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Commit | Line | Data |
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1c1af145 | 1 | /* |
2 | * RSA implementation for PuTTY. | |
3 | */ | |
4 | ||
5 | #include <stdio.h> | |
6 | #include <stdlib.h> | |
7 | #include <string.h> | |
8 | #include <assert.h> | |
9 | ||
10 | #include "ssh.h" | |
11 | #include "misc.h" | |
12 | ||
13 | int makekey(unsigned char *data, int len, struct RSAKey *result, | |
14 | unsigned char **keystr, int order) | |
15 | { | |
16 | unsigned char *p = data; | |
17 | int i, n; | |
18 | ||
19 | if (len < 4) | |
20 | return -1; | |
21 | ||
22 | if (result) { | |
23 | result->bits = 0; | |
24 | for (i = 0; i < 4; i++) | |
25 | result->bits = (result->bits << 8) + *p++; | |
26 | } else | |
27 | p += 4; | |
28 | ||
29 | len -= 4; | |
30 | ||
31 | /* | |
32 | * order=0 means exponent then modulus (the keys sent by the | |
33 | * server). order=1 means modulus then exponent (the keys | |
34 | * stored in a keyfile). | |
35 | */ | |
36 | ||
37 | if (order == 0) { | |
38 | n = ssh1_read_bignum(p, len, result ? &result->exponent : NULL); | |
39 | if (n < 0) return -1; | |
40 | p += n; | |
41 | len -= n; | |
42 | } | |
43 | ||
44 | n = ssh1_read_bignum(p, len, result ? &result->modulus : NULL); | |
45 | if (n < 0 || (result && bignum_bitcount(result->modulus) == 0)) return -1; | |
46 | if (result) | |
47 | result->bytes = n - 2; | |
48 | if (keystr) | |
49 | *keystr = p + 2; | |
50 | p += n; | |
51 | len -= n; | |
52 | ||
53 | if (order == 1) { | |
54 | n = ssh1_read_bignum(p, len, result ? &result->exponent : NULL); | |
55 | if (n < 0) return -1; | |
56 | p += n; | |
57 | len -= n; | |
58 | } | |
59 | return p - data; | |
60 | } | |
61 | ||
62 | int makeprivate(unsigned char *data, int len, struct RSAKey *result) | |
63 | { | |
64 | return ssh1_read_bignum(data, len, &result->private_exponent); | |
65 | } | |
66 | ||
67 | int rsaencrypt(unsigned char *data, int length, struct RSAKey *key) | |
68 | { | |
69 | Bignum b1, b2; | |
70 | int i; | |
71 | unsigned char *p; | |
72 | ||
73 | if (key->bytes < length + 4) | |
74 | return 0; /* RSA key too short! */ | |
75 | ||
76 | memmove(data + key->bytes - length, data, length); | |
77 | data[0] = 0; | |
78 | data[1] = 2; | |
79 | ||
80 | for (i = 2; i < key->bytes - length - 1; i++) { | |
81 | do { | |
82 | data[i] = random_byte(); | |
83 | } while (data[i] == 0); | |
84 | } | |
85 | data[key->bytes - length - 1] = 0; | |
86 | ||
87 | b1 = bignum_from_bytes(data, key->bytes); | |
88 | ||
89 | b2 = modpow(b1, key->exponent, key->modulus); | |
90 | ||
91 | p = data; | |
92 | for (i = key->bytes; i--;) { | |
93 | *p++ = bignum_byte(b2, i); | |
94 | } | |
95 | ||
96 | freebn(b1); | |
97 | freebn(b2); | |
98 | ||
99 | return 1; | |
100 | } | |
101 | ||
102 | static void sha512_mpint(SHA512_State * s, Bignum b) | |
103 | { | |
104 | unsigned char lenbuf[4]; | |
105 | int len; | |
106 | len = (bignum_bitcount(b) + 8) / 8; | |
107 | PUT_32BIT(lenbuf, len); | |
108 | SHA512_Bytes(s, lenbuf, 4); | |
109 | while (len-- > 0) { | |
110 | lenbuf[0] = bignum_byte(b, len); | |
111 | SHA512_Bytes(s, lenbuf, 1); | |
112 | } | |
113 | memset(lenbuf, 0, sizeof(lenbuf)); | |
114 | } | |
115 | ||
116 | /* | |
117 | * Compute (base ^ exp) % mod, provided mod == p * q, with p,q | |
118 | * distinct primes, and iqmp is the multiplicative inverse of q mod p. | |
119 | * Uses Chinese Remainder Theorem to speed computation up over the | |
120 | * obvious implementation of a single big modpow. | |
121 | */ | |
122 | Bignum crt_modpow(Bignum base, Bignum exp, Bignum mod, | |
123 | Bignum p, Bignum q, Bignum iqmp) | |
124 | { | |
125 | Bignum pm1, qm1, pexp, qexp, presult, qresult, diff, multiplier, ret0, ret; | |
126 | ||
127 | /* | |
128 | * Reduce the exponent mod phi(p) and phi(q), to save time when | |
129 | * exponentiating mod p and mod q respectively. Of course, since p | |
130 | * and q are prime, phi(p) == p-1 and similarly for q. | |
131 | */ | |
132 | pm1 = copybn(p); | |
133 | decbn(pm1); | |
134 | qm1 = copybn(q); | |
135 | decbn(qm1); | |
136 | pexp = bigmod(exp, pm1); | |
137 | qexp = bigmod(exp, qm1); | |
138 | ||
139 | /* | |
140 | * Do the two modpows. | |
141 | */ | |
142 | presult = modpow(base, pexp, p); | |
143 | qresult = modpow(base, qexp, q); | |
144 | ||
145 | /* | |
146 | * Recombine the results. We want a value which is congruent to | |
