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 | /* |
117 | * This function is a wrapper on modpow(). It has the same effect |
118 | * as modpow(), but employs RSA blinding to protect against timing |
119 | * attacks. |
120 | */ |
121 | static Bignum rsa_privkey_op(Bignum input, struct RSAKey *key) |
32874aea |
122 | { |
8671a580 |
123 | Bignum random, random_encrypted, random_inverse; |
124 | Bignum input_blinded, ret_blinded; |
7cca0d81 |
125 | Bignum ret; |
8671a580 |
126 | |
b492c4d7 |
127 | SHA512_State ss; |
128 | unsigned char digest512[64]; |
129 | int digestused = lenof(digest512); |
130 | int hashseq = 0; |
131 | |
8671a580 |
132 | /* |
133 | * Start by inventing a random number chosen uniformly from the |
134 | * range 2..modulus-1. (We do this by preparing a random number |
135 | * of the right length and retrying if it's greater than the |
136 | * modulus, to prevent any potential Bleichenbacher-like |
137 | * attacks making use of the uneven distribution within the |
138 | * range that would arise from just reducing our number mod n. |
139 | * There are timing implications to the potential retries, of |
140 | * course, but all they tell you is the modulus, which you |
141 | * already knew.) |
b492c4d7 |
142 | * |
143 | * To preserve determinism and avoid Pageant needing to share |
144 | * the random number pool, we actually generate this `random' |
145 | * number by hashing stuff with the private key. |
8671a580 |
146 | */ |
147 | while (1) { |
148 | int bits, byte, bitsleft, v; |
149 | random = copybn(key->modulus); |
150 | /* |
151 | * Find the topmost set bit. (This function will return its |
152 | * index plus one.) Then we'll set all bits from that one |
153 | * downwards randomly. |
154 | */ |
155 | bits = bignum_bitcount(random); |
156 | byte = 0; |
157 | bitsleft = 0; |
158 | while (bits--) { |
b492c4d7 |
159 | if (bitsleft <= 0) { |
160 | bitsleft = 8; |
161 | /* |
162 | * Conceptually the following few lines are equivalent to |
163 | * byte = random_byte(); |
164 | */ |
165 | if (digestused >= lenof(digest512)) { |
166 | unsigned char seqbuf[4]; |
167 | PUT_32BIT(seqbuf, hashseq); |
168 | SHA512_Init(&ss); |
169 | SHA512_Bytes(&ss, "RSA deterministic blinding", 26); |
170 | SHA512_Bytes(&ss, seqbuf, sizeof(seqbuf)); |
171 | sha512_mpint(&ss, key->private_exponent); |
172 | SHA512_Final(&ss, digest512); |
173 | hashseq++; |
174 | |
175 | /* |
176 | * Now hash that digest plus the signature |
177 | * input. |
178 | */ |
179 | SHA512_Init(&ss); |
180 | SHA512_Bytes(&ss, digest512, sizeof(digest512)); |
181 | sha512_mpint(&ss, input); |
182 | SHA512_Final(&ss, digest512); |
183 | |
184 | digestused = 0; |
185 | } |
186 | byte = digest512[digestused++]; |
187 | } |
8671a580 |
188 | v = byte & 1; |
189 | byte >>= 1; |
190 | bitsleft--; |
191 | bignum_set_bit(random, bits, v); |
192 | } |
193 | |
194 | /* |
195 | * Now check that this number is strictly greater than |
196 | * zero, and strictly less than modulus. |
197 | */ |
198 | if (bignum_cmp(random, Zero) <= 0 || |
199 | bignum_cmp(random, key->modulus) >= 0) { |
200 | freebn(random); |
201 | continue; |
202 | } else { |
203 | break; |
204 | } |
205 | } |
206 | |
207 | /* |
208 | * RSA blinding relies on the fact that (xy)^d mod n is equal |
209 | * to (x^d mod n) * (y^d mod n) mod n. We invent a random pair |
033a3ded |
210 | * y and y^d; then we multiply x by y, raise to the power d mod |
211 | * n as usual, and divide by y^d to recover x^d. Thus an |
212 | * attacker can't correlate the timing of the modpow with the |
213 | * input, because they don't know anything about the number |
214 | * that was input to the actual modpow. |
8671a580 |
215 | * |
216 | * The clever bit is that we don't have to do a huge modpow to |
217 | * get y and y^d; we will use the number we just invented as |
