CVE-2011-3188 (C, published 2012-05-24T23:55Z)
Description: value: The (1) IPv4 and (2) IPv6 implementations in the Linux kernel before 3.1 use a modified MD4 algorithm to generate sequence numbers and Fragment Identification values, which makes it easier for remote attackers to cause a denial of service (disrupted networking) or hijack network sessions by predicting these values and sending crafted packets.
Severity: MEDIUM (CVSS v3 base score: 9.1)
Weakness: NVD-CWE-Other \u2014 Other
NVD is only using a subset of CWE for mapping instead of the entire CWE, and the weakness type is not covered by that subset.
Repository: https://github.com/torvalds/linux
Files changed:
drivers/char/random.c
include/linux/random.h
include/net/secure_seq.h
net/core/Makefile
net/core/secure_seq.c
net/dccp/ipv4.c
net/dccp/ipv6.c
net/ipv4/inet_hashtables.c
net/ipv4/inetpeer.c
net/ipv4/netfilter/nf_nat_proto_common.c
net/ipv4/route.c
net/ipv4/tcp_ipv4.c
net/ipv6/inet6_hashtables.c
net/ipv6/tcp_ipv6.c
Commit message: 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>


Vulnerable code:
/********************************************************************
 *
 * Random functions for networking
 *
 ********************************************************************/

/*
 * TCP initial sequence number picking.  This uses the random number
 * generator to pick an initial secret value.  This value is hashed
 * along with the TCP endpoint information to provide a unique
 * starting point for each pair of TCP endpoints.  This defeats
 * attacks which rely on guessing the initial TCP sequence number.
 * This algorithm was suggested by Steve Bellovin.
 *
 * Using a very strong hash was taking an appreciable amount of the total
 * TCP connection establishment time, so this is a weaker hash,
 * compensated for by changing the secret periodically.
 */

/* F, G and H are basic MD4 functions: selection, majority, parity */
#define F(x, y, z) ((z) ^ ((x) & ((y) ^ (z))))
#define G(x, y, z) (((x) & (y)) + (((x) ^ (y)) & (z)))
#define H(x, y, z) ((x) ^ (y) ^ (z))

/*
 * The generic round function.  The application is so specific that
 * we don't bother protecting all the arguments with parens, as is generally
 * good macro practice, in favor of extra legibility.
 * Rotation is separate from addition to prevent recomputation
 */
#define ROUND(f, a, b, c, d, x, s)	\
	(a += f(b, c, d) + x, a = (a << s) | (a >> (32 - s)))
#define K1 0
#define K2 013240474631UL
#define K3 015666365641UL

#if defined(CONFIG_IPV6) || defined(CONFIG_IPV6_MODULE)

static __u32 twothirdsMD4Transform(__u32 const buf[4], __u32 const in[12])
{
	__u32 a = buf[0], b = buf[1], c = buf[2], d = buf[3];

	/* Round 1 */
	ROUND(F, a, b, c, d, in[ 0] + K1,  3);
	ROUND(F, d, a, b, c, in[ 1] + K1,  7);
	ROUND(F, c, d, a, b, in[ 2] + K1, 11);
	ROUND(F, b, c, d, a, in[ 3] + K1, 19);
	ROUND(F, a, b, c, d, in[ 4] + K1,  3);
	ROUND(F, d, a, b, c, in[ 5] + K1,  7);
	ROUND(F, c, d, a, b, in[ 6] + K1, 11);
	ROUND(F, b, c, d, a, in[ 7] + K1, 19);
	ROUND(F, a, b, c, d, in[ 8] + K1,  3);
	ROUND(F, d, a, b, c, in[ 9] + K1,  7);
	ROUND(F, c, d, a, b, in[10] + K1, 11);
	ROUND(F, b, c, d, a, in[11] + K1, 19);

