GCC Code Coverage Report
Directory: ./ Exec Total Coverage
File: usr.bin/ssh/sshd/../auth-rhosts.c Lines: 0 127 0.0 %
Date: 2017-11-13 Branches: 0 101 0.0 %

Line Branch Exec Source
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/* $OpenBSD: auth-rhosts.c,v 1.48 2016/08/13 17:47:41 markus Exp $ */
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/*
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 * Author: Tatu Ylonen <ylo@cs.hut.fi>
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 * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
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 *                    All rights reserved
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 * Rhosts authentication.  This file contains code to check whether to admit
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 * the login based on rhosts authentication.  This file also processes
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 * /etc/hosts.equiv.
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 *
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 * As far as I am concerned, the code I have written for this software
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 * can be used freely for any purpose.  Any derived versions of this
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 * software must be clearly marked as such, and if the derived work is
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 * incompatible with the protocol description in the RFC file, it must be
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 * called by a name other than "ssh" or "Secure Shell".
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 */
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#include <sys/types.h>
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#include <sys/stat.h>
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#include <fcntl.h>
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#include <netgroup.h>
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#include <pwd.h>
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#include <stdio.h>
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#include <string.h>
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#include <stdarg.h>
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#include <unistd.h>
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#include "packet.h"
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#include "uidswap.h"
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#include "pathnames.h"
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#include "log.h"
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#include "misc.h"
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#include "buffer.h" /* XXX */
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#include "key.h" /* XXX */
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#include "servconf.h"
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#include "canohost.h"
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#include "sshkey.h"
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#include "hostfile.h"
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#include "auth.h"
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/* import */
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extern ServerOptions options;
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extern int use_privsep;
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/*
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 * This function processes an rhosts-style file (.rhosts, .shosts, or
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 * /etc/hosts.equiv).  This returns true if authentication can be granted
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 * based on the file, and returns zero otherwise.
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 */
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static int
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check_rhosts_file(const char *filename, const char *hostname,
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		  const char *ipaddr, const char *client_user,
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		  const char *server_user)
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{
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	FILE *f;
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#define RBUFLN 1024
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	char buf[RBUFLN];/* Must not be larger than host, user, dummy below. */
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	int fd;
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	struct stat st;
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	/* Open the .rhosts file, deny if unreadable */
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	if ((fd = open(filename, O_RDONLY|O_NONBLOCK)) == -1)
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		return 0;
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	if (fstat(fd, &st) == -1) {
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		close(fd);
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		return 0;
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	}
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	if (!S_ISREG(st.st_mode)) {
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		logit("User %s hosts file %s is not a regular file",
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		    server_user, filename);
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		close(fd);
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		return 0;
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	}
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	unset_nonblock(fd);
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	if ((f = fdopen(fd, "r")) == NULL) {
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		close(fd);
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		return 0;
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	}
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	while (fgets(buf, sizeof(buf), f)) {
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		/* All three must have length >= buf to avoid overflows. */
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		char hostbuf[RBUFLN], userbuf[RBUFLN], dummy[RBUFLN];
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		char *host, *user, *cp;
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		int negated;
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		for (cp = buf; *cp == ' ' || *cp == '\t'; cp++)
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			;
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		if (*cp == '#' || *cp == '\n' || !*cp)
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			continue;
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		/*
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		 * NO_PLUS is supported at least on OSF/1.  We skip it (we
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		 * don't ever support the plus syntax).
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		 */
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		if (strncmp(cp, "NO_PLUS", 7) == 0)
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			continue;
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		/*
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		 * This should be safe because each buffer is as big as the
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		 * whole string, and thus cannot be overwritten.
