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 tarball for details.
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4 | */
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5 |
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6 | #include "libbb.h"
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7 | #include <utmp.h>
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8 | #include <sys/resource.h>
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9 | #include <syslog.h>
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10 |
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11 | #if ENABLE_SELINUX
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12 | #include <selinux/selinux.h> /* for is_selinux_enabled() */
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13 | #include <selinux/get_context_list.h> /* for get_default_context() */
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14 | #include <selinux/flask.h> /* for security class definitions */
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15 | #endif
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16 |
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17 | #if ENABLE_PAM
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18 | /* PAM may include <locale.h>. We may need to undefine bbox's stub define: */
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19 | #undef setlocale
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20 | /* For some obscure reason, PAM is not in pam/xxx, but in security/xxx.
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21 | * Apparently they like to confuse people. */
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22 | #include <security/pam_appl.h>
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23 | #include <security/pam_misc.h>
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24 | static const struct pam_conv conv = {
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25 | misc_conv,
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26 | NULL
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27 | };
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28 | #endif
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29 |
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30 | enum {
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31 | TIMEOUT = 60,
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32 | EMPTY_USERNAME_COUNT = 10,
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33 | USERNAME_SIZE = 32,
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34 | TTYNAME_SIZE = 32,
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35 | };
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36 |
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37 | static char* short_tty;
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38 |
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39 | #if ENABLE_FEATURE_UTMP
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40 | /* vv Taken from tinylogin utmp.c vv */
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41 | /*
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42 | * read_or_build_utent - see if utmp file is correct for this process
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43 | *
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44 | * System V is very picky about the contents of the utmp file
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45 | * and requires that a slot for the current process exist.
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46 | * The utmp file is scanned for an entry with the same process
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47 | * ID. If no entry exists the process exits with a message.
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48 | *
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49 | * The "picky" flag is for network and other logins that may
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50 | * use special flags. It allows the pid checks to be overridden.
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51 | * This means that getty should never invoke login with any
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52 | * command line flags.
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53 | */
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54 |
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55 | static void read_or_build_utent(struct utmp *utptr, int picky)
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56 | {
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57 | struct utmp *ut;
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58 | pid_t pid = getpid();
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59 |
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60 | setutent();
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61 |
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62 | /* First, try to find a valid utmp entry for this process. */
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63 | while ((ut = getutent()))
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64 | if (ut->ut_pid == pid && ut->ut_line[0] && ut->ut_id[0] &&
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65 | (ut->ut_type == LOGIN_PROCESS || ut->ut_type == USER_PROCESS))
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66 | break;
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67 |
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68 | /* If there is one, just use it, otherwise create a new one. */
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69 | if (ut) {
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70 | *utptr = *ut;
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71 | } else {
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72 | if (picky)
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73 | bb_error_msg_and_die("no utmp entry found");
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74 |
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75 | memset(utptr, 0, sizeof(*utptr));
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76 | utptr->ut_type = LOGIN_PROCESS;
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77 | utptr->ut_pid = pid;
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78 | strncpy(utptr->ut_line, short_tty, sizeof(utptr->ut_line));
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79 | /* This one is only 4 chars wide. Try to fit something
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80 | * remotely meaningful by skipping "tty"... */
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81 | strncpy(utptr->ut_id, short_tty + 3, sizeof(utptr->ut_id));
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82 | strncpy(utptr->ut_user, "LOGIN", sizeof(utptr->ut_user));
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83 | utptr->ut_time = time(NULL);
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84 | }
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85 | if (!picky) /* root login */
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86 | memset(utptr->ut_host, 0, sizeof(utptr->ut_host));
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87 | }
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88 |
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89 | /*
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90 | * write_utent - put a USER_PROCESS entry in the utmp file
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91 | *
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92 | * write_utent changes the type of the current utmp entry to
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93 | * USER_PROCESS. the wtmp file will be updated as well.
