X-Git-Url: http://www.chiark.greenend.org.uk/ucgi/~ian/git?p=secnet.git;a=blobdiff_plain;f=udp.c;h=98da30d6f66f391ac8944a4e2a835dacf257572e;hp=f05596202d8e0f5d7a59d6205b60cb7b8b4ac89a;hb=67be07ed798122634472d467f42727f2e92a8f40;hpb=8689b3a94c043f04e334a7b181a7250ad5940616

diff --git a/udp.c b/udp.c
index f055962..98da30d 100644
--- a/udp.c
+++ b/udp.c
@@ -5,10 +5,6 @@
  * optionally bind to a particular local IP address (not implemented
  * yet).
  *
- * Sites register an interest in local port numbers for receiving
- * packets, and can also send packets. We don't care about the source
- * port number for sending packets. 
- *
  * Packets are offered to registered receivers in turn. Once one
  * accepts it, it isn't offered to any more. */
 
@@ -19,7 +15,14 @@
 #include <string.h>
 #include <errno.h>
 #include <sys/socket.h>
+#include <sys/wait.h>
+#include <netinet/in.h>
+#include <arpa/inet.h>
 #include "util.h"
+#include "magic.h"
+#include "unaligned.h"
+#include "ipaddr.h"
+#include "magic.h"
 
 static beforepoll_fn udp_beforepoll;
 static afterpoll_fn udp_afterpoll;
@@ -27,69 +30,134 @@ static comm_request_notify_fn request_notify;
 static comm_release_notify_fn release_notify;
 static comm_sendmsg_fn udp_sendmsg;
 
-/* The UDP module exports a pure closure which can be used to construct a
- * UDP send/receive module. Arguments:
- */
-
-struct notify_list {
+struct comm_notify_entry {
     comm_notify_fn *fn;
     void *state;
-    struct notify_list *next;
+    LIST_ENTRY(comm_notify_entry) entry;
+};
+LIST_HEAD(comm_notify_list, comm_notify_entry) notify;
+
+#define MAX_SOCKETS 3 /* 2 ought to do really */
+
+struct udpsock {
+    union iaddr addr;
+    int fd;
 };
 
 struct udp {
     closure_t cl;
     struct comm_if ops;
     struct cloc loc;
-    int fd;
+    int n_socks;
+    struct udpsock socks[MAX_SOCKETS];
+    string_t authbind;
     struct buffer_if *rbuf;
-    struct notify_list *notify;
+    struct comm_notify_list notify;
+    bool_t use_proxy;
+    union iaddr proxy;
 };
 
+/*
+ * Re comm_addr.ix: This field allows us to note in the comm_addr
+ * which socket an incoming packet was received on.  This is required
+ * for conveniently logging the actual source of a packet.  But the ix
+ * does not formally form part of the address: it is not used when
+ * sending, nor when comparing two comm_addrs.
+ *
+ * The special value -1 means that the comm_addr was constructed by
+ * another module in secnet (eg the resolver), rather than being a
+ * description of the source of an incoming packet.
+ */
+
+static const char *addr_to_string(void *commst, const struct comm_addr *ca) {
+    struct udp *st=commst;
+    static char sbuf[100];
+    int ix=ca->ix>=0 ? ca->ix : 0;
+
+    assert(ix>=0 && ix<st->n_socks);
+    snprintf(sbuf, sizeof(sbuf), "udp:%s%s-%s",
+	     iaddr_to_string(&st->socks[ix].addr),
+	     ca->ix<0 ? "&" : "",
+	     iaddr_to_string(&ca->ia));
+    return sbuf;
+}
+
 static int udp_beforepoll(void *state, struct pollfd *fds, int *nfds_io,
-			  int *timeout_io, const struct timeval *tv,
-			  uint64_t *now)
+			  int *timeout_io)
 {
+    int i;
     struct udp *st=state;
-    if (*nfds_io<1) {
-	*nfds_io=1;
-	return ERANGE;
+    BEFOREPOLL_WANT_FDS(st->n_socks);
+    for (i=0; i<st->n_socks; i++) {
+	fds[i].fd=st->socks[i].fd;
+	fds[i].events=POLLIN;
     }
-    *nfds_io=1;
-    fds->fd=st->fd;
-    fds->events=POLLIN;
     return 0;
 }
 