147 | * qresult mod q, and to presult mod p. | |
148 | * | |
149 | * We know that iqmp * q is congruent to 1 * mod p (by definition | |
150 | * of iqmp) and to 0 mod q (obviously). So we start with qresult | |
151 | * (which is congruent to qresult mod both primes), and add on | |
152 | * (presult-qresult) * (iqmp * q) which adjusts it to be congruent | |
153 | * to presult mod p without affecting its value mod q. | |
154 | */ | |
155 | if (bignum_cmp(presult, qresult) < 0) { | |
156 | /* | |
157 | * Can't subtract presult from qresult without first adding on | |
158 | * p. | |
159 | */ | |
160 | Bignum tmp = presult; | |
161 | presult = bigadd(presult, p); | |
162 | freebn(tmp); | |
163 | } | |
164 | diff = bigsub(presult, qresult); | |
165 | multiplier = bigmul(iqmp, q); | |
166 | ret0 = bigmuladd(multiplier, diff, qresult); | |
167 | ||
168 | /* | |
169 | * Finally, reduce the result mod n. | |
170 | */ | |
171 | ret = bigmod(ret0, mod); | |
172 | ||
173 | /* | |
174 | * Free all the intermediate results before returning. | |
175 | */ | |
176 | freebn(pm1); | |
177 | freebn(qm1); | |
178 | freebn(pexp); | |
179 | freebn(qexp); | |
180 | freebn(presult); | |
181 | freebn(qresult); | |
182 | freebn(diff); | |
183 | freebn(multiplier); | |
184 | freebn(ret0); | |
185 | ||
186 | return ret; | |
187 | } | |
188 | ||
189 | /* | |
190 | * This function is a wrapper on modpow(). It has the same effect as | |
191 | * modpow(), but employs RSA blinding to protect against timing | |
192 | * attacks and also uses the Chinese Remainder Theorem (implemented | |
193 | * above, in crt_modpow()) to speed up the main operation. | |
194 | */ | |
195 | static Bignum rsa_privkey_op(Bignum input, struct RSAKey *key) | |
196 | { | |
197 | Bignum random, random_encrypted, random_inverse; | |
198 | Bignum input_blinded, ret_blinded; | |
199 | Bignum ret; | |
200 | ||
201 | SHA512_State ss; | |
202 | unsigned char digest512[64]; | |
203 | int digestused = lenof(digest512); | |
204 | int hashseq = 0; | |
205 | ||
206 | /* | |
207 | * Start by inventing a random number chosen uniformly from the | |
208 | * range 2..modulus-1. (We do this by preparing a random number | |
209 | * of the right length and retrying if it's greater than the | |
210 | * modulus, to prevent any potential Bleichenbacher-like | |
211 | * attacks making use of the uneven distribution within the | |
212 | * range that would arise from just reducing our number mod n. | |
213 | * There are timing implications to the potential retries, of | |
214 | * course, but all they tell you is the modulus, which you | |
215 | * already knew.) | |
216 | * | |
217 | * To preserve determinism and avoid Pageant needing to share | |
218 | * the random number pool, we actually generate this `random' | |
219 | * number by hashing stuff with the private key. | |
220 | */ | |
221 | while (1) { | |
222 | int bits, byte, bitsleft, v; | |
223 | random = copybn(key->modulus); | |
224 | /* | |
225 | * Find the topmost set bit. (This function will return its | |
226 | * index plus one.) Then we'll set all bits from that one | |
227 | * downwards randomly. | |
228 | */ | |
229 | bits = bignum_bitcount(random); | |
230 | byte = 0; | |
231 | bitsleft = 0; | |
232 | while (bits--) { | |
233 | if (bitsleft <= 0) { | |
234 | bitsleft = 8; | |
235 | /* | |
236 | * Conceptually the following few lines are equivalent to | |
237 | * byte = random_byte(); | |
238 | */ | |
239 | if (digestused >= lenof(digest512)) { | |
240 | unsigned char seqbuf[4]; | |
241 | PUT_32BIT(seqbuf, hashseq); | |
242 | SHA512_Init(&ss); | |
243 | SHA512_Bytes(&ss, "RSA deterministic blinding", 26); | |
244 | SHA512_Bytes(&ss, seqbuf, sizeof(seqbuf)); | |
245 | sha512_mpint(&ss, key->private_exponent); | |
246 | SHA512_Final(&ss, digest512); | |
247 | hashseq++; | |
248 | ||
249 | /* | |
250 | * Now hash that digest plus the signature | |
251 | * input. | |
252 | */ | |
253 | SHA512_Init(&ss); | |
254 | SHA512_Bytes(&ss, digest512, sizeof(digest512)); | |
255 | sha512_mpint(&ss, input); | |
256 | SHA512_Final(&ss, digest512); | |
257 | ||
258 | digestused = 0; | |
259 | } | |
260 | byte = digest512[digestused++]; | |
261 | } | |
262 | v = byte & 1; | |
263 | byte >>= 1; | |
264 | bitsleft--; | |
265 | bignum_set_bit(random, bits, v); | |
266 | } | |
267 | ||
268 | /* | |
269 | * Now check that this number is strictly greater than | |
270 | * zero, and strictly less than modulus. | |
271 | */ | |
