/*      $NetBSD: su.c,v 1.75 2023/03/24 16:58:24 kre Exp $      */

/*
 * Copyright (c) 1988 The Regents of the University of California.
 * 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.
 * 3. Neither the name of the University nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``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 REGENTS OR CONTRIBUTORS 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 <sys/cdefs.h>
#ifndef lint
__COPYRIGHT("@(#) Copyright (c) 1988\
 The Regents of the University of California.  All rights reserved.");
#endif /* not lint */

#ifndef lint
#if 0
static char sccsid[] = "@(#)su.c        8.3 (Berkeley) 4/2/94";*/
#else
__RCSID("$NetBSD: su.c,v 1.75 2023/03/24 16:58:24 kre Exp $");
#endif
#endif /* not lint */

#include <sys/param.h>
#include <sys/time.h>
#include <sys/resource.h>
#include <err.h>
#include <errno.h>
#include <grp.h>
#include <paths.h>
#include <pwd.h>
#include <stdio.h>
#ifdef SKEY
#include <skey.h>
#endif
#include <stdlib.h>
#include <string.h>
#include <syslog.h>
#include <time.h>
#include <tzfile.h>
#include <unistd.h>
#include <util.h>

#ifdef LOGIN_CAP
#include <login_cap.h>
#endif

#ifdef KERBEROS5
#include <krb5.h>
#endif

#ifdef ALLOW_GROUP_CHANGE
#include "grutil.h"
#endif
#include "suutil.h"

#ifdef KERBEROS5
#define ARGSTRX "-Kdflm"
static int kerberos5(char *, const char *, uid_t);
int use_kerberos = 1;
#else
#define ARGSTRX "-dflm"
#endif

#ifndef SU_GROUP
#define SU_GROUP        "wheel"
#endif

#define GROUP_PASSWORD  "Group Password:"

#ifdef LOGIN_CAP
#define ARGSTR  ARGSTRX "c:"
#else
#define ARGSTR ARGSTRX
#endif

static int check_ingroup(int, const char *, const char *, int);

int
main(int argc, char **argv)
{
        extern char **environ;
        struct passwd *pwd;
        char *p;
#ifdef BSD4_4
        struct timeval tp;
#endif
        uid_t ruid;
        int asme, ch, asthem, fastlogin, prio, gohome;
        enum { UNSET, YES, NO } iscsh = UNSET;
        const char *user, *shell, *avshell;
        char *username, **np;
#ifdef SU_ROOTAUTH
        char *userpass;
#endif
        char *class;
        char shellbuf[MAXPATHLEN], avshellbuf[MAXPATHLEN];
        time_t pw_warntime = _PASSWORD_WARNDAYS * SECSPERDAY;
#ifdef LOGIN_CAP
        login_cap_t *lc;
#endif
#ifdef ALLOW_GROUP_CHANGE
        char *gname;
#endif

        (void)setprogname(argv[0]);
        asme = asthem = fastlogin = 0;
        gohome = 1;
        shell = class = NULL;
        while ((ch = getopt(argc, argv, ARGSTR)) != -1)
                switch((char)ch) {
#ifdef KERBEROS5
                case 'K':
                        use_kerberos = 0;
                        break;
#endif
#ifdef LOGIN_CAP
                case 'c':
                        class = optarg;
                        break;
#endif
                case 'd':
                        asme = 0;
                        asthem = 1;
                        gohome = 0;
                        break;
                case 'f':
                        fastlogin = 1;
                        break;
                case '-':
                case 'l':
                        asme = 0;
                        asthem = 1;
                        break;
                case 'm':
                        asme = 1;
                        asthem = 0;
                        break;
                case '?':
                default:
                        (void)fprintf(stderr,
#ifdef ALLOW_GROUP_CHANGE
                            "usage: %s [%s] [login[:group] [shell arguments]]\n",
#else
                            "usage: %s [%s] [login [shell arguments]]\n",
#endif
                            getprogname(), ARGSTR);
                        exit(EXIT_FAILURE);
                }
        argv += optind;

        /* Lower the priority so su runs faster */
        errno = 0;
        prio = getpriority(PRIO_PROCESS, 0);
        if (errno)
                prio = 0;
        if (prio > -2)
                (void)setpriority(PRIO_PROCESS, 0, -2);
        openlog("su", 0, LOG_AUTH);

