Message-Id: <201104182124.18866.glenn@wurster.ca>
Date:	Mon, 18 Apr 2011 21:24:17 -0400
From:	Glenn Wurster <glenn@...ster.ca>
To:	"David S. Miller" <davem@...emloft.net>,
	Alexey Kuznetsov <kuznet@....inr.ac.ru>,
	"Pekka Savola (ipv6)" <pekkas@...core.fi>,
	James Morris <jmorris@...ei.org>,
	Hideaki YOSHIFUJI <yoshfuji@...ux-ipv6.org>,
	Patrick McHardy <kaber@...sh.net>,
	Stephen Hemminger <shemminger@...tta.com>,
	Eric Dumazet <eric.dumazet@...il.com>,
	Herbert Xu <herbert@...dor.apana.org.au>,
	netdev@...r.kernel.org
Cc:	linux-kernel@...r.kernel.org, dbarrera@....carleton.ca
Subject: [PATCH 2.6.36 1/1] IPv6: Create temp address based on advertised network prefix

As discussed ;Login: Volume 36, number 1, create a temporary address
by hashing a random value along with the advertised network
prefix.  This results on the temporary address changing whenever
the network prefix changes (i.e., the host changes networks), or
whenever the random value (which can be set by a user-space
application with sufficient privilege) changes.

Signed-off-by: Glenn Wurster <gwurster@....carleton.ca>
---
 Documentation/networking/ip-sysctl.txt |   20 ++++-
 include/linux/ipv6.h                   |    4 +
 include/net/if_inet6.h                 |    3 +
 net/ipv6/Kconfig                       |   22 +++++
 net/ipv6/addrconf.c                    |  159 
+++++++++++++++++++++++++-------
 5 files changed, 175 insertions(+), 33 deletions(-)

diff --git a/Documentation/networking/ip-sysctl.txt 
b/Documentation/networking/ip-sysctl.txt
index f350c69..b366c28 100644
--- a/Documentation/networking/ip-sysctl.txt
+++ b/Documentation/networking/ip-sysctl.txt
@@ -1128,11 +1128,18 @@ router_solicitations - INTEGER
 
 use_tempaddr - INTEGER
 	Preference for Privacy Extensions (RFC3041).
+    Bits 0 and 1:
 	  <= 0 : disable Privacy Extensions
 	  == 1 : enable Privacy Extensions, but prefer public
 	         addresses over temporary addresses.
-	  >  1 : enable Privacy Extensions and prefer temporary
+	  >= 2 : enable Privacy Extensions and prefer temporary
 	         addresses over public addresses.
+    Bit 2:
+	  == 0 : Use RFC3041 random algorithm for generating
+             temporary addresses.
+	  == 1 : Use the output of a hash based on the network prefix
+	         and random number from temp_random.
+
 	Default:  0 (for most devices)
 		 -1 (for point-to-point devices and loopback devices)
 
@@ -1144,6 +1151,17 @@ temp_prefered_lft - INTEGER
 	Preferred lifetime (in seconds) for temporary addresses.
 	Default: 86400 (1 day)
 
+temp_random - INTEGER[4]
+    Random number used as input to the hash function when
+	generating temporary addresses also based on the network
+    prefix.
+	 == 0 : Generate a new random value when a temporary address
+	        is created.  This random value replaces the 0 in
+			temp_random	
+      > 0 : A random number used as input to the hash
+
+	Default:  0
+
 max_desync_factor - INTEGER
 	Maximum value for DESYNC_FACTOR, which is a random value
 	that ensures that clients don't synchronize with each
diff --git a/include/linux/ipv6.h b/include/linux/ipv6.h
index e62683b..b9bd404 100644
--- a/include/linux/ipv6.h
+++ b/include/linux/ipv6.h
@@ -172,6 +172,9 @@ struct ipv6_devconf {
 	__s32		disable_ipv6;
 	__s32		accept_dad;
 	__s32		force_tllao;
+#ifdef CONFIG_IPV6_PRIVACY_HASH
+	__u32		temp_random[4];
+#endif
 	void		*sysctl;
 };
 
@@ -213,6 +216,7 @@ enum {
 	DEVCONF_DISABLE_IPV6,
 	DEVCONF_ACCEPT_DAD,
 	DEVCONF_FORCE_TLLAO,
+	DEVCONF_TEMP_RANDOM,
 	DEVCONF_MAX
 };
 
diff --git a/include/net/if_inet6.h b/include/net/if_inet6.h
index f95ff8d..99428bf 100644
--- a/include/net/if_inet6.h
+++ b/include/net/if_inet6.h
@@ -183,6 +183,9 @@ struct inet6_dev {
 
 #ifdef CONFIG_IPV6_PRIVACY
 	u8			rndid[8];
+#ifdef CONFIG_IPV6_PRIVACY_HASH
+	__u32       rndid_inc;
+#endif
 	struct timer_list	regen_timer;
 	struct list_head	tempaddr_list;
 #endif
diff --git a/net/ipv6/Kconfig b/net/ipv6/Kconfig
index 36d7437..c0bc79a 100644
--- a/net/ipv6/Kconfig
+++ b/net/ipv6/Kconfig
@@ -39,6 +39,28 @@ config IPV6_PRIVACY
 
 	  See <file:Documentation/networking/ip-sysctl.txt> for details.
 