272 | if (bignum_cmp(random, Zero) <= 0 || | |
273 | bignum_cmp(random, key->modulus) >= 0) { | |
274 | freebn(random); | |
275 | continue; | |
276 | } else { | |
277 | break; | |
278 | } | |
279 | } | |
280 | ||
281 | /* | |
282 | * RSA blinding relies on the fact that (xy)^d mod n is equal | |
283 | * to (x^d mod n) * (y^d mod n) mod n. We invent a random pair | |
284 | * y and y^d; then we multiply x by y, raise to the power d mod | |
285 | * n as usual, and divide by y^d to recover x^d. Thus an | |
286 | * attacker can't correlate the timing of the modpow with the | |
287 | * input, because they don't know anything about the number | |
288 | * that was input to the actual modpow. | |
289 | * | |
290 | * The clever bit is that we don't have to do a huge modpow to | |
291 | * get y and y^d; we will use the number we just invented as | |
292 | * _y^d_, and use the _public_ exponent to compute (y^d)^e = y | |
293 | * from it, which is much faster to do. | |
294 | */ | |
295 | random_encrypted = crt_modpow(random, key->exponent, | |
296 | key->modulus, key->p, key->q, key->iqmp); | |
297 | random_inverse = modinv(random, key->modulus); | |
298 | input_blinded = modmul(input, random_encrypted, key->modulus); | |
299 | ret_blinded = crt_modpow(input_blinded, key->private_exponent, | |
300 | key->modulus, key->p, key->q, key->iqmp); | |
301 | ret = modmul(ret_blinded, random_inverse, key->modulus); | |
302 | ||
303 | freebn(ret_blinded); | |
304 | freebn(input_blinded); | |
305 | freebn(random_inverse); | |
306 | freebn(random_encrypted); | |
307 | freebn(random); | |
308 | ||
309 | return ret; | |
310 | } | |
311 | ||
312 | Bignum rsadecrypt(Bignum input, struct RSAKey *key) | |
313 | { | |
314 | return rsa_privkey_op(input, key); | |
315 | } | |
316 | ||
317 | int rsastr_len(struct RSAKey *key) | |
318 | { | |
319 | Bignum md, ex; | |
320 | int mdlen, exlen; | |
321 | ||
322 | md = key->modulus; | |
323 | ex = key->exponent; | |
324 | mdlen = (bignum_bitcount(md) + 15) / 16; | |
325 | exlen = (bignum_bitcount(ex) + 15) / 16; | |
326 | return 4 * (mdlen + exlen) + 20; | |
327 | } | |
328 | ||
329 | void rsastr_fmt(char *str, struct RSAKey *key) | |
330 | { | |
331 | Bignum md, ex; | |
332 | int len = 0, i, nibbles; | |
333 | static const char hex[] = "0123456789abcdef"; | |
334 | ||
335 | md = key->modulus; | |
336 | ex = key->exponent; | |
337 | ||
338 | len += sprintf(str + len, "0x"); | |
339 | ||
340 | nibbles = (3 + bignum_bitcount(ex)) / 4; | |
341 | if (nibbles < 1) | |
342 | nibbles = 1; | |
343 | for (i = nibbles; i--;) | |
344 | str[len++] = hex[(bignum_byte(ex, i / 2) >> (4 * (i % 2))) & 0xF]; | |
345 | ||
346 | len += sprintf(str + len, ",0x"); | |
347 | ||
348 | nibbles = (3 + bignum_bitcount(md)) / 4; | |
349 | if (nibbles < 1) | |
350 | nibbles = 1; | |
351 | for (i = nibbles; i--;) | |
352 | str[len++] = hex[(bignum_byte(md, i / 2) >> (4 * (i % 2))) & 0xF]; | |
353 | ||
354 | str[len] = '\0'; | |
355 | } | |
356 | ||
357 | /* | |
358 | * Generate a fingerprint string for the key. Compatible with the | |
359 | * OpenSSH fingerprint code. | |
360 | */ | |
361 | void rsa_fingerprint(char *str, int len, struct RSAKey *key) | |
362 | { | |
363 | struct MD5Context md5c; | |
364 | unsigned char digest[16]; | |
365 | char buffer[16 * 3 + 40]; | |
366 | int numlen, slen, i; | |
367 | ||
368 | MD5Init(&md5c); | |
369 | numlen = ssh1_bignum_length(key->modulus) - 2; | |
370 | for (i = numlen; i--;) { | |
371 | unsigned char c = bignum_byte(key->modulus, i); | |
372 | MD5Update(&md5c, &c, 1); | |
373 | } | |
374 | numlen = ssh1_bignum_length(key->exponent) - 2; | |
375 | for (i = numlen; i--;) { | |
376 | unsigned char c = bignum_byte(key->exponent, i); | |
377 | MD5Update(&md5c, &c, 1); | |
378 | } | |
379 | MD5Final(digest, &md5c); | |
380 | ||
381 | sprintf(buffer, "%d ", bignum_bitcount(key->modulus)); | |
382 | for (i = 0; i < 16; i++) | |
383 | sprintf(buffer + strlen(buffer), "%s%02x", i ? ":" : "", | |
384 | digest[i]); | |
385 | strncpy(str, buffer, len); | |
386 | str[len - 1] = '\0'; | |
387 | slen = strlen(str); | |
388 | if (key->comment && slen < len - 1) { | |
389 | str[slen] = ' '; | |
390 | strncpy(str + slen + 1, key->comment, len - slen - 1); | |
391 | str[len - 1] = '\0'; | |
392 | } | |
393 | } | |
394 | ||
395 | /* | |
396 | * Verify that the public data in an RSA key matches the private | |
397 | * data. We also check the private data itself: we ensure that p > | |
