/*-
 * Copyright (c) 1996 by
 * Sean Eric Fagan <sef@kithrup.com>
 * David Nugent <davidn@blaze.net.au>
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, is permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice immediately at the beginning of the file, without modification,
 *    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. This work was done expressly for inclusion into FreeBSD.  Other use
 *    is permitted provided this notation is included.
 * 4. Absolutely no warranty of function or purpose is made by the authors.
 * 5. Modifications may be freely made to this file providing the above
 *    conditions are met.
 *
 * High-level routines relating to use of the user capabilities database
 *
 * $FreeBSD: head/lib/libutil/login_class.c 256850 2013-10-21 16:46:12Z kib $
 */

#include <sys/types.h>
#include <sys/resource.h>
#include <sys/rtprio.h>
#include <sys/stat.h>
#include <sys/time.h>

#include <ctype.h>
#include <err.h>
#include <errno.h>
#include <fcntl.h>
#include <login_cap.h>
#include <paths.h>
#include <pwd.h>
#include <signal.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <syslog.h>
#include <unistd.h>


static struct login_res {
    const char *what;
    rlim_t (*who)(login_cap_t *, const char *, rlim_t, rlim_t);
    int why;
} resources[] = {
    { "cputime",        login_getcaptime,       RLIMIT_CPU      },
    { "filesize",       login_getcapsize,       RLIMIT_FSIZE    },
    { "datasize",       login_getcapsize,       RLIMIT_DATA     },
    { "stacksize",      login_getcapsize,       RLIMIT_STACK    },
    { "memoryuse",      login_getcapsize,       RLIMIT_RSS      },
    { "memorylocked",   login_getcapsize,       RLIMIT_MEMLOCK  },
    { "maxproc",        login_getcapnum,        RLIMIT_NPROC    },
    { "openfiles",      login_getcapnum,        RLIMIT_NOFILE   },
    { "coredumpsize",   login_getcapsize,       RLIMIT_CORE     },
    { "sbsize",         login_getcapsize,       RLIMIT_SBSIZE   },
    { "vmemoryuse",     login_getcapsize,       RLIMIT_VMEM     },
#ifdef RLIMIT_POSIXLOCKS
    { "posixlocks",     login_getcapnum,        RLIMIT_POSIXLOCKS },
#endif
    { NULL,             0,                      0               }
};


void
setclassresources(login_cap_t *lc)
{
    struct login_res *lr;

    if (lc == NULL)
        return;

    for (lr = resources; lr->what != NULL; ++lr) {
        struct rlimit   rlim;

        /*
         * The login.conf file can have <limit>, <limit>-max, and
         * <limit>-cur entries.
         * What we do is get the current current- and maximum- limits.
         * Then, we try to get an entry for <limit> from the capability,
         * using the current and max limits we just got as the
         * default/error values.
         * *Then*, we try looking for <limit>-cur and <limit>-max,
         * again using the appropriate values as the default/error
         * conditions.
         */

        if (getrlimit(lr->why, &rlim) != 0)
            syslog(LOG_ERR, "getting %s resource limit: %m", lr->what);
        else {
            char        name_cur[40];
            char        name_max[40];
            rlim_t      rcur = rlim.rlim_cur;
            rlim_t      rmax = rlim.rlim_max;

            sprintf(name_cur, "%s-cur", lr->what);
            sprintf(name_max, "%s-max", lr->what);

            rcur = (*lr->who)(lc, lr->what, rcur, rcur);
            rmax = (*lr->who)(lc, lr->what, rmax, rmax);
            rlim.rlim_cur = (*lr->who)(lc, name_cur, rcur, rcur);
            rlim.rlim_max = (*lr->who)(lc, name_max, rmax, rmax);

            if (setrlimit(lr->why, &rlim) == -1)
                syslog(LOG_WARNING, "set class '%s' resource limit %s: %m", lc->lc_class, lr->what);
        }
    }
}



static struct login_vars {
    const char *tag;
    const char *var;
    const char *def;
    int overwrite;
} pathvars[] = {
    { "path",           "PATH",       NULL, 1},
    { "cdpath",         "CDPATH",     NULL, 1},
    { "manpath",        "MANPATH",    NULL, 1},
    { NULL,             NULL,         NULL, 0}
}, envars[] = {
    { "lang",           "LANG",       NULL, 1},
    { "charset",        "MM_CHARSET", NULL, 1},
    { "timezone",       "TZ",         NULL, 1},
    { "term",           "TERM",       NULL, 0},
    { NULL,             NULL,         NULL, 0}
};

