557 lines
14 KiB
C
557 lines
14 KiB
C
/*
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* Copyright (c) 2000 Markus Friedl. All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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*
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* THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
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* IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
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* OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
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* IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
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* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
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* NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
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* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
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* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
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* THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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*/
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#include "includes.h"
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RCSID("$OpenBSD: auth.c,v 1.48 2003/06/02 09:17:34 markus Exp $");
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#ifdef HAVE_LOGIN_H
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#include <login.h>
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#endif
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#if defined(HAVE_SHADOW_H) && !defined(DISABLE_SHADOW)
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#include <shadow.h>
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#endif /* defined(HAVE_SHADOW_H) && !defined(DISABLE_SHADOW) */
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#ifdef HAVE_LIBGEN_H
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#include <libgen.h>
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#endif
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#include "xmalloc.h"
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#include "match.h"
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#include "groupaccess.h"
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#include "log.h"
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#include "servconf.h"
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#include "auth.h"
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#include "auth-options.h"
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#include "canohost.h"
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#include "buffer.h"
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#include "bufaux.h"
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#include "uidswap.h"
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#include "tildexpand.h"
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#include "misc.h"
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#include "bufaux.h"
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#include "packet.h"
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/* import */
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extern ServerOptions options;
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extern Buffer loginmsg;
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/* Debugging messages */
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Buffer auth_debug;
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int auth_debug_init;
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/*
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* Check if the user is allowed to log in via ssh. If user is listed
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* in DenyUsers or one of user's groups is listed in DenyGroups, false
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* will be returned. If AllowUsers isn't empty and user isn't listed
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* there, or if AllowGroups isn't empty and one of user's groups isn't
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* listed there, false will be returned.
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* If the user's shell is not executable, false will be returned.
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* Otherwise true is returned.
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*/
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int
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allowed_user(struct passwd * pw)
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{
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struct stat st;
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const char *hostname = NULL, *ipaddr = NULL;
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char *shell;
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int i;
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#if defined(HAVE_SHADOW_H) && !defined(DISABLE_SHADOW) && \
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defined(HAS_SHADOW_EXPIRE)
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struct spwd *spw;
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time_t today;
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#endif
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/* Shouldn't be called if pw is NULL, but better safe than sorry... */
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if (!pw || !pw->pw_name)
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return 0;
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#if defined(HAVE_SHADOW_H) && !defined(DISABLE_SHADOW) && \
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defined(HAS_SHADOW_EXPIRE)
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#define DAY (24L * 60 * 60) /* 1 day in seconds */
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if (!options.use_pam && (spw = getspnam(pw->pw_name)) != NULL) {
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today = time(NULL) / DAY;
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debug3("allowed_user: today %d sp_expire %d sp_lstchg %d"
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" sp_max %d", (int)today, (int)spw->sp_expire,
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(int)spw->sp_lstchg, (int)spw->sp_max);
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/*
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* We assume account and password expiration occurs the
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* day after the day specified.
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*/
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if (spw->sp_expire != -1 && today > spw->sp_expire) {
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logit("Account %.100s has expired", pw->pw_name);
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return 0;
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}
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if (spw->sp_lstchg == 0) {
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logit("User %.100s password has expired (root forced)",
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pw->pw_name);
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return 0;
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}
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if (spw->sp_max != -1 &&
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today > spw->sp_lstchg + spw->sp_max) {
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logit("User %.100s password has expired (password aged)",
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pw->pw_name);
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return 0;
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}
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}
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#endif
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/*
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* Get the shell from the password data. An empty shell field is
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* legal, and means /bin/sh.
