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>
diff --git a/net/core/secure_seq.c b/net/core/secure_seq.c
new file mode 100644
index 0000000..45329d7
--- /dev/null
+++ b/net/core/secure_seq.c
@@ -0,0 +1,184 @@
+#include <linux/kernel.h>
+#include <linux/init.h>
+#include <linux/cryptohash.h>
+#include <linux/module.h>
+#include <linux/cache.h>
+#include <linux/random.h>
+#include <linux/hrtimer.h>
+#include <linux/ktime.h>
+#include <linux/string.h>
+
+#include <net/secure_seq.h>
+
+static u32 net_secret[MD5_MESSAGE_BYTES / 4] ____cacheline_aligned;
+
+static int __init net_secret_init(void)
+{
+ get_random_bytes(net_secret, sizeof(net_secret));
+ return 0;
+}
+late_initcall(net_secret_init);
+
+static u32 seq_scale(u32 seq)
+{
+ /*
+ * As close as possible to RFC 793, which
+ * suggests using a 250 kHz clock.
+ * Further reading shows this assumes 2 Mb/s networks.
+ * For 10 Mb/s Ethernet, a 1 MHz clock is appropriate.
+ * For 10 Gb/s Ethernet, a 1 GHz clock should be ok, but
+ * we also need to limit the resolution so that the u32 seq
+ * overlaps less than one time per MSL (2 minutes).
+ * Choosing a clock of 64 ns period is OK. (period of 274 s)
+ */
+ return seq + (ktime_to_ns(ktime_get_real()) >> 6);
+}
+
+#if defined(CONFIG_IPV6) || defined(CONFIG_IPV6_MODULE)
+__u32 secure_tcpv6_sequence_number(__be32 *saddr, __be32 *daddr,
+ __be16 sport, __be16 dport)
+{
+ u32 secret[MD5_MESSAGE_BYTES / 4];
+ u32 hash[MD5_DIGEST_WORDS];
+ u32 i;
+
+ memcpy(hash, saddr, 16);
+ for (i = 0; i < 4; i++)
+ secret[i] = net_secret[i] + daddr[i];
+ secret[4] = net_secret[4] +
+ (((__force u16)sport << 16) + (__force u16)dport);
+ for (i = 5; i < MD5_MESSAGE_BYTES / 4; i++)
+ secret[i] = net_secret[i];
+
+ md5_transform(hash, secret);
+
+ return seq_scale(hash[0]);
+}
+EXPORT_SYMBOL(secure_tcpv6_sequence_number);
+
+u32 secure_ipv6_port_ephemeral(const __be32 *saddr, const __be32 *daddr,
+ __be16 dport)
+{
+ u32 secret[MD5_MESSAGE_BYTES / 4];
+ u32 hash[MD5_DIGEST_WORDS];
+ u32 i;
+
+ memcpy(hash, saddr, 16);
+ for (i = 0; i < 4; i++)
+ secret[i] = net_secret[i] + (__force u32) daddr[i];
+ secret[4] = net_secret[4] + (__force u32)dport;
+ for (i = 5; i < MD5_MESSAGE_BYTES / 4; i++)
+ secret[i] = net_secret[i];
+
+ md5_transform(hash, secret);
+
+ return hash[0];
+}
+#endif
+
+#ifdef CONFIG_INET
+__u32 secure_ip_id(__be32 daddr)
+{
+ u32 hash[MD5_DIGEST_WORDS];
+
+ hash[0] = (__force __u32) daddr;
+ hash[1] = net_secret[13];
+ hash[2] = net_secret[14];
+ hash[3] = net_secret[15];
+
+ md5_transform(hash, net_secret);
+
+ return hash[0];
+}
+
+__u32 secure_ipv6_id(const __be32 daddr[4])
+{
+ __u32 hash[4];
+
+ memcpy(hash, daddr, 16);
+ md5_transform(hash, net_secret);
+
+ return hash[0];
+}
+
+__u32 secure_tcp_sequence_number(__be32 saddr, __be32 daddr,
+ __be16 sport, __be16 dport)
+{
+ u32 hash[MD5_DIGEST_WORDS];
+
+ hash[0] = (__force u32)saddr;
+ hash[1] = (__force u32)daddr;
+ hash[2] = ((__force u16)sport << 16) + (__force u16)dport;
+ hash[3] = net_secret[15];
+
+ md5_transform(hash, net_secret);
+
+ return seq_scale(hash[0]);
+}
+
+u32 secure_ipv4_port_ephemeral(__be32 saddr, __be32 daddr, __be16 dport)
+{
+ u32 hash[MD5_DIGEST_WORDS];
+
+ hash[0] = (__force u32)saddr;
+ hash[1] = (__force u32)daddr;
+ hash[2] = (__force u32)dport ^ net_secret[14];
+ hash[3] = net_secret[15];
+
+ md5_transform(hash, net_secret);
+
+ return hash[0];
+}
+EXPORT_SYMBOL_GPL(secure_ipv4_port_ephemeral);
+#endif
+
+#if defined(CONFIG_IP_DCCP) || defined(CONFIG_IP_DCCP_MODULE)
+u64 secure_dccp_sequence_number(__be32 saddr, __be32 daddr,
+ __be16 sport, __be16 dport)
+{
+ u32 hash[MD5_DIGEST_WORDS];
+ u64 seq;
+
+ hash[0] = (__force u32)saddr;
+ hash[1] = (__force u32)daddr;
+ hash[2] = ((__force u16)sport << 16) + (__force u16)dport;
+ hash[3] = net_secret[15];
+
+ md5_transform(hash, net_secret);
+
+ seq = hash[0] | (((u64)hash[1]) << 32);
+ seq += ktime_to_ns(ktime_get_real());
+ seq &= (1ull << 48) - 1;
+
+ return seq;
+}
+EXPORT_SYMBOL(secure_dccp_sequence_number);
+
+#if defined(CONFIG_IPV6) || defined(CONFIG_IPV6_MODULE)
+u64 secure_dccpv6_sequence_number(__be32 *saddr, __be32 *daddr,
+ __be16 sport, __be16 dport)
+{
+ u32 secret[MD5_MESSAGE_BYTES / 4];
+ u32 hash[MD5_DIGEST_WORDS];
+ u64 seq;
+ u32 i;
+
+ memcpy(hash, saddr, 16);
+ for (i = 0; i < 4; i++)
+ secret[i] = net_secret[i] + daddr[i];
+ secret[4] = net_secret[4] +
+ (((__force u16)sport << 16) + (__force u16)dport);
+ for (i = 5; i < MD5_MESSAGE_BYTES / 4; i++)
+ secret[i] = net_secret[i];
+
+ md5_transform(hash, secret);
+
+ seq = hash[0] | (((u64)hash[1]) << 32);
+ seq += ktime_to_ns(ktime_get_real());
+ seq &= (1ull << 48) - 1;
+
+ return seq;
+}
+EXPORT_SYMBOL(secure_dccpv6_sequence_number);
+#endif
+#endif