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/* chsh.c - Change login shell.
*
* Copyright 2021 Michael Christensen
*
* See http://refspecs.linuxfoundation.org/LSB_4.1.0/LSB-Core-generic/LSB-Core-generic/chsh.html
USE_CHSH(NEWTOY(chsh, "s:", TOYFLAG_USR|TOYFLAG_BIN|TOYFLAG_STAYROOT))
config CHSH
bool "chsh"
default y
help
usage: chsh [-s SHELL] [USER]
Change user's login shell.
-s Use SHELL instead of prompting
Non-root users can only change their own shell to one listed in /etc/shells.
*/
#define FOR_chsh
#include "toys.h"
GLOBALS(
char *s;
)
void chsh_main()
{
FILE *file;
char *user, *line, *shell, *encrypted;
struct passwd *passwd_info;
struct spwd *shadow_info;
// Get uid user information, may be discarded later
if ((user = *toys.optargs)) {
passwd_info = xgetpwnam(user);
if (geteuid() && strcmp(passwd_info->pw_name, user))
error_exit("Permission denied\n");
} else {
passwd_info = xgetpwuid(getuid());
user = passwd_info->pw_name;
}
// Get a password, encrypt it, wipe it, and check it
if (mlock(toybuf, sizeof(toybuf))) perror_exit("mlock");
if (!(shadow_info = getspnam(passwd_info->pw_name))) perror_exit("getspnam");
if (read_password(toybuf, sizeof(toybuf), "Password: ")) perror_exit("woaj"); //xexit();
if (!(encrypted = crypt(toybuf, shadow_info->sp_pwdp))) perror_exit("crypt");
memset(toybuf, 0, sizeof(toybuf));
munlock(toybuf, sizeof(toybuf)); // prevents memset from "optimizing" away.
if (strcmp(encrypted, shadow_info->sp_pwdp)) perror_exit("Bad password");
// Get new shell (either -s or interactive)
file = xfopen("/etc/shells", "r");
if (toys.optflags) shell = TT.s;
else {
xprintf("Changing the login shell for %s\n"
"Enter the new value, or press ENTER for default\n"
" Login shell [%s]: ", user, passwd_info->pw_shell);
if (!(shell = xgetline(stdin))) xexit();
}
// Verify supplied shell in /etc/shells, or get default shell
if (strlen(shell))
while ((line = xgetline(file)) && strcmp(shell, line)) free(line);
else do line = xgetline(file); while (line && *line != '/');
if (!line) error_exit("Shell not found in '/etc/shells'");
// Update /etc/passwd
passwd_info->pw_shell = line;
if (-1 == update_password("/etc/passwd", user, NULL)) perror_exit("Failed to remove passwd entry");
file = xfopen("/etc/passwd", "a");
if (putpwent(passwd_info, file)) perror_exit("putwent");
}
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