374330e2 |
1 | /* |
8671a580 |
2 | * RSA implementation for PuTTY. |
374330e2 |
3 | */ |
4 | |
374330e2 |
5 | #include <stdio.h> |
6 | #include <stdlib.h> |
7 | #include <string.h> |
65a22376 |
8 | #include <assert.h> |
374330e2 |
9 | |
e5574168 |
10 | #include "ssh.h" |
8365990c |
11 | #include "misc.h" |
374330e2 |
12 | |
0016d70b |
13 | int makekey(unsigned char *data, int len, struct RSAKey *result, |
32874aea |
14 | unsigned char **keystr, int order) |
15 | { |
374330e2 |
16 | unsigned char *p = data; |
0016d70b |
17 | int i, n; |
18 | |
19 | if (len < 4) |
20 | return -1; |
374330e2 |
21 | |
a52f067e |
22 | if (result) { |
32874aea |
23 | result->bits = 0; |
24 | for (i = 0; i < 4; i++) |
25 | result->bits = (result->bits << 8) + *p++; |
a52f067e |
26 | } else |
32874aea |
27 | p += 4; |
374330e2 |
28 | |
0016d70b |
29 | len -= 4; |
30 | |
7cca0d81 |
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 | */ |
374330e2 |
36 | |
0016d70b |
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); |
26d98fc6 |
45 | if (n < 0 || (result && bignum_bitcount(result->modulus) == 0)) return -1; |
a52f067e |
46 | if (result) |
0016d70b |
47 | result->bytes = n - 2; |
32874aea |
48 | if (keystr) |
49 | *keystr = p + 2; |
0016d70b |
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 | } |
374330e2 |
59 | return p - data; |
60 | } |
61 | |
0016d70b |
62 | int makeprivate(unsigned char *data, int len, struct RSAKey *result) |
32874aea |
63 | { |
0016d70b |
64 | return ssh1_read_bignum(data, len, &result->private_exponent); |
7cca0d81 |
65 | } |
66 | |
0016d70b |
67 | int rsaencrypt(unsigned char *data, int length, struct RSAKey *key) |
32874aea |
68 | { |
374330e2 |
69 | Bignum b1, b2; |
3709bfe9 |
70 | int i; |
374330e2 |
71 | unsigned char *p; |
72 | |
0016d70b |
73 | if (key->bytes < length + 4) |
74 | return 0; /* RSA key too short! */ |
75 | |
32874aea |
76 | memmove(data + key->bytes - length, data, length); |
374330e2 |
77 | data[0] = 0; |
78 | data[1] = 2; |
79 | |
32874aea |
80 | for (i = 2; i < key->bytes - length - 1; i++) { |
374330e2 |
81 | do { |
82 | data[i] = random_byte(); |
83 | } while (data[i] == 0); |
84 | } |
32874aea |
85 | data[key->bytes - length - 1] = 0; |
374330e2 |
86 | |
3709bfe9 |
87 | b1 = bignum_from_bytes(data, key->bytes); |
374330e2 |
88 | |
59600f67 |
89 | b2 = modpow(b1, key->exponent, key->modulus); |
374330e2 |
90 | |
374330e2 |
91 | p = data; |
32874aea |
92 | for (i = key->bytes; i--;) { |
93 | *p++ = bignum_byte(b2, i); |
374330e2 |
94 | } |
95 | |
96 | freebn(b1); |
97 | freebn(b2); |
0016d70b |
98 | |
99 | return 1; |
374330e2 |
100 | } |
101 | |
b492c4d7 |
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 | |
8671a580 |
116 | /* |
d737853b |
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. |
8671a580 |
194 | */ |
195 | static Bignum rsa_privkey_op(Bignum input, struct RSAKey *key) |
32874aea |
196 | { |
8671a580 |
197 | Bignum random, random_encrypted, random_inverse; |
198 | Bignum input_blinded, ret_blinded; |
7cca0d81 |
199 | Bignum ret; |
8671a580 |
200 | |
b492c4d7 |
201 | SHA512_State ss; |
202 | unsigned char digest512[64]; |
203 | int digestused = lenof(digest512); |
204 | int hashseq = 0; |
205 | |
8671a580 |
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.) |