398 | * q and that iqmp really is the inverse of q mod p. | |
399 | */ | |
400 | int rsa_verify(struct RSAKey *key) | |
401 | { | |
402 | Bignum n, ed, pm1, qm1; | |
403 | int cmp; | |
404 | ||
405 | /* n must equal pq. */ | |
406 | n = bigmul(key->p, key->q); | |
407 | cmp = bignum_cmp(n, key->modulus); | |
408 | freebn(n); | |
409 | if (cmp != 0) | |
410 | return 0; | |
411 | ||
412 | /* e * d must be congruent to 1, modulo (p-1) and modulo (q-1). */ | |
413 | pm1 = copybn(key->p); | |
414 | decbn(pm1); | |
415 | ed = modmul(key->exponent, key->private_exponent, pm1); | |
416 | cmp = bignum_cmp(ed, One); | |
417 | sfree(ed); | |
418 | if (cmp != 0) | |
419 | return 0; | |
420 | ||
421 | qm1 = copybn(key->q); | |
422 | decbn(qm1); | |
423 | ed = modmul(key->exponent, key->private_exponent, qm1); | |
424 | cmp = bignum_cmp(ed, One); | |
425 | sfree(ed); | |
426 | if (cmp != 0) | |
427 | return 0; | |
428 | ||
429 | /* | |
430 | * Ensure p > q. | |
431 | * | |
432 | * I have seen key blobs in the wild which were generated with | |
433 | * p < q, so instead of rejecting the key in this case we | |
434 | * should instead flip them round into the canonical order of | |
435 | * p > q. This also involves regenerating iqmp. | |
436 | */ | |
437 | if (bignum_cmp(key->p, key->q) <= 0) { | |
438 | Bignum tmp = key->p; | |
439 | key->p = key->q; | |
440 | key->q = tmp; | |
441 | ||
442 | freebn(key->iqmp); | |
443 | key->iqmp = modinv(key->q, key->p); | |
444 | } | |
445 | ||
446 | /* | |
447 | * Ensure iqmp * q is congruent to 1, modulo p. | |
448 | */ | |
449 | n = modmul(key->iqmp, key->q, key->p); | |
450 | cmp = bignum_cmp(n, One); | |
451 | sfree(n); | |
452 | if (cmp != 0) | |
453 | return 0; | |
454 | ||
455 | return 1; | |
456 | } | |
457 | ||
458 | /* Public key blob as used by Pageant: exponent before modulus. */ | |
459 | unsigned char *rsa_public_blob(struct RSAKey *key, int *len) | |
460 | { | |
461 | int length, pos; | |
462 | unsigned char *ret; | |
463 | ||
464 | length = (ssh1_bignum_length(key->modulus) + | |
465 | ssh1_bignum_length(key->exponent) + 4); | |
466 | ret = snewn(length, unsigned char); | |
467 | ||
468 | PUT_32BIT(ret, bignum_bitcount(key->modulus)); | |
469 | pos = 4; | |
470 | pos += ssh1_write_bignum(ret + pos, key->exponent); | |
471 | pos += ssh1_write_bignum(ret + pos, key->modulus); | |
472 | ||
473 | *len = length; | |
474 | return ret; | |
475 | } | |
476 | ||
477 | /* Given a public blob, determine its length. */ | |
478 | int rsa_public_blob_len(void *data, int maxlen) | |
479 | { | |
480 | unsigned char *p = (unsigned char *)data; | |
481 | int n; | |
482 | ||
483 | if (maxlen < 4) | |
484 | return -1; | |
485 | p += 4; /* length word */ | |
486 | maxlen -= 4; | |
487 | ||
488 | n = ssh1_read_bignum(p, maxlen, NULL); /* exponent */ | |
489 | if (n < 0) | |
490 | return -1; | |
491 | p += n; | |
492 | ||
493 | n = ssh1_read_bignum(p, maxlen, NULL); /* modulus */ | |
494 | if (n < 0) | |
495 | return -1; | |
496 | p += n; | |
497 | ||
498 | return p - (unsigned char *)data; | |
499 | } | |
500 | ||
501 | void freersakey(struct RSAKey *key) | |
502 | { | |
503 | if (key->modulus) | |
504 | freebn(key->modulus); | |
505 | if (key->exponent) | |
506 | freebn(key->exponent); | |
507 | if (key->private_exponent) | |
508 | freebn(key->private_exponent); | |
509 | if (key->p) | |
510 | freebn(key->p); | |
511 | if (key->q) | |
512 | freebn(key->q); | |
513 | if (key->iqmp) | |
514 | freebn(key->iqmp); | |
515 | if (key->comment) | |
516 | sfree(key->comment); | |
517 | } | |
518 | ||
519 | /* ---------------------------------------------------------------------- | |
520 | * Implementation of the ssh-rsa signing key type. | |
521 | */ | |
522 | ||
523 | static void getstring(char **data, int *datalen, char **p, int *length) | |
524 | { | |
525 | *p = NULL; | |
526 | if (*datalen < 4) | |
527 | return; | |
528 | *length = GET_32BIT(*data); | |
529 | *datalen -= 4; | |
530 | *data += 4; | |
531 | if (*datalen < *length) | |
532 | return; | |
533 | *p = *data; | |
534 | *data += *length; | |
535 | *datalen -= *length; | |
536 | } | |
537 | static Bignum getmp(char **data, int *datalen) | |
538 | { | |
539 | char *p; | |
540 | int length; | |
541 | Bignum b; | |
542 | ||
543 | getstring(data, datalen, &p, &length); | |
544 | if (!p) | |
545 | return NULL; | |
546 | b = bignum_from_bytes((unsigned char *)p, length); | |