        /* get current login name and shell */
        ruid = getuid();
        username = getlogin();
        if (username == NULL || (pwd = getpwnam(username)) == NULL ||
            pwd->pw_uid != ruid)
                pwd = getpwuid(ruid);
        if (pwd == NULL)
                errx(EXIT_FAILURE, "who are you?");
        username = estrdup(pwd->pw_name);
#ifdef SU_ROOTAUTH
        userpass = estrdup(pwd->pw_passwd);
#endif

        if (asme) {
                if (pwd->pw_shell && *pwd->pw_shell) {
                        (void)estrlcpy(shellbuf, pwd->pw_shell, sizeof(shellbuf));
                        shell = shellbuf;
                } else {
                        shell = _PATH_BSHELL;
                        iscsh = NO;
                }
        }
        /* get target login information, default to root */
        user = *argv ? *argv : "root";
        np = *argv ? argv : argv - 1;

#ifdef ALLOW_GROUP_CHANGE
        if ((p = strchr(user, ':')) != NULL) {
                *p = '\0';
                gname = ++p;
                if (*gname == '\0')
                        errx(EXIT_FAILURE, "missing 'group' after ':'");
        } else
                gname = NULL;

#ifdef ALLOW_EMPTY_USER
        if (user[0] == '\0' && gname != NULL)
                user = username;
#endif
#endif
        if ((pwd = getpwnam(user)) == NULL)
                errx(EXIT_FAILURE, "unknown login `%s'", user);

#ifdef LOGIN_CAP
        /* force the usage of specified class */
        if (class) {
                if (ruid)
                        errx(EXIT_FAILURE, "Only root may use -c");

                pwd->pw_class = class;
        }
        if ((lc = login_getclass(pwd->pw_class)) == NULL)
                errx(EXIT_FAILURE, "Unknown class %s", pwd->pw_class);

        pw_warntime = (time_t)login_getcaptime(lc, "password-warn",
            _PASSWORD_WARNDAYS * SECSPERDAY,
            _PASSWORD_WARNDAYS * SECSPERDAY);
#endif

        if (ruid
#ifdef KERBEROS5
            && (!use_kerberos || kerberos5(username, user, pwd->pw_uid))
#endif
            ) {
                char *pass = pwd->pw_passwd;
                int ok = pwd->pw_uid != 0;

#ifdef SU_ROOTAUTH
                /*
                 * Allow those in group rootauth to su to root, by supplying
                 * their own password.
                 */
                if (!ok) {
                        if ((ok = check_ingroup(-1, SU_ROOTAUTH, username, 0))) {
                                pass = userpass;
                                user = username;
                        }
                }
#endif
                /*
                 * Only allow those in group SU_GROUP to su to root,
                 * but only if that group has any members.
                 * If SU_GROUP has no members, allow anyone to su root
                 */
                if (!ok)
                        ok = check_ingroup(-1, SU_GROUP, username, 1);
                if (!ok)
                        errx(EXIT_FAILURE,
            "you are not listed in the correct secondary group (%s) to su %s.",
                                            SU_GROUP, user);
                /* if target requires a password, verify it */
                if (*pass && pwd->pw_uid != ruid) {     /* XXX - OK? */
                        p = getpass("Password:");
#ifdef SKEY
                        if (strcasecmp(p, "s/key") == 0) {
                                if (skey_haskey(user))
                                        errx(EXIT_FAILURE,
                                            "Sorry, you have no s/key.");
                                else {
                                        if (skey_authenticate(user)) {
                                                goto badlogin;
                                        }
                                }

                        } else
#endif
                        if (consttime_memequal(pass,
                            crypt(p, pass), strlen(pass)) == 0) {
#ifdef SKEY
 badlogin:
#endif
                                (void)fprintf(stderr, "Sorry\n");
                                syslog(LOG_WARNING,
                                        "BAD SU %s to %s%s", username,
                                        pwd->pw_name, ontty());
                                exit(EXIT_FAILURE);
                        }
                }
        }

        if (asme) {
                /* if asme and non-standard target shell, must be root */
                if (chshell(pwd->pw_shell) == 0 && ruid)
                        errx(EXIT_FAILURE, "permission denied (shell).");
        } else if (pwd->pw_shell && *pwd->pw_shell) {
                shell = pwd->pw_shell;
                iscsh = UNSET;
        } else {
                shell = _PATH_BSHELL;
                iscsh = NO;
        }

        if ((p = strrchr(shell, '/')) != NULL)
                avshell = p+1;
        else
                avshell = shell;

        /* if we're forking a csh, we want to slightly muck the args */
        if (iscsh == UNSET)
                iscsh = strstr(avshell, "csh") ? YES : NO;