static char *
substvar(const char * var, const struct passwd * pwd, int hlen, int pch, int nlen)
{
    char    *np = NULL;

    if (var != NULL) {
        int     tildes = 0;
        int     dollas = 0;
        char    *p;
        const char *q;

        if (pwd != NULL) {
            for (q = var; *q != '\0'; ++q) {
                tildes += (*q == '~');
                dollas += (*q == '$');
            }
        }

        np = malloc(strlen(var) + (dollas * nlen)
                    - dollas + (tildes * (pch+hlen))
                    - tildes + 1);

        if (np != NULL) {
            p = strcpy(np, var);

            if (pwd != NULL) {
                /*
                 * This loop does user username and homedir substitutions
                 * for unescaped $ (username) and ~ (homedir)
                 */
                while (*(p += strcspn(p, "~$")) != '\0') {
                    int l = strlen(p);

                    if (p > np && *(p-1) == '\\')  /* Escaped: */
                        memmove(p - 1, p, l + 1); /* Slide-out the backslash */
                    else if (*p == '~') {
                        int     v = pch && *(p+1) != '/'; /* Avoid double // */
                        memmove(p + hlen + v, p + 1, l);  /* Subst homedir */
                        memmove(p, pwd->pw_dir, hlen);
                        if (v)
                            p[hlen] = '/';
                        p += hlen + v;
                    }
                    else /* if (*p == '$') */ {
                        memmove(p + nlen, p + 1, l);    /* Subst username */
                        memmove(p, pwd->pw_name, nlen);
                        p += nlen;
                    }
                }
            }
        }
    }

    return (np);
}


void
setclassenvironment(login_cap_t *lc, const struct passwd * pwd, int paths)
{
    struct login_vars   *vars = paths ? pathvars : envars;
    int                 hlen = pwd ? strlen(pwd->pw_dir) : 0;
    int                 nlen = pwd ? strlen(pwd->pw_name) : 0;
    char pch = 0;

    if (hlen && pwd->pw_dir[hlen-1] != '/')
        ++pch;

    while (vars->tag != NULL) {
        const char * var = paths ? login_getpath(lc, vars->tag, NULL)
                           : login_getcapstr(lc, vars->tag, NULL, NULL);

        char * np  = substvar(var, pwd, hlen, pch, nlen);

        if (np != NULL) {
            setenv(vars->var, np, vars->overwrite);
            free(np);
        } else if (vars->def != NULL) {
            setenv(vars->var, vars->def, 0);
        }
        ++vars;
    }

    /*
     * If we're not processing paths, then see if there is a setenv list by
     * which the admin and/or user may set an arbitrary set of env vars.
     */
    if (!paths) {
        const char      **set_env = login_getcaplist(lc, "setenv", ",");

        if (set_env != NULL) {
            while (*set_env != NULL) {
                char    *p = strchr(*set_env, '=');

                if (p != NULL) {  /* Discard invalid entries */
                    char        *np;

                    *p++ = '\0';
                    if ((np = substvar(p, pwd, hlen, pch, nlen)) != NULL) {
                        setenv(*set_env, np, 1);
                        free(np);
                    }
                }
                ++set_env;
            }
        }
    }
}



/*
 * setclasscontext()
 *
 * For the login class <class>, set various class context values
 * (limits, mainly) to the values for that class.  Which values are
 * set are controlled by <flags> -- see <login_class.h> for the
 * possible values.
 *
 * setclasscontext() can only set resources, priority, and umask.
 */

int
setclasscontext(const char *classname, unsigned int flags)
{
    int         rc;
    login_cap_t *lc;

    lc = login_getclassbyname(classname, NULL);

    flags &= LOGIN_SETRESOURCES | LOGIN_SETPRIORITY |
            LOGIN_SETUMASK | LOGIN_SETPATH;

    rc = lc ? setusercontext(lc, NULL, 0, flags) : -1;
    login_close(lc);
    return (rc);
}



/*
 * Private function which takes care of processing
 */

static mode_t
setlogincontext(login_cap_t *lc, const struct passwd *pwd,
                mode_t mymask, unsigned long flags)
{
    if (lc) {
        /* Set resources */
        if (flags & LOGIN_SETRESOURCES)
            setclassresources(lc);
        /* See if there's a umask override */
        if (flags & LOGIN_SETUMASK)
            mymask = (mode_t)login_getcapnum(lc, "umask", mymask, mymask);
        /* Set paths */
        if (flags & LOGIN_SETPATH)
            setclassenvironment(lc, pwd, 1);
        /* Set environment */
        if (flags & LOGIN_SETENV)
            setclassenvironment(lc, pwd, 0);
    }
    return (mymask);
}