033a3ded |
218 | * _y^d_, and use the _public_ exponent to compute (y^d)^e = y |
219 | * from it, which is much faster to do. |
8671a580 |
220 | */ |
221 | random_encrypted = modpow(random, key->exponent, key->modulus); |
222 | random_inverse = modinv(random, key->modulus); |
223 | input_blinded = modmul(input, random_encrypted, key->modulus); |
224 | ret_blinded = modpow(input_blinded, key->private_exponent, key->modulus); |
225 | ret = modmul(ret_blinded, random_inverse, key->modulus); |
226 | |
227 | freebn(ret_blinded); |
228 | freebn(input_blinded); |
229 | freebn(random_inverse); |
230 | freebn(random_encrypted); |
231 | freebn(random); |
232 | |
7cca0d81 |
233 | return ret; |
234 | } |
235 | |
8671a580 |
236 | Bignum rsadecrypt(Bignum input, struct RSAKey *key) |
237 | { |
238 | return rsa_privkey_op(input, key); |
239 | } |
240 | |
32874aea |
241 | int rsastr_len(struct RSAKey *key) |
242 | { |
374330e2 |
243 | Bignum md, ex; |
3709bfe9 |
244 | int mdlen, exlen; |
374330e2 |
245 | |
246 | md = key->modulus; |
247 | ex = key->exponent; |
32874aea |
248 | mdlen = (bignum_bitcount(md) + 15) / 16; |
249 | exlen = (bignum_bitcount(ex) + 15) / 16; |
250 | return 4 * (mdlen + exlen) + 20; |
374330e2 |
251 | } |
252 | |
32874aea |
253 | void rsastr_fmt(char *str, struct RSAKey *key) |
254 | { |
374330e2 |
255 | Bignum md, ex; |
d5859615 |
256 | int len = 0, i, nibbles; |
257 | static const char hex[] = "0123456789abcdef"; |
374330e2 |
258 | |
259 | md = key->modulus; |
260 | ex = key->exponent; |
261 | |
32874aea |
262 | len += sprintf(str + len, "0x"); |
d5859615 |
263 | |
32874aea |
264 | nibbles = (3 + bignum_bitcount(ex)) / 4; |
265 | if (nibbles < 1) |
266 | nibbles = 1; |
267 | for (i = nibbles; i--;) |
268 | str[len++] = hex[(bignum_byte(ex, i / 2) >> (4 * (i % 2))) & 0xF]; |
d5859615 |
269 | |
32874aea |
270 | len += sprintf(str + len, ",0x"); |
d5859615 |
271 | |
32874aea |
272 | nibbles = (3 + bignum_bitcount(md)) / 4; |
273 | if (nibbles < 1) |
274 | nibbles = 1; |
275 | for (i = nibbles; i--;) |
276 | str[len++] = hex[(bignum_byte(md, i / 2) >> (4 * (i % 2))) & 0xF]; |
d5859615 |
277 | |
374330e2 |
278 | str[len] = '\0'; |
279 | } |
280 | |
1c2a93c4 |
281 | /* |
282 | * Generate a fingerprint string for the key. Compatible with the |
283 | * OpenSSH fingerprint code. |
284 | */ |
32874aea |
285 | void rsa_fingerprint(char *str, int len, struct RSAKey *key) |
286 | { |
1c2a93c4 |
287 | struct MD5Context md5c; |
288 | unsigned char digest[16]; |
32874aea |
289 | char buffer[16 * 3 + 40]; |
1c2a93c4 |
290 | int numlen, slen, i; |
291 | |
292 | MD5Init(&md5c); |
293 | numlen = ssh1_bignum_length(key->modulus) - 2; |
32874aea |
294 | for (i = numlen; i--;) { |
295 | unsigned char c = bignum_byte(key->modulus, i); |
296 | MD5Update(&md5c, &c, 1); |
1c2a93c4 |
297 | } |
298 | numlen = ssh1_bignum_length(key->exponent) - 2; |
32874aea |
299 | for (i = numlen; i--;) { |
300 | unsigned char c = bignum_byte(key->exponent, i); |
301 | MD5Update(&md5c, &c, 1); |
1c2a93c4 |
302 | } |
303 | MD5Final(digest, &md5c); |
304 | |
ddecd643 |
305 | sprintf(buffer, "%d ", bignum_bitcount(key->modulus)); |
1c2a93c4 |
306 | for (i = 0; i < 16; i++) |
32874aea |
307 | sprintf(buffer + strlen(buffer), "%s%02x", i ? ":" : "", |
308 | digest[i]); |
309 | strncpy(str, buffer, len); |
310 | str[len - 1] = '\0'; |
1c2a93c4 |
311 | slen = strlen(str); |
32874aea |
312 | if (key->comment && slen < len - 1) { |
313 | str[slen] = ' '; |
314 | strncpy(str + slen + 1, key->comment, len - slen - 1); |
315 | str[len - 1] = '\0'; |
1c2a93c4 |
316 | } |
317 | } |
318 | |
98f022f5 |
319 | /* |
320 | * Verify that the public data in an RSA key matches the private |
60fe6ff7 |
321 | * data. We also check the private data itself: we ensure that p > |
