Hi Alain, Marcel, On Wed, Jan 8, 2020 at 12:08 PM Alain Michaud <alainmichaud@xxxxxxxxxx> wrote: > > Hi Luiz, > > > On Wed, Jan 8, 2020 at 3:00 PM Luiz Augusto von Dentz > <luiz.dentz@xxxxxxxxx> wrote: > > > > Hi Alain, > > > > On Wed, Jan 8, 2020 at 7:04 AM Alain Michaud <alainmichaud@xxxxxxxxxx> wrote: > > > > > > Hi Luiz, > > > > > > > > > On Tue, Jan 7, 2020 at 6:22 PM Luiz Augusto von Dentz > > > <luiz.dentz@xxxxxxxxx> wrote: > > > > > > > > Hi Alain, > > > > > > > > On Mon, Jan 6, 2020 at 5:31 PM Alain Michaud <alainm@xxxxxxxxxxxx> wrote: > > > > > > > > > > This change accomplishes 2 things: > > > > > 1. Drop device security data from previously paired devices > > > > > using blocked keys. > > > > > 2. Send the list of known bad keys that should be blocked to the kernel > > > > > if supported. > > > > > > > > > > In particular keys from the Google Titan Security key are being > > > > > blocked. > > > > > > > > > > For additional background information, please see > > > > > https://security.googleblog.com/2019/05/titan-keys-update.html > > > > > --- > > > > > > > > > > src/adapter.c | 140 +++++++++++++++++++++++++++++++++++++++++++++++--- > > > > > 1 file changed, 134 insertions(+), 6 deletions(-) > > > > > > > > > > diff --git a/src/adapter.c b/src/adapter.c > > > > > index cef25616f..9c41ebe86 100644 > > > > > --- a/src/adapter.c > > > > > +++ b/src/adapter.c > > > > > @@ -99,10 +99,27 @@ > > > > > #define DISTANCE_VAL_INVALID 0x7FFF > > > > > #define PATHLOSS_MAX 137 > > > > > > > > > > +/* > > > > > + * These are known security keys that have been compromised. > > > > > + * If this grows or there are needs to be platform specific, it is > > > > > + * conceivable that these could be read from a config file. > > > > > + */ > > > > > +static const struct mgmt_blocked_key_info blocked_keys[] = { > > > > > + /* Google Titan Security Keys */ > > > > > + { HCI_BLOCKED_KEY_TYPE_LTK, > > > > > + {0xbf, 0x01, 0xfb, 0x9d, 0x4e, 0xf3, 0xbc, 0x36, > > > > > + 0xd8, 0x74, 0xf5, 0x39, 0x41, 0x38, 0x68, 0x4c}}, > > > > > + { HCI_BLOCKED_KEY_TYPE_IRK, > > > > > + {0xa5, 0x99, 0xba, 0xe4, 0xe1, 0x7c, 0xa6, 0x18, > > > > > + 0x22, 0x8e, 0x07, 0x56, 0xb4, 0xe8, 0x5f, 0x01}}, > > > > > +}; > > > > > + > > > > > static DBusConnection *dbus_conn = NULL; > > > > > > > > > > static bool kernel_conn_control = false; > > > > > > > > > > +static bool kernel_blocked_keys_supported = false; > > > > > + > > > > > static GList *adapter_list = NULL; > > > > > static unsigned int adapter_remaining = 0; > > > > > static bool powering_down = false; > > > > > @@ -124,6 +141,7 @@ struct link_key_info { > > > > > unsigned char key[16]; > > > > > uint8_t type; > > > > > uint8_t pin_len; > > > > > + bool is_blocked; > > > > > }; > > > > > > > > > > struct smp_ltk_info { > > > > > @@ -135,12 +153,14 @@ struct smp_ltk_info { > > > > > uint16_t ediv; > > > > > uint64_t rand; > > > > > uint8_t val[16]; > > > > > + bool is_blocked; > > > > > }; > > > > > > > > > > struct irk_info { > > > > > bdaddr_t bdaddr; > > > > > uint8_t bdaddr_type; > > > > > uint8_t val[16]; > > > > > + bool is_blocked; > > > > > }; > > > > > > > > > > struct conn_param { > > > > > @@ -3439,6 +3459,20 @@ static int str2buf(const char *str, uint8_t *buf, size_t blen) > > > > > return 0; > > > > > } > > > > > > > > > > +static bool is_blocked_key(uint8_t key_type, uint8_t *key_value) > > > > > +{ > > > > > + uint32_t i = 0; > > > > > + > > > > > + for (i = 0; i < ARRAY_SIZE(blocked_keys); ++i) { > > > > > + if (key_type == blocked_keys[i].type && > > > > > + !memcmp(blocked_keys[i].val, key_value, > > > > > + sizeof(blocked_keys[i].val))) > > > > > + return true; > > > > > + } > > > > > + > > > > > + return false; > > > > > +} > > > > > + > > > > > static struct link_key_info *get_key_info(GKeyFile *key_file, const char *peer) > > > > > { > > > > > struct link_key_info *info = NULL; > > > > > @@ -3461,6 +3495,9 @@ static struct link_key_info *get_key_info(GKeyFile *key_file, const char *peer) > > > > > info->pin_len = g_key_file_get_integer(key_file, "LinkKey", "PINLength", > > > > > NULL); > > > > > > > > > > + info->is_blocked = is_blocked_key(HCI_BLOCKED_KEY_TYPE_LINKKEY, > > > > > + info->key); > > > > > + > > > > > failed: > > > > > g_free(str); > > > > > > > > > > @@ -3534,6 +3571,9 @@ static struct smp_ltk_info *get_ltk(GKeyFile *key_file, const char *peer, > > > > > else > > > > > ltk->master = master; > > > > > > > > > > + ltk->is_blocked = is_blocked_key(HCI_BLOCKED_KEY_TYPE_LTK, > > > > > + ltk->val); > > > > > + > > > > > failed: > > > > > g_free(key); > > > > > g_free(rand); > > > > > @@ -3584,6 +3624,9 @@ static struct irk_info *get_irk_info(GKeyFile *key_file, const char *peer, > > > > > else > > > > > str2buf(&str[0], irk->val, sizeof(irk->val)); > > > > > > > > > > + irk->is_blocked = is_blocked_key(HCI_BLOCKED_KEY_TYPE_LINKKEY, > > > > > + irk->val); > > > > > + > > > > > failed: > > > > > g_free(str); > > > > > > > > > > @@ -4142,21 +4185,55 @@ static void load_devices(struct btd_adapter *adapter) > > > > > g_key_file_load_from_file(key_file, filename, 0, NULL); > > > > > > > > > > key_info = get_key_info(key_file, entry->d_name); > > > > > - if (key_info) > > > > > - keys = g_slist_append(keys, key_info); > > > > > > > > > > bdaddr_type = get_le_addr_type(key_file); > > > > > > > > > > ltk_info = get_ltk_info(key_file, entry->d_name, bdaddr_type); > > > > > - if (ltk_info) > > > > > - ltks = g_slist_append(ltks, ltk_info); > > > > > > > > > > slave_ltk_info = get_slave_ltk_info(key_file, entry->d_name, > > > > > bdaddr_type); > > > > > + > > > > > + irk_info = get_irk_info(key_file, entry->d_name, bdaddr_type); > > > > > + > > > > > + // If any key for the device is blocked, we discard all. > > > > > + if ((key_info && key_info->is_blocked) || > > > > > + (ltk_info && ltk_info->is_blocked) || > > > > > + (slave_ltk_info && > > > > > + slave_ltk_info->is_blocked) || > > > > > + (irk_info && irk_info->is_blocked)) { > > > > > > > > Perhaps it would be more efficient if we don't add is_blocked as a > > > > member of these keys and instead pass bool variable to get_*_info > > > > which just set it in case the key is blocked, that way if is_blocked > > > > is set for get_key_info you don't have to free anything. Also it might > > > > be a good idea to move the handling of loading the keys to another > > > > function i.e. load_keys to make it simpler to bail out, etc. Have you > > > > though about the possibility of just using a the device block API when > > > > you detect it is using compromised keys? That way the application can > > > > detect the device is in fact blocked and can either remove the device, > > > > which would clean up the storage as well (see my comments bellow), or > > > > unblock it in order to continue using the device. > > > > > > My thoughts was to keep the contract simple. if the return is not > > > null then a key exists, it can be blocked or not blocked. It feels a > > > bit weird to have a contract return null but a parameter tells you > > > that it's been blocked. The extra allocation/free doesn't seem like a > > > lot of overhead for what is expected to be a rare case (blocked keys). > > > > Fair enough, I suggested that because the is_block logic seems to > > apply to all of the keys not just the key that was compromised, anyway > > Im probably getting a little too paranoid regarding overhead but I > > don't think we had loose anything by avoiding the extra > > allocation/free > Correct. The idea is that if any of the keys from the device is > blocked, the device > is simply ignored. > > > > > > > > > > > > + if (key_info) { > > > > > + g_free(key_info); > > > > > + key_info = NULL; > > > > > + } > > > > > + > > > > > + if (ltk_info) { > > > > > + g_free(ltk_info); > > > > > + ltk_info = NULL; > > > > > + } > > > > > + > > > > > + if (slave_ltk_info) { > > > > > + g_free(slave_ltk_info); > > > > > + slave_ltk_info = NULL; > > > > > + } > > > > > + > > > > > + if (irk_info) { > > > > > + g_free(irk_info); > > > > > + irk_info = NULL; > > > > > + } > > > > > + > > > > > + goto free; > > > > > + } > > > > > + > > > > > + if (key_info) > > > > > + keys = g_slist_append(keys, key_info); > > > > > + > > > > > + if (ltk_info) > > > > > + ltks = g_slist_append(ltks, ltk_info); > > > > > + > > > > > > > > Perhaps I missing something but don't we need to clear these keys form > > > > the storage once we figure they are blocked or there is any reason to > > > > leave them in there so we can unblock? > > > Since these are expected to be rare cases, I didn't go through the > > > extent to clear them from storage. Having them in storage also can > > > help with diagnosability. > > > > That is an interesting point, but we don't allow new pairing with > > compromised keys with these