	/* Round 2 */
	ROUND(G, a, b, c, d, in[ 1] + K2,  3);
	ROUND(G, d, a, b, c, in[ 3] + K2,  5);
	ROUND(G, c, d, a, b, in[ 5] + K2,  9);
	ROUND(G, b, c, d, a, in[ 7] + K2, 13);
	ROUND(G, a, b, c, d, in[ 9] + K2,  3);
	ROUND(G, d, a, b, c, in[11] + K2,  5);
	ROUND(G, c, d, a, b, in[ 0] + K2,  9);
	ROUND(G, b, c, d, a, in[ 2] + K2, 13);
	ROUND(G, a, b, c, d, in[ 4] + K2,  3);
	ROUND(G, d, a, b, c, in[ 6] + K2,  5);
	ROUND(G, c, d, a, b, in[ 8] + K2,  9);
	ROUND(G, b, c, d, a, in[10] + K2, 13);

	/* Round 3 */
	ROUND(H, a, b, c, d, in[ 3] + K3,  3);
	ROUND(H, d, a, b, c, in[ 7] + K3,  9);
	ROUND(H, c, d, a, b, in[11] + K3, 11);
	ROUND(H, b, c, d, a, in[ 2] + K3, 15);
	ROUND(H, a, b, c, d, in[ 6] + K3,  3);
	ROUND(H, d, a, b, c, in[10] + K3,  9);
	ROUND(H, c, d, a, b, in[ 1] + K3, 11);
	ROUND(H, b, c, d, a, in[ 5] + K3, 15);
	ROUND(H, a, b, c, d, in[ 9] + K3,  3);
	ROUND(H, d, a, b, c, in[ 0] + K3,  9);
	ROUND(H, c, d, a, b, in[ 4] + K3, 11);
	ROUND(H, b, c, d, a, in[ 8] + K3, 15);

	return buf[1] + b; /* "most hashed" word */
	/* Alternative: return sum of all words? */
}
#endif

#undef ROUND
#undef F
#undef G
#undef H
#undef K1
#undef K2
#undef K3

/* This should not be decreased so low that ISNs wrap too fast. */
#define REKEY_INTERVAL (300 * HZ)
/*
 * Bit layout of the tcp sequence numbers (before adding current time):
 * bit 24-31: increased after every key exchange
 * bit 0-23: hash(source,dest)
 *
 * The implementation is similar to the algorithm described
 * in the Appendix of RFC 1185, except that
 * - it uses a 1 MHz clock instead of a 250 kHz clock
 * - it performs a rekey every 5 minutes, which is equivalent
 * 	to a (source,dest) tulple dependent forward jump of the
 * 	clock by 0..2^(HASH_BITS+1)
 *
 * Thus the average ISN wraparound time is 68 minutes instead of
 * 4.55 hours.
 *
 * SMP cleanup and lock avoidance with poor man's RCU.
 * 			Manfred Spraul <manfred@colorfullife.com>
 *
 */
#define COUNT_BITS 8
#define COUNT_MASK ((1 << COUNT_BITS) - 1)
#define HASH_BITS 24
#define HASH_MASK ((1 << HASH_BITS) - 1)
static struct keydata {
	__u32 count; /* already shifted to the final position */
	__u32 secret[12];
} ____cacheline_aligned ip_keydata[2];

static unsigned int ip_cnt;

static void rekey_seq_generator(struct work_struct *work);

static DECLARE_DELAYED_WORK(rekey_work, rekey_seq_generator);