322 | * q and that iqmp really is the inverse of q mod p. |
98f022f5 |
323 | */ |
32874aea |
324 | int rsa_verify(struct RSAKey *key) |
325 | { |
60fe6ff7 |
326 | Bignum n, ed, pm1, qm1; |
98f022f5 |
327 | int cmp; |
328 | |
329 | /* n must equal pq. */ |
330 | n = bigmul(key->p, key->q); |
331 | cmp = bignum_cmp(n, key->modulus); |
332 | freebn(n); |
333 | if (cmp != 0) |
334 | return 0; |
335 | |
60fe6ff7 |
336 | /* e * d must be congruent to 1, modulo (p-1) and modulo (q-1). */ |
98f022f5 |
337 | pm1 = copybn(key->p); |
338 | decbn(pm1); |
60fe6ff7 |
339 | ed = modmul(key->exponent, key->private_exponent, pm1); |
340 | cmp = bignum_cmp(ed, One); |
341 | sfree(ed); |
342 | if (cmp != 0) |
343 | return 0; |
344 | |
98f022f5 |
345 | qm1 = copybn(key->q); |
346 | decbn(qm1); |
60fe6ff7 |
347 | ed = modmul(key->exponent, key->private_exponent, qm1); |
98f022f5 |
348 | cmp = bignum_cmp(ed, One); |
349 | sfree(ed); |
350 | if (cmp != 0) |
351 | return 0; |
014970c8 |
352 | |
60fe6ff7 |
353 | /* |
354 | * Ensure p > q. |
f5bcbcc2 |
355 | * |
356 | * I have seen key blobs in the wild which were generated with |
357 | * p < q, so instead of rejecting the key in this case we |
358 | * should instead flip them round into the canonical order of |
359 | * p > q. This also involves regenerating iqmp. |
60fe6ff7 |
360 | */ |
f5bcbcc2 |
361 | if (bignum_cmp(key->p, key->q) <= 0) { |
362 | Bignum tmp = key->p; |
363 | key->p = key->q; |
364 | key->q = tmp; |
365 | |
366 | freebn(key->iqmp); |
367 | key->iqmp = modinv(key->q, key->p); |
368 | } |
60fe6ff7 |
369 | |
370 | /* |
371 | * Ensure iqmp * q is congruent to 1, modulo p. |
372 | */ |
373 | n = modmul(key->iqmp, key->q, key->p); |
374 | cmp = bignum_cmp(n, One); |
375 | sfree(n); |
376 | if (cmp != 0) |
32874aea |
377 | return 0; |
60fe6ff7 |
378 | |
014970c8 |
379 | return 1; |
98f022f5 |
380 | } |
381 | |
3f2d010c |
382 | /* Public key blob as used by Pageant: exponent before modulus. */ |
383 | unsigned char *rsa_public_blob(struct RSAKey *key, int *len) |
384 | { |
385 | int length, pos; |
386 | unsigned char *ret; |
387 | |
388 | length = (ssh1_bignum_length(key->modulus) + |
389 | ssh1_bignum_length(key->exponent) + 4); |
3d88e64d |
390 | ret = snewn(length, unsigned char); |
3f2d010c |
391 | |
392 | PUT_32BIT(ret, bignum_bitcount(key->modulus)); |
393 | pos = 4; |
394 | pos += ssh1_write_bignum(ret + pos, key->exponent); |
395 | pos += ssh1_write_bignum(ret + pos, key->modulus); |
396 | |
397 | *len = length; |
398 | return ret; |
399 | } |
400 | |
401 | /* Given a public blob, determine its length. */ |
0016d70b |
402 | int rsa_public_blob_len(void *data, int maxlen) |
3f2d010c |
403 | { |
404 | unsigned char *p = (unsigned char *)data; |
0016d70b |
405 | int n; |
3f2d010c |
406 | |
0016d70b |
407 | if (maxlen < 4) |
408 | return -1; |
3f2d010c |
409 | p += 4; /* length word */ |
0016d70b |
410 | maxlen -= 4; |
411 | |
412 | n = ssh1_read_bignum(p, maxlen, NULL); /* exponent */ |
413 | if (n < 0) |
414 | return -1; |
415 | p += n; |
416 | |
417 | n = ssh1_read_bignum(p, maxlen, NULL); /* modulus */ |
418 | if (n < 0) |
419 | return -1; |
420 | p += n; |
3f2d010c |
421 | |
422 | return p - (unsigned char *)data; |
423 | } |
424 | |
32874aea |
425 | void freersakey(struct RSAKey *key) |
426 | { |
427 | if (key->modulus) |
428 | freebn(key->modulus); |
429 | if (key->exponent) |
430 | freebn(key->exponent); |
431 | if (key->private_exponent) |
432 | freebn(key->private_exponent); |
f5bcbcc2 |
433 | if (key->p) |
434 | freebn(key->p); |
435 | if (key->q) |
436 | freebn(key->q); |
437 | if (key->iqmp) |
438 | freebn(key->iqmp); |
32874aea |
439 | if (key->comment) |
440 | sfree(key->comment); |
5c58ad2d |
441 | } |
85cc02bb |
442 | |
443 | /* ---------------------------------------------------------------------- |