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94 | */
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95 | static void write_utent(struct utmp *utptr, const char *username)
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96 | {
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97 | utptr->ut_type = USER_PROCESS;
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98 | strncpy(utptr->ut_user, username, sizeof(utptr->ut_user));
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99 | utptr->ut_time = time(NULL);
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100 | /* other fields already filled in by read_or_build_utent above */
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101 | setutent();
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102 | pututline(utptr);
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103 | endutent();
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104 | #if ENABLE_FEATURE_WTMP
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105 | if (access(bb_path_wtmp_file, R_OK|W_OK) == -1) {
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106 | close(creat(bb_path_wtmp_file, 0664));
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107 | }
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108 | updwtmp(bb_path_wtmp_file, utptr);
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109 | #endif
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110 | }
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111 | #else /* !ENABLE_FEATURE_UTMP */
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112 | #define read_or_build_utent(utptr, picky) ((void)0)
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113 | #define write_utent(utptr, username) ((void)0)
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114 | #endif /* !ENABLE_FEATURE_UTMP */
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115 |
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116 | #if ENABLE_FEATURE_NOLOGIN
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117 | static void die_if_nologin_and_non_root(int amroot)
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118 | {
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119 | FILE *fp;
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120 | int c;
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121 |
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122 | if (access("/etc/nologin", F_OK))
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123 | return;
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124 |
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125 | fp = fopen("/etc/nologin", "r");
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126 | if (fp) {
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127 | while ((c = getc(fp)) != EOF)
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128 | putchar((c=='\n') ? '\r' : c);
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129 | fflush(stdout);
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130 | fclose(fp);
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131 | } else
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132 | puts("\r\nSystem closed for routine maintenance\r");
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133 | if (!amroot)
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134 | exit(1);
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135 | puts("\r\n[Disconnect bypassed -- root login allowed]\r");
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136 | }
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137 | #else
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138 | static ALWAYS_INLINE void die_if_nologin_and_non_root(int amroot) {}
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139 | #endif
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140 |
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141 | #if ENABLE_FEATURE_SECURETTY && !ENABLE_PAM
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142 | static int check_securetty(void)
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143 | {
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144 | FILE *fp;
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145 | int i;
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146 | char buf[256];
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147 |
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148 | fp = fopen("/etc/securetty", "r");
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149 | if (!fp) {
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150 | /* A missing securetty file is not an error. */
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151 | return 1;
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152 | }
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153 | while (fgets(buf, sizeof(buf)-1, fp)) {
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154 | for (i = strlen(buf)-1; i >= 0; --i) {
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155 | if (!isspace(buf[i]))
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156 | break;
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157 | }
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158 | buf[++i] = '\0';
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159 | if (!buf[0] || (buf[0] == '#'))
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160 | continue;
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161 | if (strcmp(buf, short_tty) == 0) {
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162 | fclose(fp);
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163 | return 1;
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164 | }
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165 | }
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166 | fclose(fp);
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167 | return 0;
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168 | }
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169 | #else
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170 | static ALWAYS_INLINE int check_securetty(void) { return 1; }
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171 | #endif
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172 |
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173 | static void get_username_or_die(char *buf, int size_buf)
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174 | {
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175 | int c, cntdown;
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176 |
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177 | cntdown = EMPTY_USERNAME_COUNT;
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178 | prompt:
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179 | print_login_prompt();
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180 | /* skip whitespace */
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181 | do {
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182 | c = getchar();
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183 | if (c == EOF) exit(1);
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184 | if (c == '\n') {
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185 | if (!--cntdown) exit(1);
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186 | goto prompt;
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187 | }
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188 | } while (isspace(c));
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189 |
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190 | *buf++ = c;
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191 | if (!fgets(buf, size_buf-2, stdin))
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192 | exit(1);
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193 | if (!strchr(buf, '\n'))
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194 | exit(1);
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195 | while (isgraph(*buf)) buf++;
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196 | *buf = '\0';
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197 | }
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198 |
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199 | static void motd(void)
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200 | {
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201 | int fd;
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202 |
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203 | fd = open(bb_path_motd_file, O_RDONLY);
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204 | if (fd) {
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205 | fflush(stdout);
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206 | bb_copyfd_eof(fd, STDOUT_FILENO);
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207 | close(fd);
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208 | }
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209 | }
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210 |
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211 | static void alarm_handler(int sig ATTRIBUTE_UNUSED)
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212 | {
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213 | /* This is the escape hatch! Poor serial line users and the like
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214 | * arrive here when their connection is broken.
