X-Git-Url: https://git.distorted.org.uk/~mdw/secnet/blobdiff_plain/45a1170652384baf744a5e61d576af534c7b8b14..f928f0694ff6b90d5fc429cfe910eaba9fdd3fd0:/netlink.c

diff --git a/netlink.c b/netlink.c
index 5d586d0..97e1af9 100644
--- a/netlink.c
+++ b/netlink.c
@@ -120,7 +120,7 @@ their use.
 #define ICMP_CODE_TTL_EXCEEDED           0
 
 /* Generic IP checksum routine */
-static inline uint16_t ip_csum(uint8_t *iph,int32_t count)
+static inline uint16_t ip_csum(const uint8_t *iph,int32_t count)
 {
     register uint32_t sum=0;
 
@@ -144,7 +144,7 @@ static inline uint16_t ip_csum(uint8_t *iph,int32_t count)
  *      By Jorge Cwik <jorge@laser.satlink.net>, adapted for linux by
  *      Arnt Gulbrandsen.
  */
-static inline uint16_t ip_fast_csum(uint8_t *iph, int32_t ihl) {
+static inline uint16_t ip_fast_csum(const uint8_t *iph, int32_t ihl) {
     uint32_t sum;
 
     __asm__ __volatile__(
@@ -192,7 +192,11 @@ struct iphdr {
     uint8_t    tos;
     uint16_t   tot_len;
     uint16_t   id;
-    uint16_t   frag_off;
+    uint16_t   frag;
+#define IPHDR_FRAG_OFF  ((uint16_t)0x1fff)
+#define IPHDR_FRAG_MORE ((uint16_t)0x2000)
+#define IPHDR_FRAG_DONT ((uint16_t)0x4000)
+/*                 reserved        0x8000 */
     uint8_t    ttl;
     uint8_t    protocol;
     uint16_t   check;
@@ -206,7 +210,7 @@ struct icmphdr {
     uint8_t type;
     uint8_t code;
     uint16_t check;
-    union {
+    union icmpinfofield {
 	uint32_t unused;
 	struct {
 	    uint8_t pointer;
@@ -220,6 +224,8 @@ struct icmphdr {
 	} echo;
     } d;
 };
+
+static const union icmpinfofield icmp_noinfo;
     
 static void netlink_packet_deliver(struct netlink *st,
 				   struct netlink_client *client,
@@ -238,7 +244,7 @@ static struct icmphdr *netlink_icmp_tmpl(struct netlink *st,
     struct icmphdr *h;
 
     BUF_ALLOC(&st->icmp,"netlink_icmp_tmpl");
-    buffer_init(&st->icmp,st->max_start_pad);
+    buffer_init(&st->icmp,calculate_max_start_pad());
     h=buf_append(&st->icmp,sizeof(*h));
 
     h->iph.version=4;
@@ -246,7 +252,7 @@ static struct icmphdr *netlink_icmp_tmpl(struct netlink *st,
     h->iph.tos=0;
     h->iph.tot_len=htons(len+(h->iph.ihl*4)+8);
     h->iph.id=0;
-    h->iph.frag_off=0;
+    h->iph.frag=0;
     h->iph.ttl=255; /* XXX should be configurable */
     h->iph.protocol=1;
     h->iph.saddr=htonl(st->secnet_address);
@@ -293,18 +299,27 @@ static bool_t netlink_icmp_may_reply(struct buffer_if *buf)
     struct icmphdr *icmph;
     uint32_t source;
 
