diff options
| -rw-r--r-- | drivers/char/random.c | 68 |
1 files changed, 35 insertions, 33 deletions
diff --git a/drivers/char/random.c b/drivers/char/random.c index 4f6903cc695b..295e3f718b5c 100644 --- a/drivers/char/random.c +++ b/drivers/char/random.c @@ -2187,7 +2187,7 @@ static __u32 twothirdsMD4Transform (__u32 const buf[4], __u32 const in[12]) #undef K3 /* This should not be decreased so low that ISNs wrap too fast. */ -#define REKEY_INTERVAL 300 +#define REKEY_INTERVAL (300*HZ) /* * Bit layout of the tcp sequence numbers (before adding current time): * bit 24-31: increased after every key exchange @@ -2213,48 +2213,55 @@ static __u32 twothirdsMD4Transform (__u32 const buf[4], __u32 const in[12]) #define HASH_MASK ( (1<<HASH_BITS)-1 ) static struct keydata { - time_t rekey_time; __u32 count; // already shifted to the final position __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; - struct timeval tv; +static void rekey_seq_generator(void *private_); - do_gettimeofday(&tv); +static DECLARE_WORK(rekey_work, rekey_seq_generator, NULL); - spin_lock_bh(&ip_lock); - keyptr = &ip_keydata[ip_cnt&1]; +/* + * 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(void *private_) +{ + struct keydata *keyptr = &ip_keydata[1^(ip_cnt&1)]; - keyptr = &ip_keydata[1^(ip_cnt&1)]; - keyptr->rekey_time = tv.tv_sec; get_random_bytes(keyptr->secret, sizeof(keyptr->secret)); keyptr->count = (ip_cnt&COUNT_MASK)<<HASH_BITS; - mb(); + smp_wmb(); ip_cnt++; - - spin_unlock_bh(&ip_lock); + schedule_delayed_work(&rekey_work, REKEY_INTERVAL); } -static DECLARE_WORK(rekey_work, rekey_seq_generator, NULL); - -static inline struct keydata *check_and_rekey(time_t time) +static inline struct keydata *get_keyptr(void) { struct keydata *keyptr = &ip_keydata[ip_cnt&1]; - rmb(); - if (!keyptr->rekey_time || (time - keyptr->rekey_time) > REKEY_INTERVAL) { - schedule_work(&rekey_work); - } + smp_rmb(); 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) @@ -2262,14 +2269,12 @@ __u32 secure_tcpv6_sequence_number(__u32 *saddr, __u32 *daddr, struct timeval tv; __u32 seq; __u32 hash[12]; - struct keydata *keyptr; + struct keydata *keyptr = get_keyptr(); /* The procedure is the same as for IPv4, but addresses are longer. * Thus we must use twothirdsMD4Transform. */ - do_gettimeofday(&tv); /* We need the usecs below... */ - keyptr = check_and_rekey(tv.tv_sec); memcpy(hash, saddr, 16); hash[4]=(sport << 16) + dport; @@ -2277,6 +2282,8 @@ __u32 secure_tcpv6_sequence_number(__u32 *saddr, __u32 *daddr, seq = twothirdsMD4Transform(daddr, hash) & HASH_MASK; seq += keyptr->count; + + do_gettimeofday(&tv); seq += tv.tv_usec + tv.tv_sec*1000000; return seq; @@ -2290,13 +2297,7 @@ __u32 secure_tcp_sequence_number(__u32 saddr, __u32 daddr, struct timeval tv; __u32 seq; __u32 hash[4]; - struct keydata *keyptr; - - /* - * Pick a random secret every REKEY_INTERVAL seconds. - */ - do_gettimeofday(&tv); /* We need the usecs below... */ - keyptr = check_and_rekey(tv.tv_sec); + struct keydata *keyptr = get_keyptr(); /* * Pick a unique starting offset for each TCP connection endpoints @@ -2319,6 +2320,7 @@ __u32 secure_tcp_sequence_number(__u32 saddr, __u32 daddr, * That's funny, Linux has one built in! Use it! * (Networks are faster now - should this be increased?) */ + do_gettimeofday(&tv); seq += tv.tv_usec + tv.tv_sec*1000000; #if 0 printk("init_seq(%lx, %lx, %d, %d) = %d\n", @@ -2337,7 +2339,7 @@ __u32 secure_ip_id(__u32 daddr) struct keydata *keyptr; __u32 hash[4]; - keyptr = check_and_rekey(get_seconds()); + keyptr = get_keyptr(); /* * Pick a unique starting offset for each IP destination. |