+if IPV6_PRIVACY
+
+config IPV6_PRIVACY_HASH
+	bool "IPv6: Privacy Extension Hash Support"
+	select CRYPTO
+	select CRYPTO_SHA256
+	---help---
+	  Generate the pseudo-random global-scope unicast address(es) based on
+	  the output of hashing together the broadcast prefix with a random
+	  value.  The algorithm is discussed in Volume 36, Number 1 of the USENIX
+	  ;Login: publication.
+
+	  To use hash-based temorary addresses, do
+
+	         echo 6 >/proc/sys/net/ipv6/conf/all/use_tempaddr
+
+	  To modify the input to the hash, do
+
+	         echo <random> >/proc/sys/net/ipv6/conf/all/temp_random
+
+endif # if IPV6_PRIVACY
+
 config IPV6_ROUTER_PREF
 	bool "IPv6: Router Preference (RFC 4191) support"
 	---help---
diff --git a/net/ipv6/addrconf.c b/net/ipv6/addrconf.c
index 89bcb62..4a2eaca 100644
--- a/net/ipv6/addrconf.c
+++ b/net/ipv6/addrconf.c
@@ -118,6 +118,7 @@ static inline void addrconf_sysctl_unregister(struct 
inet6_dev *idev)
 #endif
 
 #ifdef CONFIG_IPV6_PRIVACY
+static int __ipv6_is_invalid_rndid(const __u8 * rndid);
 static int __ipv6_regen_rndid(struct inet6_dev *idev);
 static int __ipv6_try_regen_rndid(struct inet6_dev *idev, struct in6_addr 
*tmpaddr);
 static void ipv6_regen_rndid(unsigned long data);
@@ -177,6 +178,9 @@ static struct ipv6_devconf ipv6_devconf __read_mostly = {
 	.temp_prefered_lft	= TEMP_PREFERRED_LIFETIME,
 	.regen_max_retry	= REGEN_MAX_RETRY,
 	.max_desync_factor	= MAX_DESYNC_FACTOR,
+#ifdef CONFIG_IPV6_PRIVACY_HASH
+	.temp_random		= { 0, 0, 0, 0 },
+#endif
 #endif
 	.max_addresses		= IPV6_MAX_ADDRESSES,
 	.accept_ra_defrtr	= 1,
@@ -211,6 +215,9 @@ static struct ipv6_devconf ipv6_devconf_dflt __read_mostly 
= {
 	.temp_prefered_lft	= TEMP_PREFERRED_LIFETIME,
 	.regen_max_retry	= REGEN_MAX_RETRY,
 	.max_desync_factor	= MAX_DESYNC_FACTOR,
+#ifdef CONFIG_IPV6_PRIVACY_HASH
+	.temp_random		= { 0, 0, 0, 0 },
+#endif
 #endif
 	.max_addresses		= IPV6_MAX_ADDRESSES,
 	.accept_ra_defrtr	= 1,
@@ -849,6 +856,7 @@ static int ipv6_create_tempaddr(struct inet6_ifaddr *ifp, 
struct inet6_ifaddr *i
 		memcpy(&addr.s6_addr[8], &ift->addr.s6_addr[8], 8);
 		spin_unlock_bh(&ift->lock);
 		tmpaddr = &addr;
+		ift = NULL;
 	} else {
 		tmpaddr = NULL;
 	}
@@ -875,17 +883,71 @@ retry:
 	}
 	in6_ifa_hold(ifp);
 	memcpy(addr.s6_addr, ifp->addr.s6_addr, 8);
-	if (__ipv6_try_regen_rndid(idev, tmpaddr) < 0) {
-		spin_unlock_bh(&ifp->lock);
-		write_unlock(&idev->lock);
-		printk(KERN_WARNING
-			"ipv6_create_tempaddr(): regeneration of randomized 
interface id failed.\n");
-		in6_ifa_put(ifp);
-		in6_dev_put(idev);
-		ret = -1;
-		goto out;
+#ifdef CONFIG_IPV6_PRIVACY_HASH
+	while (idev->cnf.use_tempaddr > 4) {
+		char hash[32];
+		__u32 temp_random[4];
+		int i;