b492c4d7 |
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. |
8671a580 |
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--) { |
b492c4d7 |
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 | } |
8671a580 |
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 |
033a3ded |
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. |
8671a580 |
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 |
033a3ded |
292 | * _y^d_, and use the _public_ exponent to compute (y^d)^e = y |
293 | * from it, which is much faster to do. |
8671a580 |
294 | */ |
d737853b |
295 | random_encrypted = crt_modpow(random, key->exponent, |
296 | key->modulus, key->p, key->q, key->iqmp); |
8671a580 |
297 | random_inverse = modinv(random, key->modulus); |
298 | input_blinded = modmul(input, random_encrypted, key->modulus); |
d737853b |
299 | ret_blinded = crt_modpow(input_blinded, key->private_exponent, |
300 | key->modulus, key->p, key->q, key->iqmp); |
8671a580 |
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 | |
7cca0d81 |
309 | return ret; |
310 | } |
311 | |
8671a580 |
312 | Bignum rsadecrypt(Bignum input, struct RSAKey *key) |
313 | { |
314 | return rsa_privkey_op(input, key); |
315 | } |
316 | |
32874aea |
317 | int rsastr_len(struct RSAKey *key) |
318 | { |
374330e2 |
319 | Bignum md, ex; |
3709bfe9 |
320 | int mdlen, exlen; |
374330e2 |
321 | |
322 | md = key->modulus; |
323 | ex = key->exponent; |
32874aea |
324 | mdlen = (bignum_bitcount(md) + 15) / 16; |
325 | exlen = (bignum_bitcount(ex) + 15) / 16; |
326 | return 4 * (mdlen + exlen) + 20; |
374330e2 |
327 | } |
328 | |
32874aea |
329 | void rsastr_fmt(char *str, struct RSAKey *key) |
330 | { |
374330e2 |
331 | Bignum md, ex; |
d5859615 |
332 | int len = 0, i, nibbles; |
333 | static const char hex[] = "0123456789abcdef"; |
374330e2 |
334 | |
335 | md = key->modulus; |
336 | ex = key->exponent; |
337 | |
32874aea |
338 | len += sprintf(str + len, "0x"); |
d5859615 |
339 | |
32874aea |
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]; |
d5859615 |
345 | |
32874aea |
346 | len += sprintf(str + len, ",0x"); |
d5859615 |
347 | |
32874aea |
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]; |
d5859615 |
353 | |
374330e2 |
354 | str[len] = '\0'; |
355 | } |
356 | |
1c2a93c4 |
357 | /* |
358 | * Generate a fingerprint string for the key. Compatible with the |
359 | * OpenSSH fingerprint code. |
360 | */ |
32874aea |
361 | void rsa_fingerprint(char *str, int len, struct RSAKey *key) |
362 | { |
1c2a93c4 |
363 | struct MD5Context md5c; |
364 | unsigned char digest[16]; |
32874aea |
365 | char buffer[16 * 3 + 40]; |
1c2a93c4 |
366 | int numlen, slen, i; |
367 | |
368 | MD5Init(&md5c); |
369 | numlen = ssh1_bignum_length(key->modulus) - 2; |
32874aea |
370 | for (i = numlen; i--;) { |
371 | unsigned char c = bignum_byte(key->modulus, i); |
372 | MD5Update(&md5c, &c, 1); |
1c2a93c4 |
373 | } |
374 | numlen = ssh1_bignum_length(key->exponent) - 2; |
32874aea |
375 | for (i = numlen; i--;) { |
376 | unsigned char c = bignum_byte(key->exponent, i); |
377 | MD5Update(&md5c, &c, 1); |
1c2a93c4 |
378 | } |
379 | MD5Final(digest, &md5c); |
380 | |
ddecd643 |
381 | sprintf(buffer, "%d ", bignum_bitcount(key->modulus)); |
1c2a93c4 |
382 | for (i = 0; i < 16; i++) |
32874aea |
