TCP MD5 signatures on sparc64 (big-endian) completely fail on current
kernel releases in interoperability with Cisco/Foundry or other
little-endian linux systems.
The root cause is a cast in the return statement of tcp_v4_md5_do_lookup,
where a tcp4_md5sig_key is casted onto tcp_md5sig_key without proper
conversion. On little-endian systems the upper 8 bits are cut of which
yields the expected behaviour. However, on big-endian systems (like
sparc64) only the most significant 8 bits are preserved. Since
TCP_MD5SIG_MAXKEYLEN is 80, this always yields 0.
In the calculation of the md5 signature afterwards the key is therefore
not appended to the tcp segment which could result in a security problem
since only the presence of a md5 signature is checked, and the key itself
doesn't matter.
--- linux.old/include/net/tcp.h 2007-09-28 21:43:26.000000000 +0200 +++
linux/include/net/tcp.h 2007-09-28 21:45:35.000000000 +0200 @@ -1055,6
+1055,7 @@ static inline void clear_all_retrans_hin
struct crypto_hash;
/* - key database */
+/* this should be compatible with the head of the following two structs */
struct tcp_md5sig_key {
u8 *key;
u8 keylen;
@@ -1062,13 +1063,13 @@ struct tcp_md5sig_key {
struct tcp4_md5sig_key {
u8 *key;
- u16 keylen;
+ u8 keylen;
__be32 addr;
};
struct tcp6_md5sig_key {
u8 *key;
- u16 keylen;
+ u8 keylen;
#if 0
u32 scope_id; /* XXX */
#endif
Signed-off-by: Peter Lieven <[email protected]>
Signed-off-by: Matthias M. Dellweg <[email protected]>
From: "Peter Lieven" <[email protected]>
Date: Fri, 28 Sep 2007 22:42:25 +0200 (CEST)
> TCP MD5 signatures on sparc64 (big-endian) completely fail on current
> kernel releases in interoperability with Cisco/Foundry or other
> little-endian linux systems.
>
> The root cause is a cast in the return statement of tcp_v4_md5_do_lookup,
> where a tcp4_md5sig_key is casted onto tcp_md5sig_key without proper
> conversion. On little-endian systems the upper 8 bits are cut of which
> yields the expected behaviour. However, on big-endian systems (like
> sparc64) only the most significant 8 bits are preserved. Since
> TCP_MD5SIG_MAXKEYLEN is 80, this always yields 0.
>
> In the calculation of the md5 signature afterwards the key is therefore
> not appended to the tcp segment which could result in a security problem
> since only the presence of a md5 signature is checked, and the key itself
> doesn't matter.
Thanks for finding this bug.
> --- linux.old/include/net/tcp.h 2007-09-28 21:43:26.000000000 +0200 +++
> linux/include/net/tcp.h 2007-09-28 21:45:35.000000000 +0200 @@ -1055,6
> +1055,7 @@ static inline void clear_all_retrans_hin
I'll have to apply this patch by hand because your email client
completely corrupted the patch.
> Signed-off-by: Peter Lieven <[email protected]>
> Signed-off-by: Matthias M. Dellweg <[email protected]>
Thanks again.
From: David Miller <[email protected]>
Date: Fri, 28 Sep 2007 14:20:15 -0700 (PDT)
> Thanks for finding this bug.
>
> > --- linux.old/include/net/tcp.h 2007-09-28 21:43:26.000000000 +0200 +++
> > linux/include/net/tcp.h 2007-09-28 21:45:35.000000000 +0200 @@ -1055,6
> > +1055,7 @@ static inline void clear_all_retrans_hin
>
> I'll have to apply this patch by hand because your email client
> completely corrupted the patch.
Actually, I think I'm going to put in a slightly different
fix.
If tcp4_md5sig_key and tcp6_md5sig_key have to begin with exacytly
tcp_md5sig_key's only two members, we should fully tell this
explicitly to the compiler and remove those ugly casts.
The casts are the real bug.