444 | * Implementation of the ssh-rsa signing key type. |
445 | */ |
446 | |
32874aea |
447 | static void getstring(char **data, int *datalen, char **p, int *length) |
448 | { |
85cc02bb |
449 | *p = NULL; |
450 | if (*datalen < 4) |
32874aea |
451 | return; |
85cc02bb |
452 | *length = GET_32BIT(*data); |
32874aea |
453 | *datalen -= 4; |
454 | *data += 4; |
85cc02bb |
455 | if (*datalen < *length) |
32874aea |
456 | return; |
85cc02bb |
457 | *p = *data; |
32874aea |
458 | *data += *length; |
459 | *datalen -= *length; |
85cc02bb |
460 | } |
32874aea |
461 | static Bignum getmp(char **data, int *datalen) |
462 | { |
85cc02bb |
463 | char *p; |
464 | int length; |
465 | Bignum b; |
466 | |
467 | getstring(data, datalen, &p, &length); |
468 | if (!p) |
32874aea |
469 | return NULL; |
9bf430c9 |
470 | b = bignum_from_bytes((unsigned char *)p, length); |
85cc02bb |
471 | return b; |
472 | } |
473 | |
32874aea |
474 | static void *rsa2_newkey(char *data, int len) |
475 | { |
85cc02bb |
476 | char *p; |
477 | int slen; |
478 | struct RSAKey *rsa; |
479 | |
3d88e64d |
480 | rsa = snew(struct RSAKey); |
32874aea |
481 | if (!rsa) |
482 | return NULL; |
85cc02bb |
483 | getstring(&data, &len, &p, &slen); |
484 | |
45cebe79 |
485 | if (!p || slen != 7 || memcmp(p, "ssh-rsa", 7)) { |
85cc02bb |
486 | sfree(rsa); |
487 | return NULL; |
488 | } |
489 | rsa->exponent = getmp(&data, &len); |
490 | rsa->modulus = getmp(&data, &len); |
491 | rsa->private_exponent = NULL; |
bc7cc96f |
492 | rsa->p = rsa->q = rsa->iqmp = NULL; |
85cc02bb |
493 | rsa->comment = NULL; |
494 | |
495 | return rsa; |
496 | } |
497 | |
32874aea |
498 | static void rsa2_freekey(void *key) |
499 | { |
500 | struct RSAKey *rsa = (struct RSAKey *) key; |
85cc02bb |
501 | freersakey(rsa); |
502 | sfree(rsa); |
503 | } |
504 | |
32874aea |
505 | static char *rsa2_fmtkey(void *key) |
506 | { |
507 | struct RSAKey *rsa = (struct RSAKey *) key; |
85cc02bb |
508 | char *p; |
509 | int len; |
32874aea |
510 | |
85cc02bb |
511 | len = rsastr_len(rsa); |
3d88e64d |
512 | p = snewn(len, char); |
32874aea |
513 | rsastr_fmt(p, rsa); |
85cc02bb |
514 | return p; |
515 | } |
516 | |
32874aea |
517 | static unsigned char *rsa2_public_blob(void *key, int *len) |
518 | { |
519 | struct RSAKey *rsa = (struct RSAKey *) key; |
65a22376 |
520 | int elen, mlen, bloblen; |
521 | int i; |
522 | unsigned char *blob, *p; |
523 | |
32874aea |
524 | elen = (bignum_bitcount(rsa->exponent) + 8) / 8; |
525 | mlen = (bignum_bitcount(rsa->modulus) + 8) / 8; |
65a22376 |
526 | |
527 | /* |
528 | * string "ssh-rsa", mpint exp, mpint mod. Total 19+elen+mlen. |
529 | * (three length fields, 12+7=19). |
530 | */ |
32874aea |
531 | bloblen = 19 + elen + mlen; |
3d88e64d |
532 | blob = snewn(bloblen, unsigned char); |
65a22376 |
533 | p = blob; |
32874aea |
534 | PUT_32BIT(p, 7); |
535 | p += 4; |
536 | memcpy(p, "ssh-rsa", 7); |
537 | p += 7; |
538 | PUT_32BIT(p, elen); |
539 | p += 4; |
540 | for (i = elen; i--;) |
541 | *p++ = bignum_byte(rsa->exponent, i); |
542 | PUT_32BIT(p, mlen); |
543 | p += 4; |
544 | for (i = mlen; i--;) |
545 | *p++ = bignum_byte(rsa->modulus, i); |
65a22376 |
546 | assert(p == blob + bloblen); |
547 | *len = bloblen; |
548 | return blob; |
549 | } |
550 | |
32874aea |
551 | static unsigned char *rsa2_private_blob(void *key, int *len) |
552 | { |
553 | struct RSAKey *rsa = (struct RSAKey *) key; |
65a22376 |
554 | int dlen, plen, qlen, ulen, bloblen; |
555 | int i; |
556 | unsigned char *blob, *p; |
557 | |
32874aea |
558 | dlen = (bignum_bitcount(rsa->private_exponent) + 8) / 8; |
559 | plen = (bignum_bitcount(rsa->p) + 8) / 8; |
560 | qlen = (bignum_bitcount(rsa->q) + 8) / 8; |
561 | ulen = (bignum_bitcount(rsa->iqmp) + 8) / 8; |
65a22376 |
562 | |
563 | /* |
564 | * mpint private_exp, mpint p, mpint q, mpint iqmp. Total 16 + |
