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 | |
3f2d010c |
13 | #define GET_32BIT(cp) \ |
14 | (((unsigned long)(unsigned char)(cp)[0] << 24) | \ |
15 | ((unsigned long)(unsigned char)(cp)[1] << 16) | \ |
16 | ((unsigned long)(unsigned char)(cp)[2] << 8) | \ |
17 | ((unsigned long)(unsigned char)(cp)[3])) |
18 | |
19 | #define PUT_32BIT(cp, value) { \ |
20 | (cp)[0] = (unsigned char)((value) >> 24); \ |
21 | (cp)[1] = (unsigned char)((value) >> 16); \ |
22 | (cp)[2] = (unsigned char)((value) >> 8); \ |
23 | (cp)[3] = (unsigned char)(value); } |
1c2a93c4 |
24 | |
0016d70b |
25 | int makekey(unsigned char *data, int len, struct RSAKey *result, |
32874aea |
26 | unsigned char **keystr, int order) |
27 | { |
374330e2 |
28 | unsigned char *p = data; |
0016d70b |
29 | int i, n; |
30 | |
31 | if (len < 4) |
32 | return -1; |
374330e2 |
33 | |
a52f067e |
34 | if (result) { |
32874aea |
35 | result->bits = 0; |
36 | for (i = 0; i < 4; i++) |
37 | result->bits = (result->bits << 8) + *p++; |
a52f067e |
38 | } else |
32874aea |
39 | p += 4; |
374330e2 |
40 | |
0016d70b |
41 | len -= 4; |
42 | |
7cca0d81 |
43 | /* |
44 | * order=0 means exponent then modulus (the keys sent by the |
45 | * server). order=1 means modulus then exponent (the keys |
46 | * stored in a keyfile). |
47 | */ |
374330e2 |
48 | |
0016d70b |
49 | if (order == 0) { |
50 | n = ssh1_read_bignum(p, len, result ? &result->exponent : NULL); |
51 | if (n < 0) return -1; |
52 | p += n; |
53 | len -= n; |
54 | } |
55 | |
56 | n = ssh1_read_bignum(p, len, result ? &result->modulus : NULL); |
26d98fc6 |
57 | if (n < 0 || (result && bignum_bitcount(result->modulus) == 0)) return -1; |
a52f067e |
58 | if (result) |
0016d70b |
59 | result->bytes = n - 2; |
32874aea |
60 | if (keystr) |
61 | *keystr = p + 2; |
0016d70b |
62 | p += n; |
63 | len -= n; |
64 | |
65 | if (order == 1) { |
66 | n = ssh1_read_bignum(p, len, result ? &result->exponent : NULL); |
67 | if (n < 0) return -1; |
68 | p += n; |
69 | len -= n; |
70 | } |
374330e2 |
71 | return p - data; |
72 | } |
73 | |
0016d70b |
74 | int makeprivate(unsigned char *data, int len, struct RSAKey *result) |
32874aea |
75 | { |
0016d70b |
76 | return ssh1_read_bignum(data, len, &result->private_exponent); |
7cca0d81 |
77 | } |
78 | |
0016d70b |
79 | int rsaencrypt(unsigned char *data, int length, struct RSAKey *key) |
32874aea |
80 | { |
374330e2 |
81 | Bignum b1, b2; |
3709bfe9 |
82 | int i; |
374330e2 |
83 | unsigned char *p; |
84 | |
0016d70b |
85 | if (key->bytes < length + 4) |
86 | return 0; /* RSA key too short! */ |
87 | |
32874aea |
88 | memmove(data + key->bytes - length, data, length); |
374330e2 |
89 | data[0] = 0; |
90 | data[1] = 2; |
91 | |
32874aea |
92 | for (i = 2; i < key->bytes - length - 1; i++) { |
374330e2 |
93 | do { |
94 | data[i] = random_byte(); |
95 | } while (data[i] == 0); |
96 | } |
32874aea |
97 | data[key->bytes - length - 1] = 0; |
374330e2 |
98 | |
3709bfe9 |
99 | b1 = bignum_from_bytes(data, key->bytes); |
374330e2 |
100 | |
59600f67 |
101 | b2 = modpow(b1, key->exponent, key->modulus); |
374330e2 |
102 | |
374330e2 |
103 | p = data; |
32874aea |
104 | for (i = key->bytes; i--;) { |
105 | *p++ = bignum_byte(b2, i); |
374330e2 |
106 | } |
107 | |
108 | freebn(b1); |
109 | freebn(b2); |
0016d70b |
110 | |
111 | return 1; |
374330e2 |
112 | } |
113 | |
b492c4d7 |
114 | static void sha512_mpint(SHA512_State * s, Bignum b) |
115 | { |
116 | unsigned char lenbuf[4]; |
117 | int len; |
118 | len = (bignum_bitcount(b) + 8) / 8; |
119 | PUT_32BIT(lenbuf, len); |
