| 1 | /* |
| 2 | * RSA implementation just sufficient for ssh client-side |
| 3 | * initialisation step |
| 4 | */ |
| 5 | |
| 6 | /*#include <windows.h> |
| 7 | #define RSADEBUG |
| 8 | #define DLVL 2 |
| 9 | #include "stel.h"*/ |
| 10 | |
| 11 | #include <stdio.h> |
| 12 | #include <stdlib.h> |
| 13 | #include <string.h> |
| 14 | |
| 15 | #include "ssh.h" |
| 16 | |
| 17 | typedef unsigned short *Bignum; |
| 18 | |
| 19 | static unsigned short Zero[1] = { 0 }; |
| 20 | |
| 21 | #if defined TESTMODE || defined RSADEBUG |
| 22 | #ifndef DLVL |
| 23 | #define DLVL 10000 |
| 24 | #endif |
| 25 | #define debug(x) bndebug(#x,x) |
| 26 | static int level = 0; |
| 27 | static void bndebug(char *name, Bignum b) { |
| 28 | int i; |
| 29 | int w = 50-level-strlen(name)-5*b[0]; |
| 30 | if (level >= DLVL) |
| 31 | return; |
| 32 | if (w < 0) w = 0; |
| 33 | dprintf("%*s%s%*s", level, "", name, w, ""); |
| 34 | for (i=b[0]; i>0; i--) |
| 35 | dprintf(" %04x", b[i]); |
| 36 | dprintf("\n"); |
| 37 | } |
| 38 | #define dmsg(x) do {if(level<DLVL){dprintf("%*s",level,"");printf x;}} while(0) |
| 39 | #define enter(x) do { dmsg(x); level += 4; } while(0) |
| 40 | #define leave(x) do { level -= 4; dmsg(x); } while(0) |
| 41 | #else |
| 42 | #define debug(x) |
| 43 | #define dmsg(x) |
| 44 | #define enter(x) |
| 45 | #define leave(x) |
| 46 | #endif |
| 47 | |
| 48 | static Bignum newbn(int length) { |
| 49 | Bignum b = malloc((length+1)*sizeof(unsigned short)); |
| 50 | if (!b) |
| 51 | abort(); /* FIXME */ |
| 52 | b[0] = length; |
| 53 | return b; |
| 54 | } |
| 55 | |
| 56 | static void freebn(Bignum b) { |
| 57 | free(b); |
| 58 | } |
| 59 | |
| 60 | static int msb(Bignum r) { |
| 61 | int i; |
| 62 | int j; |
| 63 | unsigned short n; |
| 64 | |
| 65 | for (i=r[0]; i>0; i--) |
| 66 | if (r[i]) |
| 67 | break; |
| 68 | |
| 69 | j = (i-1)*16; |
| 70 | n = r[i]; |
| 71 | if (n & 0xFF00) j += 8, n >>= 8; |
| 72 | if (n & 0x00F0) j += 4, n >>= 4; |
| 73 | if (n & 0x000C) j += 2, n >>= 2; |
| 74 | if (n & 0x0002) j += 1, n >>= 1; |
| 75 | |
| 76 | return j; |
| 77 | } |
| 78 | |
| 79 | static void add(Bignum r1, Bignum r2, Bignum result) { |
| 80 | int i; |
| 81 | long stuff = 0; |
| 82 | |
| 83 | enter((">add\n")); |
| 84 | debug(r1); |
| 85 | debug(r2); |
| 86 | |
| 87 | for (i = 1 ;; i++) { |
| 88 | if (i <= r1[0]) |
| 89 | stuff += r1[i]; |
| 90 | if (i <= r2[0]) |
| 91 | stuff += r2[i]; |
| 92 | if (i <= result[0]) |
| 93 | result[i] = stuff & 0xFFFFU; |
| 94 | if (i > r1[0] && i > r2[0] && i >= result[0]) |
| 95 | break; |
| 96 | stuff >>= 16; |
| 97 | } |
| 98 | |
| 99 | debug(result); |
| 100 | leave(("<add\n")); |
| 101 | } |
| 102 | |
| 103 | static void sub(Bignum r1, Bignum r2, Bignum result) { |
| 104 | int i; |
