Check that TLV length is correct when receiving TLVs.

The function, tlv_post_recv, and the functions it calls don't check
the length of the tlv before flipping the byte order of fields. An
attacker (or a really buggy client) can craft a message causing the
byte order of data outside the received message to be flipped.

None of the supported tlvs are large enough to flip bytes outside the
ptp_message struct, which could corrupt the heap. However, it's easy
to mess up the message's refcnt field, leading to memory leaks.

The fix is to check that the tlv length is what is expected when
receiving, and tlv_post_recv needs to return an int to signal when a
tlv is invalid.

Signed-off-by: Geoff Salmon <gsalmon@se-instruments.com>

msg.c

@@ -157,16 +157,18 @@ static int suffix_post_recv(uint8_t *ptr, int len)
 		tlv->type = ntohs(tlv->type);
 		tlv->length = ntohs(tlv->length);
 		if (tlv->length % 2) {
-			break;
+			return -1;
 		}
 		len -= sizeof(struct TLV);
 		ptr += sizeof(struct TLV);
 		if (tlv->length > len) {
-			break;
+			return -1;
 		}
 		len -= tlv->length;
 		ptr += tlv->length;
-		tlv_post_recv(tlv);
+		if (tlv_post_recv(tlv)) {
+			return -1;
+		}
 	}
 	return cnt;
 }
@@ -343,6 +345,9 @@ int msg_post_recv(struct ptp_message *m, int cnt)
 	}
 
 	m->tlv_count = suffix_post_recv(suffix, cnt - pdulen);
+	if (m->tlv_count == -1) {
+		return -1;
+	}
 
 	return 0;
 }

tlv.c

@@ -22,6 +22,9 @@
 #include "port.h"
 #include "tlv.h"
 
+#define TLV_LENGTH_INVALID(tlv, type) \
+	(tlv->length < sizeof(struct type) - sizeof(struct TLV))
+
 uint8_t ieee8021_id[3] = { IEEE_802_1_COMMITTEE };
 
 static void scaled_ns_n2h(ScaledNs *sns)
@@ -38,7 +41,7 @@ static void scaled_ns_h2n(ScaledNs *sns)
 	sns->fractional_nanoseconds = htons(sns->fractional_nanoseconds);
 }
 
-static void mgt_post_recv(struct management_tlv *m)
+static int mgt_post_recv(struct management_tlv *m, uint16_t data_len)
 {
 	struct defaultDS *dds;
 	struct currentDS *cds;
@@ -48,18 +51,24 @@ static void mgt_post_recv(struct management_tlv *m)
 	struct time_status_np *tsn;
 	switch (m->id) {
 	case DEFAULT_DATA_SET:
+		if (data_len != sizeof(struct defaultDS))
+			goto bad_length;
 		dds = (struct defaultDS *) m->data;
 		dds->numberPorts = ntohs(dds->numberPorts);
 		dds->clockQuality.offsetScaledLogVariance =
 			ntohs(dds->clockQuality.offsetScaledLogVariance);
 		break;
 	case CURRENT_DATA_SET:
+		if (data_len != sizeof(struct currentDS))
+			goto bad_length;
 		cds = (struct currentDS *) m->data;
 		cds->stepsRemoved = ntohs(cds->stepsRemoved);
 		cds->offsetFromMaster = net2host64(cds->offsetFromMaster);
 		cds->meanPathDelay = net2host64(cds->meanPathDelay);
 		break;
 	case PARENT_DATA_SET:
+		if (data_len != sizeof(struct parentDS))
+			goto bad_length;
 		pds = (struct parentDS *) m->data;
 		pds->parentPortIdentity.portNumber =
 			ntohs(pds->parentPortIdentity.portNumber);
@@ -71,15 +80,21 @@ static void mgt_post_recv(struct management_tlv *m)
 			ntohs(pds->grandmasterClockQuality.offsetScaledLogVariance);
 		break;
 	case TIME_PROPERTIES_DATA_SET:
+		if (data_len != sizeof(struct timePropertiesDS))
+			goto bad_length;
 		tp = (struct timePropertiesDS *) m->data;
 		tp->currentUtcOffset = ntohs(tp->currentUtcOffset);
 		break;
 	case PORT_DATA_SET:
+		if (data_len != sizeof(struct portDS))
+			goto bad_length;
 		p = (struct portDS *) m->data;
 		p->portIdentity.portNumber = ntohs(p->portIdentity.portNumber);
 		p->peerMeanPathDelay = net2host64(p->peerMeanPathDelay);
 		break;
 	case TIME_STATUS_NP:
+		if (data_len != sizeof(struct time_status_np))
+			goto bad_length;
 		tsn = (struct time_status_np *) m->data;
 		tsn->master_offset = net2host64(tsn->master_offset);
 		tsn->ingress_time = net2host64(tsn->ingress_time);
@@ -90,6 +105,9 @@ static void mgt_post_recv(struct management_tlv *m)
 		tsn->gmPresent = ntohl(tsn->gmPresent);
 		break;
 	}
+	return 0;
+bad_length:
+	return -1;
 }
 
