374330e2 |
1 | /* |
2 | * RSA implementation just sufficient for ssh client-side |
3 | * initialisation step |
4644b0ce |
4 | * |
5 | * Rewritten for more speed by Joris van Rantwijk, Jun 1999. |
374330e2 |
6 | */ |
7 | |
374330e2 |
8 | #include <stdio.h> |
9 | #include <stdlib.h> |
10 | #include <string.h> |
65a22376 |
11 | #include <assert.h> |
374330e2 |
12 | |
e5574168 |
13 | #include "ssh.h" |
8365990c |
14 | #include "misc.h" |
374330e2 |
15 | |
3f2d010c |
16 | #define GET_32BIT(cp) \ |
17 | (((unsigned long)(unsigned char)(cp)[0] << 24) | \ |
18 | ((unsigned long)(unsigned char)(cp)[1] << 16) | \ |
19 | ((unsigned long)(unsigned char)(cp)[2] << 8) | \ |
20 | ((unsigned long)(unsigned char)(cp)[3])) |
21 | |
22 | #define PUT_32BIT(cp, value) { \ |
23 | (cp)[0] = (unsigned char)((value) >> 24); \ |
24 | (cp)[1] = (unsigned char)((value) >> 16); \ |
25 | (cp)[2] = (unsigned char)((value) >> 8); \ |
26 | (cp)[3] = (unsigned char)(value); } |
1c2a93c4 |
27 | |
374330e2 |
28 | int makekey(unsigned char *data, struct RSAKey *result, |
32874aea |
29 | unsigned char **keystr, int order) |
30 | { |
374330e2 |
31 | unsigned char *p = data; |
7cca0d81 |
32 | int i; |
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 | |
7cca0d81 |
41 | /* |
42 | * order=0 means exponent then modulus (the keys sent by the |
43 | * server). order=1 means modulus then exponent (the keys |
44 | * stored in a keyfile). |
45 | */ |
374330e2 |
46 | |
7cca0d81 |
47 | if (order == 0) |
32874aea |
48 | p += ssh1_read_bignum(p, result ? &result->exponent : NULL); |
a52f067e |
49 | if (result) |
32874aea |
50 | result->bytes = (((p[0] << 8) + p[1]) + 7) / 8; |
51 | if (keystr) |
52 | *keystr = p + 2; |
a52f067e |
53 | p += ssh1_read_bignum(p, result ? &result->modulus : NULL); |
7cca0d81 |
54 | if (order == 1) |
32874aea |
55 | p += ssh1_read_bignum(p, result ? &result->exponent : NULL); |
374330e2 |
56 | |
57 | return p - data; |
58 | } |
59 | |
32874aea |
60 | int makeprivate(unsigned char *data, struct RSAKey *result) |
61 | { |
7cca0d81 |
62 | return ssh1_read_bignum(data, &result->private_exponent); |
63 | } |
64 | |
32874aea |
65 | void rsaencrypt(unsigned char *data, int length, struct RSAKey *key) |
66 | { |
374330e2 |
67 | Bignum b1, b2; |
3709bfe9 |
68 | int i; |
374330e2 |
69 | unsigned char *p; |
70 | |
32874aea |
71 | memmove(data + key->bytes - length, data, length); |
374330e2 |
72 | data[0] = 0; |
73 | data[1] = 2; |
74 | |
32874aea |
75 | for (i = 2; i < key->bytes - length - 1; i++) { |
374330e2 |
76 | do { |
77 | data[i] = random_byte(); |
78 | } while (data[i] == 0); |
79 | } |
32874aea |
80 | data[key->bytes - length - 1] = 0; |
374330e2 |
81 | |
3709bfe9 |
82 | b1 = bignum_from_bytes(data, key->bytes); |
374330e2 |
83 | |
59600f67 |
84 | b2 = modpow(b1, key->exponent, key->modulus); |
