cotp.c

   1 /** Practical One-time Pad Library
   2  *
   3  * Created:20080514
   4  * By Jeff Connelly
   5  */
   6
   7 #include <stdio.h>
   8 #include <stdlib.h>
   9 #include <string.h>
  10 #include <getopt.h>
  11 #include <sysexits.h>
  12
  13 #include "libotp.h"
  14
  15 extern PAD *pads;
  16
  17 extern char *optarg;
  18 extern int optind;
  19
  20 void test()
  21 {
  22     char *o;
  23     unsigned int i;
  24
  25     load_config("otp.conf");
  26     show_pads();
  27
  28     /*
  29     printf("offset=%ld\n", read_offset(pads));
  30     write_offset(pads, 1213475);
  31     printf("offset=%ld\n", read_offset(pads));
  32     */
  33
  34     otp_decrypt("--EMOTP_BEGIN--1213434,\n"
  35             "gK1O22FPbxLmxrROfFHDCsM1LTsOAjjbRlHVM1p+WG+s6yslYVfzvtc=\n"
  36             "--EMOTP_END--\n", &o);
  37     puts(o);
  38     free(o);
  39
  40     otp_decrypt("--EMOTP_BEGIN--978,dc,\n"
  41             "hUZm1q0gX7pa6Alzbo9OZiT8wA==\n"
  42             "--EMOTP_END--\n", &o);
  43     puts(o);
  44     free(o);
  45
  46     o = otp_encrypt("hello world", strlen("hello world"), "dc", &i);
  47     printf("encrypt = %s\n", o);
  48     free(o);
  49
  50     otp_decrypt("junkasdsjdfldjf jdsfjunk--EMOTP_BEGIN--1213475,dc,\n"
  51             "v7jlXbCCvPv4S0k=\n"
  52             "--EMOTP_END--\n-tasjdktrailingjunkksjdjf", &o);
  53     puts(o);
  54     free(o);
  55
  56     free_pads();
  57 }
  58
  59 /* Operation mode */
  60 #define ENCRYPT -1
  61 #define AUTO     0
  62 #define DECRYPT 1
  63 #define REPLACE 2
  64
  65 void usage()
  66 {
  67     fprintf(stderr, "usage: otp [-e | -d | ] [-t <pad_name>]\n"
  68             "\n"
  69             "Mode selection:\n"
  70             "-e     Encrypt\n"
  71             "-d     Decrypt\n"
  72             "-r     Replace what an existing encrypted message decrypts to\n"
  73             "Default is automatic.\n"
  74             "\n"
  75             "-t     Specify pad name to encrypt with. Default: first pad.\n");
  76     exit(EX_USAGE);
  77 }
  78
  79 /* Read input data.
  80  *
  81  * @param size Set to number of bytes read.
  82  *
  83  * @return Input, caller frees.
  84  */
  85 char *read_input(unsigned int *size)
  86 {
  87     unsigned int i, buffer_size;
  88     char *input;
  89
  90     i = 0;
  91     buffer_size = 1024;
  92     input = malloc(buffer_size);
  93     if (!input) {
  94         perror("malloc input buffer");
  95         exit(EX_UNAVAILABLE);
  96     }
  97
  98     while(!feof(stdin)) {
  99         input[i++] = fgetc(stdin);
 100         if (input[i - 1] == EOF)
 101             break;
 102         if (i >= buffer_size) {
 103             buffer_size += 1024;
 104             input = realloc(input, buffer_size);
 105             if (!input) {
 106                 perror("realloc input buffer");
 107                 exit(EX_UNAVAILABLE);
 108             }
 109         }
 110     }
 111     input[i - 1] = 0;
 112     *size = i - 1;
 113
 114     return input;
 115 }
 116
 117 int main(int argc, char **argv)
 118 {
 119     int ch, mode, i;
 120     unsigned int length, output_length;
 121     char *to, *input, *output;
 122
 123     mode = AUTO;
 124     to = NULL;
 125
 126     while((ch = getopt(argc, argv, "erdt:")) != -1) {
 127         switch(ch)
 128         {
 129         case 'e':
 130             mode = ENCRYPT;
 131             break;
 132         case 'd':
 133             mode = DECRYPT;
 134             break;
 135         case 't':
 136             to = optarg;
 137             break;
 138         case 'r':
 139             mode = REPLACE;
 140             break;
 141         case '?':
 142         default:
 143             usage();
 144         }
 145     }
 146     argc -= optind;
 147     argv += optind;
 148
 149     /* Automatic mode - guess based on magic markers.
 150      * Explicit modes still allowed so can encrypt data with
 151      * magic markers in it (if you ever want to). */
 152     if (mode == AUTO) {
 153         if (strstr(input, MARKER_BEGIN))
 154             mode = DECRYPT;
 155         else
 156             mode = ENCRYPT;
 157     }
 158
 159     load_config("otp.conf");
 160
 161     input = read_input(&length);
 162
 163     if (mode == ENCRYPT) {
 164         output = otp_encrypt(input, length, to, &output_length);
 165     } else if (mode == DECRYPT) {
 166         output_length = otp_decrypt(input, &output);
 167     } else if (mode == REPLACE) {
 168         if (!strstr(input, MARKER_END)) {
 169             fprintf(stderr, "need encrypted pad, trailed by new message\n");
 170             exit(EXIT_FAILURE);
 171         }
 172
 173         otp_replace(input, strstr(input, MARKER_END) + strlen(MARKER_END) + 1);
 174         output_length = 0;
 175     }
 176
 177     for (i = 0; i < output_length; ++i)
 178         putchar(output[i]);
 179
 180     free(output);
 181     free_pads();
 182
 183     return 0;
 184 }
 185