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/* setgrp.c - by Michael Haardt. Set the gid if possible
* Added a bit more error recovery/reporting - poe
* Vesa Roukonen added code for asking password */
/* 1999-02-22 Arkadiusz Miśkiewicz <misiek@pld.ORG.PL>
* - added Native Language Support
*/
#include <errno.h>
#include <getopt.h>
#include <grp.h>
#include <pwd.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <termios.h>
#include <unistd.h>
#ifdef HAVE_CRYPT_H
# include <crypt.h>
#endif
#ifdef HAVE_GETSGNAM
# include <gshadow.h>
#endif
#include "c.h"
#include "closestream.h"
#include "nls.h"
#include "pathnames.h"
#include "xalloc.h"
static char *xgetpass(FILE *input, const char *prompt)
{
char *pass = NULL;
struct termios saved, no_echo;
const int fd = fileno(input);
size_t dummy = 0;
ssize_t len;
fputs(prompt, stdout);
if (isatty(fd)) {
/* disable echo */
tcgetattr(fd, &saved);
no_echo = saved;
no_echo.c_lflag &= ~ECHO;
no_echo.c_lflag |= ECHONL;
if (tcsetattr(fd, TCSANOW, &no_echo))
err(EXIT_FAILURE, _("could not set terminal attributes"));
}
len = getline(&pass, &dummy, input);
if (isatty(fd))
/* restore terminal */
if (tcsetattr(fd, TCSANOW, &saved))
err(EXIT_FAILURE, _("could not set terminal attributes"));
if (len < 0)
err(EXIT_FAILURE, _("getline() failed"));
if (0 < len && *(pass + len - 1) == '\n')
*(pass + len - 1) = '\0';
return pass;
}
#ifndef HAVE_EXPLICIT_BZERO
/* Ensure memory is set to value c without compiler optimization getting
* into way that could happen with memset(3). */
static int xmemset_s(void *v, size_t sz, const int c)
{
volatile unsigned char *p = v;
if (v == NULL)
return EINVAL;
while (sz--)
*p++ = c;
return 0;
}
#endif
/* try to read password from gshadow */
static char *get_gshadow_pwd(const char *groupname)
{
#ifdef HAVE_GETSGNAM
struct sgrp *sgrp;
sgrp = getsgnam(groupname);
return sgrp ? xstrdup(sgrp->sg_passwd) : NULL;
#else
char buf[BUFSIZ];
char *pwd = NULL;
FILE *f;
if (groupname == NULL || *groupname == '\0')
return NULL;
f = fopen(_PATH_GSHADOW, "r");
if (!f)
return NULL;
while (fgets(buf, sizeof buf, f)) {
char *cp = strchr(buf, ':');
if (!cp)
/* any junk in gshadow? */
continue;
*cp = '\0';
if (strcmp(buf, groupname) == 0) {
if (cp - buf >= BUFSIZ)
/* only group name on line */
break;
pwd = cp + 1;
if ((cp = strchr(pwd, ':')) && pwd == cp + 1)
/* empty password */
pwd = NULL;
else if (cp)
*cp = '\0';
break;
}
}
fclose(f);
return pwd ? xstrdup(pwd) : NULL;
#endif /* HAVE_GETSGNAM */
}
static int allow_setgid(const struct passwd *pe, const struct group *ge)
{
char **look;
int notfound = 1;
char *pwd, *xpwd;
if (getuid() == 0)
/* root may do anything */
return TRUE;
if (ge->gr_gid == pe->pw_gid)
/* You can switch back to your default group */
return TRUE;
look = ge->gr_mem;
while (*look && (notfound = strcmp(*look++, pe->pw_name))) ;
if (!notfound)
/* member of group => OK */
return TRUE;
/* Ask for password. Often there is no password in /etc/group, so
* contrary to login et al. we let an empty password mean the same
* as in /etc/passwd */
/* check /etc/gshadow */
if (!(pwd = get_gshadow_pwd(ge->gr_name)))
pwd = ge->gr_passwd;
if (pwd && *pwd && (xpwd = xgetpass(stdin, _("Password: ")))) {
char *cbuf = crypt(xpwd, pwd);
#ifdef HAVE_EXPLICIT_BZERO
explicit_bzero(xpwd, strlen(xpwd));
#else
xmemset_s(xpwd, strlen(xpwd), 0);
#endif
free(xpwd);
if (!cbuf)
warn(_("crypt failed"));
else if (strcmp(pwd, cbuf) == 0)
return TRUE;
}
/* default to denial */
return FALSE;
}
static void __attribute__((__noreturn__)) usage(void)
{
FILE *out = stdout;
fputs(USAGE_HEADER, out);
fprintf(out, _(" %s <group>\n"), program_invocation_short_name);
fputs(USAGE_SEPARATOR, out);
fputs(_("Log in to a new group.\n"), out);
fputs(USAGE_OPTIONS, out);
printf(USAGE_HELP_OPTIONS(16));
printf(USAGE_MAN_TAIL("newgrp(1)"));
exit(EXIT_SUCCESS);
}
int main(int argc, char *argv[])
{
struct passwd *pw_entry;
struct group *gr_entry;
char *shell;
int ch;
static const struct option longopts[] = {
{"version", no_argument, NULL, 'V'},
{"help", no_argument, NULL, 'h'},
{NULL, 0, NULL, 0}
};
setlocale(LC_ALL, "");
bindtextdomain(PACKAGE, LOCALEDIR);
textdomain(PACKAGE);
atexit(close_stdout);
while ((ch = getopt_long(argc, argv, "Vh", longopts, NULL)) != -1)
switch (ch) {
case 'V':
printf(UTIL_LINUX_VERSION);
return EXIT_SUCCESS;
case 'h':
usage();
default:
errtryhelp(EXIT_FAILURE);
}
if (!(pw_entry = getpwuid(getuid())))
err(EXIT_FAILURE, _("who are you?"));
if (argc < 2) {
if (setgid(pw_entry->pw_gid) < 0)
err(EXIT_FAILURE, _("setgid failed"));
} else {
errno = 0;
if (!(gr_entry = getgrnam(argv[1]))) {
if (errno)
err(EXIT_FAILURE, _("no such group"));
else
errx(EXIT_FAILURE, _("no such group"));
}
if (!allow_setgid(pw_entry, gr_entry))
errx(EXIT_FAILURE, _("permission denied"));
if (setgid(gr_entry->gr_gid) < 0)
err(EXIT_FAILURE, _("setgid failed"));
}
if (setuid(getuid()) < 0)
err(EXIT_FAILURE, _("setuid failed"));
fflush(NULL);
shell = (pw_entry->pw_shell && *pw_entry->pw_shell ?
pw_entry->pw_shell : _PATH_BSHELL);
execl(shell, shell, (char *)0);
errexec(shell);
}
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