diff options
author | William Allen Simpson <william.allen.simpson@gmail.com> | 2009-12-02 18:25:27 +0000 |
---|---|---|
committer | David S. Miller <davem@davemloft.net> | 2009-12-02 22:07:26 -0800 |
commit | 4957faade11b3a278c3b3cade3411ddc20afa791 (patch) | |
tree | 57f994bab69353baf5f554b89cf9107c3372ecce /net/ipv4 | |
parent | bd0388ae77075026d6a9f9eb6026dfd1d52ce0e9 (diff) | |
download | op-kernel-dev-4957faade11b3a278c3b3cade3411ddc20afa791.zip op-kernel-dev-4957faade11b3a278c3b3cade3411ddc20afa791.tar.gz |
TCPCT part 1g: Responder Cookie => Initiator
Parse incoming TCP_COOKIE option(s).
Calculate <SYN,ACK> TCP_COOKIE option.
Send optional <SYN,ACK> data.
This is a significantly revised implementation of an earlier (year-old)
patch that no longer applies cleanly, with permission of the original
author (Adam Langley):
http://thread.gmane.org/gmane.linux.network/102586
Requires:
TCPCT part 1a: add request_values parameter for sending SYNACK
TCPCT part 1b: generate Responder Cookie secret
TCPCT part 1c: sysctl_tcp_cookie_size, socket option TCP_COOKIE_TRANSACTIONS
TCPCT part 1d: define TCP cookie option, extend existing struct's
TCPCT part 1e: implement socket option TCP_COOKIE_TRANSACTIONS
TCPCT part 1f: Initiator Cookie => Responder
Signed-off-by: William.Allen.Simpson@gmail.com
Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'net/ipv4')
-rw-r--r-- | net/ipv4/syncookies.c | 5 | ||||
-rw-r--r-- | net/ipv4/tcp_input.c | 75 | ||||
-rw-r--r-- | net/ipv4/tcp_ipv4.c | 47 | ||||
-rw-r--r-- | net/ipv4/tcp_minisocks.c | 14 | ||||
-rw-r--r-- | net/ipv4/tcp_output.c | 103 |
5 files changed, 205 insertions, 39 deletions
diff --git a/net/ipv4/syncookies.c b/net/ipv4/syncookies.c index 3146cc4..26399ad 100644 --- a/net/ipv4/syncookies.c +++ b/net/ipv4/syncookies.c @@ -253,6 +253,8 @@ EXPORT_SYMBOL(cookie_check_timestamp); struct sock *cookie_v4_check(struct sock *sk, struct sk_buff *skb, struct ip_options *opt) { + struct tcp_options_received tcp_opt; + u8 *hash_location; struct inet_request_sock *ireq; struct tcp_request_sock *treq; struct tcp_sock *tp = tcp_sk(sk); @@ -263,7 +265,6 @@ struct sock *cookie_v4_check(struct sock *sk, struct sk_buff *skb, int mss; struct rtable *rt; __u8 rcv_wscale; - struct tcp_options_received tcp_opt; if (!sysctl_tcp_syncookies || !th->ack) goto out; @@ -341,7 +342,7 @@ struct sock *cookie_v4_check(struct sock *sk, struct sk_buff *skb, /* check for timestamp cookie support */ memset(&tcp_opt, 0, sizeof(tcp_opt)); - tcp_parse_options(skb, &tcp_opt, 0, &rt->u.dst); + tcp_parse_options(skb, &tcp_opt, &hash_location, 0, &rt->u.dst); if (tcp_opt.saw_tstamp) cookie_check_timestamp(&tcp_opt); diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c index be166e0..57ae96a 100644 --- a/net/ipv4/tcp_input.c +++ b/net/ipv4/tcp_input.c @@ -3698,7 +3698,7 @@ old_ack: * the fast version below fails. */ void tcp_parse_options(struct sk_buff *skb, struct tcp_options_received *opt_rx, - int estab, struct dst_entry *dst) + u8 **hvpp, int estab, struct dst_entry *dst) { unsigned char *ptr; struct tcphdr *th = tcp_hdr(skb); @@ -3785,7 +3785,30 @@ void tcp_parse_options(struct