Here is the patch I will use after some testing:
diff --git a/include/net/tcp.h b/include/net/tcp.h
index 185c7ec..54053de 100644
--- a/include/net/tcp.h
+++ b/include/net/tcp.h
@@ -1059,14 +1059,12 @@ struct tcp_md5sig_key {
};
struct tcp4_md5sig_key {
- u8 *key;
- u16 keylen;
+ struct tcp_md5sig_key base;
__be32 addr;
};
struct tcp6_md5sig_key {
- u8 *key;
- u16 keylen;
+ struct tcp_md5sig_key base;
#if 0
u32 scope_id; /* XXX */
#endif
diff --git a/net/ipv4/tcp_ipv4.c b/net/ipv4/tcp_ipv4.c
index 9c94627..e089a97 100644
--- a/net/ipv4/tcp_ipv4.c
+++ b/net/ipv4/tcp_ipv4.c
@@ -833,8 +833,7 @@ static struct tcp_md5sig_key *
return NULL;
for (i = 0; i < tp->md5sig_info->entries4; i++) {
if (tp->md5sig_info->keys4[i].addr == addr)
- return (struct tcp_md5sig_key *)
- &tp->md5sig_info->keys4[i];
+ return &tp->md5sig_info->keys4[i].base;
}
return NULL;
}
@@ -865,9 +864,9 @@ int tcp_v4_md5_do_add(struct sock *sk, __be32 addr,
key = (struct tcp4_md5sig_key *)tcp_v4_md5_do_lookup(sk, addr);
if (key) {
/* Pre-existing entry - just update that one. */
- kfree(key->key);
- key->key = newkey;
- key->keylen = newkeylen;
+ kfree(key->base.key);
+ key->base.key = newkey;
+ key->base.keylen = newkeylen;
} else {
struct tcp_md5sig_info *md5sig;
@@ -906,9 +905,9 @@ int tcp_v4_md5_do_add(struct sock *sk, __be32 addr,
md5sig->alloced4++;
}
md5sig->entries4++;
- md5sig->keys4[md5sig->entries4 - 1].addr = addr;
- md5sig->keys4[md5sig->entries4 - 1].key = newkey;
- md5sig->keys4[md5sig->entries4 - 1].keylen = newkeylen;
+ md5sig->keys4[md5sig->entries4 - 1].addr = addr;
+ md5sig->keys4[md5sig->entries4 - 1].base.key = newkey;
+ md5sig->keys4[md5sig->entries4 - 1].base.keylen = newkeylen;
}
return 0;
}
@@ -930,7 +929,7 @@ int tcp_v4_md5_do_del(struct sock *sk, __be32 addr)
for (i = 0; i < tp->md5sig_info->entries4; i++) {
if (tp->md5sig_info->keys4[i].addr == addr) {
/* Free the key */
- kfree(tp->md5sig_info->keys4[i].key);
+ kfree(tp->md5sig_info->keys4[i].base.key);
tp->md5sig_info->entries4--;
if (tp->md5sig_info->entries4 == 0) {
@@ -964,7 +963,7 @@ static void tcp_v4_clear_md5_list(struct sock *sk)
if (tp->md5sig_info->entries4) {
int i;
for (i = 0; i < tp->md5sig_info->entries4; i++)
- kfree(tp->md5sig_info->keys4[i].key);
+ kfree(tp->md5sig_info->keys4[i].base.key);
tp->md5sig_info->entries4 = 0;
tcp_free_md5sig_pool();
}
diff --git a/net/ipv6/tcp_ipv6.c b/net/ipv6/tcp_ipv6.c
index 0f7defb..3e06799 100644
--- a/net/ipv6/tcp_ipv6.c
+++ b/net/ipv6/tcp_ipv6.c
@@ -539,7 +539,7 @@ static struct tcp_md5sig_key *tcp_v6_md5_do_lookup(struct sock *sk,
for (i = 0; i < tp->md5sig_info->entries6; i++) {
if (ipv6_addr_cmp(&tp->md5sig_info->keys6[i].addr, addr) == 0)
- return (struct tcp_md5sig_key *)&tp->md5sig_info->keys6[i];
+ return &tp->md5sig_info->keys6[i].base;
}
return NULL;
}
@@ -567,9 +567,9 @@ static int tcp_v6_md5_do_add(struct sock *sk, struct in6_addr *peer,
key = (struct tcp6_md5sig_key*) tcp_v6_md5_do_lookup(sk, peer);
if (key) {
/* modify existing entry - just update that one */
- kfree(key->key);
- key->key = newkey;
- key->keylen = newkeylen;
+ kfree(key->base.key);
+ key->base.key = newkey;
+ key->base.keylen = newkeylen;
} else {
/* reallocate new list if current one is full. */
if (!tp->md5sig_info) {
@@ -603,8 +603,8 @@ static int tcp_v6_md5_do_add(struct sock *sk, struct in6_addr *peer,
ipv6_addr_copy(&tp->md5sig_info->keys6[tp->md5sig_info->entries6].addr,
peer);
