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