/* * Socket functions used in rsync. * * Copyright (C) 1992-2001 Andrew Tridgell <tridge@samba.org> * Copyright (C) 2001, 2002 Martin Pool <mbp@samba.org> * Copyright (C) 2003-2020 Wayne Davison * * This program is free software; you can redistribute it and/or modify * it under the terms of the GNU General Public License as published by * the Free Software Foundation; either version 3 of the License, or * (at your option) any later version. * * This program is distributed in the hope that it will be useful, * but WITHOUT ANY WARRANTY; without even the implied warranty of * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the * GNU General Public License for more details. * * You should have received a copy of the GNU General Public License along * with this program; if not, visit the http://fsf.org website. */ /* This file is now converted to use the new-style getaddrinfo() * interface, which supports IPv6 but is also supported on recent * IPv4-only machines.  On systems that don't have that interface, we * emulate it using the KAME implementation. */ #include "rsync.h"#include <poll.h>#include "itypes.h"#include "ifuncs.h"#ifdef HAVE_NETINET_IN_SYSTM_H#include <netinet/in_systm.h>#endif#ifdef HAVE_NETINET_IP_H#include <netinet/ip.h>#endif#include <netinet/tcp.h> extern char *bind_address;extern char *sockopts;extern int default_af_hint;extern int connect_timeout;extern int pid_file_fd; #ifdef HAVE_SIGACTIONstatic struct sigaction sigact;#endif static int sock_exec(const char *prog);static char *shell_quote_connect_host(const char *host); #define PROXY_BUF_SIZE 1024 /* Establish a proxy connection on an open socket to a web proxy by using the * CONNECT method.  If proxy_user and proxy_pass are not NULL, they are used to * authenticate to the proxy using the "Basic" proxy-authorization protocol. */static int establish_proxy_connection(int fd, char *host, int port, char *proxy_user, char *proxy_pass){	char *cp, buffer[PROXY_BUF_SIZE + 1];	char *authhdr, authbuf[PROXY_BUF_SIZE + 1];	int len; 	/* Reject control bytes in the host so they can't be smuggled into the	 * HTTP CONNECT request line (CRLF header/request injection). */	for (cp = host; *cp; cp++) {		if ((unsigned char)*cp < 0x20 || (unsigned char)*cp == 0x7f) {			rprintf(FERROR, "invalid control character in proxy CONNECT host\n");			return -1;		}	} 	if (proxy_user && proxy_pass) {		stringjoin(buffer, PROXY_BUF_SIZE,			 proxy_user, ":", proxy_pass, NULL);		len = strlen(buffer); 		if ((len*8 + 5) / 6 >= PROXY_BUF_SIZE - 3) {			rprintf(FERROR,				"authentication information is too long\n");			return -1;		} 		base64_encode(buffer, len, authbuf, 1);		authhdr = "\r\nProxy-Authorization: Basic ";	} else {		*authbuf = '\0';		authhdr = "";	} 	len = snprintf(buffer, PROXY_BUF_SIZE, "CONNECT %s:%d HTTP/1.0%s%s\r\n\r\n", host, port, authhdr, authbuf);	if (len <= 0 || len >= PROXY_BUF_SIZE) {		rprintf(FERROR, "proxy CONNECT request too long\n");		return -1;	}	if (write(fd, buffer, len) != len) {		rsyserr(FERROR, errno, "failed to write to proxy");		return -1;	} 	for (cp = buffer; cp < &buffer[PROXY_BUF_SIZE - 1]; cp++) {		if (read(fd, cp, 1) != 1) {			rsyserr(FERROR, errno, "failed to read from proxy");			return -1;		}		if (*cp == '\n')			break;	} 	if (cp == &buffer[PROXY_BUF_SIZE - 1]) {		rprintf(FERROR, "proxy response line too long\n");		return -1;	}	*cp = '\0';	if (cp > buffer && cp[-1] == '\r')		cp[-1] = '\0';	if (strncmp(buffer, "HTTP/", 5) != 0) {		rprintf(FERROR, "bad response from proxy -- %s\n",			buffer);		return -1;	}	for (cp = &buffer[5]; isDigit(cp) || *cp == '.'; cp++) {}	while (*cp == ' ')		cp++;	if (*cp != '2') {		