From cddf4d81eacfc81cf761619fcb67bc07a744a6d1 Mon Sep 17 00:00:00 2001 From: Tom Gundersen Date: Mon, 23 Nov 2015 15:59:58 +0100 Subject: sd-ndisc: better validate RA packets Verify the hoplimit and that the received packet is large enough for the RA header. See . --- src/libsystemd-network/icmp6-util.c | 24 +++++++-------- src/libsystemd-network/sd-ndisc.c | 58 ++++++++++++++++++++++++++++++------- 2 files changed, 58 insertions(+), 24 deletions(-) diff --git a/src/libsystemd-network/icmp6-util.c b/src/libsystemd-network/icmp6-util.c index 03505fc47b..acad9d7d6a 100644 --- a/src/libsystemd-network/icmp6-util.c +++ b/src/libsystemd-network/icmp6-util.c @@ -47,17 +47,15 @@ int icmp6_bind_router_solicitation(int index) { .ipv6mr_interface = index, }; _cleanup_close_ int s = -1; - int r, zero = 0, hops = 255; + int r, zero = 0, one = 1, hops = 255; - s = socket(AF_INET6, SOCK_RAW | SOCK_CLOEXEC | SOCK_NONBLOCK, - IPPROTO_ICMPV6); + s = socket(AF_INET6, SOCK_RAW | SOCK_CLOEXEC | SOCK_NONBLOCK, IPPROTO_ICMPV6); if (s < 0) return -errno; ICMP6_FILTER_SETBLOCKALL(&filter); ICMP6_FILTER_SETPASS(ND_ROUTER_ADVERT, &filter); - r = setsockopt(s, IPPROTO_ICMPV6, ICMP6_FILTER, &filter, - sizeof(filter)); + r = setsockopt(s, IPPROTO_ICMPV6, ICMP6_FILTER, &filter, sizeof(filter)); if (r < 0) return -errno; @@ -65,23 +63,23 @@ int icmp6_bind_router_solicitation(int index) { IPV6_PKTINFO socket option also applies for ICMPv6 multicast. Empirical experiments indicates otherwise and therefore an IPV6_MULTICAST_IF socket option is used here instead */ - r = setsockopt(s, IPPROTO_IPV6, IPV6_MULTICAST_IF, &index, - sizeof(index)); + r = setsockopt(s, IPPROTO_IPV6, IPV6_MULTICAST_IF, &index, sizeof(index)); if (r < 0) return -errno; - r = setsockopt(s, IPPROTO_IPV6, IPV6_MULTICAST_LOOP, &zero, - sizeof(zero)); + r = setsockopt(s, IPPROTO_IPV6, IPV6_MULTICAST_LOOP, &zero, sizeof(zero)); if (r < 0) return -errno; - r = setsockopt(s, IPPROTO_IPV6, IPV6_MULTICAST_HOPS, &hops, - sizeof(hops)); + r = setsockopt(s, IPPROTO_IPV6, IPV6_MULTICAST_HOPS, &hops, sizeof(hops)); if (r < 0) return -errno; - r = setsockopt(s, IPPROTO_IPV6, IPV6_ADD_MEMBERSHIP, &mreq, - sizeof(mreq)); + r = setsockopt(s, IPPROTO_IPV6, IPV6_ADD_MEMBERSHIP, &mreq, sizeof(mreq)); + if (r < 0) + return -errno; + + r = setsockopt(s, SOL_IPV6, IPV6_RECVHOPLIMIT, &one, sizeof(one)); if (r < 0) return -errno; diff --git a/src/libsystemd-network/sd-ndisc.c b/src/libsystemd-network/sd-ndisc.c index 249586f048..f2bce3b99f 100644 --- a/src/libsystemd-network/sd-ndisc.c +++ b/src/libsystemd-network/sd-ndisc.c @@ -418,8 +418,7 @@ static int ndisc_prefix_update(sd_ndisc *nd, ssize_t len, return 0; } -static int ndisc_ra_parse(sd_ndisc *nd, struct nd_router_advert *ra, - ssize_t len) { +static int ndisc_ra_parse(sd_ndisc *nd, struct nd_router_advert *ra, ssize_t len) { void *opt; struct nd_opt_hdr *opt_hdr; @@ -482,12 +481,25 @@ static int ndisc_ra_parse(sd_ndisc *nd, struct nd_router_advert *ra, static int ndisc_router_advertisment_recv(sd_event_source *s, int fd, uint32_t revents, void *userdata) { _cleanup_free_ struct nd_router_advert *ra = NULL; sd_ndisc *nd = userdata; - int r, buflen = 0, pref, stateful; - union sockaddr_union router = {}; - socklen_t router_len = sizeof(router); + union { + struct cmsghdr cmsghdr; + uint8_t buf[CMSG_LEN(sizeof(int))]; + } control = {}; + struct iovec iov = {}; + union sockaddr_union sa = {}; + struct msghdr msg = { + .msg_name = &sa.sa, + .msg_namelen = sizeof(sa), + .msg_iov = &iov, + .msg_iovlen = 1, + .msg_control = &control, + .msg_controllen = sizeof(control), + }; + struct cmsghdr *cmsg; struct in6_addr *gw; unsigned lifetime; ssize_t len; + int r, pref, stateful, buflen = 0; assert(s); assert(nd); @@ -500,24 +512,48 @@ static int ndisc_router_advertisment_recv(sd_event_source *s, int fd, uint32_t r /* This really should not happen */ return -EIO; - ra = malloc(buflen); + iov.iov_len = buflen; + + ra = malloc(iov.iov_len); if (!ra) return -ENOMEM; - len = recvfrom(fd, ra, buflen, 0, &router.sa, &router_len); + iov.iov_base = ra; + + len = recvmsg(fd, &msg, 0); if (len < 0) { if (errno == EAGAIN || errno == EINTR) return 0; log_ndisc(nd, "Could not receive message from ICMPv6 socket: %m"); return -errno; - } else if (router_len == 0) + } else if ((size_t)len < sizeof(struct nd_router_advert)) { + return 0; + } else if (msg.msg_namelen == 0) gw = NULL; /* only happens when running the test-suite over a socketpair */ - else if (router_len != sizeof(router.in6)) { - log_ndisc(nd, "Received invalid source address size from ICMPv6 socket: %zu bytes", (size_t)router_len); + else if (msg.msg_namelen != sizeof(sa.in6)) { + log_ndisc(nd, "Received invalid source address size from ICMPv6 socket: %zu bytes", (size_t)msg.msg_namelen); return 0; } else - gw = &router.in6.sin6_addr; + gw = &sa.in6.sin6_addr; + + assert(!(msg.msg_flags & MSG_CTRUNC)); + assert(!(msg.msg_flags & MSG_TRUNC)); + + CMSG_FOREACH(cmsg, &msg) { + if (cmsg->cmsg_level == SOL_IPV6 && + cmsg->cmsg_type == IPV6_HOPLIMIT && + cmsg->cmsg_len == CMSG_LEN(sizeof(int))) { + int hops = *(int*)CMSG_DATA(cmsg); + + if (hops != 255) { + log_ndisc(nd, "Received RA with invalid hop limit %d. Ignoring.", hops); + return 0; + } + + break; + } + } if (gw && !in_addr_is_link_local(AF_INET6, (const union in_addr_union*) gw)) { _cleanup_free_ char *addr = NULL; -- cgit v1.2.3-54-g00ecf