120 | SHA512_Bytes(s, lenbuf, 4); |
121 | while (len-- > 0) { |
122 | lenbuf[0] = bignum_byte(b, len); |
123 | SHA512_Bytes(s, lenbuf, 1); |
124 | } |
125 | memset(lenbuf, 0, sizeof(lenbuf)); |
126 | } |
127 | |
8671a580 |
128 | /* |
129 | * This function is a wrapper on modpow(). It has the same effect |
130 | * as modpow(), but employs RSA blinding to protect against timing |
131 | * attacks. |
132 | */ |
133 | static Bignum rsa_privkey_op(Bignum input, struct RSAKey *key) |
32874aea |
134 | { |
8671a580 |
135 | Bignum random, random_encrypted, random_inverse; |
136 | Bignum input_blinded, ret_blinded; |
7cca0d81 |
137 | Bignum ret; |
8671a580 |
138 | |
b492c4d7 |
139 | SHA512_State ss; |
140 | unsigned char digest512[64]; |
141 | int digestused = lenof(digest512); |
142 | int hashseq = 0; |
143 | |
8671a580 |
144 | /* |
145 | * Start by inventing a random number chosen uniformly from the |
146 | * range 2..modulus-1. (We do this by preparing a random number |
147 | * of the right length and retrying if it's greater than the |
148 | * modulus, to prevent any potential Bleichenbacher-like |
149 | * attacks making use of the uneven distribution within the |
150 | * range that would arise from just reducing our number mod n. |
151 | * There are timing implications to the potential retries, of |
152 | * course, but all they tell you is the modulus, which you |
153 | * already knew.) |
b492c4d7 |
154 | * |
155 | * To preserve determinism and avoid Pageant needing to share |
156 | * the random number pool, we actually generate this `random' |
157 | * number by hashing stuff with the private key. |
8671a580 |
158 | */ |
159 | while (1) { |
160 | int bits, byte, bitsleft, v; |
161 | random = copybn(key->modulus); |
162 | /* |
163 | * Find the topmost set bit. (This function will return its |
164 | * index plus one.) Then we'll set all bits from that one |
165 | * downwards randomly. |
166 | */ |
167 | bits = bignum_bitcount(random); |
168 | byte = 0; |
169 | bitsleft = 0; |
170 | while (bits--) { |
b492c4d7 |
171 | if (bitsleft <= 0) { |
172 | bitsleft = 8; |
173 | /* |
174 | * Conceptually the following few lines are equivalent to |
175 | * byte = random_byte(); |
176 | */ |
177 | if (digestused >= lenof(digest512)) { |
178 | unsigned char seqbuf[4]; |
179 | PUT_32BIT(seqbuf, hashseq); |
180 | SHA512_Init(&ss); |
181 | SHA512_Bytes(&ss, "RSA deterministic blinding", 26); |
182 | SHA512_Bytes(&ss, seqbuf, sizeof(seqbuf)); |
183 | sha512_mpint(&ss, key->private_exponent); |
184 | SHA512_Final(&ss, digest512); |
185 | hashseq++; |
186 | |
187 | /* |
188 | * Now hash that digest plus the signature |
189 | * input. |
190 | */ |
191 | SHA512_Init(&ss); |
192 | SHA512_Bytes(&ss, digest512, sizeof(digest512)); |
193 | sha512_mpint(&ss, input); |
194 | SHA512_Final(&ss, digest512); |
195 | |
196 | digestused = 0; |
197 | } |
198 | byte = digest512[digestused++]; |
199 | } |
8671a580 |
200 | v = byte & 1; |
201 | byte >>= 1; |
202 | bitsleft--; |
203 | bignum_set_bit(random, bits, v); |
204 | } |
205 | |
206 | /* |
207 | * Now check that this number is strictly greater than |
208 | * zero, and strictly less than modulus. |
209 | */ |
210 | if (bignum_cmp(random, Zero) <= 0 || |
211 | bignum_cmp(random, key->modulus) >= 0) { |
212 | freebn(random); |
213 | continue; |
214 | } else { |
215 | break; |
216 | } |
217 | } |
218 | |
219 | /* |
220 | * RSA blinding relies on the fact that (xy)^d mod n is equal |
221 | * to (x^d mod n) * (y^d mod n) mod n. We invent a random pair |
033a3ded |