383 | sprintf(buffer + strlen(buffer), "%s%02x", i ? ":" : "", |
384 | digest[i]); |
385 | strncpy(str, buffer, len); |
386 | str[len - 1] = '\0'; |
1c2a93c4 |
387 | slen = strlen(str); |
32874aea |
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'; |
1c2a93c4 |
392 | } |
393 | } |
394 | |
98f022f5 |
395 | /* |
396 | * Verify that the public data in an RSA key matches the private |
60fe6ff7 |
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. |
98f022f5 |
399 | */ |
32874aea |
400 | int rsa_verify(struct RSAKey *key) |
401 | { |
60fe6ff7 |
402 | Bignum n, ed, pm1, qm1; |
98f022f5 |
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 | |
60fe6ff7 |
412 | /* e * d must be congruent to 1, modulo (p-1) and modulo (q-1). */ |
98f022f5 |
413 | pm1 = copybn(key->p); |
414 | decbn(pm1); |
60fe6ff7 |
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 | |
98f022f5 |
421 | qm1 = copybn(key->q); |
422 | decbn(qm1); |
60fe6ff7 |
423 | ed = modmul(key->exponent, key->private_exponent, qm1); |
98f022f5 |
424 | cmp = bignum_cmp(ed, One); |
425 | sfree(ed); |
426 | if (cmp != 0) |
427 | return 0; |
014970c8 |
428 | |
60fe6ff7 |
429 | /* |
430 | * Ensure p > q. |
f5bcbcc2 |
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. |
60fe6ff7 |
436 | */ |
f5bcbcc2 |
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 | } |
60fe6ff7 |
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) |
32874aea |
453 | return 0; |
60fe6ff7 |
454 | |
014970c8 |
455 | return 1; |
98f022f5 |
456 | } |
457 | |
3f2d010c |
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); |
3d88e64d |
466 | ret = snewn(length, unsigned char); |
3f2d010c |
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. */ |
0016d70b |
478 | int rsa_public_blob_len(void *data, int maxlen) |
3f2d010c |
479 | { |
480 | unsigned char *p = (unsigned char *)data; |
0016d70b |
481 | int n; |
3f2d010c |
482 | |
0016d70b |
483 | if (maxlen < 4) |
484 | return -1; |
3f2d010c |
485 | p += 4; /* length word */ |
0016d70b |
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; |
3f2d010c |
497 | |
498 | return p - (unsigned char *)data; |
499 | } |
500 | |
32874aea |
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); |
f5bcbcc2 |
509 | if (key->p) |
510 | freebn(key->p); |
511 | if (key->q) |
512 | freebn(key->q); |
513 | if (key->iqmp) |
514 | freebn(key->iqmp); |
32874aea |
515 | if (key->comment) |
516 | sfree(key->comment); |
5c58ad2d |
517 | } |
85cc02bb |
518 | |
519 | /* ---------------------------------------------------------------------- |
520 | * Implementation of the ssh-rsa signing key type. |
521 | */ |
522 | |
32874aea |
523 | static void getstring(char **data, int *datalen, char **p, int *length) |
524 | { |
85cc02bb |
525 | *p = NULL; |
526 | if (*datalen < 4) |
32874aea |
527 | return; |
85cc02bb |
528 | *length = GET_32BIT(*data); |
32874aea |
529 | *datalen -= 4; |
530 | *data += 4; |
85cc02bb |
531 | if (*datalen < *length) |
32874aea |
532 | return; |
85cc02bb |
533 | *p = *data; |
32874aea |
534 | *data += *length; |
535 | *datalen -= *length; |
85cc02bb |
536 | } |
32874aea |
537 | static Bignum getmp(char **data, int *datalen) |
538 | { |
85cc02bb |
539 | char *p; |
540 | int length; |
541 | Bignum b; |
542 | |
543 | getstring(data, datalen, &p, &length); |
