374330e2 |
1 | /* |
2 | * RSA implementation just sufficient for ssh client-side |
3 | * initialisation step |
7ef88f13 |
4 | * Modified by Joris, Jun 1999. |
374330e2 |
5 | */ |
6 | |
7ef88f13 |
7 | #define JORIS_RSA |
8 | |
374330e2 |
9 | /*#include <windows.h> |
10 | #define RSADEBUG |
11 | #define DLVL 2 |
12 | #include "stel.h"*/ |
13 | |
14 | #include <stdio.h> |
15 | #include <stdlib.h> |
16 | #include <string.h> |
17 | |
18 | #include "ssh.h" |
19 | |
20 | typedef unsigned short *Bignum; |
21 | |
22 | static unsigned short Zero[1] = { 0 }; |
23 | |
24 | #if defined TESTMODE || defined RSADEBUG |
25 | #ifndef DLVL |
26 | #define DLVL 10000 |
27 | #endif |
28 | #define debug(x) bndebug(#x,x) |
29 | static int level = 0; |
30 | static void bndebug(char *name, Bignum b) { |
31 | int i; |
32 | int w = 50-level-strlen(name)-5*b[0]; |
33 | if (level >= DLVL) |
34 | return; |
35 | if (w < 0) w = 0; |
36 | dprintf("%*s%s%*s", level, "", name, w, ""); |
37 | for (i=b[0]; i>0; i--) |
38 | dprintf(" %04x", b[i]); |
39 | dprintf("\n"); |
40 | } |
41 | #define dmsg(x) do {if(level<DLVL){dprintf("%*s",level,"");printf x;}} while(0) |
42 | #define enter(x) do { dmsg(x); level += 4; } while(0) |
43 | #define leave(x) do { level -= 4; dmsg(x); } while(0) |
44 | #else |
45 | #define debug(x) |
46 | #define dmsg(x) |
47 | #define enter(x) |
48 | #define leave(x) |
49 | #endif |
50 | |
51 | static Bignum newbn(int length) { |
52 | Bignum b = malloc((length+1)*sizeof(unsigned short)); |
53 | if (!b) |
54 | abort(); /* FIXME */ |
55 | b[0] = length; |
56 | return b; |
57 | } |
58 | |
59 | static void freebn(Bignum b) { |
60 | free(b); |
61 | } |
62 | |
7ef88f13 |
63 | #ifdef JORIS_RSA |
64 | |
65 | /* |
66 | * Compute c = a * b. |
67 | * Input is in the first len words of a and b. |
68 | * Result is returned in the first 2*len words of c. |
69 | */ |
70 | static void bigmul(unsigned short *a, unsigned short *b, unsigned short *c, |
71 | int len) |
72 | { |
73 | int i, j; |
74 | unsigned long ai, t; |
75 | |
76 | for (j = len - 1; j >= 0; j--) |
77 | c[j+len] = 0; |
78 | |
79 | for (i = len - 1; i >= 0; i--) { |
80 | ai = a[i]; |
81 | t = 0; |
82 | for (j = len - 1; j >= 0; j--) { |
83 | t += ai * (unsigned long) b[j]; |
84 | t += (unsigned long) c[i+j+1]; |
85 | c[i+j+1] = t; |
86 | t = t >> 16; |
87 | } |
88 | c[i] = t; |
89 | } |
90 | } |
91 | |
92 | |
93 | /* |
94 | * Compute a = a % m. |
95 | * Input in first 2*len words of a and first len words of m. |
96 | * Output in first 2*len words of a (of which first len words will be zero). |
97 | * The MSW of m MUST have its high bit set. |
98 | */ |
99 | static void bigmod(unsigned short *a, unsigned short *m, int len) |
100 | { |
101 | unsigned short m0, m1; |
102 | unsigned int h; |
103 | int i, k; |
104 | |
105 | /* Special case for len == 1 */ |
106 | if (len == 1) { |
107 | a[1] = (((long) a[0] << 16) + a[1]) % m[0]; |
108 | a[0] = 0; |
109 | return; |
110 | } |
111 | |
112 | m0 = m[0]; |
113 | m1 = m[1]; |
114 | |
115 | for (i = 0; i <= len; i++) { |
116 | unsigned long t; |
117 | unsigned int q, r, c; |
118 | |
119 | if (i == 0) { |
120 | h = 0; |
121 | } else { |
122 | h = a[i-1]; |