-static void udp_afterpoll(void *state, struct pollfd *fds, int nfds,
-			  const struct timeval *tv, uint64_t *now)
+static void udp_afterpoll(void *state, struct pollfd *fds, int nfds)
 {
     struct udp *st=state;
-    struct sockaddr_in from;
-    int fromlen;
-    struct notify_list *n;
+    union iaddr from;
+    socklen_t fromlen;
+    struct comm_notify_entry *n;
     bool_t done;
     int rv;
+    int i;
 
-    if (nfds && (fds->revents & POLLIN)) {
+    for (i=0; i<st->n_socks; i++) {
+	if (i>=nfds) continue;
+	if (!(fds[i].revents & POLLIN)) continue;
+	assert(fds[i].fd == st->socks[i].fd);
+	int fd=st->socks[i].fd;
 	do {
 	    fromlen=sizeof(from);
 	    BUF_ASSERT_FREE(st->rbuf);
 	    BUF_ALLOC(st->rbuf,"udp_afterpoll");
-	    rv=recvfrom(st->fd, st->rbuf->start, st->rbuf->len, 0,
-			(struct sockaddr *)&from, &fromlen);
+	    buffer_init(st->rbuf,calculate_max_start_pad());
+	    rv=recvfrom(fd, st->rbuf->start,
+			buf_remaining_space(st->rbuf),
+			0, &from.sa, &fromlen);
 	    if (rv>0) {
 		st->rbuf->size=rv;
+		if (st->use_proxy) {
+		    /* Check that the packet came from our poxy server;
+		       we shouldn't be contacted directly by anybody else
+		       (since they can trivially forge source addresses) */
+		    if (!iaddr_equal(&from,&st->proxy)) {
+			Message(M_INFO,"udp: received packet that's not "
+				"from the proxy\n");
+			BUF_FREE(st->rbuf);
+			continue;
+		    }
+		    /* proxy protocol supports ipv4 transport only */
+		    from.sa.sa_family=AF_INET;
+		    memcpy(&from.sin.sin_addr,buf_unprepend(st->rbuf,4),4);
+		    buf_unprepend(st->rbuf,2);
+		    memcpy(&from.sin.sin_port,buf_unprepend(st->rbuf,2),2);
+		}
+		struct comm_addr ca;
+		ca.comm=&st->ops;
+		ca.ia=from;
+		ca.ix=i;
 		done=False;
-		for (n=st->notify; n; n=n->next) {
-		    if (n->fn(n->state, st->rbuf, &from)) {
+		LIST_FOREACH(n, &st->notify, entry) {
+		    if (n->fn(n->state, st->rbuf, &ca)) {
 			done=True;
 			break;
 		    }
 		}
 		if (!done) {
-		    /* XXX manufacture and send NAK packet */
-		    Message(M_WARNING,"Need to send NAK\n");
+		    uint32_t msgtype;
+		    if (st->rbuf->size>12 /* prevents traffic amplification */
+			&& ((msgtype=get_uint32(st->rbuf->start+8))
+			    != LABEL_NAK)) {
+			uint32_t source,dest;
+			/* Manufacture and send NAK packet */
+			source=get_uint32(st->rbuf->start); /* Us */
+			dest=get_uint32(st->rbuf->start+4); /* Them */
+			send_nak(&ca,source,dest,msgtype,st->rbuf,"unwanted");
+		    }
 		    BUF_FREE(st->rbuf);
 		}
 		BUF_ASSERT_FREE(st->rbuf);
@@ -103,56 +171,174 @@ static void udp_afterpoll(void *state, struct pollfd *fds, int nfds,
 static void request_notify(void *commst, void *nst, comm_notify_fn *fn)
 {
     struct udp *st=commst;
-    struct notify_list *n;
+    struct comm_notify_entry *n;
     
     n=safe_malloc(sizeof(*n),"request_notify");
     n->fn=fn;
     n->state=nst;
-    n->next=st->notify;
-    st->notify=n;
+    LIST_INSERT_HEAD(&st->notify, n, entry);
 }
 
 static void release_notify(void *commst, void *nst, comm_notify_fn *fn)
 {
     struct udp *st=commst;
-    struct notify_list *n, **p, *t;
+    struct comm_notify_entry *n, *t;
 