+    if (buf->size < (int)sizeof(struct icmphdr)) return False;
     iph=(struct iphdr *)buf->start;
     icmph=(struct icmphdr *)buf->start;
     if (iph->protocol==1) {
 	switch(icmph->type) {
-	case 3: /* Destination unreachable */
-	case 11: /* Time Exceeded */
-	case 12: /* Parameter Problem */
+	    /* Based on http://www.iana.org/assignments/icmp-parameters/icmp-parameters.xhtml#icmp-parameters-types
+	     * as retrieved Thu, 20 Mar 2014 00:16:44 +0000.
+	     * Deprecated, reserved, unassigned and experimental
+	     * options are treated as not safe to reply to.
+	     */
+	case 0: /* Echo Reply */
+	case 8: /* Echo */
+	case 13: /* Timestamp */
+	case 14: /* Timestamp Reply */
+	    return True;
+	default:
 	    return False;
 	}
     }
     /* How do we spot broadcast destination addresses? */
-    if (ntohs(iph->frag_off)&0x1fff) return False; /* Non-initial fragment */
+    if (ntohs(iph->frag)&IPHDR_FRAG_OFF) return False;
     source=ntohl(iph->saddr);
     if (source==0) return False;
     if ((source&0xff000000)==0x7f000000) return False;
@@ -338,6 +353,7 @@ static bool_t netlink_icmp_may_reply(struct buffer_if *buf)
    */
 static uint16_t netlink_icmp_reply_len(struct buffer_if *buf)
 {
+    if (buf->size < (int)sizeof(struct iphdr)) return 0;
     struct iphdr *iph=(struct iphdr *)buf->start;
     uint16_t hlen,plen;
 
@@ -351,17 +367,17 @@ static uint16_t netlink_icmp_reply_len(struct buffer_if *buf)
 /* client indicates where the packet we're constructing a response to
    comes from. NULL indicates the host. */
 static void netlink_icmp_simple(struct netlink *st, struct buffer_if *buf,
-				struct netlink_client *client,
-				uint8_t type, uint8_t code)
+				uint8_t type, uint8_t code,
+				union icmpinfofield info)
 {
-    struct iphdr *iph=(struct iphdr *)buf->start;
     struct icmphdr *h;
     uint16_t len;
 
     if (netlink_icmp_may_reply(buf)) {
+	struct iphdr *iph=(struct iphdr *)buf->start;
 	len=netlink_icmp_reply_len(buf);
 	h=netlink_icmp_tmpl(st,ntohl(iph->saddr),len);
-	h->type=type; h->code=code;
+	h->type=type; h->code=code; h->d=info;
 	memcpy(buf_append(&st->icmp,len),buf->start,len);
 	netlink_icmp_csum(h);
 	netlink_packet_deliver(st,NULL,&st->icmp);
@@ -389,6 +405,7 @@ static bool_t netlink_check(struct netlink *st, struct buffer_if *buf,
 	return False;					\
     }while(0)
 
+    if (buf->size < (int)sizeof(struct iphdr)) BAD("len %"PRIu32"",buf->size);
     struct iphdr *iph=(struct iphdr *)buf->start;
     int32_t len;
 
@@ -406,6 +423,38 @@ static bool_t netlink_check(struct netlink *st, struct buffer_if *buf,
 #undef BAD
 }
 