        /* set permissions */
#ifdef LOGIN_CAP
# ifdef ALLOW_GROUP_CHANGE
        /* if we aren't changing users, keep the current group members */
        if (ruid != pwd->pw_uid &&
            setusercontext(lc, pwd, pwd->pw_uid, LOGIN_SETGROUP) == -1)
                err(EXIT_FAILURE, "setting user context");

        addgroup(lc, gname, pwd, ruid, GROUP_PASSWORD);

        if (setusercontext(lc, pwd, pwd->pw_uid,
                (u_int)(asthem ? (LOGIN_SETPRIORITY | LOGIN_SETUMASK) : 0) |
                LOGIN_SETRESOURCES | LOGIN_SETUSER) == -1)
                err(EXIT_FAILURE, "setting user context");
# else
        if (setusercontext(lc, pwd, pwd->pw_uid,
                (u_int)(asthem ? (LOGIN_SETPRIORITY | LOGIN_SETUMASK) : 0) |
                LOGIN_SETRESOURCES | LOGIN_SETGROUP | LOGIN_SETUSER) == -1)
                err(EXIT_FAILURE, "setting user context");
# endif
#else
        if (setgid(pwd->pw_gid) == -1)
                err(EXIT_FAILURE, "setgid");
        /* if we aren't changing users, keep the current group members */
        if (ruid != pwd->pw_uid && initgroups(user, pwd->pw_gid) != 0)
                errx(EXIT_FAILURE, "initgroups failed");
# ifdef ALLOW_GROUP_CHANGE
        addgroup(/*EMPTY*/, gname, pwd, ruid, GROUP_PASSWORD);
# endif
        if (setuid(pwd->pw_uid) == -1)
                err(EXIT_FAILURE, "setuid");
#endif

        if (!asme) {
                if (asthem) {
                        p = getenv("TERM");
                        /* Create an empty environment */
                        environ = emalloc(sizeof(char *));
                        environ[0] = NULL;
#ifdef LOGIN_CAP
                        if (setusercontext(lc, pwd, pwd->pw_uid,
                                LOGIN_SETPATH) == -1)
                                err(EXIT_FAILURE, "setting user context");
#else
                        (void)setenv("PATH", _PATH_DEFPATH, 1);
#endif
                        if (p)
                                (void)setenv("TERM", p, 1);
                        if (gohome && chdir(pwd->pw_dir) == -1)
                                errx(EXIT_FAILURE, "no directory");
                }

                if (asthem || pwd->pw_uid) {
                        (void)setenv("LOGNAME", pwd->pw_name, 1);
                        (void)setenv("USER", pwd->pw_name, 1);
                }
                (void)setenv("HOME", pwd->pw_dir, 1);
                (void)setenv("SHELL", shell, 1);
        }
        (void)setenv("SU_FROM", username, 1);

        if (iscsh == YES) {
                if (fastlogin)
                        *np-- = __UNCONST("-f");
                if (asme)
                        *np-- = __UNCONST("-m");
        } else {
                if (fastlogin)
                        (void)unsetenv("ENV");
        }

        if (asthem) {
                avshellbuf[0] = '-';
                (void)estrlcpy(avshellbuf + 1, avshell, sizeof(avshellbuf) - 1);
                avshell = avshellbuf;
        } else if (iscsh == YES) {
                /* csh strips the first character... */
                avshellbuf[0] = '_';
                (void)estrlcpy(avshellbuf + 1, avshell, sizeof(avshellbuf) - 1);
                avshell = avshellbuf;
        }
        *np = __UNCONST(avshell);

#ifdef BSD4_4
        if (pwd->pw_change || pwd->pw_expire)
                (void)gettimeofday(&tp, NULL);
        if (pwd->pw_change) {
                if (tp.tv_sec >= pwd->pw_change) {
                        (void)printf("%s -- %s's password has expired.\n",
                                     (ruid ? "Sorry" : "Note"), user);
                        if (ruid != 0)
                                exit(EXIT_FAILURE);
                } else if (pwd->pw_change - tp.tv_sec < pw_warntime)
                        (void)printf("Warning: %s's password expires on %s",
                                     user, ctime(&pwd->pw_change));
        }
        if (pwd->pw_expire) {
                if (tp.tv_sec >= pwd->pw_expire) {
                        (void)printf("%s -- %s's account has expired.\n",
                                     (ruid ? "Sorry" : "Note"), user);
                        if (ruid != 0)
                                exit(EXIT_FAILURE);
                } else if (pwd->pw_expire - tp.tv_sec <
                    _PASSWORD_WARNDAYS * SECSPERDAY)
                        (void)printf("Warning: %s's account expires on %s",
                                     user, ctime(&pwd->pw_expire));
        }
#endif
        if (ruid != 0)
                syslog(LOG_NOTICE, "%s to %s%s",
                    username, pwd->pw_name, ontty());

        /* Raise our priority back to what we had before */
        (void)setpriority(PRIO_PROCESS, 0, prio);

