From 683d3a3f04a8c282ed4338f31de67abbb90e37a6 Mon Sep 17 00:00:00 2001 From: James Prestwood Date: Thu, 16 Dec 2021 10:08:49 -0800 Subject: [PATCH] dpp: send presence announcements on StartEnrollee The presence procedure implemented is a far cry from what the spec actually wants. There are two reason for this: a) the kernels offchannel support is not at a level where it will work without rather annoying work arounds, and b) doing the procedure outlined in the spec will result in terrible discovery performance. Because of this a simpler single channel announcement is done by default and the full presence procedure is left out until/if it is needed. --- src/dpp.c | 243 ++++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 243 insertions(+) diff --git a/src/dpp.c b/src/dpp.c index 93dc19ae..0a42e321 100644 --- a/src/dpp.c +++ b/src/dpp.c @@ -24,15 +24,32 @@ #include #endif +#include + #include +#include "linux/nl80211.h" + #include "src/dbus.h" #include "src/netdev.h" #include "src/module.h" #include "src/dpp-util.h" #include "src/band.h" +#include "src/frame-xchg.h" +#include "src/offchannel.h" +#include "src/wiphy.h" +#include "src/ie.h" +#include "src/iwd.h" +#include "src/util.h" static uint32_t netdev_watch; +static struct l_genl_family *nl80211; +static uint8_t broadcast[] = { 0xff, 0xff, 0xff, 0xff, 0xff, 0xff }; + +enum dpp_state { + DPP_STATE_NOTHING, + DPP_STATE_PRESENCE, +}; struct dpp_sm { struct netdev *netdev; @@ -48,6 +65,17 @@ struct dpp_sm { size_t nonce_len; struct l_ecc_scalar *boot_private; struct l_ecc_point *boot_public; + + enum dpp_state state; + + uint32_t *freqs; + size_t freqs_len; + size_t freqs_idx; + uint32_t dwell; + uint32_t current_freq; + struct scan_freq_set *presence_list; + + uint32_t offchannel_id; }; static void dpp_reset(struct dpp_sm *dpp) @@ -56,6 +84,18 @@ static void dpp_reset(struct dpp_sm *dpp) l_free(dpp->uri); dpp->uri = NULL; } + + if (dpp->freqs) { + l_free(dpp->freqs); + dpp->freqs = NULL; + } + + if (dpp->offchannel_id) { + offchannel_cancel(dpp->wdev_id, dpp->offchannel_id); + dpp->offchannel_id = 0; + } + + dpp->state = DPP_STATE_NOTHING; } static void dpp_free(struct dpp_sm *dpp) @@ -80,12 +120,106 @@ static void dpp_free(struct dpp_sm *dpp) l_free(dpp); } +static void dpp_send_frame_cb(struct l_genl_msg *msg, void *user_data) +{ + if (l_genl_msg_get_error(msg) < 0) + l_error("Error sending frame"); +} + +static void dpp_send_frame(uint64_t wdev_id, struct iovec *iov, size_t iov_len, + uint32_t freq) +{ + struct l_genl_msg *msg; + + msg = l_genl_msg_new_sized(NL80211_CMD_FRAME, 512); + l_genl_msg_append_attr(msg, NL80211_ATTR_WDEV, 8, &wdev_id); + l_genl_msg_append_attr(msg, NL80211_ATTR_WIPHY_FREQ, 4, &freq); + l_genl_msg_append_attr(msg, NL80211_ATTR_OFFCHANNEL_TX_OK, 0, NULL); + l_genl_msg_append_attrv(msg, NL80211_ATTR_FRAME, iov, iov_len); + + l_debug("Sending frame on frequency %u", freq); + + if (!l_genl_family_send(nl80211, msg, dpp_send_frame_cb, NULL, NULL)) + l_error("Could not send CMD_FRAME"); +} + +static size_t dpp_append_attr(uint8_t *to, enum