source: MondoRescue/branches/2.2.2/mindi-busybox/applets/applets.c@ 1247

/* vi: set sw=4 ts=4: */
/*
 * Utility routines.
 *
 * Copyright (C) tons of folks.  Tracking down who wrote what
 * isn't something I'm going to worry about...  If you wrote something
 * here, please feel free to acknowledge your work.
 *
 * Based in part on code from sash, Copyright (c) 1999 by David I. Bell
 * Permission has been granted to redistribute this code under the GPL.
 *
 * Licensed under GPLv2 or later, see file License in this tarball for details.
 */

#include "busybox.h"
#include <unistd.h>
#include <string.h>
#include <assert.h>

#if ENABLE_SHOW_USAGE && !ENABLE_FEATURE_COMPRESS_USAGE
static const char usage_messages[] =
#define MAKE_USAGE
#include "usage.h"
#include "applets.h"
;
#undef MAKE_USAGE
#else
#define usage_messages 0
#endif /* ENABLE_SHOW_USAGE */

#undef APPLET
#undef APPLET_NOUSAGE
#undef PROTOTYPES
#include "applets.h"

static struct BB_applet *applet_using;

/* The -1 arises because of the {0,NULL,0,-1} entry above. */
const size_t NUM_APPLETS = (sizeof (applets) / sizeof (struct BB_applet) - 1);


#ifdef CONFIG_FEATURE_SUID_CONFIG

#include <ctype.h>
#include "pwd_.h"
#include "grp_.h"

#define CONFIG_FILE "/etc/busybox.conf"

/* applets [] is const, so we have to define this "override" structure */
static struct BB_suid_config
{
  struct BB_applet *m_applet;

  uid_t m_uid;
  gid_t m_gid;
  mode_t m_mode;

  struct BB_suid_config *m_next;
} *suid_config;

static int suid_cfg_readable;

/* check if u is member of group g */
static int ingroup (uid_t u, gid_t g)
{
  struct group *grp = getgrgid (g);

  if (grp) {
    char **mem;

    for (mem = grp->gr_mem; *mem; mem++) {
      struct passwd *pwd = getpwnam (*mem);

      if (pwd && (pwd->pw_uid == u))
        return 1;
    }
  }
  return 0;
}

/* This should probably be a libbb routine.  In that case,
 * I'd probably rename it to something like bb_trimmed_slice.
 */
static char *get_trimmed_slice(char *s, char *e)
{
    /* First, consider the value at e to be nul and back up until we
     * reach a non-space char.  Set the char after that (possibly at
     * the original e) to nul. */
    while (e-- > s) {
        if (!isspace(*e)) {
            break;
        }
    }
    e[1] = 0;

    /* Next, advance past all leading space and return a ptr to the
     * first non-space char; possibly the terminating nul. */
    return skip_whitespace(s);
}


#define parse_error(x)  { err=x; goto pe_label; }

/* Don't depend on the tools to combine strings. */
static const char config_file[] = CONFIG_FILE;

/* There are 4 chars + 1 nul for each of user/group/other. */
static const char mode_chars[] = "Ssx-\0Ssx-\0Ttx-";

/* We don't supply a value for the nul, so an index adjustment is
 * necessary below.  Also, we use unsigned short here to save some
 * space even though these are really mode_t values. */
static const unsigned short mode_mask[] = {
    /*  SST         sst                 xxx   --- */
    S_ISUID,    S_ISUID|S_IXUSR,    S_IXUSR,    0,  /* user */
    S_ISGID,    S_ISGID|S_IXGRP,    S_IXGRP,    0,  /* group */
    0,          S_IXOTH,            S_IXOTH,    0   /* other */
};

static void parse_config_file(void)
{
    struct BB_suid_config *sct_head;
    struct BB_suid_config *sct;
    struct BB_applet *applet;
    FILE *f;
    char *err;
    char *s;
    char *e;
    int i, lc, section;
    char buffer[256];
    struct stat st;

    assert(!suid_config);       /* Should be set to NULL by bss init. */

    if ((stat(config_file, &st) != 0)           /* No config file? */
        || !S_ISREG(st.st_mode)                 /* Not a regular file? */
        || (st.st_uid != 0)                     /* Not owned by root? */
        || (st.st_mode & (S_IWGRP | S_IWOTH))   /* Writable by non-root? */
        || !(f = fopen(config_file, "r"))       /* Can not open? */
        ) {
        return;
    }

    suid_cfg_readable = 1;
    sct_head = NULL;
    section = lc = 0;

    do {
        s = buffer;

        if (!fgets(s, sizeof(buffer), f)) { /* Are we done? */
            if (ferror(f)) {   /* Make sure it wasn't a read error. */
                parse_error("reading");
            }
            fclose(f);
            suid_config = sct_head; /* Success, so set the pointer. */
            return;
        }

        lc++;                   /* Got a (partial) line. */

        /* If a line is too long for our buffer, we consider it an error.
         * The following test does mistreat one corner case though.
         * If the final line of the file does not end with a newline and
         * yet exactly fills the buffer, it will be treated as too long
         * even though there isn't really a problem.  But it isn't really
         * worth adding code to deal with such an unlikely situation, and
         * we do err on the side of caution.  Besides, the line would be
         * too long if it did end with a newline. */
        if (!strchr(s, '\n') && !feof(f)) {
            parse_error("line too long");
        }

