source: trunk/third/openssh/auth.c @ 18763

/*
 * Copyright (c) 2000 Markus Friedl.  All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

#include "includes.h"
RCSID("$OpenBSD: auth.c,v 1.45 2002/09/20 18:41:29 stevesk Exp $");

#ifdef HAVE_LOGIN_H
#include <login.h>
#endif
#if defined(HAVE_SHADOW_H) && !defined(DISABLE_SHADOW)
#include <shadow.h>
#endif /* defined(HAVE_SHADOW_H) && !defined(DISABLE_SHADOW) */

#ifdef HAVE_LIBGEN_H
#include <libgen.h>
#endif

#include <al.h>
char *session_username;
int is_local_acct;

#include "xmalloc.h"
#include "match.h"
#include "groupaccess.h"
#include "log.h"
#include "servconf.h"
#include "auth.h"
#include "auth-options.h"
#include "canohost.h"
#include "buffer.h"
#include "bufaux.h"
#include "uidswap.h"
#include "tildexpand.h"
#include "misc.h"
#include "bufaux.h"
#include "packet.h"

/* import */
extern ServerOptions options;

/* Debugging messages */
Buffer auth_debug;
int auth_debug_init;

/*
 * Check if the user is allowed to log in via ssh. If user is listed
 * in DenyUsers or one of user's groups is listed in DenyGroups, false
 * will be returned. If AllowUsers isn't empty and user isn't listed
 * there, or if AllowGroups isn't empty and one of user's groups isn't
 * listed there, false will be returned.
 * If the user's shell is not executable, false will be returned.
 * Otherwise true is returned.
 */
int
allowed_user(struct passwd * pw)
{
        struct stat st;
        const char *hostname = NULL, *ipaddr = NULL;
        char *shell;
        int i;
#ifdef WITH_AIXAUTHENTICATE
        char *loginmsg;
#endif /* WITH_AIXAUTHENTICATE */
#if !defined(USE_PAM) && defined(HAVE_SHADOW_H) && \
        !defined(DISABLE_SHADOW) && defined(HAS_SHADOW_EXPIRE)
        struct spwd *spw;

        /* Shouldn't be called if pw is NULL, but better safe than sorry... */
        if (!pw || !pw->pw_name)
                return 0;

#define DAY             (24L * 60 * 60) /* 1 day in seconds */
        spw = getspnam(pw->pw_name);
        if (spw != NULL) {
                time_t today = time(NULL) / DAY;
                debug3("allowed_user: today %d sp_expire %d sp_lstchg %d"
                    " sp_max %d", (int)today, (int)spw->sp_expire,
                    (int)spw->sp_lstchg, (int)spw->sp_max);

                /*
                 * We assume account and password expiration occurs the
                 * day after the day specified.
                 */
                if (spw->sp_expire != -1 && today > spw->sp_expire) {
                        log("Account %.100s has expired", pw->pw_name);
                        return 0;
                }

                if (spw->sp_lstchg == 0) {
                        log("User %.100s password has expired (root forced)",
                            pw->pw_name);
                        return 0;
                }

                if (spw->sp_max != -1 &&
                    today > spw->sp_lstchg + spw->sp_max) {
                        log("User %.100s password has expired (password aged)",
                            pw->pw_name);
                        return 0;
                }
        }
#else
        /* Shouldn't be called if pw is NULL, but better safe than sorry... */
        if (!pw || !pw->pw_name)
                return 0;
#endif

        /*
         * Get the shell from the password data.  An empty shell field is
         * legal, and means /bin/sh.
         */
        shell = (pw->pw_shell[0] == '\0') ? _PATH_BSHELL : pw->pw_shell;

