Add human readable parsing/display of RFC1035 data in domain-search

option. Replace handrolled dn_expand() with the system
version. Existing hex octet versions still accepted. New format is

option domain-search "my.domain.org", "fw.my.domain.org";

It is now possible to append and prepend domains to the list provided
by the server.

Documention update to dhcp-options(5) in the pipeline!

Inspired by dhcpd(8) domain-search diff from William Ahern.

Code peered at by florian@ and kn@.

4 files changed, 186 insertions, 132 deletions

diff --git a/sbin/dhclient/clparse.c b/sbin/dhclient/clparse.c
index 6998056e8fb..f934a171de5 100644
--- a/sbin/dhclient/clparse.c
+++ b/sbin/dhclient/clparse.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: clparse.c,v 1.184 2019/03/20 20:10:00 krw Exp $	*/
+/*	$OpenBSD: clparse.c,v 1.185 2019/04/02 02:59:43 krw Exp $	*/
 
 /* Parser for dhclient config and lease files. */
 
@@ -69,6 +69,7 @@
 
 void	parse_conf_decl(FILE *, char *);
 int	parse_hex_octets(FILE *, unsigned int *, uint8_t **);
+int	parse_domain_list(FILE *, int *, char **);
 int	parse_option_list(FILE *, int *, uint8_t *);
 int	parse_interface(FILE *, char *);
 int	parse_lease(FILE *, char *, struct client_lease **);
@@ -471,6 +472,53 @@ parse_hex_octets(FILE *cfile, unsigned int *len, uint8_t **buf)
 	return 0;
 }
 
+int
+parse_domain_list(FILE *cfile, int *len, char **dp)
+{
+	uint8_t		 buf[DHCP_DOMAIN_SEARCH_LEN];
+	char		*domain;
+	int		 count, token;
+
+	memset(buf, 0, sizeof(buf));
+	count = 0;
+
+	do {
+		if (parse_string(cfile, NULL, &domain) == 0)
+			return 0;
+
+		count++;
+		if (count > DHCP_DOMAIN_SEARCH_CNT) {
+			parse_warn("more than 6 search domains");
+			break;
+		}
+
+		if (count > 1)
+			strlcat(buf, " ", sizeof(buf));
+		if (strlcat(buf, domain, sizeof(buf)) >= sizeof(buf)) {
+			parse_warn("domain list too long");
+			break;
+		}
+
+		token = peek_token(NULL, cfile);
+		if (token == ';') {
+			*dp = strdup(buf);
+			if (*dp == NULL)
+				fatal("domain name list");
+			*len = strlen(buf) + 1;
+			memcpy(*dp, buf, *len);
+			return 1;
+		}
+		token = next_token(NULL, cfile);
+		if (token != ',')
+			parse_warn("';' or ',' expected");
+	} while (token == ',');
+
+	if (token != ';')
+		skip_to_semi(cfile);
+
+	return 0;
+}
+
 /*
  * option-list :==
  *	  <nil>
@@ -824,6 +872,24 @@ parse_option(FILE *cfile, int *code, struct option_data *options)
 				len = 1 + (cidr[0] + 7) / 8;
 				dp = cidr;
 				break;
+			case 'D':
+				if (peek_token(NULL, cfile) == TOK_STRING) {
+					if (parse_domain_list(cfile, &len,
+					    (char **)&dp) == 0)
+						return 0;
+				} else if (parse_hex_octets(cfile, &len, &dp)
+				    == 0) {
+					return 0;
+				} else {
+					val = rfc1035_as_string(dp, len);
+					free(dp);
+					dp = strdup(val);
+					if (dp == NULL)
+						fatal("RFC1035 hex octets");
+					len = strlen(dp) + 1;
+				}
+				freedp = 1;
+				break;
 			default:
 				log_warnx("%s: bad format %c in "
 				    "parse_option_param", log_procname, *fmt);
diff --git a/sbin/dhclient/dhclient.c b/sbin/dhclient/dhclient.c
index e4fc18d214d..b13bb985032 100644
--- a/sbin/dhclient/dhclient.c
+++ b/sbin/dhclient/dhclient.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: dhclient.c,v 1.630 2019/03/22 16:45:48 krw Exp $	*/
+/*	$OpenBSD: dhclient.c,v 1.631 2019/04/02 02:59:43 krw Exp $	*/
 
