diff options
author | Denis Vlasenko <vda.linux@googlemail.com> | 2006-12-27 07:35:04 +0300 |
---|---|---|
committer | Denis Vlasenko <vda.linux@googlemail.com> | 2006-12-27 07:35:04 +0300 |
commit | 8d42f86b146871ae4c4cafd3801a85f381249a14 (patch) | |
tree | b963999fc54eddb65f1929b894f868e24851fc9c /loginutils/login.c |
Correcting branch name to be like previous ones
Diffstat (limited to 'loginutils/login.c')
-rw-r--r-- | loginutils/login.c | 402 |
1 files changed, 402 insertions, 0 deletions
diff --git a/loginutils/login.c b/loginutils/login.c new file mode 100644 index 000000000..bd3c112b9 --- /dev/null +++ b/loginutils/login.c @@ -0,0 +1,402 @@ +/* vi: set sw=4 ts=4: */ +/* + * Licensed under GPLv2 or later, see file LICENSE in this tarball for details. + */ + +#include "busybox.h" +#include <utmp.h> +#include <sys/resource.h> +#include <syslog.h> + +#ifdef CONFIG_SELINUX +#include <selinux/selinux.h> /* for is_selinux_enabled() */ +#include <selinux/get_context_list.h> /* for get_default_context() */ +#include <selinux/flask.h> /* for security class definitions */ +#include <errno.h> +#endif + +enum { + TIMEOUT = 60, + EMPTY_USERNAME_COUNT = 10, + USERNAME_SIZE = 32, + TTYNAME_SIZE = 32, +}; + +static char full_tty[TTYNAME_SIZE]; +static char* short_tty = full_tty; + +#if ENABLE_FEATURE_UTMP +/* vv Taken from tinylogin utmp.c vv */ +/* + * read_or_build_utent - see if utmp file is correct for this process + * + * System V is very picky about the contents of the utmp file + * and requires that a slot for the current process exist. + * The utmp file is scanned for an entry with the same process + * ID. If no entry exists the process exits with a message. + * + * The "picky" flag is for network and other logins that may + * use special flags. It allows the pid checks to be overridden. + * This means that getty should never invoke login with any + * command line flags. + */ + +static struct utmp utent; + +static void read_or_build_utent(int picky) +{ + struct utmp *ut; + pid_t pid = getpid(); + + setutent(); + + /* First, try to find a valid utmp entry for this process. */ + while ((ut = getutent())) + if (ut->ut_pid == pid && ut->ut_line[0] && ut->ut_id[0] && + (ut->ut_type == LOGIN_PROCESS || ut->ut_type == USER_PROCESS)) + break; + + /* If there is one, just use it, otherwise create a new one. */ + if (ut) { + utent = *ut; + } else { + if (picky) + bb_error_msg_and_die("no utmp entry found"); + + memset(&utent, 0, sizeof(utent)); + utent.ut_type = LOGIN_PROCESS; + utent.ut_pid = pid; + strncpy(utent.ut_line, short_tty, sizeof(utent.ut_line)); + /* This one is only 4 chars wide. Try to fit something + * remotely meaningful by skipping "tty"... */ + strncpy(utent.ut_id, short_tty + 3, sizeof(utent.ut_id)); + strncpy(utent.ut_user, "LOGIN", sizeof(utent.ut_user)); + utent.ut_time = time(NULL); + } + if (!picky) /* root login */ + memset(utent.ut_host, 0, sizeof(utent.ut_host)); +} + +/* + * write_utent - put a USER_PROCESS entry in the utmp file + * + * write_utent changes the type of the current utmp entry to + * USER_PROCESS. the wtmp file will be updated as well. + */ +static void write_utent(const char *username) +{ + utent.ut_type = USER_PROCESS; + strncpy(utent.ut_user, username, sizeof(utent.ut_user)); + utent.ut_time = time(NULL); + /* other fields already filled in by read_or_build_utent above */ + setutent(); + pututline(&utent); + endutent(); +#if ENABLE_FEATURE_WTMP + if (access(bb_path_wtmp_file, R_OK|W_OK) == -1) { + close(creat(bb_path_wtmp_file, 0664)); + } + updwtmp(bb_path_wtmp_file, &utent); +#endif +} +#else /* !ENABLE_FEATURE_UTMP */ +static inline void read_or_build_utent(int ATTRIBUTE_UNUSED picky) {} +static inline void write_utent(const char ATTRIBUTE_UNUSED *username) {} +#endif /* !ENABLE_FEATURE_UTMP */ + +static void die_if_nologin_and_non_root(int amroot) +{ + FILE *fp; + int c; + + if (access(bb_path_nologin_file, F_OK)) + return; + + fp = fopen(bb_path_nologin_file, "r"); + if (fp) { + while ((c = getc(fp)) != EOF) + putchar((c=='\n') ? '\r' : c); + fflush(stdout); + fclose(fp); + } else + puts("\r\nSystem closed for routine maintenance\r"); + if (!amroot) + exit(1); + puts("\r\n[Disconnect bypassed -- root login allowed.]\r"); +} + +#if ENABLE_FEATURE_SECURETTY +static int check_securetty(void) +{ + FILE *fp; + int i; + char buf[BUFSIZ]; + + fp = fopen(bb_path_securetty_file, "r"); + if (!fp) { + /* A missing securetty file is not an error. */ + return 1; + } + while (fgets(buf, sizeof(buf)-1, fp)) { + for(i = strlen(buf)-1; i>=0; --i) { + if (!isspace(buf[i])) + break; + } + buf[++i] = '\0'; + if ((buf[0]=='\0') || (buf[0]=='#')) + continue; + if (strcmp(buf, short_tty) == 0) { + fclose(fp); + return 1; + } + } + fclose(fp); + return 0; +} +#else +static inline int check_securetty(void) { return 1; } +#endif + +static void get_username_or_die(char *buf, int size_buf) +{ + int c, cntdown; + cntdown = EMPTY_USERNAME_COUNT; +prompt: + /* skip whitespace */ + print_login_prompt(); + do { + c = getchar(); + if (c == EOF) exit(1); + if (c == '\n') { + if (!--cntdown) exit(1); + goto prompt; + } + } while (isspace(c)); + + *buf++ = c; + if (!fgets(buf, size_buf-2, stdin)) + exit(1); + if (!strchr(buf, '\n')) + exit(1); + while (isgraph(*buf)) buf++; + *buf = '\0'; +} + +static void motd(void) +{ + FILE *fp; + int c; + + fp = fopen(bb_path_motd_file, "r"); + if (fp) { + while ((c = getc(fp)) != EOF) + putchar(c); + fclose(fp); + } +} + +static void nonblock(int fd) +{ + fcntl(fd, F_SETFL, O_NONBLOCK | fcntl(fd, F_GETFL)); +} + +static void alarm_handler(int sig ATTRIBUTE_UNUSED) +{ + /* This is the escape hatch! Poor serial line users and the like + * arrive here when their connection is broken. + * We don't want to block here */ + nonblock(1); + nonblock(2); + bb_info_msg("\r\nLogin timed out after %d seconds\r", TIMEOUT); + exit(EXIT_SUCCESS); +} + +int login_main(int argc, char **argv) +{ + enum { + LOGIN_OPT_f = (1<<0), + LOGIN_OPT_h = (1<<1), + LOGIN_OPT_p = (1<<2), + }; + char fromhost[512]; + char username[USERNAME_SIZE]; + const char *tmp; + int amroot; + unsigned opt; + int count = 0; + struct passwd *pw; + char *opt_host = NULL; + char *opt_user = NULL; + USE_SELINUX(security_context_t user_sid = NULL;) + + username[0] = '\0'; + amroot = (getuid() == 0); + signal(SIGALRM, alarm_handler); + alarm(TIMEOUT); + + opt = getopt32(argc, argv, "f:h:p", &opt_user, &opt_host); + if (opt & LOGIN_OPT_f) { + if (!amroot) + bb_error_msg_and_die("-f is for root only"); + safe_strncpy(username, opt_user, sizeof(username)); + } + if (optind < argc) /* user from command line (getty) */ + safe_strncpy(username, argv[optind], sizeof(username)); + + /* Let's find out and memorize our tty */ + if (!isatty(0) || !isatty(1) || !isatty(2)) + return EXIT_FAILURE; /* Must be a terminal */ + safe_strncpy(full_tty, "UNKNOWN", sizeof(full_tty)); + tmp = ttyname(0); + if (tmp) { + safe_strncpy(full_tty, tmp, sizeof(full_tty)); + if (strncmp(full_tty, "/dev/", 5) == 0) + short_tty = full_tty + 5; + } + + read_or_build_utent(!amroot); + + if (opt_host) { + USE_FEATURE_UTMP( + safe_strncpy(utent.ut_host, opt_host, sizeof(utent.ut_host)); + ) + snprintf(fromhost, sizeof(fromhost)-1, " on '%.100s' from " + "'%.200s'", short_tty, opt_host); + } + else + snprintf(fromhost, sizeof(fromhost)-1, " on '%.100s'", short_tty); + + bb_setpgrp; + + openlog(applet_name, LOG_PID | LOG_CONS | LOG_NOWAIT, LOG_AUTH); + + while (1) { + if (!username[0]) + get_username_or_die(username, sizeof(username)); + + pw = getpwnam(username); + if (!pw) { + safe_strncpy(username, "UNKNOWN", sizeof(username)); + goto auth_failed; + } + + if (pw->pw_passwd[0] == '!' || pw->pw_passwd[0] == '*') + goto auth_failed; + + if (opt & LOGIN_OPT_f) + break; /* -f USER: success without asking passwd */ + + if (pw->pw_uid == 0 && !check_securetty()) + goto auth_failed; + + /* Don't check the password if password entry is empty (!) */ + if (!pw->pw_passwd[0]) + break; + + /* authorization takes place here */ + if (correct_password(pw)) + break; + +auth_failed: + opt &= ~LOGIN_OPT_f; + bb_do_delay(FAIL_DELAY); + puts("Login incorrect"); + if (++count == 3) { + syslog(LOG_WARNING, "invalid password for '%s'%s", + username, fromhost); + return EXIT_FAILURE; + } + username[0] = '\0'; + } + + alarm(0); + die_if_nologin_and_non_root(pw->pw_uid == 0); + + write_utent(username); + +#ifdef CONFIG_SELINUX + if (is_selinux_enabled()) { + security_context_t old_tty_sid, new_tty_sid; + + if (get_default_context(username, NULL, &user_sid)) { + bb_error_msg_and_die("cannot get SID for %s", + username); + } + if (getfilecon(full_tty, &old_tty_sid) < 0) { + bb_perror_msg_and_die("getfilecon(%s) failed", + full_tty); + } + if (security_compute_relabel(user_sid, old_tty_sid, + SECCLASS_CHR_FILE, &new_tty_sid) != 0) { + bb_perror_msg_and_die("security_change_sid(%s) failed", + full_tty); + } + if (setfilecon(full_tty, new_tty_sid) != 0) { + bb_perror_msg_and_die("chsid(%s, %s) failed", + full_tty, new_tty_sid); + } + } +#endif + /* Try these, but don't complain if they fail. + * _f_chown is safe wrt race t=ttyname(0);...;chown(t); */ + fchown(0, pw->pw_uid, pw->pw_gid); + fchmod(0, 0600); + + /* TODO: be nommu-friendly, use spawn? */ + if (ENABLE_LOGIN_SCRIPTS) { + char *script = getenv("LOGIN_PRE_SUID_SCRIPT"); + if (script) { + char *t_argv[2] = { script, NULL }; + switch (fork()) { + case -1: break; + case 0: /* child */ + xchdir("/"); + setenv("LOGIN_TTY", full_tty, 1); + setenv("LOGIN_USER", pw->pw_name, 1); + setenv("LOGIN_UID", utoa(pw->pw_uid), 1); + setenv("LOGIN_GID", utoa(pw->pw_gid), 1); + setenv("LOGIN_SHELL", pw->pw_shell, 1); + execvp(script, t_argv); + exit(1); + default: /* parent */ + wait(NULL); + } + } + } + + change_identity(pw); + tmp = pw->pw_shell; + if (!tmp || !*tmp) + tmp = DEFAULT_SHELL; + setup_environment(tmp, 1, !(opt & LOGIN_OPT_p), pw); + + motd(); + + if (pw->pw_uid == 0) + syslog(LOG_INFO, "root login%s", fromhost); +#ifdef CONFIG_SELINUX + /* well, a simple setexeccon() here would do the job as well, + * but let's play the game for now */ + set_current_security_context(user_sid); +#endif + + // util-linux login also does: + // /* start new session */ + // setsid(); + // /* TIOCSCTTY: steal tty from other process group */ + // if (ioctl(0, TIOCSCTTY, 1)) error_msg... + + /* set signals to defaults */ + signal(SIGALRM, SIG_DFL); + /* Is this correct? This way user can ctrl-c out of /etc/profile, + * potentially creating security breach (tested with bash 3.0). + * But without this, bash 3.0 will not enable ctrl-c either. + * Maybe bash is buggy? + * Need to find out what standards say about /bin/login - + * should it leave SIGINT etc enabled or disabled? */ + signal(SIGINT, SIG_DFL); + + run_shell(tmp, 1, 0, 0); /* exec the shell finally */ + + return EXIT_FAILURE; +} |