        /* deny if shell does not exists or is not executable */
        if (stat(shell, &st) != 0) {
                log("User %.100s not allowed because shell %.100s does not exist",
                    pw->pw_name, shell);
                return 0;
        }
        if (S_ISREG(st.st_mode) == 0 ||
            (st.st_mode & (S_IXOTH|S_IXUSR|S_IXGRP)) == 0) {
                log("User %.100s not allowed because shell %.100s is not executable",
                    pw->pw_name, shell);
                return 0;
        }

        if (options.num_deny_users > 0 || options.num_allow_users > 0) {
                hostname = get_canonical_hostname(options.verify_reverse_mapping);
                ipaddr = get_remote_ipaddr();
        }

        /* Return false if user is listed in DenyUsers */
        if (options.num_deny_users > 0) {
                for (i = 0; i < options.num_deny_users; i++)
                        if (match_user(pw->pw_name, hostname, ipaddr,
                            options.deny_users[i])) {
                                log("User %.100s not allowed because listed in DenyUsers",
                                    pw->pw_name);
                                return 0;
                        }
        }
        /* Return false if AllowUsers isn't empty and user isn't listed there */
        if (options.num_allow_users > 0) {
                for (i = 0; i < options.num_allow_users; i++)
                        if (match_user(pw->pw_name, hostname, ipaddr,
                            options.allow_users[i]))
                                break;
                /* i < options.num_allow_users iff we break for loop */
                if (i >= options.num_allow_users) {
                        log("User %.100s not allowed because not listed in AllowUsers",
                            pw->pw_name);
                        return 0;
                }
        }
        if (options.num_deny_groups > 0 || options.num_allow_groups > 0) {
                /* Get the user's group access list (primary and supplementary) */
                if (ga_init(pw->pw_name, pw->pw_gid) == 0) {
                        log("User %.100s not allowed because not in any group",
                            pw->pw_name);
                        return 0;
                }

                /* Return false if one of user's groups is listed in DenyGroups */
                if (options.num_deny_groups > 0)
                        if (ga_match(options.deny_groups,
                            options.num_deny_groups)) {
                                ga_free();
                                log("User %.100s not allowed because a group is listed in DenyGroups",
                                    pw->pw_name);
                                return 0;
                        }
                /*
                 * Return false if AllowGroups isn't empty and one of user's groups
                 * isn't listed there
                 */
                if (options.num_allow_groups > 0)
                        if (!ga_match(options.allow_groups,
                            options.num_allow_groups)) {
                                ga_free();
                                log("User %.100s not allowed because none of user's groups are listed in AllowGroups",
                                    pw->pw_name);
                                return 0;
                        }
                ga_free();
        }

#ifdef WITH_AIXAUTHENTICATE
        if (loginrestrictions(pw->pw_name, S_RLOGIN, NULL, &loginmsg) != 0) {
                if (loginmsg && *loginmsg) {
                        /* Remove embedded newlines (if any) */
                        char *p;
                        for (p = loginmsg; *p; p++) {
                                if (*p == '\n')
                                        *p = ' ';
                        }
                        /* Remove trailing newline */
                        *--p = '\0';
                        log("Login restricted for %s: %.100s", pw->pw_name, loginmsg);
                }
                return 0;
        }
#endif /* WITH_AIXAUTHENTICATE */

        /* We found no reason not to let this user try to log on... */
        return 1;
}

Authctxt *
authctxt_new(void)
{
        Authctxt *authctxt = xmalloc(sizeof(*authctxt));
        memset(authctxt, 0, sizeof(*authctxt));
        return authctxt;
}

void
auth_log(Authctxt *authctxt, int authenticated, char *method, char *info)
{
        void (*authlog) (const char *fmt,...) = verbose;
        char *authmsg;

        /* Raise logging level */
        if (authenticated == 1 ||
            !authctxt->valid ||
            authctxt->failures >= AUTH_FAIL_LOG ||
            strcmp(method, "password") == 0)
                authlog = log;

        if (authctxt->postponed)
                authmsg = "Postponed";
        else
                authmsg = authenticated ? "Accepted" : "Failed";

        authlog("%s %s for %s%.100s from %.200s port %d%s",
            authmsg,
            method,
            authctxt->valid ? "" : "illegal user ",
            authctxt->user,
            get_remote_ipaddr(),
            get_remote_port(),
            info);

