module-raop: Add transient HomeKit pairing

src/modules/module-raop-discover.c

@@ -64,7 +64,7 @@
  *                          #raop.domain = ""
  *                          #raop.device = ""
  *                          #raop.transport = "udp" | "tcp"
- *                          #raop.encryption.type = "RSA" | "auth_setup" | "none"
+ *                          #raop.encryption.type = "RSA" | "auth_setup" | "pair_setup" | "none"
  *                          #raop.audio.codec = "PCM" | "ALAC" | "AAC" | "AAC-ELD"
  *                          #audio.channels = 2
  *                          #audio.format = "S16" | "S24" | "S32"
@@ -105,12 +105,14 @@ PW_LOG_TOPIC_STATIC(mod_topic, "mod." NAME);
 
 static const struct spa_dict_item module_props[] = {
 	{ PW_KEY_MODULE_AUTHOR, "Wim Taymans <wim.taymans@gmail.com>" },
-	{ PW_KEY_MODULE_DESCRIPTION, "Discover remote streams" },
+	{ PW_KEY_MODULE_DESCRIPTION, "Discover remote speakers" },
 	{ PW_KEY_MODULE_USAGE, MODULE_USAGE },
 	{ PW_KEY_MODULE_VERSION, PACKAGE_VERSION },
 };
 
-#define SERVICE_TYPE_SINK "_raop._tcp"
+#define SERVICE_TYPE_RAOP "_raop._tcp"
+#define SERVICE_TYPE_AP "_airplay._tcp"
+
 
 struct impl {
 	struct pw_context *context;
@@ -122,7 +124,8 @@ struct impl {
 
 	AvahiPoll *avahi_poll;
 	AvahiClient *client;
-	AvahiServiceBrowser *sink_browser;
+	AvahiServiceBrowser *sink_browser_raop;
+	AvahiServiceBrowser *sink_browser_ap;
 
 	struct spa_list tunnel_list;
 };
@@ -182,8 +185,10 @@ static void impl_free(struct impl *impl)
 	spa_list_consume(t, &impl->tunnel_list, link)
 		free_tunnel(t);
 
-	if (impl->sink_browser)
-		avahi_service_browser_free(impl->sink_browser);
+	if (impl->sink_browser_raop)
+		avahi_service_browser_free(impl->sink_browser_raop);
+	if (impl->sink_browser_ap)
+		avahi_service_browser_free(impl->sink_browser_ap);
 	if (impl->client)
 		avahi_client_free(impl->client);
 	if (impl->avahi_poll)
@@ -215,7 +220,30 @@ static bool str_in_list(const char *haystack, const char *delimiters, const char
 	return false;
 }
 
-static void pw_properties_from_avahi_string(const char *key, const char *value,
+static void pw_properties_from_ap_txt(const char *key, const char *value,
+		struct pw_properties *props)
+{
+	if (spa_streq(key, "deviceid")) {
+		pw_properties_set(props, "raop.device", value);
+	}
+	else if (spa_streq(key, "features")) {
+		pw_properties_set(props, "raop.features", value);
+	}
+	else if (spa_streq(key, "flags")) {
+		pw_properties_set(props, "raop.flags", value);
+	}
+	else if (spa_streq(key, "pk")) {
+		pw_properties_set(props, "raop.pk", value);
+	}
+	else if (spa_streq(key, "pi")) {
+		pw_properties_set(props, "raop.pi", value);
+	}
+	else if (spa_streq(key, "psi")) {
+		pw_properties_set(props, "raop.psi", value);
+	}
+}
+
+static void pw_properties_from_raop_txt(const char *key, const char *value,
 		struct pw_properties *props)
 {
 	if (spa_streq(key, "device")) {
@@ -393,6 +421,37 @@ static void resolver_cb(AvahiServiceResolver *r, AvahiIfIndex interface, AvahiPr
 		goto done;
 	}
 