 /*
  * Copyright 2004 Henning Brauer <henning@openbsd.org>
@@ -1127,17 +1127,20 @@ packet_to_lease(struct interface_info *ifi, struct option_data *options)
 		if (options[i].len == 0)
 			continue;
 		name = code_to_name(i);
-		pretty = pretty_print_option(i, &options[i], 0);
+		if (i == DHO_DOMAIN_SEARCH) {
+			/* Replace RFC 1035 data with a string. */
+			pretty = rfc1035_as_string(options[i].data, options[i].len);
+			free(options[i].data);
+			options[i].data = strdup(pretty);
+			if (options[i].data == NULL)
+				fatal("RFC1035 string");
+			options[i].len = strlen(lease->options[i].data) + 1;
+		} else
+			pretty = pretty_print_option(i, &options[i], 0);
 		if (strlen(pretty) == 0)
 			continue;
 		switch (i) {
 		case DHO_DOMAIN_SEARCH:
-			if (strlen(pretty) == 0 || res_hnok_list(pretty) == 0) {
-				log_debug("%s: invalid host name in %s",
-				    log_procname, name);
-				continue;
-			}
-			break;
 		case DHO_DOMAIN_NAME:
 			/*
 			 * Allow deviant but historically blessed
@@ -1865,7 +1868,6 @@ lease_as_proposal(struct client_lease *lease)
 {
 	struct proposal		*proposal;
 	struct option_data	*opt;
-	char			*pretty;
 
 	proposal = calloc(1, sizeof(*proposal));
 	if (proposal == NULL)
@@ -1921,11 +1923,9 @@ lease_as_proposal(struct client_lease *lease)
 
 	if (lease->options[DHO_DOMAIN_SEARCH].len != 0) {
 		opt = &lease->options[DHO_DOMAIN_SEARCH];
-		pretty = pretty_print_domain_search(opt->data, opt->len);
-		if (pretty != NULL && strlen(pretty) > 0 && strlen(pretty) <
-		    sizeof(proposal->rtsearch)) {
-			proposal->rtsearch_len = strlen(pretty);
-			memcpy(proposal->rtsearch, pretty,
+		if (opt->len < sizeof(proposal->rtsearch)) {
+			proposal->rtsearch_len = strlen(opt->data);
+			memcpy(proposal->rtsearch, opt->data,
 			    proposal->rtsearch_len);
 			proposal->addrs |= RTA_SEARCH;
 		} else
@@ -2134,6 +2134,57 @@ res_hnok_list(const char *names)
 	return count > 0 && count < 7 && hn == NULL;
 }
 
+/*
+ * Decode a byte string encoding a list of domain names as specified in RFC 1035
+ * section 4.1.4.
+ *
+ * The result is a string consisting of a blank separated list of domain names.
+ *
+ e.g. 3:65:6e:67:5:61:70:70:6c:65:3:63:6f:6d:0:9:6d:61:72:6b:65:74:69:6e:67:c0:04
+ *
+ *    3 |'e'|'n'|'g'| 5 |'a'|'p'|'p'|'l'|
+ *   'e'| 3 |'c'|'o'|'m'| 0 | 9 |'m'|'a'|
+ *   'r'|'k'|'e'|'t'|'i'|'n'|'g'|xC0|x04|
+ *
+ * will be translated to
+ *
+ * "eng.apple.com. marketing.apple.com."
+ */
+char *
+rfc1035_as_string(unsigned char *src, size_t srclen)
+{
+	static char		 search[DHCP_DOMAIN_SEARCH_LEN];
+	unsigned char		 name[DHCP_DOMAIN_SEARCH_LEN];
+	unsigned char		*endsrc, *cp;
+	int			 len, domains;
+
+	memset(search, 0, sizeof(search));
+
+	/* Compute expanded length. */
+	domains = 0;
+	cp = src;
+	endsrc = src + srclen;
+
+	while (cp < endsrc && domains < DHCP_DOMAIN_SEARCH_CNT) {
+		len = dn_expand(src, endsrc, cp, name, sizeof(name));
+		if (len == -1)
+			goto bad;
+		cp += len;
+		if (domains > 0)
+			strlcat(search, " ", sizeof(search));
+		strlcat(search, name, sizeof(search));
+		if (strlcat(search, ".", sizeof(search)) >= sizeof(search))
+			goto bad;
+		domains++;
+	}
+
+	return search;
+
+bad:
+	memset(search, 0, sizeof(search));
+	return search;
+}
+
 void
 fork_privchld(struct interface_info *ifi, int fd, int fd2)
 {
diff --git a/sbin/dhclient/dhcpd.h b/sbin/dhclient/dhcpd.h
index a765409d961..980777a629d 100644
--- a/sbin/dhclient/dhcpd.h
+++ b/sbin/dhclient/dhcpd.h
@@ -1,4 +1,4 @@
-/*	$OpenBSD: dhcpd.h,v 1.276 2019/03/22 16:45:48 krw Exp $	*/
+/*	$OpenBSD: dhcpd.h,v 1.277 2019/04/02 02:59:43 krw Exp $	*/
 