     /* XXX untested */
-    p=&st->notify;
-    for (n=st->notify; n; )
-    {
+    LIST_FOREACH_SAFE(n, &st->notify, entry, t) {
 	if (n->state==nst && n->fn==fn) {
-	    t=n;
-	    *p=n->next;
-	    n=n->next;
-	    free(t);
-	} else {
-	    p=&n->next;
-	    n=n->next;
+	    LIST_REMOVE(n, entry);
+	    free(n);
 	}
     }
 }
 
 static bool_t udp_sendmsg(void *commst, struct buffer_if *buf,
-			  struct sockaddr_in *dest)
+			  const struct comm_addr *dest)
 {
     struct udp *st=commst;
+    uint8_t *sa;
 
-    /* XXX fix error reporting */
-    sendto(st->fd, buf->start, buf->size, 0,
-	   (struct sockaddr *)dest, sizeof(*dest));
+    if (st->use_proxy) {
+	sa=buf_prepend(buf,8);
+	if (dest->ia.sa.sa_family != AF_INET) {
+	    Message(M_INFO,
+               "udp: proxy means dropping outgoing non-IPv4 packet to %s\n",
+		    iaddr_to_string(&dest->ia));
+	    return False;
+	}
+	memcpy(sa,&dest->ia.sin.sin_addr,4);
+	memset(sa+4,0,4);
+	memcpy(sa+6,&dest->ia.sin.sin_port,2);
+	sendto(st->socks[0].fd,sa,buf->size+8,0,&st->proxy.sa,
+	       iaddr_socklen(&st->proxy));
+	buf_unprepend(buf,8);
+    } else {
+	int i,r;
+	bool_t allunsupported=True;
+	for (i=0; i<st->n_socks; i++) {
+	    if (dest->ia.sa.sa_family != st->socks[i].addr.sa.sa_family)
+		/* no point even trying */
+		continue;
+	    r=sendto(st->socks[i].fd, buf->start, buf->size, 0,
+		     &dest->ia.sa, iaddr_socklen(&dest->ia));
+	    if (r>=0) return True;
+	    if (!(errno==EAFNOSUPPORT || errno==ENETUNREACH))
+		/* who knows what that error means? */
+		allunsupported=False;
+	}
+	return !allunsupported; /* see doc for comm_sendmsg_fn in secnet.h */
+    }
 