        (void)execv(shell, np);
        err(EXIT_FAILURE, "%s", shell);
        /* NOTREACHED */
}


#ifdef KERBEROS5
static int
kerberos5(char *username, const char *user, uid_t uid)
{
        krb5_error_code ret;
        krb5_context context;
        krb5_principal princ = NULL;
        krb5_ccache ccache, ccache2;
        char *cc_name;
        const char *filename;

        ret = krb5_init_context(&context);
        if (ret)
                return 1;

        if (strcmp(user, "root") == 0)
                ret = krb5_make_principal(context, &princ,
                                          NULL, username, "root", NULL);
        else
                ret = krb5_make_principal(context, &princ,
                                          NULL, user, NULL);
        if (ret)
                goto fail;
        if (!krb5_kuserok(context, princ, user) && !uid) {
                warnx("kerberos5: not in %s's ACL.", user);
                goto fail;
        }
        ret = krb5_cc_new_unique(context, krb5_mcc_ops.prefix, NULL, &ccache);
        if (ret)
                goto fail;
        ret = krb5_verify_user_lrealm(context, princ, ccache, NULL, TRUE,
                                      NULL);
        if (ret) {
                krb5_cc_destroy(context, ccache);
                switch (ret) {
                case KRB5_LIBOS_PWDINTR :
                        break;
                case KRB5KRB_AP_ERR_BAD_INTEGRITY:
                case KRB5KRB_AP_ERR_MODIFIED:
                        krb5_warnx(context, "Password incorrect");
                        break;
                default :
                        krb5_warn(context, ret, "krb5_verify_user");
                        break;
                }
                goto fail;
        }
        ret = krb5_cc_new_unique(context, krb5_mcc_ops.prefix, NULL, &ccache2);
        if (ret) {
                krb5_cc_destroy(context, ccache);
                goto fail;
        }
        ret = krb5_cc_copy_cache(context, ccache, ccache2);
        if (ret) {
                krb5_cc_destroy(context, ccache);
                krb5_cc_destroy(context, ccache2);
                goto fail;
        }

        filename = krb5_cc_get_name(context, ccache2);
        (void)easprintf(&cc_name, "%s:%s", krb5_cc_get_type(context, ccache2),
                 filename);
        if (chown(filename, uid, NOGROUP) == -1) {
                warn("chown %s", filename);
                free(cc_name);
                krb5_cc_destroy(context, ccache);
                krb5_cc_destroy(context, ccache2);
                goto fail;
        }

        (void)setenv("KRB5CCNAME", cc_name, 1);
        free(cc_name);
        krb5_cc_close(context, ccache2);
        krb5_cc_destroy(context, ccache);
        return 0;

 fail:
        if (princ != NULL)
                krb5_free_principal(context, princ);
        krb5_free_context(context);
        return 1;
}
#endif /* KERBEROS5 */

static int
check_ingroup(int gid, const char *gname, const char *user, int ifempty)
{
        struct group *gr;
        char **g;
#ifdef SU_INDIRECT_GROUP
        char **gr_mem;
        int n = 0;
        int i = 0;
#endif
        int ok = 0;

        if (gname == NULL)
                gr = getgrgid((gid_t) gid);
        else
                gr = getgrnam(gname);

        /*
         * XXX we are relying on the fact that we only set ifempty when
         * calling to check for SU_GROUP and that is the only time a
         * missing group is acceptable.
         */
        if (gr == NULL)
                return ifempty;
        if (!*gr->gr_mem)               /* empty */
                return ifempty;

        /*
         * Ok, first see if user is in gr_mem
         */
        for (g = gr->gr_mem; *g; ++g) {
                if (strcmp(*g, user) == 0)
                        return 1;       /* ok */
#ifdef SU_INDIRECT_GROUP
                ++n;                    /* count them */
#endif
        }
#ifdef SU_INDIRECT_GROUP
        /*
         * No.
         * Now we need to duplicate the gr_mem list, and recurse for
         * each member to see if it is a group, and if so whether user is
         * in it.
         */
        gr_mem = NULL;
        ereallocarr(&gr_mem, n + 1, sizeof(char *));
        for (g = gr->gr_mem, i = 0; *g; ++g) {
                gr_mem[i] = estrdup(*g);
                i++;
        }
        gr_mem[i++] = NULL;

        for (g = gr_mem; ok == 0 && *g; ++g) {
                /*
                 * If we get this far we don't accept empty/missing groups.
                 */
                ok = check_ingroup(-1, *g, user, 0);
        }
        for (g = gr_mem; *g; ++g) {
                free(*g);
        }
        free(gr_mem);
#endif
        return ok;
}