374330e2 |
85 | |
374330e2 |
86 | p = data; |
32874aea |
87 | for (i = key->bytes; i--;) { |
88 | *p++ = bignum_byte(b2, i); |
374330e2 |
89 | } |
90 | |
91 | freebn(b1); |
92 | freebn(b2); |
93 | } |
94 | |
32874aea |
95 | Bignum rsadecrypt(Bignum input, struct RSAKey *key) |
96 | { |
7cca0d81 |
97 | Bignum ret; |
59600f67 |
98 | ret = modpow(input, key->private_exponent, key->modulus); |
7cca0d81 |
99 | return ret; |
100 | } |
101 | |
32874aea |
102 | int rsastr_len(struct RSAKey *key) |
103 | { |
374330e2 |
104 | Bignum md, ex; |
3709bfe9 |
105 | int mdlen, exlen; |
374330e2 |
106 | |
107 | md = key->modulus; |
108 | ex = key->exponent; |
32874aea |
109 | mdlen = (bignum_bitcount(md) + 15) / 16; |
110 | exlen = (bignum_bitcount(ex) + 15) / 16; |
111 | return 4 * (mdlen + exlen) + 20; |
374330e2 |
112 | } |
113 | |
32874aea |
114 | void rsastr_fmt(char *str, struct RSAKey *key) |
115 | { |
374330e2 |
116 | Bignum md, ex; |
d5859615 |
117 | int len = 0, i, nibbles; |
118 | static const char hex[] = "0123456789abcdef"; |
374330e2 |
119 | |
120 | md = key->modulus; |
121 | ex = key->exponent; |
122 | |
32874aea |
123 | len += sprintf(str + len, "0x"); |
d5859615 |
124 | |
32874aea |
125 | nibbles = (3 + bignum_bitcount(ex)) / 4; |
126 | if (nibbles < 1) |
127 | nibbles = 1; |
128 | for (i = nibbles; i--;) |
129 | str[len++] = hex[(bignum_byte(ex, i / 2) >> (4 * (i % 2))) & 0xF]; |
d5859615 |
130 | |
32874aea |
131 | len += sprintf(str + len, ",0x"); |
d5859615 |
132 | |
32874aea |
133 | nibbles = (3 + bignum_bitcount(md)) / 4; |
134 | if (nibbles < 1) |
135 | nibbles = 1; |
136 | for (i = nibbles; i--;) |
137 | str[len++] = hex[(bignum_byte(md, i / 2) >> (4 * (i % 2))) & 0xF]; |
d5859615 |
138 | |
374330e2 |
139 | str[len] = '\0'; |
140 | } |
141 | |
1c2a93c4 |
142 | /* |
143 | * Generate a fingerprint string for the key. Compatible with the |
144 | * OpenSSH fingerprint code. |
145 | */ |
32874aea |
146 | void rsa_fingerprint(char *str, int len, struct RSAKey *key) |
147 | { |
1c2a93c4 |
148 | struct MD5Context md5c; |
149 | unsigned char digest[16]; |
32874aea |
150 | char buffer[16 * 3 + 40]; |
1c2a93c4 |
151 | int numlen, slen, i; |
152 | |
153 | MD5Init(&md5c); |
154 | numlen = ssh1_bignum_length(key->modulus) - 2; |
32874aea |
155 | for (i = numlen; i--;) { |
156 | unsigned char c = bignum_byte(key->modulus, i); |
157 | MD5Update(&md5c, &c, 1); |
1c2a93c4 |
158 | } |
159 | numlen = ssh1_bignum_length(key->exponent) - 2; |
32874aea |
160 | for (i = numlen; i--;) { |
161 | unsigned char c = bignum_byte(key->exponent, i); |
162 | MD5Update(&md5c, &c, 1); |
1c2a93c4 |
163 | } |
164 | MD5Final(digest, &md5c); |
165 | |
ddecd643 |
166 | sprintf(buffer, "%d ", bignum_bitcount(key->modulus)); |
1c2a93c4 |
167 | for (i = 0; i < 16; i++) |
32874aea |
