1 | /* vi: set sw=4 ts=4: */
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2 | /*
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3 | * Licensed under GPLv2 or later, see file LICENSE in this source tree.
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4 | */
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5 | #include "libbb.h"
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6 | #include <syslog.h>
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7 | #if ENABLE_FEATURE_UTMP
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8 | # include <utmp.h> /* USER_PROCESS */
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9 | #endif
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10 | #include <sys/resource.h>
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11 |
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12 | #if ENABLE_SELINUX
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13 | # include <selinux/selinux.h> /* for is_selinux_enabled() */
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14 | # include <selinux/get_context_list.h> /* for get_default_context() */
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15 | # include <selinux/flask.h> /* for security class definitions */
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16 | #endif
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17 |
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18 | #if ENABLE_PAM
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19 | /* PAM may include <locale.h>. We may need to undefine bbox's stub define: */
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20 | # undef setlocale
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21 | /* For some obscure reason, PAM is not in pam/xxx, but in security/xxx.
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22 | * Apparently they like to confuse people. */
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23 | # include <security/pam_appl.h>
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24 | # include <security/pam_misc.h>
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25 | static const struct pam_conv conv = {
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26 | misc_conv,
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27 | NULL
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28 | };
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29 | #endif
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30 |
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31 | enum {
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32 | TIMEOUT = 60,
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33 | EMPTY_USERNAME_COUNT = 10,
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34 | USERNAME_SIZE = 32,
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35 | TTYNAME_SIZE = 32,
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36 | };
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37 |
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38 | static char* short_tty;
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39 |
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40 | #if ENABLE_FEATURE_NOLOGIN
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41 | static void die_if_nologin(void)
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42 | {
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43 | FILE *fp;
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44 | int c;
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45 | int empty = 1;
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46 |
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47 | fp = fopen_for_read("/etc/nologin");
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48 | if (!fp) /* assuming it does not exist */
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49 | return;
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50 |
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51 | while ((c = getc(fp)) != EOF) {
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52 | if (c == '\n')
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53 | bb_putchar('\r');
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54 | bb_putchar(c);
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55 | empty = 0;
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56 | }
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57 | if (empty)
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58 | puts("\r\nSystem closed for routine maintenance\r");
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59 |
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60 | fclose(fp);
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61 | fflush_all();
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62 | /* Users say that they do need this prior to exit: */
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63 | tcdrain(STDOUT_FILENO);
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64 | exit(EXIT_FAILURE);
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65 | }
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66 | #else
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67 | # define die_if_nologin() ((void)0)
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68 | #endif
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69 |
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70 | #if ENABLE_FEATURE_SECURETTY && !ENABLE_PAM
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71 | static int check_securetty(void)
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72 | {
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73 | char *buf = (char*)"/etc/securetty"; /* any non-NULL is ok */
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74 | parser_t *parser = config_open2("/etc/securetty", fopen_for_read);
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75 | while (config_read(parser, &buf, 1, 1, "# \t", PARSE_NORMAL)) {
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76 | if (strcmp(buf, short_tty) == 0)
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77 | break;
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78 | buf = NULL;
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79 | }
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80 | config_close(parser);
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81 | /* buf != NULL here if config file was not found, empty
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82 | * or line was found which equals short_tty */
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83 | return buf != NULL;
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84 | }
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85 | #else
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86 | static ALWAYS_INLINE int check_securetty(void) { return 1; }
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87 | #endif
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88 |
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89 | #if ENABLE_SELINUX
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90 | static void initselinux(char *username, char *full_tty,
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91 | security_context_t *user_sid)
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92 | {
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93 | security_context_t old_tty_sid, new_tty_sid;
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94 |
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95 | if (!is_selinux_enabled())
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96 | return;
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97 |
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98 | if (get_default_context(username, NULL, user_sid)) {
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99 | bb_error_msg_and_die("can't get SID for %s", username);
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100 | }
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101 | if (getfilecon(full_tty, &old_tty_sid) < 0) {
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102 | bb_perror_msg_and_die("getfilecon(%s) failed", full_tty);
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103 | }
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104 | if (security_compute_relabel(*user_sid, old_tty_sid,
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105 | SECCLASS_CHR_FILE, &new_tty_sid) != 0) {
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106 | bb_perror_msg_and_die("security_change_sid(%s) failed", full_tty);
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107 | }
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108 | if (setfilecon(full_tty, new_tty_sid) != 0) {
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109 | bb_perror_msg_and_die("chsid(%s, %s) failed", full_tty, new_tty_sid);
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110 | }
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111 | }
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112 | #endif
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113 |
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114 | #if ENABLE_LOGIN_SCRIPTS
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115 | static void run_login_script(struct passwd *pw, char *full_tty)
