(De-)fragment EAP-TLS packets, pass TLS records to upper layer

src/charon/plugins/eap_tls/eap_tls.c

@@ -44,18 +44,241 @@ struct private_eap_tls_t {
 	 * Is this method instance acting as server?
 	 */
 	bool is_server;
+
+	/**
+	 * Allocated input buffer
+	 */
+	chunk_t input;
+
+	/**
+	 * Number of bytes read in input buffer
+	 */
+	size_t inpos;
+
+	/**
+	 * Allocated ouput buffer
+	 */
+	chunk_t output;
+
+	/**
+	 * Number of bytes sent from output buffer
+	 */
+	size_t outpos;
 };
 
+/** Size limit for a single TLS message */
+#define MAX_TLS_MESSAGE_LEN 16192
+/** Size of a EAP-TLS fragment */
+#define EAP_TLS_FRAGMENT_LEN 1014
+
+/**
+ * Flags of an EAP-TLS message
+ */
+typedef enum {
+	EAP_TLS_LENGTH = (1<<7),
+	EAP_TLS_MORE_FRAGS = (1<<6),
+	EAP_TLS_START = (1<<5),
+} eap_tls_flags_t;
+
+/**
+ * EAP-TLS packet format
+ */
+typedef struct __attribute__((packed)) {
+	u_int8_t code;
+	u_int8_t identifier;
+	u_int16_t length;
+	u_int8_t type;
+	u_int8_t flags;
+} eap_tls_packet_t;
+
+/**
+ * TLS record
+ */
+typedef struct __attribute__((packed)) {
+	u_int8_t type;
+	u_int16_t version;
+	u_int16_t length;
+	char data[];
+} tls_record_t;
+
 METHOD(eap_method_t, initiate, status_t,
 	private_eap_tls_t *this, eap_payload_t **out)
 {
+	if (this->is_server)
+	{
+		eap_tls_packet_t pkt = {
+			.type = EAP_TLS,
+			.code = EAP_REQUEST,
+			.flags = EAP_TLS_START,
+		};
+		htoun16(&pkt.length, sizeof(eap_tls_packet_t));
+		/* start with non-zero random identifier */
+		do {
+			pkt.identifier = random();
+		} while (!pkt.identifier);
+
+		*out = eap_payload_create_data(chunk_from_thing(pkt));
+		return NEED_MORE;
+	}
 	return FAILED;
 }
 