sk_buff *skb, struct tcp_options_received *opt_rx, */ break; #endif - } + case TCPOPT_COOKIE: + /* This option is variable length. + */ + switch (opsize) { + case TCPOLEN_COOKIE_BASE: + /* not yet implemented */ + break; + case TCPOLEN_COOKIE_PAIR: + /* not yet implemented */ + break; + case TCPOLEN_COOKIE_MIN+0: + case TCPOLEN_COOKIE_MIN+2: + case TCPOLEN_COOKIE_MIN+4: + case TCPOLEN_COOKIE_MIN+6: + case TCPOLEN_COOKIE_MAX: + /* 16-bit multiple */ + opt_rx->cookie_plus = opsize; + *hvpp = ptr; + default: + /* ignore option */ + break; + }; + break; + }; ptr += opsize-2; length -= opsize; @@ -3813,17 +3836,20 @@ static int tcp_parse_aligned_timestamp(struct tcp_sock *tp, struct tcphdr *th) * If it is wrong it falls back on tcp_parse_options(). */ static int tcp_fast_parse_options(struct sk_buff *skb, struct tcphdr *th, - struct tcp_sock *tp) + struct tcp_sock *tp, u8 **hvpp) { - if (th->doff == sizeof(struct tcphdr) >> 2) { + /* In the spirit of fast parsing, compare doff directly to constant + * values. Because equality is used, short doff can be ignored here. + */ + if (th->doff == (sizeof(*th) / 4)) { tp->rx_opt.saw_tstamp = 0; return 0; } else if (tp->rx_opt.tstamp_ok && - th->doff == (sizeof(struct tcphdr)>>2)+(TCPOLEN_TSTAMP_ALIGNED>>2)) { + th->doff == ((sizeof(*th) + TCPOLEN_TSTAMP_ALIGNED) / 4)) { if (tcp_parse_aligned_timestamp(tp, th)) return 1; } - tcp_parse_options(skb, &tp->rx_opt, 1, NULL); + tcp_parse_options(skb, &tp->rx_opt, hvpp, 1, NULL); return 1; } @@ -5077,10 +5103,12 @@ out: static int tcp_validate_incoming(struct sock *sk, struct sk_buff *skb, struct tcphdr *th, int syn_inerr) { + u8 *hash_location; struct tcp_sock *tp = tcp_sk(sk); /* RFC1323: H1. Apply PAWS check first. */ - if (tcp_fast_parse_options(skb, th, tp) && tp->rx_opt.saw_tstamp && + if (tcp_fast_parse_options(skb, th, tp, &hash_location) && + tp->rx_opt.saw_tstamp && tcp_paws_discard(sk, skb)) { if (!th->rst) { NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_PAWSESTABREJECTED); @@ -5368,12 +5396,14 @@ discard: static int tcp_rcv_synsent_state_process(struct sock *sk, struct sk_buff *skb, struct tcphdr *th, unsigned len) { - struct tcp_sock *tp = tcp_sk(sk); + u8 *hash_location; struct inet_connection_sock *icsk = inet_csk(sk); - int saved_clamp = tp->rx_opt.mss_clamp; + struct tcp_sock *tp = tcp_sk(sk); struct dst_entry *dst = __sk_dst_get(sk); + struct tcp_cookie_values *cvp = tp->cookie_values; + int saved_clamp = tp->rx_opt.mss_clamp; - tcp_parse_options(skb, &tp->rx_opt, 0, dst); + tcp_parse_options(skb, &tp->rx_opt, &hash_location, 0, dst); if (th->ack) { /* rfc793: @@ -5470,6 +5500,31 @@ static int tcp_rcv_synsent_state_process(struct sock *sk, struct sk_buff *skb, * Change state from SYN-SENT only after copied_seq * is initialized. */ tp->copied_seq = tp->rcv_nxt; + + if (cvp != NULL && + cvp->cookie_pair_size > 0 && + tp->rx_opt.cookie_plus > 0) { + int cookie_size = tp->rx_opt.cookie_plus + - TCPOLEN_COOKIE_BASE; + int cookie_pair_size = cookie_size + + cvp->cookie_desired; + + /* A cookie extension option was sent and returned. + * Note that each incoming SYNACK replaces the + * Responder cookie. The initial exchange is most + * fragile, as protection against spoofing relies + * entirely upon the sequence and timestamp (above). + * This replacement strategy allows the correct pair to + * pass through, while any others will be filtered via + * Responder verification later. + */ + if (sizeof(cvp->cookie_pair) >= cookie_pair_size) { + memcpy(&cvp->cookie_pair[cvp->cookie_desired], + hash_location, cookie_size); + cvp->cookie_pair_size = cookie_pair_size; + } + } + smp_mb(); tcp_set_state(sk, TCP_ESTABLISHED); diff --git a/net/ipv4/tcp_ipv4.c b/net/ipv4/tcp_ipv4.c index a2bcac9..59c911f 100644 --- a/net/ipv4/tcp_ipv4.c +++ b/net/ipv4/tcp_ipv4.c @@ -1213,9 +1213,12 @@ static struct timewait_sock_ops tcp_timewait_sock_ops = { int tcp_v4_conn_request(struct sock *sk, struct sk_buff *skb) { + struct tcp_extend_values tmp_ext; struct tcp_options_received tmp_opt; + u8 *hash_location; struct request_sock *req; struct inet_request_sock *ireq; + struct tcp_sock *tp = tcp_sk(sk); struct dst_entry *dst = NULL; __be32 saddr = ip_hdr(skb)->saddr; __be32 daddr = ip_hdr(skb)->daddr; @@ -1271,15 +1274,49 @@ int tcp_v4_conn_request(struct sock *sk, struct sk_buff *skb) tcp_clear_options(&tmp_opt); tmp_opt.mss_clamp = TCP_MSS_DEFAULT; - tmp_opt.user_mss = tcp_sk(sk)->rx_opt.user_mss; + tmp_opt.user_mss = tp->rx_opt.user_mss; + tcp_parse_options(skb, &tmp_opt, &hash_location, 0, dst); + + if (tmp_opt.cookie_plus > 0 && + tmp_opt.saw_tstamp && + !tp->rx_opt.cookie_out_never && + (sysctl_tcp_cookie_size > 0 || + (tp->cookie_values != NULL && + tp->cookie_values->cookie_desired > 0))) { + u8 *c; + u32 *mess = &tmp_ext.cookie_bakery[COOKIE_DIGEST_WORDS]; + int l = tmp_opt.cookie_plus - TCPOLEN_COOKIE_BASE; + + if (tcp_cookie_generator(&tmp_ext.cookie_bakery[0]) != 0) + goto drop_and_release; + + /* Secret recipe starts with IP addresses */ + *mess++ ^= daddr; + *mess++ ^= saddr; - tcp_parse_options(skb, &tmp_opt, 0, dst); + /* plus variable length Initiator Cookie */ + c = (u8 *)mess; + while (l-- > 0) + *c++ ^= *hash_location++; + +#ifdef CONFIG_SYN_COOKIES + want_cookie = 0; /* not our kind of cookie */ +#endif + tmp_ext.cookie_out_never = 0; /* false */ + tmp_ext.cookie_plus = tmp_opt.cookie_plus; + } else if (!tp->rx_opt.cookie_in_always) { + /* redundant indications, but ensure initialization. */ + tmp_ext.cookie_out_never = 1; /* true */ + tmp_ext.cookie_plus = 0; + } else { + goto drop_and_release; + } + tmp_ext.cookie_in_always = tp->rx_opt.cookie_in_always; if (want_cookie && !tmp_opt.saw_tstamp) tcp_clear_options(&tmp_opt); tmp_opt.tstamp_ok = tmp_opt.saw_tstamp; - tcp_openreq_init(req, &tmp_opt, skb); if (security_inet_conn_request(sk, skb, req)) @@ -1339,7 +1376,9 @@ int tcp_v4_conn_request(struct sock *sk, struct sk_buff *skb) } tcp_rsk(req)->snt_isn = isn; - if (__tcp_v4_send_synack(sk, dst, req, NULL) || want_cookie) + if (__tcp_v4_send_synack(sk, dst, req, + (struct request_values *)&tmp_ext) || + want_cookie) goto drop_and_free; inet_csk_reqsk_queue_hash_add(sk, req, TCP_TIMEOUT_INIT); diff --git a/net/ipv4/tcp_minisocks.c b/net/ipv4/tcp_minisocks.c index 