X-Git-Url: http://www.chiark.greenend.org.uk/ucgi/~ian/git?p=secnet.git;a=blobdiff_plain;f=udp.c;h=c83e618fb6ca91876dcb1307c2bac516ba35a06a;hp=65208650f998a7cbc5f670a1d7114ae40adc677b;hb=bf28fc736c33aa8b26b3c3267cf4c3b33e69c4a5;hpb=794f2398b8fe84bf398bb10d6eeca6fe6737f65f diff --git a/udp.c b/udp.c index 6520865..c83e618 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. */ @@ -20,8 +16,12 @@ #include #include #include +#include +#include #include "util.h" #include "unaligned.h" +#include "ipaddr.h" +#include "magic.h" static beforepoll_fn udp_beforepoll; static afterpoll_fn udp_afterpoll; @@ -29,10 +29,6 @@ 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 { comm_notify_fn *fn; void *state; @@ -43,16 +39,42 @@ struct udp { closure_t cl; struct comm_if ops; struct cloc loc; + uint32_t addr; uint16_t port; int fd; string_t authbind; struct buffer_if *rbuf; struct notify_list *notify; + bool_t use_proxy; + struct sockaddr_in proxy; }; +static const char *saddr_to_string(const struct sockaddr_in *sin) { + static char bufs[2][100]; + static int b; + + b ^= 1; + snprintf(bufs[b], sizeof(bufs[b]), "[%s]:%d", + inet_ntoa(sin->sin_addr), + ntohs(sin->sin_port)); + return bufs[b]; +} + +static const char *addr_to_string(void *commst, const struct comm_addr *ca) { + struct udp *st=commst; + static char sbuf[100]; + + struct sockaddr_in la; + la.sin_addr.s_addr=htonl(st->addr); + la.sin_port=htons(st->port); + + snprintf(sbuf, sizeof(sbuf), "udp:%s-%s", + saddr_to_string(&la), saddr_to_string(&ca->sin)); + 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) { struct udp *st=state; if (*nfds_io<1) { @@ -65,18 +87,18 @@ static int udp_beforepoll(void *state, struct pollfd *fds, int *nfds_io, 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; + socklen_t fromlen; struct notify_list *n; bool_t done; int rv; if (nfds && (fds->revents & POLLIN)) { do { + FILLZERO(from); fromlen=sizeof(from); BUF_ASSERT_FREE(st->rbuf); BUF_ALLOC(st->rbuf,"udp_afterpoll"); @@ -84,25 +106,53 @@ static void udp_afterpoll(void *state, struct pollfd *fds, int nfds, (struct sockaddr *)&from, &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 (memcmp(&from.sin_addr,&st->proxy.sin_addr,4)!=0 || + memcmp(&from.sin_port,&st->proxy.sin_port,2)!=0) { + Message(M_INFO,"udp: received packet that's not " + "from the proxy\n"); + BUF_FREE(st->rbuf); + continue; + } + memcpy(&from.sin_addr,buf_unprepend(st->rbuf,4),4); + buf_unprepend(st->rbuf,2); + memcpy(&from.sin_port,buf_unprepend(st->rbuf,2),2); + } done=False; for (n=st->notify; n; n=n->next) { - if (n->fn(n->state, st->rbuf, &from)) { + struct comm_addr ca; + FILLZERO(ca); + ca.comm=&st->ops; + ca.sin=from; + if (n->fn(n->state, st->rbuf, &ca)) { done=True; break; } } if (!done) { - uint32_t source,dest; - /* XXX manufacture and send NAK packet */ - source=get_uint32(st->rbuf->start); /* Us */ - dest=get_uint32(st->rbuf->start+4); /* Them */ - Message(M_INFO,"udp (port %d): sending NAK\n",st->port); - buffer_init(st->rbuf,0); - buf_append_uint32(st->rbuf,dest); - buf_append_uint32(st->rbuf,source); - buf_append_uint32(st->rbuf,0); /* NAK is msg type 0 */ - sendto(st->fd, st->rbuf->start, st->rbuf->size, 0, - (struct sockaddr *)&from, sizeof(from)); + 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 */ + Message(M_INFO,"udp (port %d, peer %s):" + " %08"PRIx32"<-%08"PRIx32": %08"PRIx32":" + " unwanted/incorrect, sending