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116 | {
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117 | char *t_argv[2];
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118 |
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119 | t_argv[0] = getenv("LOGIN_PRE_SUID_SCRIPT");
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120 | if (t_argv[0]) {
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121 | t_argv[1] = NULL;
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122 | xsetenv("LOGIN_TTY", full_tty);
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123 | xsetenv("LOGIN_USER", pw->pw_name);
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124 | xsetenv("LOGIN_UID", utoa(pw->pw_uid));
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125 | xsetenv("LOGIN_GID", utoa(pw->pw_gid));
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126 | xsetenv("LOGIN_SHELL", pw->pw_shell);
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127 | spawn_and_wait(t_argv); /* NOMMU-friendly */
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128 | unsetenv("LOGIN_TTY");
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129 | unsetenv("LOGIN_USER");
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130 | unsetenv("LOGIN_UID");
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131 | unsetenv("LOGIN_GID");
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132 | unsetenv("LOGIN_SHELL");
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133 | }
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134 | }
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135 | #else
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136 | void run_login_script(struct passwd *pw, char *full_tty);
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137 | #endif
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138 |
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139 | static void get_username_or_die(char *buf, int size_buf)
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140 | {
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141 | int c, cntdown;
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142 |
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143 | cntdown = EMPTY_USERNAME_COUNT;
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144 | prompt:
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145 | print_login_prompt();
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146 | /* skip whitespace */
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147 | do {
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148 | c = getchar();
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149 | if (c == EOF)
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150 | exit(EXIT_FAILURE);
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151 | if (c == '\n') {
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152 | if (!--cntdown)
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153 | exit(EXIT_FAILURE);
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154 | goto prompt;
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155 | }
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156 | } while (isspace(c)); /* maybe isblank? */
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157 |
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158 | *buf++ = c;
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159 | if (!fgets(buf, size_buf-2, stdin))
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160 | exit(EXIT_FAILURE);
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161 | if (!strchr(buf, '\n'))
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162 | exit(EXIT_FAILURE);
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163 | while ((unsigned char)*buf > ' ')
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164 | buf++;
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165 | *buf = '\0';
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166 | }
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167 |
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168 | static void motd(void)
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169 | {
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170 | int fd;
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171 |
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172 | fd = open(bb_path_motd_file, O_RDONLY);
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173 | if (fd >= 0) {
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174 | fflush_all();
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175 | bb_copyfd_eof(fd, STDOUT_FILENO);
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176 | close(fd);
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177 | }
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178 | }
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179 |
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180 | static void alarm_handler(int sig UNUSED_PARAM)
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181 | {
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182 | /* This is the escape hatch! Poor serial line users and the like
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183 | * arrive here when their connection is broken.
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184 | * We don't want to block here */
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185 | ndelay_on(1);
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186 | printf("\r\nLogin timed out after %d seconds\r\n", TIMEOUT);
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187 | fflush_all();
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188 | /* unix API is brain damaged regarding O_NONBLOCK,
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189 | * we should undo it, or else we can affect other processes */
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190 | ndelay_off(1);
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191 | _exit(EXIT_SUCCESS);
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192 | }
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193 |
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194 | int login_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
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195 | int login_main(int argc UNUSED_PARAM, char **argv)
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196 | {
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197 | enum {
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198 | LOGIN_OPT_f = (1<<0),
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199 | LOGIN_OPT_h = (1<<1),
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200 | LOGIN_OPT_p = (1<<2),
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201 | };
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202 | char *fromhost;
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203 | char username[USERNAME_SIZE];
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204 | const char *shell;
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205 | int run_by_root;
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206 | unsigned opt;
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207 | int count = 0;
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208 | struct passwd *pw;
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209 | char *opt_host = NULL;
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210 | char *opt_user = opt_user; /* for compiler */
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211 | char *full_tty;
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212 | IF_SELINUX(security_context_t user_sid = NULL;)
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213 | #if ENABLE_PAM
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214 | int pamret;
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215 | pam_handle_t *pamh;
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216 | const char *pamuser;
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217 | const char *failed_msg;
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218 | struct passwd pwdstruct;
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219 | char pwdbuf[256];
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220 | #endif
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221 |
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222 | username[0] = '\0';
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223 | signal(SIGALRM, alarm_handler);
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224 | alarm(TIMEOUT);
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225 |
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226 | /* More of suid paranoia if called by non-root: */
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227 | /* Clear dangerous stuff, set PATH */
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228 | run_by_root = !sanitize_env_if_suid();
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229 |
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230 | /* Mandatory paranoia for suid applet:
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231 | * ensure that fd# 0,1,2 are opened (at least to /dev/null)
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232 | * and any extra open fd's are closed.
