The UPnP Device Architecture spec provides a way for devices to connect back to control points, called "Eventing" (chapter 4). This sequence can look something like: 1) Outbound multicast M-SEARCH packet (dst: 1900/udp) - Create expectation for unicast reply from <any host> to source port 2) Inbound unicast reply (there may be several of these from different devices) - Find the device's URL, e.g. LOCATION: http://192.168.1.123:1400/xml/device_description.xml - Create expectation to track connections to this host:port (tcp) 3) Outbound connection to device's web server (there will be several of these) - Watch for a SUBSCRIBE request - Find the control point's callback URL, e.g. CALLBACK: <http://192.168.1.124:3500/notify> - Create expectation to open up inbound connections to this host:port 4) Inbound connection to control point's web server - Once this is complete, the subscription should work Add the necessary code to add expectations for each of these connections and rewrite the IP in the CALLBACK URL. Signed-off-by: Kevin Cernekee <cernekee@xxxxxxxxxxxx> --- This needs more testing on my end, so I'm posting it as an RFC to solicit preliminary feedback. doc/helper/conntrackd.conf | 10 +- src/helpers/ssdp.c | 400 ++++++++++++++++++++++++++++++++++++++++++++- 2 files changed, 403 insertions(+), 7 deletions(-) diff --git a/doc/helper/conntrackd.conf b/doc/helper/conntrackd.conf index 5c07509..ec24e2a 100644 --- a/doc/helper/conntrackd.conf +++ b/doc/helper/conntrackd.conf @@ -74,7 +74,15 @@ Helper { QueueNum 5 QueueLen 10240 Policy ssdp { - ExpectMax 1 + ExpectMax 8 + ExpectTimeout 300 + } + } + Type ssdp inet tcp { + QueueNum 5 + QueueLen 10240 + Policy ssdp { + ExpectMax 8 ExpectTimeout 300 } } diff --git a/src/helpers/ssdp.c b/src/helpers/ssdp.c index bc41087..d9c9a5a 100644 --- a/src/helpers/ssdp.c +++ b/src/helpers/ssdp.c @@ -1,5 +1,5 @@ /* - * SSDP connection tracking helper + * SSDP/UPnP connection tracking helper * (SSDP = Simple Service Discovery Protocol) * For documentation about SSDP see * http://en.wikipedia.org/wiki/Simple_Service_Discovery_Protocol @@ -8,6 +8,18 @@ * Based on the SSDP conntrack helper (nf_conntrack_ssdp.c), * :http://marc.info/?t=132945775100001&r=1&w=2 * (C) 2012 Ian Pilcher <arequipeno@xxxxxxxxx> + * Copyright (C) 2016 Google Inc. + * + * This requires Linux 3.12 or higher. Usage: + * + * nfct add helper ssdp inet udp + * nfct add helper ssdp inet tcp + * iptables -t raw -A OUTPUT -p udp --dport 1900 -j CT --helper ssdp + * iptables -t raw -A PREROUTING -p udp --dport 1900 -j CT --helper ssdp + * + * This helper supports SNAT when used in conjunction with a daemon that + * forwards SSDP broadcasts/replies between interfaces, e.g. + * https://chromium.googlesource.com/chromiumos/platform2/+/master/arc-networkd/multicast_forwarder.h * * This program is free software; you can redistribute it and/or modify * it under the terms of the GNU General Public License version 2 as @@ -19,8 +31,10 @@ #include "myct.h" #include "log.h" #include <errno.h> +#include <stdlib.h> #include <arpa/inet.h> #include <netinet/ip.h> +#include <netinet/tcp.h> #include <netinet/udp.h> #include <libmnl/libmnl.h> #include <libnetfilter_conntrack/libnetfilter_conntrack.h> @@ -36,8 +50,94 @@ #define SSDP_M_SEARCH "M-SEARCH" #define SSDP_M_SEARCH_SIZE (sizeof SSDP_M_SEARCH - 1) -static int ssdp_helper_cb(struct pkt_buff *pkt, uint32_t protoff, - struct