diff options
Diffstat (limited to 'src')
| -rw-r--r-- | src/libcharon/plugins/kernel_wfp/kernel_wfp_ipsec.c | 61 |
1 files changed, 59 insertions, 2 deletions
diff --git a/src/libcharon/plugins/kernel_wfp/kernel_wfp_ipsec.c b/src/libcharon/plugins/kernel_wfp/kernel_wfp_ipsec.c index 0f78ef665..83248889b 100644 --- a/src/libcharon/plugins/kernel_wfp/kernel_wfp_ipsec.c +++ b/src/libcharon/plugins/kernel_wfp/kernel_wfp_ipsec.c @@ -42,6 +42,11 @@ struct private_kernel_wfp_ipsec_t { refcount_t nextspi; /** + * Mix value to distribute SPI allocation randomly + */ + u_int32_t mixspi; + + /** * Temporary SAD/SPD entries referenced reqid, as uintptr_t => entry_t */ hashtable_t *tsas; @@ -1204,11 +1209,58 @@ METHOD(kernel_ipsec_t, get_features, kernel_feature_t, return KERNEL_ESP_V3_TFC | KERNEL_NO_POLICY_UPDATES; } +/** + * Initialize seeds for SPI generation + */ +static bool init_spi(private_kernel_wfp_ipsec_t *this) +{ + bool ok = TRUE; + rng_t *rng; + + rng = lib->crypto->create_rng(lib->crypto, RNG_STRONG); + if (!rng) + { + return FALSE; + } + ok = rng->get_bytes(rng, sizeof(this->nextspi), (u_int8_t*)&this->nextspi); + if (ok) + { + ok = rng->get_bytes(rng, sizeof(this->mixspi), (u_int8_t*)&this->mixspi); + } + rng->destroy(rng); + return ok; +} + +/** + * Map an integer x with a one-to-one function using quadratic residues. + */ +static u_int permute(u_int x, u_int p) +{ + u_int qr; + + x = x % p; + qr = ((u_int64_t)x * x) % p; + if (x <= p / 2) + { + return qr; + } + return p - qr; +} + METHOD(kernel_ipsec_t, get_spi, status_t, private_kernel_wfp_ipsec_t *this, host_t *src, host_t *dst, u_int8_t protocol, u_int32_t reqid, u_int32_t *spi) { - *spi = htonl(ref_get(&this->nextspi)); + /* To avoid sequencial SPIs, we use a one-to-one permuation function on + * an incrementing counter, that is a full period PRNG for the range we + * allocate SPIs in. We add some randomness using a fixed XOR and start + * the counter at random position. This is not cryptographically safe, + * but that is actually not required. + * The selected prime should be smaller than the range we allocate SPIs + * in, and it must satisfy p % 4 == 3 to map x > p/2 using p - qr. */ + static const u_int p = 268435399, offset = 0xc0000000; + + *spi = htonl(offset + permute(ref_get(&this->nextspi) ^ this->mixspi, p)); return SUCCESS; } @@ -1646,7 +1698,6 @@ kernel_wfp_ipsec_t *kernel_wfp_ipsec_create() .providerKey = { 0x59cdae2e, 0xf6bb, 0x4c09, { 0xa9,0x59,0x9d,0x91,0xac,0xaf,0xf9,0x19 }}, }, - .nextspi = 0xc0000001, .mutex = mutex_create(MUTEX_TYPE_RECURSIVE), .tsas = hashtable_create(hashtable_hash_ptr, hashtable_equals_ptr, 4), .isas = hashtable_create((void*)hash_sa, (void*)equals_sa, 4), @@ -1654,6 +1705,12 @@ kernel_wfp_ipsec_t *kernel_wfp_ipsec_create() .routes = hashtable_create((void*)hash_route, (void*)equals_route, 4), ); + if (!init_spi(this)) + { + destroy(this); + return NULL; + } + res = FwpmEngineOpen0(NULL, RPC_C_AUTHN_WINNT, NULL, &session, &this->handle); if (res != ERROR_SUCCESS) |