123 | a[i-1] = 0; |
124 | } |
125 | |
126 | /* Find q = h:a[i] / m0 */ |
127 | t = ((unsigned long) h << 16) + a[i]; |
128 | q = t / m0; |
129 | r = t % m0; |
130 | |
131 | /* Refine our estimate of q by looking at |
132 | h:a[i]:a[i+1] / m0:m1 */ |
133 | t = (long) m1 * (long) q; |
134 | if (t > ((unsigned long) r << 16) + a[i+1]) { |
135 | q--; |
136 | t -= m1; |
137 | r = (r + m0) & 0xffff; /* overflow? */ |
138 | if (r >= m0 && t > ((unsigned long) r << 16) + a[i+1]) |
139 | q--; |
140 | } |
141 | |
142 | /* Substract q * m from a[i...] */ |
143 | c = 0; |
144 | for (k = len - 1; k >= 0; k--) { |
145 | t = (long) q * (long) m[k]; |
146 | t += c; |
147 | c = t >> 16; |
148 | if ((unsigned short) t > a[i+k]) c++; |
149 | a[i+k] -= (unsigned short) t; |
150 | } |
151 | |
152 | /* Add back m in case of borrow */ |
153 | if (c != h) { |
154 | t = 0; |
155 | for (k = len - 1; k >= 0; k--) { |
156 | t += m[k]; |
157 | t += a[i+k]; |
158 | a[i+k] = t; |
159 | t = t >> 16; |
160 | } |
161 | } |
162 | } |
163 | } |
164 | |
165 | |
166 | /* |
167 | * Compute (base ^ exp) % mod. |
168 | * The base MUST be smaller than the modulus. |
169 | * The most significant word of mod MUST be non-zero. |
170 | * We assume that the result array is the same size as the mod array. |
171 | */ |
172 | static void modpow(Bignum base, Bignum exp, Bignum mod, Bignum result) |
173 | { |
174 | unsigned short *a, *b, *n, *m; |
175 | int mshift; |
176 | int mlen, i, j; |
177 | |
178 | /* Allocate m of size mlen, copy mod to m */ |
179 | /* We use big endian internally */ |
180 | mlen = mod[0]; |
181 | m = malloc(mlen * sizeof(unsigned short)); |
182 | for (j = 0; j < mlen; j++) m[j] = mod[mod[0] - j]; |
183 | |
184 | /* Shift m left to make msb bit set */ |
185 | for (mshift = 0; mshift < 15; mshift++) |
186 | if ((m[0] << mshift) & 0x8000) break; |
187 | if (mshift) { |
188 | for (i = 0; i < mlen - 1; i++) |
189 | m[i] = (m[i] << mshift) | (m[i+1] >> (16-mshift)); |
190 | m[mlen-1] = m[mlen-1] << mshift; |
191 | } |
192 | |
193 | /* Allocate n of size mlen, copy base to n */ |
194 | n = malloc(mlen * sizeof(unsigned short)); |
195 | i = mlen - base[0]; |
196 | for (j = 0; j < i; j++) n[j] = 0; |
197 | for (j = 0; j < base[0]; j++) n[i+j] = base[base[0] - j]; |
198 | |
199 | /* Allocate a and b of size 2*mlen. Set a = 1 */ |
200 | a = malloc(2 * mlen * sizeof(unsigned short)); |
201 | b = malloc(2 * mlen * sizeof(unsigned short)); |
202 | for (i = 0; i < 2*mlen; i++) a[i] = 0; |
203 | a[2*mlen-1] = 1; |
204 | |
205 | /* Skip leading zero bits of exp. */ |
206 | i = 0; j = 15; |
207 | while (i < exp[0] && (exp[exp[0] - i] & (1 << j)) == 0) { |
208 | j--; |
209 | if (j < 0) { i++; j = 15; } |
210 | } |
211 | |
212 | /* Main computation */ |
213 | while (i < exp[0]) { |
214 | while (j >= 0) { |
215 | bigmul(a + mlen, a + mlen, b, mlen); |
216 | bigmod(b, m, mlen); |
217 | if ((exp[exp[0] - i] & (1 << j)) != 0) { |
218 | bigmul(b + mlen, n, a, mlen); |
219 | bigmod(a, m, mlen); |
220 | } else { |
221 | unsigned short *t; |
222 | t = a; a = b; b = t; |
223 | } |
224 | j--; |
225 | } |
226 | i++; j = 15; |
227 | } |
228 | |