        /* Trim leading and trailing whitespace, ignoring comments, and
         * check if the resulting string is empty. */
        if (!*(s = get_trimmed_slice(s, strchrnul(s, '#')))) {
            continue;
        }

        /* Check for a section header. */

        if (*s == '[') {
            /* Unlike the old code, we ignore leading and trailing
             * whitespace for the section name.  We also require that
             * there are no stray characters after the closing bracket. */
            if (!(e = strchr(s, ']'))   /* Missing right bracket? */
                || e[1]                 /* Trailing characters? */
                || !*(s = get_trimmed_slice(s+1, e)) /* Missing name? */
                ) {
                parse_error("section header");
            }
            /* Right now we only have one section so just check it.
             * If more sections are added in the future, please don't
             * resort to cascading ifs with multiple strcasecmp calls.
             * That kind of bloated code is all too common.  A loop
             * and a string table would be a better choice unless the
             * number of sections is very small. */
            if (strcasecmp(s, "SUID") == 0) {
                section = 1;
                continue;
            }
            section = -1;   /* Unknown section so set to skip. */
            continue;
        }

        /* Process sections. */

        if (section == 1) {     /* SUID */
            /* Since we trimmed leading and trailing space above, we're
             * now looking for strings of the form
             *    <key>[::space::]*=[::space::]*<value>
             * where both key and value could contain inner whitespace. */

            /* First get the key (an applet name in our case). */
            if (!!(e = strchr(s, '='))) {
                s = get_trimmed_slice(s, e);
            }
            if (!e || !*s) {    /* Missing '=' or empty key. */
                parse_error("keyword");
            }

            /* Ok, we have an applet name.  Process the rhs if this
             * applet is currently built in and ignore it otherwise.
             * Note: This can hide config file bugs which only pop
             * up when the busybox configuration is changed. */
            if ((applet = find_applet_by_name(s))) {
                /* Note: We currently don't check for duplicates!
                 * The last config line for each applet will be the
                 * one used since we insert at the head of the list.
                 * I suppose this could be considered a feature. */
                sct = xmalloc(sizeof(struct BB_suid_config));
                sct->m_applet = applet;
                sct->m_mode = 0;
                sct->m_next = sct_head;
                sct_head = sct;

                /* Get the specified mode. */

                e = skip_whitespace(e+1);

                for (i=0 ; i < 3 ; i++) {
                    const char *q;
                    if (!*(q = strchrnul(mode_chars + 5*i, *e++))) {
                        parse_error("mode");
                    }
                    /* Adjust by -i to account for nul. */
                    sct->m_mode |= mode_mask[(q - mode_chars) - i];
                }

                /* Now get the the user/group info. */

                s = skip_whitespace(e);

                /* Note: We require whitespace between the mode and the
                 * user/group info. */
                if ((s == e) || !(e = strchr(s, '.'))) {
                    parse_error("<uid>.<gid>");
                }
                *e++ = 0;

                /* We can't use get_ug_id here since it would exit()
                 * if a uid or gid was not found.  Oh well... */
                {
                    char *e2;

                    sct->m_uid = strtoul(s, &e2, 10);
                    if (*e2 || (s == e2)) {
                        struct passwd *pwd;
                        if (!(pwd = getpwnam(s))) {
                            parse_error("user");
                        }
                        sct->m_uid = pwd->pw_uid;
                    }

                    sct->m_gid = strtoul(e, &e2, 10);
                    if (*e2 || (e == e2)) {
                        struct group *grp;
                        if (!(grp = getgrnam(e))) {
                            parse_error("group");
                        }
                        sct->m_gid = grp->gr_gid;
                    }
                }
            }
            continue;
        }

        /* Unknown sections are ignored. */

        /* Encountering configuration lines prior to seeing a
         * section header is treated as an error.  This is how
         * the old code worked, but it may not be desirable.
         * We may want to simply ignore such lines in case they
         * are used in some future version of busybox. */
        if (!section) {
            parse_error("keyword outside section");
        }

    } while (1);

 pe_label:
    fprintf(stderr, "Parse error in %s, line %d: %s\n",
            config_file, lc, err);

    fclose(f);
    /* Release any allocated memory before returning. */
    while (sct_head) {
        sct = sct_head->m_next;
        free(sct_head);
        sct_head = sct;
    }
    return;
}

#else
#define parse_config_file()
#endif /* CONFIG_FEATURE_SUID_CONFIG */

#ifdef CONFIG_FEATURE_SUID
static void check_suid (struct BB_applet *applet)
{
  uid_t ruid = getuid ();               /* real [ug]id */
  uid_t rgid = getgid ();

