From: Manfred Spraul <manfred@colorfullife.com>
Below are fixes for secret key loading of the secure sequence number
generator.
The tcp sequence number generator needs a random seed that is reset every
few minutes. Since the sequence numbers should be constantly increasing,
for each rekey 2^24 is added to the sequence number. The actual use of the
sequence number generator is lockless, synchronization is achieved by
having two copies of the control structure.
The attached patch:
- fixes a race in rekey_seq_generator(): schedule_work doesn't provide
synchronization, keyptr->rekey_time must be checked again under a
spinlock
- removes the _bh from the ip_lock spinlock: it now always runs from
process context, no need to disable bottom-halfs.
- replaces do_gettimeofday with get_seconds(): get_seconds is faster and
usec resolution is not required.
- replaces tmpdata with a simple char array - saves some stack space, no
need to create an unused copy of the whole control structure on the
stack.
- Adds a late_initcall for the first initialization after boot.
init_call would be too early, I've checked that the late_initcall runs
before net/ipv4/ipconfig.c, i.e. the BOOTP/DHCP autoconfiguration.
Signed-Off-By: Manfred Spraul <manfred@colorfullife.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
---
25-akpm/drivers/char/random.c | 37 ++++++++++++++++++++++---------------
1 files changed, 22 insertions(+), 15 deletions(-)
diff -puN drivers/char/random.c~fix-secure-tcp-sequence-number-generator drivers/char/random.c
--- 25/drivers/char/random.c~fix-secure-tcp-sequence-number-generator 2004-09-26 17:18:36.526105640 -0700
+++ 25-akpm/drivers/char/random.c 2004-09-26 17:18:36.531104880 -0700
@@ -2215,28 +2215,28 @@ static struct keydata {
__u32 secret[12];
} ____cacheline_aligned ip_keydata[2];
-static spinlock_t ip_lock = SPIN_LOCK_UNLOCKED;
static unsigned int ip_cnt;
static void rekey_seq_generator(void *private_)
{
- struct keydata *keyptr, tmp;
- struct timeval tv;
+static spinlock_t ip_lock = SPIN_LOCK_UNLOCKED;
+ struct keydata *keyptr;
+ char newkey[sizeof(keyptr->secret)];
- do_gettimeofday(&tv);
- get_random_bytes(tmp.secret, sizeof(tmp.secret));
+ get_random_bytes(newkey, sizeof(newkey));
- spin_lock_bh(&ip_lock);
+ spin_lock(&ip_lock);
keyptr = &ip_keydata[ip_cnt&1];
+ if ((get_seconds() - keyptr->rekey_time) > REKEY_INTERVAL) {
- keyptr = &ip_keydata[1^(ip_cnt&1)];
- keyptr->rekey_time = tv.tv_sec;
- memcpy(keyptr->secret, tmp.secret, sizeof(keyptr->secret));
- keyptr->count = (ip_cnt&COUNT_MASK)<<HASH_BITS;
- mb();
- ip_cnt++;
-
- spin_unlock_bh(&ip_lock);
+ keyptr = &ip_keydata[1^(ip_cnt&1)];
+ keyptr->rekey_time = get_seconds();
+ memcpy(keyptr->secret, newkey, sizeof(keyptr->secret));
+ keyptr->count = (ip_cnt&COUNT_MASK)<<HASH_BITS;
+ mb();
+ ip_cnt++;
+ }
+ spin_unlock(&ip_lock);
}
static DECLARE_WORK(rekey_work, rekey_seq_generator, NULL);
@@ -2246,13 +2246,20 @@ static inline struct keydata *check_and_
struct keydata *keyptr = &ip_keydata[ip_cnt&1];
rmb();
- if (!keyptr->rekey_time || (time - keyptr->rekey_time) > REKEY_INTERVAL) {
+ if ((time - keyptr->rekey_time) > REKEY_INTERVAL) {
schedule_work(&rekey_work);
}
return keyptr;
}
+static __init int seqgen_init(void)
+{
+ rekey_seq_generator(NULL);
+ return 0;
+}
+late_initcall(seqgen_init);
+
#if defined(CONFIG_IPV6) || defined(CONFIG_IPV6_MODULE)
__u32 secure_tcpv6_sequence_number(__u32 *saddr, __u32 *daddr,
__u16 sport, __u16 dport)
_