565 | * sum of lengths. |
566 | */ |
32874aea |
567 | bloblen = 16 + dlen + plen + qlen + ulen; |
3d88e64d |
568 | blob = snewn(bloblen, unsigned char); |
65a22376 |
569 | p = blob; |
32874aea |
570 | PUT_32BIT(p, dlen); |
571 | p += 4; |
572 | for (i = dlen; i--;) |
573 | *p++ = bignum_byte(rsa->private_exponent, i); |
574 | PUT_32BIT(p, plen); |
575 | p += 4; |
576 | for (i = plen; i--;) |
577 | *p++ = bignum_byte(rsa->p, i); |
578 | PUT_32BIT(p, qlen); |
579 | p += 4; |
580 | for (i = qlen; i--;) |
581 | *p++ = bignum_byte(rsa->q, i); |
582 | PUT_32BIT(p, ulen); |
583 | p += 4; |
584 | for (i = ulen; i--;) |
585 | *p++ = bignum_byte(rsa->iqmp, i); |
65a22376 |
586 | assert(p == blob + bloblen); |
587 | *len = bloblen; |
588 | return blob; |
589 | } |
590 | |
591 | static void *rsa2_createkey(unsigned char *pub_blob, int pub_len, |
32874aea |
592 | unsigned char *priv_blob, int priv_len) |
593 | { |
65a22376 |
594 | struct RSAKey *rsa; |
32874aea |
595 | char *pb = (char *) priv_blob; |
596 | |
597 | rsa = rsa2_newkey((char *) pub_blob, pub_len); |
65a22376 |
598 | rsa->private_exponent = getmp(&pb, &priv_len); |
599 | rsa->p = getmp(&pb, &priv_len); |
600 | rsa->q = getmp(&pb, &priv_len); |
601 | rsa->iqmp = getmp(&pb, &priv_len); |
602 | |
98f022f5 |
603 | if (!rsa_verify(rsa)) { |
604 | rsa2_freekey(rsa); |
605 | return NULL; |
606 | } |
607 | |
65a22376 |
608 | return rsa; |
609 | } |
610 | |
32874aea |
611 | static void *rsa2_openssh_createkey(unsigned char **blob, int *len) |
612 | { |
613 | char **b = (char **) blob; |
45cebe79 |
614 | struct RSAKey *rsa; |
45cebe79 |
615 | |
3d88e64d |
616 | rsa = snew(struct RSAKey); |
32874aea |
617 | if (!rsa) |
618 | return NULL; |
45cebe79 |
619 | rsa->comment = NULL; |
620 | |
621 | rsa->modulus = getmp(b, len); |
622 | rsa->exponent = getmp(b, len); |
623 | rsa->private_exponent = getmp(b, len); |
624 | rsa->iqmp = getmp(b, len); |
625 | rsa->p = getmp(b, len); |
626 | rsa->q = getmp(b, len); |
627 | |
628 | if (!rsa->modulus || !rsa->exponent || !rsa->private_exponent || |
629 | !rsa->iqmp || !rsa->p || !rsa->q) { |
630 | sfree(rsa->modulus); |
631 | sfree(rsa->exponent); |
632 | sfree(rsa->private_exponent); |
633 | sfree(rsa->iqmp); |
634 | sfree(rsa->p); |
635 | sfree(rsa->q); |
636 | sfree(rsa); |
637 | return NULL; |
638 | } |
639 | |
640 | return rsa; |
641 | } |
642 | |
32874aea |
643 | static int rsa2_openssh_fmtkey(void *key, unsigned char *blob, int len) |
644 | { |
645 | struct RSAKey *rsa = (struct RSAKey *) key; |
ddecd643 |
646 | int bloblen, i; |
647 | |
648 | bloblen = |
649 | ssh2_bignum_length(rsa->modulus) + |
650 | ssh2_bignum_length(rsa->exponent) + |
651 | ssh2_bignum_length(rsa->private_exponent) + |
652 | ssh2_bignum_length(rsa->iqmp) + |
32874aea |
653 | ssh2_bignum_length(rsa->p) + ssh2_bignum_length(rsa->q); |
ddecd643 |
654 | |
655 | if (bloblen > len) |
656 | return bloblen; |
657 | |
658 | bloblen = 0; |
659 | #define ENC(x) \ |
660 | PUT_32BIT(blob+bloblen, ssh2_bignum_length((x))-4); bloblen += 4; \ |
661 | for (i = ssh2_bignum_length((x))-4; i-- ;) blob[bloblen++]=bignum_byte((x),i); |
662 | ENC(rsa->modulus); |
663 | ENC(rsa->exponent); |
664 | ENC(rsa->private_exponent); |
665 | ENC(rsa->iqmp); |
666 | ENC(rsa->p); |
667 | ENC(rsa->q); |
668 | |
669 | return bloblen; |
670 | } |
671 | |
47a6b94c |
672 | static int rsa2_pubkey_bits(void *blob, int len) |
673 | { |
674 | struct RSAKey *rsa; |
675 | int ret; |
676 | |
677 | rsa = rsa2_newkey((char *) blob, len); |
678 | ret = bignum_bitcount(rsa->modulus); |
679 | rsa2_freekey(rsa); |
680 | |
681 | return ret; |
682 | } |
683 | |
32874aea |
684 | static char *rsa2_fingerprint(void *key) |
685 | { |
686 | struct RSAKey *rsa = (struct RSAKey *) key; |
85cc02bb |
687 | struct MD5Context md5c; |