222 | * y and y^d; then we multiply x by y, raise to the power d mod |
223 | * n as usual, and divide by y^d to recover x^d. Thus an |
224 | * attacker can't correlate the timing of the modpow with the |
225 | * input, because they don't know anything about the number |
226 | * that was input to the actual modpow. |
8671a580 |
227 | * |
228 | * The clever bit is that we don't have to do a huge modpow to |
229 | * get y and y^d; we will use the number we just invented as |
033a3ded |
230 | * _y^d_, and use the _public_ exponent to compute (y^d)^e = y |
231 | * from it, which is much faster to do. |
8671a580 |
232 | */ |
233 | random_encrypted = modpow(random, key->exponent, key->modulus); |
234 | random_inverse = modinv(random, key->modulus); |
235 | input_blinded = modmul(input, random_encrypted, key->modulus); |
236 | ret_blinded = modpow(input_blinded, key->private_exponent, key->modulus); |
237 | ret = modmul(ret_blinded, random_inverse, key->modulus); |
238 | |
239 | freebn(ret_blinded); |
240 | freebn(input_blinded); |
241 | freebn(random_inverse); |
242 | freebn(random_encrypted); |
243 | freebn(random); |
244 | |
7cca0d81 |
245 | return ret; |
246 | } |
247 | |
8671a580 |
248 | Bignum rsadecrypt(Bignum input, struct RSAKey *key) |
249 | { |
250 | return rsa_privkey_op(input, key); |
251 | } |
252 | |
32874aea |
253 | int rsastr_len(struct RSAKey *key) |
254 | { |
374330e2 |
255 | Bignum md, ex; |
3709bfe9 |
256 | int mdlen, exlen; |
374330e2 |
257 | |
258 | md = key->modulus; |
259 | ex = key->exponent; |
32874aea |
260 | mdlen = (bignum_bitcount(md) + 15) / 16; |
261 | exlen = (bignum_bitcount(ex) + 15) / 16; |
262 | return 4 * (mdlen + exlen) + 20; |
374330e2 |
263 | } |
264 | |
32874aea |
265 | void rsastr_fmt(char *str, struct RSAKey *key) |
266 | { |
374330e2 |
267 | Bignum md, ex; |
d5859615 |
268 | int len = 0, i, nibbles; |
269 | static const char hex[] = "0123456789abcdef"; |
374330e2 |
270 | |
271 | md = key->modulus; |
272 | ex = key->exponent; |
273 | |
32874aea |
274 | len += sprintf(str + len, "0x"); |
d5859615 |
275 | |
32874aea |
276 | nibbles = (3 + bignum_bitcount(ex)) / 4; |
277 | if (nibbles < 1) |
278 | nibbles = 1; |
279 | for (i = nibbles; i--;) |
280 | str[len++] = hex[(bignum_byte(ex, i / 2) >> (4 * (i % 2))) & 0xF]; |
d5859615 |
281 | |
32874aea |
282 | len += sprintf(str + len, ",0x"); |
d5859615 |
283 | |
32874aea |
284 | nibbles = (3 + bignum_bitcount(md)) / 4; |
285 | if (nibbles < 1) |
286 | nibbles = 1; |
287 | for (i = nibbles; i--;) |
288 | str[len++] = hex[(bignum_byte(md, i / 2) >> (4 * (i % 2))) & 0xF]; |
d5859615 |
289 | |
374330e2 |
290 | str[len] = '\0'; |
291 | } |
292 | |
1c2a93c4 |
293 | /* |
294 | * Generate a fingerprint string for the key. Compatible with the |
295 | * OpenSSH fingerprint code. |
296 | */ |
32874aea |
297 | void rsa_fingerprint(char *str, int len, struct RSAKey *key) |
298 | { |
1c2a93c4 |
299 | struct MD5Context md5c; |
300 | unsigned char digest[16]; |
32874aea |
301 | char buffer[16 * 3 + 40]; |
1c2a93c4 |
302 | int numlen, slen, i; |
303 | |
304 | MD5Init(&md5c); |
305 | numlen = ssh1_bignum_length(key->modulus) - 2; |
32874aea |
306 | for (i = numlen; i--;) { |
307 | unsigned char c = bignum_byte(key->modulus, i); |
308 | MD5Update(&md5c, &c, 1); |
1c2a93c4 |
309 | } |
310 | numlen = ssh1_bignum_length(key->exponent) - 2; |
32874aea |
311 | for (i = numlen; i--;) { |
312 | unsigned char c = bignum_byte(key->exponent, i); |
313 | MD5Update(&md5c, &c, 1); |
1c2a93c4 |
314 | } |
315 | MD5Final(digest, &md5c); |
316 | |
ddecd643 |
