236 lines
6.7 KiB
C
236 lines
6.7 KiB
C
/*
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* This module determines the type of socket (datagram, stream), the client
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* socket address and port, the server socket address and port. In addition,
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* it provides methods to map a transport address to a printable host name
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* or address. Socket address information results are in static memory.
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*
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* The result from the hostname lookup method is STRING_PARANOID when a host
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* pretends to have someone elses name, or when a host name is available but
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* could not be verified.
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*
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* When lookup or conversion fails the result is set to STRING_UNKNOWN.
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*
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* Diagnostics are reported through syslog(3).
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*
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* Author: Wietse Venema, Eindhoven University of Technology, The Netherlands.
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*/
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#ifndef lint
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static char sccsid[] = "@(#) socket.c 1.15 97/03/21 19:27:24";
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#endif
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/* System libraries. */
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#include <sys/types.h>
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#include <sys/param.h>
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#include <sys/socket.h>
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#include <netinet/in.h>
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#include <netdb.h>
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#include <stdio.h>
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#include <syslog.h>
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#include <string.h>
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extern char *inet_ntoa();
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/* Local stuff. */
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#include "tcpd.h"
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/* Forward declarations. */
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static void sock_sink();
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#ifdef APPEND_DOT
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/*
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* Speed up DNS lookups by terminating the host name with a dot. Should be
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* done with care. The speedup can give problems with lookups from sources
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* that lack DNS-style trailing dot magic, such as local files or NIS maps.
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*/
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static struct hostent *gethostbyname_dot(name)
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char *name;
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{
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char dot_name[MAXHOSTNAMELEN + 1];
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/*
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* Don't append dots to unqualified names. Such names are likely to come
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* from local hosts files or from NIS.
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*/
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if (strchr(name, '.') == 0 || strlen(name) >= MAXHOSTNAMELEN - 1) {
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return (gethostbyname(name));
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} else {
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sprintf(dot_name, "%s.", name);
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return (gethostbyname(dot_name));
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}
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}
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#define gethostbyname gethostbyname_dot
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#endif
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/* sock_host - look up endpoint addresses and install conversion methods */
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void sock_host(request)
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struct request_info *request;
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{
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static struct sockaddr_in client;
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static struct sockaddr_in server;
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int len;
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char buf[BUFSIZ];
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int fd = request->fd;
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sock_methods(request);
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/*
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* Look up the client host address. Hal R. Brand <BRAND@addvax.llnl.gov>
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* suggested how to get the client host info in case of UDP connections:
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* peek at the first message without actually looking at its contents. We
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* really should verify that client.sin_family gets the value AF_INET,
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* but this program has already caused too much grief on systems with
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* broken library code.
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*/
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len = sizeof(client);
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if (getpeername(fd, (struct sockaddr *) & client, &len) < 0) {
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request->sink = sock_sink;
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len = sizeof(client);
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if (recvfrom(fd, buf, sizeof(buf), MSG_PEEK,
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(struct sockaddr *) & client, &len) < 0) {
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tcpd_warn("can't get client address: %m");
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return; /* give up */
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}
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#ifdef really_paranoid
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memset(buf, 0 sizeof(buf));
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#endif
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}
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request->client->sin = &client;
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/*
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* Determine the server binding. This is used for client username
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* lookups, and for access control rules that trigger on the server
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* address or name.
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*/
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len = sizeof(server);
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if (getsockname(fd, (struct sockaddr *) & server, &len) < 0) {
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tcpd_warn("getsockname: %m");
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return;
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}
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request->server->sin = &server;
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}
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/* sock_hostaddr - map endpoint address to printable form */
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void sock_hostaddr(host)
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struct host_info *host;
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{
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struct sockaddr_in *sin = host->sin;
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if (sin != 0)
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STRN_CPY(host->addr, inet_ntoa(sin->sin_addr), sizeof(host->addr));
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}
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/* sock_hostname - map endpoint address to host name */
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void sock_hostname(host)
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struct host_info *host;
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{
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struct sockaddr_in *sin = host->sin;
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struct hostent *hp;
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int i;
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/*
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* On some systems, for example Solaris 2.3, gethostbyaddr(0.0.0.0) does
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* not fail. Instead it returns "INADDR_ANY". Unfortunately, this does
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* not work the other way around: gethostbyname("INADDR_ANY") fails. We
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* have to special-case 0.0.0.0, in order to avoid false alerts from the
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* host name/address checking code below.
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*/
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if (sin != 0 && sin->sin_addr.s_addr != 0
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&& (hp = gethostbyaddr((char *) &(sin->sin_addr),
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sizeof(sin->sin_addr), AF_INET)) != 0) {
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STRN_CPY(host->name, hp->h_name, sizeof(host->name));
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/*
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* Verify that the address is a member of the address list returned
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* by gethostbyname(hostname).
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*
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* Verify also that gethostbyaddr() and gethostbyname() return the same
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* hostname, or rshd and rlogind may still end up being spoofed.
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*
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* On some sites, gethostbyname("localhost") returns "localhost.domain".
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* This is a DNS artefact. We treat it as a special case. When we
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* can't believe the address list from gethostbyname("localhost")
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* we're in big trouble anyway.
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*/
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if ((hp = gethostbyname(host->name)) == 0) {
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/*
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* Unable to verify that the host name matches the address. This
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* may be a transient problem or a botched name server setup.
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*/
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tcpd_warn("can't verify hostname: gethostbyname(%s) failed",
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host->name);
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} else if (STR_NE(host->name, hp->h_name)
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&& STR_NE(host->name, "localhost")) {
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/*
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* The gethostbyaddr() and gethostbyname() calls did not return
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* the same hostname. This could be a nameserver configuration
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* problem. It could also be that someone is trying to spoof us.
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*/
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tcpd_warn("host name/name mismatch: %s != %.*s",
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host->name, STRING_LENGTH, hp->h_name);
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} else {
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/*
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* The address should be a member of the address list returned by
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* gethostbyname(). We should first verify that the h_addrtype
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* field is AF_INET, but this program has already caused too much
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* grief on systems with broken library code.
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*/
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for (i = 0; hp->h_addr_list[i]; i++) {
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if (memcmp(hp->h_addr_list[i],
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(char *) &sin->sin_addr,
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sizeof(sin->sin_addr)) == 0)
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return; /* name is good, keep it */
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}
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/*
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* The host name does not map to the initial address. Perhaps
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* someone has messed up. Perhaps someone compromised a name
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* server.
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*/
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tcpd_warn("host name/address mismatch: %s != %.*s",
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inet_ntoa(sin->sin_addr), STRING_LENGTH, hp->h_name);
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}
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strcpy(host->name, paranoid); /* name is bad, clobber it */
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}
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}
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/* sock_sink - absorb unreceived IP datagram */
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static void sock_sink(fd)
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int fd;
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{
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char buf[BUFSIZ];
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struct sockaddr_in sin;
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int size = sizeof(sin);
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/*
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* Eat up the not-yet received datagram. Some systems insist on a
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* non-zero source address argument in the recvfrom() call below.
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*/
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(void) recvfrom(fd, buf, sizeof(buf), 0, (struct sockaddr *) & sin, &size);
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}
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