229 | /* Fixup result in case the modulus was shifted */ |
230 | if (mshift) { |
231 | for (i = mlen - 1; i < 2*mlen - 1; i++) |
232 | a[i] = (a[i] << mshift) | (a[i+1] >> (16-mshift)); |
233 | a[2*mlen-1] = a[2*mlen-1] << mshift; |
234 | bigmod(a, m, mlen); |
235 | for (i = 2*mlen - 1; i >= mlen; i--) |
236 | a[i] = (a[i] >> mshift) | (a[i-1] << (16-mshift)); |
237 | } |
238 | |
239 | /* Copy result to buffer */ |
240 | for (i = 0; i < mlen; i++) |
241 | result[result[0] - i] = a[i+mlen]; |
242 | |
243 | /* Free temporary arrays */ |
244 | for (i = 0; i < 2*mlen; i++) a[i] = 0; free(a); |
245 | for (i = 0; i < 2*mlen; i++) b[i] = 0; free(b); |
246 | for (i = 0; i < mlen; i++) m[i] = 0; free(m); |
247 | for (i = 0; i < mlen; i++) n[i] = 0; free(n); |
248 | } |
249 | |
250 | #else |
251 | |
374330e2 |
252 | static int msb(Bignum r) { |
253 | int i; |
254 | int j; |
255 | unsigned short n; |
256 | |
257 | for (i=r[0]; i>0; i--) |
258 | if (r[i]) |
259 | break; |
260 | |
261 | j = (i-1)*16; |
262 | n = r[i]; |
263 | if (n & 0xFF00) j += 8, n >>= 8; |
264 | if (n & 0x00F0) j += 4, n >>= 4; |
265 | if (n & 0x000C) j += 2, n >>= 2; |
266 | if (n & 0x0002) j += 1, n >>= 1; |
267 | |
268 | return j; |
269 | } |
270 | |
271 | static void add(Bignum r1, Bignum r2, Bignum result) { |
272 | int i; |
273 | long stuff = 0; |
274 | |
275 | enter((">add\n")); |
276 | debug(r1); |
277 | debug(r2); |
278 | |
279 | for (i = 1 ;; i++) { |
280 | if (i <= r1[0]) |
281 | stuff += r1[i]; |
282 | if (i <= r2[0]) |
283 | stuff += r2[i]; |
284 | if (i <= result[0]) |
285 | result[i] = stuff & 0xFFFFU; |
286 | if (i > r1[0] && i > r2[0] && i >= result[0]) |
287 | break; |
288 | stuff >>= 16; |
289 | } |
290 | |
291 | debug(result); |
292 | leave(("<add\n")); |
293 | } |
294 | |
295 | static void sub(Bignum r1, Bignum r2, Bignum result) { |
296 | int i; |
297 | long stuff = 0; |
298 | |
299 | enter((">sub\n")); |
300 | debug(r1); |
301 | debug(r2); |
302 | |
303 | for (i = 1 ;; i++) { |
304 | if (i <= r1[0]) |
305 | stuff += r1[i]; |
306 | if (i <= r2[0]) |
307 | stuff -= r2[i]; |
308 | if (i <= result[0]) |
309 | result[i] = stuff & 0xFFFFU; |
310 | if (i > r1[0] && i > r2[0] && i >= result[0]) |
311 | break; |
312 | stuff = stuff<0 ? -1 : 0; |
313 | } |
314 | |
315 | debug(result); |
316 | leave(("<sub\n")); |
317 | } |
318 | |
319 | static int ge(Bignum r1, Bignum r2) { |
320 | int i; |
321 | |
322 | enter((">ge\n")); |
323 | debug(r1); |
324 | debug(r2); |
325 | |
326 | if (r1[0] < r2[0]) |
327 | i = r2[0]; |
328 | else |
329 | i = r1[0]; |
330 | |
331 | while (i > 0) { |
332 | unsigned short n1 = (i > r1[0] ? 0 : r1[i]); |
333 | unsigned short n2 = (i > r2[0] ? 0 : r2[i]); |
334 | |
335 | if (n1 > n2) { |
336 | dmsg(("greater\n")); |
337 | leave(("<ge\n")); |
338 | return 1; /* r1 > r2 */ |
339 | } else if (n1 < n2) { |
340 | dmsg(("less\n")); |
341 | leave(("<ge\n")); |
342 | return 0; /* r1 < r2 */ |
343 | } |
344 | |
345 | i--; |
346 | } |
347 | |
348 | dmsg(("equal\n")); |
349 | leave(("<ge\n")); |
350 | return 1; /* r1 = r2 */ |
351 | } |
352 | |
353 | static void modmult(Bignum r1, Bignum r2, Bignum modulus, Bignum result) { |
354 | Bignum temp = newbn(modulus[0]+1); |