547 | return b; | |
548 | } | |
549 | ||
550 | static void *rsa2_newkey(char *data, int len) | |
551 | { | |
552 | char *p; | |
553 | int slen; | |
554 | struct RSAKey *rsa; | |
555 | ||
556 | rsa = snew(struct RSAKey); | |
557 | if (!rsa) | |
558 | return NULL; | |
559 | getstring(&data, &len, &p, &slen); | |
560 | ||
561 | if (!p || slen != 7 || memcmp(p, "ssh-rsa", 7)) { | |
562 | sfree(rsa); | |
563 | return NULL; | |
564 | } | |
565 | rsa->exponent = getmp(&data, &len); | |
566 | rsa->modulus = getmp(&data, &len); | |
567 | rsa->private_exponent = NULL; | |
568 | rsa->p = rsa->q = rsa->iqmp = NULL; | |
569 | rsa->comment = NULL; | |
570 | ||
571 | return rsa; | |
572 | } | |
573 | ||
574 | static void rsa2_freekey(void *key) | |
575 | { | |
576 | struct RSAKey *rsa = (struct RSAKey *) key; | |
577 | freersakey(rsa); | |
578 | sfree(rsa); | |
579 | } | |
580 | ||
581 | static char *rsa2_fmtkey(void *key) | |
582 | { | |
583 | struct RSAKey *rsa = (struct RSAKey *) key; | |
584 | char *p; | |
585 | int len; | |
586 | ||
587 | len = rsastr_len(rsa); | |
588 | p = snewn(len, char); | |
589 | rsastr_fmt(p, rsa); | |
590 | return p; | |
591 | } | |
592 | ||
593 | static unsigned char *rsa2_public_blob(void *key, int *len) | |
594 | { | |
595 | struct RSAKey *rsa = (struct RSAKey *) key; | |
596 | int elen, mlen, bloblen; | |
597 | int i; | |
598 | unsigned char *blob, *p; | |
599 | ||
600 | elen = (bignum_bitcount(rsa->exponent) + 8) / 8; | |
601 | mlen = (bignum_bitcount(rsa->modulus) + 8) / 8; | |
602 | ||
603 | /* | |
604 | * string "ssh-rsa", mpint exp, mpint mod. Total 19+elen+mlen. | |
605 | * (three length fields, 12+7=19). | |
606 | */ | |
607 | bloblen = 19 + elen + mlen; | |
608 | blob = snewn(bloblen, unsigned char); | |
609 | p = blob; | |
610 | PUT_32BIT(p, 7); | |
611 | p += 4; | |
612 | memcpy(p, "ssh-rsa", 7); | |
613 | p += 7; | |
614 | PUT_32BIT(p, elen); | |
615 | p += 4; | |
616 | for (i = elen; i--;) | |
617 | *p++ = bignum_byte(rsa->exponent, i); | |
618 | PUT_32BIT(p, mlen); | |
619 | p += 4; | |
620 | for (i = mlen; i--;) | |
621 | *p++ = bignum_byte(rsa->modulus, i); | |
622 | assert(p == blob + bloblen); | |
623 | *len = bloblen; | |
624 | return blob; | |
625 | } | |
626 | ||
627 | static unsigned char *rsa2_private_blob(void *key, int *len) | |
628 | { | |
629 | struct RSAKey *rsa = (struct RSAKey *) key; | |
630 | int dlen, plen, qlen, ulen, bloblen; | |
631 | int i; | |
632 | unsigned char *blob, *p; | |
633 | ||
634 | dlen = (bignum_bitcount(rsa->private_exponent) + 8) / 8; | |
635 | plen = (bignum_bitcount(rsa->p) + 8) / 8; | |
636 | qlen = (bignum_bitcount(rsa->q) + 8) / 8; | |
637 | ulen = (bignum_bitcount(rsa->iqmp) + 8) / 8; | |
638 | ||
639 | /* | |
640 | * mpint private_exp, mpint p, mpint q, mpint iqmp. Total 16 + | |
641 | * sum of lengths. | |
642 | */ | |
643 | bloblen = 16 + dlen + plen + qlen + ulen; | |
644 | blob = snewn(bloblen, unsigned char); | |
645 | p = blob; | |
646 | PUT_32BIT(p, dlen); | |
647 | p += 4; | |
648 | for (i = dlen; i--;) | |
649 | *p++ = bignum_byte(rsa->private_exponent, i); | |
650 | PUT_32BIT(p, plen); | |
651 | p += 4; | |
652 | for (i = plen; i--;) | |
653 | *p++ = bignum_byte(rsa->p, i); | |
654 | PUT_32BIT(p, qlen); | |
655 | p += 4; | |
656 | for (i = qlen; i--;) | |
657 | *p++ = bignum_byte(rsa->q, i); | |
658 | PUT_32BIT(p, ulen); | |
659 | p += 4; | |
660 | for (i = ulen; i--;) | |
661 | *p++ = bignum_byte(rsa->iqmp, i); | |
662 | assert(p == blob + bloblen); | |
663 | *len = bloblen; | |
664 | return blob; | |
665 | } | |
666 | ||
667 | static void *rsa2_createkey(unsigned char *pub_blob, int pub_len, | |
668 | unsigned char *priv_blob, int priv_len) | |
669 | { | |
670 | struct RSAKey *rsa; | |
671 | char *pb = (char *) priv_blob; | |
672 | ||
673 | rsa = rsa2_newkey((char *) pub_blob, pub_len); | |
674 | rsa->private_exponent = getmp(&pb, &priv_len); | |
675 | rsa->p = getmp(&pb, &priv_len); | |
676 | rsa->q = getmp(&pb, &priv_len); | |
677 | rsa->iqmp = getmp(&pb, &priv_len); | |
678 | ||
679 | if (!rsa_verify(rsa)) { | |
680 | rsa2_freekey(rsa); | |
681 | return NULL; | |
682 | } | |
683 | ||
684 | return rsa; | |
685 | } | |
686 | ||
687 | static void *rsa2_openssh_createkey(unsigned char **blob, int *len) | |
688 | { | |
689 | char **b = (char **) blob; | |
690 | struct RSAKey *rsa; | |
691 | ||
692 | rsa = snew(struct RSAKey); | |
693 | if (!rsa) | |
694 | return NULL; | |