#ifdef WITH_AIXAUTHENTICATE
        if (authenticated == 0 && strcmp(method, "password") == 0)
            loginfailed(authctxt->user,
                get_canonical_hostname(options.verify_reverse_mapping),
                "ssh");
#endif /* WITH_AIXAUTHENTICATE */

}

/*
 * Check whether root logins are disallowed.
 */
int
auth_root_allowed(char *method)
{
        switch (options.permit_root_login) {
        case PERMIT_YES:
                return 1;
                break;
        case PERMIT_NO_PASSWD:
                if (strcmp(method, "password") != 0)
                        return 1;
                break;
        case PERMIT_FORCED_ONLY:
                if (forced_command) {
                        log("Root login accepted for forced command.");
                        return 1;
                }
                break;
        }
        log("ROOT LOGIN REFUSED FROM %.200s", get_remote_ipaddr());
        return 0;
}


/*
 * Given a template and a passwd structure, build a filename
 * by substituting % tokenised options. Currently, %% becomes '%',
 * %h becomes the home directory and %u the username.
 *
 * This returns a buffer allocated by xmalloc.
 */
char *
expand_filename(const char *filename, struct passwd *pw)
{
        Buffer buffer;
        char *file;
        const char *cp;

        /*
         * Build the filename string in the buffer by making the appropriate
         * substitutions to the given file name.
         */
        buffer_init(&buffer);
        for (cp = filename; *cp; cp++) {
                if (cp[0] == '%' && cp[1] == '%') {
                        buffer_append(&buffer, "%", 1);
                        cp++;
                        continue;
                }
                if (cp[0] == '%' && cp[1] == 'h') {
                        buffer_append(&buffer, pw->pw_dir, strlen(pw->pw_dir));
                        cp++;
                        continue;
                }
                if (cp[0] == '%' && cp[1] == 'u') {
                        buffer_append(&buffer, pw->pw_name,
                            strlen(pw->pw_name));
                        cp++;
                        continue;
                }
                buffer_append(&buffer, cp, 1);
        }
        buffer_append(&buffer, "\0", 1);

        /*
         * Ensure that filename starts anchored. If not, be backward
         * compatible and prepend the '%h/'
         */
        file = xmalloc(MAXPATHLEN);
        cp = buffer_ptr(&buffer);
        if (*cp != '/')
                snprintf(file, MAXPATHLEN, "%s/%s", pw->pw_dir, cp);
        else
                strlcpy(file, cp, MAXPATHLEN);

        buffer_free(&buffer);
        return file;
}

char *
authorized_keys_file(struct passwd *pw)
{
        return expand_filename(options.authorized_keys_file, pw);
}

char *
authorized_keys_file2(struct passwd *pw)
{
        return expand_filename(options.authorized_keys_file2, pw);
}

/* return ok if key exists in sysfile or userfile */
HostStatus
check_key_in_hostfiles(struct passwd *pw, Key *key, const char *host,
    const char *sysfile, const char *userfile)
{
        Key *found;
        char *user_hostfile;
        struct stat st;
        HostStatus host_status;

        /* Check if we know the host and its host key. */
        found = key_new(key->type);
        host_status = check_host_in_hostfile(sysfile, host, key, found, NULL);

        if (host_status != HOST_OK && userfile != NULL) {
                user_hostfile = tilde_expand_filename(userfile, pw->pw_uid);
                if (options.strict_modes &&
                    (stat(user_hostfile, &st) == 0) &&
                    ((st.st_uid != 0 && st.st_uid != pw->pw_uid) ||
                    (st.st_mode & 022) != 0)) {
                        log("Authentication refused for %.100s: "
                            "bad owner or modes for %.200s",
                            pw->pw_name, user_hostfile);
                } else {
                        temporarily_use_uid(pw);
                        host_status = check_host_in_hostfile(user_hostfile,
                            host, key, found, NULL);
                        restore_uid();
                }
                xfree(user_hostfile);
        }
        key_free(found);

        debug2("check_key_in_hostfiles: key %s for %s", host_status == HOST_OK ?
            "ok" : "not found", host);
        return host_status;
}


