From 3b59b9748aa13a244c173585dfbaf79dfff9ea8f Mon Sep 17 00:00:00 2001 From: David Gibson Date: Wed, 28 Feb 2024 22:25:17 +1100 Subject: tcp: Validate TCP endpoint addresses TCP connections should typically not have wildcard addresses (0.0.0.0 or ::) nor a zero port number for either endpoint. It's not entirely clear (at least to me) if it's strictly against the RFCs to do so, but at any rate the socket interfaces often treat those values specially[1], so it's not really possible to manipulate such connections. Likewise they should not have broadcast or multicast addresses for either endpoint. However, nothing prevents a guest from creating a SYN packet with such values, and it's not entirely clear what the effect on passt would be. To ensure sane behaviour, explicitly check for this case and drop such packets, logging a debug warning (we don't want a higher level, because that would allow a guest to spam the logs). We never expect such an address on an accept()ed socket either, but just in case, check for it as well. [1] Depending on context as "unknown", "match any" or "kernel, pick something for me" Signed-off-by: David Gibson Signed-off-by: Stefano Brivio --- tcp.c | 74 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++------- 1 file changed, 67 insertions(+), 7 deletions(-) diff --git a/tcp.c b/tcp.c index b4d7eec..2ea985e 100644 --- a/tcp.c +++ b/tcp.c @@ -284,6 +284,7 @@ #include #include #include +#include #include /* For struct tcp_info */ @@ -1935,27 +1936,59 @@ static void tcp_conn_from_tap(struct ctx *c, sa_family_t af, const struct tcphdr *th, const char *opts, size_t optlen, const struct timespec *now) { + in_port_t srcport = ntohs(th->source); + in_port_t dstport = ntohs(th->dest); struct sockaddr_in addr4 = { .sin_family = AF_INET, - .sin_port = th->dest, + .sin_port = htons(dstport), .sin_addr = *(struct in_addr *)daddr, }; struct sockaddr_in6 addr6 = { .sin6_family = AF_INET6, - .sin6_port = th->dest, + .sin6_port = htons(dstport), .sin6_addr = *(struct in6_addr *)daddr, }; const struct sockaddr *sa; struct tcp_tap_conn *conn; union flow *flow; + int s = -1, mss; socklen_t sl; - int s, mss; - - (void)saddr; if (!(flow = flow_alloc())) return; + if (af == AF_INET) { + if (IN4_IS_ADDR_UNSPECIFIED(saddr) || + IN4_IS_ADDR_BROADCAST(saddr) || + IN4_IS_ADDR_MULTICAST(saddr) || srcport == 0 || + IN4_IS_ADDR_UNSPECIFIED(daddr) || + IN4_IS_ADDR_BROADCAST(daddr) || + IN4_IS_ADDR_MULTICAST(daddr) || dstport == 0) { + char sstr[INET_ADDRSTRLEN], dstr[INET_ADDRSTRLEN]; + + debug("Invalid endpoint in TCP SYN: %s:%hu -> %s:%hu", + inet_ntop(AF_INET, saddr, sstr, sizeof(sstr)), + srcport, + inet_ntop(AF_INET, daddr, dstr, sizeof(dstr)), + dstport); + goto cancel; + } + } else if (af == AF_INET6) { + if (IN6_IS_ADDR_UNSPECIFIED(saddr) || + IN6_IS_ADDR_MULTICAST(saddr) || srcport == 0 || + IN6_IS_ADDR_UNSPECIFIED(daddr) || + IN6_IS_ADDR_MULTICAST(daddr) || dstport == 0) { + char sstr[INET6_ADDRSTRLEN], dstr[INET6_ADDRSTRLEN]; + + debug("Invalid endpoint in TCP SYN: %s:%hu -> %s:%hu", + inet_ntop(AF_INET6, saddr, sstr, sizeof(sstr)), + srcport, + inet_ntop(AF_INET6, daddr, dstr, sizeof(dstr)), + dstport); + goto cancel; + } + } + if ((s = tcp_conn_sock(c, af)) < 0) goto cancel; @@ -2006,8 +2039,8 @@ static void tcp_conn_from_tap(struct ctx *c, sa_family_t af, sl = sizeof(addr6); } - conn->fport = ntohs(th->dest); - conn->eport = ntohs(th->source); + conn->fport = dstport; + conn->eport = srcport; conn->seq_init_from_tap = ntohl(th->seq); conn->seq_from_tap = conn->seq_init_from_tap + 1; @@ -2736,6 +2769,33 @@ void tcp_listen_handler(struct ctx *c, union epoll_ref ref, if (s < 0) goto cancel; + if (sa.sa_family == AF_INET) { + const struct in_addr *addr = &sa.sa4.sin_addr; + in_port_t port = sa.sa4.sin_port; + + if (IN4_IS_ADDR_UNSPECIFIED(addr) || + IN4_IS_ADDR_BROADCAST(addr) || + IN4_IS_ADDR_MULTICAST(addr) || port == 0) { + char str[INET_ADDRSTRLEN]; + + err("Invalid endpoint from TCP accept(): %s:%hu", + inet_ntop(AF_INET, addr, str, sizeof(str)), port); + goto cancel; + } + } else if (sa.sa_family == AF_INET6) { + const struct in6_addr *addr = &sa.sa6.sin6_addr; + in_port_t port = sa.sa6.sin6_port; + + if (IN6_IS_ADDR_UNSPECIFIED(addr) || + IN6_IS_ADDR_MULTICAST(addr) || port == 0) { + char str[INET6_ADDRSTRLEN]; + + err("Invalid endpoint from TCP accept(): %s:%hu", + inet_ntop(AF_INET6, addr, str, sizeof(str)), port); + goto cancel; + } + } + if (tcp_splice_conn_from_sock(c, ref.tcp_listen.pif, ref.tcp_listen.port, flow, s, &sa)) return; -- cgit v1.2.3