688 | unsigned char digest[16], lenbuf[4]; |
32874aea |
689 | char buffer[16 * 3 + 40]; |
85cc02bb |
690 | char *ret; |
691 | int numlen, i; |
692 | |
693 | MD5Init(&md5c); |
9bf430c9 |
694 | MD5Update(&md5c, (unsigned char *)"\0\0\0\7ssh-rsa", 11); |
85cc02bb |
695 | |
696 | #define ADD_BIGNUM(bignum) \ |
ddecd643 |
697 | numlen = (bignum_bitcount(bignum)+8)/8; \ |
85cc02bb |
698 | PUT_32BIT(lenbuf, numlen); MD5Update(&md5c, lenbuf, 4); \ |
699 | for (i = numlen; i-- ;) { \ |
700 | unsigned char c = bignum_byte(bignum, i); \ |
701 | MD5Update(&md5c, &c, 1); \ |
702 | } |
703 | ADD_BIGNUM(rsa->exponent); |
704 | ADD_BIGNUM(rsa->modulus); |
705 | #undef ADD_BIGNUM |
706 | |
707 | MD5Final(digest, &md5c); |
708 | |
ddecd643 |
709 | sprintf(buffer, "ssh-rsa %d ", bignum_bitcount(rsa->modulus)); |
85cc02bb |
710 | for (i = 0; i < 16; i++) |
32874aea |
711 | sprintf(buffer + strlen(buffer), "%s%02x", i ? ":" : "", |
712 | digest[i]); |
3d88e64d |
713 | ret = snewn(strlen(buffer) + 1, char); |
85cc02bb |
714 | if (ret) |
32874aea |
715 | strcpy(ret, buffer); |
85cc02bb |
716 | return ret; |
717 | } |
718 | |
719 | /* |
720 | * This is the magic ASN.1/DER prefix that goes in the decoded |
721 | * signature, between the string of FFs and the actual SHA hash |
96a73db9 |
722 | * value. The meaning of it is: |
85cc02bb |
723 | * |
724 | * 00 -- this marks the end of the FFs; not part of the ASN.1 bit itself |
725 | * |
726 | * 30 21 -- a constructed SEQUENCE of length 0x21 |
727 | * 30 09 -- a constructed sub-SEQUENCE of length 9 |
728 | * 06 05 -- an object identifier, length 5 |
96a73db9 |
729 | * 2B 0E 03 02 1A -- object id { 1 3 14 3 2 26 } |
730 | * (the 1,3 comes from 0x2B = 43 = 40*1+3) |
85cc02bb |
731 | * 05 00 -- NULL |
732 | * 04 14 -- a primitive OCTET STRING of length 0x14 |
733 | * [0x14 bytes of hash data follows] |
96a73db9 |
734 | * |
735 | * The object id in the middle there is listed as `id-sha1' in |
736 | * ftp://ftp.rsasecurity.com/pub/pkcs/pkcs-1/pkcs-1v2-1d2.asn (the |
737 | * ASN module for PKCS #1) and its expanded form is as follows: |
738 | * |
739 | * id-sha1 OBJECT IDENTIFIER ::= { |
740 | * iso(1) identified-organization(3) oiw(14) secsig(3) |
741 | * algorithms(2) 26 } |
85cc02bb |
742 | */ |
b5864f2c |
743 | static const unsigned char asn1_weird_stuff[] = { |
32874aea |
744 | 0x00, 0x30, 0x21, 0x30, 0x09, 0x06, 0x05, 0x2B, |
745 | 0x0E, 0x03, 0x02, 0x1A, 0x05, 0x00, 0x04, 0x14, |
85cc02bb |
746 | }; |
747 | |
d8770b12 |
748 | #define ASN1_LEN ( (int) sizeof(asn1_weird_stuff) ) |
749 | |
85cc02bb |
750 | static int rsa2_verifysig(void *key, char *sig, int siglen, |
32874aea |
751 | char *data, int datalen) |
752 | { |
753 | struct RSAKey *rsa = (struct RSAKey *) key; |
85cc02bb |
754 | Bignum in, out; |
755 | char *p; |
756 | int slen; |
757 | int bytes, i, j, ret; |
758 | unsigned char hash[20]; |
759 | |
760 | getstring(&sig, &siglen, &p, &slen); |
761 | if (!p || slen != 7 || memcmp(p, "ssh-rsa", 7)) { |
32874aea |
762 | return 0; |
85cc02bb |
763 | } |
764 | in = getmp(&sig, &siglen); |
765 | out = modpow(in, rsa->exponent, rsa->modulus); |
766 | freebn(in); |
767 | |
768 | ret = 1; |
769 | |
7bd33644 |
770 | bytes = (bignum_bitcount(rsa->modulus)+7) / 8; |
85cc02bb |
771 | /* Top (partial) byte should be zero. */ |
32874aea |
772 | if (bignum_byte(out, bytes - 1) != 0) |
773 | ret = 0; |
85cc02bb |
774 | /* First whole byte should be 1. */ |
32874aea |
775 | if (bignum_byte(out, bytes - 2) != 1) |
776 | ret = 0; |
85cc02bb |
777 | /* Most of the rest should be FF. */ |
32874aea |
778 | for (i = bytes - 3; i >= 20 + ASN1_LEN; i--) { |
779 | if (bignum_byte(out, i) != 0xFF) |
780 | ret = 0; |
85cc02bb |
781 | } |
782 | /* Then we expect to see the asn1_weird_stuff. */ |
32874aea |
783 | for (i = 20 + ASN1_LEN - 1, j = 0; i >= 20; i--, j++) { |