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215 | * We don't want to block here */
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216 | ndelay_on(1);
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217 | ndelay_on(2);
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218 | printf("\r\nLogin timed out after %d seconds\r\n", TIMEOUT);
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219 | exit(EXIT_SUCCESS);
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220 | }
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221 |
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222 | int login_main(int argc, char **argv);
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223 | int login_main(int argc, char **argv)
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224 | {
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225 | enum {
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226 | LOGIN_OPT_f = (1<<0),
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227 | LOGIN_OPT_h = (1<<1),
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228 | LOGIN_OPT_p = (1<<2),
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229 | };
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230 | char *fromhost;
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231 | char username[USERNAME_SIZE];
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232 | const char *tmp;
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233 | int amroot;
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234 | unsigned opt;
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235 | int count = 0;
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236 | struct passwd *pw;
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237 | char *opt_host = NULL;
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238 | char *opt_user = NULL;
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239 | char full_tty[TTYNAME_SIZE];
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240 | USE_SELINUX(security_context_t user_sid = NULL;)
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241 | USE_FEATURE_UTMP(struct utmp utent;)
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242 | USE_PAM(pam_handle_t *pamh;)
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243 | USE_PAM(int pamret;)
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244 | USE_PAM(const char *failed_msg;)
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245 |
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246 | short_tty = full_tty;
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247 | username[0] = '\0';
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248 | amroot = (getuid() == 0);
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249 | signal(SIGALRM, alarm_handler);
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250 | alarm(TIMEOUT);
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251 |
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252 | /* Mandatory paranoia for suid applet:
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253 | * ensure that fd# 0,1,2 are opened (at least to /dev/null)
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254 | * and any extra open fd's are closed.
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255 | * (The name of the function is misleading. Not daemonizing here.) */
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256 | bb_daemonize_or_rexec(DAEMON_ONLY_SANITIZE | DAEMON_CLOSE_EXTRA_FDS, NULL);
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257 |
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258 | opt = getopt32(argv, "f:h:p", &opt_user, &opt_host);
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259 | if (opt & LOGIN_OPT_f) {
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260 | if (!amroot)
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261 | bb_error_msg_and_die("-f is for root only");
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262 | safe_strncpy(username, opt_user, sizeof(username));
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263 | }
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264 | if (optind < argc) /* user from command line (getty) */
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265 | safe_strncpy(username, argv[optind], sizeof(username));
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266 |
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267 | /* Let's find out and memorize our tty */
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268 | if (!isatty(0) || !isatty(1) || !isatty(2))
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269 | return EXIT_FAILURE; /* Must be a terminal */
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270 | safe_strncpy(full_tty, "UNKNOWN", sizeof(full_tty));
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271 | tmp = ttyname(0);
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272 | if (tmp) {
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273 | safe_strncpy(full_tty, tmp, sizeof(full_tty));
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274 | if (strncmp(full_tty, "/dev/", 5) == 0)
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275 | short_tty = full_tty + 5;
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276 | }
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277 |
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278 | read_or_build_utent(&utent, !amroot);
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279 |
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280 | if (opt_host) {
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281 | USE_FEATURE_UTMP(
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282 | safe_strncpy(utent.ut_host, opt_host, sizeof(utent.ut_host));
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283 | )
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284 | fromhost = xasprintf(" on '%s' from '%s'", short_tty, opt_host);
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285 | } else
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286 | fromhost = xasprintf(" on '%s'", short_tty);
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287 |
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288 | /* Was breaking "login <username>" from shell command line: */
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289 | /*bb_setpgrp();*/
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290 |
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291 | openlog(applet_name, LOG_PID | LOG_CONS | LOG_NOWAIT, LOG_AUTH);
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292 |
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293 | while (1) {
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294 | if (!username[0])
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295 | get_username_or_die(username, sizeof(username));
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296 |
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297 | #if ENABLE_PAM
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298 | pamret = pam_start("login", username, &conv, &pamh);
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299 | if (pamret != PAM_SUCCESS) {
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300 | failed_msg = "pam_start";
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301 | goto pam_auth_failed;
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302 | }
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303 | /* set TTY (so things like securetty work) */
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304 | pamret = pam_set_item(pamh, PAM_TTY, short_tty);
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305 | if (pamret != PAM_SUCCESS) {
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306 | failed_msg = "pam_set_item(TTY)";
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307 | goto pam_auth_failed;
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308 | }
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309 | pamret = pam_authenticate(pamh, 0);
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310 | if (pamret != PAM_SUCCESS) {
