X-Git-Url: http://www.chiark.greenend.org.uk/ucgi/~ian/git?p=secnet.git;a=blobdiff_plain;f=udp.c;h=477dea38c7efe47e97ab5f52656fc79c07953509;hp=f05596202d8e0f5d7a59d6205b60cb7b8b4ac89a;hb=2093fb5ca832669236d9e4e8b6475a14b96b3d2a;hpb=8689b3a94c043f04e334a7b181a7250ad5940616 diff --git a/udp.c b/udp.c index f055962..477dea3 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 #include #include +#include +#include +#include #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; @@ -27,10 +30,6 @@ 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; @@ -41,14 +40,26 @@ struct udp { closure_t cl; struct comm_if ops; struct cloc loc; + union iaddr addr; int fd; + string_t authbind; struct buffer_if *rbuf; struct notify_list *notify; + bool_t use_proxy; + union iaddr proxy; }; +static const char *addr_to_string(void *commst, const struct comm_addr *ca) { + struct udp *st=commst; + static char sbuf[100]; + + snprintf(sbuf, sizeof(sbuf), "udp:%s-%s", + iaddr_to_string(&st->addr), 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) { struct udp *st=state; if (*nfds_io<1) { @@ -61,12 +72,11 @@ 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; + union iaddr from; + socklen_t fromlen; struct notify_list *n; bool_t done; int rv; @@ -76,20 +86,49 @@ static void udp_afterpoll(void *state, struct pollfd *fds, int nfds, 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(st->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; done=False; for (n=st->notify; n; n=n->next) { - if (n->fn(n->state, st->rbuf, &from)) { + 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); @@ -134,25 +173,107 @@ 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_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->fd,sa,buf->size+8,0,&st->proxy.sa, + iaddr_socklen(&st->proxy)); + buf_unprepend(buf,8); + } else { + sendto(st->fd, buf->start, buf->size, 0, + &dest->ia.sa, iaddr_socklen(&dest->ia)); + } return True; } +static void udp_phase_hook(void *sst, uint32_t new_phase) +{ + struct udp *st=sst; + union iaddr addr; + + 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); + } + if (fcntl(st->fd, F_SETFL, fcntl(st->fd, F_GETFL)|O_NONBLOCK)==-1) { + fatal_perror("udp (%s:%d): fcntl(set O_NONBLOCK)", + st->loc.file,st->loc.line); + } + setcloexec(st->fd); + + addr=st->addr; + 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[4], addrstr[9], portstr[5]; + switch (addr.sa.sa_family) { + case AF_INET: + sprintf(addrstr,"%08lX",(long)addr.sin.sin_addr.s_addr); + sprintf(portstr,"%04X",addr.sin.sin_port); + break; + default: + fatal("udp (%s:%d): unsupported address family for authbind", + st->loc.file,st->loc.line); + } + argv[0]=st->authbind; + argv[1]=addrstr; + argv[2]=portstr; + argv[3]=NULL; + dup2(st->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(st->fd, &addr.sa, iaddr_socklen(&addr))!=0) { + fatal_perror("udp (%s:%d): bind",st->loc.file,st->loc.line); + } + } + + register_for_poll(st,udp_beforepoll,udp_afterpoll,1,"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 *i,*j; dict_t *d; - uint16_t local_port=0; - struct sockaddr_in addr; + list_t *l; + uint32_t a; st=safe_malloc(sizeof(*st),"udp_apply(st)"); st->loc=loc; @@ -164,6 +285,8 @@ 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; i=list_elem(args,0); if (!i || i->type!=t_dict) { @@ -171,37 +294,36 @@ static list_t *udp_apply(closure_t *self, struct cloc loc, dict_t *context, } d=i->data.dict; - local_port=dict_read_number(d,"port",False,"udp",st->loc,0); + st->addr.sa.sa_family=AF_INET; + j=dict_find_item(d,"address",False,"udp",st->loc); + st->addr.sin.sin_addr.s_addr=j?string_item_to_ipaddr(j, "udp"):INADDR_ANY; + st->addr.sin.sin_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->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); + 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; + 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.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.sin_port=htons(i->data.number); } - memset(&addr, 0, sizeof(addr)); - addr.sin_family=AF_INET; - if (local_port) { - addr.sin_port=htons(local_port); - } - if (bind(st->fd, (struct sockaddr *)&addr, sizeof(addr))!=0) { - fatal_perror("udp_apply (%s:%d): bind",loc.file,loc.line); - } + update_max_start_pad(&comm_max_start_pad, st->use_proxy ? 8 : 0); - register_for_poll(st,udp_beforepoll,udp_afterpoll,1,"udp"); + 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);