695 | rsa->comment = NULL; | |
696 | ||
697 | rsa->modulus = getmp(b, len); | |
698 | rsa->exponent = getmp(b, len); | |
699 | rsa->private_exponent = getmp(b, len); | |
700 | rsa->iqmp = getmp(b, len); | |
701 | rsa->p = getmp(b, len); | |
702 | rsa->q = getmp(b, len); | |
703 | ||
704 | if (!rsa->modulus || !rsa->exponent || !rsa->private_exponent || | |
705 | !rsa->iqmp || !rsa->p || !rsa->q) { | |
706 | sfree(rsa->modulus); | |
707 | sfree(rsa->exponent); | |
708 | sfree(rsa->private_exponent); | |
709 | sfree(rsa->iqmp); | |
710 | sfree(rsa->p); | |
711 | sfree(rsa->q); | |
712 | sfree(rsa); | |
713 | return NULL; | |
714 | } | |
715 | ||
716 | return rsa; | |
717 | } | |
718 | ||
719 | static int rsa2_openssh_fmtkey(void *key, unsigned char *blob, int len) | |
720 | { | |
721 | struct RSAKey *rsa = (struct RSAKey *) key; | |
722 | int bloblen, i; | |
723 | ||
724 | bloblen = | |
725 | ssh2_bignum_length(rsa->modulus) + | |
726 | ssh2_bignum_length(rsa->exponent) + | |
727 | ssh2_bignum_length(rsa->private_exponent) + | |
728 | ssh2_bignum_length(rsa->iqmp) + | |
729 | ssh2_bignum_length(rsa->p) + ssh2_bignum_length(rsa->q); | |
730 | ||
731 | if (bloblen > len) | |
732 | return bloblen; | |
733 | ||
734 | bloblen = 0; | |
735 | #define ENC(x) \ | |
736 | PUT_32BIT(blob+bloblen, ssh2_bignum_length((x))-4); bloblen += 4; \ | |
737 | for (i = ssh2_bignum_length((x))-4; i-- ;) blob[bloblen++]=bignum_byte((x),i); | |
738 | ENC(rsa->modulus); | |
739 | ENC(rsa->exponent); | |
740 | ENC(rsa->private_exponent); | |
741 | ENC(rsa->iqmp); | |
742 | ENC(rsa->p); | |
743 | ENC(rsa->q); | |
744 | ||
745 | return bloblen; | |
746 | } | |
747 | ||
748 | static int rsa2_pubkey_bits(void *blob, int len) | |
749 | { | |
750 | struct RSAKey *rsa; | |
751 | int ret; | |
752 | ||
753 | rsa = rsa2_newkey((char *) blob, len); | |
754 | ret = bignum_bitcount(rsa->modulus); | |
755 | rsa2_freekey(rsa); | |
756 | ||
757 | return ret; | |
758 | } | |
759 | ||
760 | static char *rsa2_fingerprint(void *key) | |
761 | { | |
762 | struct RSAKey *rsa = (struct RSAKey *) key; | |
763 | struct MD5Context md5c; | |
764 | unsigned char digest[16], lenbuf[4]; | |
765 | char buffer[16 * 3 + 40]; | |
766 | char *ret; | |
767 | int numlen, i; | |
768 | ||
769 | MD5Init(&md5c); | |
770 | MD5Update(&md5c, (unsigned char *)"\0\0\0\7ssh-rsa", 11); | |
771 | ||
772 | #define ADD_BIGNUM(bignum) \ | |
773 | numlen = (bignum_bitcount(bignum)+8)/8; \ | |
774 | PUT_32BIT(lenbuf, numlen); MD5Update(&md5c, lenbuf, 4); \ | |
775 | for (i = numlen; i-- ;) { \ | |
776 | unsigned char c = bignum_byte(bignum, i); \ | |
777 | MD5Update(&md5c, &c, 1); \ | |
778 | } | |
779 | ADD_BIGNUM(rsa->exponent); | |
780 | ADD_BIGNUM(rsa->modulus); | |
781 | #undef ADD_BIGNUM | |
782 | ||
783 | MD5Final(digest, &md5c); | |
784 | ||
785 | sprintf(buffer, "ssh-rsa %d ", bignum_bitcount(rsa->modulus)); | |
786 | for (i = 0; i < 16; i++) | |
787 | sprintf(buffer + strlen(buffer), "%s%02x", i ? ":" : "", | |
788 | digest[i]); | |
789 | ret = snewn(strlen(buffer) + 1, char); | |
790 | if (ret) | |
791 | strcpy(ret, buffer); | |
792 | return ret; | |
793 | } | |
794 | ||
795 | /* | |
796 | * This is the magic ASN.1/DER prefix that goes in the decoded | |
797 | * signature, between the string of FFs and the actual SHA hash | |
798 | * value. The meaning of it is: | |
799 | * | |
800 | * 00 -- this marks the end of the FFs; not part of the ASN.1 bit itself | |
801 | * | |
802 | * 30 21 -- a constructed SEQUENCE of length 0x21 | |
803 | * 30 09 -- a constructed sub-SEQUENCE of length 9 | |
804 | * 06 05 -- an object identifier, length 5 | |
805 | * 2B 0E 03 02 1A -- object id { 1 3 14 3 2 26 } | |
806 | * (the 1,3 comes from 0x2B = 43 = 40*1+3) | |
807 | * 05 00 -- NULL | |
808 | * 04 14 -- a primitive OCTET STRING of length 0x14 | |
809 | * [0x14 bytes of hash data follows] | |
810 | * | |
811 | * The object id in the middle there is listed as `id-sha1' in | |
812 | * ftp://ftp.rsasecurity.com/pub/pkcs/pkcs-1/pkcs-1v2-1d2.asn (the | |
813 | * ASN module for PKCS #1) and its expanded form is as follows: | |
814 | * | |
815 | * id-sha1 OBJECT IDENTIFIER ::= { | |
816 | * iso(1) identified-organization(3) oiw(14) secsig(3) | |
817 | * algorithms(2) 26 } | |
818 | */ | |
819 | static const unsigned char asn1_weird_stuff[] = { | |
820 | 0x00, 0x30, 0x21, 0x30, 0x09, 0x06, 0x05, 0x2B, | |
821 | 0x0E, 0x03, 0x02, 0x1A, 0x05, 0x00, 0x04, 0x14, | |
822 | }; | |
