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gap: abort SSP pairing if MITM protection required but not possible

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This commit is contained in:
Matthias Ringwald 2021-05-25 15:04:25 +02:00
parent e276e383d1
commit 17c6fe5cac
2 changed files with 37 additions and 2 deletions
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1
CHANGELOG.md
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@ -80,6 +80,7 @@ and this project adheres to [Semantic Versioning](http://semver.org/spec/v2.0.0.
- SM: start pairing as Central for already encrypted connection on Slave Security Request
- GAP: provide Device ID from EIR in GAP_EVENT_INQUIRY_RESULT
- GAP: only store link key if it allows requested security level
- GAP: abort SSP pairing if MITM protection required but not possible
## Release v1.3.2

38
src/hci.c
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@ -2320,6 +2320,38 @@ static void event_handle_le_connection_complete(const uint8_t * packet){
}
#endif
#ifdef ENABLE_CLASSIC
static bool hci_ssp_security_level_possible_for_io_cap(gap_security_level_t level, uint8_t io_cap_local, uint8_t io_cap_remote){
if (io_cap_local == SSP_IO_CAPABILITY_UNKNOWN) return false;
// LEVEL_4 is tested by l2cap
// LEVEL 3 requires MITM protection -> check io capabilities
if (level >= LEVEL_3){
if (io_cap_remote >= SSP_IO_CAPABILITY_NO_INPUT_NO_OUTPUT) return false;
if (io_cap_local >= SSP_IO_CAPABILITY_NO_INPUT_NO_OUTPUT) return false;
if ((io_cap_remote == SSP_IO_CAPABILITY_KEYBOARD_ONLY) && (io_cap_local == SSP_IO_CAPABILITY_KEYBOARD_ONLY)) return false;
}
// LEVEL 2 requires SSP, which is a given
return true;
}
static bool hci_ssp_validate_possible_security_level(bd_addr_t addr){
hci_connection_t * conn = hci_connection_for_bd_addr_and_type(addr, BD_ADDR_TYPE_ACL);
if (!conn) return false;
// abort pairing, if requested security level cannot be met
if (hci_ssp_security_level_possible_for_io_cap(conn->requested_security_level, hci_stack->ssp_io_capability, conn->io_cap_response_io)) {
// inlined hci_add_connection_flags_for_flipped_bd_addr
connectionSetAuthenticationFlags(conn, SSP_PAIRING_ACTIVE);
hci_connection_timestamp(conn);
return true;
} else {
log_info("Level %u cannot be reached", conn->requested_security_level);
conn->bonding_flags |= BONDING_DISCONNECT_SECURITY_BLOCK;
return false;
};
}
#endif
static void event_handler(uint8_t *packet, uint16_t size){
uint16_t event_length = packet[1];
@ -2679,13 +2711,15 @@ static void event_handler(uint8_t *packet, uint16_t size){
#endif
case HCI_EVENT_USER_CONFIRMATION_REQUEST:
hci_add_connection_flags_for_flipped_bd_addr(&packet[2], SSP_PAIRING_ACTIVE);
hci_event_user_confirmation_request_get_bd_addr(packet, addr);
if (hci_ssp_validate_possible_security_level(addr) == false) break;
if (!hci_stack->ssp_auto_accept) break;
hci_add_connection_flags_for_flipped_bd_addr(&packet[2], SEND_USER_CONFIRM_REPLY);
break;
case HCI_EVENT_USER_PASSKEY_REQUEST:
hci_add_connection_flags_for_flipped_bd_addr(&packet[2], SSP_PAIRING_ACTIVE);
hci_event_user_passkey_request_get_bd_addr(packet, addr);
if (hci_ssp_validate_possible_security_level(addr) == false) break;
if (!hci_stack->ssp_auto_accept) break;
hci_add_connection_flags_for_flipped_bd_addr(&packet[2], SEND_USER_PASSKEY_REPLY);
break;