+/**
+ * Write received TLS data to the input buffer
+ */
+static bool write_buf(private_eap_tls_t *this, eap_tls_packet_t *pkt)
+{
+	u_int32_t msg_len;
+	u_int16_t pkt_len;
+
+	chunk_free(&this->input);
+	pkt_len = untoh16(&pkt->length);
+
+	if (pkt->flags & EAP_TLS_LENGTH)
+	{	/* first fragment */
+		if (pkt_len < sizeof(eap_tls_packet_t) + 4)
+		{
+			DBG1(DBG_IKE, "EAP-TLS packet too short");
+			return FALSE;
+		}
+		msg_len = untoh32(pkt + 1);
+		this->inpos = pkt_len - sizeof(eap_tls_packet_t) - 4;
+		if (msg_len < this->inpos || msg_len > MAX_TLS_MESSAGE_LEN)
+		{
+			DBG1(DBG_IKE, "invalid EAP-TLS packet length");
+			return FALSE;
+		}
+		this->input = chunk_alloc(msg_len);
+		memcpy(this->input.ptr, ((char*)(pkt + 1)) + 4, this->inpos);
+	}
+	else
+	{	/* non-first fragment */
+		if (pkt_len > this->input.len - this->inpos)
+		{
+			DBG1(DBG_IKE, "EAP-TLS fragment exceeds TLS message length");
+			return FALSE;
+		}
+		memcpy(this->input.ptr + this->inpos, (char*)(pkt + 1),
+			   pkt_len - sizeof(eap_tls_packet_t));
+		this->inpos += pkt_len - sizeof(eap_tls_packet_t);
+	}
+	return TRUE;
+}
+
+/**
+ * Create a eap response from data in the TLS output buffer
+ */
+static eap_payload_t *read_buf(private_eap_tls_t *this, u_int8_t identifier)
+{
+	char buf[EAP_TLS_FRAGMENT_LEN + sizeof(eap_tls_packet_t) + 4], *start;
+	eap_tls_packet_t *pkt = (eap_tls_packet_t*)buf;
+	u_int16_t pkt_len = sizeof(eap_tls_packet_t);
+
+	pkt->code = this->is_server ? EAP_REQUEST : EAP_RESPONSE;
+	pkt->identifier = this->is_server ? identifier + 1 : identifier;
+	pkt->type = EAP_TLS;
+	pkt->flags = 0;
+
+	start = (char*)(pkt + 1);
+	if (this->outpos == 0)
+	{	/* first fragment */
+		pkt->flags = EAP_TLS_LENGTH;
+		pkt_len += 4;
+		start += 4;
+		htoun32(pkt + 1, this->output.len);
+	}
+
+	if (this->output.len - this->outpos > EAP_TLS_FRAGMENT_LEN)
+	{
+		pkt->flags |= EAP_TLS_MORE_FRAGS;
+		pkt_len += EAP_TLS_FRAGMENT_LEN;
+		memcpy(start, this->output.ptr + this->outpos, EAP_TLS_FRAGMENT_LEN);
+		this->outpos += EAP_TLS_FRAGMENT_LEN;
+	}
+	else
+	{
+		pkt_len += this->output.len - this->outpos;
+		memcpy(start, this->output.ptr + this->outpos,
+			   this->output.len - this->outpos);
+		chunk_free(&this->output);
+		this->outpos = 0;
+	}
+	htoun16(&pkt->length, pkt_len);
+	return eap_payload_create_data(chunk_create(buf, pkt_len));
+}
+
+/**
+ * Pass data in input buffer to upper layers, write result to output buffer
+ */
+static status_t process_buf(private_eap_tls_t *this)
+{
+	tls_record_t *record;
+	chunk_t input;
+	u_int16_t len;
+
+	input = this->input;
+	while (input.len > sizeof(tls_record_t))
+	{
+		record = (tls_record_t*)input.ptr;
+		len = untoh16(&record->length);
+		if (len > input.len)
+		{
+			DBG1(DBG_IKE, "TLS record length invalid");
+			break;
+		}
+		/* TODO: pass record to next layer */
+		input = chunk_skip(input, len);
+	}
+	chunk_free(&this->input);
+	this->inpos = 0;
+
+	/* TODO: read records from next layer */
+	return NEED_MORE;
+}
+
 METHOD(eap_method_t, process, status_t,
 	private_eap_tls_t *this, eap_payload_t *in, eap_payload_t **out)
 {
-	return FAILED;
+	eap_tls_packet_t *pkt;
+	chunk_t data;
+	status_t status;
+
+	data = in->get_data(in);
+	pkt = (eap_tls_packet_t*)data.ptr;
+	if (data.len < sizeof(eap_tls_packet_t) ||
+		untoh16(&pkt->length) != data.len)
+	{
+		DBG1(DBG_IKE, "invalid EAP-TLS packet length");
+		return FAILED;
+	}
+	if (!(pkt->flags & EAP_TLS_START))
+	{
+		if (data.len == sizeof(eap_tls_packet_t))
+		{	/* ACK to our fragment, send next */
+			*out = read_buf(this, pkt->identifier);
+			return NEED_MORE;
+		}
+		if (!write_buf(this, pkt))
+		{
+			return FAILED;
+		}
+		if (pkt->flags & EAP_TLS_MORE_FRAGS)
+		{	/* more fragments follow */
+			*out = read_buf(this, pkt->identifier);
+			return NEED_MORE;
+		}
+		else if (this->input.len != this->inpos)
+		{
+			DBG1(DBG_IKE, "defragemented TLS message has invalid length");
+			return FAILED;
+		}
+	}
+	status = process_buf(this);
+	if (status == NEED_MORE)
+	{
+		*out = read_buf(this, pkt->identifier);
+	}
+	return status;
 }
 
 METHOD(eap_method_t, get_type, eap_type_t,
@@ -82,6 +305,10 @@ METHOD(eap_method_t, destroy, void,
 {
 	this->peer->destroy(this->peer);
 	this->server->destroy(this->server);
+
+	free(this->input.ptr);
+	free(this->output.ptr);
+
 	free(this);
 }
 
@@ -106,6 +333,7 @@ static eap_tls_t *eap_tls_create(identification_t *server,
 		.server = server->clone(server),
 		.is_server = is_server,
 	);
+
 	return &this->public;
 }