+
+		struct hash_desc desc = { .tfm = NULL, .flags = 0 };
+		struct scatterlist sg;
+
+		BUG_ON (sizeof(temp_random) != sizeof(idev->cnf.temp_random));
+
+		for (i = 0; unlikely(idev->cnf.temp_random[i] == 0) && i < 4; i++);
+		if (unlikely(i == 4))
+			get_random_bytes(idev->cnf.temp_random, sizeof(idev-
>cnf.temp_random));
+
+		desc.tfm = crypto_alloc_hash ("sha256", 0, CRYPTO_ALG_ASYNC);
+		if (IS_ERR(desc.tfm)) {
+			idev->cnf.use_tempaddr &= 0x03;
+			printk (KERN_WARNING
+					"ipv6_create_tempaddr(): Hash unavailable, 
reverting use_tempaddr to %d.\n",
+					idev->cnf.use_tempaddr);
+			break;
+		}
+
+		BUG_ON (crypto_hash_digestsize(desc.tfm) > sizeof(hash));
+		BUG_ON (sizeof(idev->rndid) < 8);
+
+		crypto_hash_init (&desc);
+
+		sg_init_one (&sg, (u8 *)addr.s6_addr, 8);
+		crypto_hash_update (&desc, &sg, 8);
+
+		memcpy (temp_random, idev->cnf.temp_random, sizeof(temp_random));
+		temp_random[3] += idev->rndid_inc;
+		sg_init_one (&sg, (u8 *)temp_random, sizeof(temp_random));
+		crypto_hash_update (&desc, &sg, sizeof(temp_random));
+
+		crypto_hash_final (&desc, hash);
+		crypto_free_hash (desc.tfm);
+
+		memcpy (&addr.s6_addr[8], hash, 8);
+		if (__ipv6_is_invalid_rndid(&addr.s6_addr[8])) {
+			idev->rndid_inc++;
+			continue;
+		}
+
+		ift = ipv6_get_ifaddr (dev_net(idev->dev), &addr, idev->dev, 0);
+		break;
+	}
+#else
+	idev->cnf.use_tempaddr &= 0x03;
+#endif
+	if (idev->cnf.use_tempaddr < 4) {
+		if (__ipv6_try_regen_rndid(idev, tmpaddr) < 0) {
+			spin_unlock_bh(&ifp->lock);
+			write_unlock(&idev->lock);
+			printk(KERN_WARNING
+				   "ipv6_create_tempaddr(): regeneration of randomized 
interface id failed.\n");
+			in6_ifa_put(ifp);
+			in6_dev_put(idev);
+			ret = -1;
+			goto out;
+		}
+		memcpy(&addr.s6_addr[8], idev->rndid, 8);
 	}
-	memcpy(&addr.s6_addr[8], idev->rndid, 8);
 	age = (jiffies - ifp->tstamp) / HZ;
 	tmp_valid_lft = min_t(__u32,
 			      ifp->valid_lft,
@@ -922,11 +984,11 @@ retry:
 	if (ifp->flags & IFA_F_OPTIMISTIC)
 		addr_flags |= IFA_F_OPTIMISTIC;
 
-	ift = !max_addresses ||
-	      ipv6_count_addresses(idev) < max_addresses ?
-		ipv6_add_addr(idev, &addr, tmp_plen,
-			      ipv6_addr_type(&addr)&IPV6_ADDR_SCOPE_MASK,
-			      addr_flags) : NULL;
+	if (!ift && (!max_addresses || ipv6_count_addresses(idev) < 
max_addresses)) {
+		ift = ipv6_add_addr(idev, &addr, tmp_plen,
+		                    ipv6_addr_type(&addr)&IPV6_ADDR_SCOPE_MASK,
+		                    addr_flags);
+	}
 	if (!ift || IS_ERR(ift)) {
 		in6_ifa_put(ifp);
 		in6_dev_put(idev);
@@ -943,9 +1005,11 @@ retry:
 	ift->prefered_lft = tmp_prefered_lft;
 	ift->cstamp = tmp_cstamp;
 	ift->tstamp = tmp_tstamp;
+	ift->regen_count = 0;
 	spin_unlock_bh(&ift->lock);
 