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233 | * (The name of the function is misleading. Not daemonizing here.) */
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234 | bb_daemonize_or_rexec(DAEMON_ONLY_SANITIZE | DAEMON_CLOSE_EXTRA_FDS, NULL);
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235 |
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236 | opt = getopt32(argv, "f:h:p", &opt_user, &opt_host);
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237 | if (opt & LOGIN_OPT_f) {
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238 | if (!run_by_root)
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239 | bb_error_msg_and_die("-f is for root only");
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240 | safe_strncpy(username, opt_user, sizeof(username));
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241 | }
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242 | argv += optind;
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243 | if (argv[0]) /* user from command line (getty) */
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244 | safe_strncpy(username, argv[0], sizeof(username));
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245 |
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246 | /* Let's find out and memorize our tty */
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247 | if (!isatty(STDIN_FILENO) || !isatty(STDOUT_FILENO) || !isatty(STDERR_FILENO))
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248 | return EXIT_FAILURE; /* Must be a terminal */
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249 | full_tty = xmalloc_ttyname(STDIN_FILENO);
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250 | if (!full_tty)
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251 | full_tty = xstrdup("UNKNOWN");
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252 | short_tty = skip_dev_pfx(full_tty);
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253 |
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254 | if (opt_host) {
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255 | fromhost = xasprintf(" on '%s' from '%s'", short_tty, opt_host);
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256 | } else {
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257 | fromhost = xasprintf(" on '%s'", short_tty);
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258 | }
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259 |
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260 | /* Was breaking "login <username>" from shell command line: */
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261 | /*bb_setpgrp();*/
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262 |
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263 | openlog(applet_name, LOG_PID | LOG_CONS, LOG_AUTH);
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264 |
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265 | while (1) {
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266 | /* flush away any type-ahead (as getty does) */
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267 | tcflush(0, TCIFLUSH);
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268 |
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269 | if (!username[0])
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270 | get_username_or_die(username, sizeof(username));
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271 |
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272 | #if ENABLE_PAM
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273 | pamret = pam_start("login", username, &conv, &pamh);
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274 | if (pamret != PAM_SUCCESS) {
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275 | failed_msg = "start";
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276 | goto pam_auth_failed;
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277 | }
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278 | /* set TTY (so things like securetty work) */
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279 | pamret = pam_set_item(pamh, PAM_TTY, short_tty);
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280 | if (pamret != PAM_SUCCESS) {
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281 | failed_msg = "set_item(TTY)";
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282 | goto pam_auth_failed;
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283 | }
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284 | pamret = pam_authenticate(pamh, 0);
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285 | if (pamret != PAM_SUCCESS) {
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286 | failed_msg = "authenticate";
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287 | goto pam_auth_failed;
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288 | /* TODO: or just "goto auth_failed"
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289 | * since user seems to enter wrong password
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290 | * (in this case pamret == 7)
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291 | */
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292 | }
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293 | /* check that the account is healthy */
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294 | pamret = pam_acct_mgmt(pamh, 0);
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295 | if (pamret != PAM_SUCCESS) {
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296 | failed_msg = "acct_mgmt";
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297 | goto pam_auth_failed;
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298 | }
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299 | /* read user back */
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300 | pamuser = NULL;
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301 | /* gcc: "dereferencing type-punned pointer breaks aliasing rules..."
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302 | * thus we cast to (void*) */
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303 | if (pam_get_item(pamh, PAM_USER, (void*)&pamuser) != PAM_SUCCESS) {
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304 | failed_msg = "get_item(USER)";
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305 | goto pam_auth_failed;
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306 | }
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307 | if (!pamuser || !pamuser[0])
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308 | goto auth_failed;
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309 | safe_strncpy(username, pamuser, sizeof(username));
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310 | /* Don't use "pw = getpwnam(username);",
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311 | * PAM is said to be capable of destroying static storage
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312 | * used by getpwnam(). We are using safe(r) function */
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313 | pw = NULL;
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314 | getpwnam_r(username, &pwdstruct, pwdbuf, sizeof(pwdbuf), &pw);
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315 | if (!pw)
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316 | goto auth_failed;
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317 | pamret = pam_open_session(pamh, 0);
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318 | if (pamret != PAM_SUCCESS) {
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319 | failed_msg = "open_session";
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320 | goto pam_auth_failed;
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321 | }
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322 | pamret = pam_setcred(pamh, PAM_ESTABLISH_CRED);
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323 | if (pamret != PAM_SUCCESS) {
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324 | failed_msg = "setcred";
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325 | goto pam_auth_failed;
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326 | }
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327 | break; /* success, continue login process */
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328 |
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329 | pam_auth_failed:
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330 | /* syslog, because we don't want potential attacker
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331 | * to know _why_ login failed */
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332 | syslog(LOG_WARNING, "pam_%s call failed: %s (%d)", failed_msg,
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333 | pam_strerror(pamh, pamret), pamret);
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334 | safe_strncpy(username, "UNKNOWN", sizeof(username));