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*/
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shell = (pw->pw_shell[0] == '\0') ? _PATH_BSHELL : pw->pw_shell;
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/* deny if shell does not exists or is not executable */
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if (stat(shell, &st) != 0) {
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logit("User %.100s not allowed because shell %.100s does not exist",
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pw->pw_name, shell);
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return 0;
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}
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if (S_ISREG(st.st_mode) == 0 ||
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(st.st_mode & (S_IXOTH|S_IXUSR|S_IXGRP)) == 0) {
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logit("User %.100s not allowed because shell %.100s is not executable",
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pw->pw_name, shell);
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return 0;
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}
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if (options.num_deny_users > 0 || options.num_allow_users > 0) {
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hostname = get_canonical_hostname(options.use_dns);
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ipaddr = get_remote_ipaddr();
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}
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/* Return false if user is listed in DenyUsers */
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if (options.num_deny_users > 0) {
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for (i = 0; i < options.num_deny_users; i++)
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if (match_user(pw->pw_name, hostname, ipaddr,
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options.deny_users[i])) {
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logit("User %.100s not allowed because listed in DenyUsers",
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pw->pw_name);
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return 0;
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}
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}
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/* Return false if AllowUsers isn't empty and user isn't listed there */
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if (options.num_allow_users > 0) {
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for (i = 0; i < options.num_allow_users; i++)
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if (match_user(pw->pw_name, hostname, ipaddr,
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options.allow_users[i]))
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break;
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/* i < options.num_allow_users iff we break for loop */
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if (i >= options.num_allow_users) {
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logit("User %.100s not allowed because not listed in AllowUsers",
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pw->pw_name);
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return 0;
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}
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}
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if (options.num_deny_groups > 0 || options.num_allow_groups > 0) {
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/* Get the user's group access list (primary and supplementary) */
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if (ga_init(pw->pw_name, pw->pw_gid) == 0) {
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logit("User %.100s not allowed because not in any group",
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pw->pw_name);
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return 0;
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}
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/* Return false if one of user's groups is listed in DenyGroups */
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if (options.num_deny_groups > 0)
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if (ga_match(options.deny_groups,
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options.num_deny_groups)) {
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ga_free();
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logit("User %.100s not allowed because a group is listed in DenyGroups",
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pw->pw_name);
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return 0;
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}
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/*
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* Return false if AllowGroups isn't empty and one of user's groups
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* isn't listed there
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*/
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if (options.num_allow_groups > 0)
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if (!ga_match(options.allow_groups,
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options.num_allow_groups)) {
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ga_free();
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logit("User %.100s not allowed because none of user's groups are listed in AllowGroups",
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pw->pw_name);
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return 0;
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}
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ga_free();
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}
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#ifdef WITH_AIXAUTHENTICATE
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/*
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* Don't check loginrestrictions() for root account (use
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* PermitRootLogin to control logins via ssh), or if running as
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* non-root user (since loginrestrictions will always fail).
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*/
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if ((pw->pw_uid != 0) && (geteuid() == 0)) {
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char *msg;
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if (loginrestrictions(pw->pw_name, S_RLOGIN, NULL, &msg) != 0) {
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int loginrestrict_errno = errno;
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if (msg && *msg) {
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buffer_append(&loginmsg, msg, strlen(msg));
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aix_remove_embedded_newlines(msg);
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logit("Login restricted for %s: %.100s",
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pw->pw_name, msg);
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}
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/* Don't fail if /etc/nologin set */
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if (!(loginrestrict_errno == EPERM &&
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stat(_PATH_NOLOGIN, &st) == 0))
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return 0;
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}
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}
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#endif /* WITH_AIXAUTHENTICATE */
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/* We found no reason not to let this user try to log on... */
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return 1;
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}
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Authctxt *
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authctxt_new(void)
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{
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Authctxt *authctxt = xmalloc(sizeof(*authctxt));
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memset(authctxt, 0, sizeof(*authctxt));
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return authctxt;
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}
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void
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auth_log(Authctxt *authctxt, int authenticated, char *method, char *info)
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{
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void (*authlog) (const char *fmt,...) = verbose;
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char *authmsg;
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/* Raise logging level */
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if (authenticated == 1 ||
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!authctxt->valid ||
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authctxt->failures >= AUTH_FAIL_LOG ||
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strcmp(method, "password") == 0)
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authlog = logit;
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if (authctxt->postponed)
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authmsg = "Postponed";
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else
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authmsg = authenticated ? "Accepted" : "Failed";
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authlog("%s %s for %s%.100s from %.200s port %d%s",
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authmsg,
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method,
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authctxt->valid ? "" : "illegal user ",
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authctxt->user,
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get_remote_ipaddr(),
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get_remote_port(),
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info);
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#ifdef CUSTOM_FAILED_LOGIN
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if (authenticated == 0 && strcmp(method, "password") == 0)
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record_failed_login(authctxt->user, "ssh");
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#endif
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}
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/*
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* Check whether root logins are disallowed.