- tp->md5sig_info->keys6[tp->md5sig_info->entries6].key = newkey;
- tp->md5sig_info->keys6[tp->md5sig_info->entries6].keylen = newkeylen;
+ tp->md5sig_info->keys6[tp->md5sig_info->entries6].base.key = newkey;
+ tp->md5sig_info->keys6[tp->md5sig_info->entries6].base.keylen = newkeylen;
tp->md5sig_info->entries6++;
}
@@ -626,7 +626,7 @@ static int tcp_v6_md5_do_del(struct sock *sk, struct in6_addr *peer)
for (i = 0; i < tp->md5sig_info->entries6; i++) {
if (ipv6_addr_cmp(&tp->md5sig_info->keys6[i].addr, peer) == 0) {
/* Free the key */
- kfree(tp->md5sig_info->keys6[i].key);
+ kfree(tp->md5sig_info->keys6[i].base.key);
tp->md5sig_info->entries6--;
if (tp->md5sig_info->entries6 == 0) {
@@ -657,7 +657,7 @@ static void tcp_v6_clear_md5_list (struct sock *sk)
if (tp->md5sig_info->entries6) {
for (i = 0; i < tp->md5sig_info->entries6; i++)
- kfree(tp->md5sig_info->keys6[i].key);
+ kfree(tp->md5sig_info->keys6[i].base.key);
tp->md5sig_info->entries6 = 0;
tcp_free_md5sig_pool();
}
@@ -668,7 +668,7 @@ static void tcp_v6_clear_md5_list (struct sock *sk)
if (tp->md5sig_info->entries4) {
for (i = 0; i < tp->md5sig_info->entries4; i++)
- kfree(tp->md5sig_info->keys4[i].key);
+ kfree(tp->md5sig_info->keys4[i].base.key);
tp->md5sig_info->entries4 = 0;
tcp_free_md5sig_pool();
}
Hi David,
while reviewing the tcp_md5-related code further i came across with another
two of these casts which you probably have missed. I don't actually think
that they impose a problem by now, but as you said we should remove them.
Matthias
--- linux-2.6.23.1.orig/net/ipv4/tcp_ipv4.c 2007-10-16 17:25:05.000000000 +0200
+++ linux-2.6.23.1/net/ipv4/tcp_ipv4.c 2007-10-16 17:50:05.000000000 +0200
@@ -857,16 +857,16 @@ int tcp_v4_md5_do_add(struct sock *sk, _
u8 *newkey, u8 newkeylen)
{
/* Add Key to the list */
- struct tcp4_md5sig_key *key;
+ struct tcp_md5sig_key *key;
struct tcp_sock *tp = tcp_sk(sk);
struct tcp4_md5sig_key *keys;
- key = (struct tcp4_md5sig_key *)tcp_v4_md5_do_lookup(sk, addr);
+ key = tcp_v4_md5_do_lookup(sk, addr);
if (key) {
/* Pre-existing entry - just update that one. */
- kfree(key->base.key);
- key->base.key = newkey;
- key->base.keylen = newkeylen;
+ kfree(key->key);
+ key->key = newkey;
+ key->keylen = newkeylen;
} else {
struct tcp_md5sig_info *md5sig;
--- linux-2.6.23.1.orig/net/ipv6/tcp_ipv6.c 2007-10-16 17:47:57.000000000 +0200
+++ linux-2.6.23.1/net/ipv6/tcp_ipv6.c 2007-10-16 17:49:25.000000000 +0200
@@ -560,16 +560,16 @@ static int tcp_v6_md5_do_add(struct sock
char *newkey, u8 newkeylen)
{
/* Add key to the list */
- struct tcp6_md5sig_key *key;
+ struct tcp_md5sig_key *key;
struct tcp_sock *tp = tcp_sk(sk);
struct tcp6_md5sig_key *keys;
- key = (struct tcp6_md5sig_key*) tcp_v6_md5_do_lookup(sk, peer);
+ key = tcp_v6_md5_do_lookup(sk, peer);
if (key) {
/* modify existing entry - just update that one */
- kfree(key->base.key);
- key->base.key = newkey;
- key->base.keylen = newkeylen;
+ kfree(key->key);
+ key->key = newkey;
+ key->keylen = newkeylen;
} else {
/* reallocate new list if current one is full. */
if (!tp->md5sig_info) {
Signed-off-by: Matthias M. Dellweg <[email protected]>
From: Matthias Dellweg <[email protected]>
Date: Tue, 16 Oct 2007 18:47:56 +0200
> while reviewing the tcp_md5-related code further i came across with another
> two of these casts which you probably have missed. I don't actually think
> that they impose a problem by now, but as you said we should remove them.
I'll apply this patch, thanks Matthias.