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311 | failed_msg = "pam_authenticate";
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312 | goto pam_auth_failed;
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313 | /* TODO: or just "goto auth_failed"
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314 | * since user seems to enter wrong password
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315 | * (in this case pamret == 7)
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316 | */
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317 | }
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318 | /* check that the account is healthy */
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319 | pamret = pam_acct_mgmt(pamh, 0);
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320 | if (pamret != PAM_SUCCESS) {
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321 | failed_msg = "account setup";
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322 | goto pam_auth_failed;
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323 | }
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324 | /* read user back */
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325 | {
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326 | const char *pamuser;
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327 | /* gcc: "dereferencing type-punned pointer breaks aliasing rules..."
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328 | * thus we cast to (void*) */
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329 | if (pam_get_item(pamh, PAM_USER, (void*)&pamuser) != PAM_SUCCESS) {
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330 | failed_msg = "pam_get_item(USER)";
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331 | goto pam_auth_failed;
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332 | }
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333 | safe_strncpy(username, pamuser, sizeof(username));
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334 | }
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335 | /* If we get here, the user was authenticated, and is
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336 | * granted access. */
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337 | pw = getpwnam(username);
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338 | if (pw)
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339 | break;
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340 | goto auth_failed;
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341 | pam_auth_failed:
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342 | bb_error_msg("%s failed: %s (%d)", failed_msg, pam_strerror(pamh, pamret), pamret);
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343 | safe_strncpy(username, "UNKNOWN", sizeof(username));
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344 | #else /* not PAM */
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345 | pw = getpwnam(username);
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346 | if (!pw) {
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347 | strcpy(username, "UNKNOWN");
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348 | goto fake_it;
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349 | }
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350 |
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351 | if (pw->pw_passwd[0] == '!' || pw->pw_passwd[0] == '*')
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352 | goto auth_failed;
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353 |
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354 | if (opt & LOGIN_OPT_f)
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355 | break; /* -f USER: success without asking passwd */
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356 |
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357 | if (pw->pw_uid == 0 && !check_securetty())
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358 | goto auth_failed;
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359 |
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360 | /* Don't check the password if password entry is empty (!) */
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361 | if (!pw->pw_passwd[0])
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362 | break;
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363 | fake_it:
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364 | /* authorization takes place here */
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365 | if (correct_password(pw))
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366 | break;
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367 | #endif /* ENABLE_PAM */
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368 | auth_failed:
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369 | opt &= ~LOGIN_OPT_f;
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370 | bb_do_delay(FAIL_DELAY);
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371 | /* TODO: doesn't sound like correct English phrase to me */
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372 | puts("Login incorrect");
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373 | if (++count == 3) {
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374 | syslog(LOG_WARNING, "invalid password for '%s'%s",
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375 | username, fromhost);
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376 | return EXIT_FAILURE;
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377 | }
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378 | username[0] = '\0';
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379 | }
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380 |
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381 | alarm(0);
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382 | die_if_nologin_and_non_root(pw->pw_uid == 0);
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383 |
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384 | write_utent(&utent, username);
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385 |
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386 | #if ENABLE_SELINUX
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387 | if (is_selinux_enabled()) {
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388 | security_context_t old_tty_sid, new_tty_sid;
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389 |
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390 | if (get_default_context(username, NULL, &user_sid)) {
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391 | bb_error_msg_and_die("cannot get SID for %s",
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392 | username);
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393 | }
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394 | if (getfilecon(full_tty, &old_tty_sid) < 0) {
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395 | bb_perror_msg_and_die("getfilecon(%s) failed",
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396 | full_tty);
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397 | }
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398 | if (security_compute_relabel(user_sid, old_tty_sid,
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399 | SECCLASS_CHR_FILE, &new_tty_sid) != 0) {
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400 | bb_perror_msg_and_die("security_change_sid(%s) failed",
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401 | full_tty);
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402 | }
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403 | if (setfilecon(full_tty, new_tty_sid) != 0) {
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404 | bb_perror_msg_and_die("chsid(%s, %s) failed",
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405 | full_tty, new_tty_sid);
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406 | }
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407 | }
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408 | #endif
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409 | /* Try these, but don't complain if they fail.