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*/
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int
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auth_root_allowed(char *method)
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{
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switch (options.permit_root_login) {
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case PERMIT_YES:
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return 1;
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break;
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case PERMIT_NO_PASSWD:
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if (strcmp(method, "password") != 0)
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return 1;
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break;
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case PERMIT_FORCED_ONLY:
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if (forced_command) {
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logit("Root login accepted for forced command.");
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return 1;
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}
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break;
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}
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logit("ROOT LOGIN REFUSED FROM %.200s", get_remote_ipaddr());
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return 0;
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}
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/*
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* Given a template and a passwd structure, build a filename
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* by substituting % tokenised options. Currently, %% becomes '%',
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* %h becomes the home directory and %u the username.
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*
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* This returns a buffer allocated by xmalloc.
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*/
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char *
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expand_filename(const char *filename, struct passwd *pw)
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{
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Buffer buffer;
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char *file;
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const char *cp;
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/*
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* Build the filename string in the buffer by making the appropriate
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* substitutions to the given file name.
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*/
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buffer_init(&buffer);
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for (cp = filename; *cp; cp++) {
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if (cp[0] == '%' && cp[1] == '%') {
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buffer_append(&buffer, "%", 1);
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cp++;
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continue;
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}
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if (cp[0] == '%' && cp[1] == 'h') {
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buffer_append(&buffer, pw->pw_dir, strlen(pw->pw_dir));
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cp++;
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continue;
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}
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if (cp[0] == '%' && cp[1] == 'u') {
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buffer_append(&buffer, pw->pw_name,
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strlen(pw->pw_name));
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cp++;
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continue;
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}
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buffer_append(&buffer, cp, 1);
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}
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buffer_append(&buffer, "\0", 1);
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/*
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* Ensure that filename starts anchored. If not, be backward
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* compatible and prepend the '%h/'
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*/
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file = xmalloc(MAXPATHLEN);
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cp = buffer_ptr(&buffer);
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if (*cp != '/')
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snprintf(file, MAXPATHLEN, "%s/%s", pw->pw_dir, cp);
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else
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strlcpy(file, cp, MAXPATHLEN);
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buffer_free(&buffer);
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return file;
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}
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char *
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authorized_keys_file(struct passwd *pw)
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{
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return expand_filename(options.authorized_keys_file, pw);
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}
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char *
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authorized_keys_file2(struct passwd *pw)
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{
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return expand_filename(options.authorized_keys_file2, pw);
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}
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/* return ok if key exists in sysfile or userfile */
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HostStatus
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check_key_in_hostfiles(struct passwd *pw, Key *key, const char *host,
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const char *sysfile, const char *userfile)
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{
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Key *found;
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char *user_hostfile;
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struct stat st;
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HostStatus host_status;
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/* Check if we know the host and its host key. */
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found = key_new(key->type);
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host_status = check_host_in_hostfile(sysfile, host, key, found, NULL);
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if (host_status != HOST_OK && userfile != NULL) {
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user_hostfile = tilde_expand_filename(userfile, pw->pw_uid);
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if (options.strict_modes &&
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(stat(user_hostfile, &st) == 0) &&
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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("Authentication refused for %.100s: "
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"bad owner or modes for %.200s",
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pw->pw_name, user_hostfile);
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} else {
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temporarily_use_uid(pw);
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host_status = check_host_in_hostfile(user_hostfile,
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host, key, found, NULL);
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restore_uid();
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}
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xfree(user_hostfile);
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}
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key_free(found);
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debug2("check_key_in_hostfiles: key %s for %s", host_status == HOST_OK ?
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"ok" : "not found", host);
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return host_status;
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}
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/*
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* Check a given file for security. This is defined as all components
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* of the path to the file must be owned by either the owner of
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* of the file or root and no directories must be group or world writable.
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*
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* XXX Should any specific check be done for sym links ?
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*
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* Takes an open file descriptor, the file name, a uid and and
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* error buffer plus max size as arguments.