784 | if (bignum_byte(out, i) != asn1_weird_stuff[j]) |
785 | ret = 0; |
85cc02bb |
786 | } |
787 | /* Finally, we expect to see the SHA-1 hash of the signed data. */ |
788 | SHA_Simple(data, datalen, hash); |
32874aea |
789 | for (i = 19, j = 0; i >= 0; i--, j++) { |
790 | if (bignum_byte(out, i) != hash[j]) |
791 | ret = 0; |
85cc02bb |
792 | } |
679539d7 |
793 | freebn(out); |
85cc02bb |
794 | |
795 | return ret; |
796 | } |
797 | |
164feb13 |
798 | static unsigned char *rsa2_sign(void *key, char *data, int datalen, |
799 | int *siglen) |
32874aea |
800 | { |
801 | struct RSAKey *rsa = (struct RSAKey *) key; |
65a22376 |
802 | unsigned char *bytes; |
803 | int nbytes; |
804 | unsigned char hash[20]; |
805 | Bignum in, out; |
806 | int i, j; |
807 | |
808 | SHA_Simple(data, datalen, hash); |
809 | |
32874aea |
810 | nbytes = (bignum_bitcount(rsa->modulus) - 1) / 8; |
e99cd73f |
811 | assert(1 <= nbytes - 20 - ASN1_LEN); |
3d88e64d |
812 | bytes = snewn(nbytes, unsigned char); |
65a22376 |
813 | |
814 | bytes[0] = 1; |
32874aea |
815 | for (i = 1; i < nbytes - 20 - ASN1_LEN; i++) |
65a22376 |
816 | bytes[i] = 0xFF; |
32874aea |
817 | for (i = nbytes - 20 - ASN1_LEN, j = 0; i < nbytes - 20; i++, j++) |
65a22376 |
818 | bytes[i] = asn1_weird_stuff[j]; |
32874aea |
819 | for (i = nbytes - 20, j = 0; i < nbytes; i++, j++) |
65a22376 |
820 | bytes[i] = hash[j]; |
821 | |
822 | in = bignum_from_bytes(bytes, nbytes); |
823 | sfree(bytes); |
824 | |
8671a580 |
825 | out = rsa_privkey_op(in, rsa); |
65a22376 |
826 | freebn(in); |
827 | |
32874aea |
828 | nbytes = (bignum_bitcount(out) + 7) / 8; |
3d88e64d |
829 | bytes = snewn(4 + 7 + 4 + nbytes, unsigned char); |
65a22376 |
830 | PUT_32BIT(bytes, 7); |
32874aea |
831 | memcpy(bytes + 4, "ssh-rsa", 7); |
832 | PUT_32BIT(bytes + 4 + 7, nbytes); |
65a22376 |
833 | for (i = 0; i < nbytes; i++) |
32874aea |
834 | bytes[4 + 7 + 4 + i] = bignum_byte(out, nbytes - 1 - i); |
65a22376 |
835 | freebn(out); |
836 | |
32874aea |
837 | *siglen = 4 + 7 + 4 + nbytes; |
65a22376 |
838 | return bytes; |
85cc02bb |
839 | } |
840 | |
65a22376 |
841 | const struct ssh_signkey ssh_rsa = { |
85cc02bb |
842 | rsa2_newkey, |
843 | rsa2_freekey, |
844 | rsa2_fmtkey, |
65a22376 |
845 | rsa2_public_blob, |
846 | rsa2_private_blob, |
847 | rsa2_createkey, |
45cebe79 |
848 | rsa2_openssh_createkey, |
ddecd643 |
849 | rsa2_openssh_fmtkey, |
47a6b94c |
850 | rsa2_pubkey_bits, |
85cc02bb |
851 | rsa2_fingerprint, |
852 | rsa2_verifysig, |
853 | rsa2_sign, |
854 | "ssh-rsa", |
855 | "rsa2" |
856 | }; |
fae1a71b |
857 | |
858 | void *ssh_rsakex_newkey(char *data, int len) |
859 | { |
860 | return rsa2_newkey(data, len); |
861 | } |
862 | |
863 | void ssh_rsakex_freekey(void *key) |
864 | { |
865 | rsa2_freekey(key); |
866 | } |
867 | |
868 | int ssh_rsakex_klen(void *key) |
869 | { |
870 | struct RSAKey *rsa = (struct RSAKey *) key; |
871 | |
872 | return bignum_bitcount(rsa->modulus); |
873 | } |
874 | |
875 | static void oaep_mask(const struct ssh_hash *h, void *seed, int seedlen, |
876 | void *vdata, int datalen) |
877 | { |
878 | unsigned char *data = (unsigned char *)vdata; |
879 | unsigned count = 0; |
880 | |
881 | while (datalen > 0) { |
882 | int i, max = (datalen > h->hlen ? h->hlen : datalen); |
883 | void *s; |
143ec28a |
884 | unsigned char counter[4], hash[SSH2_KEX_MAX_HASH_LEN]; |
fae1a71b |
885 | |
143ec28a |
886 | assert(h->hlen <= SSH2_KEX_MAX_HASH_LEN); |
fae1a71b |
887 | PUT_32BIT(counter, count); |
888 | s = h->init(); |
889 | h->bytes(s, seed, seedlen); |
890 | h->bytes(s, counter, 4); |
891 | h->final(s, hash); |
892 | count++; |
893 | |
894 | for (i = 0; i < max; i++) |
895 | data[i] ^= hash[i]; |
896 | |
897 | data += max; |
898 | datalen -= max; |
899 | } |
900 | } |
901 | |
