src/util/gen_pkcs3.c

   1 /* Copyright (C) 2012 Phil Pennock.
   2  * This is distributed as part of Exim and licensed under the GPL.
   3  * See the file "NOTICE" for more details.
   4  */
   5
   6 /* Build with:
   7  * c99 $(pkg-config --cflags openssl) gen_pkcs3.c $(pkg-config --libs openssl)
   8  */
   9
  10 #include <ctype.h>
  11 #include <errno.h>
  12 #include <stdbool.h>
  13 #include <stdio.h>
  14 #include <stdlib.h>
  15 #include <string.h>
  16 #include <unistd.h>
  17
  18 #include <openssl/bio.h>
  19 #include <openssl/bn.h>
  20 #include <openssl/dh.h>
  21 #include <openssl/err.h>
  22 #include <openssl/pem.h>
  23
  24 extern const char *__progname;
  25
  26
  27 void __attribute__((__noreturn__)) __attribute__((__format__(printf, 1, 2)))
  28 die(const char *fmt, ...)
  29 {
  30   va_list ap;
  31
  32   fflush(NULL);
  33   fprintf(stderr, "%s: ", __progname);
  34   va_start(ap, fmt);
  35   vfprintf(stderr, fmt, ap);
  36   va_end(ap);
  37   fprintf(stderr, "\n");
  38   fflush(stderr);
  39   exit(1);
  40 }
  41
  42
  43 void __attribute__((__noreturn__))
  44 die_openssl_err(const char *msg)
  45 {
  46   char err_string[250];
  47   unsigned long e;
  48
  49   ERR_error_string_n(ERR_get_error(), err_string, sizeof(err_string));
  50   die("%s: %s", msg, err_string);
  51 }
  52
  53
  54 static BIGNUM *
  55 bn_from_text(const char *text)
  56 {
  57   BIGNUM *b;
  58   char *p, *spaceless;
  59   const char *q, *end;
  60   size_t len;
  61   int rc;
  62
  63   len = strlen(text);
  64   spaceless = malloc(len);
  65   if (!spaceless)
  66     die("malloc(%zu) failed: %s", len, strerror(errno));
  67
  68   for (p = spaceless, q = text, end = text + len;
  69        q < end;
  70        ++q) {
  71     if (!isspace(*q))
  72       *p++ = *q;
  73   }
  74
  75   b = NULL;
  76   rc = BN_hex2bn(&b, spaceless);
  77
  78   if (rc != p - spaceless)
  79     die("BN_hex2bn did not convert entire input; took %d of %z bytes",
  80         rc, p - spaceless);
  81
  82   return b;
  83 }
  84
  85
  86 static void
  87 our_dh_check(DH *dh)
  88 {
  89   int rc, errflags = 0;
  90
  91   rc = DH_check(dh, &errflags);
  92   if (!rc) die_openssl_err("DH_check() could not be performed");;
  93
  94   /* We ignore DH_UNABLE_TO_CHECK_GENERATOR because some of the invocations
  95    * deliberately provide generators other than 2 or 5. */
  96
  97   if (errflags & DH_CHECK_P_NOT_SAFE_PRIME)
  98     die("DH_check(): p not a safe prime");
  99   if (errflags & DH_NOT_SUITABLE_GENERATOR)
 100     die("DH_check(): g not suitable as generator");
 101 }
 102
 103
 104 static void
 105 emit_c_format_dh(FILE *stream, DH *dh)
 106 {
 107   BIO *bio;
 108   long length;
 109   char *data, *end, *p, *nl;
 110
 111   bio = BIO_new(BIO_s_mem());
 112   PEM_write_bio_DHparams(bio, dh);
 113   length = BIO_get_mem_data(bio, &data);
 114   if (!length)
 115     die("no data in memory BIO to format for printing");
 116   if (length < 0)
 117     die("grr, negative length memory not supported");
 118   end = data + length;
 119
 120   for (p = data; p < end; /**/) {
 121     nl = strchr(p, '\n');
 122     if (!nl) {
 123       fprintf(stream, "\"%s\\n\"\n/* missing final newline */\n", p);
 124       break;
 125     }
 126     *nl = '\0';
 127     fprintf(stream, "\"%s\\n\"\n", p);
 128     p = nl + 1;
 129   }
 130 }
 131
 132
 133 void __attribute__((__noreturn__))
 134 usage(FILE *stream, int exitcode)
 135 {
 136   fprintf(stream, "Usage: %s [-CPcst] <dh_p> <dh_g>\n"
 137 "Both dh_p and dh_g should be hex strings representing the numbers\n"
 138 "They may contain whitespace.\n"
 139 "\n"
 140 " -C      show C string form of PEM result\n"
 141 " -P      do not show PEM\n"
 142 " -c      run OpenSSL DH_check() on the DH object\n"
 143 " -s      show the parsed p and g\n"
 144 " -t      show text form of certificate\n"
 145
 146       , __progname);
 147   exit(exitcode);
 148 }
 149
 150
 151 int
 152 main(int argc, char *argv[])
 153 {
 154   BIGNUM *p, *g;
 155   DH *dh;
 156   int ch;
 157   bool perform_dh_check = false;
 158   bool show_c_form = false;
 159   bool show_numbers = false;
 160   bool show_pem = true;
 161   bool show_text = false;
 162
 163   while ((ch = getopt(argc, argv, "CPcsth")) != -1) {
 164     switch (ch) {
 165       case 'C':
 166         show_c_form = true;
 167         break;
 168       case 'P':
 169         show_pem = false;
 170         break;
 171       case 'c':
 172         perform_dh_check = true;
 173         break;
 174       case 's':
 175         show_numbers = true;
 176         break;
 177       case 't':
 178         show_text = true;
 179         break;
 180
 181       case 'h':
 182         usage(stdout, 0);
 183       case '?':
 184         die("Unknown option or missing argument -%c", optopt);
 185       default:
 186         die("Unhandled option -%c", ch);
 187     }
 188   }
 189
 190   optind -= 1;
 191   argc -= optind;
 192   argv += optind;
 193
 194   if (argc != 3) {
 195     fprintf(stderr, "argc: %d\n", argc);
 196     usage(stderr, 1);
 197   }
 198
 199   p = bn_from_text(argv[1]);
 200   g = bn_from_text(argv[2]);
 201
 202   if (show_numbers) {
 203     printf("p = ");
 204     BN_print_fp(stdout, p);
 205     printf("\ng = ");
 206     BN_print_fp(stdout, g);
 207     printf("\n");
 208   }
 209
 210   dh = DH_new();
 211   dh->p = p;
 212   dh->g = g;
 213
 214   if (perform_dh_check)
 215     our_dh_check(dh);
 216
 217   if (show_text)
 218     DHparams_print_fp(stdout, dh);
 219
 220   if (show_pem) {
 221     if (show_c_form)
 222       emit_c_format_dh(stdout, dh);
 223     else
 224       PEM_write_DHparams(stdout, dh);
 225   }
 226
 227   DH_free(dh); /* should free p & g too */
 228   return 0;
 229 }