rprintf(FERROR, "bad response from proxy -- %s\n",			buffer);		return -1;	}	/* throw away the rest of the HTTP header */	while (1) {		for (cp = buffer; cp < &buffer[PROXY_BUF_SIZE - 1]; cp++) {			if (read(fd, cp, 1) != 1) {				rsyserr(FERROR, errno,					"failed to read from proxy");				return -1;			}			if (*cp == '\n')				break;		}		if (cp == &buffer[PROXY_BUF_SIZE - 1]) {			rprintf(FERROR, "proxy response header line too long\n");			return -1;		}		if (cp > buffer && *cp == '\n')			cp--;		if (cp == buffer && (*cp == '\n' || *cp == '\r'))			break;	}	return 0;} static char *shell_quote_connect_host(const char *host){	const char *s;	char *quoted, *t;	size_t len = 2; /* surrounding single quotes */ 	for (s = host; *s; s++)		len += *s == '\'' ? 4 : 1;	quoted = new_array(char, len + 1);	t = quoted;	*t++ = '\'';	for (s = host; *s; s++) {		if (*s == '\'') {			memcpy(t, "'\\''", 4);			t += 4;		} else			*t++ = *s;	}	*t++ = '\'';	*t = '\0';	return quoted;} /* %H is substituted into a free-form command string that a shell then runs, and * a hook of the form `sh -c '... %H ...'` re-parses the word in a nested shell * where the quoting we added has already been consumed.  Restrict the host to * characters that stay data through such a pass.  ('Any shell' is too strong a * claim -- see the leading-'%' note below.) * * The set is deliberately a little wider than a DNS name: RSYNC_CONNECT_PROG * exists for custom transports, where %H may be an alias the program resolves * itself rather than a name the resolver ever sees, so '+' and '~' are allowed * inside the string.  '%' is required for an IPv6 zone id (fe80::1%eth0) and is * not special to a POSIX shell. * * The first character is checked separately, because several of the allowed * ones change an argument's MEANING rather than its text, which no amount of * quoting prevents.  Mid-word each is literal, which is why the set still * allows them: *   '-' and '+' both introduce options to plenty of programs -- `sh +x` is as *       real as `sh -x`; *   '~' is tilde-expanded by the nested shell, turning ~root into /root; *   '%' is expanded by a nested fish, where %self becomes its pid (an IPv6 *       zone id has its '%' mid-word, so nothing legitimate is lost). * An empty host is refused too: it survives a direct exec as an empty argument * but vanishes entirely when a nested shell re-splits the command, shifting * every argument after it.  None of these can begin a real hostname. * * This bounds what a SHELL can do with the value.  It cannot bound what the * named program does with it -- something like "host:-rf" arrives intact, and a * program that splits on ':' may reinterpret the tail.  That boundary belongs * to whoever writes RSYNC_CONNECT_PROG. */static int shell_unsafe_connect_host(const char *host){	const unsigned char *s; 	if (!*host || strchr("-+~%", *host))		return 1; 	for (s = (const unsigned char *)host; *s; s++) {		if (!((*s >= 'a' && *s <= 'z') || (*s >= 'A' && *s <= 'Z')		 || (*s >= '0' && *s <= '9') || strchr("._:-%+~", *s)))			return 1;	}	return 0;}  /* Try to set the local address for a newly-created socket. * Return -1 if this fails. */int try_bind_local(int s, int ai_family, int ai_socktype,		   const char *bind_addr){	int error;	struct addrinfo bhints, *bres_all, *r; 	memset(&bhints, 0, sizeof bhints);	bhints.ai_family = ai_family;	bhints.ai_socktype = ai_socktype;	bhints.ai_flags = AI_PASSIVE;	if ((error = getaddrinfo(bind_addr, NULL, &bhints, &bres_all))) {		rprintf(FERROR, RSYNC_NAME ": getaddrinfo %s: %s\n",			bind_addr, gai_strerror(error));		return -1;	} 	for (r = bres_all; r; r = r->ai_next) {		if (bind(s, r->ai_addr, r->ai_addrlen) == -1)			continue;		freeaddrinfo(bres_all);		return s;	} 	/* no error message; there might be some problem that allows	 * creation of the socket but not binding, perhaps if the	 * machine has no ipv6 address of this name. */	freeaddrinfo(bres_all);	return -1;} /* connect() timeout handler based on alarm() */static void contimeout_handler(UNUSED(int val)){	connect_timeout = -1;} /* How long each poll() pass waits before re-checking a pending connect(). */#define CONNECT_POLL_SLICE 100 /* connect() to addr, waiting for completion with poll() rather than blocking * in the kernel.  A blocking connect() can sleep forever on a connection that * is already established (seen on OpenBSD, where the socket shows ESTABLISHED * at both ends while connect() never returns); with no timeout set that hangs * rsync for good.  Re-checking the socket on each pass costs a loop instead. * Returns 0 on success, -1 with errno set on failure. */static int connect_polled(int s, const struct sockaddr *addr, socklen_t addrlen){	struct pollfd pfd;	int save_errno; 	set_nonblocking(s); 	if (connect(s, addr, addrlen) == 0)		goto connected;	if (errno != EINPROGRESS && errno != EINTR)		goto failed; 	pfd.fd = s;	pfd.events = POLLOUT;	while (1) {		int err = 0;		socklen_t errlen = sizeof err; 		/* the --contimeout alarm fired: let the caller report it */		if (connect_timeout < 0) {			errno = ETIMEDOUT;			goto failed;		}		pfd.revents = 0;		if (poll(&pfd, 1, CONNECT_POLL_SLICE) < 0) {			if (errno == EINTR)				continue;			goto failed;		}		/* A finished slice is not a failure: loop so that poll() looks		 * at the socket again, which is what recovers a missed wakeup. */		if (!pfd.revents)			continue;		if (getsockopt(s, SOL_SOCKET, SO_ERROR, &err, &errlen) < 0)			goto failed;		if (err) {			errno = err;			goto failed;		}		break;	}  connected:	set_blocking(s);	return 0;  failed:	save_errno = errno;	set_blocking(s);	errno = save_errno;	return -1;} /* Open a socket to a tcp remote host with the specified port. * * Based on code from Warren.  Proxy support by Stephen Rothwell. * getaddrinfo() rewrite contributed by KAME.net. * * Now that we support IPv6 we need to look up the remote machine's address * first, using af_hint to set a preference for the type of address.  Then * depending on whether it has v4 or v6 addresses we try to open a connection. * * The loop allows for machines with some addresses which may not be reachable, * perhaps because we can't e.g. route ipv6 to that network but we can get ip4 * packets through. * * bind_addr: local address to use.  Normally NULL to bind the wildcard address. * * af_hint: address family, e.g. AF_INET or AF_INET6. */int open_socket_out(char *host, int port, const char *bind_addr, int af_hint){	int type = SOCK_STREAM;	int error, s, j, addr_cnt, *errnos;	struct addrinfo hints, *res0, *res;	char portbuf[10];	char *h, *cp;	int proxied = 0;	char buffer[1024];	char *proxy_user = NULL, *proxy_pass = NULL;#ifdef SUPPORT_IDN	char idn_host[1024]; 	/* The resolver only speaks ASCII, so an IDN host goes out as A-labels.	 * An all-ASCII host is passed along untouched. */	if (idn_to_ascii(host, 1, idn_host, sizeof idn_host))		host = idn_host;#endif 	/* if we have a RSYNC_PROXY env variable then redirect our	 * connection via a web proxy at the given address. */	h = getenv("RSYNC_PROXY");	proxied = h != NULL && *h != '\0'; 	if (proxied) {		strlcpy(buffer, h, sizeof buffer); 		/* Is the USER:PASS@ prefix present? */		if ((cp = strrchr(buffer, '@')) != NULL) {			*cp++ = '\0';			/* The remainder is the HOST:PORT part. */			h = cp; 			if ((cp = strchr(buffer, ':')) == NULL) {				