| 105 | long stuff = 0; |
| 106 | |
| 107 | enter((">sub\n")); |
| 108 | debug(r1); |
| 109 | debug(r2); |
| 110 | |
| 111 | for (i = 1 ;; i++) { |
| 112 | if (i <= r1[0]) |
| 113 | stuff += r1[i]; |
| 114 | if (i <= r2[0]) |
| 115 | stuff -= r2[i]; |
| 116 | if (i <= result[0]) |
| 117 | result[i] = stuff & 0xFFFFU; |
| 118 | if (i > r1[0] && i > r2[0] && i >= result[0]) |
| 119 | break; |
| 120 | stuff = stuff<0 ? -1 : 0; |
| 121 | } |
| 122 | |
| 123 | debug(result); |
| 124 | leave(("<sub\n")); |
| 125 | } |
| 126 | |
| 127 | static int ge(Bignum r1, Bignum r2) { |
| 128 | int i; |
| 129 | |
| 130 | enter((">ge\n")); |
| 131 | debug(r1); |
| 132 | debug(r2); |
| 133 | |
| 134 | if (r1[0] < r2[0]) |
| 135 | i = r2[0]; |
| 136 | else |
| 137 | i = r1[0]; |
| 138 | |
| 139 | while (i > 0) { |
| 140 | unsigned short n1 = (i > r1[0] ? 0 : r1[i]); |
| 141 | unsigned short n2 = (i > r2[0] ? 0 : r2[i]); |
| 142 | |
| 143 | if (n1 > n2) { |
| 144 | dmsg(("greater\n")); |
| 145 | leave(("<ge\n")); |
| 146 | return 1; /* r1 > r2 */ |
| 147 | } else if (n1 < n2) { |
| 148 | dmsg(("less\n")); |
| 149 | leave(("<ge\n")); |
| 150 | return 0; /* r1 < r2 */ |
| 151 | } |
| 152 | |
| 153 | i--; |
| 154 | } |
| 155 | |
| 156 | dmsg(("equal\n")); |
| 157 | leave(("<ge\n")); |
| 158 | return 1; /* r1 = r2 */ |
| 159 | } |
| 160 | |
| 161 | static void modmult(Bignum r1, Bignum r2, Bignum modulus, Bignum result) { |
| 162 | Bignum temp = newbn(modulus[0]+1); |
| 163 | Bignum tmp2 = newbn(modulus[0]+1); |
| 164 | int i; |
| 165 | int bit, bits, digit, smallbit; |
| 166 | |
| 167 | enter((">modmult\n")); |
| 168 | debug(r1); |
| 169 | debug(r2); |
| 170 | debug(modulus); |
| 171 | |
| 172 | for (i=1; i<=result[0]; i++) |
| 173 | result[i] = 0; /* result := 0 */ |
| 174 | for (i=1; i<=temp[0]; i++) |
| 175 | temp[i] = (i > r2[0] ? 0 : r2[i]); /* temp := r2 */ |
| 176 | |
| 177 | bits = 1+msb(r1); |
| 178 | |
| 179 | for (bit = 0; bit < bits; bit++) { |
| 180 | digit = 1 + bit / 16; |
| 181 | smallbit = bit % 16; |
| 182 | |
| 183 | debug(temp); |
| 184 | if (digit <= r1[0] && (r1[digit] & (1<<smallbit))) { |
| 185 | dmsg(("bit %d\n", bit)); |
| 186 | add(temp, result, tmp2); |
| 187 | if (ge(tmp2, modulus)) |
| 188 | sub(tmp2, modulus, result); |
| 189 | else |
| 190 | add(tmp2, Zero, result); |
| 191 | debug(result); |
| 192 | } |
| 193 | |
| 194 | add(temp, temp, tmp2); |
| 195 | if (ge(tmp2, modulus)) |
| 196 | sub(tmp2, modulus, temp); |
| 197 | else |
| 198 | add(tmp2, Zero, temp); |
| 199 | } |
| 200 | |
| 201 | freebn(temp); |
| 202 | freebn(tmp2); |
| 203 | |
| 204 | debug(result); |
| 205 | leave(("<modmult\n")); |
| 206 | } |
| 207 | |
| 208 | static void modpow(Bignum r1, Bignum r2, Bignum modulus, Bignum result) { |