/*
 * Lock avoidance:
 * The ISN generation runs lockless - it's just a hash over random data.
 * State changes happen every 5 minutes when the random key is replaced.
 * Synchronization is performed by having two copies of the hash function
 * state and rekey_seq_generator always updates the inactive copy.
 * The copy is then activated by updating ip_cnt.
 * The implementation breaks down if someone blocks the thread
 * that processes SYN requests for more than 5 minutes. Should never
 * happen, and even if that happens only a not perfectly compliant
 * ISN is generated, nothing fatal.
 */
static void rekey_seq_generator(struct work_struct *work)
	struct keydata *keyptr = &ip_keydata[1 ^ (ip_cnt & 1)];

	get_random_bytes(keyptr->secret, sizeof(keyptr->secret));
	keyptr->count = (ip_cnt & COUNT_MASK) << HASH_BITS;
	smp_wmb();
	ip_cnt++;
	schedule_delayed_work(&rekey_work,
			      round_jiffies_relative(REKEY_INTERVAL));
}

static inline struct keydata *get_keyptr(void)
{
	struct keydata *keyptr = &ip_keydata[ip_cnt & 1];

	smp_rmb();

	return keyptr;
}

static __init int seqgen_init(void)
{
	rekey_seq_generator(NULL);
late_initcall(seqgen_init);

#if defined(CONFIG_IPV6) || defined(CONFIG_IPV6_MODULE)
__u32 secure_tcpv6_sequence_number(__be32 *saddr, __be32 *daddr,
				   __be16 sport, __be16 dport)
{
	__u32 seq;
	__u32 hash[12];
	struct keydata *keyptr = get_keyptr();

	/* The procedure is the same as for IPv4, but addresses are longer.
	 * Thus we must use twothirdsMD4Transform.
	 */

	memcpy(hash, saddr, 16);
	hash[4] = ((__force u16)sport << 16) + (__force u16)dport;
	memcpy(&hash[5], keyptr->secret, sizeof(__u32) * 7);

	seq = twothirdsMD4Transform((const __u32 *)daddr, hash) & HASH_MASK;
	seq += keyptr->count;

	seq += ktime_to_ns(ktime_get_real());

	return seq;
}
EXPORT_SYMBOL(secure_tcpv6_sequence_number);
#endif

/*  The code below is shamelessly stolen from secure_tcp_sequence_number().
 *  All blames to Andrey V. Savochkin <saw@msu.ru>.
 */
__u32 secure_ip_id(__be32 daddr)
{
	struct keydata *keyptr;
	__u32 hash[4];

	keyptr = get_keyptr();

	/*
	 *  Pick a unique starting offset for each IP destination.
	 *  The dest ip address is placed in the starting vector,
	 *  which is then hashed with random data.
	 */
	hash[0] = (__force __u32)daddr;
	hash[1] = keyptr->secret[9];
	hash[2] = keyptr->secret[10];
	hash[3] = keyptr->secret[11];

	return half_md4_transform(hash, keyptr->secret);
}

__u32 secure_ipv6_id(const __be32 daddr[4])
{
	const struct keydata *keyptr;
	__u32 hash[4];

	keyptr = get_keyptr();

	hash[0] = (__force __u32)daddr[0];
	hash[1] = (__force __u32)daddr[1];
	hash[2] = (__force __u32)daddr[2];
	hash[3] = (__force __u32)daddr[3];

	return half_md4_transform(hash, keyptr->secret);
}

#ifdef CONFIG_INET

__u32 secure_tcp_sequence_number(__be32 saddr, __be32 daddr,
				 __be16 sport, __be16 dport)
{
	__u32 seq;
	__u32 hash[4];
	struct keydata *keyptr = get_keyptr();

	/*
	 *  Pick a unique starting offset for each TCP connection endpoints
	 *  (saddr, daddr, sport, dport).
	 *  Note that the words are placed into the starting vector, which is
	 *  then mixed with a partial MD4 over random data.
	 */
	hash[0] = (__force u32)saddr;
	hash[1] = (__force u32)daddr;
	hash[2] = ((__force u16)sport << 16) + (__force u16)dport;
	hash[3] = keyptr->secret[11];

	seq = half_md4_transform(hash, keyptr->secret) & HASH_MASK;
	seq += keyptr->count;
	/*
	 *	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)
	 */
	seq += ktime_to_ns(ktime_get_real()) >> 6;

	return seq;
}

/* Generate secure starting point for ephemeral IPV4 transport port search */
u32 secure_ipv4_port_ephemeral(__be32 saddr, __be32 daddr, __be16 dport)
{
	struct keydata *keyptr = get_keyptr();
	u32 hash[4];