changes or do we? If we want to allow > > diagnosing in all cases we could actually store the blocked flag into > > the storage so something like a diagnostic tool can fetch the > > information directly. > With these changes, the device is simply dropped from the list > entirely. The user is free to attempt to pair it again. If the > device is fixed, pairing will work and the key will be overwritten, if > the device is still broken, the pairing will fail and the user will > see the error. Given that for now, the keys are hardcoded and a > relatively small list, it feels like overkill to store an additional > flag for it. This may be something we'd want to do if the list of > blocked keys grows beyond something that is easily manageable. If > that is the case, I also think we should read the blocked keys from a > configuration file rather than hardcoded in the code as it currently > is. All good, just waiting the kernel changes to be applied then we can go ahead with these changes as well, @Marcel are you planning to merge the kernel changes? > > > > > > > > > > > if (slave_ltk_info) > > > > > ltks = g_slist_append(ltks, slave_ltk_info); > > > > > > > > > > - irk_info = get_irk_info(key_file, entry->d_name, bdaddr_type); > > > > > if (irk_info) > > > > > irks = g_slist_append(irks, irk_info); > > > > > > > > > > @@ -8568,6 +8645,42 @@ static bool set_static_addr(struct btd_adapter *adapter) > > > > > return false; > > > > > } > > > > > > > > > > +static void set_blocked_keys_complete(uint8_t status, uint16_t length, > > > > > + const void *param, void *user_data) > > > > > +{ > > > > > + struct btd_adapter *adapter = user_data; > > > > > + > > > > > + if (status != MGMT_STATUS_SUCCESS) { > > > > > + btd_error(adapter->dev_id, > > > > > + "Failed to set blocked keys: %s (0x%02x)", > > > > > + mgmt_errstr(status), status); > > > > > + return; > > > > > + } > > > > > + > > > > > + DBG("Successfully set blocked keys for index %u", adapter->dev_id); > > > > > +} > > > > > + > > > > > +static bool set_blocked_keys(struct btd_adapter *adapter) > > > > > +{ > > > > > + uint8_t buffer[sizeof(struct mgmt_cp_set_blocked_keys) + > > > > > + sizeof(blocked_keys)] = { 0 }; > > > > > + struct mgmt_cp_set_blocked_keys *cp = > > > > > + (struct mgmt_cp_set_blocked_keys *)buffer; > > > > > + int i; > > > > > + > > > > > + cp->key_count = ARRAY_SIZE(blocked_keys); > > > > > + for (i = 0; i < cp->key_count; ++i) { > > > > > + cp->keys[i].type = blocked_keys[i].type; > > > > > + memcpy(cp->keys[i].val, blocked_keys[i].val, > > > > > + sizeof(cp->keys[i].val)); > > > > > + } > > > > > + > > > > > + return mgmt_send(mgmt_master, MGMT_OP_SET_BLOCKED_KEYS, adapter->dev_id, > > > > > + sizeof(buffer), buffer, > > > > > + set_blocked_keys_complete, > > > > > + adapter, NULL); > > > > > +} > > > > > + > > > > > static void read_info_complete(uint8_t status, uint16_t length, > > > > > const void *param, void *user_data) > > > > > { > > > > > @@ -8795,6 +8908,13 @@ static void read_info_complete(uint8_t status, uint16_t length, > > > > > > > > > > set_name(adapter, btd_adapter_get_name(adapter)); > > > > > > > > > > + if (kernel_blocked_keys_supported && !set_blocked_keys(adapter)) { > > > > > + btd_error(adapter->dev_id, > > > > > + "Failed to set blocked keys for index %u", > > > > > + adapter->dev_id); > > > > > + goto failed; > > > > > + } > > > > > + > > > > > if (main_opts.pairable && > > > > > !(adapter->current_settings & MGMT_SETTING_BONDABLE)) > > > > > set_mode(adapter, MGMT_OP_SET_BONDABLE, 0x01); > > > > > @@ -8972,9 +9092,17 @@ static void read_commands_complete(uint8_t status, uint16_t length, > > > > > for (i = 0; i < num_commands; i++) { > > > > > uint16_t op = get_le16(rp->opcodes + i); > > > > > > > > > > - if (op == MGMT_OP_ADD_DEVICE) { > > > > > + switch (op) { > > > > > + case MGMT_OP_ADD_DEVICE: > > > > > DBG("enabling kernel-side connection control"); > > > > > kernel_conn_control = true; > > > > > + break; > > > > > + case MGMT_OP_SET_BLOCKED_KEYS: > > > > > + DBG("kernel supports the set_blocked_keys op"); > > > > > + kernel_blocked_keys_supported = true; > > > > > + break; > > > > > + default: > > > > > + break; > > > > > } > > > > > } > > > > > } > > > > > -- > > > > > 2.24.1.735.g03f4e72817-goog > > > > > > > > > > > > > > > > > -- > > > > Luiz Augusto von Dentz > > > > > > > > -- > > Luiz Augusto von Dentz -- Luiz Augusto von Dentz