544 | if (!p) |
32874aea |
545 | return NULL; |
9bf430c9 |
546 | b = bignum_from_bytes((unsigned char *)p, length); |
85cc02bb |
547 | return b; |
548 | } |
549 | |
32874aea |
550 | static void *rsa2_newkey(char *data, int len) |
551 | { |
85cc02bb |
552 | char *p; |
553 | int slen; |
554 | struct RSAKey *rsa; |
555 | |
3d88e64d |
556 | rsa = snew(struct RSAKey); |
32874aea |
557 | if (!rsa) |
558 | return NULL; |
85cc02bb |
559 | getstring(&data, &len, &p, &slen); |
560 | |
45cebe79 |
561 | if (!p || slen != 7 || memcmp(p, "ssh-rsa", 7)) { |
85cc02bb |
562 | sfree(rsa); |
563 | return NULL; |
564 | } |
565 | rsa->exponent = getmp(&data, &len); |
566 | rsa->modulus = getmp(&data, &len); |
567 | rsa->private_exponent = NULL; |
bc7cc96f |
568 | rsa->p = rsa->q = rsa->iqmp = NULL; |
85cc02bb |
569 | rsa->comment = NULL; |
570 | |
571 | return rsa; |
572 | } |
573 | |
32874aea |
574 | static void rsa2_freekey(void *key) |
575 | { |
576 | struct RSAKey *rsa = (struct RSAKey *) key; |
85cc02bb |
577 | freersakey(rsa); |
578 | sfree(rsa); |
579 | } |
580 | |
32874aea |
581 | static char *rsa2_fmtkey(void *key) |
582 | { |
583 | struct RSAKey *rsa = (struct RSAKey *) key; |
85cc02bb |
584 | char *p; |
585 | int len; |
32874aea |
586 | |
85cc02bb |
587 | len = rsastr_len(rsa); |
3d88e64d |
588 | p = snewn(len, char); |
32874aea |
589 | rsastr_fmt(p, rsa); |
85cc02bb |
590 | return p; |
591 | } |
592 | |
32874aea |
593 | static unsigned char *rsa2_public_blob(void *key, int *len) |
594 | { |
595 | struct RSAKey *rsa = (struct RSAKey *) key; |
65a22376 |
596 | int elen, mlen, bloblen; |
597 | int i; |
598 | unsigned char *blob, *p; |
599 | |
32874aea |
600 | elen = (bignum_bitcount(rsa->exponent) + 8) / 8; |
601 | mlen = (bignum_bitcount(rsa->modulus) + 8) / 8; |
65a22376 |
602 | |
603 | /* |
604 | * string "ssh-rsa", mpint exp, mpint mod. Total 19+elen+mlen. |
605 | * (three length fields, 12+7=19). |
606 | */ |
32874aea |
607 | bloblen = 19 + elen + mlen; |
3d88e64d |
608 | blob = snewn(bloblen, unsigned char); |
65a22376 |
609 | p = blob; |
32874aea |
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); |
65a22376 |
622 | assert(p == blob + bloblen); |
623 | *len = bloblen; |
624 | return blob; |
625 | } |
626 | |
32874aea |
627 | static unsigned char *rsa2_private_blob(void *key, int *len) |
628 | { |
629 | struct RSAKey *rsa = (struct RSAKey *) key; |
65a22376 |
630 | int dlen, plen, qlen, ulen, bloblen; |
631 | int i; |
632 | unsigned char *blob, *p; |
633 | |
32874aea |
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; |
65a22376 |
638 | |
639 | /* |
640 | * mpint private_exp, mpint p, mpint q, mpint iqmp. Total 16 + |
641 | * sum of lengths. |
642 | */ |
32874aea |
643 | bloblen = 16 + dlen + plen + qlen + ulen; |
3d88e64d |
644 | blob = snewn(bloblen, unsigned char); |
65a22376 |
645 | p = blob; |
32874aea |
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); |
65a22376 |
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, |
32874aea |
668 | unsigned char *priv_blob, int priv_len) |
669 | { |
65a22376 |
670 | struct RSAKey *rsa; |
32874aea |
671 | char *pb = (char *) priv_blob; |
672 | |
673 | rsa = rsa2_newkey((char *) pub_blob, pub_len); |
65a22376 |
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 | |
