[PATCH v3 09/11] dpp: add support for configuration protocol

[James Prestwood <prestwoj at gmail.com>]

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This is a minimal implementation only supporting legacy network
configuration, i.e. only SSID and PSK/passphrase are supported.

Missing features include:
 - Fragmentation/comeback delay support
 - DPP AKM support
 - 8021x/PKEX support
---
 src/dpp.c | 297 ++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 297 insertions(+)

diff --git a/src/dpp.c b/src/dpp.c
index ec6ddc0c..af6a5fd0 100644
--- a/src/dpp.c
+++ b/src/dpp.c
@@ -44,6 +44,8 @@
 #include "src/crypto.h"
 #include "src/mpdu.h"
 #include "ell/useful.h"
+#include "src/common.h"
+#include "src/storage.h"
 
 static uint32_t netdev_watch;
 static struct l_genl_family *nl80211;
@@ -53,6 +55,7 @@ enum dpp_state {
 	DPP_STATE_NOTHING,
 	DPP_STATE_PRESENCE,
 	DPP_STATE_AUTHENTICATING,
+	DPP_STATE_CONFIGURING,
 };
 
 struct dpp_sm {
@@ -84,6 +87,7 @@ struct dpp_sm {
 	uint8_t auth_addr[6];
 	uint8_t r_nonce[32];
 	uint8_t i_nonce[32];
+	uint8_t e_nonce[32];
 
 	uint64_t ke[L_ECC_MAX_DIGITS];
 	uint64_t k2[L_ECC_MAX_DIGITS];
@@ -92,6 +96,8 @@ struct dpp_sm {
 	struct l_ecc_point *proto_public;
 
 	struct l_ecc_point *i_proto_public;
+
+	uint8_t diag_token;
 };
 
 static void dpp_send_frame_cb(struct l_genl_msg *msg, void *user_data)
@@ -186,6 +192,13 @@ static size_t dpp_append_wrapped_data(uint8_t *hdr, uint8_t *wrap_start,
 		ad_size++;
 	}
 
+	/* The configuration result requires this zero-length data component */
+	if (hdr && hdr[5] == DPP_FRAME_CONFIGURATION_RESULT) {
+		ad[1].iov_base = NULL;
+		ad[1].iov_len = 0;
+		ad_size++;
+	}
+
 	va_start(va, num_attrs);
 
 	/* Count up total attributes length */
@@ -266,6 +279,284 @@ static size_t dpp_build_header(const uint8_t *src, const uint8_t *dest,
 	return ptr - buf;
 }
 