NAK\n", + st->port, saddr_to_string(&from), + dest, source, msgtype); + buffer_init(st->rbuf,0); + buf_append_uint32(st->rbuf,dest); + buf_append_uint32(st->rbuf,source); + buf_append_uint32(st->rbuf,LABEL_NAK); + sendto(st->fd, st->rbuf->start, st->rbuf->size, 0, + (struct sockaddr *)&from, sizeof(from)); + } BUF_FREE(st->rbuf); } BUF_ASSERT_FREE(st->rbuf); @@ -147,13 +197,22 @@ static void release_notify(void *commst, void *nst, comm_notify_fn *fn) } 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->start-8; + memcpy(sa,&dest->sin.sin_addr,4); + memset(sa+4,0,4); + memcpy(sa+6,&dest->sin.sin_port,2); + sendto(st->fd,sa,buf->size+8,0,(struct sockaddr *)&st->proxy, + sizeof(st->proxy)); + } else { + sendto(st->fd, buf->start, buf->size, 0, + (struct sockaddr *)&dest->sin, sizeof(dest->sin)); + } return True; } @@ -163,7 +222,7 @@ static void udp_phase_hook(void *sst, uint32_t new_phase) struct udp *st=sst; struct sockaddr_in addr; - st->fd=socket(AF_INET, SOCK_DGRAM, 0); + st->fd=socket(PF_INET, SOCK_DGRAM, IPPROTO_UDP); if (st->fd<0) { fatal_perror("udp (%s:%d): socket",st->loc.file,st->loc.line); } @@ -176,8 +235,9 @@ static void udp_phase_hook(void *sst, uint32_t new_phase) st->loc.file,st->loc.line); } - memset(&addr, 0, sizeof(addr)); + FILLZERO(addr); addr.sin_family=AF_INET; + addr.sin_addr.s_addr=htonl(st->addr); addr.sin_port=htons(st->port); if (st->authbind) { pid_t c; @@ -190,22 +250,29 @@ static void udp_phase_hook(void *sst, uint32_t new_phase) fatal_perror("udp_phase_hook: fork() for authbind"); } if (c==0) { - char *argv[4]; + char *argv[4], addrstr[9], portstr[5]; + sprintf(addrstr,"%08lX",(long)addr.sin_addr.s_addr); + sprintf(portstr,"%04X",addr.sin_port); argv[0]=st->authbind; - argv[1]="00000000"; - argv[2]=alloca(8); - if (!argv[2]) exit(ENOMEM); - sprintf(argv[2],"%04X",htons(st->port)); + argv[1]=addrstr; + argv[2]=portstr; argv[3]=NULL; dup2(st->fd,0); execvp(st->authbind,argv); - exit(ENOEXEC); + _exit(255); } - waitpid(c,&status,0); - if (WEXITSTATUS(status)!=0) { - errno=WEXITSTATUS(status); + 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(st->fd, (struct sockaddr *)&addr, sizeof(addr))!=0) { fatal_perror("udp (%s:%d): bind",st->loc.file,st->loc.line); @@ -219,8 +286,10 @@ 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 *i,*j; dict_t *d; + list_t *l; + uint32_t a; st=safe_malloc(sizeof(*st),"udp_apply(st)"); st->loc=loc; @@ -229,10 +298,14 @@ static list_t *udp_apply(closure_t *self, struct cloc loc, dict_t *context, st->cl.apply=NULL; st->cl.interface=&st->ops; st->ops.st=st; + st->ops.min_start_pad=0; + st->ops.min_end_pad=0; 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->port=0; + st->use_proxy=False; i=list_elem(args,0); if (!i || i->type!=t_dict) { @@ -240,16 +313,35 @@ static list_t *udp_apply(closure_t *self, struct cloc loc, dict_t *context, } d=i->data.dict; + j=dict_find_item(d,"address",False,"udp",st->loc); + st->addr=j?string_item_to_ipaddr(j, "udp"):INADDR_ANY; st->port=dict_read_number(d,"port",True,"udp",st->loc,0); 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; + FILLZERO(st->proxy); + st->proxy.sin_family=AF_INET; + i=list_elem(l,0); + if (!i || i->type!=t_string) { + cfgfatal(st->loc,"udp","proxy must supply ""addr"",port\n"); + } + a=string_item_to_ipaddr(i,"proxy"); + st->proxy.sin_addr.s_addr=htonl(a); + i=list_elem(l,1); + if (!i || i->type!=t_number) { + cfgfatal(st->loc,"udp","proxy must supply ""addr"",port\n"); + } + st->proxy.sin_port=htons(i->data.number); + st->ops.min_start_pad=8; + } 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);