| Message ID | 73b11222e312a60a17ccaeabbd0e96732289defc.1629840814.git.cdleonard@gmail.com (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | tcp: Initial support for RFC5925 auth option | expand |
On 8/24/21 2:34 PM, Leonard Crestez wrote: > The tcp_authopt features exposes a minimal interface to the rest of the > TCP stack. Only a few functions are exposed and if the feature is > disabled they return neutral values, avoiding ifdefs in the rest of the > code. > > Add calls into tcp authopt from send, receive and accept code. > > Signed-off-by: Leonard Crestez <cdleonard@gmail.com> > --- > include/net/tcp_authopt.h | 56 +++++++++ > net/ipv4/tcp_authopt.c | 246 ++++++++++++++++++++++++++++++++++++++ > net/ipv4/tcp_input.c | 17 +++ > net/ipv4/tcp_ipv4.c | 3 + > net/ipv4/tcp_minisocks.c | 2 + > net/ipv4/tcp_output.c | 74 +++++++++++- > net/ipv6/tcp_ipv6.c | 4 + > 7 files changed, 401 insertions(+), 1 deletion(-) > > diff --git a/include/net/tcp_authopt.h b/include/net/tcp_authopt.h > index c9ee2059b442..61db268f36f8 100644 > --- a/include/net/tcp_authopt.h > +++ b/include/net/tcp_authopt.h > @@ -21,10 +21,11 @@ struct tcp_authopt_key_info { > /* Wire identifiers */ > u8 send_id, recv_id; > u8 alg_id; > u8 keylen; > u8 key[TCP_AUTHOPT_MAXKEYLEN]; > + u8 maclen; I do not see maclen being enforced to 12, or a multiple of 4 ? This means that later [2], tcp_authopt_hash() will leave up to 3 unitialized bytes in the TCP options, sent to the wire. This is a security issue, since we will leak kernel memory. > struct sockaddr_storage addr; > struct tcp_authopt_alg_imp *alg; > }; > > /** > @@ -41,15 +42,53 @@ struct tcp_authopt_info { > u32 src_isn; > u32 dst_isn; > }; > > #ifdef CONFIG_TCP_AUTHOPT > +struct tcp_authopt_key_info *tcp_authopt_select_key(const struct sock *sk, > + const struct sock *addr_sk, > + u8 *rnextkeyid); > void tcp_authopt_clear(struct sock *sk); > int tcp_set_authopt(struct sock *sk, sockptr_t optval, unsigned int optlen); > int tcp_get_authopt_val(struct sock *sk, struct tcp_authopt *key); > int tcp_set_authopt_key(struct sock *sk, sockptr_t optval, unsigned int optlen); > +int tcp_authopt_hash( > + char *hash_location, > + struct tcp_authopt_key_info *key, > + struct sock *sk, struct sk_buff *skb); > +int __tcp_authopt_openreq(struct sock *newsk, const struct sock *oldsk, struct request_sock *req); > +static inline int tcp_authopt_openreq( > + struct sock *newsk, > + const struct sock *oldsk, > + struct request_sock *req) > +{ > + if (!rcu_dereference(tcp_sk(oldsk)->authopt_info)) > + return 0; > + else > + return __tcp_authopt_openreq(newsk, oldsk, req); > +} > +int __tcp_authopt_inbound_check( > + struct sock *sk, > + struct sk_buff *skb, > + struct tcp_authopt_info *info); > +static inline int tcp_authopt_inbound_check(struct sock *sk, struct sk_buff *skb) > +{ > + struct tcp_authopt_info *info = rcu_dereference(tcp_sk(sk)->authopt_info); > + > + if (info) > + return __tcp_authopt_inbound_check(sk, skb, info); > + else > + return 0; > +} > #else > +static inline struct tcp_authopt_key_info *tcp_authopt_select_key( > + const struct sock *sk, > + const struct sock *addr_sk, > + u8 *rnextkeyid) > +{ > + return NULL; > +} > static inline int tcp_set_authopt(struct sock *sk, sockptr_t optval, unsigned int optlen) > { > return -ENOPROTOOPT; > } > static inline int tcp_get_authopt_val(struct sock *sk, struct tcp_authopt *key) > @@ -61,8 +100,25 @@ static inline void tcp_authopt_clear(struct sock *sk) > } > static inline int tcp_set_authopt_key(struct sock *sk, sockptr_t optval, unsigned int optlen) > { > return -ENOPROTOOPT; > } > +static inline int tcp_authopt_hash( > + char *hash_location, > + struct tcp_authopt_key_info *key, > + struct sock *sk, struct sk_buff *skb) > +{ > + return -EINVAL; > +} > +static inline int tcp_authopt_openreq(struct sock *newsk, > + const struct sock *oldsk, > + struct request_sock *req) > +{ > + return 0; > +} > +static inline int tcp_authopt_inbound_check(struct sock *sk, struct sk_buff *skb) > +{ > + return 0; > +} > #endif > > #endif /* _LINUX_TCP_AUTHOPT_H */ > diff --git a/net/ipv4/tcp_authopt.c b/net/ipv4/tcp_authopt.c > index 2a3463ad6896..af777244d098 100644 > --- a/net/ipv4/tcp_authopt.c > +++ b/net/ipv4/tcp_authopt.c > @@ -203,10 +203,71 @@ static struct tcp_authopt_key_info *tcp_authopt_key_lookup_exact(const struct so > return key_info; > > return NULL; > } > > +struct tcp_authopt_key_info *tcp_authopt_lookup_send(struct tcp_authopt_info *info, > + const struct sock *addr_sk, > + int send_id) > +{ > + struct tcp_authopt_key_info *result = NULL; > + struct tcp_authopt_key_info *key; > + > + hlist_for_each_entry_rcu(key, &info->head, node, 0) { > + if (send_id >= 0 && key->send_id != send_id) > + continue; > + if (key->flags & TCP_AUTHOPT_KEY_ADDR_BIND) { > + if (addr_sk->sk_family == AF_INET) { > + struct sockaddr_in *key_addr = (struct sockaddr_in *)&key->addr; > + const struct in_addr *daddr = > + (const struct in_addr *)&addr_sk->sk_daddr; Why a cast is needed ? sk_daddr is a __be32, no need to cast it to in_addr > + > + if (WARN_ON(key_addr->sin_family != AF_INET)) Why a WARN_ON() is used ? If we expect this to trigger, then at minimumum WARN_ON_ONCE() please. > + continue; > + if (memcmp(daddr, &key_addr->sin_addr, sizeof(*daddr))) > + continue; Using memcmp() to compare two __be32 is overkill. > + } > + if (addr_sk->sk_family == AF_INET6) { > + struct sockaddr_in6 *key_addr = (struct sockaddr_in6 *)&key->addr; > + const struct in6_addr *daddr = &addr_sk->sk_v6_daddr; Not sure why a variable is used, you need it once. > + > + if (WARN_ON(key_addr->sin6_family != AF_INET6)) > + continue; > + if (memcmp(daddr, &key_addr->sin6_addr, sizeof(*daddr))) ipv6_addr_equal() should be faster. > + continue; > + } > + } > + if (result && net_ratelimit()) > + pr_warn("ambiguous tcp authentication keys configured for send\n"); > + result = key; > + } > + > + return result; > +} > + > +/** > + * tcp_authopt_select_key - select key for sending > + * > + * addr_sk is the sock used for comparing daddr, it is only different from sk in > + * the synack case. > + * > + * Result is protected by RCU and can't be stored, it may only be passed to > + * tcp_authopt_hash and only under a single rcu_read_lock. > + */ > +struct tcp_authopt_key_info *tcp_authopt_select_key(const struct sock *sk, > + const struct sock *addr_sk, > + u8 *rnextkeyid) > +{ > + struct tcp_authopt_info *info; > + > + info = rcu_dereference(tcp_sk(sk)->authopt_info); distro kernels will have CONFIG_TCP_AUTHOPT set, meaning that we will add a cache line miss for every incoming TCP packet even on hosts not using any RFC5925 TCP flow. For TCP MD5 we are using a static key, to avoid this extra cost. > + if (!info) > + return NULL; > + > + return tcp_authopt_lookup_send(info, addr_sk, -1); > +} > + > static