+static size_t dpp_build_config_header(const uint8_t *src, const uint8_t *dest,
+					uint8_t diag_token,
+					uint8_t buf[static 37])
+{
+	uint8_t *ptr = buf + 24;
+
+	memset(buf, 0, 37);
+
+	l_put_le16(0x00d0, buf);
+	memcpy(buf + 4, dest, 6);
+	memcpy(buf + 10, src, 6);
+	memcpy(buf + 16, broadcast, 6);
+
+	*ptr++ = 0x04; /* Public */
+	*ptr++ = 0x0a; /* Action */
+	*ptr++ = diag_token;
+
+	*ptr++ = IE_TYPE_ADVERTISEMENT_PROTOCOL;
+	*ptr++ = 8; /* len */
+	*ptr++ = 0x00;
+	*ptr++ = IE_TYPE_VENDOR_SPECIFIC;
+	*ptr++ = 5;
+	memcpy(ptr, wifi_alliance_oui, 3);
+	ptr += 3;
+	*ptr++ = 0x1a;
+	*ptr++ = 1;
+
+	return ptr - buf;
+}
+
+static void dpp_configuration_start(struct dpp_sm *dpp, const uint8_t *addr)
+{
+	const char *json = "{\"name\":\"IWD\",\"wi-fi_tech\":\"infra\","
+				"\"netRole\":\"sta\"}";
+	struct iovec iov[3];
+	uint8_t hdr[37];
+	uint8_t attrs[512];
+	size_t json_len = strlen(json);
+	uint8_t *ptr = attrs;
+
+	l_getrandom(&dpp->diag_token, 1);
+
+	iov[0].iov_len = dpp_build_config_header(
+					netdev_get_address(dpp->netdev),
+					addr, dpp->diag_token, hdr);
+	iov[0].iov_base = hdr;
+
+	l_getrandom(dpp->e_nonce, dpp->nonce_len);
+
+	/* length */
+	ptr += 2;
+
+	ptr += dpp_append_wrapped_data(NULL, NULL, ptr, sizeof(attrs),
+			dpp->ke, dpp->key_len, 2,
+			DPP_ATTR_ENROLLEE_NONCE, dpp->nonce_len, dpp->e_nonce,
+			DPP_ATTR_CONFIGURATION_REQUEST, json_len, json);
+
+	l_put_le16(ptr - attrs - 2, attrs);
+
+	iov[1].iov_base = attrs;
+	iov[1].iov_len = ptr - attrs;
+
+	dpp->state = DPP_STATE_CONFIGURING;
+
+	dpp_send_frame(dpp->wdev_id, iov, 2, dpp->current_freq);
+}
+
+static void send_config_result(struct dpp_sm *dpp, const uint8_t *to)
+{
+	uint8_t hdr[32];
+	struct iovec iov[2];
+	uint8_t attrs[256];
+	uint8_t *ptr = attrs;
+	uint8_t zero = 0;
+
+	iov[0].iov_len = dpp_build_header(netdev_get_address(dpp->netdev), to,
+					DPP_FRAME_CONFIGURATION_RESULT, hdr);
+	iov[0].iov_base = hdr;
+
+	ptr += dpp_append_wrapped_data(hdr + 26, NULL, ptr, sizeof(attrs),
+			dpp->ke, dpp->key_len, 2,
+			DPP_ATTR_STATUS, 1, &zero,
+			DPP_ATTR_ENROLLEE_NONCE, dpp->nonce_len, dpp->e_nonce);
+
+	iov[1].iov_base = attrs;
+	iov[1].iov_len = ptr - attrs;
+
+	dpp_send_frame(dpp->wdev_id, iov, 2, dpp->current_freq);
+}
+
+static void dpp_write_config(struct dpp_configuration *config)
+{
+	_auto_(l_free) char *ssid = l_malloc(config->ssid_len + 1);
+	_auto_(l_settings_free) struct l_settings *settings = l_settings_new();
+	_auto_(l_free) char *path;
+
+	memcpy(ssid, config->ssid, config->ssid_len);
+	ssid[config->ssid_len] = '\0';
+
+	path = storage_get_network_file_path(SECURITY_PSK, ssid);
+
+	if (l_settings_load_from_file(settings, path)) {
+		/* Remove any existing Security keys */
+		l_settings_remove_group(settings, "Security");
+	}
+
+	if (config->passphrase)
+		l_settings_set_string(settings, "Security", "Passphrase",
+				config->passphrase);
+	else if (config->psk)
+		l_settings_set_string(settings, "Security", "PreSharedKey",
+				config->psk);
+
+	l_debug("Storing credential for '%s(%s)'", ssid,
+						security_to_str(SECURITY_PSK));
+	storage_network_sync(SECURITY_PSK, ssid, settings);
+}
+
+static void dpp_handle_config_frame(const struct mmpdu_header *frame,
+				const void *body, size_t body_len,
+				int rssi, void *user_data)
+{
+	struct dpp_sm *dpp = user_data;
+	const uint8_t *ptr = body;
+	uint16_t status;
+	uint16_t fragmented; /* Fragmented/Comeback delay field */
+	uint8_t adv_protocol_element[] = { 0x6C, 0x08, 0x7F };
+	uint8_t adv_protocol_id[] = { 0xDD, 0x05, 0x50, 0x6F,
+					0x9A, 0x1A, 0x01 };
+	uint16_t query_len;
+	struct dpp_attr_iter iter;
+	enum dpp_attribute_type type;
+	size_t len;
+	const uint8_t *data;
+	const char *json = NULL;
+	size_t json_len = 0;
+	int dstatus = -1;
+	const uint8_t *wrapped = NULL;
+	const uint8_t *e_nonce = NULL;
+	size_t wrapped_len = 0;
+	_auto_(l_free) uint8_t *unwrapped = NULL;
+	struct dpp_configuration *config;
+	uint8_t ad0[] = { 0x00, 0x10, 0x01, 0x00, 0x05 };
+	struct iovec ad = {
+		.iov_base = ad0,
+		.iov_len = 5
+	};
+
+	if (dpp->state != DPP_STATE_CONFIGURING)
+		return;
+
+	ptr += 2;
+
+	/*
+	 * Can a configuration request come from someone other than who you
+	 * authenticated to?
+	 */
+	if (memcmp(dpp->auth_addr, frame->address_2, 6))
+		return;
+
+	if (*ptr++ != dpp->diag_token)
+		return;
+
+	status = l_get_le16(ptr);
+	ptr += 2;
+
+	if (status != 0) {
+		l_debug("Bad configuration status %u", status);
+		return;
+	}
+
+	fragmented = l_get_le16(ptr);
+	ptr += 2;
+
+	/*
+	 * TODO: handle 0x0001 (fragmented), as well as comeback delay.
+	 */
+	if (fragmented != 0) {
+		l_debug("Fragmented messages not currently supported");
+		return;
+	}
+
+	if (memcmp(ptr, adv_protocol_element, sizeof(adv_protocol_element))) {
+		l_debug("Invalid Advertisement protocol element");
+		return;
+	}
+
+	ptr += sizeof(adv_protocol_element);
+
+	if (memcmp(ptr, adv_protocol_id, sizeof(adv_protocol_id))) {
+		l_debug("Invalid Advertisement protocol ID");
+		return;
+	}
+
+	ptr += sizeof(adv_protocol_id);
+
+	query_len = l_get_le16(ptr);
+	ptr += 2;
+
+	dpp_attr_iter_init(&iter, ptr, query_len);
+
+	while (dpp_attr_iter_next(&iter, &type, &len, &data)) {
+		switch (type) {
+		case DPP_ATTR_STATUS:
+			dstatus = l_get_u8(data);
+			break;
+		case DPP_ATTR_WRAPPED_DATA:
+			wrapped = data;
+			wrapped_len = len;
+			break;
+		default:
+			/*
+			 * TODO: CSR Attribute
+			 */
+			break;
+		}
+	}
+
+	if (dstatus != DPP_STATUS_OK || !wrapped) {
+		l_debug("Bad status or missing attributes");
+		return;
+	}
+
+	unwrapped = l_malloc(wrapped_len - 16);
+
+	aes_siv_decrypt(dpp->ke, dpp->key_len, wrapped, wrapped_len, &ad,
+				1, unwrapped);
+
+	wrapped_len -= 16;
+
+	dpp_attr_iter_init(&iter, unwrapped, wrapped_len);
+
+	while (dpp_attr_iter_next(&iter, &type, &len, &data)) {
+		switch (type) {
+		case DPP_ATTR_ENROLLEE_NONCE:
+			if (len != dpp->nonce_len)
+				break;
+
+			if (memcmp(data, dpp->e_nonce, dpp->nonce_len))
+				break;
+
+			e_nonce = data;
+			break;
+		case DPP_ATTR_CONFIGURATION_OBJECT:
+			json = (const char *)data;
+			json_len = len;
+			break;
+		default:
+			break;
+		}
+	}
+
+	if (!json || !e_nonce) {
+		l_debug("No configuration object in response");
+		return;
+	}
+
+	config = dpp_parse_configuration_object(json, json_len);
+	if (!config) {
+		l_error("Configuration object did not parse");
+		return;
+	}
+
+	dpp_write_config(config);
+	/*
+	 * TODO: Depending on the info included in the configuration object a
+	 * limited scan could be issued to get autoconnect to trigger faster.
+	 * In addition this network may already be in past scan results and
+	 * could be joined immediately.
+	 *
+	 * For now just wait for autoconnect.
+	 */
+
+	dpp_configuration_free(config);
+
+	send_config_result(dpp, dpp->auth_addr);
+}
+
 static void dpp_free_auth_data(struct dpp_sm *dpp)
 {
 	if (dpp->proto_public) {
@@ -456,6 +747,8 @@ static void authenticate_confirm(struct dpp_sm *dpp, const uint8_t *from,
 