/*
 * Check a given file for security. This is defined as all components
 * of the path to the file must be owned by either the owner of
 * of the file or root and no directories must be group or world writable.
 *
 * XXX Should any specific check be done for sym links ?
 *
 * Takes an open file descriptor, the file name, a uid and and
 * error buffer plus max size as arguments.
 *
 * Returns 0 on success and -1 on failure
 */
int
secure_filename(FILE *f, const char *file, struct passwd *pw,
    char *err, size_t errlen)
{
        uid_t uid = pw->pw_uid;
        char buf[MAXPATHLEN], homedir[MAXPATHLEN];
        char *cp;
        struct stat st;

        if (realpath(file, buf) == NULL) {
                snprintf(err, errlen, "realpath %s failed: %s", file,
                    strerror(errno));
                return -1;
        }
        if (realpath(pw->pw_dir, homedir) == NULL) {
                snprintf(err, errlen, "realpath %s failed: %s", pw->pw_dir,
                    strerror(errno));
                return -1;
        }

        /* check the open file to avoid races */
        if (fstat(fileno(f), &st) < 0 ||
            (st.st_uid != 0 && st.st_uid != uid) ||
            (st.st_mode & 022) != 0) {
                snprintf(err, errlen, "bad ownership or modes for file %s",
                    buf);
                return -1;
        }

        /* for each component of the canonical path, walking upwards */
        for (;;) {
                if ((cp = dirname(buf)) == NULL) {
                        snprintf(err, errlen, "dirname() failed");
                        return -1;
                }
                strlcpy(buf, cp, sizeof(buf));

                debug3("secure_filename: checking '%s'", buf);
                if (stat(buf, &st) < 0 ||
                    (st.st_uid != 0 && st.st_uid != uid) ||
                    (st.st_mode & 022) != 0) {
                        snprintf(err, errlen,
                            "bad ownership or modes for directory %s", buf);
                        return -1;
                }

                /* If are passed the homedir then we can stop */
                if (strcmp(homedir, buf) == 0) {
                        debug3("secure_filename: terminating check at '%s'",
                            buf);
                        break;
                }
                /*
                 * dirname should always complete with a "/" path,
                 * but we can be paranoid and check for "." too
                 */
                if ((strcmp("/", buf) == 0) || (strcmp(".", buf) == 0))
                        break;
        }
        return 0;
}

void session_cleanup(void)
{
  al_acct_revert(session_username, getpid());
}

struct passwd *
getpwnamallow(const char *user)
{
#ifdef HAVE_LOGIN_CAP
        extern login_cap_t *lc;
#ifdef BSD_AUTH
        auth_session_t *as;
#endif
#endif
        struct passwd *pw;

        pw = getpwnam(user);
        if (pw == NULL) {
                log("Illegal user %.100s from %.100s",
                    user, get_remote_ipaddr());
                return (NULL);
        }
        if (!allowed_user(pw))
                return (NULL);
#ifdef HAVE_LOGIN_CAP
        if ((lc = login_getclass(pw->pw_class)) == NULL) {
                debug("unable to get login class: %s", user);
                return (NULL);
        }
#ifdef BSD_AUTH
        if ((as = auth_open()) == NULL || auth_setpwd(as, pw) != 0 ||
            auth_approval(as, lc, pw->pw_name, "ssh") <= 0) {
                debug("Approval failure for %s", user);
                pw = NULL;
        }
        if (as != NULL)
                auth_close(as);
#endif
#endif
        if (pw != NULL)
                return (pwcopy(pw));
        return (NULL);
}

void
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;
        }
}