+	pw_log_info("mdns service type: %s", type);
+	if (strcmp(type, SERVICE_TYPE_AP) == 0) {
+		for (l = txt; l; l = l->next) {
+			char *key, *value;
+
+			if (avahi_string_list_get_pair(l, &key, &value, NULL) != 0)
+				break;
+
+			pw_properties_from_ap_txt(key, value, props);
+			avahi_free(key);
+			avahi_free(value);
+		}
+
+		// TODO lorbus
+		// if !feature audio goto done  
+		pw_properties_set(props, "raop.encryption.type", "pair_setup");
+		pw_properties_set(props, "raop.transport", "udp");
+
+	} else {
+		for (l = txt; l; l = l->next) {
+			char *key, *value;
+
+			if (avahi_string_list_get_pair(l, &key, &value, NULL) != 0)
+				break;
+
+			pw_properties_from_raop_txt(key, value, props);
+			avahi_free(key);
+			avahi_free(value);
+		}
+	}
+
 	avahi_address_snprint(at, sizeof(at), a);
 	ipv = protocol == AVAHI_PROTO_INET ? 4 : 6;
 	pw_properties_setf(props, "raop.ip", "%s", at);
@@ -402,17 +461,6 @@ static void resolver_cb(AvahiServiceResolver *r, AvahiIfIndex interface, AvahiPr
 	pw_properties_setf(props, "raop.hostname", "%s", host_name);
 	pw_properties_setf(props, "raop.domain", "%s", domain);
 
-	for (l = txt; l; l = l->next) {
-		char *key, *value;
-
-		if (avahi_string_list_get_pair(l, &key, &value, NULL) != 0)
-			break;
-
-		pw_properties_from_avahi_string(key, value, props);
-		avahi_free(key);
-		avahi_free(value);
-	}
-
 	if ((str = pw_properties_get(impl->properties, "raop.latency.ms")) != NULL)
 		pw_properties_set(props, "raop.latency.ms", str);
 
@@ -502,9 +550,13 @@ static void client_callback(AvahiClient *c, AvahiClientState state, void *userda
 	case AVAHI_CLIENT_S_REGISTERING:
 	case AVAHI_CLIENT_S_RUNNING:
 	case AVAHI_CLIENT_S_COLLISION:
-		if (impl->sink_browser == NULL)
-			impl->sink_browser = make_browser(impl, SERVICE_TYPE_SINK);
-		if (impl->sink_browser == NULL)
+		if (impl->sink_browser_raop == NULL)
+			impl->sink_browser_raop = make_browser(impl, SERVICE_TYPE_RAOP);
+		if (impl->sink_browser_raop == NULL)
+			goto error;
+		if (impl->sink_browser_ap == NULL)
+			impl->sink_browser_ap = make_browser(impl, SERVICE_TYPE_AP);
+		if (impl->sink_browser_ap == NULL)
 			goto error;
 		break;
 	case AVAHI_CLIENT_FAILURE:
@@ -513,9 +565,13 @@ static void client_callback(AvahiClient *c, AvahiClientState state, void *userda
 
 		SPA_FALLTHROUGH;
 	case AVAHI_CLIENT_CONNECTING:
-		if (impl->sink_browser) {
-			avahi_service_browser_free(impl->sink_browser);
-			impl->sink_browser = NULL;
+		if (impl->sink_browser_raop) {
+			avahi_service_browser_free(impl->sink_browser_raop);
+			impl->sink_browser_raop = NULL;
+		}
+		if (impl->sink_browser_ap) {
+			avahi_service_browser_free(impl->sink_browser_ap);
+			impl->sink_browser_ap = NULL;
 		}
 		break;
 	default:

src/modules/module-raop-sink.c

@@ -2,6 +2,8 @@
 /* SPDX-FileCopyrightText: Copyright © 2021 Wim Taymans */
 /* SPDX-License-Identifier: MIT */
 
+#include <ctype.h>
+#include <assert.h>
 #include <string.h>
 #include <stdio.h>
 #include <errno.h>
@@ -26,6 +28,7 @@
 #include <openssl/engine.h>
 #include <openssl/aes.h>
 #include <openssl/md5.h>
+#include <openssl/evp.h>
 
 #include "config.h"
 
@@ -44,6 +47,8 @@
 #include <pipewire/i18n.h>
 
 #include "module-raop/rtsp-client.h"
+#include "module-raop/srp.h"
+#include "module-raop/tlv.h"
 