355 | Bignum tmp2 = newbn(modulus[0]+1); |
356 | int i; |
357 | int bit, bits, digit, smallbit; |
358 | |
359 | enter((">modmult\n")); |
360 | debug(r1); |
361 | debug(r2); |
362 | debug(modulus); |
363 | |
364 | for (i=1; i<=result[0]; i++) |
365 | result[i] = 0; /* result := 0 */ |
366 | for (i=1; i<=temp[0]; i++) |
367 | temp[i] = (i > r2[0] ? 0 : r2[i]); /* temp := r2 */ |
368 | |
369 | bits = 1+msb(r1); |
370 | |
371 | for (bit = 0; bit < bits; bit++) { |
372 | digit = 1 + bit / 16; |
373 | smallbit = bit % 16; |
374 | |
375 | debug(temp); |
376 | if (digit <= r1[0] && (r1[digit] & (1<<smallbit))) { |
377 | dmsg(("bit %d\n", bit)); |
378 | add(temp, result, tmp2); |
379 | if (ge(tmp2, modulus)) |
380 | sub(tmp2, modulus, result); |
381 | else |
382 | add(tmp2, Zero, result); |
383 | debug(result); |
384 | } |
385 | |
386 | add(temp, temp, tmp2); |
387 | if (ge(tmp2, modulus)) |
388 | sub(tmp2, modulus, temp); |
389 | else |
390 | add(tmp2, Zero, temp); |
391 | } |
392 | |
393 | freebn(temp); |
394 | freebn(tmp2); |
395 | |
396 | debug(result); |
397 | leave(("<modmult\n")); |
398 | } |
399 | |
400 | static void modpow(Bignum r1, Bignum r2, Bignum modulus, Bignum result) { |
401 | Bignum temp = newbn(modulus[0]+1); |
402 | Bignum tmp2 = newbn(modulus[0]+1); |
403 | int i; |
404 | int bit, bits, digit, smallbit; |
405 | |
406 | enter((">modpow\n")); |
407 | debug(r1); |
408 | debug(r2); |
409 | debug(modulus); |
410 | |
411 | for (i=1; i<=result[0]; i++) |
412 | result[i] = (i==1); /* result := 1 */ |
413 | for (i=1; i<=temp[0]; i++) |
414 | temp[i] = (i > r1[0] ? 0 : r1[i]); /* temp := r1 */ |
415 | |
416 | bits = 1+msb(r2); |
417 | |
418 | for (bit = 0; bit < bits; bit++) { |
419 | digit = 1 + bit / 16; |
420 | smallbit = bit % 16; |
421 | |
422 | debug(temp); |
423 | if (digit <= r2[0] && (r2[digit] & (1<<smallbit))) { |
424 | dmsg(("bit %d\n", bit)); |
425 | modmult(temp, result, modulus, tmp2); |
426 | add(tmp2, Zero, result); |
427 | debug(result); |
428 | } |
429 | |
430 | modmult(temp, temp, modulus, tmp2); |
431 | add(tmp2, Zero, temp); |
432 | } |
433 | |
434 | freebn(temp); |
435 | freebn(tmp2); |
436 | |
437 | debug(result); |
438 | leave(("<modpow\n")); |
439 | } |
440 | |
7ef88f13 |
441 | #endif |
442 | |
374330e2 |
443 | int makekey(unsigned char *data, struct RSAKey *result, |
444 | unsigned char **keystr) { |
445 | unsigned char *p = data; |
446 | Bignum bn[2]; |
447 | int i, j; |
448 | int w, b; |
449 | |
450 | result->bits = 0; |
451 | for (i=0; i<4; i++) |
452 | result->bits = (result->bits << 8) + *p++; |
453 | |
454 | for (j=0; j<2; j++) { |
455 | |
456 | w = 0; |
457 | for (i=0; i<2; i++) |
458 | w = (w << 8) + *p++; |
459 | |
460 | result->bytes = b = (w+7)/8; /* bits -> bytes */ |
461 | w = (w+15)/16; /* bits -> words */ |
462 | |
463 | bn[j] = newbn(w); |
464 | |
465 | if (keystr) *keystr = p; /* point at key string, second time */ |
466 | |
467 | for (i=1; i<=w; i++) |
468 | bn[j][i] = 0; |
469 | for (i=0; i<b; i++) { |
470 | unsigned char byte = *p++; |
471 | if ((b-i) & 1) |
472 | bn[j][w-i/2] |= byte; |
473 | else |
474 | bn[j][w-i/2] |= byte<<8; |
475 | } |
476 | |