	/*
	 *  Pick a unique starting offset for each ephemeral port search
	 *  (saddr, daddr, dport) and 48bits of random data.
	 */
	hash[0] = (__force u32)saddr;
	hash[1] = (__force u32)daddr;
	hash[2] = (__force u32)dport ^ keyptr->secret[10];
	hash[3] = keyptr->secret[11];

	return half_md4_transform(hash, keyptr->secret);
}
EXPORT_SYMBOL_GPL(secure_ipv4_port_ephemeral);

#if defined(CONFIG_IPV6) || defined(CONFIG_IPV6_MODULE)
u32 secure_ipv6_port_ephemeral(const __be32 *saddr, const __be32 *daddr,
			       __be16 dport)
{
	struct keydata *keyptr = get_keyptr();
	u32 hash[12];

	memcpy(hash, saddr, 16);
	hash[4] = (__force u32)dport;
	memcpy(&hash[5], keyptr->secret, sizeof(__u32) * 7);

	return twothirdsMD4Transform((const __u32 *)daddr, hash);
}
#endif

#if defined(CONFIG_IP_DCCP) || defined(CONFIG_IP_DCCP_MODULE)
/* Similar to secure_tcp_sequence_number but generate a 48 bit value
 * bit's 32-47 increase every key exchange
 *       0-31  hash(source, dest)
 */
u64 secure_dccp_sequence_number(__be32 saddr, __be32 daddr,
				__be16 sport, __be16 dport)
{
	u64 seq;
	__u32 hash[4];
	struct keydata *keyptr = get_keyptr();

	hash[0] = (__force u32)saddr;
	hash[1] = (__force u32)daddr;
	hash[2] = ((__force u16)sport << 16) + (__force u16)dport;
	hash[3] = keyptr->secret[11];

	seq = half_md4_transform(hash, keyptr->secret);
	seq |= ((u64)keyptr->count) << (32 - HASH_BITS);

	seq += ktime_to_ns(ktime_get_real());
	seq &= (1ull << 48) - 1;

	return seq;
}
EXPORT_SYMBOL(secure_dccp_sequence_number);
#endif

#endif /* CONFIG_INET */

DEFINE_PER_CPU(__u32 [4], get_random_int_hash);
	struct keydata *keyptr;
	int ret;
	keyptr = get_keyptr();

	ret = half_md4_transform(hash, keyptr->secret);
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);

	 gen_stats.o gen_estimator.o net_namespace.o
static inline __u32 secure_dccpv6_sequence_number(__be32 *saddr, __be32 *daddr,
						  __be16 sport, __be16 dport   )
{
	return secure_tcpv6_sequence_number(saddr, daddr, sport, dport);
}

static inline __u32 dccp_v6_init_sequence(struct sk_buff *skb)

Fixed code:
static u32 random_int_secret[MD5_MESSAGE_BYTES / 4] ____cacheline_aligned;
static int __init random_int_secret_init(void)
	get_random_bytes(random_int_secret, sizeof(random_int_secret));
late_initcall(random_int_secret_init);
DEFINE_PER_CPU(__u32 [MD5_DIGEST_WORDS], get_random_int_hash);
	unsigned int ret;
	md5_transform(hash, random_int_secret);
	ret = hash[0];
#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 */
	 gen_stats.o gen_estimator.o net_namespace.o secure_seq.o
#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
#include <net/secure_seq.h>
#include <net/secure_seq.h>
static inline __u64 dccp_v6_init_sequence(struct sk_buff *skb)
#include <net/secure_seq.h>
#include <net/secure_seq.h>
#include <net/secure_seq.h>
#include <net/secure_seq.h>
#include <net/secure_seq.h>
#include <net/secure_seq.h>
#include <net/secure_seq.h>