 /*
  * Copyright (c) 2004 Henning Brauer <henning@openbsd.org>
@@ -160,7 +160,6 @@ struct option_data	*unpack_options(struct dhcp_packet *);
 char			*pretty_print_option(unsigned int, struct option_data *,
     int);
 char			*pretty_print_string(unsigned char *, size_t, int);
-char			*pretty_print_domain_search(unsigned char *, size_t);
 char			*code_to_name(int);
 char			*code_to_format(int);
 int			 code_to_action(int, int);
@@ -224,6 +223,7 @@ void		 bootreply(struct interface_info *, struct option_data *,
 void		 free_client_lease(struct client_lease *);
 void		 routefd_handler(struct interface_info *, int);
 void		 state_preboot(struct interface_info *);
+char		*rfc1035_as_string(unsigned char *, size_t);
 
 /* packet.c */
 void		 assemble_eh_header(struct ether_addr, struct ether_header *);
diff --git a/sbin/dhclient/options.c b/sbin/dhclient/options.c
index 38beeb18834..833a0aebaad 100644
--- a/sbin/dhclient/options.c
+++ b/sbin/dhclient/options.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: options.c,v 1.117 2019/03/22 16:45:48 krw Exp $	*/
+/*	$OpenBSD: options.c,v 1.118 2019/04/02 02:59:43 krw Exp $	*/
 
 /* DHCP options parsing and reassembly. */
 
@@ -51,6 +51,7 @@
 #include <netinet/if_ether.h>
 
 #include <ctype.h>
+#include <resolv.h>
 #include <signal.h>
 #include <stdio.h>
 #include <stdlib.h>
@@ -64,7 +65,8 @@
 int	parse_option_buffer(struct option_data *, unsigned char *, int);
 void	pretty_print_classless_routes(unsigned char *, size_t, unsigned char *,
     size_t);
-int expand_search_domain_name(unsigned char *, size_t, int *, unsigned char *);
+void	pretty_print_domain_list(unsigned char *, size_t, unsigned char *,
+    size_t);
 
 /*
  * DHCP Option names, formats and codes, from RFC1533.
@@ -82,6 +84,7 @@ int expand_search_domain_name(unsigned char *, size_t, int *, unsigned char *);
  * A - array of whatever precedes (e.g., IA means array of IP addresses)
  * C - CIDR description
  * X - hex octets
+ * D - domain name list, comma separated list of domain names.
  */
 
 static const struct {
@@ -207,7 +210,7 @@ static const struct {
 	/* 116 */ { NULL, NULL },
 	/* 117 */ { NULL, NULL },
 	/* 118 */ { NULL, NULL },
-	/* 119 */ { "domain-search", "X" },
+	/* 119 */ { "domain-search", "D" },
 	/* 120 */ { NULL, NULL },
 	/* 121 */ { "classless-static-routes", "CIA" },
 	/* 122 */ { NULL, NULL },
@@ -410,10 +413,7 @@ code_to_action(int code, int action)
 	char	*fmt;
 
 	fmt = code_to_format(code);
-	if (fmt == NULL || strpbrk(fmt, "At") != NULL)
-		return action;
-
-	if (fmt[0] == 'X' && code != DHO_DOMAIN_SEARCH)
+	if (fmt == NULL || strpbrk(fmt, "ADtX") != NULL)
 		return action;
 
 	/*
@@ -652,122 +652,56 @@ bad:
 	memset(buf, 0, buflen);
 }
 
-int
-expand_search_domain_name(unsigned char *src, size_t srclen, int *offset,
-    unsigned char *domain_search)
+/*
+ * Print string containing blank separated list of domain names
+ * as a comma separated list of double-quote delimited strings.
+ *
+ * e.g.  "eng.apple.com. marketing.apple.com."
+ *
+ * will be translated to
+ *
+ * "eng.apple.com.", "marketing.apple.com."
+ */
+void
+pretty_print_domain_list(unsigned char *src, size_t srclen,
+    unsigned char *buf, size_t buflen)
 {
-	char		*cursor;
-	unsigned int	 i;
-	int		 domain_name_len, label_len, pointer, pointed_len;
-
-	cursor = domain_search + strlen(domain_search);
-	domain_name_len = 0;
-
-	i = *offset;
-	while (i <= srclen) {
-		label_len = src[i];
-		if (label_len == 0) {
-			/*
-			 * A zero-length label marks the end of this
-			 * domain name.
-			 */
-			*offset = i + 1;
-			return domain_name_len;
-		} else if ((label_len & 0xC0) != 0) {
-			/* This is a pointer to another list of labels. */
-			if (i + 1 >= srclen) {
-				/* The pointer is truncated. */
-				log_warnx("%s: truncated pointer in DHCP "
-				    "Domain Search option", log_procname);
-				return -1;
-			}
+	char	*dupnames, *hn, *inputstring;
+	int	 count;
 
