From db6491450361aede405510edf412bc276cce6536 Mon Sep 17 00:00:00 2001 From: Jan Just Keijser Date: Tue, 14 Jul 2020 11:39:10 +0200 Subject: [PATCH] Added support for DHCP option 119 (dns search suffix list) for Windows. As of Windows 10 1809 Windows finally supports this so it makes sense to add support to OpenVPN as well. Signed-off-by: Jan Just Keijser --- src/openvpn/options.c | 24 ++++++++++++++++ src/openvpn/tun.c | 76 +++++++++++++++++++++++++++++++++++++++++++++++++++ src/openvpn/tun.h | 6 ++++ 3 files changed, 106 insertions(+) diff --git a/src/openvpn/options.c b/src/openvpn/options.c index bf2760e..66c72f1 100644 --- a/src/openvpn/options.c +++ b/src/openvpn/options.c @@ -729,6 +729,7 @@ static const char usage_message[] = " which allow multiple addresses,\n" " --dhcp-option must be repeated.\n" " DOMAIN name : Set DNS suffix\n" + " DOMAIN-SEARCH entry : Add entry to DNS domain search list\n" " DNS addr : Set domain name server address(es) (IPv4 and IPv6)\n" " NTP : Set NTP server address(es)\n" " NBDD : Set NBDD server address(es)\n" @@ -1144,6 +1145,16 @@ parse_hash_fingerprint(const char *str, int nbytes, int msglevel, struct gc_aren #ifndef ENABLE_SMALL +static void +show_dhcp_option_list(const char *name, const char * const*array, int len) +{ + int i; + for (i = 0; i < len; ++i) + { + msg(D_SHOW_PARMS, " %s[%d] = %s", name, i, array[i] ); + } +} + static void show_dhcp_option_addrs(const char *name, const in_addr_t *array, int len) { @@ -1179,6 +1190,7 @@ show_tuntap_options(const struct tuntap_options *o) show_dhcp_option_addrs("WINS", o->wins, o->wins_len); show_dhcp_option_addrs("NTP", o->ntp, o->ntp_len); show_dhcp_option_addrs("NBDD", o->nbdd, o->nbdd_len); + show_dhcp_option_list("DOMAIN-SEARCH", o->domain_search_list, o->domain_search_list_len); } #endif /* ifndef ENABLE_SMALL */ @@ -7460,6 +7472,18 @@ add_option(struct options *options, { dhcp_option_address_parse("NBDD", p[2], o->nbdd, &o->nbdd_len, msglevel); } + else if (streq(p[1], "DOMAIN-SEARCH") && p[2]) + { + if (o->domain_search_list_len < N_SEARCH_LIST_LEN) + { + o->domain_search_list[o->domain_search_list_len++] = p[2]; + } + else + { + msg(msglevel, "--dhcp-option %s: maximum of %d search entries can be specified", + p[1], N_SEARCH_LIST_LEN); + } + } else if (streq(p[1], "DISABLE-NBT") && !p[2]) { o->disable_nbt = 1; diff --git a/src/openvpn/tun.c b/src/openvpn/tun.c index 2a2df27..4b772dd 100644 --- a/src/openvpn/tun.c +++ b/src/openvpn/tun.c @@ -5673,6 +5673,75 @@ write_dhcp_str(struct buffer *buf, const int type, const char *str, bool *error) buf_write(buf, str, len); } +/* + * RFC3397 states that multiple searchdomains are encoded as follows: + * - at start the length of the entire option is given + * - each subdomain is preceded by its length + * - each searchdomain is separated by a NUL character + * e.g. if you want "openvpn.net" and "duckduckgo.com" then you end up with + * 0x1D 0x7 openvpn 0x3 net 0x00 0x0A duckduckgo 0x3 com 0x00 + */ +static void +write_dhcp_search_str(struct buffer *buf, const int type, const char * const *str_array, + int array_len, bool *error) +{ + char tmp_buf[256]; + int i; + int len = 0; + int label_length_pos; + + for (i=0; i < array_len; i++) + { + const char *ptr = str_array[i]; + + if (strlen(ptr) + len + 1 > sizeof(tmp_buf)) + { + *error = true; + msg(M_WARN, "write_dhcp_search_str: temp buffer overflow building DHCP options"); + return; + } + /* Loop over all subdomains separated by a dot and replace the dot + with the length of the subdomain */ + + /* label_length_pos points to the byte to be replaced by the length + * of the following domain label */ + label_length_pos = len++; + + while (true) + { + if (*ptr == '.' || *ptr == '\0' ) + { + tmp_buf[label_length_pos] = (len-label_length_pos)-1; + label_length_pos = len; + if (*ptr == '\0') + { + break; + } + } + tmp_buf[len++] = *ptr++; + } + /* And close off with an extra NUL char */ + tmp_buf[len++] = 0; + } + + if (!buf_safe(buf, 2 + len)) + { + *error = true; + msg(M_WARN, "write_search_dhcp_str: buffer overflow building DHCP options"); + return; + } + if (len > 255) + { + *error = true; + msg(M_WARN, "write_dhcp_search_str: search domain string must be <= 255 bytes"); + return; + } + + buf_write_u8(buf, type); + buf_write_u8(buf, len); + buf_write(buf, tmp_buf, len); +} + static bool build_dhcp_options_string(struct buffer *buf, const struct tuntap_options *o) { @@ -5697,6 +5766,13 @@ build_dhcp_options_string(struct buffer *buf, const struct tuntap_options *o) write_dhcp_u32_array(buf, 42, (uint32_t *)o->ntp, o->ntp_len, &error); write_dhcp_u32_array(buf, 45, (uint32_t *)o->nbdd, o->nbdd_len, &error); + if (o->domain_search_list_len > 0) + { + write_dhcp_search_str(buf, 119, o->domain_search_list, + o->domain_search_list_len, + &error); + } + /* the MS DHCP server option 'Disable Netbios-over-TCP/IP * is implemented as vendor option 001, value 002. * A value of 001 means 'leave NBT alone' which is the default */ diff --git a/src/openvpn/tun.h b/src/openvpn/tun.h index b38e7e9..99826cf 100644 --- a/src/openvpn/tun.h +++ b/src/openvpn/tun.h @@ -112,6 +112,12 @@ struct tuntap_options { in_addr_t nbdd[N_DHCP_ADDR]; int nbdd_len; +#define N_SEARCH_LIST_LEN 10 /* Max # of entries in domin-search list */ + + /* SEARCH (119), MacOS, Linux, Win10 1809+ */ + const char *domain_search_list[N_SEARCH_LIST_LEN]; + int domain_search_list_len; + /* DISABLE_NBT (43, Vendor option 001) */ bool disable_nbt; -- 1.8.3.1