 	l_debug("Authentication successful");
 
+	dpp_configuration_start(dpp, from);
+
 	return;
 
 auth_confirm_failed:
@@ -739,6 +1032,7 @@ static void dpp_create(struct netdev *netdev)
 	struct l_dbus *dbus = dbus_get_bus();
 	struct dpp_sm *dpp = l_new(struct dpp_sm, 1);
 	uint8_t dpp_prefix[] = { 0x04, 0x09, 0x50, 0x6f, 0x9a, 0x1a, 0x01 };
+	uint8_t dpp_conf_prefix[] = { 0x04, 0x0b };
 
 	dpp->netdev = netdev;
 	dpp->state = DPP_STATE_NOTHING;
@@ -761,6 +1055,9 @@ static void dpp_create(struct netdev *netdev)
 	frame_watch_add(netdev_get_wdev_id(netdev), 0, 0x00d0, dpp_prefix,
 				sizeof(dpp_prefix), dpp_handle_auth_frame,
 				dpp, NULL);
+	frame_watch_add(netdev_get_wdev_id(netdev), 0, 0x00d0, dpp_conf_prefix,
+				sizeof(dpp_conf_prefix),
+				dpp_handle_config_frame, dpp, NULL);
 }
 
 static void dpp_reset(struct dpp_sm *dpp)
-- 
2.31.1