 /** \page page_module_raop_sink PipeWire Module: AirPlay Sink
  *
@@ -136,9 +141,16 @@ PW_LOG_TOPIC_STATIC(mod_topic, "mod." NAME);
 #define MD5_DIGEST_LENGTH	16
 #endif
 #define MD5_HASH_LENGTH (2*MD5_DIGEST_LENGTH)
+#ifndef SHA512_DIGEST_LENGTH
+#define SHA512_DIGEST_LENGTH 64
+#endif
 
 #define DEFAULT_USER_AGENT	"iTunes/11.0.4 (Windows; N)"
 #define DEFAULT_USER_NAME	"iTunes"
+#define AP_USER_AGENT  		"AirPlay/381.13"
+#define AP_USER_NAME		"AirPlay"
+#define AP_REQUEST_BUFSIZE	4096
+#define AP_SRP_USER_NAME	"Pair-Setup"
 
 #define MAX_PORT_RETRY	128
 
@@ -171,7 +183,7 @@ PW_LOG_TOPIC_STATIC(mod_topic, "mod." NAME);
 
 static const struct spa_dict_item module_props[] = {
 	{ PW_KEY_MODULE_AUTHOR, "Wim Taymans <wim.taymans@gmail.com>" },
-	{ PW_KEY_MODULE_DESCRIPTION, "An RAOP audio sink" },
+	{ PW_KEY_MODULE_DESCRIPTION, "An AirPlay audio sink" },
 	{ PW_KEY_MODULE_USAGE, MODULE_USAGE },
 	{ PW_KEY_MODULE_VERSION, PACKAGE_VERSION },
 };
@@ -183,7 +195,8 @@ enum {
 enum {
 	CRYPTO_NONE,
 	CRYPTO_RSA,
-	CRYPTO_AUTH_SETUP,
+	CRYPTO_AUTH_SETUP = 4,
+	CRYPTO_PAIR_TRANSIENT = 8,
 };
 enum {
 	CODEC_PCM,
@@ -232,6 +245,22 @@ struct impl {
 	uint8_t aes_iv[AES_CHUNK_SIZE];  /* Initialization vector for cbc */
 	EVP_CIPHER_CTX *ctx;
 
+	struct SRPUser *srp_user;
+	uint8_t public_key[32];
+	uint8_t private_key[64];
+	const uint8_t *pkA;
+	int pkA_len;
+	uint8_t *pkB;
+	uint64_t pkB_len;
+	const uint8_t *M1;
+	int M1_len;
+	uint8_t *M2;
+	int M2_len;
+	uint8_t *salt;
+	uint64_t salt_len;
+	uint8_t shared_secret[64];
+	size_t shared_secret_len; // Will be 32 (normal) or 64 (transient)
+
 	uint16_t control_port;
 	int control_fd;
 	struct spa_source *control_source;
@@ -1384,6 +1413,290 @@ static int rtsp_do_raop_auth(struct impl *impl, const struct spa_dict *headers)
 	return rtsp_send(impl, "OPTIONS", NULL, NULL, rtsp_raop_auth_reply);
 }
 