rprintf(FERROR,					"invalid proxy specification: should be USER:PASS@HOST:PORT\n");				return -1;			}			*cp++ = '\0'; 			proxy_user = buffer;			proxy_pass = cp;		} else {			/* The whole buffer is the HOST:PORT part. */			h = buffer;		} 		if ((cp = strchr(h, ':')) == NULL) {			rprintf(FERROR,				"invalid proxy specification: should be HOST:PORT\n");			return -1;		}		*cp++ = '\0';		strlcpy(portbuf, cp, sizeof portbuf);		if (DEBUG_GTE(CONNECT, 1)) {			rprintf(FINFO, "connection via http proxy %s port %s\n",				h, portbuf);		}	} else {		snprintf(portbuf, sizeof portbuf, "%d", port);		h = host;	} 	memset(&hints, 0, sizeof hints);	hints.ai_family = af_hint;	hints.ai_socktype = type;	error = getaddrinfo(h, portbuf, &hints, &res0);	if (error) {		rprintf(FERROR, RSYNC_NAME ": getaddrinfo: %s %s: %s\n",			h, portbuf, gai_strerror(error));		return -1;	} 	for (res = res0, addr_cnt = 0; res; res = res->ai_next, addr_cnt++) {}	errnos = new_array0(int, addr_cnt); 	s = -1;	/* Try to connect to all addresses for this machine until we get	 * through.  It might e.g. be multi-homed, or have both IPv4 and IPv6	 * addresses.  We need to create a socket for each record, since the	 * address record tells us what protocol to use to try to connect. */	for (res = res0, j = 0; res; res = res->ai_next, j++) {		s = socket(res->ai_family, res->ai_socktype, res->ai_protocol);		if (s < 0)			continue; 		if (bind_addr		 && try_bind_local(s, res->ai_family, type,				   bind_addr) == -1) {			close(s);			s = -1;			continue;		}		if (connect_timeout > 0) {			SIGACTION(SIGALRM, contimeout_handler);			alarm(connect_timeout);		} 		set_socket_options(s, sockopts);		if (connect_polled(s, res->ai_addr, res->ai_addrlen) < 0) {			if (connect_timeout < 0)				exit_cleanup(RERR_CONTIMEOUT);			/* stash it before close()/alarm() can overwrite errno */			errnos[j] = errno;			close(s);			s = -1;		} 		if (connect_timeout > 0)			alarm(0); 		if (s < 0)			continue; 		if (proxied && establish_proxy_connection(s, host, port, proxy_user, proxy_pass) != 0) {			close(s);			s = -1;			continue;		}		if (DEBUG_GTE(CONNECT, 2)) {			char buf[2048];			if ((error = getnameinfo(res->ai_addr, res->ai_addrlen, buf, sizeof buf, NULL, 0, NI_NUMERICHOST)) != 0)				snprintf(buf, sizeof buf, "*getnameinfo failure: %s*", gai_strerror(error));			rprintf(FINFO, "Connected to %s (%s)\n", h, buf);		}		break;	} 	if (s < 0 || DEBUG_GTE(CONNECT, 2)) {		char buf[2048];		for (res = res0, j = 0; res; res = res->ai_next, j++) {			if (errnos[j] == 0)				continue;			if ((error = getnameinfo(res->ai_addr, res->ai_addrlen, buf, sizeof buf, NULL, 0, NI_NUMERICHOST)) != 0)				snprintf(buf, sizeof buf, "*getnameinfo failure: %s*", gai_strerror(error));			rsyserr(FERROR, errnos[j], "failed to connect to %s (%s)", h, buf);		}		if (s < 0)			s = -1;	} 	freeaddrinfo(res0);	free(errnos); 	return s;}  /* Open an outgoing socket, but allow for it to be intercepted by * $RSYNC_CONNECT_PROG, which will execute a program across a TCP * socketpair rather than really opening a socket. * * We use this primarily in testing to detect TCP flow bugs, but not * cause security problems by really opening remote connections. * * This is based on the Samba LIBSMB_PROG feature. * * bind_addr: local address to use.  Normally NULL to get the stack default. */int open_socket_out_wrapped(char *host, int port, const char *bind_addr, int af_hint){	char *prog = getenv("RSYNC_CONNECT_PROG"); 	if (prog && strchr(prog, '%')) {		if (shell_unsafe_connect_host(host)) {			rprintf(FERROR, "unsafe host characters for RSYNC_CONNECT_PROG\n");

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