wrapper.c

   1 #include <sys/stat.h>
   2 #include <sys/types.h>
   3 #include <sys/wait.h>
   4
   5 #include <err.h>
   6 #include <errno.h>
   7 #include <signal.h>
   8 #include <stdio.h>
   9 #include <stdlib.h>
  10 #include <string.h>
  11 #include <unistd.h>
  12
  13 #define LOCATE_HP(a, b) (((a) - (b)) / 2 + 1)
  14
  15 static size_t   host_is_valid(char *);
  16 static size_t   is_sh_clear(char *);
  17 static int      port_is_valid(char *);
  18 static void     usage(void);
  19
  20 int
  21 main(int argc, char **argv)
  22 {
  23         const unsigned int uargc = (unsigned int)argc;
  24         char *args[2] = {NULL, NULL}, *init = NULL;
  25         size_t n, o, s;
  26         int ch, rv;
  27         pid_t pids[2], sid;
  28
  29         if (uargc < 3) usage();
  30         while ((ch = getopt(argc, argv, "i:s:")) != -1)
  31                 switch (ch) {
  32                 case 'i':
  33                         if (is_sh_clear(optarg))
  34                                 errx(1, "sh(1) meta-characters and quotation"
  35                                     " marks are not allowed in `ii arg'.");
  36                         args[0] = optarg;
  37                         break;
  38                 case 's':
  39                         if (is_sh_clear(optarg))
  40                                 errx(1, "sh(1) meta-characters and quotation"
  41                                     " marks are not allowed in `sh arg'.");
  42                         args[1] = optarg;
  43                         break;
  44                 default:
  45                         usage();
  46                         /* NOTREACHED */
  47                 }
  48
  49         for (o = 1; o < uargc - 2; o++)
  50                 if (!strcmp(argv[o], "--"))
  51                         break;
  52         o++; /* argv[o] is now the first hostname, hopefully: */
  53         if ((uargc - o) & 1) usage();
  54
  55         for (n = o; n < uargc; n++) /* Validate the hosts and ports. */
  56                 if ((n - o) & 1) {
  57                         if ((rv = port_is_valid(argv[n])) < 0)
  58                                 errx(1, "Port number `%lu' is not in range.",
  59                                     (unsigned long)LOCATE_HP(n, o));
  60                         else if (rv > 0)
  61                                 errx(1, "Character `%lu' in port `%lu' is not"
  62                                     " allowed.", (unsigned long)rv,
  63                                     (unsigned long)LOCATE_HP(n, o));
  64                 } else
  65                         if ((rv = host_is_valid(argv[n])) != NULL)
  66                                 errx(1, "Character `%lu' in hostname `%lu' is"
  67                                     " not allowed.", (unsigned long)rv,
  68                                     (unsigned long)LOCATE_HP(n, o));
  69
  70         if (args[0]) printf("ii arg: `%s'.\n", args[0]);
  71         if (args[1]) printf("sh arg: `%s'.\n", args[1]);
  72         for (n = o; n < uargc - 1; n += 2)
  73                 printf("Server[%lu]: %s:%d\n", (unsigned long)LOCATE_HP(n, o),
  74                     argv[n], atoi(argv[n + 1]));
  75
  76         pids[0] = fork();
  77         if (pids[0] < 0)
  78                 exit(1);
  79         else if (pids[0] > 0)
  80                 exit(0);
  81
  82         umask(0);
  83
  84         sid = setsid();
  85         if (sid < 0)
  86                 _exit(1);
  87
  88         if ((chdir("/")) < 0)
  89                 _exit(1);
  90
  91         close(STDIN_FILENO);
  92         close(STDOUT_FILENO);
  93         close(STDERR_FILENO);
  94
  95         srandom(time(NULL));
  96
  97         for (;;) {
  98                 if (args[1] && pids[1] > 0) {
  99                         if (kill(pids[1], SIGKILL) && errno != ESRCH)
 100                                 _exit(1);
 101                         waitpid(0, NULL, 0);
 102                 }
 103
 104                 /* http://eternallyconfuzzled.com/arts/jsw_art_rand.aspx */
 105                 n = o + 1 + random() * 1.0 / ( RAND_MAX + 1.0 ) * (uargc - o - 1);
 106                 if ((n - o) & 1) n--;
 107                 s = strlen(args[0]) + strlen(argv[n]) + strlen(argv[n + 1]) + 10
 108                     + sizeof(EXECUTABLE);
 109
 110                 if ((init = calloc(s, 1)) == NULL)
 111                         _exit(1);
 112                 strlcpy(init, EXECUTABLE" ", s);
 113                 strlcat(init, args[0], s);
 114                 strlcat(init, " -s ", s);
 115                 strlcat(init, argv[n], s);
 116                 strlcat(init, " -p ", s);
 117                 strlcat(init, argv[n + 1], s);
 118
 119                 if (args[1]) {
 120                         pids[1] = fork();
 121                         if (pids[1] < 0) {
 122                                 _exit(1);
 123                         } else if (pids[1] > 0) {
 124                                 system(init);
 125                                 free(init);
 126                                 continue;
 127                         }
 128
 129                         sleep(SSLEEP);
 130                         system(args[1]);
 131                         _exit(0);
 132                 } else {
 133                         system(init);
 134                         free(init);
 135                 }
 136         }
 137 }
 138
 139 static size_t
 140 host_is_valid(char *h)
 141 {
 142         size_t n;
 143
 144         /*
 145          * Permitted characters in a hostname:
 146          *      a-z     (0x61 <= c <= 0x7a)
 147          *      0-9     (0x30 <= c <= 0x39)
 148          *      A-Z     (0x41 <= c <= 0x5a)
 149          *      .-
 150          */
 151         for (n = 0; n < strlen(h); n++)
 152                 if (((h[n] < 0x61 || h[n] > 0x7a) && (h[n] < 0x30 ||
 153                     h[n] > 0x39) && (h[n] < 0x41 || h[n] > 0x5a))
 154                     && h[n] != '.' && h[n] != '-')
 155                         return n + 1;
 156         return 0;
 157 }
 158
 159 static size_t
 160 is_sh_clear(char *s)
 161 {
 162         size_t n;
 163
 164         for (n = 0; n < strlen(s); n++)
 165                 if (s[n] == '<' || s[n] == '>' || s[n] == '|' || s[n] == ';' ||
 166                     s[n] == '(' || s[n] == ')' || s[n] == '&' || s[n] == '"' ||
 167                     s[n] == '\'')
 168                         if (n && s[n - 1] != '\\')
 169                                 return n + 1;
 170         return 0;
 171 }
 172
 173 static int
 174 port_is_valid(char *p)
 175 {
 176         size_t n;
 177
 178         if (atoi(p) < 1 || atoi(p) > 65535)
 179                 return -1;
 180
 181         for (n = 0; n < strlen(p); n++)
 182                 if (p[n] < 0x30 || p[n] > 0x39)
 183                         return n + 1;
 184         return 0;
 185 }
 186
 187 static void
 188 usage(void)
 189 {
 190         extern char *__progname;
 191
 192         (void)fprintf(stderr, "usage: %s [-i ii arg] [-s sh arg] \\\n\t --"
 193             " host1 port1 [host2 port2 ...]\n", __progname);
 194         exit(1);
 195 }