struct tcp_authopt_info *__tcp_authopt_info_get_or_create(struct sock *sk) > { > struct tcp_sock *tp = tcp_sk(sk); > struct tcp_authopt_info *info; > > @@ -387,16 +448,69 @@ int tcp_set_authopt_key(struct sock *sk, sockptr_t optval, unsigned int optlen) > key_info->recv_id = opt.recv_id; > key_info->alg_id = opt.alg; > key_info->alg = alg; > key_info->keylen = opt.keylen; > memcpy(key_info->key, opt.key, opt.keylen); > + key_info->maclen = alg->maclen; > memcpy(&key_info->addr, &opt.addr, sizeof(key_info->addr)); > hlist_add_head_rcu(&key_info->node, &info->head); > > return 0; > } > > +static int tcp_authopt_clone_keys(struct sock *newsk, > + const struct sock *oldsk, > + struct tcp_authopt_info *new_info, > + struct tcp_authopt_info *old_info) > +{ > + struct tcp_authopt_key_info *old_key; > + struct tcp_authopt_key_info *new_key; > + > + hlist_for_each_entry_rcu(old_key, &old_info->head, node, lockdep_sock_is_held(sk)) { > + new_key = sock_kmalloc(newsk, sizeof(*new_key), GFP_ATOMIC); > + if (!new_key) > + return -ENOMEM; > + memcpy(new_key, old_key, sizeof(*new_key)); > + tcp_authopt_alg_incref(old_key->alg); > + hlist_add_head_rcu(&new_key->node, &new_info->head); > + } > + > + return 0; > +} > + > +/** Called to create accepted sockets. > + * > + * Need to copy authopt info from listen socket. > + */ > +int __tcp_authopt_openreq(struct sock *newsk, const struct sock *oldsk, struct request_sock *req) > +{ > + struct tcp_authopt_info *old_info; > + struct tcp_authopt_info *new_info; > + int err; > + > + old_info = rcu_dereference(tcp_sk(oldsk)->authopt_info); > + if (!old_info) > + return 0; > + > + new_info = kmalloc(sizeof(*new_info), GFP_ATOMIC | __GFP_ZERO); kzalloc() is your friend. (same remark for your other patches, where you are using __GFP_ZERO) Also see additional comment [1] > + if (!new_info) > + return -ENOMEM; > + > + sk_nocaps_add(newsk, NETIF_F_GSO_MASK); > + new_info->src_isn = tcp_rsk(req)->snt_isn; > + new_info->dst_isn = tcp_rsk(req)->rcv_isn; > + INIT_HLIST_HEAD(&new_info->head); > + err = tcp_authopt_clone_keys(newsk, oldsk, new_info, old_info); > + if (err) { > + __tcp_authopt_info_free(newsk, new_info); [1] Are we leaving in place old value of newsk->authopt_info ? If this is copied from the listener, I think you need to add a tcp_sk(newsk)->authopt_info = NULL; before the kzalloc() call done above. > + return err; > + } > + rcu_assign_pointer(tcp_sk(newsk)->authopt_info, new_info); > + > + return 0; > +} > + > /* feed traffic key into shash */ > static int tcp_authopt_shash_traffic_key(struct shash_desc *desc, > struct sock *sk, > struct sk_buff *skb, > bool input, > @@ -815,10 +929,16 @@ static int tcp_authopt_hash_packet(struct crypto_shash *tfm, > return err; > > return crypto_shash_final(desc, macbuf); > } > > +/** > + * __tcp_authopt_calc_mac - Compute packet MAC using key > + * > + * @macbuf: output buffer. Must be large enough to fit the digestsize of the > + * underlying transform before truncation. Please use TCP_AUTHOPT_MAXMACBUF > + */ > int __tcp_authopt_calc_mac(struct sock *sk, > struct sk_buff *skb, > struct tcp_authopt_key_info *key, > bool input, > char *macbuf) > @@ -859,5 +979,131 @@ int __tcp_authopt_calc_mac(struct sock *sk, > > out: > tcp_authopt_put_mac_shash(key, mac_tfm); > return err; > } > + > +/** > + * tcp_authopt_hash - fill in the mac > + * > + * The key must come from tcp_authopt_select_key. > + */ > +int tcp_authopt_hash(char *hash_location, > + struct tcp_authopt_key_info *key, > + struct sock *sk, > + struct sk_buff *skb) > +{ > + /* MAC inside option is truncated to 12 bytes but crypto API needs output > + * buffer to be large enough so we use a buffer on the stack. > + */ > + u8 macbuf[TCP_AUTHOPT_MAXMACBUF]; > + int err; > + > + if (WARN_ON(key->maclen > sizeof(macbuf))) > + return -ENOBUFS; > + > + err = __tcp_authopt_calc_mac(sk, skb, key, false, macbuf); > + if (err) { > + /* If mac calculation fails and caller doesn't handle the error > + * try to make it obvious inside the packet. > + */ > + memset(hash_location, 0, key->maclen); > + return err; > + } > + memcpy(hash_location, macbuf, key->maclen); [2] This is the place were we do not make sure to clear the padding bytes (if key->maclen is not a multiple of 4) > + > + return 0; > +} > + > +static struct tcp_authopt_key_info *tcp_authopt_lookup_recv(struct sock *sk, > + struct sk_buff *skb, > + struct tcp_authopt_info *info, > + int recv_id) > +{ > + struct tcp_authopt_key_info *result = NULL; > + struct tcp_authopt_key_info *key; > + > + /* multiple matches will cause occasional failures */ > + hlist_for_each_entry_rcu(key, &info->head, node, 0) { > + if (recv_id >= 0 && key->recv_id != recv_id) > + continue; > + if (key->flags & TCP_AUTHOPT_KEY_ADDR_BIND) { > + if (sk->sk_family == AF_INET) { > + struct sockaddr_in *key_addr = (struct sockaddr_in *)&key->addr; > + struct iphdr *iph = (struct iphdr *)skb_network_header(skb); > + > + if (WARN_ON(key_addr->sin_family != AF_INET)) > + continue; > + if (WARN_ON(iph->version != 4)) > + continue; > + if (memcmp(&iph->saddr, &key_addr->sin_addr, sizeof(iph->saddr))) > + continue; > + } > + if (sk->sk_family == AF_INET6) { > + struct sockaddr_in6 *key_addr = (struct sockaddr_in6 *)&key->addr; > + struct ipv6hdr *iph = (struct ipv6hdr *)skb_network_header(skb); > + > + if (WARN_ON(key_addr->sin6_family != AF_INET6)) > + continue; > + if (WARN_ON(iph->version != 6)) > + continue; > + if (memcmp(&iph->saddr, &key_addr->sin6_addr, sizeof(iph->saddr))) > + continue; > + } > + } > + if (result && net_ratelimit()) > + pr_warn("ambiguous tcp authentication keys configured for receive\n"); > + result = key; > + } > + > + return result; > +} > + > +int __tcp_authopt_inbound_check(struct sock *sk, struct sk_buff *skb, struct tcp_authopt_info *info) > +{ > + struct tcphdr *th = (struct tcphdr *)skb_transport_header(skb); > + struct tcphdr_authopt *opt; > + struct tcp_authopt_key_info *key; > + u8 macbuf[TCP_AUTHOPT_MAXMACBUF]; > + int err; > + > + opt = (struct tcphdr_authopt *)tcp_authopt_find_option(th); > + key = tcp_authopt_lookup_recv(sk, skb, info, opt ? opt->keyid : -1); > + > + /* nothing found or expected */ > + if (!opt && !key) > + return 0; > + if (!opt && key) { > + net_info_ratelimited("TCP Authentication Missing\n"); > + return -EINVAL; > + } > + if (opt && !key) { > + /* RFC5925 Section 7.3: > + * A TCP-AO implementation MUST allow for configuration of the behavior > + * of segments with TCP-AO but that do not match an MKT. The initial > + * default of this configuration SHOULD be to silently accept such > + * connections. > + */ > + if (info->flags & TCP_AUTHOPT_FLAG_REJECT_UNEXPECTED) { > + net_info_ratelimited("TCP Authentication Unexpected: Rejected\n"); > + return -EINVAL; > + } else { > + net_info_ratelimited("TCP Authentication Unexpected: Accepted\n"); > + return 0; > + } > + } > + > + /* bad inbound key len */ > + if (key->maclen + 4 != opt->len) > + return -EINVAL; > + > + err = __tcp_authopt_calc_mac(sk, skb, key, true, macbuf); > + if (err) > + return err; > + > + if (memcmp(macbuf, opt->mac, key->maclen)) { > + net_info_ratelimited("TCP Authentication Failed\n"); > + return -EINVAL; > + } > + > + return 0; > +} > diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c > index 3f7bd7ae7d7a..e0b51b2f747f 100644 > --- a/net/ipv4/tcp_input.c > +++ b/net/ipv4/tcp_input.c > @@ -70,10 +70,11 @@ > #include <linux/sysctl.h> > #include <linux/kernel.h> > #include <linux/prefetch.h> > #include <net/dst.h> > #include <net/tcp.h> > +#include <net/tcp_authopt.h> > #include <net/inet_common.h> > #include <linux/ipsec.h> > #include <asm/unaligned.h> > #include <linux/errqueue.h> > #include <trace/events/tcp.h> > @@ -5967,18 +5968,34 @@ void tcp_init_transfer(struct sock *sk, int bpf_op, struct sk_buff *skb) > if (!icsk->icsk_ca_initialized) > tcp_init_congestion_control(sk); > tcp_init_buffer_space(sk); > } > > +static void tcp_authopt_finish_connect(struct sock *sk, struct sk_buff *skb) > +{ > +#ifdef CONFIG_TCP_AUTHOPT > + struct tcp_authopt_info *info; > + > + info = rcu_dereference_protected(tcp_sk(sk)->authopt_info, lockdep_sock_is_held(sk)); > + if (!info) > + return; > + > + info->src_isn = ntohl(tcp_hdr(skb)->ack_seq) - 1; > + info->dst_isn = ntohl(tcp_hdr(skb)->seq); > +#endif > +} > + > void tcp_finish_connect(struct sock *sk, struct sk_buff *skb) > { > struct tcp_sock *tp = tcp_sk(sk); > struct inet_connection_sock *icsk = inet_csk(sk); > > tcp_set_state(sk, TCP_ESTABLISHED); > icsk->icsk_ack.lrcvtime = tcp_jiffies32; > > + tcp_authopt_finish_connect(sk, skb); > + > if (skb) { > icsk->icsk_af_ops->sk_rx_dst_set(sk, skb); > security_inet_conn_established(sk, skb); > sk_mark_napi_id(sk, skb); > } > diff --git a/net/ipv4/tcp_ipv4.c b/net/ipv4/tcp_ipv4.c > index 1348615c7576..a1d39183908c 100644 > --- a/net/ipv4/tcp_ipv4.c > +++ b/net/ipv4/tcp_ipv4.c > @@ -2060,10 +2060,13 @@ int tcp_v4_rcv(struct sk_buff *skb) > goto discard_and_relse; > > if (tcp_v4_inbound_md5_hash(sk, skb, dif, sdif)) > goto discard_and_relse; > > + if (tcp_authopt_inbound_check(sk, skb)) > + goto discard_and_relse; > + > nf_reset_ct(skb); > > if (tcp_filter(sk, skb)) > goto discard_and_relse; > th = (const struct tcphdr *)skb->data; > diff --git a/net/ipv4/tcp_minisocks.c b/net/ipv4/tcp_minisocks.c > index 0a4f3f16140a..4d7d86547b0e 100644 > --- a/net/ipv4/tcp_minisocks.c > +++ b/net/ipv4/tcp_minisocks.c > @@ -24,10 +24,11 @@ > #include <linux/slab.h> > #include <linux/sysctl.h> > #include <linux/workqueue.h> > #include <linux/static_key.h> > #include <net/tcp.h> > +#include <net/tcp_authopt.h> > #include <net/inet_common.h> > #include <net/xfrm.h> > #include <net/busy_poll.h> > > static bool tcp_in_window(u32 seq, u32 end_seq, u32 s_win, u32 e_win) > @@ -539,10 +540,11 @@ struct sock *tcp_create_openreq_child(const struct sock *sk, > #ifdef CONFIG_TCP_MD5SIG > newtp->md5sig_info = NULL; /*XXX*/ > if (newtp->af_specific->md5_lookup(sk, newsk)) > newtp->tcp_header_len += TCPOLEN_MD5SIG_ALIGNED; > #endif > + tcp_authopt_openreq(newsk, sk, req); > if (skb->len >= TCP_MSS_DEFAULT + newtp->tcp_header_len) > newicsk->icsk_ack.last_seg_size = skb->len - newtp->tcp_header_len; > newtp->rx_opt.mss_clamp = req->mss; > tcp_ecn_openreq_child(newtp, req); > newtp->fastopen_req = NULL; > diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c > index 6d72f3ea48c4..6d73bee349c9 100644 > --- a/net/ipv4/tcp_output.c > +++ b/net/ipv4/tcp_output.c > @@ -37,10 +37,11 @@ > > #define pr_fmt(fmt) "TCP: " fmt > > #include <net/tcp.h> > #include <net/mptcp.h> > +#include <net/tcp_authopt.h> > > #include <linux/compiler.h> > #include <linux/gfp.h> > #include <linux/module.h> > #include <linux/static_key.h> > @@ -411,10 +412,11 @@ static inline bool tcp_urg_mode(const struct tcp_sock *tp) > > #define OPTION_SACK_ADVERTISE (1 << 0) > #define OPTION_TS (1 << 1) > #define OPTION_MD5 (1 << 2) > #define OPTION_WSCALE (1 << 3) > +#define OPTION_AUTHOPT (1 << 4) > #define OPTION_FAST_OPEN_COOKIE (1 << 8) > #define OPTION_SMC (1 << 9) > #define OPTION_MPTCP (1 << 10) > > static void smc_options_write(__be32 *ptr, u16 *options) > @@ -435,16 +437,21 @@ static void smc_options_write(__be32 *ptr, u16 *options) > struct tcp_out_options { > u16 options; /* bit field of OPTION_* */ > u16 mss; /* 0 to disable */ > u8 ws; /* window scale, 0 to disable */ > u8 num_sack_blocks; /* number of SACK blocks to include */ > - u8 hash_size; /* bytes in hash_location */ > u8 bpf_opt_len; /* length of BPF hdr option */ > +#ifdef CONFIG_TCP_AUTHOPT > + u8 authopt_rnextkeyid; /* rnextkey */ > +#endif > __u8 *hash_location; /* temporary pointer, overloaded */ > __u32 tsval, tsecr; /* need to include OPTION_TS */ > struct tcp_fastopen_cookie *fastopen_cookie; /* Fast open cookie */ > struct mptcp_out_options mptcp; > +#ifdef CONFIG_TCP_AUTHOPT > + struct tcp_authopt_key_info *authopt_key; > +#endif > }; > > static void mptcp_options_write(__be32 *ptr, const struct tcp_sock *tp, > struct tcp_out_options *opts) > { > @@ -617,10 +624,24 @@ static void tcp_options_write(__be32 *ptr, struct tcp_sock *tp, > /* overload cookie hash location */ > opts->hash_location = (__u8 *)ptr; > ptr += 4; > } > > +#ifdef CONFIG_TCP_AUTHOPT > + if (unlikely(OPTION_AUTHOPT & options)) { > + struct tcp_authopt_key_info *key = opts->authopt_key; > + > + WARN_ON(!key); > + *ptr++ = htonl((TCPOPT_AUTHOPT << 24) | ((4 + key->maclen) << 16) | > + (key->send_id << 8) | opts->authopt_rnextkeyid); > + /* overload cookie hash location */ > + opts->hash_location = (__u8 *)ptr; > + /* maclen is currently always 12 but try to align nicely anyway. */ > + ptr += (key->maclen + 3) / 4; > + } > +#endif > + > if (unlikely(opts->mss)) { > *ptr++ = htonl((TCPOPT_MSS << 24) | > (TCPOLEN_MSS << 16) | > opts->mss); > } > @@ -752,10 +773,28 @@ static void mptcp_set_option_cond(const struct request_sock *req, > } > } > } > } > > +static int tcp_authopt_init_options(const struct sock *sk, > + const struct sock *addr_sk, > + struct tcp_out_options *opts) > +{ > +#ifdef CONFIG_TCP_AUTHOPT > + struct tcp_authopt_key_info *key; > + > + key = tcp_authopt_select_key(sk, addr_sk, &opts->authopt_rnextkeyid); > + if (key) { > + opts->options |= OPTION_AUTHOPT; > + opts->authopt_key = key; > + return 4 + key->maclen; > + } > +#endif > + > + return 0; > +} > + > /* Compute TCP options for SYN packets. This is not the final > * network wire format yet. > */ > static unsigned int tcp_syn_options(struct sock *sk, struct sk_buff *skb, > struct tcp_out_options *opts, > @@ -774,10 +813,11 @@ static unsigned int