| 209 | Bignum temp = newbn(modulus[0]+1); |
| 210 | Bignum tmp2 = newbn(modulus[0]+1); |
| 211 | int i; |
| 212 | int bit, bits, digit, smallbit; |
| 213 | |
| 214 | enter((">modpow\n")); |
| 215 | debug(r1); |
| 216 | debug(r2); |
| 217 | debug(modulus); |
| 218 | |
| 219 | for (i=1; i<=result[0]; i++) |
| 220 | result[i] = (i==1); /* result := 1 */ |
| 221 | for (i=1; i<=temp[0]; i++) |
| 222 | temp[i] = (i > r1[0] ? 0 : r1[i]); /* temp := r1 */ |
| 223 | |
| 224 | bits = 1+msb(r2); |
| 225 | |
| 226 | for (bit = 0; bit < bits; bit++) { |
| 227 | digit = 1 + bit / 16; |
| 228 | smallbit = bit % 16; |
| 229 | |
| 230 | debug(temp); |
| 231 | if (digit <= r2[0] && (r2[digit] & (1<<smallbit))) { |
| 232 | dmsg(("bit %d\n", bit)); |
| 233 | modmult(temp, result, modulus, tmp2); |
| 234 | add(tmp2, Zero, result); |
| 235 | debug(result); |
| 236 | } |
| 237 | |
| 238 | modmult(temp, temp, modulus, tmp2); |
| 239 | add(tmp2, Zero, temp); |
| 240 | } |
| 241 | |
| 242 | freebn(temp); |
| 243 | freebn(tmp2); |
| 244 | |
| 245 | debug(result); |
| 246 | leave(("<modpow\n")); |
| 247 | } |
| 248 | |
| 249 | int makekey(unsigned char *data, struct RSAKey *result, |
| 250 | unsigned char **keystr) { |
| 251 | unsigned char *p = data; |
| 252 | Bignum bn[2]; |
| 253 | int i, j; |
| 254 | int w, b; |
| 255 | |
| 256 | result->bits = 0; |
| 257 | for (i=0; i<4; i++) |
| 258 | result->bits = (result->bits << 8) + *p++; |
| 259 | |
| 260 | for (j=0; j<2; j++) { |
| 261 | |
| 262 | w = 0; |
| 263 | for (i=0; i<2; i++) |
| 264 | w = (w << 8) + *p++; |
| 265 | |
| 266 | result->bytes = b = (w+7)/8; /* bits -> bytes */ |
| 267 | w = (w+15)/16; /* bits -> words */ |
| 268 | |
| 269 | bn[j] = newbn(w); |
| 270 | |
| 271 | if (keystr) *keystr = p; /* point at key string, second time */ |
| 272 | |
| 273 | for (i=1; i<=w; i++) |
| 274 | bn[j][i] = 0; |
| 275 | for (i=0; i<b; i++) { |
| 276 | unsigned char byte = *p++; |
| 277 | if ((b-i) & 1) |
| 278 | bn[j][w-i/2] |= byte; |
| 279 | else |
| 280 | bn[j][w-i/2] |= byte<<8; |
| 281 | } |
| 282 | |
| 283 | debug(bn[j]); |
| 284 | |
| 285 | } |
| 286 | |
| 287 | result->exponent = bn[0]; |
| 288 | result->modulus = bn[1]; |
| 289 | |
| 290 | return p - data; |
| 291 | } |
| 292 | |
| 293 | void rsaencrypt(unsigned char *data, int length, struct RSAKey *key) { |
| 294 | Bignum b1, b2; |
| 295 | int w, i; |
| 296 | unsigned char *p; |
| 297 | |
| 298 | debug(key->exponent); |
| 299 | |
| 300 | memmove(data+key->bytes-length, data, length); |
| 301 | data[0] = 0; |
| 302 | data[1] = 2; |
| 303 | |
| 304 | for (i = 2; i < key->bytes-length-1; i++) { |
| 305 | do { |
| 306 | data[i] = random_byte(); |
| 307 | } while (data[i] == 0); |
| 308 | } |
| 309 | data[key->bytes-length-1] = 0; |