dpp_attribute_type type, + void *attr, size_t attr_len) +{ + l_put_le16(type, to); + l_put_le16(attr_len, to + 2); + memcpy(to + 4, attr, attr_len); + + return attr_len + 4; +} + +static size_t dpp_build_header(const uint8_t *src, const uint8_t *dest, + enum dpp_frame_type type, + uint8_t buf[static 32]) +{ + uint8_t *ptr = buf + 24; + + memset(buf, 0, 32); + + l_put_le16(0x00d0, buf); + memcpy(buf + 4, dest, 6); + memcpy(buf + 10, src, 6); + memcpy(buf + 16, broadcast, 6); + + *ptr++ = 0x04; /* Category: Public */ + *ptr++ = 0x09; /* Action: Vendor specific usage */ + memcpy(ptr, wifi_alliance_oui, 3); + ptr += 3; + *ptr++ = 0x1a; /* WiFi Alliance DPP OI type */ + *ptr++ = 1; /* Cryptosuite */ + *ptr++ = type; + + return ptr - buf; +} + +static void dpp_presence_announce(struct dpp_sm *dpp) +{ + struct netdev *netdev = dpp->netdev; + uint8_t hdr[32]; + uint8_t attrs[32 + 4]; + uint8_t hash[32]; + uint8_t *ptr = attrs; + const uint8_t *addr = netdev_get_address(netdev); + struct iovec iov[2]; + + iov[0].iov_len = dpp_build_header(addr, broadcast, + DPP_FRAME_PRESENCE_ANNOUNCEMENT, hdr); + iov[0].iov_base = hdr; + + dpp_hash(L_CHECKSUM_SHA256, hash, 2, "chirp", strlen("chirp"), + dpp->pub_asn1, dpp->pub_asn1_len); + + ptr += dpp_append_attr(ptr, DPP_ATTR_RESPONDER_BOOT_KEY_HASH, hash, 32); + + iov[1].iov_base = attrs; + iov[1].iov_len = ptr - attrs; + + l_debug("Sending presense annoucement on frequency %u and waiting %u", + dpp->current_freq, dpp->dwell); + + dpp_send_frame(netdev_get_wdev_id(netdev), iov, 2, dpp->current_freq); +} + +static void dpp_roc_started(void *user_data) +{ + struct dpp_sm *dpp = user_data; + + dpp_presence_announce(dpp); +} + static void dpp_create(struct netdev *netdev) { struct l_dbus *dbus = dbus_get_bus(); struct dpp_sm *dpp = l_new(struct dpp_sm, 1); dpp->netdev = netdev; + dpp->state = DPP_STATE_NOTHING; + dpp->wdev_id = netdev_get_wdev_id(netdev); dpp->curve = l_ecc_curve_from_ike_group(19); dpp->key_len = l_ecc_curve_get_scalar_bytes(dpp->curve); dpp->nonce_len = dpp_nonce_len_from_key_len(dpp->key_len); @@ -123,6 +257,97 @@ static void dpp_netdev_watch(struct netdev *netdev, } } +static void dpp_presence_timeout(int error, void *user_data) +{ + struct dpp_sm *dpp = user_data; + + if (dpp->state != DPP_STATE_PRESENCE) { + l_debug("DPP state changed, stopping presence announcements"); + dpp->freqs_idx = 0; + return; + } + + dpp->freqs_idx++; + + if (dpp->freqs_idx >= dpp->freqs_len) { + l_debug("Max retries on presence announcements"); + dpp->freqs_idx = 0; + } + + dpp->current_freq = dpp->freqs[dpp->freqs_idx]; + + l_debug("Presence timeout, moving to next frequency %u, duration %u", + dpp->current_freq, dpp->dwell); + + dpp->offchannel_id = offchannel_start(netdev_get_wdev_id(dpp->netdev), + dpp->current_freq, dpp->dwell, dpp_roc_started, + dpp, dpp_presence_timeout); +} + +/* + * EasyConnect 2.0 - 6.2.2 + */ +static uint32_t *dpp_add_default_channels(struct dpp_sm *dpp, size_t *len_out) +{ + struct wiphy *wiphy = wiphy_find_by_wdev( + netdev_get_wdev_id(dpp->netdev)); + const struct scan_freq_set *list = wiphy_get_supported_freqs(wiphy); + uint32_t freq; + + if (!dpp->presence_list) + dpp->presence_list = scan_freq_set_new(); + + scan_freq_set_add(dpp->presence_list, band_channel_to_freq(6, + BAND_FREQ_2_4_GHZ)); + /* + * "5 GHz: Channel 44 (5.220 GHz) if local regulations permit operation + * only in the 5.150 - 5.250 GHz band and Channel 149 (5.745 GHz) + * otherwise" + */ + freq = band_channel_to_freq(149, BAND_FREQ_5_GHZ); + + if (scan_freq_set_contains(list, freq)) + scan_freq_set_add(dpp->presence_list, freq); + else + scan_freq_set_add(dpp->presence_list, + band_channel_to_freq(44, BAND_FREQ_5_GHZ)); + + /* TODO: 60GHz: Channel 2 */ + + return scan_freq_set_to_fixed_array(dpp->presence_list, len_out); +} + +/* + * TODO: There is an entire procedure defined in the spec where you increase + * the ROC timeout with each unsuccessful iteration of channels, wait on channel + * for long periods of time etc. Due to offchannel issues in the kernel this + * procedure is not being fully implemented. In reality doing this would result + * in quite terrible DPP performance anyways. + */ +static void dpp_start_presence(struct dpp_sm *dpp, uint32_t *limit_freqs, + size_t limit_len) +{ + uint32_t max_roc = wiphy_get_max_roc_duration( + wiphy_find_by_wdev(dpp->wdev_id)); + + if (2000 < max_roc) + max_roc = 2000; + + if (limit_freqs) { + dpp->freqs = l_memdup(limit_freqs, sizeof(uint32_t) * limit_len); + dpp->freqs_len = limit_len; + } else + dpp->freqs = dpp_add_default_channels(dpp, &dpp->freqs_len); + + dpp->dwell = max_roc; + dpp->freqs_idx = 0; + dpp->current_freq = dpp->freqs[0]; + + dpp->offchannel_id = offchannel_start(netdev_get_wdev_id(dpp->netdev), + dpp->current_freq, dpp->dwell, dpp_roc_started, + dpp, dpp_presence_timeout); +} + static struct l_dbus_message *dpp_dbus_start_enrollee(struct l_dbus *dbus, struct l_dbus_message *message, void *user_data) @@ -131,12 +356,24 @@ static struct l_dbus_message *dpp_dbus_start_enrollee(struct l_dbus *dbus, uint32_t freq = band_channel_to_freq(6, BAND_FREQ_2_4_GHZ); struct l_dbus_message *reply; + if (dpp->state != DPP_STATE_NOTHING) + return dbus_error_busy(message); + dpp->uri = dpp_generate_uri(dpp->pub_asn1, dpp->pub_asn1_len, 2, netdev_get_address(dpp->netdev), &freq, 1, NULL, NULL); + dpp->state = DPP_STATE_PRESENCE; + l_debug("DPP Start Enrollee: %s", dpp->uri); + /* + * Going off spec here. Select a single channel to send presence + * announcements on. This will be advertised in the URI. The full + * presence procedure can be implemented if it is ever needed. + */ + dpp_start_presence(dpp, &freq, 1); + reply = l_dbus_message_new_method_return(message); l_dbus_message_set_arguments(reply, "s", dpp->uri); @@ -172,6 +409,12 @@ static void dpp_destroy_interface(void *user_data) static int dpp_init(void) { + nl80211 = l_genl_family_new(iwd_get_genl(), NL80211_GENL_NAME); + if (!nl80211) { + l_error("Failed to obtain nl80211"); + return -EIO; + } + netdev_watch = netdev_watch_add(dpp_netdev_watch, NULL, NULL); l_dbus_register_interface(dbus_get_bus(), IWD_DPP_INTERFACE,