/*
 * setusercontext()
 *
 * Given a login class <lc> and a user in <pwd>, with a uid <uid>,
 * set the context as in setclasscontext().  <flags> controls which
 * values are set.
 *
 * The difference between setclasscontext() and setusercontext() is
 * that the former sets things up for an already-existing process,
 * while the latter sets things up from a root context.  Such as might
 * be called from login(1).
 *
 */

int
setusercontext(login_cap_t *lc, const struct passwd *pwd, uid_t uid, unsigned int flags)
{
    rlim_t      p;
    mode_t      mymask;
    login_cap_t *llc = NULL;
    struct rtprio rtp;

    if (lc == NULL) {
        if (pwd != NULL && (lc = login_getpwclass(pwd)) != NULL)
            llc = lc; /* free this when we're done */
    }

    if (flags & LOGIN_SETPATH)
        pathvars[0].def = uid ? _PATH_DEFPATH : _PATH_STDPATH;

    /* we need a passwd entry to set these */
    if (pwd == NULL)
        flags &= ~(LOGIN_SETGROUP | LOGIN_SETLOGIN);

    /* Set the process priority */
    if (flags & LOGIN_SETPRIORITY) {
        p = login_getcapnum(lc, "priority", LOGIN_DEFPRI, LOGIN_DEFPRI);

        if (p > PRIO_MAX) {
            rtp.type = RTP_PRIO_IDLE;
            p -= PRIO_MAX + 1;
            rtp.prio = p > RTP_PRIO_MAX ? RTP_PRIO_MAX : p;
            if (rtprio(RTP_SET, 0, &rtp))
                syslog(LOG_WARNING, "rtprio '%s' (%s): %m",
                    pwd ? pwd->pw_name : "-",
                    lc ? lc->lc_class : LOGIN_DEFCLASS);
        } else if (p < PRIO_MIN) {
            rtp.type = RTP_PRIO_REALTIME;
            p -= PRIO_MIN - RTP_PRIO_MAX;
            rtp.prio = p < RTP_PRIO_MIN ? RTP_PRIO_MIN : p;
            if (rtprio(RTP_SET, 0, &rtp))
                syslog(LOG_WARNING, "rtprio '%s' (%s): %m",
                    pwd ? pwd->pw_name : "-",
                    lc ? lc->lc_class : LOGIN_DEFCLASS);
        } else {
            if (setpriority(PRIO_PROCESS, 0, (int)p) != 0)
                syslog(LOG_WARNING, "setpriority '%s' (%s): %m",
                    pwd ? pwd->pw_name : "-",
                    lc ? lc->lc_class : LOGIN_DEFCLASS);
        }
    }

    /* Setup the user's group permissions */
    if (flags & LOGIN_SETGROUP) {
        if (setgid(pwd->pw_gid) != 0) {
            syslog(LOG_ERR, "setgid(%lu): %m", (u_long)pwd->pw_gid);
            login_close(llc);
            return (-1);
        }
        if (initgroups(pwd->pw_name, pwd->pw_gid) == -1) {
            syslog(LOG_ERR, "initgroups(%s,%lu): %m", pwd->pw_name,
                   (u_long)pwd->pw_gid);
            login_close(llc);
            return (-1);
        }
    }

    /* Set the sessions login */
    if ((flags & LOGIN_SETLOGIN) && setlogin(pwd->pw_name) != 0) {
        syslog(LOG_ERR, "setlogin(%s): %m", pwd->pw_name);
        login_close(llc);
        return (-1);
    }

    mymask = (flags & LOGIN_SETUMASK) ? umask(LOGIN_DEFUMASK) : 0;
    mymask = setlogincontext(lc, pwd, mymask, flags);
    login_close(llc);

    /* This needs to be done after anything that needs root privs */
    if ((flags & LOGIN_SETUSER) && setuid(uid) != 0) {
        syslog(LOG_ERR, "setuid(%lu): %m", (u_long)uid);
        return (-1);    /* Paranoia again */
    }

    /*
     * Now, we repeat some of the above for the user's private entries
     */
    if (getuid() == uid && (lc = login_getuserclass(pwd)) != NULL) {
        mymask = setlogincontext(lc, pwd, mymask, flags);
        login_close(lc);
    }

    /* Finally, set any umask we've found */
    if (flags & LOGIN_SETUMASK)
        umask(mymask);

    return (0);
}