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Bluetooth: SMP: Re-pairing cannot lower the security level of the bond

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Make sure that a new pairing procedure with an existing bond does not
result in a security with weaker security properties.

Signed-off-by: Joakim Andersson <joakim.andersson@nordicsemi.no>
This commit is contained in:
Joakim Andersson 2019-08-22 10:38:24 +02:00 • committed by Carles Cufí
commit b35075d595
1 changed files with 67 additions and 12 deletions
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79
subsys/bluetooth/host/smp.c
View file

@ -304,10 +304,20 @@ no_callbacks:
}
}
#if !defined(CONFIG_BT_SMP_SC_PAIR_ONLY)
static u8_t legacy_get_pair_method(struct bt_smp *smp, u8_t remote_io);
#endif
static u8_t get_pair_method(struct bt_smp *smp, u8_t remote_io)
{
struct bt_smp_pairing *req, *rsp;
#if !defined(CONFIG_BT_SMP_SC_PAIR_ONLY)
if (!atomic_test_bit(smp->flags, SMP_FLAG_SC)) {
return legacy_get_pair_method(smp, remote_io);
}
#endif
req = (struct bt_smp_pairing *)&smp->preq[1];
rsp = (struct bt_smp_pairing *)&smp->prsp[1];
@ -587,6 +597,39 @@ static u8_t get_encryption_key_size(struct bt_smp *smp)
return MIN(req->max_key_size, rsp->max_key_size);
}
/* Check that if a new pairing procedure with an existing bond will not lower
* the established security level of the bond.
*/
bool update_keys_check(struct bt_smp *smp)
{
struct bt_conn *conn = smp->chan.chan.conn;
if (!conn->le.keys) {
conn->le.keys = bt_keys_get_addr(conn->id, &conn->le.dst);
}
if (!conn->le.keys ||
!(conn->le.keys->keys & (BT_KEYS_LTK_P256 | BT_KEYS_LTK))) {
return true;
}
if (conn->le.keys->enc_size > get_encryption_key_size(smp)) {
return false;
}
if ((conn->le.keys->keys & BT_KEYS_LTK_P256) &&
!atomic_test_bit(smp->flags, SMP_FLAG_SC)) {
return false;
}
if ((conn->le.keys->flags & BT_KEYS_AUTHENTICATED) &&
smp->method == JUST_WORKS) {
return false;
}
return true;
}
#if defined(CONFIG_BT_PRIVACY) || defined(CONFIG_BT_SIGNING) || \
!defined(CONFIG_BT_SMP_SC_PAIR_ONLY)
/* For TX callbacks */
@ -2064,14 +2107,12 @@ static u8_t legacy_send_pairing_confirm(struct bt_smp *smp)
}
#if defined(CONFIG_BT_PERIPHERAL)
static u8_t legacy_pairing_req(struct bt_smp *smp, u8_t remote_io)
static u8_t legacy_pairing_req(struct bt_smp *smp)
{
u8_t ret;
BT_DBG("");
smp->method = legacy_get_pair_method(smp, remote_io);
/* ask for consent if pairing is not due to sending SecReq*/
if ((DISPLAY_FIXED(smp) || smp->method == JUST_WORKS) &&
!atomic_test_bit(smp->flags, SMP_FLAG_SEC_REQ) &&
@ -2270,14 +2311,12 @@ static u8_t smp_master_ident(struct bt_smp *smp, struct net_buf *buf)
}
#if defined(CONFIG_BT_CENTRAL)
static u8_t legacy_pairing_rsp(struct bt_smp *smp, u8_t remote_io)
static u8_t legacy_pairing_rsp(struct bt_smp *smp)
{
u8_t ret;
BT_DBG("");
smp->method = legacy_get_pair_method(smp, remote_io);
/* ask for consent if this is due to received SecReq */
if ((DISPLAY_FIXED(smp) || smp->method == JUST_WORKS) &&
atomic_test_bit(smp->flags, SMP_FLAG_SEC_REQ) &&
@ -2528,16 +2567,20 @@ static u8_t smp_pairing_req(struct bt_smp *smp, struct net_buf *buf)
atomic_set_bit(smp->flags, SMP_FLAG_PAIRING);
smp->method = get_pair_method(smp, req->io_capability);
if (!update_keys_check(smp)) {
return BT_SMP_ERR_AUTH_REQUIREMENTS;
}
if (!atomic_test_bit(smp->flags, SMP_FLAG_SC)) {
#if defined(CONFIG_BT_SMP_SC_PAIR_ONLY)
return BT_SMP_ERR_AUTH_REQUIREMENTS;
#else
return legacy_pairing_req(smp, req->io_capability);
return legacy_pairing_req(smp);
#endif /* CONFIG_BT_SMP_SC_PAIR_ONLY */
}
smp->method = get_pair_method(smp, req->io_capability);
if ((IS_ENABLED(CONFIG_BT_SMP_SC_ONLY) ||
conn->required_sec_level == BT_SECURITY_FIPS) &&
smp->method == JUST_WORKS) {
@ -2698,16 +2741,20 @@ static u8_t smp_pairing_rsp(struct bt_smp *smp, struct net_buf *buf)
atomic_set_bit(smp->flags, SMP_FLAG_BOND);
}
smp->method = get_pair_method(smp, rsp->io_capability);
if (!update_keys_check(smp)) {
return BT_SMP_ERR_AUTH_REQUIREMENTS;
}
if (!atomic_test_bit(smp->flags, SMP_FLAG_SC)) {
#if defined(CONFIG_BT_SMP_SC_PAIR_ONLY)
return BT_SMP_ERR_AUTH_REQUIREMENTS;
#else
return legacy_pairing_rsp(smp, rsp->io_capability);
return legacy_pairing_rsp(smp);
#endif /* CONFIG_BT_SMP_SC_PAIR_ONLY */
}
smp->method = get_pair_method(smp, rsp->io_capability);
if ((IS_ENABLED(CONFIG_BT_SMP_SC_ONLY) ||
conn->required_sec_level == BT_SECURITY_FIPS) &&
smp->method == JUST_WORKS) {
@ -3556,6 +3603,14 @@ static u8_t smp_public_key(struct bt_smp *smp, struct net_buf *buf)
if (memcmp(smp->pkey, sc_debug_public_key, 64) == 0) {
BT_INFO("Remote is using Debug Public key");
atomic_set_bit(smp->flags, SMP_FLAG_SC_DEBUG_KEY);
/* Don't allow a bond established without debug key to be
* updated using LTK generated from debug key.
*/
if (smp->chan.chan.conn->le.keys &&
!(smp->chan.chan.conn->le.keys->flags & BT_KEYS_DEBUG)) {
return BT_SMP_ERR_AUTH_REQUIREMENTS;
}
}
if (IS_ENABLED(CONFIG_BT_CENTRAL) &&