317 | sprintf(buffer, "%d ", bignum_bitcount(key->modulus)); |
1c2a93c4 |
318 | for (i = 0; i < 16; i++) |
32874aea |
319 | sprintf(buffer + strlen(buffer), "%s%02x", i ? ":" : "", |
320 | digest[i]); |
321 | strncpy(str, buffer, len); |
322 | str[len - 1] = '\0'; |
1c2a93c4 |
323 | slen = strlen(str); |
32874aea |
324 | if (key->comment && slen < len - 1) { |
325 | str[slen] = ' '; |
326 | strncpy(str + slen + 1, key->comment, len - slen - 1); |
327 | str[len - 1] = '\0'; |
1c2a93c4 |
328 | } |
329 | } |
330 | |
98f022f5 |
331 | /* |
332 | * Verify that the public data in an RSA key matches the private |
60fe6ff7 |
333 | * data. We also check the private data itself: we ensure that p > |
334 | * q and that iqmp really is the inverse of q mod p. |
98f022f5 |
335 | */ |
32874aea |
336 | int rsa_verify(struct RSAKey *key) |
337 | { |
60fe6ff7 |
338 | Bignum n, ed, pm1, qm1; |
98f022f5 |
339 | int cmp; |
340 | |
341 | /* n must equal pq. */ |
342 | n = bigmul(key->p, key->q); |
343 | cmp = bignum_cmp(n, key->modulus); |
344 | freebn(n); |
345 | if (cmp != 0) |
346 | return 0; |
347 | |
60fe6ff7 |
348 | /* e * d must be congruent to 1, modulo (p-1) and modulo (q-1). */ |
98f022f5 |
349 | pm1 = copybn(key->p); |
350 | decbn(pm1); |
60fe6ff7 |
351 | ed = modmul(key->exponent, key->private_exponent, pm1); |
352 | cmp = bignum_cmp(ed, One); |
353 | sfree(ed); |
354 | if (cmp != 0) |
355 | return 0; |
356 | |
98f022f5 |
357 | qm1 = copybn(key->q); |
358 | decbn(qm1); |
60fe6ff7 |
359 | ed = modmul(key->exponent, key->private_exponent, qm1); |
98f022f5 |
360 | cmp = bignum_cmp(ed, One); |
361 | sfree(ed); |
362 | if (cmp != 0) |
363 | return 0; |
014970c8 |
364 | |
60fe6ff7 |
365 | /* |
366 | * Ensure p > q. |
367 | */ |
368 | if (bignum_cmp(key->p, key->q) <= 0) |
32874aea |
369 | return 0; |
60fe6ff7 |
370 | |
371 | /* |
372 | * Ensure iqmp * q is congruent to 1, modulo p. |
373 | */ |
374 | n = modmul(key->iqmp, key->q, key->p); |
375 | cmp = bignum_cmp(n, One); |
376 | sfree(n); |
377 | if (cmp != 0) |
32874aea |
378 | return 0; |
60fe6ff7 |
379 | |
014970c8 |
380 | return 1; |
98f022f5 |
381 | } |
382 | |
3f2d010c |
383 | /* Public key blob as used by Pageant: exponent before modulus. */ |
384 | unsigned char *rsa_public_blob(struct RSAKey *key, int *len) |
385 | { |
386 | int length, pos; |
387 | unsigned char *ret; |
388 | |
389 | length = (ssh1_bignum_length(key->modulus) + |
390 | ssh1_bignum_length(key->exponent) + 4); |
3d88e64d |
391 | ret = snewn(length, unsigned char); |
3f2d010c |
392 | |
393 | PUT_32BIT(ret, bignum_bitcount(key->modulus)); |
394 | pos = 4; |
395 | pos += ssh1_write_bignum(ret + pos, key->exponent); |
396 | pos += ssh1_write_bignum(ret + pos, key->modulus); |
397 | |
398 | *len = length; |
399 | return ret; |
400 | } |
401 | |
402 | /* Given a public blob, determine its length. */ |
0016d70b |
403 | int rsa_public_blob_len(void *data, int maxlen) |
3f2d010c |
404 | { |
405 | unsigned char *p = (unsigned char *)data; |
0016d70b |
406 | int n; |
3f2d010c |
407 | |
0016d70b |
408 | if (maxlen < 4) |
409 | return -1; |
3f2d010c |
410 | p += 4; /* length word */ |
0016d70b |
411 | maxlen -= 4; |
412 | |
413 | n = ssh1_read_bignum(p, maxlen, NULL); /* exponent */ |
414 | if (n < 0) |
415 | return -1; |
416 | p += n; |
417 | |
418 | n = ssh1_read_bignum(p, maxlen, NULL); /* modulus */ |
419 | if (n < 0) |
420 | return -1; |
421 | p += n; |
3f2d010c |
422 | |
423 | return p - (unsigned char *)data; |
424 | } |
425 | |
32874aea |
426 | void freersakey(struct RSAKey *key) |
427 | { |
428 | if (key->modulus) |
