usr/src/usr.bin/su/su.c

/*
 * Copyright (c) 1988, 1993, 1994
 *      The Regents of the University of California.  All rights reserved.
 *
 * %sccs.include.redist.c%
 */

#ifndef lint
static char copyright[] =
"@(#) Copyright (c) 1988, 1993, 1994\n\
        The Regents of the University of California.  All rights reserved.\n";
#endif /* not lint */

#ifndef lint
static char sccsid[] = "@(#)su.c        8.3 (Berkeley) %G%";
#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>
#include <stdlib.h>
#include <string.h>
#include <syslog.h>
#include <unistd.h>

#ifdef KERBEROS
#include <kerberosIV/des.h>
#include <kerberosIV/krb.h>
#include <netdb.h>

#define ARGSTR  "-Kflm"

int use_kerberos = 1;
#else
#define ARGSTR  "-flm"
#endif

char   *ontty __P((void));
int     chshell __P((char *));

int
main(argc, argv)
        int argc;
        char **argv;
{
        extern char **environ;
        struct passwd *pwd;
        char *p, **g, *user, *shell, *username, *cleanenv[2], *nargv[4], **np;
        struct group *gr;
        uid_t ruid;
        int asme, ch, asthem, fastlogin, prio;
        enum { UNSET, YES, NO } iscsh = UNSET;
        char shellbuf[MAXPATHLEN];

        np = &nargv[3];
        *np-- = NULL;
        asme = asthem = fastlogin = 0;
        while ((ch = getopt(argc, argv, ARGSTR)) != EOF)
                switch((char)ch) {
#ifdef KERBEROS
                case 'K':
                        use_kerberos = 0;
                        break;
#endif
                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, "usage: su [%s] [login]\n",
                            ARGSTR);
                        exit(1);
                }
        argv += optind;

        errno = 0;
        prio = getpriority(PRIO_PROCESS, 0);
        if (errno)
                prio = 0;
        (void)setpriority(PRIO_PROCESS, 0, -2);
        openlog("su", LOG_CONS, 0);

        /* 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(1, "who are you?");
        username = strdup(pwd->pw_name);
        if (username == NULL)
                err(1, NULL);
        if (asme)
                if (pwd->pw_shell && *pwd->pw_shell)
                        shell = strcpy(shellbuf,  pwd->pw_shell);
                else {
                        shell = _PATH_BSHELL;
                        iscsh = NO;
                }

        /* get target login information, default to root */
        user = *argv ? *argv : "root";
        if ((pwd = getpwnam(user)) == NULL) {
                fprintf(stderr, "su: unknown login %s\n", user);
                exit(1);
        }

        if (ruid) {
#ifdef KERBEROS
            if (!use_kerberos || kerberos(username, user, pwd->pw_uid))
#endif
            {
                /* only allow those in group zero to su to root. */
                if (pwd->pw_uid == 0 && (gr = getgrgid((gid_t)0)))
                        for (g = gr->gr_mem;; ++g) {
                                if (!*g)
                                        errx(1,
                            "you are not in the correct group to su %s.",
                                            user);
                                if (strcmp(username, *g) == 0)
                                        break;
                }
                /* if target requires a password, verify it */
                if (*pwd->pw_passwd) {
                        p = getpass("Password:");
                        if (strcmp(pwd->pw_passwd, crypt(p, pwd->pw_passwd))) {
                                fprintf(stderr, "Sorry\n");
                                syslog(LOG_AUTH|LOG_WARNING,
                                        "BAD SU %s to %s%s", username,
                                        user, ontty());
                                exit(1);
                        }
                }
            }
        }

        if (asme) {
                /* if asme and non-standard target shell, must be root */
                if (!chshell(pwd->pw_shell) && ruid)
                        errx(1, "permission denied (shell).");
        } else if (pwd->pw_shell && *pwd->pw_shell) {
                shell = pwd->pw_shell;
                iscsh = UNSET;
        } else {
                shell = _PATH_BSHELL;
                iscsh = NO;
        }

        /* if we're forking a csh, we want to slightly muck the args */
        if (iscsh == UNSET) {
                if (p = strrchr(shell, '/'))
                        ++p;
                else
                        p = shell;
                iscsh = strcmp(p, "csh") ? NO : YES;
        }

        /* set permissions */
        if (setgid(pwd->pw_gid) < 0)
                err(1, "setgid");
        if (initgroups(user, pwd->pw_gid))
                errx(1, "initgroups failed");
        if (setuid(pwd->pw_uid) < 0)
                err(1, "setuid");

        if (!asme) {
                if (asthem) {
                        p = getenv("TERM");
                        cleanenv[0] = _PATH_DEFPATH;
                        cleanenv[1] = NULL;
                        environ = cleanenv;
                        (void)setenv("TERM", p, 1);
                        if (chdir(pwd->pw_dir) < 0)
                                errx(1, "no directory");
                }
                if (asthem || pwd->pw_uid)
                        (void)setenv("USER", pwd->pw_name, 1);
                (void)setenv("HOME", pwd->pw_dir, 1);
                (void)setenv("SHELL", shell, 1);
        }

        if (iscsh == YES) {
                if (fastlogin)
                        *np-- = "-f";
                if (asme)
                        *np-- = "-m";
        }

        /* csh strips the first character... */
        *np = asthem ? "-su" : iscsh == YES ? "_su" : "su";

        if (ruid != 0)
                syslog(LOG_NOTICE|LOG_AUTH, "%s to %s%s",
                    username, user, ontty());