98f022f5 |
679 | if (!rsa_verify(rsa)) { |
680 | rsa2_freekey(rsa); |
681 | return NULL; |
682 | } |
683 | |
65a22376 |
684 | return rsa; |
685 | } |
686 | |
32874aea |
687 | static void *rsa2_openssh_createkey(unsigned char **blob, int *len) |
688 | { |
689 | char **b = (char **) blob; |
45cebe79 |
690 | struct RSAKey *rsa; |
45cebe79 |
691 | |
3d88e64d |
692 | rsa = snew(struct RSAKey); |
32874aea |
693 | if (!rsa) |
694 | return NULL; |
45cebe79 |
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 | |
32874aea |
719 | static int rsa2_openssh_fmtkey(void *key, unsigned char *blob, int len) |
720 | { |
721 | struct RSAKey *rsa = (struct RSAKey *) key; |
ddecd643 |
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) + |
32874aea |
729 | ssh2_bignum_length(rsa->p) + ssh2_bignum_length(rsa->q); |
ddecd643 |
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 | |
47a6b94c |
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 | |
32874aea |
760 | static char *rsa2_fingerprint(void *key) |
761 | { |
762 | struct RSAKey *rsa = (struct RSAKey *) key; |
85cc02bb |
763 | struct MD5Context md5c; |
764 | unsigned char digest[16], lenbuf[4]; |
32874aea |
765 | char buffer[16 * 3 + 40]; |
85cc02bb |
766 | char *ret; |
767 | int numlen, i; |
768 | |
769 | MD5Init(&md5c); |
9bf430c9 |
770 | MD5Update(&md5c, (unsigned char *)"\0\0\0\7ssh-rsa", 11); |
85cc02bb |
771 | |
772 | #define ADD_BIGNUM(bignum) \ |
ddecd643 |
773 | numlen = (bignum_bitcount(bignum)+8)/8; \ |
85cc02bb |
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 | |
ddecd643 |
785 | sprintf(buffer, "ssh-rsa %d ", bignum_bitcount(rsa->modulus)); |
85cc02bb |
786 | for (i = 0; i < 16; i++) |
32874aea |
787 | sprintf(buffer + strlen(buffer), "%s%02x", i ? ":" : "", |
788 | digest[i]); |
3d88e64d |
789 | ret = snewn(strlen(buffer) + 1, char); |
85cc02bb |
790 | if (ret) |
32874aea |
791 | strcpy(ret, buffer); |
85cc02bb |
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 |
96a73db9 |
798 | * value. The meaning of it is: |
85cc02bb |
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 |
96a73db9 |
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) |
85cc02bb |
807 | * 05 00 -- NULL |
808 | * 04 14 -- a primitive OCTET STRING of length 0x14 |
809 | * [0x14 bytes of hash data follows] |
96a73db9 |
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 } |
85cc02bb |
818 | */ |
b5864f2c |
819 | static const unsigned char asn1_weird_stuff[] = { |
32874aea |
820 | 0x00, 0x30, 0x21, 0x30, 0x09, 0x06, 0x05, 0x2B, |
821 | 0x0E, 0x03, 0x02, 0x1A, 0x05, 0x00, 0x04, 0x14, |
85cc02bb |
822 | }; |
823 | |
d8770b12 |
824 | #define ASN1_LEN ( (int) sizeof(asn1_weird_stuff) ) |
825 | |
85cc02bb |
826 | static int rsa2_verifysig(void *key, char *sig, int siglen, |
32874aea |
827 | char *data, int datalen) |
828 | { |
829 | struct RSAKey *rsa = (struct RSAKey *) key; |
85cc02bb |
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)) { |
32874aea |
838 | return 0; |
85cc02bb |
839 | } |
840 | in = getmp(&sig, &siglen); |
841 | out = modpow(in, rsa->exponent, rsa->modulus); |
842 | freebn(in); |
843 | |
844 | ret = 1; |
845 | |
7bd33644 |
846 | bytes = (bignum_bitcount(rsa->modulus)+7) / 8; |
85cc02bb |
847 | /* Top (partial) byte should be zero. */ |
32874aea |