-	addrconf_dad_start(ift, 0);
+	if (ift->flags & IFA_F_TENTATIVE)
+		addrconf_dad_start(ift, 0);
 	in6_ifa_put(ift);
 	in6_dev_put(idev);
 out:
@@ -1090,7 +1154,7 @@ static int ipv6_get_saddr_eval(struct net *net,
 		 */
 		int preftmp = dst->prefs & (IPV6_PREFER_SRC_PUBLIC|
IPV6_PREFER_SRC_TMP) ?
 				!!(dst->prefs & IPV6_PREFER_SRC_TMP) :
-				score->ifa->idev->cnf.use_tempaddr >= 2;
+				!!(score->ifa->idev->cnf.use_tempaddr & 2);
 		ret = (!(score->ifa->flags & IFA_F_TEMPORARY)) ^ preftmp;
 		break;
 	    }
@@ -1398,6 +1462,9 @@ static void addrconf_dad_stop(struct inet6_ifaddr *ifp, 
int dad_failed)
 		if (ifpub) {
 			in6_ifa_hold(ifpub);
 			spin_unlock_bh(&ifp->lock);
+#ifdef CONFIG_IPV6_PRIVACY_HASH
+			ifp->idev->rndid_inc++;
+#endif
 			ipv6_create_tempaddr(ifpub, ifp);
 			in6_ifa_put(ifpub);
 		} else {
@@ -1605,13 +1672,8 @@ static int ipv6_inherit_eui64(u8 *eui, struct inet6_dev 
*idev)
 }
 
 #ifdef CONFIG_IPV6_PRIVACY
-/* (re)generation of randomized interface identifier (RFC 3041 3.2, 3.5) */
-static int __ipv6_regen_rndid(struct inet6_dev *idev)
+static int __ipv6_is_invalid_rndid(const __u8 * rndid)
 {
-regen:
-	get_random_bytes(idev->rndid, sizeof(idev->rndid));
-	idev->rndid[0] &= ~0x02;
-
 	/*
 	 * <draft-ietf-ipngwg-temp-addresses-v2-00.txt>:
 	 * check if generated address is not inappropriate
@@ -1623,15 +1685,35 @@ regen:
 	 *  - value 0
 	 *  - XXX: already assigned to an address on the device
 	 */
-	if (idev->rndid[0] == 0xfd &&
-	    (idev->rndid[1]&idev->rndid[2]&idev->rndid[3]&idev->rndid[4]&idev-
>rndid[5]&idev->rndid[6]) == 0xff &&
-	    (idev->rndid[7]&0x80))
-		goto regen;
-	if ((idev->rndid[0]|idev->rndid[1]) == 0) {
-		if (idev->rndid[2] == 0x5e && idev->rndid[3] == 0xfe)
-			goto regen;
-		if ((idev->rndid[2]|idev->rndid[3]|idev->rndid[4]|idev->rndid[5]|
idev->rndid[6]|idev->rndid[7]) == 0x00)
-			goto regen;
+
+	if (rndid[0] == 0xfd &&
+	    (rndid[1]&rndid[2]&rndid[3]&rndid[4]&rndid[5]&rndid[6]) == 0xff &&
+	    (rndid[7]&0x80))
+		return -1;
+	if ((rndid[0]|rndid[1]) == 0) {
+		if (rndid[2] == 0x5e && rndid[3] == 0xfe)
+			return -1;
+		if ((rndid[2]|rndid[3]|rndid[4]|rndid[5]|rndid[6]|rndid[7]) == 
0x00)
+			return -1;
+	}
+	return 0;
+}
+
+/* (re)generation of randomized interface identifier (RFC 3041 3.2, 3.5) */
+static int __ipv6_regen_rndid(struct inet6_dev *idev)
+{
+#ifdef CONFIG_IPV6_PRIVACY_HASH
+	if (idev->cnf.use_tempaddr > 4) {
+		get_random_bytes(idev->cnf.temp_random, sizeof(idev-
>cnf.temp_random));
+	}
+#else
+	idev->cnf.use_tempaddr &= 0x03;
+#endif
+	if (idev->cnf.use_tempaddr < 4) {
+		do {
+			get_random_bytes(idev->rndid, sizeof(idev->rndid));
+			idev->rndid[0] &= ~0x02;
+		} while (__ipv6_is_invalid_rndid(idev->rndid));
 	}
 
 	return 0;
@@ -1903,6 +1985,10 @@ ok:
 			int max_addresses = in6_dev->cnf.max_addresses;
 			u32 addr_flags = 0;
 
+#ifdef CONFIG_IPV6_PRIVACY_HASH
+			in6_dev->rndid_inc = 0;
+#endif
+
 #ifdef CONFIG_IPV6_OPTIMISTIC_DAD
 			if (in6_dev->cnf.optimistic_dad &&
 			    !net->ipv6.devconf_all->forwarding)
@@ -4454,6 +4540,15 @@ static struct addrconf_sysctl_table
 			.mode           = 0644,
 			.proc_handler   = proc_dointvec
 		},
+#ifdef CONFIG_IPV6_PRIVACY_HASH
+		{
+			.procname	= "temp_random",
+			.data		= &ipv6_devconf.temp_random,
+			.maxlen		= sizeof(ipv6_devconf.temp_random),
+			.mode		= 0640,
+			.proc_handler	= proc_dointvec,
+		},
+#endif
 		{
 			/* sentinel */
 		}
-- 
1.7.2.3

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