+/* Deliver a packet _to_ client; used after we have decided
+ * what to do with it (and just to check that the client has
+ * actually registered a delivery function with us). */
+static void netlink_client_deliver(struct netlink *st,
+				   struct netlink_client *client,
+				   uint32_t source, uint32_t dest,
+				   struct buffer_if *buf)
+{
+    if (!client->deliver) {
+	string_t s,d;
+	s=ipaddr_to_string(source);
+	d=ipaddr_to_string(dest);
+	Message(M_ERR,"%s: dropping %s->%s, client not registered\n",
+		st->name,s,d);
+	free(s); free(d);
+	BUF_FREE(buf);
+	return;
+    }
+    client->deliver(client->dst, buf);
+    client->outcount++;
+}
+
+/* Deliver a packet to the host; used after we have decided that that
+ * is what to do with it. */
+static void netlink_host_deliver(struct netlink *st,
+				 uint32_t source, uint32_t dest,
+				 struct buffer_if *buf)
+{
+    st->deliver_to_host(st->dst,buf);
+    st->outcount++;
+}
+
 /* Deliver a packet. "client" is the _origin_ of the packet, not its
    destination, and is NULL for packets from the host and packets
    generated internally in secnet.  */
@@ -413,6 +462,13 @@ static void netlink_packet_deliver(struct netlink *st,
 				   struct netlink_client *client,
 				   struct buffer_if *buf)
 {
+    if (buf->size < (int)sizeof(struct iphdr)) {
+	Message(M_ERR,"%s: trying to deliver a too-short packet"
+		" from %s!\n",st->name, client?client->name:"(local)");
+	BUF_FREE(buf);
+	return;
+    }
+
     struct iphdr *iph=(struct iphdr *)buf->start;
     uint32_t dest=ntohl(iph->daddr);
     uint32_t source=ntohl(iph->saddr);
@@ -478,8 +534,7 @@ static void netlink_packet_deliver(struct netlink *st,
 	/* The packet's not going down a tunnel.  It might (ought to)
 	   be for the host.   */
 	if (ipset_contains_addr(st->networks,dest)) {
-	    st->deliver_to_host(st->dst,buf);
-	    st->outcount++;
+	    netlink_host_deliver(st,source,dest,buf);
 	    BUF_ASSERT_FREE(buf);
 	} else {
 	    string_t s,d;
@@ -488,8 +543,8 @@ static void netlink_packet_deliver(struct netlink *st,
 	    Message(M_DEBUG,"%s: don't know where to deliver packet "
 		    "(s=%s, d=%s)\n", st->name, s, d);
 	    free(s); free(d);
-	    netlink_icmp_simple(st,buf,client,ICMP_TYPE_UNREACHABLE,
-				ICMP_CODE_NET_UNREACHABLE);
+	    netlink_icmp_simple(st,buf,ICMP_TYPE_UNREACHABLE,
+				ICMP_CODE_NET_UNREACHABLE, icmp_noinfo);
 	    BUF_FREE(buf);
 	}
     } else {
@@ -505,20 +560,21 @@ static void netlink_packet_deliver(struct netlink *st,
 		    st->name,s,d);
 	    free(s); free(d);
 		    
-	    netlink_icmp_simple(st,buf,client,ICMP_TYPE_UNREACHABLE,
-				ICMP_CODE_NET_PROHIBITED);
+	    netlink_icmp_simple(st,buf,ICMP_TYPE_UNREACHABLE,
+				ICMP_CODE_NET_PROHIBITED, icmp_noinfo);
 	    BUF_FREE(buf);
 	} else {
 	    if (best_quality>0) {
 		/* XXX Fragment if required */
-		st->routes[best_match]->deliver(
-		    st->routes[best_match]->dst, buf);
-		st->routes[best_match]->outcount++;
+		netlink_client_deliver(st,st->routes[best_match],
+				       source,dest,buf);
 		BUF_ASSERT_FREE(buf);
 	    } else {
 		/* Generate ICMP destination unreachable */
-		netlink_icmp_simple(st,buf,client,ICMP_TYPE_UNREACHABLE,
-				    ICMP_CODE_NET_UNREACHABLE); /* client==NULL */
+		netlink_icmp_simple(st,buf,
+				    ICMP_TYPE_UNREACHABLE,
+				    ICMP_CODE_NET_UNREACHABLE,
+				    icmp_noinfo);
 		BUF_FREE(buf);
 	    }
 	}
@@ -530,6 +586,7 @@ static void netlink_packet_forward(struct netlink *st,
 				   struct netlink_client *client,
 				   struct buffer_if *buf)
 {
+    if (buf->size < (int)sizeof(struct iphdr)) return;
     struct iphdr *iph=(struct iphdr *)buf->start;
     
     BUF_ASSERT_USED(buf);
@@ -537,8 +594,8 @@ static void netlink_packet_forward(struct netlink *st,
     /* Packet has already been checked */
     if (iph->ttl<=1) {
 	/* Generate ICMP time exceeded */
-	netlink_icmp_simple(st,buf,client,ICMP_TYPE_TIME_EXCEEDED,
-			    ICMP_CODE_TTL_EXCEEDED);
+	netlink_icmp_simple(st,buf,ICMP_TYPE_TIME_EXCEEDED,
+			    ICMP_CODE_TTL_EXCEEDED,icmp_noinfo);
 	BUF_FREE(buf);
 	return;
     }
@@ -559,9 +616,15 @@ static void netlink_packet_local(struct netlink *st,
 
     st->localcount++;
 