+static tlv_values_t * tlv_message_process(const uint8_t *data, size_t data_len)
+{
+	tlv_values_t *response;
+	tlv_t *error;
+	int ret;
+
+	pw_log_debug("tlv: processing tlv message");
+
+	response = tlv_new();
+	if (!response) {
+		pw_log_error("tlv: Out of memory");
+		return NULL;
+	}
+
+	ret = tlv_parse(data, data_len, response);
+	if (ret < 0) {
+		pw_log_error("tlv: Could not parse TLV");
+		goto error;
+	}
+	
+  	for (tlv_t *t=response->head; t; t=t->next) {
+		pw_log_info("tlv: parsed type %d value (%zu bytes)", t->type, t->size);
+	}
+
+	error = tlv_get_value(response, AP2_TLVType_Error);
+	if (error) {
+		if (error->value[0] == AP2_TLVError_Authentication)
+			pw_log_error("tlv: Device returned an authentication failure");
+		else if (error->value[0] == AP2_TLVError_Backoff)
+			pw_log_error("tlv: Device told us to back off pairing attempts");
+		else if (error->value[0] == AP2_TLVError_MaxPeers)
+			pw_log_error("tlv: Max peers trying to connect to device");
+	  	else if (error->value[0] == AP2_TLVError_MaxTries)
+			pw_log_error("tlv: Max pairing attempts reached");
+	  	else if (error->value[0] == AP2_TLVError_Unavailable)
+			pw_log_error("tlv: Device is unavailable at this time");
+		else
+			pw_log_error("tlv: Device is busy/returned unknown error");
+
+		goto error;
+	}
+
+  return response;
+
+error:
+	tlv_free(response);
+	return NULL;
+}
+
+static int rtsp_ap2_pair_setup2_reply(void *data, int status, const struct spa_dict *headers, const struct pw_array *content)
+{
+	struct impl *impl = data;
+	tlv_values_t *response;
+	tlv_t *proof;
+	const uint8_t *session_key;
+	int session_key_len;
+	uint32_t content_length;
+	const char *str;
+
+	pw_log_info("pair-setup (req 2) status: %d", status);
+
+	if ((str = spa_dict_lookup(headers, "Content-Length")) == NULL) {
+		pw_log_error("pair-setup (req 2) res: Missing Content-Length");
+		return -1;
+	}
+	
+	if (!spa_atou32(str, &content_length, 0)) {
+		pw_log_error("pair-setup (req 2) res: Could not read Content-Length");
+		return -1;
+	}
+	pw_log_debug("pair-setup (req 2) res: Content-Length: %s", str);
+
+	response = tlv_message_process((const uint8_t *)content->data, (size_t)content_length);
+	if (!response) {
+		pw_log_error("pair-setup (req 2) res: Received an error");
+		return -1;
+	}
+
+	proof = tlv_get_value(response, AP2_TLVType_Proof);
+	if (!proof || proof->size != SHA512_DIGEST_LENGTH) {
+		pw_log_error("pair-setup (req 2) res: Missing or invalid proof");
+		goto error;
+	}
+
+	impl->M2_len = proof->size;
+  	impl->M2 = malloc(impl->M2_len);
+  	memcpy(impl->M2, proof->value, impl->M2_len);
+
+	// Check M2
+	srp_user_verify_session(impl->srp_user, (const unsigned char *)impl->M2);
+	if (!srp_user_is_authenticated(impl->srp_user)) {
+		pw_log_error("pair-setup (req 2) res: Server authentication failed");
+		goto error;
+	}
+
+	session_key = srp_user_get_session_key(impl->srp_user, &session_key_len);
+	if (!session_key) {
+		pw_log_error("pair-setup (req 2) res: Could not compute session key");
+		goto error;
+	}
+
+	if (sizeof(impl->shared_secret) < (unsigned long int) session_key_len) {
+		pw_log_error("pair-setup (req 2) res: invalid session key");
+		goto error;
+	}
+
+	memcpy(impl->shared_secret, session_key, session_key_len);
+	impl->shared_secret_len = session_key_len;
+
+	pw_log_info("received shared secret");
+
+	tlv_free(response);
+	// TODO
+	pw_properties_set(impl->headers, "X-Apple-HKP", NULL);
+
+	//return rtsp_do_setup(impl);
+	return 0;
+
+error:
+	tlv_free(response);
+	return -1;
+}
+
+static int rtsp_do_ap2_pair_setup2(struct impl *impl)
+{
+	tlv_values_t *request;
+	uint8_t *data;
+	size_t data_len = AP_REQUEST_BUFSIZE;
+	const char *auth_username = NULL;
+	int ret;
+	// TLV Pairing Message State
+	uint8_t state = 0x03;
+
+	data = malloc(data_len);
+	request = tlv_new();
+
+	// Calculate A
+	srp_user_start_authentication(impl->srp_user, &auth_username, &impl->pkA, &impl->pkA_len);
+
+	// Calculate M1 (client proof)
+	srp_user_process_challenge(impl->srp_user, impl->salt, impl->salt_len, impl->pkB, impl->pkB_len, &impl->M1, &impl->M1_len);
+
+	tlv_add_value(request, AP2_TLVType_State, &state, sizeof(state));
+	tlv_add_value(request, AP2_TLVType_PublicKey, impl->pkA, impl->pkA_len);