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		 */
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		switch (sscanf(buf, "%1023s %1023s %1023s", hostbuf, userbuf,
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		    dummy)) {
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		case 0:
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			auth_debug_add("Found empty line in %.100s.", filename);
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			continue;
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		case 1:
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			/* Host name only. */
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			strlcpy(userbuf, server_user, sizeof(userbuf));
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			break;
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		case 2:
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			/* Got both host and user name. */
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			break;
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		case 3:
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			auth_debug_add("Found garbage in %.100s.", filename);
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			continue;
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		default:
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			/* Weird... */
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			continue;
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		}
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		host = hostbuf;
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		user = userbuf;
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		negated = 0;
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		/* Process negated host names, or positive netgroups. */
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		if (host[0] == '-') {
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			negated = 1;
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			host++;
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		} else if (host[0] == '+')
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			host++;
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		if (user[0] == '-') {
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			negated = 1;
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			user++;
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		} else if (user[0] == '+')
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			user++;
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		/* Check for empty host/user names (particularly '+'). */
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		if (!host[0] || !user[0]) {
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			/* We come here if either was '+' or '-'. */
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			auth_debug_add("Ignoring wild host/user names "
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			    "in %.100s.", filename);
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			continue;
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		}
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		/* Verify that host name matches. */
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		if (host[0] == '@') {
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			if (!innetgr(host + 1, hostname, NULL, NULL) &&
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			    !innetgr(host + 1, ipaddr, NULL, NULL))
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				continue;
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		} else if (strcasecmp(host, hostname) &&
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		    strcmp(host, ipaddr) != 0)
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			continue;	/* Different hostname. */
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		/* Verify that user name matches. */
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		if (user[0] == '@') {
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			if (!innetgr(user + 1, NULL, client_user, NULL))
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				continue;
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		} else if (strcmp(user, client_user) != 0)
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			continue;	/* Different username. */
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		/* Found the user and host. */
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		fclose(f);
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		/* If the entry was negated, deny access. */
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		if (negated) {
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			auth_debug_add("Matched negative entry in %.100s.",
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			    filename);
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			return 0;
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		}
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		/* Accept authentication. */
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		return 1;
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	}
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	/* Authentication using this file denied. */
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	fclose(f);
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	return 0;
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}
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/*
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 * Tries to authenticate the user using the .shosts or .rhosts file. Returns
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 * true if authentication succeeds.  If ignore_rhosts is true, only
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 * /etc/hosts.equiv will be considered (.rhosts and .shosts are ignored).
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 */
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int
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auth_rhosts2(struct passwd *pw, const char *client_user, const char *hostname,
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    const char *ipaddr)
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{
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	char buf[1024];
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	struct stat st;
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	static const char *rhosts_files[] = {".shosts", ".rhosts", NULL};
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	u_int rhosts_file_index;
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	debug2("auth_rhosts2: clientuser %s hostname %s ipaddr %s",
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	    client_user, hostname, ipaddr);
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	/* Switch to the user's uid. */
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	temporarily_use_uid(pw);
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	/*
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	 * Quick check: if the user has no .shosts or .rhosts files and
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	 * no system hosts.equiv/shosts.equiv files exist then return
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	 * failure immediately without doing costly lookups from name
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	 * servers.
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	 */
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	for (rhosts_file_index = 0; rhosts_files[rhosts_file_index];
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	    rhosts_file_index++) {
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		/* Check users .rhosts or .shosts. */
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		snprintf(buf, sizeof buf, "%.500s/%.100s",
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			 pw->pw_dir, rhosts_files[rhosts_file_index]);
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		if (stat(buf, &st) >= 0)
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			break;
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	}
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	/* Switch back to privileged uid. */
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	restore_uid();
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	/*
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	 * Deny if The user has no .shosts or .rhosts file and there
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	 * are no system-wide files.
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	 */
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	if (!rhosts_files[rhosts_file_index] &&
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	    stat(_PATH_RHOSTS_EQUIV, &st) < 0 &&
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	    stat(_PATH_SSH_HOSTS_EQUIV, &st) < 0) {
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		debug3("%s: no hosts access files exist", __func__);
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		return 0;
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	}
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	/*
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	 * If not logging in as superuser, try /etc/hosts.equiv and
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	 * shosts.equiv.