902 | void ssh_rsakex_encrypt(const struct ssh_hash *h, unsigned char *in, int inlen, |
903 | unsigned char *out, int outlen, |
904 | void *key) |
905 | { |
906 | Bignum b1, b2; |
907 | struct RSAKey *rsa = (struct RSAKey *) key; |
908 | int k, i; |
909 | char *p; |
910 | const int HLEN = h->hlen; |
911 | |
912 | /* |
913 | * Here we encrypt using RSAES-OAEP. Essentially this means: |
914 | * |
915 | * - we have a SHA-based `mask generation function' which |
916 | * creates a pseudo-random stream of mask data |
917 | * deterministically from an input chunk of data. |
918 | * |
919 | * - we have a random chunk of data called a seed. |
920 | * |
921 | * - we use the seed to generate a mask which we XOR with our |
922 | * plaintext. |
923 | * |
924 | * - then we use _the masked plaintext_ to generate a mask |
925 | * which we XOR with the seed. |
926 | * |
927 | * - then we concatenate the masked seed and the masked |
928 | * plaintext, and RSA-encrypt that lot. |
929 | * |
930 | * The result is that the data input to the encryption function |
931 | * is random-looking and (hopefully) contains no exploitable |
932 | * structure such as PKCS1-v1_5 does. |
933 | * |
934 | * For a precise specification, see RFC 3447, section 7.1.1. |
935 | * Some of the variable names below are derived from that, so |
936 | * it'd probably help to read it anyway. |
937 | */ |
938 | |
939 | /* k denotes the length in octets of the RSA modulus. */ |
940 | k = (7 + bignum_bitcount(rsa->modulus)) / 8; |
941 | |
942 | /* The length of the input data must be at most k - 2hLen - 2. */ |
943 | assert(inlen > 0 && inlen <= k - 2*HLEN - 2); |
944 | |
945 | /* The length of the output data wants to be precisely k. */ |
946 | assert(outlen == k); |
947 | |
948 | /* |
949 | * Now perform EME-OAEP encoding. First set up all the unmasked |
950 | * output data. |
951 | */ |
952 | /* Leading byte zero. */ |
953 | out[0] = 0; |
954 | /* At position 1, the seed: HLEN bytes of random data. */ |
955 | for (i = 0; i < HLEN; i++) |
956 | out[i + 1] = random_byte(); |
957 | /* At position 1+HLEN, the data block DB, consisting of: */ |
958 | /* The hash of the label (we only support an empty label here) */ |
959 | h->final(h->init(), out + HLEN + 1); |
960 | /* A bunch of zero octets */ |
961 | memset(out + 2*HLEN + 1, 0, outlen - (2*HLEN + 1)); |
962 | /* A single 1 octet, followed by the input message data. */ |
963 | out[outlen - inlen - 1] = 1; |
964 | memcpy(out + outlen - inlen, in, inlen); |
965 | |
966 | /* |
967 | * Now use the seed data to mask the block DB. |
968 | */ |
969 | oaep_mask(h, out+1, HLEN, out+HLEN+1, outlen-HLEN-1); |
970 | |
971 | /* |
972 | * And now use the masked DB to mask the seed itself. |
973 | */ |
974 | oaep_mask(h, out+HLEN+1, outlen-HLEN-1, out+1, HLEN); |
975 | |
976 | /* |
977 | * Now `out' contains precisely the data we want to |
978 | * RSA-encrypt. |
979 | */ |
980 | b1 = bignum_from_bytes(out, outlen); |
981 | b2 = modpow(b1, rsa->exponent, rsa->modulus); |
7108a872 |
982 | p = (char *)out; |
fae1a71b |
983 | for (i = outlen; i--;) { |
984 | *p++ = bignum_byte(b2, i); |
985 | } |
986 | freebn(b1); |
987 | freebn(b2); |
988 | |
989 | /* |
990 | * And we're done. |
991 | */ |
992 | } |
993 | |
994 | static const struct ssh_kex ssh_rsa_kex_sha1 = { |
995 | "rsa1024-sha1", NULL, KEXTYPE_RSA, NULL, NULL, 0, 0, &ssh_sha1 |
996 | }; |
997 | |
998 | static const struct ssh_kex ssh_rsa_kex_sha256 = { |
999 | "rsa2048-sha256", NULL, KEXTYPE_RSA, NULL, NULL, 0, 0, &ssh_sha256 |
1000 | }; |
1001 | |
1002 | static const struct ssh_kex *const rsa_kex_list[] = { |
1003 | &ssh_rsa_kex_sha256, |
1004 | &ssh_rsa_kex_sha1 |
1005 | }; |
1006 | |
1007 | const struct ssh_kexes ssh_rsa_kex = { |
1008 | sizeof(rsa_kex_list) / sizeof(*rsa_kex_list), |
1009 | rsa_kex_list |
1010 | }; |