+	tlv_add_value(request, AP2_TLVType_Proof, impl->M1, impl->M1_len);
+
+	ret = tlv_format(request, data, &data_len);
+	if (ret < 0) {
+		pw_log_error("pair-setup 2: tlv_format returned an error");
+		goto error;
+	}
+
+  	for (tlv_t *t=request->head; t; t=t->next) {
+		pw_log_info("pair-setup 2: sending TLV type %d (bytes: %zu)", t->type, t->size);
+	}
+
+	tlv_free(request);
+
+   	return pw_rtsp_client_url_send(impl->rtsp, "/pair-setup", "POST", &impl->headers->dict,
+				"application/octet-stream", data, data_len,
+				rtsp_ap2_pair_setup2_reply, impl);
+
+error:
+	tlv_free(request);
+	free(data);
+	return -1;
+}
+
+static int rtsp_ap2_pair_setup1_reply(void *data, int status, const struct spa_dict *headers, const struct pw_array *content)
+{
+	struct impl *impl = data;
+	uint32_t content_length;
+	const char *len_str;
+	tlv_values_t *response;
+	tlv_t *pk;
+	tlv_t *salt;
+
+	pw_log_info("pair-setup (req 1) status: %d", status);
+
+	if ((len_str = spa_dict_lookup(headers, "Content-Length")) == NULL) {
+		pw_log_error("pair-setup (req 1) res: Missing Content-Length header");
+		return -1;
+	}
+	
+	if (!spa_atou32(len_str, &content_length, 0)) {
+		pw_log_error("pair-setup (req 1) res: Could not read Content-Length header");
+		return -1;
+	}
+	pw_log_info("pair-setup (req 1) content len: %d", content_length);
+
+	response = tlv_message_process((const uint8_t *)content->data, (size_t)content_length);
+	if (!response) {
+		pw_log_error("pair-setup (req 1) res: message process error");
+		return -1;
+	}
+
+	pk = tlv_get_value(response, AP2_TLVType_PublicKey);
+	if (!pk) {
+		pw_log_error("pair-setup (req 1) res: missing public key");
+		goto error;
+	}
+	if (pk->size > (long unsigned int) get_N_len(SRP_NG_3072)) {
+		pw_log_error("pair-setup (req 1) res: invalid public key");
+		goto error;
+	}
+
+	salt = tlv_get_value(response, AP2_TLVType_Salt);
+	if (!salt) {
+		pw_log_error("pair-setup (req 1) res: missing salt");
+		goto error;
+	}
+	if (salt->size != 16) {
+		pw_log_error("pair-setup (req 1) res: invalid salt");
+		goto error;
+	}
+
+	impl->pkB_len = pk->size;
+	impl->pkB = malloc(impl->pkB_len);
+	memcpy(impl->pkB, pk->value, impl->pkB_len);
+
+	impl->salt_len = salt->size;
+	impl->salt = malloc(impl->salt_len);
+	memcpy(impl->salt, salt->value, impl->salt_len);
+
+	tlv_free(response);
+
+	return rtsp_do_ap2_pair_setup2(impl);
+
+error:
+	tlv_free(response);
+	return -1;
+}
+
+static int rtsp_do_ap2_pair_setup1(struct impl *impl)
+{
+	tlv_values_t *request;
+	uint8_t *data;
+	size_t data_len;
+	// TLV Pairing Method: Pair Setup
+	uint8_t method = 0x00;
+	// TLV Pairing Flags: Transient
+	uint8_t flags = 0x10;
+	// TLV Pairing Message State
+	uint8_t state = 0x01;
+	char *pin = "3939";
+	int ret;
+
+	data_len = AP_REQUEST_BUFSIZE;
+	data = malloc(data_len);
+	request = tlv_new();
+
+  	impl->srp_user = srp_user_new(SRP_SHA512, SRP_NG_3072, AP_SRP_USER_NAME, (unsigned char *)pin, strlen(pin), 0, 0);
+  	if (!impl->srp_user) {
+		pw_log_error("pair-setup 1: SRP user creation failed");
+		goto error;
+	}
+
+   	tlv_add_value(request, AP2_TLVType_State, &state, sizeof(state));
+  	tlv_add_value(request, AP2_TLVType_Method, &method, sizeof(method));
+	tlv_add_value(request, AP2_TLVType_Flags, &flags, sizeof(flags));
+
+  	ret = tlv_format(request, data, &data_len);
+  	if (ret < 0) {
+		pw_log_error("pair-setup 1: tlv_format returned an error");
+		goto error;
+	}
+
+  	for (tlv_t *t=request->head; t; t=t->next) {
+		pw_log_info("pair-setup 1: sending TLV type %d value (%zu bytes)", t->type, t->size);
+	}
+
+  	tlv_free(request);
+
+	pw_properties_set(impl->headers, "X-Apple-HKP", "4");
+
+	return pw_rtsp_client_url_send(impl->rtsp, "/pair-setup", "POST", &impl->headers->dict,
+				"application/octet-stream", (unsigned char *)data, data_len,
+				rtsp_ap2_pair_setup1_reply, impl);
+error:
+	tlv_free(request);
+	free(data);
+	return -1;
+}
+
 static int rtsp_raop_options_reply(void *data, int status, const struct spa_dict *headers, const struct pw_array *content)
 {
 	struct impl *impl = data;
@@ -1409,30 +1722,51 @@ static void rtsp_connected(void *data)
 {
 	struct impl *impl = data;
 	uint32_t sci[2];
-	uint8_t rac[16];
-	char sac[16*4];
-	int res;
 