#ifdef CONFIG_FEATURE_SUID_CONFIG
  if (suid_cfg_readable) {
    struct BB_suid_config *sct;

    for (sct = suid_config; sct; sct = sct->m_next) {
      if (sct->m_applet == applet)
        break;
    }
    if (sct) {
      mode_t m = sct->m_mode;

      if (sct->m_uid == ruid)       /* same uid */
        m >>= 6;
      else if ((sct->m_gid == rgid) || ingroup (ruid, sct->m_gid))  /* same group / in group */
        m >>= 3;

      if (!(m & S_IXOTH))           /* is x bit not set ? */
        bb_error_msg_and_die ("You have no permission to run this applet!");

      if ((sct->m_mode & (S_ISGID | S_IXGRP)) == (S_ISGID | S_IXGRP)) {     /* *both* have to be set for sgid */
        if (setegid (sct->m_gid))
          bb_error_msg_and_die
            ("BusyBox binary has insufficient rights to set proper GID for applet!");
      } else
        setgid (rgid);                  /* no sgid -> drop */

      if (sct->m_mode & S_ISUID) {
        if (seteuid (sct->m_uid))
          bb_error_msg_and_die
            ("BusyBox binary has insufficient rights to set proper UID for applet!");
      } else
        setuid (ruid);                  /* no suid -> drop */
    } else {
        /* default: drop all privileges */
      setgid (rgid);
      setuid (ruid);
    }
    return;
  } else {
#ifndef CONFIG_FEATURE_SUID_CONFIG_QUIET
    static int onetime = 0;

    if (!onetime) {
      onetime = 1;
      fprintf (stderr, "Using fallback suid method\n");
    }
#endif
  }
#endif

  if (applet->need_suid == _BB_SUID_ALWAYS) {
    if (geteuid () != 0)
      bb_error_msg_and_die ("This applet requires root privileges!");
  } else if (applet->need_suid == _BB_SUID_NEVER) {
    setgid (rgid);                          /* drop all privileges */
    setuid (ruid);
  }
}
#else
#define check_suid(x)
#endif /* CONFIG_FEATURE_SUID */



#if ENABLE_FEATURE_COMPRESS_USAGE

#include "usage_compressed.h"
#include "unarchive.h"

static const char *unpack_usage_messages(void)
{
    int input[2], output[2], pid;
    char *buf;

    if(pipe(input) < 0 || pipe(output) < 0)
        exit(1);

    pid = fork();
    switch (pid) {
    case -1: /* error */
        exit(1);
    case 0: /* child */
        close(input[1]);
        close(output[0]);
        uncompressStream(input[0], output[1]);
        exit(0);
    }
    /* parent */

    close(input[0]);
    close(output[1]);
    pid = fork();
    switch (pid) {
    case -1: /* error */
        exit(1);
    case 0: /* child */
        bb_full_write(input[1], packed_usage, sizeof(packed_usage));
        exit(0);
    }
    /* parent */
    close(input[1]);

    buf = xmalloc(SIZEOF_usage_messages);
    bb_full_read(output[0], buf, SIZEOF_usage_messages);
    return buf;
}

#else
#define unpack_usage_messages() usage_messages
#endif /* ENABLE_FEATURE_COMPRESS_USAGE */

void bb_show_usage (void)
{
    if (ENABLE_SHOW_USAGE) {
        const char *format_string;
        const char *usage_string = unpack_usage_messages();
        int i;

        for (i = applet_using - applets; i > 0;)
            if (!*usage_string++) --i;

        format_string = "%s\n\nUsage: %s %s\n\n";
        if (*usage_string == '\b')
            format_string = "%s\n\nNo help available.\n\n";
        fprintf (stderr, format_string, bb_msg_full_version,
            applet_using->name, usage_string);
    }

  exit (bb_default_error_retval);
}

static int applet_name_compare (const void *x, const void *y)
{
  const char *name = x;
  const struct BB_applet *applet = y;

  return strcmp (name, applet->name);
}

extern const size_t NUM_APPLETS;

struct BB_applet *find_applet_by_name (const char *name)
{
  return bsearch (name, applets, NUM_APPLETS, sizeof (struct BB_applet),
                  applet_name_compare);
}

void run_applet_by_name (const char *name, int argc, char **argv)
{
    if(ENABLE_FEATURE_SUID_CONFIG) parse_config_file ();

    if(!strncmp(name, "busybox", 7)) busybox_main(argc, argv);
    /* Do a binary search to find the applet entry given the name. */
    applet_using = find_applet_by_name(name);
    if(applet_using) {
        bb_applet_name = applet_using->name;
        if(argc==2 && !strcmp(argv[1], "--help")) bb_show_usage ();
        if(ENABLE_FEATURE_SUID) check_suid (applet_using);
        exit ((*(applet_using->main)) (argc, argv));
    }
}