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335 | #else /* not PAM */
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336 | pw = getpwnam(username);
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337 | if (!pw) {
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338 | strcpy(username, "UNKNOWN");
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339 | goto fake_it;
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340 | }
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341 |
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342 | if (pw->pw_passwd[0] == '!' || pw->pw_passwd[0] == '*')
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343 | goto auth_failed;
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344 |
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345 | if (opt & LOGIN_OPT_f)
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346 | break; /* -f USER: success without asking passwd */
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347 |
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348 | if (pw->pw_uid == 0 && !check_securetty())
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349 | goto auth_failed;
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350 |
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351 | /* Don't check the password if password entry is empty (!) */
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352 | if (!pw->pw_passwd[0])
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353 | break;
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354 | fake_it:
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355 | /* authorization takes place here */
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356 | if (correct_password(pw))
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357 | break;
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358 | #endif /* ENABLE_PAM */
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359 | auth_failed:
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360 | opt &= ~LOGIN_OPT_f;
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361 | bb_do_delay(FAIL_DELAY);
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362 | /* TODO: doesn't sound like correct English phrase to me */
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363 | puts("Login incorrect");
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364 | if (++count == 3) {
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365 | syslog(LOG_WARNING, "invalid password for '%s'%s",
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366 | username, fromhost);
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367 |
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368 | if (ENABLE_FEATURE_CLEAN_UP)
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369 | free(fromhost);
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370 |
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371 | return EXIT_FAILURE;
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372 | }
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373 | username[0] = '\0';
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374 | } /* while (1) */
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375 |
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376 | alarm(0);
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377 | /* We can ignore /etc/nologin if we are logging in as root,
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378 | * it doesn't matter whether we are run by root or not */
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379 | if (pw->pw_uid != 0)
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380 | die_if_nologin();
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381 |
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382 | IF_SELINUX(initselinux(username, full_tty, &user_sid));
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383 |
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384 | /* Try these, but don't complain if they fail.
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385 | * _f_chown is safe wrt race t=ttyname(0);...;chown(t); */
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386 | fchown(0, pw->pw_uid, pw->pw_gid);
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387 | fchmod(0, 0600);
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388 |
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389 | update_utmp(getpid(), USER_PROCESS, short_tty, username, run_by_root ? opt_host : NULL);
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390 |
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391 | /* We trust environment only if we run by root */
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392 | if (ENABLE_LOGIN_SCRIPTS && run_by_root)
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393 | run_login_script(pw, full_tty);
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394 |
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395 | change_identity(pw);
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396 | shell = pw->pw_shell;
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397 | if (!shell || !shell[0])
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398 | shell = DEFAULT_SHELL;
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399 | setup_environment(shell,
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400 | (!(opt & LOGIN_OPT_p) * SETUP_ENV_CLEARENV) + SETUP_ENV_CHANGEENV,
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401 | pw);
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402 |
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403 | motd();
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404 |
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405 | if (pw->pw_uid == 0)
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406 | syslog(LOG_INFO, "root login%s", fromhost);
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407 |
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408 | if (ENABLE_FEATURE_CLEAN_UP)
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409 | free(fromhost);
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410 |
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411 | /* well, a simple setexeccon() here would do the job as well,
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412 | * but let's play the game for now */
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413 | IF_SELINUX(set_current_security_context(user_sid);)
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414 |
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415 | // util-linux login also does:
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416 | // /* start new session */
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417 | // setsid();
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418 | // /* TIOCSCTTY: steal tty from other process group */
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419 | // if (ioctl(0, TIOCSCTTY, 1)) error_msg...
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420 | // BBox login used to do this (see above):
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421 | // bb_setpgrp();
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422 | // If this stuff is really needed, add it and explain why!
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423 |
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424 | /* Set signals to defaults */
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425 | /* Non-ignored signals revert to SIG_DFL on exec anyway */
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426 | /*signal(SIGALRM, SIG_DFL);*/
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427 |
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428 | /* Is this correct? This way user can ctrl-c out of /etc/profile,
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429 | * potentially creating security breach (tested with bash 3.0).
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430 | * But without this, bash 3.0 will not enable ctrl-c either.
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431 | * Maybe bash is buggy?
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432 | * Need to find out what standards say about /bin/login -
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433 | * should we leave SIGINT etc enabled or disabled? */
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434 | signal(SIGINT, SIG_DFL);
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435 |
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436 | /* Exec login shell with no additional parameters */
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437 | run_shell(shell, 1, NULL, NULL);
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438 |
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439 | /* return EXIT_FAILURE; - not reached */
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440 | }
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