tcp: Fix MD5 signatures for non-linear skbs

Currently, the MD5 code assumes that the SKBs are linear and, in the case
that they aren't, happily goes off and hashes off the end of the SKB and
into random memory.

Reported by Stephen Hemminger in [1]. Advice thanks to Stephen and Evgeniy
Polyakov. Also includes a couple of missed route_caps from Stephen's patch
in [2].

[1] http://marc.info/?l=linux-netdev&m=121445989106145&w=2
[2] http://marc.info/?l=linux-netdev&m=121459157816964&w=2

Signed-off-by: Adam Langley <agl@imperialviolet.org>
Acked-by: Stephen Hemminger <shemminger@vyatta.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 83 insertions, 44 deletions

diff --git a/net/ipv6/tcp_ipv6.c b/net/ipv6/tcp_ipv6.c
index ca5b93a5c02a..ae45f9835014 100644
--- a/net/ipv6/tcp_ipv6.c
+++ b/net/ipv6/tcp_ipv6.c
@@ -736,64 +736,105 @@ static int tcp_v6_parse_md5_keys (struct sock *sk, char __user *optval,
         return tcp_v6_md5_do_add(sk, &sin6->sin6_addr, newkey, cmd.tcpm_keylen);
 }
 
-static int tcp_v6_do_calc_md5_hash(char *md5_hash, struct tcp_md5sig_key *key,
-                                   struct in6_addr *saddr,
-                                   struct in6_addr *daddr,
-                                   struct tcphdr *th, unsigned int tcplen)
+static int tcp_v6_md5_hash_pseudoheader(struct tcp_md5sig_pool *hp,
+                                        struct in6_addr *daddr,
+                                        struct in6_addr *saddr, int nbytes)
 {
-        struct tcp_md5sig_pool *hp;
         struct tcp6_pseudohdr *bp;
-        int err;
-
-        hp = tcp_get_md5sig_pool();
-        if (!hp) {
-                printk(KERN_WARNING "%s(): hash pool not found...\n", __func__);
-                goto clear_hash_noput;
-        }
+        struct scatterlist sg;
 
         bp = &hp->md5_blk.ip6;
-
         /* 1. TCP pseudo-header (RFC2460) */
         ipv6_addr_copy(&bp->saddr, saddr);
         ipv6_addr_copy(&bp->daddr, daddr);
-        bp->len = htonl(tcplen);
-        bp->protocol = htonl(IPPROTO_TCP);
+        bp->protocol = cpu_to_be32(IPPROTO_TCP);
+        bp->len = cpu_to_be16(nbytes);
 
-        err = tcp_calc_md5_hash(md5_hash, key, sizeof(*bp),
-                                th, tcplen, hp);
+        sg_init_one(&sg, bp, sizeof(*bp));
+        return crypto_hash_update(&hp->md5_desc, &sg, sizeof(*bp));
+}
 
-        if (err)
+static int tcp_v6_md5_hash_hdr(char *md5_hash, struct tcp_md5sig_key *key,
+                               struct in6_addr *daddr, struct in6_addr *saddr,
+                               struct tcphdr *th)
+{
+        struct tcp_md5sig_pool *hp;
+        struct hash_desc *desc;
+
+        hp = tcp_get_md5sig_pool();
+        if (!hp)
+                goto clear_hash_noput;
+        desc = &hp->md5_desc;
+
+        if (crypto_hash_init(desc))
+                goto clear_hash;
+        if (tcp_v6_md5_hash_pseudoheader(hp, daddr, saddr, th->doff << 2))
+                goto clear_hash;
+        if (tcp_md5_hash_header(hp, th))
+                goto clear_hash;
+        if (tcp_md5_hash_key(hp, key))
+                goto clear_hash;
+        if (crypto_hash_final(desc, md5_hash))
                 goto clear_hash;
 
-        /* Free up the crypto pool */
         tcp_put_md5sig_pool();
-out:
         return 0;
+
 clear_hash:
         tcp_put_md5sig_pool();
 clear_hash_noput:
         memset(md5_hash, 0, 16);
-        goto out;
+        return 1;
 }
 
-static int tcp_v6_calc_md5_hash(char *md5_hash, struct tcp_md5sig_key *key,
-                                struct sock *sk,
-                                struct dst_entry *dst,
-                                struct request_sock *req,
-                                struct tcphdr *th, unsigned int tcplen)
+static int tcp_v6_md5_hash_skb(char *md5_hash, struct tcp_md5sig_key *key,
+                               struct sock *sk, struct request_sock *req,
+                               struct sk_buff *skb)
 {
         struct in6_addr *saddr, *daddr;
+        struct tcp_md5sig_pool *hp;
+        struct hash_desc *desc;
+        struct tcphdr *th = tcp_hdr(skb);
 