 static void mgt_pre_send(struct management_tlv *m)
@@ -146,16 +164,18 @@ static void mgt_pre_send(struct management_tlv *m)
 	}
 }
 
-static void org_post_recv(struct organization_tlv *org)
+static int org_post_recv(struct organization_tlv *org)
 {
 	struct follow_up_info_tlv *f;
 
 	if (0 == memcmp(org->id, ieee8021_id, sizeof(ieee8021_id))) {
 		if (org->subtype[0] || org->subtype[1]) {
-			return;
+			return 0;
 		}
 		switch (org->subtype[2]) {
 		case 1:
+			if (org->length + sizeof(struct TLV) != sizeof(struct follow_up_info_tlv))
+				goto bad_length;
 			f = (struct follow_up_info_tlv *) org;
 			f->cumulativeScaledRateOffset = ntohl(f->cumulativeScaledRateOffset);
 			f->gmTimeBaseIndicator = ntohs(f->gmTimeBaseIndicator);
@@ -164,6 +184,9 @@ static void org_post_recv(struct organization_tlv *org)
 			break;
 		}
 	}
+	return 0;
+bad_length:
+	return -1;
 }
 
 static void org_pre_send(struct organization_tlv *org)
@@ -186,25 +209,33 @@ static void org_pre_send(struct organization_tlv *org)
 	}
 }
 
-void tlv_post_recv(struct TLV *tlv)
+int tlv_post_recv(struct TLV *tlv)
 {
+	int result = 0;
 	struct management_tlv *mgt;
 	struct management_error_status *mes;
 	struct path_trace_tlv *ptt;
 
 	switch (tlv->type) {
 	case TLV_MANAGEMENT:
+		if (TLV_LENGTH_INVALID(tlv, management_tlv))
+			goto bad_length;
 		mgt = (struct management_tlv *) tlv;
 		mgt->id = ntohs(mgt->id);
-		mgt_post_recv(mgt);
+		if (tlv->length > sizeof(mgt->id))
+			result = mgt_post_recv(mgt, tlv->length - sizeof(mgt->id));
 		break;
 	case TLV_MANAGEMENT_ERROR_STATUS:
+		if (TLV_LENGTH_INVALID(tlv, management_error_status))
+			goto bad_length;
 		mes = (struct management_error_status *) tlv;
 		mes->error = ntohs(mes->error);
 		mes->id = ntohs(mes->id);
 		break;
 	case TLV_ORGANIZATION_EXTENSION:
-		org_post_recv((struct organization_tlv *) tlv);
+		if (TLV_LENGTH_INVALID(tlv, organization_tlv))
+			goto bad_length;
+		result = org_post_recv((struct organization_tlv *) tlv);
 		break;
 	case TLV_REQUEST_UNICAST_TRANSMISSION:
 	case TLV_GRANT_UNICAST_TRANSMISSION:
@@ -225,6 +256,9 @@ void tlv_post_recv(struct TLV *tlv)
 	default:
 		break;
 	}
+	return result;
+bad_length:
+	return -1;
 }
 
 void tlv_pre_send(struct TLV *tlv)

tlv.h

@@ -180,8 +180,9 @@ struct time_status_np {
 /**
  * Converts recognized value sub-fields into host byte order.
  * @param tlv Pointer to a Type Length Value field.
+ * @return Zero if successful, otherwise non-zero
  */
-void tlv_post_recv(struct TLV *tlv);
+int tlv_post_recv(struct TLV *tlv);
 
 /**
  * Converts recognized value sub-fields into network byte order.