diff options
Diffstat (limited to 'net/core/secure_seq.c')
| -rw-r--r-- | net/core/secure_seq.c | 200 |
1 files changed, 200 insertions, 0 deletions
diff --git a/net/core/secure_seq.c b/net/core/secure_seq.c new file mode 100644 index 000000000..6fd25279b --- /dev/null +++ b/net/core/secure_seq.c @@ -0,0 +1,200 @@ +/* + * Copyright (C) 2016 Jason A. Donenfeld <Jason@zx2c4.com>. All Rights Reserved. + */ + +#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 <linux/net.h> +#include <linux/siphash.h> +#include <net/secure_seq.h> + +#if IS_ENABLED(CONFIG_IPV6) || IS_ENABLED(CONFIG_INET) +#include <linux/in6.h> +#include <net/tcp.h> + +static siphash_key_t net_secret __read_mostly; +static siphash_key_t ts_secret __read_mostly; + +#define EPHEMERAL_PORT_SHUFFLE_PERIOD (10 * HZ) + +static __always_inline void net_secret_init(void) +{ + net_get_random_once(&net_secret, sizeof(net_secret)); +} + +static __always_inline void ts_secret_init(void) +{ + net_get_random_once(&ts_secret, sizeof(ts_secret)); +} +#endif + +#ifdef CONFIG_INET +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_get_real_ns() >> 6); +} +#endif + +#if IS_ENABLED(CONFIG_IPV6) +u32 secure_tcpv6_ts_off(const struct net *net, + const __be32 *saddr, const __be32 *daddr) +{ + const struct { + struct in6_addr saddr; + struct in6_addr daddr; + } __aligned(SIPHASH_ALIGNMENT) combined = { + .saddr = *(struct in6_addr *)saddr, + .daddr = *(struct in6_addr *)daddr, + }; + + if (net->ipv4.sysctl_tcp_timestamps != 1) + return 0; + + ts_secret_init(); + return siphash(&combined, offsetofend(typeof(combined), daddr), + &ts_secret); +} +EXPORT_SYMBOL(secure_tcpv6_ts_off); + +u32 secure_tcpv6_seq(const __be32 *saddr, const __be32 *daddr, + __be16 sport, __be16 dport) +{ + const struct { + struct in6_addr saddr; + struct in6_addr daddr; + __be16 sport; + __be16 dport; + } __aligned(SIPHASH_ALIGNMENT) combined = { + .saddr = *(struct in6_addr *)saddr, + .daddr = *(struct in6_addr *)daddr, + .sport = sport, + .dport = dport + }; + u32 hash; + + net_secret_init(); + hash = siphash(&combined, offsetofend(typeof(combined), dport), + &net_secret); + return seq_scale(hash); +} +EXPORT_SYMBOL(secure_tcpv6_seq); + +u64 secure_ipv6_port_ephemeral(const __be32 *saddr, const __be32 *daddr, + __be16 dport) +{ + const struct { + struct in6_addr saddr; + struct in6_addr daddr; + unsigned int timeseed; + __be16 dport; + } __aligned(SIPHASH_ALIGNMENT) combined = { + .saddr = *(struct in6_addr *)saddr, + .daddr = *(struct in6_addr *)daddr, + .timeseed = jiffies / EPHEMERAL_PORT_SHUFFLE_PERIOD, + .dport = dport, + }; + net_secret_init(); + return siphash(&combined, offsetofend(typeof(combined), dport), + &net_secret); +} +EXPORT_SYMBOL(secure_ipv6_port_ephemeral); +#endif + +#ifdef CONFIG_INET +u32 secure_tcp_ts_off(const struct net *net, __be32 saddr, __be32 daddr) +{ + if (net->ipv4.sysctl_tcp_timestamps != 1) + return 0; + + ts_secret_init(); + return siphash_2u32((__force u32)saddr, (__force u32)daddr, + &ts_secret); +} + +/* secure_tcp_seq_and_tsoff(a, b, 0, d) == secure_ipv4_port_ephemeral(a, b, d), + * but fortunately, `sport' cannot be 0 in any circumstances. If this changes, + * it would be easy enough to have the former function use siphash_4u32, passing + * the arguments as separate u32. + */ +u32 secure_tcp_seq(__be32 saddr, __be32 daddr, + __be16 sport, __be16 dport) +{ + u32 hash; + + net_secret_init(); + hash = siphash_3u32((__force u32)saddr, (__force u32)daddr, + (__force u32)sport << 16 | (__force u32)dport, + &net_secret); + return seq_scale(hash); +} +EXPORT_SYMBOL_GPL(secure_tcp_seq); + +u64 secure_ipv4_port_ephemeral(__be32 saddr, __be32 daddr, __be16 dport) +{ + net_secret_init(); + return siphash_4u32((__force u32)saddr, (__force u32)daddr, + (__force u16)dport, + jiffies / EPHEMERAL_PORT_SHUFFLE_PERIOD, + &net_secret); +} +EXPORT_SYMBOL_GPL(secure_ipv4_port_ephemeral); +#endif + +#if IS_ENABLED(CONFIG_IP_DCCP) +u64 secure_dccp_sequence_number(__be32 saddr, __be32 daddr, + __be16 sport, __be16 dport) +{ + u64 seq; + net_secret_init(); + seq = siphash_3u32((__force u32)saddr, (__force u32)daddr, + (__force u32)sport << 16 | (__force u32)dport, + &net_secret); + seq += ktime_get_real_ns(); + seq &= (1ull << 48) - 1; + return seq; +} +EXPORT_SYMBOL(secure_dccp_sequence_number); + +#if IS_ENABLED(CONFIG_IPV6) +u64 secure_dccpv6_sequence_number(__be32 *saddr, __be32 *daddr, + __be16 sport, __be16 dport) +{ + const struct { + struct in6_addr saddr; + struct in6_addr daddr; + __be16 sport; + __be16 dport; + } __aligned(SIPHASH_ALIGNMENT) combined = { + .saddr = *(struct in6_addr *)saddr, + .daddr = *(struct in6_addr *)daddr, + .sport = sport, + .dport = dport + }; + u64 seq; + net_secret_init(); + seq = siphash(&combined, offsetofend(typeof(combined), dport), + &net_secret); + seq += ktime_get_real_ns(); + seq &= (1ull << 48) - 1; + return seq; +} +EXPORT_SYMBOL(secure_dccpv6_sequence_number); +#endif +#endif |