         if (sk) {
                 saddr = &inet6_sk(sk)->saddr;
                 daddr = &inet6_sk(sk)->daddr;
-        } else {
+        } else if (req) {
                 saddr = &inet6_rsk(req)->loc_addr;
                 daddr = &inet6_rsk(req)->rmt_addr;
+        } else {
+                struct ipv6hdr *ip6h = ipv6_hdr(skb);
+                saddr = &ip6h->saddr;
+                daddr = &ip6h->daddr;
         }
-        return tcp_v6_do_calc_md5_hash(md5_hash, key,
-                                       saddr, daddr,
-                                       th, tcplen);
+
+        hp = tcp_get_md5sig_pool();
+        if (!hp)
+                goto clear_hash_noput;
+        desc = &hp->md5_desc;
+
+        if (crypto_hash_init(desc))
+                goto clear_hash;
+
+        if (tcp_v6_md5_hash_pseudoheader(hp, daddr, saddr, skb->len))
+                goto clear_hash;
+        if (tcp_md5_hash_header(hp, th))
+                goto clear_hash;
+        if (tcp_md5_hash_skb_data(hp, skb, th->doff << 2))
+                goto clear_hash;
+        if (tcp_md5_hash_key(hp, key))
+                goto clear_hash;
+        if (crypto_hash_final(desc, md5_hash))
+                goto clear_hash;
+
+        tcp_put_md5sig_pool();
+        return 0;
+
+clear_hash:
+        tcp_put_md5sig_pool();
+clear_hash_noput:
+        memset(md5_hash, 0, 16);
+        return 1;
 }
 
 static int tcp_v6_inbound_md5_hash (struct sock *sk, struct sk_buff *skb)
@@ -834,10 +875,10 @@ static int tcp_v6_inbound_md5_hash (struct sock *sk, struct sk_buff *skb)
         }
 
         /* check the signature */
-        genhash = tcp_v6_do_calc_md5_hash(newhash,
-                                          hash_expected,
-                                          &ip6h->saddr, &ip6h->daddr,
-                                          th, skb->len);
+        genhash = tcp_v6_md5_hash_skb(newhash,
+                                      hash_expected,
+                                      NULL, NULL, skb);
+
         if (genhash || memcmp(hash_location, newhash, 16) != 0) {
                 if (net_ratelimit()) {
                         printk(KERN_INFO "MD5 Hash %s for "
@@ -974,10 +1015,9 @@ static void tcp_v6_send_reset(struct sock *sk, struct sk_buff *skb)
                                (TCPOPT_NOP << 16) |
                                (TCPOPT_MD5SIG << 8) |
                                TCPOLEN_MD5SIG);
-                tcp_v6_do_calc_md5_hash((__u8 *)&opt[1], key,
-                                        &ipv6_hdr(skb)->daddr,
-                                        &ipv6_hdr(skb)->saddr,
-                                        t1, tot_len);
+                tcp_v6_md5_hash_hdr((__u8 *)&opt[1], key,
+                                    &ipv6_hdr(skb)->daddr,
+                                    &ipv6_hdr(skb)->saddr, t1);
         }
 #endif
 
@@ -1064,10 +1104,9 @@ static void tcp_v6_send_ack(struct sk_buff *skb, u32 seq, u32 ack, u32 win, u32
         if (key) {
                 *topt++ = htonl((TCPOPT_NOP << 24) | (TCPOPT_NOP << 16) |
                                 (TCPOPT_MD5SIG << 8) | TCPOLEN_MD5SIG);
-                tcp_v6_do_calc_md5_hash((__u8 *)topt, key,
-                                        &ipv6_hdr(skb)->daddr,
-                                        &ipv6_hdr(skb)->saddr,
-                                        t1, tot_len);
+                tcp_v6_md5_hash_hdr((__u8 *)topt, key,
+                                    &ipv6_hdr(skb)->daddr,
+                                    &ipv6_hdr(skb)->saddr, t1);
         }
 #endif
 
@@ -1783,7 +1822,7 @@ static struct inet_connection_sock_af_ops ipv6_specific = {
 #ifdef CONFIG_TCP_MD5SIG
 static struct tcp_sock_af_ops tcp_sock_ipv6_specific = {
         .md5_lookup     =       tcp_v6_md5_lookup,
-        .calc_md5_hash  =       tcp_v6_calc_md5_hash,
+        .calc_md5_hash  =       tcp_v6_md5_hash_skb,
         .md5_add        =       tcp_v6_md5_add_func,
         .md5_parse      =       tcp_v6_parse_md5_keys,
 };
@@ -1815,7 +1854,7 @@ static struct inet_connection_sock_af_ops ipv6_mapped = {
 #ifdef CONFIG_TCP_MD5SIG
 static struct tcp_sock_af_ops tcp_sock_ipv6_mapped_specific = {
         .md5_lookup     =       tcp_v4_md5_lookup,
-        .calc_md5_hash  =       tcp_v4_calc_md5_hash,
+        .calc_md5_hash  =       tcp_v4_md5_hash_skb,
         .md5_add        =       tcp_v6_md5_add_func,
         .md5_parse      =       tcp_v6_parse_md5_keys,
 };