848 | if (bignum_byte(out, bytes - 1) != 0) |
849 | ret = 0; |
85cc02bb |
850 | /* First whole byte should be 1. */ |
32874aea |
851 | if (bignum_byte(out, bytes - 2) != 1) |
852 | ret = 0; |
85cc02bb |
853 | /* Most of the rest should be FF. */ |
32874aea |
854 | for (i = bytes - 3; i >= 20 + ASN1_LEN; i--) { |
855 | if (bignum_byte(out, i) != 0xFF) |
856 | ret = 0; |
85cc02bb |
857 | } |
858 | /* Then we expect to see the asn1_weird_stuff. */ |
32874aea |
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; |
85cc02bb |
862 | } |
863 | /* Finally, we expect to see the SHA-1 hash of the signed data. */ |
864 | SHA_Simple(data, datalen, hash); |
32874aea |
865 | for (i = 19, j = 0; i >= 0; i--, j++) { |
866 | if (bignum_byte(out, i) != hash[j]) |
867 | ret = 0; |
85cc02bb |
868 | } |
679539d7 |
869 | freebn(out); |
85cc02bb |
870 | |
871 | return ret; |
872 | } |
873 | |
164feb13 |
874 | static unsigned char *rsa2_sign(void *key, char *data, int datalen, |
875 | int *siglen) |
32874aea |
876 | { |
877 | struct RSAKey *rsa = (struct RSAKey *) key; |
65a22376 |
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 | |
32874aea |
886 | nbytes = (bignum_bitcount(rsa->modulus) - 1) / 8; |
e99cd73f |
887 | assert(1 <= nbytes - 20 - ASN1_LEN); |
3d88e64d |
888 | bytes = snewn(nbytes, unsigned char); |
65a22376 |
889 | |
890 | bytes[0] = 1; |
32874aea |
891 | for (i = 1; i < nbytes - 20 - ASN1_LEN; i++) |
65a22376 |
892 | bytes[i] = 0xFF; |
32874aea |
893 | for (i = nbytes - 20 - ASN1_LEN, j = 0; i < nbytes - 20; i++, j++) |
65a22376 |
894 | bytes[i] = asn1_weird_stuff[j]; |
32874aea |
895 | for (i = nbytes - 20, j = 0; i < nbytes; i++, j++) |
65a22376 |
896 | bytes[i] = hash[j]; |
897 | |
898 | in = bignum_from_bytes(bytes, nbytes); |
899 | sfree(bytes); |
900 | |
8671a580 |
901 | out = rsa_privkey_op(in, rsa); |
65a22376 |
902 | freebn(in); |
903 | |
32874aea |
904 | nbytes = (bignum_bitcount(out) + 7) / 8; |
3d88e64d |
905 | bytes = snewn(4 + 7 + 4 + nbytes, unsigned char); |
65a22376 |
906 | PUT_32BIT(bytes, 7); |
32874aea |
907 | memcpy(bytes + 4, "ssh-rsa", 7); |
908 | PUT_32BIT(bytes + 4 + 7, nbytes); |
65a22376 |
909 | for (i = 0; i < nbytes; i++) |
32874aea |
910 | bytes[4 + 7 + 4 + i] = bignum_byte(out, nbytes - 1 - i); |
65a22376 |
911 | freebn(out); |
912 | |
32874aea |
913 | *siglen = 4 + 7 + 4 + nbytes; |
65a22376 |
914 | return bytes; |
85cc02bb |
915 | } |
916 | |
65a22376 |
917 | const struct ssh_signkey ssh_rsa = { |
85cc02bb |
918 | rsa2_newkey, |
919 | rsa2_freekey, |
920 | rsa2_fmtkey, |
65a22376 |
921 | rsa2_public_blob, |
922 | rsa2_private_blob, |
923 | rsa2_createkey, |
45cebe79 |
924 | rsa2_openssh_createkey, |
ddecd643 |
925 | rsa2_openssh_fmtkey, |
47a6b94c |
926 | rsa2_pubkey_bits, |
85cc02bb |
927 | rsa2_fingerprint, |
928 | rsa2_verifysig, |
929 | rsa2_sign, |
930 | "ssh-rsa", |
931 | "rsa2" |
932 | }; |
fae1a71b |
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; |
143ec28a |
960 | unsigned char counter[4], hash[SSH2_KEX_MAX_HASH_LEN]; |
fae1a71b |
961 | |
143ec28a |
962 | assert(h->hlen <= SSH2_KEX_MAX_HASH_LEN); |
fae1a71b |
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); |
7108a872 |
1058 | p = (char *)out; |
fae1a71b |
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 | }; |