tcp_syn_options(struct sock *sk, struct sk_buff *skb, > opts->options |= OPTION_MD5; > remaining -= TCPOLEN_MD5SIG_ALIGNED; > } > } > #endif > + remaining -= tcp_authopt_init_options(sk, sk, opts); > > /* We always get an MSS option. The option bytes which will be seen in > * normal data packets should timestamps be used, must be in the MSS > * advertised. But we subtract them from tp->mss_cache so that > * calculations in tcp_sendmsg are simpler etc. So account for this > @@ -862,10 +902,11 @@ static unsigned int tcp_synack_options(const struct sock *sk, > */ > if (synack_type != TCP_SYNACK_COOKIE) > ireq->tstamp_ok &= !ireq->sack_ok; > } > #endif > + remaining -= tcp_authopt_init_options(sk, req_to_sk(req), opts); > > /* We always send an MSS option. */ > opts->mss = mss; > remaining -= TCPOLEN_MSS_ALIGNED; > > @@ -930,10 +971,11 @@ static unsigned int tcp_established_options(struct sock *sk, struct sk_buff *skb > opts->options |= OPTION_MD5; > size += TCPOLEN_MD5SIG_ALIGNED; > } > } > #endif > + size += tcp_authopt_init_options(sk, sk, opts); > > if (likely(tp->rx_opt.tstamp_ok)) { > opts->options |= OPTION_TS; > opts->tsval = skb ? tcp_skb_timestamp(skb) + tp->tsoffset : 0; > opts->tsecr = tp->rx_opt.ts_recent; > @@ -1277,10 +1319,14 @@ static int __tcp_transmit_skb(struct sock *sk, struct sk_buff *skb, > > inet = inet_sk(sk); > tcb = TCP_SKB_CB(skb); > memset(&opts, 0, sizeof(opts)); > > +#ifdef CONFIG_TCP_AUTHOPT > + /* for tcp_authopt_init_options inside tcp_syn_options or tcp_established_options */ > + rcu_read_lock(); > +#endif > if (unlikely(tcb->tcp_flags & TCPHDR_SYN)) { > tcp_options_size = tcp_syn_options(sk, skb, &opts, &md5); > } else { > tcp_options_size = tcp_established_options(sk, skb, &opts, > &md5); > @@ -1365,10 +1411,17 @@ static int __tcp_transmit_skb(struct sock *sk, struct sk_buff *skb, > sk_nocaps_add(sk, NETIF_F_GSO_MASK); > tp->af_specific->calc_md5_hash(opts.hash_location, > md5, sk, skb); > } > #endif > +#ifdef CONFIG_TCP_AUTHOPT > + if (opts.authopt_key) { > + sk_nocaps_add(sk, NETIF_F_GSO_MASK); > + tcp_authopt_hash(opts.hash_location, opts.authopt_key, sk, skb); > + } > + rcu_read_unlock(); > +#endif > > /* BPF prog is the last one writing header option */ > bpf_skops_write_hdr_opt(sk, skb, NULL, NULL, 0, &opts); > > INDIRECT_CALL_INET(icsk->icsk_af_ops->send_check, > @@ -1836,12 +1889,21 @@ unsigned int tcp_current_mss(struct sock *sk) > u32 mtu = dst_mtu(dst); > if (mtu != inet_csk(sk)->icsk_pmtu_cookie) > mss_now = tcp_sync_mss(sk, mtu); > } > > +#ifdef CONFIG_TCP_AUTHOPT > + /* Even if the result is not used rcu_read_lock is required when scanning for > + * tcp authentication keys. Otherwise lockdep will complain. > + */ > + rcu_read_lock(); > +#endif > header_len = tcp_established_options(sk, NULL, &opts, &md5) + > sizeof(struct tcphdr); > +#ifdef CONFIG_TCP_AUTHOPT > + rcu_read_unlock(); > +#endif > /* The mss_cache is sized based on tp->tcp_header_len, which assumes > * some common options. If this is an odd packet (because we have SACK > * blocks etc) then our calculated header_len will be different, and > * we have to adjust mss_now correspondingly */ > if (header_len != tp->tcp_header_len) { > @@ -3566,10 +3628,14 @@ struct sk_buff *tcp_make_synack(const struct sock *sk, struct dst_entry *dst, > } > > #ifdef CONFIG_TCP_MD5SIG > rcu_read_lock(); > md5 = tcp_rsk(req)->af_specific->req_md5_lookup(sk, req_to_sk(req)); > +#endif > +#ifdef CONFIG_TCP_AUTHOPT > + /* for tcp_authopt_init_options inside tcp_synack_options */ > + rcu_read_lock(); > #endif > skb_set_hash(skb, tcp_rsk(req)->txhash, PKT_HASH_TYPE_L4); > /* bpf program will be interested in the tcp_flags */ > TCP_SKB_CB(skb)->tcp_flags = TCPHDR_SYN | TCPHDR_ACK; > tcp_header_size = tcp_synack_options(sk, req, mss, skb, &opts, md5, > @@ -3603,10 +3669,16 @@ struct sk_buff *tcp_make_synack(const struct sock *sk, struct dst_entry *dst, > if (md5) > tcp_rsk(req)->af_specific->calc_md5_hash(opts.hash_location, > md5, req_to_sk(req), skb); > rcu_read_unlock(); > #endif > +#ifdef CONFIG_TCP_AUTHOPT > + /* If signature fails we do nothing */ > + if (opts.authopt_key) > + tcp_authopt_hash(opts.hash_location, opts.authopt_key, req_to_sk(req), skb); > + rcu_read_unlock(); > +#endif > > bpf_skops_write_hdr_opt((struct sock *)sk, skb, req, syn_skb, > synack_type, &opts); > > skb->skb_mstamp_ns = now; > diff --git a/net/ipv6/tcp_ipv6.c b/net/ipv6/tcp_ipv6.c > index 0ce52d46e4f8..51381a9c2bd5 100644 > --- a/net/ipv6/tcp_ipv6.c > +++ b/net/ipv6/tcp_ipv6.c > @@ -40,10 +40,11 @@ > #include <linux/icmpv6.h> > #include <linux/random.h> > #include <linux/indirect_call_wrapper.h> > > #include <net/tcp.h> > +#include <net/tcp_authopt.h> > #include <net/ndisc.h> > #include <net/inet6_hashtables.h> > #include <net/inet6_connection_sock.h> > #include <net/ipv6.h> > #include <net/transp_v6.h> > @@ -1733,10 +1734,13 @@ INDIRECT_CALLABLE_SCOPE int tcp_v6_rcv(struct sk_buff *skb) > goto discard_and_relse; > > if (tcp_v6_inbound_md5_hash(sk, skb, dif, sdif)) > goto discard_and_relse; > > + if (tcp_authopt_inbound_check(sk, skb)) > + goto discard_and_relse; > + > if (tcp_filter(sk, skb)) > goto discard_and_relse; > th = (const struct tcphdr *)skb->data; > hdr = ipv6_hdr(skb); > tcp_v6_fill_cb(skb, hdr, th); >
On 25.08.2021 01:59, Eric Dumazet wrote: > On 8/24/21 2:34 PM, Leonard Crestez wrote: >> The tcp_authopt features exposes a minimal interface to the rest of the >> TCP stack. Only a few functions are exposed and if the feature is >> disabled they return neutral values, avoiding ifdefs in the rest of the >> code. >> >> Add calls into tcp authopt from send, receive and accept code. >> >> Signed-off-by: Leonard Crestez <cdleonard@gmail.com> >> --- >> include/net/tcp_authopt.h | 56 +++++++++ >> net/ipv4/tcp_authopt.c | 246 ++++++++++++++++++++++++++++++++++++++ >> net/ipv4/tcp_input.c | 17 +++ >> net/ipv4/tcp_ipv4.c | 3 + >> net/ipv4/tcp_minisocks.c | 2 + >> net/ipv4/tcp_output.c | 74 +++++++++++- >> net/ipv6/tcp_ipv6.c | 4 + >> 7 files changed, 401 insertions(+), 1 deletion(-) >> >> diff --git a/include/net/tcp_authopt.h b/include/net/tcp_authopt.h >> index c9ee2059b442..61db268f36f8 100644 >> --- a/include/net/tcp_authopt.h >> +++ b/include/net/tcp_authopt.h >> @@ -21,10 +21,11 @@ struct tcp_authopt_key_info { >> /* Wire identifiers */ >> u8 send_id, recv_id; >> u8 alg_id; >> u8 keylen; >> u8 key[TCP_AUTHOPT_MAXKEYLEN]; >> + u8 maclen; > > I do not see maclen being enforced to 12, or a multiple of 4 ? For both current algorithms the maclen value is 12. I just implemented RFC5926, there is no way to control this from userspace. > This means that later [2], tcp_authopt_hash() will leave up to 3 > unitialized bytes in the TCP options, sent to the wire. > > This is a security issue, since we will leak kernel