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*
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* Returns 0 on success and -1 on failure
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*/
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int
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secure_filename(FILE *f, const char *file, struct passwd *pw,
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char *err, size_t errlen)
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{
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uid_t uid = pw->pw_uid;
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char buf[MAXPATHLEN], homedir[MAXPATHLEN];
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char *cp;
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int comparehome = 0;
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struct stat st;
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if (realpath(file, buf) == NULL) {
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snprintf(err, errlen, "realpath %s failed: %s", file,
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strerror(errno));
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return -1;
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}
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if (realpath(pw->pw_dir, homedir) != NULL)
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comparehome = 1;
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/* check the open file to avoid races */
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if (fstat(fileno(f), &st) < 0 ||
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(st.st_uid != 0 && st.st_uid != uid) ||
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(st.st_mode & 022) != 0) {
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snprintf(err, errlen, "bad ownership or modes for file %s",
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buf);
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return -1;
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}
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/* for each component of the canonical path, walking upwards */
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for (;;) {
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if ((cp = dirname(buf)) == NULL) {
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snprintf(err, errlen, "dirname() failed");
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return -1;
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}
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strlcpy(buf, cp, sizeof(buf));
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debug3("secure_filename: checking '%s'", buf);
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if (stat(buf, &st) < 0 ||
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(st.st_uid != 0 && st.st_uid != uid) ||
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(st.st_mode & 022) != 0) {
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snprintf(err, errlen,
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"bad ownership or modes for directory %s", buf);
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return -1;
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}
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/* If are passed the homedir then we can stop */
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if (comparehome && strcmp(homedir, buf) == 0) {
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debug3("secure_filename: terminating check at '%s'",
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buf);
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break;
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}
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/*
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* dirname should always complete with a "/" path,
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* but we can be paranoid and check for "." too
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*/
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if ((strcmp("/", buf) == 0) || (strcmp(".", buf) == 0))
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break;
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}
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return 0;
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}
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struct passwd *
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getpwnamallow(const char *user)
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{
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#ifdef HAVE_LOGIN_CAP
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extern login_cap_t *lc;
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#ifdef BSD_AUTH
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auth_session_t *as;
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#endif
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#endif
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struct passwd *pw;
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pw = getpwnam(user);
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if (pw == NULL) {
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logit("Illegal user %.100s from %.100s",
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user, get_remote_ipaddr());
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#ifdef CUSTOM_FAILED_LOGIN
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record_failed_login(user, "ssh");
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#endif
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return (NULL);
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}
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if (!allowed_user(pw))
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return (NULL);
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#ifdef HAVE_LOGIN_CAP
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if ((lc = login_getclass(pw->pw_class)) == NULL) {
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debug("unable to get login class: %s", user);
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return (NULL);
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}
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#ifdef BSD_AUTH
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if ((as = auth_open()) == NULL || auth_setpwd(as, pw) != 0 ||
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auth_approval(as, lc, pw->pw_name, "ssh") <= 0) {
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debug("Approval failure for %s", user);
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pw = NULL;
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}
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if (as != NULL)
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auth_close(as);
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#endif
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#endif
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if (pw != NULL)
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return (pwcopy(pw));
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return (NULL);
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}
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void
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|
auth_debug_add(const char *fmt,...)
|
|
{
|
|
char buf[1024];
|
|
va_list args;
|
|
|
|
if (!auth_debug_init)
|
|
return;
|
|
|
|
va_start(args, fmt);
|
|
vsnprintf(buf, sizeof(buf), fmt, args);
|
|
va_end(args);
|
|
buffer_put_cstring(&auth_debug, buf);
|
|
}
|
|
|
|
void
|
|
auth_debug_send(void)
|
|
{
|
|
char *msg;
|
|
|
|
if (!auth_debug_init)
|
|
return;
|
|
while (buffer_len(&auth_debug)) {
|
|
msg = buffer_get_string(&auth_debug, NULL);
|
|
packet_send_debug("%s", msg);
|
|
xfree(msg);
|
|
}
|
|
}
|
|
|
|
void
|
|
auth_debug_reset(void)
|
|
{
|
|
if (auth_debug_init)
|
|
buffer_clear(&auth_debug);
|
|
else {
|
|
buffer_init(&auth_debug);
|
|
auth_debug_init = 1;
|
|
}
|
|
}
|