From 7ea97a433c3ce62dab3d99f6dbe72a6cb319cd44 Mon Sep 17 00:00:00 2001 From: Hans Dedecker Date: Wed, 13 Nov 2013 16:03:34 +0100 Subject: [PATCH 1/1] Improved message validation checks and socket error hardening --- src/dhcpv6.c | 160 +++++++++++++++++++++++++++++++++----------------- src/odhcp6c.h | 4 -- 2 files changed, 107 insertions(+), 57 deletions(-) diff --git a/src/dhcpv6.c b/src/dhcpv6.c index 1deb10e..9b03227 100644 --- a/src/dhcpv6.c +++ b/src/dhcpv6.c @@ -44,7 +44,8 @@ static bool dhcpv6_response_is_valid(const void *buf, ssize_t len, - const uint8_t transaction[3], enum dhcpv6_msg type); + const uint8_t transaction[3], enum dhcpv6_msg type, + const struct in6_addr *daddr); static int dhcpv6_parse_ia(void *opt, void *end); @@ -99,18 +100,19 @@ static bool accept_reconfig = false; static uint8_t reconf_key[16]; - int init_dhcpv6(const char *ifname, int request_pd, int sol_timeout) { request_prefix = request_pd; dhcpv6_retx[DHCPV6_MSG_SOLICIT].max_timeo = sol_timeout; sock = socket(AF_INET6, SOCK_DGRAM | SOCK_CLOEXEC, IPPROTO_UDP); + if (sock < 0) + return -1; // Detect interface struct ifreq ifr; strncpy(ifr.ifr_name, ifname, sizeof(ifr.ifr_name)); - if (ioctl(sock, SIOCGIFINDEX, &ifr)) + if (ioctl(sock, SIOCGIFINDEX, &ifr) < 0) return -1; ifindex = ifr.ifr_ifindex; @@ -118,10 +120,11 @@ int init_dhcpv6(const char *ifname, int request_pd, int sol_timeout) size_t client_id_len; odhcp6c_get_state(STATE_CLIENT_ID, &client_id_len); if (client_id_len == 0) { - ioctl(sock, SIOCGIFHWADDR, &ifr); uint8_t duid[14] = {0, DHCPV6_OPT_CLIENTID, 0, 10, 0, DHCPV6_DUID_LLADDR, 0, 1}; - memcpy(&duid[8], ifr.ifr_hwaddr.sa_data, ETHER_ADDR_LEN); + + if (ioctl(sock, SIOCGIFHWADDR, &ifr) >= 0) + memcpy(&duid[8], ifr.ifr_hwaddr.sa_data, ETHER_ADDR_LEN); uint8_t zero[ETHER_ADDR_LEN] = {0, 0, 0, 0, 0, 0}; struct ifreq ifs[100], *ifp, *ifend; @@ -134,10 +137,11 @@ int init_dhcpv6(const char *ifname, int request_pd, int sol_timeout) // If our interface doesn't have an address... ifend = ifs + (ifc.ifc_len / sizeof(struct ifreq)); for (ifp = ifc.ifc_req; ifp < ifend && - !memcmp(&duid[8], zero, 6); ifp++) { + !memcmp(&duid[8], zero, ETHER_ADDR_LEN); ifp++) { memcpy(ifr.ifr_name, ifp->ifr_name, sizeof(ifr.ifr_name)); - ioctl(sock, SIOCGIFHWADDR, &ifr); + if (ioctl(sock, SIOCGIFHWADDR, &ifr) < 0) + continue; memcpy(&duid[8], ifr.ifr_hwaddr.sa_data, ETHER_ADDR_LEN); } @@ -153,7 +157,6 @@ int init_dhcpv6(const char *ifname, int request_pd, int sol_timeout) htons(DHCPV6_OPT_DNS_SERVERS), htons(DHCPV6_OPT_DNS_DOMAIN), htons(DHCPV6_OPT_NTP_SERVER), - htons(DHCPV6_OPT_SIP_SERVER_A), htons(DHCPV6_OPT_AFTR_NAME), htons(DHCPV6_OPT_PD_EXCLUDE), #ifdef EXT_PREFIX_CLASS @@ -162,21 +165,31 @@ int init_dhcpv6(const char *ifname, int request_pd, int sol_timeout) }; odhcp6c_add_state(STATE_ORO, oro, sizeof(oro)); + do { + // Configure IPv6-options + int val = 1; + if (setsockopt(sock, IPPROTO_IPV6, IPV6_V6ONLY, &val, sizeof(val)) < 0) + break; + if (setsockopt(sock, SOL_SOCKET, SO_REUSEADDR, &val, sizeof(val)) < 0) + break; + if (setsockopt(sock, IPPROTO_IPV6, IPV6_RECVPKTINFO, &val, sizeof(val)) < 0) + break; + + val = 0; + if (setsockopt(sock, IPPROTO_IPV6, IPV6_MULTICAST_LOOP, &val, sizeof(val)) < 0) + break; + if (setsockopt(sock, SOL_SOCKET, SO_BINDTODEVICE, ifname, strlen(ifname)) < 0) + break; - // Configure IPv6-options - int val = 1; - setsockopt(sock, IPPROTO_IPV6, IPV6_V6ONLY, &val, sizeof(val)); - setsockopt(sock, SOL_SOCKET, SO_REUSEADDR, &val, sizeof(val)); - val = 0; - setsockopt(sock, IPPROTO_IPV6, IPV6_MULTICAST_LOOP, &val, sizeof(val)); - setsockopt(sock, SOL_SOCKET, SO_BINDTODEVICE, ifname, strlen(ifname)); + struct sockaddr_in6 client_addr = { .sin6_family = AF_INET6, + .sin6_port = htons(DHCPV6_CLIENT_PORT), .sin6_flowinfo = 0 }; + if (bind(sock, (struct sockaddr*)&client_addr, sizeof(client_addr)) < 0) + break; - struct sockaddr_in6 client_addr = { .sin6_family = AF_INET6, - .sin6_port = htons(DHCPV6_CLIENT_PORT), .sin6_flowinfo = 0 }; - if (bind(sock, (struct sockaddr*)&client_addr, sizeof(client_addr))) - return -1; + return 0; + } while (0); - return 0; + return -1; } @@ -372,7 +385,7 @@ static int64_t dhcpv6_rand_delay(int64_t time) int dhcpv6_request(enum dhcpv6_msg type) { - uint8_t buf[1536], rc = 0; + uint8_t rc = 0; uint64_t timeout = UINT32_MAX; struct dhcpv6_retx *retx = &dhcpv6_retx[type]; @@ -441,6 +454,12 @@ int dhcpv6_request(enum dhcpv6_msg type) // Receive rounds for (; len < 0 && round_start < round_end; round_start = odhcp6c_get_milli_time()) { + uint8_t buf[1536], cmsg_buf[CMSG_SPACE(sizeof(struct in6_pktinfo))]; + struct iovec iov = {buf, sizeof(buf)}; + struct msghdr msg = {NULL, 0, &iov, 1, + cmsg_buf, sizeof(cmsg_buf), 0}; + struct in6_pktinfo *pktinfo = NULL; + // Check for pending signal if (odhcp6c_signal_process()) return -1; @@ -452,27 +471,43 @@ int dhcpv6_request(enum dhcpv6_msg type) &timeout, sizeof(timeout)); // Receive cycle - len = recv(sock, buf, sizeof(buf), 0); + len = recvmsg(sock, &msg, 0); + if (len < 0) + continue; + + for (struct cmsghdr *ch = CMSG_FIRSTHDR(&msg); ch != NULL; + ch = CMSG_NXTHDR(&msg, ch)) { + if (ch->cmsg_level == SOL_IPV6 && + ch->cmsg_type == IPV6_PKTINFO) { + pktinfo = (struct in6_pktinfo *)CMSG_DATA(ch); + break; + } + } + + if (pktinfo == NULL) { + len = -1; + continue; + } - if (!dhcpv6_response_is_valid(buf, len, trid, type)) + if (!dhcpv6_response_is_valid(buf, len, trid, + type, &pktinfo->ipi6_addr)) { len = -1; + continue; + } - if (len > 0) { - uint8_t *opt = &buf[4]; - uint8_t *opt_end = opt + len - 4; + uint8_t *opt = &buf[4]; + uint8_t *opt_end = opt + len - 4; - round_start = odhcp6c_get_milli_time(); - elapsed = round_start - start; - syslog(LOG_NOTICE, "Got a valid reply after " - "%llums", (unsigned long long)elapsed); + round_start = odhcp6c_get_milli_time(); + elapsed = round_start - start; + syslog(LOG_NOTICE, "Got a valid reply after " + "%llums", (unsigned long long)elapsed); - if (retx->handler_reply) - len = retx->handler_reply( - type, rc, opt, opt_end); + if (retx->handler_reply) + len = retx->handler_reply(type, rc, opt, opt_end); - if (len > 0 && round_end - round_start > 1000) - round_end = 1000 + round_start; - } + if (len > 0 && round_end - round_start > 1000) + round_end = 1000 + round_start; } // Allow @@ -483,9 +518,10 @@ int dhcpv6_request(enum dhcpv6_msg type) return len; } - +// Message validation checks according to RFC3315 chapter 15 static bool dhcpv6_response_is_valid(const void *buf, ssize_t len, - const uint8_t transaction[3], enum dhcpv6_msg type) + const uint8_t transaction[3], enum dhcpv6_msg type, + const struct in6_addr *daddr) { const struct dhcpv6_header *rep = buf; if (len < (ssize_t)sizeof(*rep) || memcmp(rep->tr_id, @@ -503,9 +539,11 @@ static bool dhcpv6_response_is_valid(const void *buf, ssize_t len, return false; } - uint8_t *end = ((uint8_t*)buf) + len, *odata; + uint8_t *end = ((uint8_t*)buf) + len, *odata, + rcmsg = DHCPV6_MSG_UNKNOWN; uint16_t otype, olen; - bool clientid_ok = false, serverid_ok = false, rcauth_ok = false; + bool clientid_ok = false, serverid_ok = false, rcauth_ok = false, + ia_present = false, options_valid = true; size_t client_id_len, server_id_len; void *client_id = odhcp6c_get_state(STATE_CLIENT_ID, &client_id_len); @@ -516,8 +554,11 @@ static bool dhcpv6_response_is_valid(const void *buf, ssize_t len, clientid_ok = (olen + 4U == client_id_len) && !memcmp( &odata[-4], client_id, client_id_len); } else if (otype == DHCPV6_OPT_SERVERID) { - serverid_ok = (olen + 4U == server_id_len) && !memcmp( - &odata[-4], server_id, server_id_len); + if (server_id_len) + serverid_ok = (olen + 4U == server_id_len) && !memcmp( + &odata[-4], server_id, server_id_len); + else + serverid_ok = true; } else if (otype == DHCPV6_OPT_AUTH && olen == -4 + sizeof(struct dhcpv6_auth_reconfigure)) { struct dhcpv6_auth_reconfigure *r = (void*)&odata[-4]; @@ -549,13 +590,34 @@ static bool dhcpv6_response_is_valid(const void *buf, ssize_t len, md5_finish(&md5, hash); rcauth_ok = !memcmp(hash, serverhash, sizeof(hash)); + } else if (otype == DHCPV6_OPT_RECONF_MESSAGE && olen == 1) { + rcmsg = odata[0]; + } else if ((otype == DHCPV6_OPT_IA_PD || otype == DHCPV6_OPT_IA_NA)) { + ia_present = true; + if (olen < sizeof(struct dhcpv6_ia_hdr)) + options_valid = false; + } + else if ((otype == DHCPV6_OPT_IA_ADDR) || (otype == DHCPV6_OPT_IA_PREFIX) || + (otype == DHCPV6_OPT_PD_EXCLUDE)) { + // Options are not allowed on global level + options_valid = false; } } - if (rep->msg_type == DHCPV6_MSG_RECONF && !rcauth_ok) + if (!options_valid) return false; - return clientid_ok && (serverid_ok || server_id_len == 0); + if (type == DHCPV6_MSG_INFO_REQ && ia_present) + return false; + + if (rep->msg_type == DHCPV6_MSG_RECONF) { + if ((rcmsg != DHCPV6_MSG_RENEW && rcmsg != DHCPV6_MSG_INFO_REQ) || + (rcmsg == DHCPV6_MSG_INFO_REQ && ia_present) || + !rcauth_ok || IN6_IS_ADDR_MULTICAST(daddr)) + return false; + } + + return clientid_ok && serverid_ok; } @@ -572,7 +634,6 @@ int dhcpv6_poll_reconfigure(void) static int dhcpv6_handle_reconfigure(_unused enum dhcpv6_msg orig, const int rc, const void *opt, const void *end) { - // TODO: should verify the reconfigure message uint16_t otype, olen; uint8_t *odata, msg = DHCPV6_MSG_RENEW; dhcpv6_for_each_option(opt, end, otype, olen, odata) @@ -673,11 +734,6 @@ static int dhcpv6_handle_advert(enum dhcpv6_msg orig, const int rc, odhcp6c_add_state(STATE_SERVER_CAND, &cand, sizeof(cand)); } - if (orig == DHCPV6_MSG_SOLICIT) { - odhcp6c_clear_state(STATE_IA_NA); - odhcp6c_clear_state(STATE_IA_PD); - } - return (rc > 1 || (pref == 255 && cand.preference > 0)) ? 1 : -1; } @@ -734,10 +790,8 @@ static int dhcpv6_handle_rebind_reply(enum dhcpv6_msg orig, const int rc, const void *opt, const void *end) { dhcpv6_handle_advert(orig, rc, opt, end); - if (dhcpv6_commit_advert() < 0) { - dhcpv6_handle_reply(DHCPV6_MSG_UNKNOWN, rc, NULL, NULL); + if (dhcpv6_commit_advert() < 0) return -1; - } return dhcpv6_handle_reply(orig, rc, opt, end); } diff --git a/src/odhcp6c.h b/src/odhcp6c.h index 183ed44..1a4fbce 100644 --- a/src/odhcp6c.h +++ b/src/odhcp6c.h @@ -21,10 +21,6 @@ #define ARRAY_SIZE(arr) (sizeof(arr) / sizeof((arr)[0])) -#ifndef SOL_NETLINK -#define SOL_NETLINK 270 -#endif - #define ND_OPT_RECURSIVE_DNS 25 #define ND_OPT_DNSSL 31 -- 2.39.2