memory. Filling the remainder with zeroes does make sense, or at least WARN_ON(maclen != 4) so that it's obvious to anyone who attempts to extend the algorithms. >> +struct tcp_authopt_key_info *tcp_authopt_lookup_send(struct tcp_authopt_info *info, >> + const struct sock *addr_sk, >> + int send_id) >> +{ >> + struct tcp_authopt_key_info *result = NULL; >> + struct tcp_authopt_key_info *key; >> + >> + hlist_for_each_entry_rcu(key, &info->head, node, 0) { >> + if (send_id >= 0 && key->send_id != send_id) >> + continue; >> + if (key->flags & TCP_AUTHOPT_KEY_ADDR_BIND) { >> + if (addr_sk->sk_family == AF_INET) { >> + struct sockaddr_in *key_addr = (struct sockaddr_in *)&key->addr; >> + const struct in_addr *daddr = >> + (const struct in_addr *)&addr_sk->sk_daddr; > > Why a cast is needed ? sk_daddr is a __be32, no need to cast it to in_addr >> + >> + if (WARN_ON(key_addr->sin_family != AF_INET)) > > Why a WARN_ON() is used ? If we expect this to trigger, then at minimumum WARN_ON_ONCE() please. > >> + continue; >> + if (memcmp(daddr, &key_addr->sin_addr, sizeof(*daddr))) >> + continue; > > Using memcmp() to compare two __be32 is overkill. > >> + } >> + if (addr_sk->sk_family == AF_INET6) { >> + struct sockaddr_in6 *key_addr = (struct sockaddr_in6 *)&key->addr; >> + const struct in6_addr *daddr = &addr_sk->sk_v6_daddr; > > Not sure why a variable is used, you need it once. > >> + >> + if (WARN_ON(key_addr->sin6_family != AF_INET6)) >> + continue; >> + if (memcmp(daddr, &key_addr->sin6_addr, sizeof(*daddr))) > > ipv6_addr_equal() should be faster. OK, I will replace the comparisons. Checking address family is mostly paranoia on my part, I don't know if a real scenario exists for AF mismatch. Still need to check ipv4-mapped ipv6 addresses, not sure if those can receive ipv4 skbs on an ipv6 socket. >> +struct tcp_authopt_key_info *tcp_authopt_select_key(const struct sock *sk, >> + const struct sock *addr_sk, >> + u8 *rnextkeyid) >> +{ >> + struct tcp_authopt_info *info; >> + >> + info = rcu_dereference(tcp_sk(sk)->authopt_info); > > distro kernels will have CONFIG_TCP_AUTHOPT set, meaning > that we will add a cache line miss for every incoming TCP packet > even on hosts not using any RFC5925 TCP flow. > > For TCP MD5 we are using a static key, to avoid this extra cost. OK, will add a static_key. The check for "does socket have tcp_authopt" also belongs in an inline wrapper, similar to inbound check >> +int __tcp_authopt_openreq(struct sock *newsk, const struct sock *oldsk, struct request_sock *req) >> +{ >> + struct tcp_authopt_info *old_info; >> + struct tcp_authopt_info *new_info; >> + int err; >> + >> + old_info = rcu_dereference(tcp_sk(oldsk)->authopt_info); >> + if (!old_info) >> + return 0; >> + >> + new_info = kmalloc(sizeof(*new_info), GFP_ATOMIC | __GFP_ZERO); > > kzalloc() is your friend. (same remark for your other patches, where you are using __GFP_ZERO) > Also see additional comment [1] OK > >> + if (!new_info) >> + return -ENOMEM; >> + >> + sk_nocaps_add(newsk, NETIF_F_GSO_MASK); >> + new_info->src_isn = tcp_rsk(req)->snt_isn; >> + new_info->dst_isn = tcp_rsk(req)->rcv_isn; >> + INIT_HLIST_HEAD(&new_info->head); >> + err = tcp_authopt_clone_keys(newsk, oldsk, new_info, old_info); >> + if (err) { >> + __tcp_authopt_info_free(newsk, new_info); > > Are we leaving in place old value of newsk->authopt_info ? > If this is copied from the listener, I think you need > to add a tcp_sk(newsk)->authopt_info = NULL; > before the kzalloc() call done above. Yes, authopt_info should be set to NULL on error because keeping the listen socket's value is wrong and dangerous (double free). Leaving authopt_info NULL or malloc failure is still possible dangerous because it means all keys are ignored and accepted. Not clear how we could cause tcp_create_openreq_child to fail instead. This is a problem in a few other parts: if cryptography fails the outbound MAC is filled with zeros because there's not obvious way to make TX fail at that point. >> + err = __tcp_authopt_calc_mac(sk, skb, key, false, macbuf); >> + if (err) { >> + /* If mac calculation fails and caller doesn't handle the error >> + * try to make it obvious inside the packet. >> + */ >> + memset(hash_location, 0, key->maclen); >> + return err; >> + } >> + memcpy(hash_location, macbuf, key->maclen); > > > [2] > This is the place were we do not make sure to clear the padding bytes > (if key->maclen is not a multiple of 4) Yes. It might make sense to fix in caller because it's the caller which decides to align options.
diff --git a/include/net/tcp_authopt.h b/include/net/tcp_authopt.h index c9ee2059b442..61db268f36f8 100644 --- a/include/net/tcp_authopt.h +++ b/include/net/tcp_authopt.h @@ -21,10 +21,11 @@ struct tcp_authopt_key_info { /* Wire identifiers */ u8 send_id, recv_id; u8 alg_id; u8 keylen; u8 key[TCP_AUTHOPT_MAXKEYLEN]; + u8 maclen; struct sockaddr_storage addr; struct tcp_authopt_alg_imp *alg; }; /** @@ -41,15 +42,53 @@ struct tcp_authopt_info { u32 src_isn; u32 dst_isn; }; #ifdef CONFIG_TCP_AUTHOPT +struct tcp_authopt_key_info *tcp_authopt_select_key(const struct sock *sk, + const struct sock *addr_sk, + u8 *rnextkeyid); void tcp_authopt_clear(struct sock *sk); int tcp_set_authopt(struct sock *sk, sockptr_t optval, unsigned int optlen); int tcp_get_authopt_val(struct sock *sk, struct tcp_authopt *key); int tcp_set_authopt_key(struct sock *sk, sockptr_t optval, unsigned int optlen); +int tcp_authopt_hash( + char *hash_location, + struct tcp_authopt_key_info *key, + struct sock *sk, struct sk_buff *skb); +int __tcp_authopt_openreq(struct sock *newsk, const struct sock *oldsk, struct request_sock *req); +static inline int tcp_authopt_openreq( + struct sock *newsk, + const struct sock *oldsk, + struct request_sock *req) +{ + if (!rcu_dereference(tcp_sk(oldsk)->authopt_info)) + return 0; + else + return __tcp_authopt_openreq(newsk, oldsk, req); +} +int __tcp_authopt_inbound_check( + struct sock *sk, + struct sk_buff *skb, + struct tcp_authopt_info *info); +static inline int tcp_authopt_inbound_check(struct sock *sk, struct sk_buff *skb) +{ + struct tcp_authopt_info *info = rcu_dereference(tcp_sk(sk)->authopt_info); + + if (info) + return __tcp_authopt_inbound_check(sk, skb, info); + else + return 0; +} #else +static inline struct tcp_authopt_key_info *tcp_authopt_select_key( + const struct sock *sk, + const struct sock *addr_sk, + u8 *rnextkeyid) +{ + return NULL; +} static inline int tcp_set_authopt(struct sock *sk, sockptr_t optval, unsigned int optlen) { return -ENOPROTOOPT; } static inline int tcp_get_authopt_val(struct sock *sk, struct tcp_authopt *key) @@ -61,8 +100,25 @@ static inline void tcp_authopt_clear(struct sock *sk) } static inline int tcp_set_authopt_key(struct sock *sk, sockptr_t optval, unsigned int optlen) { return -ENOPROTOOPT; } +static inline int tcp_authopt_hash( + char *hash_location, + struct tcp_authopt_key_info *key, + struct sock *sk, struct sk_buff *skb) +{ + return -EINVAL; +} +static inline int tcp_authopt_openreq(struct sock *newsk, + const struct sock *oldsk, + struct request_sock *req) +{ + return 0; +} +static inline int tcp_authopt_inbound_check(struct sock *sk, struct sk_buff *skb) +{ + return 0; +} #endif #endif /* _LINUX_TCP_AUTHOPT_H */ diff --git a/net/ipv4/tcp_authopt.c b/net/ipv4/tcp_authopt.c index 2a3463ad6896..af777244d098 100644 --- a/net/ipv4/tcp_authopt.c +++ b/net/ipv4/tcp_authopt.c @@ -203,10 +203,71 @@ static struct tcp_authopt_key_info *tcp_authopt_key_lookup_exact(const struct so return key_info; return NULL; } +struct tcp_authopt_key_info *tcp_authopt_lookup_send(struct tcp_authopt_info *info, + const struct sock *addr_sk, + int send_id) +{ + struct tcp_authopt_key_info *result = NULL; + struct tcp_authopt_key_info *key; + + hlist_for_each_entry_rcu(key, &info->head, node, 0) { + if (send_id >= 0 && key->send_id != send_id) + continue; + if (key->flags & TCP_AUTHOPT_KEY_ADDR_BIND) { + if (addr_sk->sk_family == AF_INET) { + struct sockaddr_in *key_addr = (struct sockaddr_in *)&key->addr; + const struct in_addr *daddr = + (const struct in_addr *)&addr_sk->sk_daddr; + + if (WARN_ON(key_addr->sin_family != AF_INET)) + continue; + if (memcmp(daddr, &key_addr->sin_addr, sizeof(*daddr))) + continue; + } + if (addr_sk->sk_family == AF_INET6) { + struct sockaddr_in6 *key_addr = (struct sockaddr_in6 *)&key->addr; + const struct in6_addr *daddr = &addr_sk->sk_v6_daddr; + + if (WARN_ON(key_addr->sin6_family != AF_INET6)) + continue; + if (memcmp(daddr, &key_addr->sin6_addr, sizeof(*daddr))) + continue; + } + } + if (result && net_ratelimit()) + pr_warn("ambiguous tcp authentication keys configured for send\n"); + result = key; + } + + return result; +} + +/** + * tcp_authopt_select_key - select key for sending + * + * addr_sk is the sock used for comparing daddr, it is only different from sk in + * the synack case. + * + * Result is protected by RCU and can't be stored, it may only be passed to + * tcp_authopt_hash and only under a single rcu_read_lock. + */ +struct tcp_authopt_key_info *tcp_authopt_select_key(const struct sock *sk, + const struct sock *addr_sk, + u8 *rnextkeyid) +{ + struct tcp_authopt_info *info; + + info = rcu_dereference(tcp_sk(sk)->authopt_info); + if (!info) + return NULL; + + return tcp_authopt_lookup_send(info, addr_sk, -1); +} + static struct tcp_authopt_info *__tcp_authopt_info_get_or_create(struct sock *sk) { struct tcp_sock *tp = tcp_sk(sk); struct tcp_authopt_info *info; @@ -387,16 +448,69 @@ int tcp_set_authopt_key(struct sock *sk, sockptr_t optval, unsigned int optlen) key_info->recv_id = opt.recv_id; key_info->alg_id = opt.alg; key_info->alg = alg; key_info->keylen = opt.keylen; memcpy(key_info->key, opt.key, opt.keylen); + key_info->maclen = alg->maclen; memcpy(&key_info->addr, &opt.addr, sizeof(key_info->addr)); hlist_add_head_rcu(&key_info->node, &info->head); return 0; } +static int tcp_authopt_clone_keys(struct sock *newsk, + const struct sock *oldsk, + struct tcp_authopt_info *new_info, + struct tcp_authopt_info *old_info) +{ + struct tcp_authopt_key_info *old_key; + struct tcp_authopt_key_info *new_key; + + hlist_for_each_entry_rcu(old_key, &old_info->head, node, lockdep_sock_is_held(sk)) { + new_key = sock_kmalloc(newsk, sizeof(*new_key), GFP_ATOMIC); + if (!new_key) + return -ENOMEM; + memcpy(new_key, old_key, sizeof(*new_key)); + tcp_authopt_alg_incref(old_key->alg); + hlist_add_head_rcu(&new_key->node, &new_info->head); + } + + return 0; +} + +/** Called to create accepted sockets. + * + * Need to copy authopt info from listen socket. + */ +int __tcp_authopt_openreq(struct sock *newsk, const struct sock *oldsk, struct request_sock *req) +{ + struct tcp_authopt_info *old_info; + struct tcp_authopt_info *new_info; + int err; + + old_info = rcu_dereference(tcp_sk(oldsk)->authopt_info); + if (!old_info) + return 0; + + new_info = kmalloc(sizeof(*new_info), GFP_ATOMIC | __GFP_ZERO); + if (!new_info) + return -ENOMEM; + + sk_nocaps_add(newsk, NETIF_F_GSO_MASK); + new_info->src_isn = tcp_rsk(req)->snt_isn; + new_info->dst_isn = tcp_rsk(req)->rcv_isn; + INIT_HLIST_HEAD(&new_info->head); + err = tcp_authopt_clone_keys(newsk, oldsk, new_info, old_info); + if (err) { + __tcp_authopt_info_free(newsk, new_info); + return err; + } + rcu_assign_pointer(tcp_sk(newsk)->authopt_info, new_info); + + return 0; +} + /* feed traffic key into shash */ static int tcp_authopt_shash_traffic_key(struct shash_desc *desc, struct sock *sk, struct sk_buff *skb, bool input, @@ -815,10 +929,16 @@ static int tcp_authopt_hash_packet(struct crypto_shash *tfm, return err; return crypto_shash_final(desc, macbuf); } +/** + * __tcp_authopt_calc_mac - Compute packet MAC using key + * + * @macbuf: output buffer. Must be large enough to fit the digestsize of the + * underlying transform before truncation. Please use TCP_AUTHOPT_MAXMACBUF + */ int __tcp_authopt_calc_mac(struct sock *sk, struct sk_buff *skb, struct tcp_authopt_key_info *key, bool input, char *macbuf) @@ -859,5 +979,131 @@ int __tcp_authopt_calc_mac(struct sock *sk, out: tcp_authopt_put_mac_shash(key, mac_tfm); return err; } + +/** + * tcp_authopt_hash - fill in the mac + * + * The key must come from tcp_authopt_select_key. + */ +int tcp_authopt_hash(char *hash_location, + struct tcp_authopt_key_info *key, + struct sock *sk, + struct sk_buff *skb) +{ + /* MAC inside option is truncated to 12 bytes but crypto API needs output + * buffer to be large enough so we use a buffer on the stack. + */ + u8 macbuf[TCP_AUTHOPT_MAXMACBUF]; + int err; + + if (WARN_ON(key->maclen > sizeof(macbuf))) + return -ENOBUFS; + + err = __tcp_authopt_calc_mac(sk, skb, key, false, macbuf); + if (err) { + /* If mac calculation fails and caller doesn't handle the error + * try to make it obvious inside the packet. + */ + memset(hash_location, 0, key->maclen); + return err; + } + memcpy(hash_location, macbuf, key->maclen); + + return 0; +} + +static struct tcp_authopt_key_info *tcp_authopt_lookup_recv(struct sock *sk, + struct sk_buff *skb, + struct tcp_authopt_info *info, + int recv_id) +{ + struct tcp_authopt_key_info *result = NULL; + struct tcp_authopt_key_info *key; + + /* multiple matches will cause occasional failures */ + hlist_for_each_entry_rcu(key, &info->head, node, 0) { + if (recv_id >= 0 && key->recv_id != recv_id) + continue; + if (key->flags & TCP_AUTHOPT_KEY_ADDR_BIND) { + if (sk->sk_family == AF_INET) { + struct sockaddr_in *key_addr = (struct sockaddr_in *)&key->addr; + struct iphdr *iph = (struct iphdr *)skb_network_header(skb); + + if (WARN_ON(key_addr->sin_family != AF_INET)) + continue; + if (WARN_ON(iph->version != 4)) + continue; + if (memcmp(&iph->saddr, &key_addr->sin_addr, sizeof(iph->saddr))) + continue; + } + if (sk->sk_family == AF_INET6) { + struct sockaddr_in6 *key_addr = (struct sockaddr_in6 *)&key->addr; + struct ipv6hdr *iph = (struct ipv6hdr *)skb_network_header(skb); + + if (WARN_ON(key_addr->sin6_family != AF_INET6)) + continue; + if (WARN_ON(iph->version != 6)) + continue; + if (memcmp(&iph->saddr, &key_addr->sin6_addr, sizeof(iph->saddr))) + continue; + } + } + if (result && net_ratelimit()) + pr_warn("ambiguous tcp authentication keys configured for receive\n"); + result = key; + } + + return result; +} + +int __tcp_authopt_inbound_check(struct sock *sk, struct sk_buff *skb, struct tcp_authopt_info *info) +{ + struct tcphdr *th = (struct tcphdr *)skb_transport_header(skb); + struct tcphdr_authopt *opt; + struct tcp_authopt_key_info *key; + u8 macbuf[TCP_AUTHOPT_MAXMACBUF]; + int err; + + opt = (struct tcphdr_authopt *)tcp_authopt_find_option(th); + key = tcp_authopt_lookup_recv(sk, skb, info, opt ? opt->keyid : -1); + + /* nothing found or expected */ + if (!opt && !key) + return 0; + if (!opt && key) { + net_info_ratelimited("TCP Authentication Missing\n"); + return -EINVAL; + } + if (opt && !key) { + /* RFC5925 Section 7.3: + * A TCP-AO implementation MUST allow for configuration of the behavior + * of segments with TCP-AO but that do not match an MKT. The initial + * default of this configuration SHOULD be to silently accept such + * connections. + */ + if (info->flags & TCP_AUTHOPT_FLAG_REJECT_UNEXPECTED) { + net_info_ratelimited("TCP Authentication Unexpected: Rejected\n"); + return -EINVAL; + } else { + net_info_ratelimited("TCP Authentication Unexpected: Accepted\n"); + return 0; + } + } + + /* bad inbound key len */ + if (key->maclen + 4 != opt->len) + return -EINVAL; + + err = __tcp_authopt_calc_mac(sk, skb, key, true, macbuf); + if (err) + return err; + + if (memcmp(macbuf, opt->mac, key->maclen)) { + net_info_ratelimited("TCP Authentication Failed\n"); + return -EINVAL; + } + + return 0; +} diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c index 3f7bd7ae7d7a..e0b51b2f747f 100644 --- a/net/ipv4/tcp_input.c +++ b/net/ipv4/tcp_input.c @@ -70,10 +70,11 @@ #include <linux/sysctl.h> #include <linux/kernel.h> #include <linux/prefetch.h> #include <net/dst.h> #include <net/tcp.h> +#include <net/tcp_authopt.h> #include <net/inet_common.h> #include <linux/ipsec.h> #include <asm/unaligned.h> #include <linux/errqueue.h> #include <trace/events/tcp.h> @@ -5967,18 +5968,34 @@ void tcp_init_transfer(struct sock *sk, int bpf_op, struct sk_buff *skb) if (!icsk->icsk_ca_initialized) tcp_init_congestion_control(sk); tcp_init_buffer_space(sk); } +static void tcp_authopt_finish_connect(struct sock *sk, struct sk_buff *skb) +{ +#ifdef CONFIG_TCP_AUTHOPT + struct tcp_authopt_info *info; + + info = rcu_dereference_protected(tcp_sk(sk)->authopt_info, lockdep_sock_is_held(sk)); + if (!info) + return; + + info->src_isn = ntohl(tcp_hdr(skb)->ack_seq) - 1; + info->dst_isn = ntohl(tcp_hdr(skb)->seq); +#endif +} + void tcp_finish_connect(struct sock *sk, struct sk_buff *skb) { struct tcp_sock *tp = tcp_sk(sk); struct inet_connection_sock *icsk = inet_csk(sk); tcp_set_state(sk, TCP_ESTABLISHED); icsk->icsk_ack.lrcvtime = tcp_jiffies32; + tcp_authopt_finish_connect(sk, skb); + if (skb) { icsk->icsk_af_ops->sk_rx_dst_set(sk, skb); security_inet_conn_established(sk, skb); sk_mark_napi_id(sk, skb); } diff --git a/net/ipv4/tcp_ipv4.c b/net/ipv4/tcp_ipv4.c index 1348615c7576..a1d39183908c 100644 --- a/net/ipv4/tcp_ipv4.c +++ b/net/ipv4/tcp_ipv4.c @@ -2060,10 +2060,13 @@ int tcp_v4_rcv(struct sk_buff *skb) goto discard_and_relse; if (tcp_v4_inbound_md5_hash(sk, skb, dif, sdif)) goto discard_and_relse; + if (tcp_authopt_inbound_check(sk, skb)) + goto discard_and_relse; + nf_reset_ct(skb); if (tcp_filter(sk, skb)) goto discard_and_relse; th = (const struct tcphdr *)skb->data; diff --git a/net/ipv4/tcp_minisocks.c b/net/ipv4/tcp_minisocks.c index 0a4f3f16140a..4d7d86547b0e 100644 --- a/net/ipv4/tcp_minisocks.c +++ b/net/ipv4/tcp_minisocks.c @@ -24,10 +24,11 @@ #include <linux/slab.h> #include <linux/sysctl.h> #include <linux/workqueue.h> #include <linux/static_key.h> #include <net/tcp.h> +#include <net/tcp_authopt.h> #include <net/inet_common.h> #include <net/xfrm.h> #include <net/busy_poll.h> static bool tcp_in_window(u32 seq, u32 end_seq, u32 s_win, u32 e_win) @@ -539,10 +540,11 @@ struct sock *tcp_create_openreq_child(const struct sock *sk, #ifdef CONFIG_TCP_MD5SIG newtp->md5sig_info = NULL; /*XXX*/ if (newtp->af_specific->md5_lookup(sk, newsk)) newtp->tcp_header_len += TCPOLEN_MD5SIG_ALIGNED; #endif + tcp_authopt_openreq(newsk, sk, req); if (skb->len >= TCP_MSS_DEFAULT + newtp->tcp_header_len) newicsk->icsk_ack.last_seg_size = skb->len - newtp->tcp_header_len; newtp->rx_opt.mss_clamp = req->mss; tcp_ecn_openreq_child(newtp, req); newtp->fastopen_req = NULL; diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c index 6d72f3ea48c4..6d73bee349c9 100644 --- a/net/ipv4/tcp_output.c +++ b/net/ipv4/tcp_output.c @@ -37,10 +37,11 @@ #define pr_fmt(fmt) "TCP: " fmt #include <net/tcp.h> #include <net/mptcp.h> +#include <net/tcp_authopt.h> #include <linux/compiler.h> #include <linux/gfp.h> #include <linux/module.h> #include <linux/static_key.h> @@ -411,10 +412,11 @@ static inline bool tcp_urg_mode(const struct tcp_sock *tp) #define OPTION_SACK_ADVERTISE (1 << 0) #define OPTION_TS (1 << 1) #define OPTION_MD5 (1 << 2) #define OPTION_WSCALE (1 << 3) +#define OPTION_AUTHOPT (1 << 4) #define OPTION_FAST_OPEN_COOKIE (1 << 8) #define OPTION_SMC (1 << 9) #define OPTION_MPTCP (1 << 10) static void smc_options_write(__be32 *ptr, u16 *options) @@ -435,16 +437,21 @@ static void smc_options_write(__be32 *ptr, u16 *options) struct tcp_out_options { u16 options; /* bit field of OPTION_* */ u16 mss; /* 0 to disable */ u8 ws; /* window scale, 0 to disable */ u8 num_sack_blocks; /* number of SACK blocks to include */ - u8 hash_size; /* bytes in hash_location */ u8 bpf_opt_len; /* length of BPF hdr option */ +#ifdef CONFIG_TCP_AUTHOPT + u8 authopt_rnextkeyid; /* rnextkey */ +#endif __u8 *hash_location; /* temporary pointer, overloaded */ __u32 tsval, tsecr; /* need to include OPTION_TS */ struct tcp_fastopen_cookie *fastopen_cookie; /* Fast open cookie */ struct mptcp_out_options mptcp; +#ifdef CONFIG_TCP_AUTHOPT + struct tcp_authopt_key_info *authopt_key; +#endif }; static void mptcp_options_write(__be32 *ptr, const struct tcp_sock *tp, struct tcp_out_options *opts) { @@ -617,10 +624,24 @@ static void tcp_options_write(__be32 *ptr, struct tcp_sock *tp, /* overload cookie hash location */ opts->hash_location = (__u8 *)ptr; ptr += 4; } +#ifdef CONFIG_TCP_AUTHOPT + if (unlikely(OPTION_AUTHOPT & options)) { + struct