EMSGSIZE;
  					return (-1);
  				}
  				*dn++ = '\\';
  				*dn++ = digits[c / 100];
  				*dn++ = digits[(c % 100) / 10];
  				*dn++ = digits[c % 10];
  			} else {
  				if (dn >= eom) {
  					errno = EMSGSIZE;
  					return (-1);
  				}
  				*dn++ = (char)c;
  			}
  		}
  	}
  	if (dn == dst) {
  		if (dn >= eom) {
  			errno = EMSGSIZE;
  			return (-1);
  		}
  		*dn++ = '.';
  	}
  	if (dn >= eom) {
  		errno = EMSGSIZE;
  		return (-1);
  	}
  	*dn++ = '\0';
  	return (dn - dst);
  }
  
  /*
   * MRns_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
  MRns_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) {
  					errno = EMSGSIZE;
  					return (-1);
  				}
  				n += (cp - digits) * 10;
  				if ((c = *src++) == 0 ||
  				    (cp = strchr(digits, c)) == NULL) {
  					errno = EMSGSIZE;
  					return (-1);
  				}
  				n += (cp - digits);
  				if (n > 255) {
  					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. */
  				errno = EMSGSIZE;
  				return (-1);
  			}
  			if (label >= eom) {
  				errno = EMSGSIZE;
  				return (-1);
  			}
  			*label = c;
  			/* Fully qualified ? */
  			if (*src == '\0') {
  				if (c != 0) {
  					if (bp >= eom) {
  						errno = EMSGSIZE;
  						return (-1);
  					}
  					*bp++ = '\0';
  				}
  				if ((bp - dst) > MAXCDNAME) {
  					errno = EMSGSIZE;
  					return (-1);
  				}
  				return (1);
  			}
  			if (c == 0 || *src == '.') {
  				errno = EMSGSIZE;
  				return (-1);
  			}
  			label = bp++;
  			continue;
  		}
  		if (bp >= eom) {
  			errno = EMSGSIZE;
  			return (-1);
  		}
  		*bp++ = (u_char)c;
  	}
  	c = (bp - label - 1);
  	if ((c & NS_CMPRSFLGS) != 0) {		/* Label too big. */
  		errno = EMSGSIZE;
  		return (-1);
  	}
  	if (label >= eom) {
  		errno = EMSGSIZE;
  		return (-1);
  	}
  	*label = c;
  	if (c != 0) {
  		if (bp >= eom) {
  			errno = EMSGSIZE;
  			return (-1);
  		}
  		*bp++ = 0;
  	}
  	if ((bp - dst) > MAXCDNAME) {	/* src too big */
  		errno = EMSGSIZE;
  		return (-1);
  	}
  	return (0);
  }
  
  /*
   * MRns_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
  MRns_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;
  
  	if (dn >= eom) {
  		errno = EMSGSIZE;
  		return (-1);
  	}
  	while ((n = *cp++) != 0) {
  		if ((n & NS_CMPRSFLGS) != 0) {
  			/* Some kind of compression pointer. */
  			errno = EMSGSIZE;
  			return (-1);
  		}
  		*dn++ = n;
  		if (dn + n >= eom) {
  			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);
  }
  
  /*
   * MRns_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
  MRns_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;
  	unsigned n;
  	int len;
  	int checked;
  
  	len = -1;
  	checked = 0;
  	dstp = dst;
  	srcp = src;
  	dstlim = dst + dstsiz;
  	if (srcp < msg || srcp >= eom) {
  		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) {
  				errno = EMSGSIZE;
  				return (-1);
  			}
  			checked += n + 1;
  			*dstp++ = n;
  			memcpy(dstp, srcp, n);
  			dstp += n;
  			srcp += n;
  			break;
  
  		case NS_CMPRSFLGS:
  			if (srcp >= eom) {
  				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. */
  				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) {
  				errno = EMSGSIZE;
  				return (-1);
  			}
  			break;
  
  		default:
  			errno = EMSGSIZE;
  			return (-1);			/* flag error */
  		}
  	}
  	*dstp = '\0';
  	if (len < 0)
  		len = srcp - src;
  	return (len);
  }
  
  /*
   * MRns_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
  MRns_name_pack(const u_char *src, u_char *dst, unsigned dstsiz,
  	       const u_char **dnptrs, const u_char **lastdnptr)
  {
  	u_char *dstp;
  	const u_char **cpp, **lpp, *eob, *msg;
  	const u_char *srcp;
  	unsigned n;
  	int l;
  
  	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) {
  			errno = EMSGSIZE;
  			return (-1);
  		}
  		l += n + 1;
  		if (l > MAXCDNAME) {
  			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) {
  				*cpp++ = dstp;
  				*cpp = NULL;
  			}
  		}
  		/* 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;
  		errno = EMSGSIZE;
  		return (-1);
  	} 
  	return (dstp - dst);
  }
  
  /*
   * MRns_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
  MRns_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 = MRns_name_unpack(msg, eom, src, tmp, sizeof tmp)) == -1)
  		return (-1);
  	if (MRns_name_ntop(tmp, dst, dstsiz) == -1)
  		return (-1);
  	return (n);
  }
  
  /*
   * MRns_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
  MRns_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 (MRns_name_pton(src, tmp, sizeof tmp) == -1)
  		return (-1);
  	return (MRns_name_pack(tmp, dst, dstsiz, dnptrs, lastdnptr));
  }
  
  /*
   * MRns_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
  MRns_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 */
  			errno = EMSGSIZE;
  			return (-1);
  		}
  		break;
  	}
  	if (cp > eom) {
  		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++) {
  		dn = domain;
  		sp = cp = *cpp;
  		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 */
  				errno = EMSGSIZE;
  				return (-1);
  			}
  		}
   next: ;
  	}
  	errno = ENOENT;
  	return (-1);
  }
  