429 | freebn(key->modulus); |
430 | if (key->exponent) |
431 | freebn(key->exponent); |
432 | if (key->private_exponent) |
433 | freebn(key->private_exponent); |
434 | if (key->comment) |
435 | sfree(key->comment); |
5c58ad2d |
436 | } |
85cc02bb |
437 | |
438 | /* ---------------------------------------------------------------------- |
439 | * Implementation of the ssh-rsa signing key type. |
440 | */ |
441 | |
32874aea |
442 | static void getstring(char **data, int *datalen, char **p, int *length) |
443 | { |
85cc02bb |
444 | *p = NULL; |
445 | if (*datalen < 4) |
32874aea |
446 | return; |
85cc02bb |
447 | *length = GET_32BIT(*data); |
32874aea |
448 | *datalen -= 4; |
449 | *data += 4; |
85cc02bb |
450 | if (*datalen < *length) |
32874aea |
451 | return; |
85cc02bb |
452 | *p = *data; |
32874aea |
453 | *data += *length; |
454 | *datalen -= *length; |
85cc02bb |
455 | } |
32874aea |
456 | static Bignum getmp(char **data, int *datalen) |
457 | { |
85cc02bb |
458 | char *p; |
459 | int length; |
460 | Bignum b; |
461 | |
462 | getstring(data, datalen, &p, &length); |
463 | if (!p) |
32874aea |
464 | return NULL; |
9bf430c9 |
465 | b = bignum_from_bytes((unsigned char *)p, length); |
85cc02bb |
466 | return b; |
467 | } |
468 | |
32874aea |
469 | static void *rsa2_newkey(char *data, int len) |
470 | { |
85cc02bb |
471 | char *p; |
472 | int slen; |
473 | struct RSAKey *rsa; |
474 | |
3d88e64d |
475 | rsa = snew(struct RSAKey); |
32874aea |
476 | if (!rsa) |
477 | return NULL; |
85cc02bb |
478 | getstring(&data, &len, &p, &slen); |
479 | |
45cebe79 |
480 | if (!p || slen != 7 || memcmp(p, "ssh-rsa", 7)) { |
85cc02bb |
481 | sfree(rsa); |
482 | return NULL; |
483 | } |
484 | rsa->exponent = getmp(&data, &len); |
485 | rsa->modulus = getmp(&data, &len); |
486 | rsa->private_exponent = NULL; |
487 | rsa->comment = NULL; |
488 | |
489 | return rsa; |
490 | } |
491 | |
32874aea |
492 | static void rsa2_freekey(void *key) |
493 | { |
494 | struct RSAKey *rsa = (struct RSAKey *) key; |
85cc02bb |
495 | freersakey(rsa); |
496 | sfree(rsa); |
497 | } |
498 | |
32874aea |
499 | static char *rsa2_fmtkey(void *key) |
500 | { |
501 | struct RSAKey *rsa = (struct RSAKey *) key; |
85cc02bb |
502 | char *p; |
503 | int len; |
32874aea |
504 | |
85cc02bb |
505 | len = rsastr_len(rsa); |
3d88e64d |
506 | p = snewn(len, char); |
32874aea |
507 | rsastr_fmt(p, rsa); |
85cc02bb |
508 | return p; |
509 | } |
510 | |
32874aea |
511 | static unsigned char *rsa2_public_blob(void *key, int *len) |
512 | { |
513 | struct RSAKey *rsa = (struct RSAKey *) key; |
65a22376 |
514 | int elen, mlen, bloblen; |
515 | int i; |
516 | unsigned char *blob, *p; |
517 | |
32874aea |
518 | elen = (bignum_bitcount(rsa->exponent) + 8) / 8; |
519 | mlen = (bignum_bitcount(rsa->modulus) + 8) / 8; |
65a22376 |
520 | |
521 | /* |
522 | * string "ssh-rsa", mpint exp, mpint mod. Total 19+elen+mlen. |
523 | * (three length fields, 12+7=19). |
524 | */ |
32874aea |
525 | bloblen = 19 + elen + mlen; |
3d88e64d |
526 | blob = snewn(bloblen, unsigned char); |
65a22376 |
527 | p = blob; |
32874aea |
528 | PUT_32BIT(p, 7); |
529 | p += 4; |
530 | memcpy(p, "ssh-rsa", 7); |
531 | p += 7; |
532 | PUT_32BIT(p, elen); |
533 | p += 4; |
534 | for (i = elen; i--;) |
535 | *p++ = bignum_byte(rsa->exponent, i); |
536 | PUT_32BIT(p, mlen); |
537 | p += 4; |
538 | for (i = mlen; i--;) |
539 | *p++ = bignum_byte(rsa->modulus, i); |
65a22376 |
540 | assert(p == blob + bloblen); |
541 | *len = bloblen; |
542 | return blob; |
543 | } |
544 | |
32874aea |