823 | ||
824 | #define ASN1_LEN ( (int) sizeof(asn1_weird_stuff) ) | |
825 | ||
826 | static int rsa2_verifysig(void *key, char *sig, int siglen, | |
827 | char *data, int datalen) | |
828 | { | |
829 | struct RSAKey *rsa = (struct RSAKey *) key; | |
830 | Bignum in, out; | |
831 | char *p; | |
832 | int slen; | |
833 | int bytes, i, j, ret; | |
834 | unsigned char hash[20]; | |
835 | ||
836 | getstring(&sig, &siglen, &p, &slen); | |
837 | if (!p || slen != 7 || memcmp(p, "ssh-rsa", 7)) { | |
838 | return 0; | |
839 | } | |
840 | in = getmp(&sig, &siglen); | |
841 | out = modpow(in, rsa->exponent, rsa->modulus); | |
842 | freebn(in); | |
843 | ||
844 | ret = 1; | |
845 | ||
846 | bytes = (bignum_bitcount(rsa->modulus)+7) / 8; | |
847 | /* Top (partial) byte should be zero. */ | |
848 | if (bignum_byte(out, bytes - 1) != 0) | |
849 | ret = 0; | |
850 | /* First whole byte should be 1. */ | |
851 | if (bignum_byte(out, bytes - 2) != 1) | |
852 | ret = 0; | |
853 | /* Most of the rest should be FF. */ | |
854 | for (i = bytes - 3; i >= 20 + ASN1_LEN; i--) { | |
855 | if (bignum_byte(out, i) != 0xFF) | |
856 | ret = 0; | |
857 | } | |
858 | /* Then we expect to see the asn1_weird_stuff. */ | |
859 | for (i = 20 + ASN1_LEN - 1, j = 0; i >= 20; i--, j++) { | |
860 | if (bignum_byte(out, i) != asn1_weird_stuff[j]) | |
861 | ret = 0; | |
862 | } | |
863 | /* Finally, we expect to see the SHA-1 hash of the signed data. */ | |
864 | SHA_Simple(data, datalen, hash); | |
865 | for (i = 19, j = 0; i >= 0; i--, j++) { | |
866 | if (bignum_byte(out, i) != hash[j]) | |
867 | ret = 0; | |
868 | } | |
869 | freebn(out); | |
870 | ||
871 | return ret; | |
872 | } | |
873 | ||
874 | static unsigned char *rsa2_sign(void *key, char *data, int datalen, | |
875 | int *siglen) | |
876 | { | |
877 | struct RSAKey *rsa = (struct RSAKey *) key; | |
878 | unsigned char *bytes; | |
879 | int nbytes; | |
880 | unsigned char hash[20]; | |
881 | Bignum in, out; | |
882 | int i, j; | |
883 | ||
884 | SHA_Simple(data, datalen, hash); | |
885 | ||
886 | nbytes = (bignum_bitcount(rsa->modulus) - 1) / 8; | |
887 | assert(1 <= nbytes - 20 - ASN1_LEN); | |
888 | bytes = snewn(nbytes, unsigned char); | |
889 | ||
890 | bytes[0] = 1; | |
891 | for (i = 1; i < nbytes - 20 - ASN1_LEN; i++) | |
892 | bytes[i] = 0xFF; | |
893 | for (i = nbytes - 20 - ASN1_LEN, j = 0; i < nbytes - 20; i++, j++) | |
894 | bytes[i] = asn1_weird_stuff[j]; | |
895 | for (i = nbytes - 20, j = 0; i < nbytes; i++, j++) | |
896 | bytes[i] = hash[j]; | |
897 | ||
898 | in = bignum_from_bytes(bytes, nbytes); | |
899 | sfree(bytes); | |
900 | ||
901 | out = rsa_privkey_op(in, rsa); | |
902 | freebn(in); | |
903 | ||
904 | nbytes = (bignum_bitcount(out) + 7) / 8; | |
905 | bytes = snewn(4 + 7 + 4 + nbytes, unsigned char); | |
906 | PUT_32BIT(bytes, 7); | |
907 | memcpy(bytes + 4, "ssh-rsa", 7); | |
908 | PUT_32BIT(bytes + 4 + 7, nbytes); | |
909 | for (i = 0; i < nbytes; i++) | |
910 | bytes[4 + 7 + 4 + i] = bignum_byte(out, nbytes - 1 - i); | |
911 | freebn(out); | |
912 | ||
913 | *siglen = 4 + 7 + 4 + nbytes; | |
914 | return bytes; | |
915 | } | |
916 | ||
917 | const struct ssh_signkey ssh_rsa = { | |
918 | rsa2_newkey, | |
919 | rsa2_freekey, | |
920 | rsa2_fmtkey, | |
921 | rsa2_public_blob, | |
922 | rsa2_private_blob, | |
923 | rsa2_createkey, | |
924 | rsa2_openssh_createkey, | |
925 | rsa2_openssh_fmtkey, | |
926 | rsa2_pubkey_bits, | |
927 | rsa2_fingerprint, | |
928 | rsa2_verifysig, | |
929 | rsa2_sign, | |
930 | "ssh-rsa", | |
931 | "rsa2" | |
932 | }; | |
933 | ||
934 | void *ssh_rsakex_newkey(char *data, int len) | |
935 | { | |
936 | return rsa2_newkey(data, len); | |
937 | } | |
938 | ||
939 | void ssh_rsakex_freekey(void *key) | |
940 | { | |
941 | rsa2_freekey(key); | |
942 | } | |
943 | ||
944 | int ssh_rsakex_klen(void *key) | |
945 | { | |
946 | struct RSAKey *rsa = (struct RSAKey *) key; | |
947 | ||
948 | return bignum_bitcount(rsa->modulus); | |
949 | } | |
950 | ||
951 | static void oaep_mask(const struct ssh_hash *h, void *seed, int seedlen, | |
952 | void *vdata, int datalen) | |
953 | { | |
954 | unsigned char *data = (unsigned char *)vdata; | |
955 | unsigned count = 0; | |
956 | ||
957 | while (datalen > 0) { | |
958 | int i, max = (datalen > h->hlen ? h->hlen : datalen); | |
959 | void *s; | |
960 | unsigned char counter[4], hash[SSH2_KEX_MAX_HASH_LEN]; | |
961 | ||
962 | assert(h->hlen <= SSH2_KEX_MAX_HASH_LEN); | |