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410 | * _f_chown is safe wrt race t=ttyname(0);...;chown(t); */
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411 | fchown(0, pw->pw_uid, pw->pw_gid);
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412 | fchmod(0, 0600);
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413 |
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414 | if (ENABLE_LOGIN_SCRIPTS) {
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415 | char *t_argv[2];
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416 |
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417 | t_argv[0] = getenv("LOGIN_PRE_SUID_SCRIPT");
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418 | if (t_argv[0]) {
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419 | t_argv[1] = NULL;
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420 | xsetenv("LOGIN_TTY", full_tty);
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421 | xsetenv("LOGIN_USER", pw->pw_name);
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422 | xsetenv("LOGIN_UID", utoa(pw->pw_uid));
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423 | xsetenv("LOGIN_GID", utoa(pw->pw_gid));
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424 | xsetenv("LOGIN_SHELL", pw->pw_shell);
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425 | xspawn(t_argv); /* NOMMU-friendly */
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426 | /* All variables are unset by setup_environment */
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427 | wait(NULL);
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428 | }
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429 | }
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430 |
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431 | change_identity(pw);
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432 | tmp = pw->pw_shell;
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433 | if (!tmp || !*tmp)
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434 | tmp = DEFAULT_SHELL;
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435 | /* setup_environment params: shell, loginshell, changeenv, pw */
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436 | setup_environment(tmp, 1, !(opt & LOGIN_OPT_p), pw);
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437 | /* FIXME: login shell = 1 -> 3rd parameter is ignored! */
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438 |
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439 | motd();
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440 |
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441 | if (pw->pw_uid == 0)
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442 | syslog(LOG_INFO, "root login%s", fromhost);
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443 | #if ENABLE_SELINUX
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444 | /* well, a simple setexeccon() here would do the job as well,
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445 | * but let's play the game for now */
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446 | set_current_security_context(user_sid);
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447 | #endif
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448 |
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449 | // util-linux login also does:
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450 | // /* start new session */
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451 | // setsid();
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452 | // /* TIOCSCTTY: steal tty from other process group */
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453 | // if (ioctl(0, TIOCSCTTY, 1)) error_msg...
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454 | // BBox login used to do this (see above):
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455 | // bb_setpgrp();
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456 | // If this stuff is really needed, add it and explain why!
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457 |
|
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458 | /* set signals to defaults */
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459 | signal(SIGALRM, SIG_DFL);
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460 | /* Is this correct? This way user can ctrl-c out of /etc/profile,
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461 | * potentially creating security breach (tested with bash 3.0).
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462 | * But without this, bash 3.0 will not enable ctrl-c either.
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463 | * Maybe bash is buggy?
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464 | * Need to find out what standards say about /bin/login -
|
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465 | * should it leave SIGINT etc enabled or disabled? */
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466 | signal(SIGINT, SIG_DFL);
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467 |
|
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468 | /* Exec login shell with no additional parameters */
|
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469 | run_shell(tmp, 1, NULL, NULL);
|
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470 |
|
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471 | /* return EXIT_FAILURE; - not reached */
|
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472 | }
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