96852af..87accec 100644 --- a/net/ipv4/tcp_minisocks.c +++ b/net/ipv4/tcp_minisocks.c @@ -90,13 +90,14 @@ enum tcp_tw_status tcp_timewait_state_process(struct inet_timewait_sock *tw, struct sk_buff *skb, const struct tcphdr *th) { - struct tcp_timewait_sock *tcptw = tcp_twsk((struct sock *)tw); struct tcp_options_received tmp_opt; + u8 *hash_location; + struct tcp_timewait_sock *tcptw = tcp_twsk((struct sock *)tw); int paws_reject = 0; if (th->doff > (sizeof(*th) >> 2) && tcptw->tw_ts_recent_stamp) { tmp_opt.tstamp_ok = 1; - tcp_parse_options(skb, &tmp_opt, 1, NULL); + tcp_parse_options(skb, &tmp_opt, &hash_location, 1, NULL); if (tmp_opt.saw_tstamp) { tmp_opt.ts_recent = tcptw->tw_ts_recent; @@ -518,15 +519,16 @@ struct sock *tcp_check_req(struct sock *sk, struct sk_buff *skb, struct request_sock *req, struct request_sock **prev) { + struct tcp_options_received tmp_opt; + u8 *hash_location; + struct sock *child; const struct tcphdr *th = tcp_hdr(skb); __be32 flg = tcp_flag_word(th) & (TCP_FLAG_RST|TCP_FLAG_SYN|TCP_FLAG_ACK); int paws_reject = 0; - struct tcp_options_received tmp_opt; - struct sock *child; - if ((th->doff > (sizeof(struct tcphdr)>>2)) && (req->ts_recent)) { + if ((th->doff > (sizeof(*th) >> 2)) && (req->ts_recent)) { tmp_opt.tstamp_ok = 1; - tcp_parse_options(skb, &tmp_opt, 1, NULL); + tcp_parse_options(skb, &tmp_opt, &hash_location, 1, NULL); if (tmp_opt.saw_tstamp) { tmp_opt.ts_recent = req->ts_recent; diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c index 35dd983..2ac8bef 100644 --- a/net/ipv4/tcp_output.c +++ b/net/ipv4/tcp_output.c @@ -655,48 +655,77 @@ static unsigned tcp_synack_options(struct sock *sk, struct request_sock *req, unsigned mss, struct sk_buff *skb, struct tcp_out_options *opts, - struct tcp_md5sig_key **md5) { - unsigned size = 0; + struct tcp_md5sig_key **md5, + struct tcp_extend_values *xvp) +{ struct inet_request_sock *ireq = inet_rsk(req); - char doing_ts; + unsigned remaining = MAX_TCP_OPTION_SPACE; + u8 cookie_plus = (xvp != NULL && !xvp->cookie_out_never) ? + xvp->cookie_plus : + 0; + bool doing_ts = ireq->tstamp_ok; #ifdef CONFIG_TCP_MD5SIG *md5 = tcp_rsk(req)->af_specific->md5_lookup(sk, req); if (*md5) { opts->options |= OPTION_MD5; - size += TCPOLEN_MD5SIG_ALIGNED; + remaining -= TCPOLEN_MD5SIG_ALIGNED; + + /* We can't fit any SACK blocks in a packet with MD5 + TS + * options. There was discussion about disabling SACK + * rather than TS in order to fit in better with old, + * buggy kernels, but that was deemed to be unnecessary. + */ + doing_ts &= !ireq->sack_ok; } #else *md5 = NULL; #endif - /* we can't fit any SACK blocks in a packet with MD5 + TS - options. There was discussion about disabling SACK rather than TS in - order to fit in better with old, buggy kernels, but that was deemed - to be unnecessary. */ - doing_ts = ireq->tstamp_ok && !