-			pointer = ((label_len & ~(0xC0)) << 8) + src[i + 1];
-			if (pointer >= *offset) {
-				/*
-				 * The pointer must indicates a prior
-				 * occurance.
-				 */
-				log_warnx("%s: invalid forward pointer in DHCP "
-				    "Domain Search option compression",
-				    log_procname);
-				return -1;
-			}
-
-			pointed_len = expand_search_domain_name(src, srclen,
-			    &pointer, domain_search);
-			domain_name_len += pointed_len;
+	memset(buf, 0, buflen);
 
-			*offset = i + 2;
-			return domain_name_len;
-		}
-		if (i + label_len + 1 > srclen) {
-			log_warnx("%s: truncated label in DHCP Domain Search "
-			    "option", log_procname);
-			return -1;
-		}
-		/*
-		 * Update the domain name length with the length of the
-		 * current label, plus a trailing dot ('.').
-		 */
-		domain_name_len += label_len + 1;
+	if (srclen >= DHCP_DOMAIN_SEARCH_LEN || strlen(src) == 0 ||
+	    strlen(src) > DHCP_DOMAIN_SEARCH_LEN)
+		return;
 
-		if (strlen(domain_search) + domain_name_len >=
-		    DHCP_DOMAIN_SEARCH_LEN) {
-			log_warnx("%s: domain search list too long",
-			    log_procname);
-			return -1;
-		}
+	dupnames = inputstring = strdup(src);
+	if (inputstring == NULL)
+		fatal("domain name list");
 
-		/* Copy the label found. */
-		memcpy(cursor, src + i + 1, label_len);
-		cursor[label_len] = '.';
-
-		/* Move cursor. */
-		i += label_len + 1;
-		cursor += label_len + 1;
+	count = 0;
+	while ((hn = strsep(&inputstring, " \t")) != NULL) {
+		if (strlen(hn) == 0)
+			continue;
+		if (res_hnok(hn) == 0)
+			goto bad;
+		if (count > 0)
+			strlcat(buf, ", ", buflen);
+		strlcat(buf, "\"", buflen);
+		strlcat(buf, hn, buflen);
+		if (strlcat(buf, "\"", buflen) >= buflen)
+			goto bad;
+		count++;
+		if (count > DHCP_DOMAIN_SEARCH_CNT)
+			goto bad;
 	}
 
-	log_warnx("%s: truncated DHCP Domain Search option", log_procname);
-
-	return -1;
-}
-
-/*
- * Must special case DHO_DOMAIN_SEARCH because it is encoded as described
- * in RFC 1035 section 4.1.4.
- */
-char *
-pretty_print_domain_search(unsigned char *src, size_t srclen)
-{
-	static char	 domain_search[DHCP_DOMAIN_SEARCH_LEN];
-	unsigned char	*cursor;
-	unsigned int	 offset;
-	int		 len, expanded_len, domains;
-
-	memset(domain_search, 0, sizeof(domain_search));
-
-	/* Compute expanded length. */
-	expanded_len = len = 0;
-	domains = 0;
-	offset = 0;
-	while (offset < srclen) {
-		cursor = domain_search + strlen(domain_search);
-		if (domain_search[0] != '\0') {
-			*cursor = ' ';
-			expanded_len++;
-		}
-		len = expand_search_domain_name(src, srclen, &offset,
-		    domain_search);
-		if (len == -1)
-			return NULL;
-		domains++;
-		expanded_len += len;
-		if (domains > DHCP_DOMAIN_SEARCH_CNT)
-			return NULL;
-	}
+	free(dupnames);
+	return;
 
-	return domain_search;
+bad:
+	free(dupnames);
+	memset(buf, 0, buflen);
 }
 
 /*
@@ -812,6 +746,9 @@ pretty_print_option(unsigned int code, struct option_data *option,
 	case DHO_CLASSLESS_MS_STATIC_ROUTES:
 		pretty_print_classless_routes(dp, len, optbuf, sizeof(optbuf));
 		goto done;
+	case DHO_DOMAIN_SEARCH:
+		pretty_print_domain_list(dp, len, optbuf, sizeof(optbuf));
+		goto done;
 	default:
 		break;
 	}