477 | debug(bn[j]); |
478 | |
479 | } |
480 | |
481 | result->exponent = bn[0]; |
482 | result->modulus = bn[1]; |
483 | |
484 | return p - data; |
485 | } |
486 | |
487 | void rsaencrypt(unsigned char *data, int length, struct RSAKey *key) { |
488 | Bignum b1, b2; |
489 | int w, i; |
490 | unsigned char *p; |
491 | |
492 | debug(key->exponent); |
493 | |
494 | memmove(data+key->bytes-length, data, length); |
495 | data[0] = 0; |
496 | data[1] = 2; |
497 | |
498 | for (i = 2; i < key->bytes-length-1; i++) { |
499 | do { |
500 | data[i] = random_byte(); |
501 | } while (data[i] == 0); |
502 | } |
503 | data[key->bytes-length-1] = 0; |
504 | |
505 | w = (key->bytes+1)/2; |
506 | |
507 | b1 = newbn(w); |
508 | b2 = newbn(w); |
509 | |
510 | p = data; |
511 | for (i=1; i<=w; i++) |
512 | b1[i] = 0; |
513 | for (i=0; i<key->bytes; i++) { |
514 | unsigned char byte = *p++; |
515 | if ((key->bytes-i) & 1) |
516 | b1[w-i/2] |= byte; |
517 | else |
518 | b1[w-i/2] |= byte<<8; |
519 | } |
520 | |
521 | debug(b1); |
522 | |
523 | modpow(b1, key->exponent, key->modulus, b2); |
524 | |
525 | debug(b2); |
526 | |
527 | p = data; |
528 | for (i=0; i<key->bytes; i++) { |
529 | unsigned char b; |
530 | if (i & 1) |
531 | b = b2[w-i/2] & 0xFF; |
532 | else |
533 | b = b2[w-i/2] >> 8; |
534 | *p++ = b; |
535 | } |
536 | |
537 | freebn(b1); |
538 | freebn(b2); |
539 | } |
540 | |
541 | int rsastr_len(struct RSAKey *key) { |
542 | Bignum md, ex; |
543 | |
544 | md = key->modulus; |
545 | ex = key->exponent; |
546 | return 4 * (ex[0]+md[0]) + 10; |
547 | } |
548 | |
549 | void rsastr_fmt(char *str, struct RSAKey *key) { |
550 | Bignum md, ex; |
551 | int len = 0, i; |
552 | |
553 | md = key->modulus; |
554 | ex = key->exponent; |
555 | |
556 | for (i=1; i<=ex[0]; i++) { |
557 | sprintf(str+len, "%04x", ex[i]); |
558 | len += strlen(str+len); |
559 | } |
560 | str[len++] = '/'; |
561 | for (i=1; i<=md[0]; i++) { |
562 | sprintf(str+len, "%04x", md[i]); |
563 | len += strlen(str+len); |
564 | } |
565 | str[len] = '\0'; |
566 | } |
567 | |
568 | #ifdef TESTMODE |
569 | |
570 | #ifndef NODDY |
571 | #define p1 10007 |
572 | #define p2 10069 |
573 | #define p3 10177 |
574 | #else |
575 | #define p1 3 |
576 | #define p2 7 |
577 | #define p3 13 |
578 | #endif |
579 | |
580 | unsigned short P1[2] = { 1, p1 }; |
581 | unsigned short P2[2] = { 1, p2 }; |
582 | unsigned short P3[2] = { 1, p3 }; |
583 | unsigned short bigmod[5] = { 4, 0, 0, 0, 32768U }; |
584 | unsigned short mod[5] = { 4, 0, 0, 0, 0 }; |
585 | unsigned short a[5] = { 4, 0, 0, 0, 0 }; |
586 | unsigned short b[5] = { 4, 0, 0, 0, 0 }; |
587 | unsigned short c[5] = { 4, 0, 0, 0, 0 }; |
588 | unsigned short One[2] = { 1, 1 }; |
589 | unsigned short Two[2] = { 1, 2 }; |
590 | |
591 | int main(void) { |
592 | modmult(P1, P2, bigmod, a); debug(a); |
593 | modmult(a, P3, bigmod, mod); debug(mod); |
594 | |
595 | sub(P1, One, a); debug(a); |
596 | sub(P2, One, b); debug(b); |
597 | modmult(a, b, bigmod, c); debug(c); |
598 | sub(P3, One, a); debug(a); |
599 | modmult(a, c, bigmod, b); debug(b); |
600 | |
601 | modpow(Two, b, mod, a); debug(a); |
602 | |
603 | return 0; |
604 | } |
605 | |
606 | #endif |