(*md5 && ireq->sack_ok); - + /* We always send an MSS option. */ opts->mss = mss; - size += TCPOLEN_MSS_ALIGNED; + remaining -= TCPOLEN_MSS_ALIGNED; if (likely(ireq->wscale_ok)) { opts->ws = ireq->rcv_wscale; opts->options |= OPTION_WSCALE; - size += TCPOLEN_WSCALE_ALIGNED; + remaining -= TCPOLEN_WSCALE_ALIGNED; } if (likely(doing_ts)) { opts->options |= OPTION_TS; opts->tsval = TCP_SKB_CB(skb)->when; opts->tsecr = req->ts_recent; - size += TCPOLEN_TSTAMP_ALIGNED; + remaining -= TCPOLEN_TSTAMP_ALIGNED; } if (likely(ireq->sack_ok)) { opts->options |= OPTION_SACK_ADVERTISE; if (unlikely(!doing_ts)) - size += TCPOLEN_SACKPERM_ALIGNED; + remaining -= TCPOLEN_SACKPERM_ALIGNED; } - return size; + /* Similar rationale to tcp_syn_options() applies here, too. + * If the <SYN> options fit, the same options should fit now! + */ + if (*md5 == NULL && + doing_ts && + cookie_plus > TCPOLEN_COOKIE_BASE) { + int need = cookie_plus; /* has TCPOLEN_COOKIE_BASE */ + + if (0x2 & need) { + /* 32-bit multiple */ + need += 2; /* NOPs */ + } + if (need <= remaining) { + opts->options |= OPTION_COOKIE_EXTENSION; + opts->hash_size = cookie_plus - TCPOLEN_COOKIE_BASE; + remaining -= need; + } else { + /* There's no error return, so flag it. */ + xvp->cookie_out_never = 1; /* true */ + opts->hash_size = 0; + } + } + return MAX_TCP_OPTION_SPACE - remaining; } /* Compute TCP options for ESTABLISHED sockets. This is not the @@ -2365,6 +2394,7 @@ struct sk_buff *tcp_make_synack(struct sock *sk, struct dst_entry *dst, struct request_values *rvp) { struct tcp_out_options opts; + struct tcp_extend_values *xvp = tcp_xv(rvp); struct inet_request_sock *ireq = inet_rsk(req); struct tcp_sock *tp = tcp_sk(sk); struct tcphdr *th; @@ -2408,8 +2438,8 @@ struct sk_buff *tcp_make_synack(struct sock *sk, struct dst_entry *dst, #endif TCP_SKB_CB(skb)->when = tcp_time_stamp; tcp_header_size = tcp_synack_options(sk, req, mss, - skb, &opts, &md5) + - sizeof(struct tcphdr); + skb, &opts, &md5, xvp) + + sizeof(*th); skb_push(skb, tcp_header_size); skb_reset_transport_header(skb); @@ -2426,6 +2456,45 @@ struct sk_buff *tcp_make_synack(struct sock *sk, struct dst_entry *dst, */ tcp_init_nondata_skb(skb, tcp_rsk(req)->snt_isn, TCPCB_FLAG_SYN | TCPCB_FLAG_ACK); + + if (OPTION_COOKIE_EXTENSION & opts.options) { + const struct tcp_cookie_values *cvp = tp->cookie_values; + + if (cvp != NULL && + cvp->s_data_constant && + cvp->s_data_desired > 0) { + u8 *buf = skb_put(skb, cvp->s_data_desired); + + /* copy data directly from the listening socket. */ + memcpy(buf, cvp->s_data_payload, cvp->s_data_desired); + TCP_SKB_CB(skb)->end_seq += cvp->s_data_desired; + } + + if (opts.hash_size > 0) { + __u32 workspace[SHA_WORKSPACE_WORDS]; + u32 *mess = &xvp->cookie_bakery[COOKIE_DIGEST_WORDS]; + u32 *tail = &mess[COOKIE_MESSAGE_WORDS-1]; + + /* Secret recipe depends on the Timestamp, (future) + * Sequence and Acknowledgment Numbers, Initiator + * Cookie, and others handled by IP variant caller. + */ + *tail-- ^= opts.tsval; + *tail-- ^= tcp_rsk(req)->rcv_isn + 1; + *tail-- ^= TCP_SKB_CB(skb)->seq + 1; + + /* recommended */ + *tail-- ^= ((th->dest << 16) | th->source); + *tail-- ^= (u32)cvp; /* per sockopt */ + + sha_transform((__u32 *)&xvp->cookie_bakery[0], + (char *)mess, + &workspace[0]); + opts.hash_location = + (__u8 *)&xvp->cookie_bakery[0]; + } + } + th->seq = htonl(TCP_SKB_CB(skb)->seq); th->ack_seq = htonl(tcp_rsk(req)->rcv_isn + 1); |