545 | static unsigned char *rsa2_private_blob(void *key, int *len) |
546 | { |
547 | struct RSAKey *rsa = (struct RSAKey *) key; |
65a22376 |
548 | int dlen, plen, qlen, ulen, bloblen; |
549 | int i; |
550 | unsigned char *blob, *p; |
551 | |
32874aea |
552 | dlen = (bignum_bitcount(rsa->private_exponent) + 8) / 8; |
553 | plen = (bignum_bitcount(rsa->p) + 8) / 8; |
554 | qlen = (bignum_bitcount(rsa->q) + 8) / 8; |
555 | ulen = (bignum_bitcount(rsa->iqmp) + 8) / 8; |
65a22376 |
556 | |
557 | /* |
558 | * mpint private_exp, mpint p, mpint q, mpint iqmp. Total 16 + |
559 | * sum of lengths. |
560 | */ |
32874aea |
561 | bloblen = 16 + dlen + plen + qlen + ulen; |
3d88e64d |
562 | blob = snewn(bloblen, unsigned char); |
65a22376 |
563 | p = blob; |
32874aea |
564 | PUT_32BIT(p, dlen); |
565 | p += 4; |
566 | for (i = dlen; i--;) |
567 | *p++ = bignum_byte(rsa->private_exponent, i); |
568 | PUT_32BIT(p, plen); |
569 | p += 4; |
570 | for (i = plen; i--;) |
571 | *p++ = bignum_byte(rsa->p, i); |
572 | PUT_32BIT(p, qlen); |
573 | p += 4; |
574 | for (i = qlen; i--;) |
575 | *p++ = bignum_byte(rsa->q, i); |
576 | PUT_32BIT(p, ulen); |
577 | p += 4; |
578 | for (i = ulen; i--;) |
579 | *p++ = bignum_byte(rsa->iqmp, i); |
65a22376 |
580 | assert(p == blob + bloblen); |
581 | *len = bloblen; |
582 | return blob; |
583 | } |
584 | |
585 | static void *rsa2_createkey(unsigned char *pub_blob, int pub_len, |
32874aea |
586 | unsigned char *priv_blob, int priv_len) |
587 | { |
65a22376 |
588 | struct RSAKey *rsa; |
32874aea |
589 | char *pb = (char *) priv_blob; |
590 | |
591 | rsa = rsa2_newkey((char *) pub_blob, pub_len); |
65a22376 |
592 | rsa->private_exponent = getmp(&pb, &priv_len); |
593 | rsa->p = getmp(&pb, &priv_len); |
594 | rsa->q = getmp(&pb, &priv_len); |
595 | rsa->iqmp = getmp(&pb, &priv_len); |
596 | |
98f022f5 |
597 | if (!rsa_verify(rsa)) { |
598 | rsa2_freekey(rsa); |
599 | return NULL; |
600 | } |
601 | |
65a22376 |
602 | return rsa; |
603 | } |
604 | |
32874aea |
605 | static void *rsa2_openssh_createkey(unsigned char **blob, int *len) |
606 | { |
607 | char **b = (char **) blob; |
45cebe79 |
608 | struct RSAKey *rsa; |
45cebe79 |
609 | |
3d88e64d |
610 | rsa = snew(struct RSAKey); |
32874aea |
611 | if (!rsa) |
612 | return NULL; |
45cebe79 |
613 | rsa->comment = NULL; |
614 | |
615 | rsa->modulus = getmp(b, len); |
616 | rsa->exponent = getmp(b, len); |
617 | rsa->private_exponent = getmp(b, len); |
618 | rsa->iqmp = getmp(b, len); |
619 | rsa->p = getmp(b, len); |
620 | rsa->q = getmp(b, len); |
621 | |
622 | if (!rsa->modulus || !rsa->exponent || !rsa->private_exponent || |
623 | !rsa->iqmp || !rsa->p || !rsa->q) { |
624 | sfree(rsa->modulus); |
625 | sfree(rsa->exponent); |
626 | sfree(rsa->private_exponent); |
627 | sfree(rsa->iqmp); |
628 | sfree(rsa->p); |
629 | sfree(rsa->q); |
630 | sfree(rsa); |
631 | return NULL; |
632 | } |
633 | |
634 | return rsa; |
635 | } |
636 | |
32874aea |
637 | static int rsa2_openssh_fmtkey(void *key, unsigned char *blob, int len) |
638 | { |
639 | struct RSAKey *rsa = (struct RSAKey *) key; |
ddecd643 |
640 | int bloblen, i; |
641 | |
642 | bloblen = |
643 | ssh2_bignum_length(rsa->modulus) + |
644 | ssh2_bignum_length(rsa->exponent) + |
645 | ssh2_bignum_length(rsa->private_exponent) + |
646 | ssh2_bignum_length(rsa->iqmp) + |
32874aea |
647 | ssh2_bignum_length(rsa->p) + ssh2_bignum_length(rsa->q); |
ddecd643 |
648 | |
649 | if (bloblen > len) |
650 | return bloblen; |
651 | |
652 | bloblen = 0; |
653 | #define ENC(x) \ |
654 | PUT_32BIT(blob+bloblen, ssh2_bignum_length((x))-4); bloblen += 4; \ |