tcp_authopt_key_info *key = opts->authopt_key; + + WARN_ON(!key); + *ptr++ = htonl((TCPOPT_AUTHOPT << 24) | ((4 + key->maclen) << 16) | + (key->send_id << 8) | opts->authopt_rnextkeyid); + /* overload cookie hash location */ + opts->hash_location = (__u8 *)ptr; + /* maclen is currently always 12 but try to align nicely anyway. */ + ptr += (key->maclen + 3) / 4; + } +#endif + if (unlikely(opts->mss)) { *ptr++ = htonl((TCPOPT_MSS << 24) | (TCPOLEN_MSS << 16) | opts->mss); } @@ -752,10 +773,28 @@ static void mptcp_set_option_cond(const struct request_sock *req, } } } } +static int tcp_authopt_init_options(const struct sock *sk, + const struct sock *addr_sk, + struct tcp_out_options *opts) +{ +#ifdef CONFIG_TCP_AUTHOPT + struct tcp_authopt_key_info *key; + + key = tcp_authopt_select_key(sk, addr_sk, &opts->authopt_rnextkeyid); + if (key) { + opts->options |= OPTION_AUTHOPT; + opts->authopt_key = key; + return 4 + key->maclen; + } +#endif + + return 0; +} + /* Compute TCP options for SYN packets. This is not the final * network wire format yet. */ static unsigned int tcp_syn_options(struct sock *sk, struct sk_buff *skb, struct tcp_out_options *opts, @@ -774,10 +813,11 @@ static unsigned int tcp_syn_options(struct sock *sk, struct sk_buff *skb, opts->options |= OPTION_MD5; remaining -= TCPOLEN_MD5SIG_ALIGNED; } } #endif + remaining -= tcp_authopt_init_options(sk, sk, opts); /* We always get an MSS option. The option bytes which will be seen in * normal data packets should timestamps be used, must be in the MSS * advertised. But we subtract them from tp->mss_cache so that * calculations in tcp_sendmsg are simpler etc. So account for this @@ -862,10 +902,11 @@ static unsigned int tcp_synack_options(const struct sock *sk, */ if (synack_type != TCP_SYNACK_COOKIE) ireq->tstamp_ok &= !ireq->sack_ok; } #endif + remaining -= tcp_authopt_init_options(sk, req_to_sk(req), opts); /* We always send an MSS option. */ opts->mss = mss; remaining -= TCPOLEN_MSS_ALIGNED; @@ -930,10 +971,11 @@ static unsigned int tcp_established_options(struct sock *sk, struct sk_buff *skb opts->options |= OPTION_MD5; size += TCPOLEN_MD5SIG_ALIGNED; } } #endif + size += tcp_authopt_init_options(sk, sk, opts); if (likely(tp->rx_opt.tstamp_ok)) { opts->options |= OPTION_TS; opts->tsval = skb ? tcp_skb_timestamp(skb) + tp->tsoffset : 0; opts->tsecr = tp->rx_opt.ts_recent; @@ -1277,10 +1319,14 @@ static int __tcp_transmit_skb(struct sock *sk, struct sk_buff *skb, inet = inet_sk(sk); tcb = TCP_SKB_CB(skb); memset(&opts, 0, sizeof(opts)); +#ifdef CONFIG_TCP_AUTHOPT + /* for tcp_authopt_init_options inside tcp_syn_options or tcp_established_options */ + rcu_read_lock(); +#endif if (unlikely(tcb->tcp_flags & TCPHDR_SYN)) { tcp_options_size = tcp_syn_options(sk, skb, &opts, &md5); } else { tcp_options_size = tcp_established_options(sk, skb, &opts, &md5); @@ -1365,10 +1411,17 @@ static int __tcp_transmit_skb(struct sock *sk, struct sk_buff *skb, sk_nocaps_add(sk, NETIF_F_GSO_MASK); tp->af_specific->calc_md5_hash(opts.hash_location, md5, sk, skb); } #endif +#ifdef CONFIG_TCP_AUTHOPT + if (opts.authopt_key) { + sk_nocaps_add(sk, NETIF_F_GSO_MASK); + tcp_authopt_hash(opts.hash_location, opts.authopt_key, sk, skb); + } + rcu_read_unlock(); +#endif /* BPF prog is the last one writing header option */ bpf_skops_write_hdr_opt(sk, skb, NULL, NULL, 0, &opts); INDIRECT_CALL_INET(icsk->icsk_af_ops->send_check, @@ -1836,12 +1889,21 @@ unsigned int tcp_current_mss(struct sock *sk) u32 mtu = dst_mtu(dst); if (mtu != inet_csk(sk)->icsk_pmtu_cookie) mss_now = tcp_sync_mss(sk, mtu); } +#ifdef CONFIG_TCP_AUTHOPT + /* Even if the result is not used rcu_read_lock is required when scanning for + * tcp authentication keys. Otherwise lockdep will complain. + */ + rcu_read_lock(); +#endif header_len = tcp_established_options(sk, NULL, &opts, &md5) + sizeof(struct tcphdr); +#ifdef CONFIG_TCP_AUTHOPT + rcu_read_unlock(); +#endif /* The mss_cache is sized based on tp->tcp_header_len, which assumes * some common options. If this is an odd packet (because we have SACK * blocks etc) then our calculated header_len will be different, and * we have to adjust mss_now correspondingly */ if (header_len != tp->tcp_header_len) { @@ -3566,10 +3628,14 @@ struct sk_buff *tcp_make_synack(const struct sock *sk, struct dst_entry *dst, } #ifdef CONFIG_TCP_MD5SIG rcu_read_lock(); md5 = tcp_rsk(req)->af_specific->req_md5_lookup(sk, req_to_sk(req)); +#endif +#ifdef CONFIG_TCP_AUTHOPT + /* for tcp_authopt_init_options inside tcp_synack_options */ + rcu_read_lock(); #endif skb_set_hash(skb, tcp_rsk(req)->txhash, PKT_HASH_TYPE_L4); /* bpf program will be interested in the tcp_flags */ TCP_SKB_CB(skb)->tcp_flags = TCPHDR_SYN | TCPHDR_ACK; tcp_header_size = tcp_synack_options(sk, req, mss, skb, &opts, md5, @@ -3603,10 +3669,16 @@ struct sk_buff *tcp_make_synack(const struct sock *sk, struct dst_entry *dst, if (md5) tcp_rsk(req)->af_specific->calc_md5_hash(opts.hash_location, md5, req_to_sk(req), skb); rcu_read_unlock(); #endif +#ifdef CONFIG_TCP_AUTHOPT + /* If signature fails we do nothing */ + if (opts.authopt_key) + tcp_authopt_hash(opts.hash_location, opts.authopt_key, req_to_sk(req), skb); + rcu_read_unlock(); +#endif bpf_skops_write_hdr_opt((struct sock *)sk, skb, req, syn_skb, synack_type, &opts); skb->skb_mstamp_ns = now; diff --git a/net/ipv6/tcp_ipv6.c b/net/ipv6/tcp_ipv6.c index 0ce52d46e4f8..51381a9c2bd5 100644 --- a/net/ipv6/tcp_ipv6.c +++ b/net/ipv6/tcp_ipv6.c @@ -40,10 +40,11 @@ #include <linux/icmpv6.h> #include <linux/random.h> #include <linux/indirect_call_wrapper.h> #include <net/tcp.h> +#include <net/tcp_authopt.h> #include <net/ndisc.h> #include <net/inet6_hashtables.h> #include <net/inet6_connection_sock.h> #include <net/ipv6.h> #include <net/transp_v6.h> @@ -1733,10 +1734,13 @@ INDIRECT_CALLABLE_SCOPE int tcp_v6_rcv(struct sk_buff *skb) goto discard_and_relse; if (tcp_v6_inbound_md5_hash(sk, skb, dif, sdif)) goto discard_and_relse; + if (tcp_authopt_inbound_check(sk, skb)) + goto discard_and_relse; + if (tcp_filter(sk, skb)) goto discard_and_relse; th = (const struct tcphdr *)skb->data; hdr = ipv6_hdr(skb); tcp_v6_fill_cb(skb, hdr, th);
The tcp_authopt features exposes a minimal interface to the rest of the TCP stack. Only a few functions are exposed and if the feature is disabled they return neutral values, avoiding ifdefs in the rest of the code. Add calls into tcp authopt from send, receive and accept code. Signed-off-by: Leonard Crestez <cdleonard@gmail.com> --- include/net/tcp_authopt.h | 56 +++++++++ net/ipv4/tcp_authopt.c | 246 ++++++++++++++++++++++++++++++++++++++ net/ipv4/tcp_input.c | 17 +++ net/ipv4/tcp_ipv4.c | 3 + net/ipv4/tcp_minisocks.c | 2 + net/ipv4/tcp_output.c | 74 +++++++++++- net/ipv6/tcp_ipv6.c | 4 + 7 files changed, 401 insertions(+), 1 deletion(-)