myct *myct, uint32_t ctinfo) +/* So, this packet has hit the connection tracking matching code. + Mangle it, and change the expectation to match the new version. */ +static unsigned int nf_nat_ssdp(struct pkt_buff *pkt, + int ctinfo, + unsigned int matchoff, + unsigned int matchlen, + struct nf_conntrack *ct, + struct nf_expect *exp) +{ + union nfct_attr_grp_addr newip; + uint16_t port; + int dir = CTINFO2DIR(ctinfo); + char buffer[sizeof("255.255.255.255:65535")]; + unsigned int buflen; + const struct nf_conntrack *expected; + struct nf_conntrack *nat_tuple; + uint16_t initial_port; + + /* Connection will come from wherever this packet goes, hence !dir */ + cthelper_get_addr_dst(ct, !dir, &newip); + + expected = nfexp_get_attr(exp, ATTR_EXP_EXPECTED); + + nat_tuple = nfct_new(); + if (nat_tuple == NULL) + return NF_ACCEPT; + + initial_port = nfct_get_attr_u16(expected, ATTR_PORT_DST); + + nfexp_set_attr_u32(exp, ATTR_EXP_NAT_DIR, !dir); + + /* libnetfilter_conntrack needs this */ + nfct_set_attr_u8(nat_tuple, ATTR_L3PROTO, AF_INET); + nfct_set_attr_u32(nat_tuple, ATTR_IPV4_SRC, 0); + nfct_set_attr_u32(nat_tuple, ATTR_IPV4_DST, 0); + nfct_set_attr_u8(nat_tuple, ATTR_L4PROTO, + nfct_get_attr_u8(ct, ATTR_L4PROTO)); + nfct_set_attr_u16(nat_tuple, ATTR_PORT_DST, 0); + + /* When you see the packet, we need to NAT it the same as the + this one. */ + nfexp_set_attr(exp, ATTR_EXP_FN, "nat-follow-master"); + + /* Try to get same port: if not, try to change it. */ + for (port = ntohs(initial_port); port != 0; port++) { + int ret; + + nfct_set_attr_u16(nat_tuple, ATTR_PORT_SRC, htons(port)); + nfexp_set_attr(exp, ATTR_EXP_NAT_TUPLE, nat_tuple); + + ret = cthelper_add_expect(exp); + if (ret == 0) + break; + else if (ret != -EBUSY) { + port = 0; + break; + } + } + + if (port == 0) + return NF_DROP; + + /* Only the SUBSCRIBE request contains an IP string that needs to be + mangled. */ + if (!matchoff) + return NF_ACCEPT; + + buflen = snprintf(buffer, sizeof(buffer), + "%u.%u.%u.%u:%u", + ((unsigned char *)&newip.ip)[0], + ((unsigned char *)&newip.ip)[1], + ((unsigned char *)&newip.ip)[2], + ((unsigned char *)&newip.ip)[3], port); + if (!buflen) + goto out; + + if (!nfq_tcp_mangle_ipv4(pkt, matchoff, matchlen, buffer, buflen)) + goto out; + + return NF_ACCEPT; + +out: + cthelper_del_expect(exp); + return NF_DROP; +} + +static int handle_ssdp_new(struct pkt_buff *pkt, uint32_t protoff, + struct myct *myct, uint32_t ctinfo) { int ret = NF_ACCEPT; union nfct_attr_grp_addr daddr, saddr, taddr; @@ -109,12 +209,285 @@ static int ssdp_helper_cb(struct pkt_buff *pkt, uint32_t protoff, nfexp_destroy(exp); return NF_DROP; } + nfexp_set_attr(exp, ATTR_EXP_HELPER_NAME, "ssdp"); + if (nfct_get_attr_u32(myct->ct, ATTR_STATUS) & IPS_SRC_NAT) + return nf_nat_ssdp(pkt, ctinfo, 0, 0, myct->ct, exp); + myct->exp = exp; return ret; } -static struct ctd_helper ssdp_helper = { +static int find_hdr(const char *name, const uint8_t *data, int data_len, + char *val, int val_len, const uint8_t **pos) +{ + int name_len = strlen(name); + int i; + + while (1) { + if (data_len < name_len + 2) + return -1; + + if (strncasecmp(name, (char *)data, name_len) == 0) + break; + + for (i = 0; ; i++) { + if (i >= data_len - 1) + return -1; + if (data[i] == '\r' && data[i+1] == '\n') + break; + } + + data_len -= i+2; + data += i+2; + } + + data_len -= name_len; + data += name_len; + if (pos) + *pos = data; + + for (i = 0; ; i++, val_len--) { + if (!val_len) + return -1; + if (*data == '\r') { + *val = 0; + return 0; + } + *(val++) = *(data++); + } +} + +static int parse_url(const char *url, + uint8_t l3proto, + union nfct_attr_grp_addr *addr, + uint16_t *port, + size_t *match_offset, + size_t *match_len) +{ + const char *start = url, *end; + size_t ip_len; + + if (strncasecmp(url, "http://[";, 8) == 0) { + char buf[64] = {0}; + + if (l3proto != AF_INET6) { + pr_debug("conntrack_ssdp: IPv6 URL in IPv4 SSDP reply\n"); + return -1; + } + + url += 8; + + end = strchr(url, ']'); + if (!end) { + pr_debug("conntrack_ssdp: unterminated IPv6 address: '%s'\n", url); + return -1; + } + + ip_len = end - url; + if (ip_len > sizeof(buf) - 1) { + pr_debug("conntrack_ssdp: IPv6 address too long: '%s'\n", url); + return -1; + } + strncpy(buf, url, ip_len); + + if (inet_pton(AF_INET6, buf, addr) != 1) { + pr_debug("conntrack_ssdp: Error parsing IPv6 address: '%s'\n", buf); + return -1; + } + } else if (strncasecmp(url, "http://";, 7) == 0) { + char buf[64] = {0}; + + if (l3proto != AF_INET) { + pr_debug("conntrack_ssdp: IPv4 URL in IPv6 SSDP reply\n"); + return -1; + } + + url += 7; + for (end = url; ; end++) { + if (*end != '.' && *end != '\0' && + (*end < '0' || *end > '9')) + break; + } + + ip_len = end - url; + if (ip_len > sizeof(buf) - 1) { + pr_debug("conntrack_ssdp: IPv4 address too long: '%s'\n", url); + return -1; + } + strncpy(buf, url, ip_len); + + if (inet_pton(AF_INET, buf, addr) != 1) { + pr_debug("conntrack_ssdp: Error parsing IPv4 address: '%s'\n", buf); + return -1; + } + } else { + pr_debug("conntrack_ssdp: header does not start with http://\n";); + return -1; + } + + if (match_offset) + *match_offset = url - start; + + if (*end != ':') { + *port = htons(80); + if (match_len) + *match_len = ip_len; + } else { + char *endptr = NULL; + *port = htons(strtol(end + 1, &endptr, 10)); + if (match_len) + *match_len = ip_len + endptr - end;; + } + + return 0; +} + +static int handle_ssdp_reply(struct pkt_buff *pkt, uint32_t protoff, + struct myct *myct, uint32_t ctinfo) +{ + uint8_t *data = pktb_network_header(pkt); + size_t bytes_left = pktb_len(pkt); + char hdr_val[256]; + union nfct_attr_grp_addr addr; + uint16_t port; + struct nf_expect *exp = NULL; + + if (bytes_left < protoff + sizeof(struct udphdr)) { + pr_debug("conntrack_ssdp: Short packet\n"); + return NF_ACCEPT; + } + bytes_left -= protoff + sizeof(struct udphdr); + data += protoff + sizeof(struct udphdr); + + if (find_hdr("LOCATION: ", data, bytes_left, + hdr_val, sizeof(hdr_val), NULL) < 0) { + pr_debug("conntrack_ssdp: No LOCATION header found\n"); + return NF_ACCEPT; + } + pr_debug("conntrack_ssdp: found location URL `%s'\n", hdr_val); + + if (parse_url(hdr_val, nfct_get_attr_u8(myct->ct, ATTR_L3PROTO), + &addr, &port, NULL, NULL) < 0) { + pr_debug("conntrack_ssdp: Error parsing URL\n"); + return NF_ACCEPT; + } + + exp = nfexp_new(); + if (cthelper_expect_init(exp, + myct->ct, + 0 /* class */, + NULL /* saddr */, + &addr /* daddr */, + IPPROTO_TCP, + NULL /* sport */, + &port /* dport */, + NF_CT_EXPECT_PERMANENT /* flags */) < 0) { + pr_debug("conntrack_ssdp: Failed to init expectation\n"); + nfexp_destroy(exp); + return NF_ACCEPT; + } + + nfexp_set_attr(exp, ATTR_EXP_HELPER_NAME, "ssdp"); + if (nfct_get_attr_u32(myct->ct, ATTR_STATUS) & IPS_SRC_NAT) + return nf_nat_ssdp(pkt, ctinfo, 0, 