655 | for (i = ssh2_bignum_length((x))-4; i-- ;) blob[bloblen++]=bignum_byte((x),i); |
656 | ENC(rsa->modulus); |
657 | ENC(rsa->exponent); |
658 | ENC(rsa->private_exponent); |
659 | ENC(rsa->iqmp); |
660 | ENC(rsa->p); |
661 | ENC(rsa->q); |
662 | |
663 | return bloblen; |
664 | } |
665 | |
47a6b94c |
666 | static int rsa2_pubkey_bits(void *blob, int len) |
667 | { |
668 | struct RSAKey *rsa; |
669 | int ret; |
670 | |
671 | rsa = rsa2_newkey((char *) blob, len); |
672 | ret = bignum_bitcount(rsa->modulus); |
673 | rsa2_freekey(rsa); |
674 | |
675 | return ret; |
676 | } |
677 | |
32874aea |
678 | static char *rsa2_fingerprint(void *key) |
679 | { |
680 | struct RSAKey *rsa = (struct RSAKey *) key; |
85cc02bb |
681 | struct MD5Context md5c; |
682 | unsigned char digest[16], lenbuf[4]; |
32874aea |
683 | char buffer[16 * 3 + 40]; |
85cc02bb |
684 | char *ret; |
685 | int numlen, i; |
686 | |
687 | MD5Init(&md5c); |
9bf430c9 |
688 | MD5Update(&md5c, (unsigned char *)"\0\0\0\7ssh-rsa", 11); |
85cc02bb |
689 | |
690 | #define ADD_BIGNUM(bignum) \ |
ddecd643 |
691 | numlen = (bignum_bitcount(bignum)+8)/8; \ |
85cc02bb |
692 | PUT_32BIT(lenbuf, numlen); MD5Update(&md5c, lenbuf, 4); \ |
693 | for (i = numlen; i-- ;) { \ |
694 | unsigned char c = bignum_byte(bignum, i); \ |
695 | MD5Update(&md5c, &c, 1); \ |
696 | } |
697 | ADD_BIGNUM(rsa->exponent); |
698 | ADD_BIGNUM(rsa->modulus); |
699 | #undef ADD_BIGNUM |
700 | |
701 | MD5Final(digest, &md5c); |
702 | |
ddecd643 |
703 | sprintf(buffer, "ssh-rsa %d ", bignum_bitcount(rsa->modulus)); |
85cc02bb |
704 | for (i = 0; i < 16; i++) |
32874aea |
705 | sprintf(buffer + strlen(buffer), "%s%02x", i ? ":" : "", |
706 | digest[i]); |
3d88e64d |
707 | ret = snewn(strlen(buffer) + 1, char); |
85cc02bb |
708 | if (ret) |
32874aea |
709 | strcpy(ret, buffer); |
85cc02bb |
710 | return ret; |
711 | } |
712 | |
713 | /* |
714 | * This is the magic ASN.1/DER prefix that goes in the decoded |
715 | * signature, between the string of FFs and the actual SHA hash |
96a73db9 |
716 | * value. The meaning of it is: |
85cc02bb |
717 | * |
718 | * 00 -- this marks the end of the FFs; not part of the ASN.1 bit itself |
719 | * |
720 | * 30 21 -- a constructed SEQUENCE of length 0x21 |
721 | * 30 09 -- a constructed sub-SEQUENCE of length 9 |
722 | * 06 05 -- an object identifier, length 5 |
96a73db9 |
723 | * 2B 0E 03 02 1A -- object id { 1 3 14 3 2 26 } |
724 | * (the 1,3 comes from 0x2B = 43 = 40*1+3) |
85cc02bb |
725 | * 05 00 -- NULL |
726 | * 04 14 -- a primitive OCTET STRING of length 0x14 |
727 | * [0x14 bytes of hash data follows] |
96a73db9 |
728 | * |
729 | * The object id in the middle there is listed as `id-sha1' in |
730 | * ftp://ftp.rsasecurity.com/pub/pkcs/pkcs-1/pkcs-1v2-1d2.asn (the |
731 | * ASN module for PKCS #1) and its expanded form is as follows: |
732 | * |
733 | * id-sha1 OBJECT IDENTIFIER ::= { |
734 | * iso(1) identified-organization(3) oiw(14) secsig(3) |
735 | * algorithms(2) 26 } |
85cc02bb |
736 | */ |
b5864f2c |
737 | static const unsigned char asn1_weird_stuff[] = { |
32874aea |
738 | 0x00, 0x30, 0x21, 0x30, 0x09, 0x06, 0x05, 0x2B, |
739 | 0x0E, 0x03, 0x02, 0x1A, 0x05, 0x00, 0x04, 0x14, |
85cc02bb |
740 | }; |
741 | |
d8770b12 |
742 | #define ASN1_LEN ( (int) sizeof(asn1_weird_stuff) ) |
743 | |
85cc02bb |
744 | static int rsa2_verifysig(void *key, char *sig, int siglen, |
32874aea |
745 | char *data, int datalen) |
746 | { |
747 | struct RSAKey *rsa = (struct RSAKey *) key; |
85cc02bb |
748 | Bignum in, out; |
