wrapper.c

   1 /*
   2  * The author of this work has dedicated it to the public by waiving all of his
   3  * or her rights to the work under copyright law and all related or neighboring
   4  * legal rights he or she had in the work, to the extent allowable by law.
   5  */
   6 #include <sys/stat.h>
   7 #include <sys/types.h>
   8 #include <sys/wait.h>
   9
  10 #include <err.h>
  11 #include <errno.h>
  12 #include <signal.h>
  13 #include <stdio.h>
  14 #include <stdlib.h>
  15 #include <string.h>
  16 #include <unistd.h>
  17
  18 #define LOCATE_HP(a, b) (((a) - (b)) / 2 + 1)
  19
  20 static size_t   host_is_valid(char *);
  21 static size_t   is_sh_clear(char *);
  22 static int      port_is_valid(char *);
  23 static void     usage(void);
  24
  25 int
  26 main(int argc, char **argv)
  27 {
  28         const unsigned int uargc = (unsigned int)argc;
  29         char *args[2] = {NULL, NULL}, *init = NULL;
  30         size_t n, o, s;
  31         int ch, rv;
  32         pid_t pids[2], sid;
  33
  34         if (uargc < 3) usage();
  35         while ((ch = getopt(argc, argv, "i:s:")) != -1)
  36                 switch (ch) {
  37                 case 'i':
  38                         if (is_sh_clear(optarg))
  39                                 errx(1, "sh(1) meta-characters and quotation"
  40                                     " marks are not allowed in `ii arg'.");
  41                         args[0] = optarg;
  42                         break;
  43                 case 's':
  44                         if (is_sh_clear(optarg))
  45                                 errx(1, "sh(1) meta-characters and quotation"
  46                                     " marks are not allowed in `sh arg'.");
  47                         args[1] = optarg;
  48                         break;
  49                 default:
  50                         usage();
  51                         /* NOTREACHED */
  52                 }
  53
  54         for (o = 1; o < uargc - 2; o++)
  55                 if (!strcmp(argv[o], "--"))
  56                         break;
  57         o++; /* argv[o] is now the first hostname, hopefully: */
  58         if ((uargc - o) & 1) usage();
  59
  60         for (n = o; n < uargc; n++) /* Validate the hosts and ports. */
  61                 if ((n - o) & 1) {
  62                         if ((rv = port_is_valid(argv[n])) < 0)
  63                                 errx(1, "Port number `%lu' is not in range.",
  64                                     (unsigned long)LOCATE_HP(n, o));
  65                         else if (rv > 0)
  66                                 errx(1, "Character `%lu' in port `%lu' is not"
  67                                     " allowed.", (unsigned long)rv,
  68                                     (unsigned long)LOCATE_HP(n, o));
  69                 } else
  70                         if ((rv = host_is_valid(argv[n])) != NULL)
  71                                 errx(1, "Character `%lu' in hostname `%lu' is"
  72                                     " not allowed.", (unsigned long)rv,
  73                                     (unsigned long)LOCATE_HP(n, o));
  74
  75         if (args[0]) printf("ii arg: `%s'.\n", args[0]);
  76         if (args[1]) printf("sh arg: `%s'.\n", args[1]);
  77         for (n = o; n < uargc - 1; n += 2)
  78                 printf("Server[%lu]: %s:%d\n", (unsigned long)LOCATE_HP(n, o),
  79                     argv[n], atoi(argv[n + 1]));
  80
  81         pids[0] = fork();
  82         if (pids[0] < 0)
  83                 exit(1);
  84         else if (pids[0] > 0)
  85                 exit(0);
  86
  87         umask(0);
  88
  89         sid = setsid();
  90         if (sid < 0)
  91                 _exit(1);
  92
  93         if ((chdir("/")) < 0)
  94                 _exit(1);
  95
  96         close(STDIN_FILENO);
  97         close(STDOUT_FILENO);
  98         close(STDERR_FILENO);
  99
 100         srandom(time(NULL));
 101
 102         for (;;) {
 103                 if (args[1] && pids[1] > 0) {
 104                         if (kill(pids[1], SIGKILL) && errno != ESRCH)
 105                                 _exit(1);
 106                         waitpid(0, NULL, 0);
 107                 }
 108
 109                 sleep(LOOP_SLEEP);
 110
 111                 /* http://eternallyconfuzzled.com/arts/jsw_art_rand.aspx */
 112                 n = o + 1 + random() * 1.0 / ( RAND_MAX + 1.0 ) * (uargc - o - 1);
 113                 if ((n - o) & 1) n--;
 114                 s = strlen(args[0]) + strlen(argv[n]) + strlen(argv[n + 1]) + 10
 115                     + sizeof(II_EXEC);
 116
 117                 if ((init = calloc(s, 1)) == NULL)
 118                         _exit(1);
 119                 strlcpy(init, II_EXEC" ", s);
 120                 strlcat(init, args[0], s);
 121                 strlcat(init, " -s ", s);
 122                 strlcat(init, argv[n], s);
 123                 strlcat(init, " -p ", s);
 124                 strlcat(init, argv[n + 1], s);
 125
 126                 if (args[1]) {
 127                         pids[1] = fork();
 128                         if (pids[1] < 0) {
 129                                 _exit(1);
 130                         } else if (pids[1] > 0) {
 131                                 system(init);
 132                                 free(init);
 133                                 continue;
 134                         }
 135
 136                         sleep(CHLD_SLEEP);
 137                         system(args[1]);
 138                         _exit(0);
 139                 } else {
 140                         system(init);
 141                         free(init);
 142                 }
 143         }
 144 }
 145
 146 static size_t
 147 host_is_valid(char *h)
 148 {
 149         size_t n;
 150
 151         /*
 152          * Permitted characters in a hostname:
 153          *      a-z     (0x61 <= c <= 0x7a)
 154          *      0-9     (0x30 <= c <= 0x39)
 155          *      A-Z     (0x41 <= c <= 0x5a)
 156          *      .-
 157          */
 158         for (n = 0; n < strlen(h); n++)
 159                 if (((h[n] < 0x61 || h[n] > 0x7a) && (h[n] < 0x30 ||
 160                     h[n] > 0x39) && (h[n] < 0x41 || h[n] > 0x5a))
 161                     && h[n] != '.' && h[n] != '-')
 162                         return n + 1;
 163         return 0;
 164 }
 165
 166 static size_t
 167 is_sh_clear(char *s)
 168 {
 169         size_t n;
 170
 171         for (n = 0; n < strlen(s); n++)
 172                 if (s[n] == '<' || s[n] == '>' || s[n] == '|' || s[n] == ';' ||
 173                     s[n] == '(' || s[n] == ')' || s[n] == '&' || s[n] == '"' ||
 174                     s[n] == '\'')
 175                         if (n && s[n - 1] != '\\')
 176                                 return n + 1;
 177         return 0;
 178 }
 179
 180 static int
 181 port_is_valid(char *p)
 182 {
 183         size_t n;
 184
 185         if (atoi(p) < 1 || atoi(p) > 65535)
 186                 return -1;
 187
 188         for (n = 0; n < strlen(p); n++)
 189                 if (p[n] < 0x30 || p[n] > 0x39)
 190                         return n + 1;
 191         return 0;
 192 }
 193
 194 static void
 195 usage(void)
 196 {
 197         extern char *__progname;
 198
 199         (void)fprintf(stderr, "usage: %s [-i ii arg] [-s sh arg] \\\n\t --"
 200             " host1 port1 [host2 port2 ...]\n", __progname);
 201         exit(1);
 202 }