        (void)setpriority(PRIO_PROCESS, 0, prio);

        execv(shell, np);
        err(1, "%s", shell);
}

int
chshell(sh)
        char *sh;
{
        char *cp;

        while ((cp = getusershell()) != NULL)
                if (strcmp(cp, sh) == 0)
                        return (1);
        return (0);
}

char *
ontty()
{
        char *p;
        static char buf[MAXPATHLEN + 4];

        buf[0] = 0;
        if (p = ttyname(STDERR_FILENO))
                snprintf(buf, sizeof(buf), " on %s", p);
        return (buf);
}

#ifdef KERBEROS
kerberos(username, user, uid)
        char *username, *user;
        int uid;
{
        extern char *krb_err_txt[];
        KTEXT_ST ticket;
        AUTH_DAT authdata;
        struct hostent *hp;
        char *p;
        int kerno;
        u_long faddr;
        char lrealm[REALM_SZ], krbtkfile[MAXPATHLEN];
        char hostname[MAXHOSTNAMELEN], savehost[MAXHOSTNAMELEN];
        char *krb_get_phost();

        if (krb_get_lrealm(lrealm, 1) != KSUCCESS)
                return (1);
        if (koktologin(username, lrealm, user) && !uid) {
                warnx("kerberos: not in %s's ACL.", user);
                return (1);
        }
        (void)sprintf(krbtkfile, "%s_%s_%d", TKT_ROOT, user, getuid());

        (void)setenv("KRBTKFILE", krbtkfile, 1);
        (void)krb_set_tkt_string(krbtkfile);
        /*
         * Set real as well as effective ID to 0 for the moment,
         * to make the kerberos library do the right thing.
         */
        if (setuid(0) < 0) {
                warn("setuid");
                return (1);
        }

        /*
         * Little trick here -- if we are su'ing to root,
         * we need to get a ticket for "xxx.root", where xxx represents
         * the name of the person su'ing.  Otherwise (non-root case),
         * we need to get a ticket for "yyy.", where yyy represents
         * the name of the person being su'd to, and the instance is null
         *
         * We should have a way to set the ticket lifetime,
         * with a system default for root.
         */
        kerno = krb_get_pw_in_tkt((uid == 0 ? username : user),
                (uid == 0 ? "root" : ""), lrealm,
                "krbtgt", lrealm, DEFAULT_TKT_LIFE, 0);

        if (kerno != KSUCCESS) {
                if (kerno == KDC_PR_UNKNOWN) {
                        warnx("kerberos: principal unknown: %s.%s@%s",
                                (uid == 0 ? username : user),
                                (uid == 0 ? "root" : ""), lrealm);
                        return (1);
                }
                warnx("kerberos: unable to su: %s", krb_err_txt[kerno]);
                syslog(LOG_NOTICE|LOG_AUTH,
                    "BAD Kerberos SU: %s to %s%s: %s",
                    username, user, ontty(), krb_err_txt[kerno]);
                return (1);
        }

        if (chown(krbtkfile, uid, -1) < 0) {
                warn("chown");
                (void)unlink(krbtkfile);
                return (1);
        }

        (void)setpriority(PRIO_PROCESS, 0, -2);

        if (gethostname(hostname, sizeof(hostname)) == -1) {
                warn("gethostname");
                dest_tkt();
                return (1);
        }

        (void)strncpy(savehost, krb_get_phost(hostname), sizeof(savehost));
        savehost[sizeof(savehost) - 1] = '\0';

        kerno = krb_mk_req(&ticket, "rcmd", savehost, lrealm, 33);

        if (kerno == KDC_PR_UNKNOWN) {
                warnx("Warning: TGT not verified.");
                syslog(LOG_NOTICE|LOG_AUTH,
                    "%s to %s%s, TGT not verified (%s); %s.%s not registered?",
                    username, user, ontty(), krb_err_txt[kerno],
                    "rcmd", savehost);
        } else if (kerno != KSUCCESS) {
                warnx("Unable to use TGT: %s", krb_err_txt[kerno]);
                syslog(LOG_NOTICE|LOG_AUTH, "failed su: %s to %s%s: %s",
                    username, user, ontty(), krb_err_txt[kerno]);
                dest_tkt();
                return (1);
        } else {
                if (!(hp = gethostbyname(hostname))) {
                        warnx("can't get addr of %s", hostname);
                        dest_tkt();
                        return (1);
                }
                memmove((char *)&faddr, (char *)hp->h_addr, sizeof(faddr));

                if ((kerno = krb_rd_req(&ticket, "rcmd", savehost, faddr,
                    &authdata, "")) != KSUCCESS) {
                        warnx("kerberos: unable to verify rcmd ticket: %s\n",
                            krb_err_txt[kerno]);
                        syslog(LOG_NOTICE|LOG_AUTH,
                            "failed su: %s to %s%s: %s", username,
                             user, ontty(), krb_err_txt[kerno]);
                        dest_tkt();
                        return (1);
                }
        }
        return (0);
}

koktologin(name, realm, toname)
        char *name, *realm, *toname;
{
        AUTH_DAT *kdata;
        AUTH_DAT kdata_st;

        kdata = &kdata_st;
        memset((char *)kdata, 0, sizeof(*kdata));
        (void)strcpy(kdata->pname, name);
        (void)strcpy(kdata->pinst,
            ((strcmp(toname, "root") == 0) ? "root" : ""));
        (void)strcpy(kdata->prealm, realm);
        return (kuserok(kdata, toname));
}
#endif