749 | char *p; |
750 | int slen; |
751 | int bytes, i, j, ret; |
752 | unsigned char hash[20]; |
753 | |
754 | getstring(&sig, &siglen, &p, &slen); |
755 | if (!p || slen != 7 || memcmp(p, "ssh-rsa", 7)) { |
32874aea |
756 | return 0; |
85cc02bb |
757 | } |
758 | in = getmp(&sig, &siglen); |
759 | out = modpow(in, rsa->exponent, rsa->modulus); |
760 | freebn(in); |
761 | |
762 | ret = 1; |
763 | |
7bd33644 |
764 | bytes = (bignum_bitcount(rsa->modulus)+7) / 8; |
85cc02bb |
765 | /* Top (partial) byte should be zero. */ |
32874aea |
766 | if (bignum_byte(out, bytes - 1) != 0) |
767 | ret = 0; |
85cc02bb |
768 | /* First whole byte should be 1. */ |
32874aea |
769 | if (bignum_byte(out, bytes - 2) != 1) |
770 | ret = 0; |
85cc02bb |
771 | /* Most of the rest should be FF. */ |
32874aea |
772 | for (i = bytes - 3; i >= 20 + ASN1_LEN; i--) { |
773 | if (bignum_byte(out, i) != 0xFF) |
774 | ret = 0; |
85cc02bb |
775 | } |
776 | /* Then we expect to see the asn1_weird_stuff. */ |
32874aea |
777 | for (i = 20 + ASN1_LEN - 1, j = 0; i >= 20; i--, j++) { |
778 | if (bignum_byte(out, i) != asn1_weird_stuff[j]) |
779 | ret = 0; |
85cc02bb |
780 | } |
781 | /* Finally, we expect to see the SHA-1 hash of the signed data. */ |
782 | SHA_Simple(data, datalen, hash); |
32874aea |
783 | for (i = 19, j = 0; i >= 0; i--, j++) { |
784 | if (bignum_byte(out, i) != hash[j]) |
785 | ret = 0; |
85cc02bb |
786 | } |
679539d7 |
787 | freebn(out); |
85cc02bb |
788 | |
789 | return ret; |
790 | } |
791 | |
164feb13 |
792 | static unsigned char *rsa2_sign(void *key, char *data, int datalen, |
793 | int *siglen) |
32874aea |
794 | { |
795 | struct RSAKey *rsa = (struct RSAKey *) key; |
65a22376 |
796 | unsigned char *bytes; |
797 | int nbytes; |
798 | unsigned char hash[20]; |
799 | Bignum in, out; |
800 | int i, j; |
801 | |
802 | SHA_Simple(data, datalen, hash); |
803 | |
32874aea |
804 | nbytes = (bignum_bitcount(rsa->modulus) - 1) / 8; |
3d88e64d |
805 | bytes = snewn(nbytes, unsigned char); |
65a22376 |
806 | |
807 | bytes[0] = 1; |
32874aea |
808 | for (i = 1; i < nbytes - 20 - ASN1_LEN; i++) |
65a22376 |
809 | bytes[i] = 0xFF; |
32874aea |
810 | for (i = nbytes - 20 - ASN1_LEN, j = 0; i < nbytes - 20; i++, j++) |
65a22376 |
811 | bytes[i] = asn1_weird_stuff[j]; |
32874aea |
812 | for (i = nbytes - 20, j = 0; i < nbytes; i++, j++) |
65a22376 |
813 | bytes[i] = hash[j]; |
814 | |
815 | in = bignum_from_bytes(bytes, nbytes); |
816 | sfree(bytes); |
817 | |
8671a580 |
818 | out = rsa_privkey_op(in, rsa); |
65a22376 |
819 | freebn(in); |
820 | |
32874aea |
821 | nbytes = (bignum_bitcount(out) + 7) / 8; |
3d88e64d |
822 | bytes = snewn(4 + 7 + 4 + nbytes, unsigned char); |
65a22376 |
823 | PUT_32BIT(bytes, 7); |
32874aea |
824 | memcpy(bytes + 4, "ssh-rsa", 7); |
825 | PUT_32BIT(bytes + 4 + 7, nbytes); |
65a22376 |
826 | for (i = 0; i < nbytes; i++) |
32874aea |
827 | bytes[4 + 7 + 4 + i] = bignum_byte(out, nbytes - 1 - i); |
65a22376 |
828 | freebn(out); |
829 | |
32874aea |
830 | *siglen = 4 + 7 + 4 + nbytes; |
65a22376 |
831 | return bytes; |
85cc02bb |
832 | } |
833 | |
65a22376 |
834 | const struct ssh_signkey ssh_rsa = { |
85cc02bb |
835 | rsa2_newkey, |
836 | rsa2_freekey, |
837 | rsa2_fmtkey, |
65a22376 |
838 | rsa2_public_blob, |
839 | rsa2_private_blob, |
840 | rsa2_createkey, |
45cebe79 |
841 | rsa2_openssh_createkey, |
ddecd643 |
842 | rsa2_openssh_fmtkey, |
47a6b94c |
843 | rsa2_pubkey_bits, |
85cc02bb |
844 | rsa2_fingerprint, |
845 | rsa2_verifysig, |
846 | rsa2_sign, |
847 | "ssh-rsa", |
848 | "rsa2" |
849 | }; |