     return True;
 }
 
+static void udp_make_socket(struct udp *st, struct udpsock *us)
+{
+    const union iaddr *addr=&us->addr;
+    us->fd=socket(addr->sa.sa_family, SOCK_DGRAM, IPPROTO_UDP);
+    if (us->fd<0) {
+	fatal_perror("udp (%s:%d): socket",st->loc.file,st->loc.line);
+    }
+    if (fcntl(us->fd, F_SETFL, fcntl(us->fd, F_GETFL)|O_NONBLOCK)==-1) {
+	fatal_perror("udp (%s:%d): fcntl(set O_NONBLOCK)",
+		     st->loc.file,st->loc.line);
+    }
+    setcloexec(us->fd);
+#ifdef CONFIG_IPV6
+    if (addr->sa.sa_family==AF_INET6) {
+	int r;
+	int optval=1;
+	socklen_t optlen=sizeof(optval);
+	r=setsockopt(us->fd,IPPROTO_IPV6,IPV6_V6ONLY,&optval,optlen);
+	if (r) fatal_perror("udp (%s:%d): setsockopt(,IPV6_V6ONLY,&1,)",
+			    st->loc.file,st->loc.line);
+    }
+#endif
+
+    if (st->authbind) {
+	pid_t c;
+	int status;
+
+	/* XXX this fork() and waitpid() business needs to be hidden
+	   in some system-specific library functions. */
+	c=fork();
+	if (c==-1) {
+	    fatal_perror("udp_phase_hook: fork() for authbind");
+	}
+	if (c==0) {
+	    char *argv[5], addrstr[33], portstr[5];
+	    const char *addrfam;
+	    int port;
+	    switch (addr->sa.sa_family) {
+	    case AF_INET:
+		sprintf(addrstr,"%08lX",(long)addr->sin.sin_addr.s_addr);
+		port=addr->sin.sin_port;
+		addrfam=NULL;
+		break;
+#ifdef CONFIG_IPV6
+	    case AF_INET6: {
+		int i;
+		for (i=0; i<16; i++)
+		    sprintf(addrstr+i*2,"%02X",addr->sin6.sin6_addr.s6_addr[i]);
+		port=addr->sin6.sin6_port;
+		addrfam="6";
+		break;
+	    }
+#endif /*CONFIG_IPV6*/
+	    default:
+		fatal("udp (%s:%d): unsupported address family for authbind",
+		      st->loc.file,st->loc.line);
+	    }
+	    sprintf(portstr,"%04X",port);
+	    argv[0]=st->authbind;
+	    argv[1]=addrstr;
+	    argv[2]=portstr;
+	    argv[3]=(char*)addrfam;
+	    argv[4]=NULL;
+	    dup2(us->fd,0);
+	    execvp(st->authbind,argv);
+	    _exit(255);
+	}
+	while (waitpid(c,&status,0)==-1) {
+	    if (errno==EINTR) continue;
+	    fatal_perror("udp (%s:%d): authbind",st->loc.file,st->loc.line);
+	}
+	if (WIFSIGNALED(status)) {
+	    fatal("udp (%s:%d): authbind died on signal %d",st->loc.file,
+		  st->loc.line, WTERMSIG(status));
+	}
+	if (WIFEXITED(status) && WEXITSTATUS(status)!=0) {
+	    fatal("udp (%s:%d): authbind died with status %d",st->loc.file,
+		  st->loc.line, WEXITSTATUS(status));
+	}
+    } else {
+	if (bind(us->fd, &addr->sa, iaddr_socklen(addr))!=0) {
+	    fatal_perror("udp (%s:%d): bind",st->loc.file,st->loc.line);
+	}
+    }
+}
+
+static void udp_phase_hook(void *sst, uint32_t new_phase)
+{
+    struct udp *st=sst;
+    int i;
+    for (i=0; i<st->n_socks; i++)
+	udp_make_socket(st,&st->socks[i]);
+
+    register_for_poll(st,udp_beforepoll,udp_afterpoll,MAX_SOCKETS,"udp");
+}
+
 static list_t *udp_apply(closure_t *self, struct cloc loc, dict_t *context,
 			 list_t *args)
 {
     struct udp *st;
-    item_t *i;
+    item_t *item;
+    list_t *caddrl;
     dict_t *d;
-    uint16_t local_port=0;
-    struct sockaddr_in addr;
+    list_t *l;
+    uint32_t a;
+    int i;
 
     st=safe_malloc(sizeof(*st),"udp_apply(st)");
     st->loc=loc;
@@ -164,44 +350,71 @@ static list_t *udp_apply(closure_t *self, struct cloc loc, dict_t *context,
     st->ops.request_notify=request_notify;
     st->ops.release_notify=release_notify;
     st->ops.sendmsg=udp_sendmsg;
+    st->ops.addr_to_string=addr_to_string;
+    st->use_proxy=False;
+    LIST_INIT(&st->notify);
 
-    i=list_elem(args,0);
-    if (!i || i->type!=t_dict) {
+    item=list_elem(args,0);
+    if (!item || item->type!=t_dict) {
 	cfgfatal(st->loc,"udp","first argument must be a dictionary\n");
     }
-    d=i->data.dict;
+    d=item->data.dict;
 
