Hi,
Den ons 12 feb. 2020 kl 14:30 skrev Howard Chung <howardchung@xxxxxxxxxx>:
>
> From: "howardchung@xxxxxxxxxx" <howardchung@xxxxxxxxxx>
>
> When kernel find out that the incoming Just-Works pairing is
> initiated by a paired device, it is user space's responsibility to
> decide the next action.
>
> This patch includes the following:
> - add JustWorksRepairing policy as an option in main.conf
> - handle the confirmation request from kernel
>
> ---
> The Just-Works repairing policy could be one of the following:
> - never: default; reject the repairing immediately.
> - confirm: prompt a confirmation dialog to user.
> - always: always accept the repairing.
>
> Changes in v2:
> - let RequestAuthorization handle the situation
> - remove the changes in client/
>
> src/agent.c | 16 ++++++++++++++++
> src/hcid.h | 8 ++++++++
> src/main.c | 27 +++++++++++++++++++++++++++
> src/main.conf | 5 +++++
> 4 files changed, 56 insertions(+)
>
> diff --git a/src/agent.c b/src/agent.c
> index e0ffcd22f..e013ec85f 100644
> --- a/src/agent.c
> +++ b/src/agent.c
> @@ -773,12 +773,28 @@ int agent_request_authorization(struct agent *agent, struct btd_device *device,
> GDestroyNotify destroy)
> {
> struct agent_request *req;
> + DBusError dbus_err;
> int err;
>
> err = agent_has_request(agent, device, AGENT_REQUEST_AUTHORIZATION);
> if (err)
> return err;
>
> + /* Just-Works repairing policy */
> + if (device_is_paired(device, BDADDR_BREDR) ||
> + device_is_paired(device, BDADDR_LE_PUBLIC)) {
> + if (main_opts.jw_repairing == JW_REPAIRING_NEVER) {
> + dbus_error_init(&dbus_err);
> + dbus_set_error_const(&dbus_err,
> + ERROR_INTERFACE ".Rejected", NULL);
> + cb(agent, &dbus_err, user_data);
> + return 0;
> + } else if (main_opts.jw_repairing == JW_REPAIRING_ALWAYS) {
> + cb(agent, NULL, user_data);
> + return 0;
> + }
> + }
> +
> DBG("Calling Agent.RequestAuthorization: name=%s, path=%s",
> agent->owner, agent->path);
>
> diff --git a/src/hcid.h b/src/hcid.h
> index adea85ce2..bcd2b9fa1 100644
> --- a/src/hcid.h
> +++ b/src/hcid.h
> @@ -35,6 +35,12 @@ typedef enum {
> BT_GATT_CACHE_NO,
> } bt_gatt_cache_t;
>
> +enum {
> + JW_REPAIRING_NEVER,
> + JW_REPAIRING_CONFIRM,
> + JW_REPAIRING_ALWAYS,
> +} jw_repairing_t;
> +
> struct main_opts {
> char *name;
> uint32_t class;
> @@ -58,6 +64,8 @@ struct main_opts {
> uint16_t gatt_mtu;
>
> uint8_t key_size;
> +
> + jw_repairing_t jw_repairing;
> };
>
> extern struct main_opts main_opts;
> diff --git a/src/main.c b/src/main.c
> index 1a6ab36a3..d67f469f1 100644
> --- a/src/main.c
> +++ b/src/main.c
> @@ -93,6 +93,7 @@ static const char *supported_options[] = {
> "MultiProfile",
> "FastConnectable",
> "Privacy",
> + "JustWorksRepairing",
> NULL
> };
>
> @@ -193,6 +194,20 @@ static bt_gatt_cache_t parse_gatt_cache(const char *cache)
> }
> }
>
> +static jw_repairing_t parse_jw_repairing(const char *jw_repairing)
> +{
> + if (!strcmp(jw_repairing, "never")) {
> + return JW_REPAIRING_NEVER;
> + } else if (!strcmp(jw_repairing, "confirm")) {
> + return JW_REPAIRING_CONFIRM;
> + } else if (!strcmp(jw_repairing, "always")) {
> + return JW_REPAIRING_ALWAYS;
> + } else {
> + return JW_REPAIRING_NEVER;
> + }
> +}
> +
> +
> static void check_options(GKeyFile *config, const char *group,
> const char **options)
> {
> @@ -331,6 +346,18 @@ static void parse_config(GKeyFile *config)
> g_free(str);
> }
>
> + str = g_key_file_get_string(config, "General",
> + "JustWorksRepairing", &err);
> + if (err) {
> + DBG("%s", err->message);
> + g_clear_error(&err);
> + main_opts.jw_repairing = JW_REPAIRING_NEVER;
> + } else {
> + DBG("just_works_repairing=%s", str);
> + main_opts.jw_repairing = parse_jw_repairing(str);
> + g_free(str);
> + }
> +
> str = g_key_file_get_string(config, "General", "Name", &err);
> if (err) {
> DBG("%s", err->message);
> diff --git a/src/main.conf b/src/main.conf
> index 40687a755..bb5ff5b15 100644
> --- a/src/main.conf
> +++ b/src/main.conf
> @@ -72,6 +72,11 @@
> # Defaults to "off"
> # Privacy = off
>
> +# Specify the policy to the JUST-WORKS repairing initiated by peer
> +# Possible values: "never", "confirm", "always"
> +# Defaults to "never"
> +#JustWorksRepairing = never
> +
> [GATT]
> # GATT attribute cache.
> # Possible values:
> --
> 2.25.0.225.g125e21ebc7-goog
>
I haven't looked much into this, but have a question. What happens by
default currently when we have an already bonded device previously
paired using some MITM-protected mechanism, and suddenly wants to
re-bond using a less secure mechanism (Just Works)? In my opinion
denying this should obviously be the default in case no agent is
available, compared to if pairing a new device then the default should
be accept.
/Emil
