Improved message validation checks and socket error hardening
authorHans Dedecker <hans.dedecker@technicolor.com>
Wed, 13 Nov 2013 15:03:34 +0000 (16:03 +0100)
committerHans Dedecker <hans.dedecker@technicolor.com>
Wed, 13 Nov 2013 15:03:34 +0000 (16:03 +0100)
src/dhcpv6.c
src/odhcp6c.h

index 1deb10e..9b03227 100644 (file)
@@ -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);
 }
index 183ed44..1a4fbce 100644 (file)
 
 #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