net: Compute protocol sequence numbers and fragment IDs using MD5.

Computers have become a lot faster since we compromised on the
partial MD4 hash which we use currently for performance reasons.

MD5 is a much safer choice, and is inline with both RFC1948 and
other ISS generators (OpenBSD, Solaris, etc.)

Furthermore, only having 24-bits of the sequence number be truly
unpredictable is a very serious limitation.  So the periodic
regeneration and 8-bit counter have been removed.  We compute and
use a full 32-bit sequence number.

For ipv6, DCCP was found to use a 32-bit truncated initial sequence
number (it needs 43-bits) and that is fixed here as well.

Reported-by: Dan Kaminsky <dan@doxpara.com>
Tested-by: Willy Tarreau <w@1wt.eu>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 20 insertions, 0 deletions

diff --git a/include/net/secure_seq.h b/include/net/secure_seq.h
new file mode 100644
index 000000000000..d97f6892c019
--- /dev/null
+++ b/include/net/secure_seq.h
@@ -0,0 +1,20 @@
+#ifndef _NET_SECURE_SEQ
+#define _NET_SECURE_SEQ
+
+#include <linux/types.h>
+
+extern __u32 secure_ip_id(__be32 daddr);
+extern __u32 secure_ipv6_id(const __be32 daddr[4]);
+extern u32 secure_ipv4_port_ephemeral(__be32 saddr, __be32 daddr, __be16 dport);
+extern u32 secure_ipv6_port_ephemeral(const __be32 *saddr, const __be32 *daddr,
+                                      __be16 dport);
+extern __u32 secure_tcp_sequence_number(__be32 saddr, __be32 daddr,
+                                        __be16 sport, __be16 dport);
+extern __u32 secure_tcpv6_sequence_number(__be32 *saddr, __be32 *daddr,
+                                          __be16 sport, __be16 dport);
+extern u64 secure_dccp_sequence_number(__be32 saddr, __be32 daddr,
+                                       __be16 sport, __be16 dport);
+extern u64 secure_dccpv6_sequence_number(__be32 *saddr, __be32 *daddr,
+                                         __be16 sport, __be16 dport);
+
+#endif /* _NET_SECURE_SEQ */