-    local_port=dict_read_number(d,"port",False,"udp",st->loc,0);
-    st->rbuf=find_cl_if(d,"buffer",CL_BUFFER,True,"udp",st->loc);
+    int port=dict_read_number(d,"port",True,"udp",st->loc,0);
 
-    st->fd=socket(AF_INET, SOCK_DGRAM, 0);
-    if (st->fd<0) {
-	fatal_perror("udp_apply (%s:%d): socket",loc.file,loc.line);
-    }
-    if (fcntl(st->fd, F_SETFL, fcntl(st->fd, F_GETFL)|O_NONBLOCK)==-1) {
-	fatal_perror("udp_apply (%s:%d): fcntl(set O_NONBLOCK)",
-		     loc.file,loc.line);
-    }
-    if (fcntl(st->fd, F_SETFD, FD_CLOEXEC)==-1) {
-	fatal_perror("udp_apply (%s:%d): fcntl(set FD_CLOEXEC)",
-		     loc.file,loc.line);
-    }
+    union iaddr defaultaddrs[] = {
+#ifdef CONFIG_IPV6
+	{ .sin6 = { .sin6_family=AF_INET6,
+		    .sin6_port=htons(port),
+		    .sin6_addr=IN6ADDR_ANY_INIT } },
+#endif
+	{ .sin = { .sin_family=AF_INET,
+		   .sin_port=htons(port),
+		   .sin_addr= { .s_addr=INADDR_ANY } } }
+    };
+
+    caddrl=dict_lookup(d,"address");
+    st->n_socks=caddrl ? list_length(caddrl) : (int)ARRAY_SIZE(defaultaddrs);
+    if (st->n_socks<=0 || st->n_socks>MAX_SOCKETS)
+	cfgfatal(st->loc,"udp","`address' must be 1..%d addresses",
+		 MAX_SOCKETS);
 
-    memset(&addr, 0, sizeof(addr));
-    addr.sin_family=AF_INET;
-    if (local_port) {
-	addr.sin_port=htons(local_port);
+    for (i=0; i<st->n_socks; i++) {
+	struct udpsock *us=&st->socks[i];
+	if (!list_length(caddrl)) {
+	    us->addr=defaultaddrs[i];
+	} else {
+	    string_item_to_iaddr(list_elem(caddrl,i),port,&us->addr,"udp");
+	}
+	us->fd=-1;
     }
-    if (bind(st->fd, (struct sockaddr *)&addr, sizeof(addr))!=0) {
-	fatal_perror("udp_apply (%s:%d): bind",loc.file,loc.line);
+
+    st->rbuf=find_cl_if(d,"buffer",CL_BUFFER,True,"udp",st->loc);
+    st->authbind=dict_read_string(d,"authbind",False,"udp",st->loc);
+    l=dict_lookup(d,"proxy");
+    if (l) {
+	st->use_proxy=True;
+	st->proxy.sa.sa_family=AF_INET;
+	item=list_elem(l,0);
+	if (!item || item->type!=t_string) {
+	    cfgfatal(st->loc,"udp","proxy must supply ""addr"",port\n");
+	}
+	a=string_item_to_ipaddr(item,"proxy");
+	st->proxy.sin.sin_addr.s_addr=htonl(a);
+	item=list_elem(l,1);
+	if (!item || item->type!=t_number) {
+	    cfgfatal(st->loc,"udp","proxy must supply ""addr"",port\n");
+	}
+	st->proxy.sin.sin_port=htons(item->data.number);
     }
 
-    register_for_poll(st,udp_beforepoll,udp_afterpoll,1,"udp");
+    update_max_start_pad(&comm_max_start_pad, st->use_proxy ? 8 : 0);
+
+    add_hook(PHASE_GETRESOURCES,udp_phase_hook,st);
 
     return new_closure(&st->cl);
 }
 
-init_module udp_module;
 void udp_module(dict_t *dict)
 {
     add_closure(dict,"udp",udp_apply);