0, myct->ct, exp); + + myct->exp = exp; + return NF_ACCEPT; +} + +static int handle_http_request(struct pkt_buff *pkt, uint32_t protoff, + struct myct *myct, uint32_t ctinfo) +{ + struct tcphdr *th; + unsigned int dataoff, datalen; + const uint8_t *data; + char hdr_val[256]; + union nfct_attr_grp_addr cbaddr = {0}, daddr = {0}, saddr = {0}; + uint16_t cbport; + struct nf_expect *exp = NULL; + const uint8_t *hdr_pos; + size_t ip_offset, ip_len; + int dir = CTINFO2DIR(ctinfo); + + th = (struct tcphdr *) (pktb_network_header(pkt) + protoff); + dataoff = protoff + th->doff * 4; + datalen = pktb_len(pkt) - dataoff; + data = pktb_network_header(pkt) + dataoff; + + if (datalen < 10 || strncmp((char *)data, "SUBSCRIBE ", 10) != 0) + return NF_ACCEPT; + + if (find_hdr("CALLBACK: <", data, datalen, + hdr_val, sizeof(hdr_val), &hdr_pos) < 0) { + pr_debug("conntrack_ssdp: No CALLBACK header found\n"); + return NF_ACCEPT; + } + pr_debug("conntrack_ssdp: found callback URL `%s'\n", hdr_val); + + if (parse_url(hdr_val, nfct_get_attr_u8(myct->ct, ATTR_L3PROTO), + &cbaddr, &cbport, &ip_offset, &ip_len) < 0) { + pr_debug("conntrack_ssdp: Error parsing URL\n"); + return NF_ACCEPT; + } + + cthelper_get_addr_dst(myct->ct, !dir, &daddr); + cthelper_get_addr_src(myct->ct, dir, &saddr); + + if (memcmp(&saddr, &cbaddr, sizeof(cbaddr)) != 0) { + pr_debug("conntrack_ssdp: Callback address belongs to another host\n"); + return NF_ACCEPT; + } + + cthelper_get_addr_src(myct->ct, !dir, &saddr); + + exp = nfexp_new(); + if (cthelper_expect_init(exp, + myct->ct, + 0 /* class */, + &saddr /* saddr */, + &daddr /* daddr */, + IPPROTO_TCP, + NULL /* sport */, + &cbport /* dport */, + NF_CT_EXPECT_PERMANENT /* flags */) < 0) { + pr_debug("conntrack_ssdp: Failed to init expectation\n"); + nfexp_destroy(exp); + return NF_ACCEPT; + } + + if (nfct_get_attr_u32(myct->ct, ATTR_STATUS) & IPS_SRC_NAT) { + return nf_nat_ssdp(pkt, ctinfo, + (hdr_pos - data) + ip_offset, + ip_len, myct->ct, exp); + } + + myct->exp = exp; + return NF_ACCEPT; +} + +static int ssdp_helper_cb(struct pkt_buff *pkt, uint32_t protoff, + struct myct *myct, uint32_t ctinfo) +{ + uint8_t proto; + + if (ctinfo == IP_CT_NEW) + return handle_ssdp_new(pkt, protoff, myct, ctinfo); + + proto = nfct_get_attr_u16(myct->ct, ATTR_ORIG_L4PROTO); + if (proto == IPPROTO_UDP) + return handle_ssdp_reply(pkt, protoff, myct, ctinfo); + else { + if (ctinfo == IP_CT_ESTABLISHED) + return handle_http_request(pkt, protoff, myct, ctinfo); + else + return NF_ACCEPT; + } + + return NF_DROP; +} + +static struct ctd_helper ssdp_helper_udp = { .name = "ssdp", .l4proto = IPPROTO_UDP, .priv_data_len = 0, @@ -122,7 +495,21 @@ static struct ctd_helper ssdp_helper = { .policy = { [0] = { .name = "ssdp", - .expect_max = 1, + .expect_max = 8, + .expect_timeout = 5 * 60, + }, + }, +}; + +static struct ctd_helper ssdp_helper_tcp = { + .name = "ssdp", + .l4proto = IPPROTO_TCP, + .priv_data_len = 0, + .cb = ssdp_helper_cb, + .policy = { + [0] = { + .name = "ssdp", + .expect_max = 8, .expect_timeout = 5 * 60, }, }, @@ -130,5 +517,6 @@ static struct ctd_helper ssdp_helper = { static void __attribute__ ((constructor)) ssdp_init(void) { - helper_register(&ssdp_helper); + helper_register(&ssdp_helper_udp); + helper_register(&ssdp_helper_tcp); } -- 1.9.1 -- To unsubscribe from this list: send the line "unsubscribe netfilter-devel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
