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TCPCT part 1g: Responder Cookie => Initiator

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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>
This commit is contained in:
William Allen Simpson 2009-12-02 18:25:27 +00:00 committed by David S. Miller
parent bd0388ae77
commit 4957faade1
8 changed files with 259 additions and 43 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

1
include/net/tcp.h
View File

@ -407,6 +407,7 @@ extern int tcp_recvmsg(struct kiocb *iocb, struct sock *sk,
extern void tcp_parse_options(struct sk_buff *skb,
struct tcp_options_received *opt_rx,
u8 **hvpp,
int estab,
struct dst_entry *dst);

5
net/ipv4/syncookies.c
View File

@ -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);

75
net/ipv4/tcp_input.c
View File

@ -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);

47
net/ipv4/tcp_ipv4.c
View File

@ -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);
tcp_parse_options(skb, &tmp_opt, 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;
/* 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);

14
net/ipv4/tcp_minisocks.c
View File

@ -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;

103
net/ipv4/tcp_output.c
View File

@ -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);

5
net/ipv6/syncookies.c
View File

@ -159,6 +159,8 @@ static inline int cookie_check(struct sk_buff *skb, __u32 cookie)
struct sock *cookie_v6_check(struct sock *sk, struct sk_buff *skb)
{
struct tcp_options_received tcp_opt;
u8 *hash_location;
struct inet_request_sock *ireq;
struct inet6_request_sock *ireq6;
struct tcp_request_sock *treq;
@ -171,7 +173,6 @@ struct sock *cookie_v6_check(struct sock *sk, struct sk_buff *skb)
int mss;
struct dst_entry *dst;
__u8 rcv_wscale;
struct tcp_options_received tcp_opt;
if (!sysctl_tcp_syncookies || !th->ack)
goto out;
@ -254,7 +255,7 @@ struct sock *cookie_v6_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, dst);
tcp_parse_options(skb, &tcp_opt, &hash_location, 0, dst);
if (tcp_opt.saw_tstamp)
cookie_check_timestamp(&tcp_opt);

52
net/ipv6/tcp_ipv6.c
View File

@ -1162,7 +1162,9 @@ static struct sock *tcp_v6_hnd_req(struct sock *sk,struct sk_buff *skb)
*/
static int tcp_v6_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 inet6_request_sock *treq;
struct ipv6_pinfo *np = inet6_sk(sk);
@ -1206,8 +1208,52 @@ static int tcp_v6_conn_request(struct sock *sk, struct sk_buff *skb)
tcp_clear_options(&tmp_opt);
tmp_opt.mss_clamp = IPV6_MIN_MTU - sizeof(struct tcphdr) - sizeof(struct ipv6hdr);
tmp_opt.user_mss = tp->rx_opt.user_mss;
tcp_parse_options(skb, &tmp_opt, &hash_location, 0, dst);
tcp_parse_options(skb, &tmp_opt, 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 *d;
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_free;
/* Secret recipe starts with IP addresses */
d = &ipv6_hdr(skb)->daddr.s6_addr32[0];
*mess++ ^= *d++;
*mess++ ^= *d++;
*mess++ ^= *d++;
*mess++ ^= *d++;
d = &ipv6_hdr(skb)->saddr.s6_addr32[0];
*mess++ ^= *d++;
*mess++ ^= *d++;
*mess++ ^= *d++;
*mess++ ^= *d++;
/* 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_free;
}
tmp_ext.cookie_in_always = tp->rx_opt.cookie_in_always;
if (want_cookie && !tmp_opt.saw_tstamp)
tcp_clear_options(&tmp_opt);
@ -1244,7 +1290,9 @@ static int tcp_v6_conn_request(struct sock *sk, struct sk_buff *skb)
security_inet_conn_request(sk, skb, req);
if (tcp_v6_send_synack(sk, req, NULL) || want_cookie)
if (tcp_v6_send_synack(sk, req,
(struct request_values *)&tmp_ext) ||
want_cookie)
goto drop_and_free;
inet6_csk_reqsk_queue_hash_add(sk, req, TCP_TIMEOUT_INIT);