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