+    if (buf->size < (int)sizeof(struct icmphdr)) {
+	Message(M_WARNING,"%s: short packet addressed to secnet; "
+		"ignoring it\n",st->name);
+	BUF_FREE(buf);
+	return;
+    }
     h=(struct icmphdr *)buf->start;
 
-    if ((ntohs(h->iph.frag_off)&0xbfff)!=0) {
+    if ((ntohs(h->iph.frag)&(IPHDR_FRAG_OFF|IPHDR_FRAG_MORE))!=0) {
 	Message(M_WARNING,"%s: fragmented packet addressed to secnet; "
 		"ignoring it\n",st->name);
 	BUF_FREE(buf);
@@ -586,8 +649,8 @@ static void netlink_packet_local(struct netlink *st,
 	Message(M_WARNING,"%s: unknown incoming ICMP\n",st->name);
     } else {
 	/* Send ICMP protocol unreachable */
-	netlink_icmp_simple(st,buf,client,ICMP_TYPE_UNREACHABLE,
-			    ICMP_CODE_PROTOCOL_UNREACHABLE);
+	netlink_icmp_simple(st,buf,ICMP_TYPE_UNREACHABLE,
+			    ICMP_CODE_PROTOCOL_UNREACHABLE,icmp_noinfo);
 	BUF_FREE(buf);
 	return;
     }
@@ -603,15 +666,18 @@ static void netlink_incoming(struct netlink *st, struct netlink_client *client,
     uint32_t source,dest;
     struct iphdr *iph;
     char errmsgbuf[50];
+    const char *sourcedesc=client?client->name:"host";
 
     BUF_ASSERT_USED(buf);
+
     if (!netlink_check(st,buf,errmsgbuf,sizeof(errmsgbuf))) {
 	Message(M_WARNING,"%s: bad IP packet from %s: %s\n",
-		st->name,client?client->name:"host",
+		st->name,sourcedesc,
 		errmsgbuf);
 	BUF_FREE(buf);
 	return;
     }
+    assert(buf->size >= (int)sizeof(struct icmphdr));
     iph=(struct iphdr *)buf->start;
 
     source=ntohl(iph->saddr);
@@ -656,9 +722,9 @@ static void netlink_incoming(struct netlink *st, struct netlink_client *client,
        address validity and generate ICMP, etc. */
     if (st->ptp) {
 	if (client) {
-	    st->deliver_to_host(st->dst,buf);
+	    netlink_host_deliver(st,source,dest,buf);
 	} else {
-	    st->clients->deliver(st->clients->dst,buf);
+	    netlink_client_deliver(st,st->clients,source,dest,buf);
 	}
 	BUF_ASSERT_FREE(buf);
 	return;
@@ -724,7 +790,7 @@ static void netlink_dump_routes(struct netlink *st, bool_t requested)
     if (requested) c=M_WARNING;
     if (st->ptp) {
 	net=ipaddr_to_string(st->secnet_address);
-	Message(c,"%s: point-to-point (remote end is %s); routes:\n",
+	Message(c,"%s: point-to-point (remote end is %s); routes: ",
 		st->name, net);
 	free(net);
 	netlink_output_subnets(st,c,st->clients->subnets);
@@ -808,12 +874,10 @@ static void netlink_inst_set_mtu(void *sst, int32_t new_mtu)
 }
 
 static void netlink_inst_reg(void *sst, netlink_deliver_fn *deliver, 
-			     void *dst, int32_t max_start_pad)
+			     void *dst)
 {
     struct netlink_client *c=sst;
-    struct netlink *st=c->nst;
 
-    if (max_start_pad > st->max_start_pad) st->max_start_pad=max_start_pad;
     c->deliver=deliver;
     c->dst=dst;
 }
@@ -941,7 +1005,6 @@ netlink_deliver_fn *netlink_init(struct netlink *st,
     st->cl.type=CL_PURE;
     st->cl.apply=netlink_inst_apply;
     st->cl.interface=st;
-    st->max_start_pad=0;
     st->clients=NULL;
     st->routes=NULL;
     st->n_clients=0;