| 310 | |
| 311 | w = (key->bytes+1)/2; |
| 312 | |
| 313 | b1 = newbn(w); |
| 314 | b2 = newbn(w); |
| 315 | |
| 316 | p = data; |
| 317 | for (i=1; i<=w; i++) |
| 318 | b1[i] = 0; |
| 319 | for (i=0; i<key->bytes; i++) { |
| 320 | unsigned char byte = *p++; |
| 321 | if ((key->bytes-i) & 1) |
| 322 | b1[w-i/2] |= byte; |
| 323 | else |
| 324 | b1[w-i/2] |= byte<<8; |
| 325 | } |
| 326 | |
| 327 | debug(b1); |
| 328 | |
| 329 | modpow(b1, key->exponent, key->modulus, b2); |
| 330 | |
| 331 | debug(b2); |
| 332 | |
| 333 | p = data; |
| 334 | for (i=0; i<key->bytes; i++) { |
| 335 | unsigned char b; |
| 336 | if (i & 1) |
| 337 | b = b2[w-i/2] & 0xFF; |
| 338 | else |
| 339 | b = b2[w-i/2] >> 8; |
| 340 | *p++ = b; |
| 341 | } |
| 342 | |
| 343 | freebn(b1); |
| 344 | freebn(b2); |
| 345 | } |
| 346 | |
| 347 | int rsastr_len(struct RSAKey *key) { |
| 348 | Bignum md, ex; |
| 349 | |
| 350 | md = key->modulus; |
| 351 | ex = key->exponent; |
| 352 | return 4 * (ex[0]+md[0]) + 10; |
| 353 | } |
| 354 | |
| 355 | void rsastr_fmt(char *str, struct RSAKey *key) { |
| 356 | Bignum md, ex; |
| 357 | int len = 0, i; |
| 358 | |
| 359 | md = key->modulus; |
| 360 | ex = key->exponent; |
| 361 | |
| 362 | for (i=1; i<=ex[0]; i++) { |
| 363 | sprintf(str+len, "%04x", ex[i]); |
| 364 | len += strlen(str+len); |
| 365 | } |
| 366 | str[len++] = '/'; |
| 367 | for (i=1; i<=md[0]; i++) { |
| 368 | sprintf(str+len, "%04x", md[i]); |
| 369 | len += strlen(str+len); |
| 370 | } |
| 371 | str[len] = '\0'; |
| 372 | } |
| 373 | |
| 374 | #ifdef TESTMODE |
| 375 | |
| 376 | #ifndef NODDY |
| 377 | #define p1 10007 |
| 378 | #define p2 10069 |
| 379 | #define p3 10177 |
| 380 | #else |
| 381 | #define p1 3 |
| 382 | #define p2 7 |
| 383 | #define p3 13 |
| 384 | #endif |
| 385 | |
| 386 | unsigned short P1[2] = { 1, p1 }; |
| 387 | unsigned short P2[2] = { 1, p2 }; |
| 388 | unsigned short P3[2] = { 1, p3 }; |
| 389 | unsigned short bigmod[5] = { 4, 0, 0, 0, 32768U }; |
| 390 | unsigned short mod[5] = { 4, 0, 0, 0, 0 }; |
| 391 | unsigned short a[5] = { 4, 0, 0, 0, 0 }; |
| 392 | unsigned short b[5] = { 4, 0, 0, 0, 0 }; |
| 393 | unsigned short c[5] = { 4, 0, 0, 0, 0 }; |
| 394 | unsigned short One[2] = { 1, 1 }; |
| 395 | unsigned short Two[2] = { 1, 2 }; |
| 396 | |
| 397 | int main(void) { |
| 398 | modmult(P1, P2, bigmod, a); debug(a); |
| 399 | modmult(a, P3, bigmod, mod); debug(mod); |
| 400 | |
| 401 | sub(P1, One, a); debug(a); |
| 402 | sub(P2, One, b); debug(b); |
| 403 | modmult(a, b, bigmod, c); debug(c); |
| 404 | sub(P3, One, a); debug(a); |
| 405 | modmult(a, c, bigmod, b); debug(b); |
| 406 | |
| 407 | modpow(Two, b, mod, a); debug(a); |
| 408 | |
| 409 | return 0; |
| 410 | } |
| 411 | |
| 412 | #endif |