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	 */
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	if (pw->pw_uid == 0)
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		debug3("%s: root user, ignoring system hosts files", __func__);
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	else {
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		if (check_rhosts_file(_PATH_RHOSTS_EQUIV, hostname, ipaddr,
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		    client_user, pw->pw_name)) {
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			auth_debug_add("Accepted for %.100s [%.100s] by "
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			    "/etc/hosts.equiv.", hostname, ipaddr);
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			return 1;
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		}
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		if (check_rhosts_file(_PATH_SSH_HOSTS_EQUIV, hostname, ipaddr,
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		    client_user, pw->pw_name)) {
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			auth_debug_add("Accepted for %.100s [%.100s] by "
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			    "%.100s.", hostname, ipaddr, _PATH_SSH_HOSTS_EQUIV);
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			return 1;
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		}
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	}
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	/*
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	 * Check that the home directory is owned by root or the user, and is
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	 * not group or world writable.
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	 */
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	if (stat(pw->pw_dir, &st) < 0) {
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		logit("Rhosts authentication refused for %.100s: "
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		    "no home directory %.200s", pw->pw_name, pw->pw_dir);
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		auth_debug_add("Rhosts authentication refused for %.100s: "
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		    "no home directory %.200s", pw->pw_name, pw->pw_dir);
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		return 0;
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	}
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	if (options.strict_modes &&
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	    ((st.st_uid != 0 && st.st_uid != pw->pw_uid) ||
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	    (st.st_mode & 022) != 0)) {
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		logit("Rhosts authentication refused for %.100s: "
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		    "bad ownership or modes for home directory.", pw->pw_name);
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		auth_debug_add("Rhosts authentication refused for %.100s: "
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		    "bad ownership or modes for home directory.", pw->pw_name);
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		return 0;
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	}
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	/* Temporarily use the user's uid. */
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	temporarily_use_uid(pw);
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	/* Check all .rhosts files (currently .shosts and .rhosts). */
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	for (rhosts_file_index = 0; rhosts_files[rhosts_file_index];
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	    rhosts_file_index++) {
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		/* Check users .rhosts or .shosts. */
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		snprintf(buf, sizeof buf, "%.500s/%.100s",
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			 pw->pw_dir, rhosts_files[rhosts_file_index]);
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		if (stat(buf, &st) < 0)
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			continue;
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		/*
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		 * Make sure that the file is either owned by the user or by
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		 * root, and make sure it is not writable by anyone but the
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		 * owner.  This is to help avoid novices accidentally
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		 * allowing access to their account by anyone.
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		 */
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		if (options.strict_modes &&
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		    ((st.st_uid != 0 && st.st_uid != pw->pw_uid) ||
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		    (st.st_mode & 022) != 0)) {
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			logit("Rhosts authentication refused for %.100s: bad modes for %.200s",
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			    pw->pw_name, buf);
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			auth_debug_add("Bad file modes for %.200s", buf);
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			continue;
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		}
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		/*
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		 * Check if we have been configured to ignore .rhosts
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		 * and .shosts files.
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		 */
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		if (options.ignore_rhosts) {
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			auth_debug_add("Server has been configured to "
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			    "ignore %.100s.", rhosts_files[rhosts_file_index]);
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			continue;
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		}
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		/* Check if authentication is permitted by the file. */
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		if (check_rhosts_file(buf, hostname, ipaddr,
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		    client_user, pw->pw_name)) {
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			auth_debug_add("Accepted by %.100s.",
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			    rhosts_files[rhosts_file_index]);
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			/* Restore the privileged uid. */
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			restore_uid();
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			auth_debug_add("Accepted host %s ip %s client_user "
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			    "%s server_user %s", hostname, ipaddr,
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			    client_user, pw->pw_name);
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			return 1;
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		}
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	}
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	/* Restore the privileged uid. */
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	restore_uid();
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	return 0;
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}