963 | PUT_32BIT(counter, count); | |
964 | s = h->init(); | |
965 | h->bytes(s, seed, seedlen); | |
966 | h->bytes(s, counter, 4); | |
967 | h->final(s, hash); | |
968 | count++; | |
969 | ||
970 | for (i = 0; i < max; i++) | |
971 | data[i] ^= hash[i]; | |
972 | ||
973 | data += max; | |
974 | datalen -= max; | |
975 | } | |
976 | } | |
977 | ||
978 | void ssh_rsakex_encrypt(const struct ssh_hash *h, unsigned char *in, int inlen, | |
979 | unsigned char *out, int outlen, | |
980 | void *key) | |
981 | { | |
982 | Bignum b1, b2; | |
983 | struct RSAKey *rsa = (struct RSAKey *) key; | |
984 | int k, i; | |
985 | char *p; | |
986 | const int HLEN = h->hlen; | |
987 | ||
988 | /* | |
989 | * Here we encrypt using RSAES-OAEP. Essentially this means: | |
990 | * | |
991 | * - we have a SHA-based `mask generation function' which | |
992 | * creates a pseudo-random stream of mask data | |
993 | * deterministically from an input chunk of data. | |
994 | * | |
995 | * - we have a random chunk of data called a seed. | |
996 | * | |
997 | * - we use the seed to generate a mask which we XOR with our | |
998 | * plaintext. | |
999 | * | |
1000 | * - then we use _the masked plaintext_ to generate a mask | |
1001 | * which we XOR with the seed. | |
1002 | * | |
1003 | * - then we concatenate the masked seed and the masked | |
1004 | * plaintext, and RSA-encrypt that lot. | |
1005 | * | |
1006 | * The result is that the data input to the encryption function | |
1007 | * is random-looking and (hopefully) contains no exploitable | |
1008 | * structure such as PKCS1-v1_5 does. | |
1009 | * | |
1010 | * For a precise specification, see RFC 3447, section 7.1.1. | |
1011 | * Some of the variable names below are derived from that, so | |
1012 | * it'd probably help to read it anyway. | |
1013 | */ | |
1014 | ||
1015 | /* k denotes the length in octets of the RSA modulus. */ | |
1016 | k = (7 + bignum_bitcount(rsa->modulus)) / 8; | |
1017 | ||
1018 | /* The length of the input data must be at most k - 2hLen - 2. */ | |
1019 | assert(inlen > 0 && inlen <= k - 2*HLEN - 2); | |
1020 | ||
1021 | /* The length of the output data wants to be precisely k. */ | |
1022 | assert(outlen == k); | |
1023 | ||
1024 | /* | |
1025 | * Now perform EME-OAEP encoding. First set up all the unmasked | |
1026 | * output data. | |
1027 | */ | |
1028 | /* Leading byte zero. */ | |
1029 | out[0] = 0; | |
1030 | /* At position 1, the seed: HLEN bytes of random data. */ | |
1031 | for (i = 0; i < HLEN; i++) | |
1032 | out[i + 1] = random_byte(); | |
1033 | /* At position 1+HLEN, the data block DB, consisting of: */ | |
1034 | /* The hash of the label (we only support an empty label here) */ | |
1035 | h->final(h->init(), out + HLEN + 1); | |
1036 | /* A bunch of zero octets */ | |
1037 | memset(out + 2*HLEN + 1, 0, outlen - (2*HLEN + 1)); | |
1038 | /* A single 1 octet, followed by the input message data. */ | |
1039 | out[outlen - inlen - 1] = 1; | |
1040 | memcpy(out + outlen - inlen, in, inlen); | |
1041 | ||
1042 | /* | |
1043 | * Now use the seed data to mask the block DB. | |
1044 | */ | |
1045 | oaep_mask(h, out+1, HLEN, out+HLEN+1, outlen-HLEN-1); | |
1046 | ||
1047 | /* | |
1048 | * And now use the masked DB to mask the seed itself. | |
1049 | */ | |
1050 | oaep_mask(h, out+HLEN+1, outlen-HLEN-1, out+1, HLEN); | |
1051 | ||
1052 | /* | |
1053 | * Now `out' contains precisely the data we want to | |
1054 | * RSA-encrypt. | |
1055 | */ | |
1056 | b1 = bignum_from_bytes(out, outlen); | |
1057 | b2 = modpow(b1, rsa->exponent, rsa->modulus); | |
1058 | p = (char *)out; | |
1059 | for (i = outlen; i--;) { | |
1060 | *p++ = bignum_byte(b2, i); | |
1061 | } | |
1062 | freebn(b1); | |
1063 | freebn(b2); | |
1064 | ||
1065 | /* | |
1066 | * And we're done. | |
1067 | */ | |
1068 | } | |
1069 | ||
1070 | static const struct ssh_kex ssh_rsa_kex_sha1 = { | |
1071 | "rsa1024-sha1", NULL, KEXTYPE_RSA, NULL, NULL, 0, 0, &ssh_sha1 | |
1072 | }; | |
1073 | ||
1074 | static const struct ssh_kex ssh_rsa_kex_sha256 = { | |
1075 | "rsa2048-sha256", NULL, KEXTYPE_RSA, NULL, NULL, 0, 0, &ssh_sha256 | |
1076 | }; | |
1077 | ||
1078 | static const struct ssh_kex *const rsa_kex_list[] = { | |
1079 | &ssh_rsa_kex_sha256, | |
1080 | &ssh_rsa_kex_sha1 | |
1081 | }; | |
1082 | ||
1083 | const struct ssh_kexes ssh_rsa_kex = { | |
1084 | sizeof(rsa_kex_list) / sizeof(*rsa_kex_list), | |
1085 | rsa_kex_list | |
1086 | }; |