According to RFC 2132, 2. BOOTP Extension/DHCP Option Field Format

ASCII data should not include trailing NUL but we MUST delete trailing
NULs on receiving.

Jan Vlach ( janus AT volny.cz) reported that Microsoft DHCP server
sends the domain name option with a trailing NUL which the installer
put into /etc/myname as a trailing ^@ which smtpd does not like.

Fix some whitespace while here.

Input & OK millert

diff --git a/sbin/dhcpleased/engine.c b/sbin/dhcpleased/engine.c
index fa25fbb..ae3f467 100644 (file)
--- a/sbin/dhcpleased/engine.c
+++ b/sbin/dhcpleased/engine.c
@@ -1,4 +1,4 @@
-/*     $OpenBSD: engine.c,v 1.35 2022/01/04 06:20:37 florian Exp $     */
+/*     $OpenBSD: engine.c,v 1.36 2022/02/16 10:35:57 florian Exp $     */
 
 /*
  * Copyright (c) 2017, 2021 Florian Obser <florian@openbsd.org>
@@ -727,7 +727,7 @@ parse_dhcp(struct dhcpleased_iface *iface, struct imsg_dhcp *dhcp)
        size_t                   rem, i;
        uint32_t                 sum, usum, lease_time = 0, renewal_time = 0;
        uint32_t                 rebinding_time = 0;
-       uint8_t                 *p, dho = DHO_PAD, dho_len;
+       uint8_t                 *p, dho = DHO_PAD, dho_len, slen;
        uint8_t                  dhcp_message_type = 0;
        int                      routes_len = 0, routers = 0, csr = 0;
        char                     from[sizeof("xx:xx:xx:xx:xx:xx")];
@@ -1014,18 +1014,30 @@ parse_dhcp(struct dhcpleased_iface *iface, struct imsg_dhcp *dhcp)
                        rem -= dho_len;
                        break;
                case DHO_HOST_NAME:
-                       if ( dho_len < 1)
+                       if (dho_len < 1)
                                goto wrong_length;
-                       strvisx(hostname, p, dho_len, VIS_SAFE);
+                       /* MUST delete trailing NUL, per RFC 2132 */
+                       slen = dho_len;
+                       while (slen > 0 && p[slen - 1] == '\0')
+                               slen--;
+                       if (slen < 1)
+                               goto wrong_length;
+                       strvisx(hostname, p, slen, VIS_SAFE);
                        if (log_getverbose() > 1)
                                log_debug("DHO_HOST_NAME: %s", hostname);
                        p += dho_len;
                        rem -= dho_len;
                        break;
                case DHO_DOMAIN_NAME:
-                       if ( dho_len < 1)
+                       if (dho_len < 1)
+                               goto wrong_length;
+                       /* MUST delete trailing NUL, per RFC 2132 */
+                       slen = dho_len;
+                       while (slen > 0 && p[slen - 1] == '\0')
+                               slen--;
+                       if (slen < 1)
                                goto wrong_length;
-                       strvisx(domainname, p, dho_len, VIS_SAFE);
+                       strvisx(domainname, p, slen, VIS_SAFE);
                        if (log_getverbose() > 1)
                                log_debug("DHO_DOMAIN_NAME: %s", domainname);
                        p += dho_len;