 	pw_log_info("connected");
 
 	impl->connected = true;
 
-	if ((res = pw_getrandom(sci, sizeof(sci), 0)) < 0 ||
-	    (res = pw_getrandom(rac, sizeof(rac), 0)) < 0) {
-		pw_log_error("error generating random data: %s", spa_strerror(res));
+	// TODO: Do a GET /info first
+
+	if (pw_getrandom(sci, sizeof(sci), 0) < 0) {
+		pw_log_error("error generating random data: %m");
 		return;
 	}
 
 	pw_properties_setf(impl->headers, "Client-Instance",
-			"%08x%08x", sci[0], sci[1]);
+			"%08X%08X", sci[0], sci[1]);
 
-	base64_encode(rac, sizeof(rac), sac, '\0');
-	pw_properties_set(impl->headers, "Apple-Challenge", sac);
+	pw_properties_setf(impl->headers, "DACP-ID",
+			"%08X%08X", sci[0], sci[1]);
 
-	pw_properties_set(impl->headers, "User-Agent", DEFAULT_USER_AGENT);
+	switch (impl->encryption) {
+	case CRYPTO_PAIR_TRANSIENT:
+		pw_properties_set(impl->headers, "User-Agent", AP_USER_AGENT);
 
-	pw_rtsp_client_send(impl->rtsp, "OPTIONS", &impl->headers->dict,
+		rtsp_do_ap2_pair_setup1(impl);
+		break;
+	default:
+		uint8_t rac[16];
+		char sac[16*4];
+
+		if (pw_getrandom(rac, sizeof(rac), 0) < 0) {
+			pw_log_error("error generating random data: %m");
+			return;
+		}
+
+		base64_encode(rac, sizeof(rac), sac, '\0');
+		pw_properties_set(impl->headers, "Apple-Challenge", sac);
+	
+		pw_properties_set(impl->headers, "User-Agent", DEFAULT_USER_AGENT);
+
+		pw_rtsp_client_send(impl->rtsp, "OPTIONS", &impl->headers->dict,
 			NULL, NULL, rtsp_raop_options_reply, impl);
+
+		break;
+	}
+
+	return;
 }
 
 static void connection_cleanup(struct impl *impl)
@@ -1888,6 +2222,9 @@ int pipewire__module_init(struct pw_impl_module *module, const char *args)
 		pw_log_error( "can't create cipher context: %m");
 		goto error;
 	}
+
+	impl->srp_user = NULL;
+
 	if (args == NULL)
 		args = "";
 
@@ -1992,6 +2329,8 @@ int pipewire__module_init(struct pw_impl_module *module, const char *args)
 		impl->encryption = CRYPTO_RSA;
 	else if (spa_streq(str, "auth_setup"))
 		impl->encryption = CRYPTO_AUTH_SETUP;
+	else if (spa_streq(str, "pair_setup"))
+		impl->encryption = CRYPTO_PAIR_TRANSIENT;
 	else {
 		pw_log_error( "can't handle encryption type %s", str);
 		res = -EINVAL;