168 | sprintf(buffer + strlen(buffer), "%s%02x", i ? ":" : "", |
169 | digest[i]); |
170 | strncpy(str, buffer, len); |
171 | str[len - 1] = '\0'; |
1c2a93c4 |
172 | slen = strlen(str); |
32874aea |
173 | if (key->comment && slen < len - 1) { |
174 | str[slen] = ' '; |
175 | strncpy(str + slen + 1, key->comment, len - slen - 1); |
176 | str[len - 1] = '\0'; |
1c2a93c4 |
177 | } |
178 | } |
179 | |
98f022f5 |
180 | /* |
181 | * Verify that the public data in an RSA key matches the private |
60fe6ff7 |
182 | * data. We also check the private data itself: we ensure that p > |
183 | * q and that iqmp really is the inverse of q mod p. |
98f022f5 |
184 | */ |
32874aea |
185 | int rsa_verify(struct RSAKey *key) |
186 | { |
60fe6ff7 |
187 | Bignum n, ed, pm1, qm1; |
98f022f5 |
188 | int cmp; |
189 | |
190 | /* n must equal pq. */ |
191 | n = bigmul(key->p, key->q); |
192 | cmp = bignum_cmp(n, key->modulus); |
193 | freebn(n); |
194 | if (cmp != 0) |
195 | return 0; |
196 | |
60fe6ff7 |
197 | /* e * d must be congruent to 1, modulo (p-1) and modulo (q-1). */ |
98f022f5 |
198 | pm1 = copybn(key->p); |
199 | decbn(pm1); |
60fe6ff7 |
200 | ed = modmul(key->exponent, key->private_exponent, pm1); |
201 | cmp = bignum_cmp(ed, One); |
202 | sfree(ed); |
203 | if (cmp != 0) |
204 | return 0; |
205 | |
98f022f5 |
206 | qm1 = copybn(key->q); |
207 | decbn(qm1); |
60fe6ff7 |
208 | ed = modmul(key->exponent, key->private_exponent, qm1); |
98f022f5 |
209 | cmp = bignum_cmp(ed, One); |
210 | sfree(ed); |
211 | if (cmp != 0) |
212 | return 0; |
014970c8 |
213 | |
60fe6ff7 |
214 | /* |
215 | * Ensure p > q. |
216 | */ |
217 | if (bignum_cmp(key->p, key->q) <= 0) |
32874aea |
218 | return 0; |
60fe6ff7 |
219 | |
220 | /* |
221 | * Ensure iqmp * q is congruent to 1, modulo p. |
222 | */ |
223 | n = modmul(key->iqmp, key->q, key->p); |
224 | cmp = bignum_cmp(n, One); |
225 | sfree(n); |
226 | if (cmp != 0) |
32874aea |
227 | return 0; |
60fe6ff7 |
228 | |
014970c8 |
229 | return 1; |
98f022f5 |
230 | } |
231 | |
3f2d010c |
232 | /* Public key blob as used by Pageant: exponent before modulus. */ |
233 | unsigned char *rsa_public_blob(struct RSAKey *key, int *len) |
234 | { |
235 | int length, pos; |
236 | unsigned char *ret; |
237 | |
238 | length = (ssh1_bignum_length(key->modulus) + |
239 | ssh1_bignum_length(key->exponent) + 4); |
240 | ret = smalloc(length); |
241 | |
242 | PUT_32BIT(ret, bignum_bitcount(key->modulus)); |
243 | pos = 4; |
244 | pos += ssh1_write_bignum(ret + pos, key->exponent); |
245 | pos += ssh1_write_bignum(ret + pos, key->modulus); |
246 | |
247 | *len = length; |
248 | return ret; |
249 | } |
250 | |
251 | /* Given a public blob, determine its length. */ |
252 | int rsa_public_blob_len(void *data) |
253 | { |
254 | unsigned char *p = (unsigned char *)data; |
3f2d010c |
255 | |
256 | p += 4; /* length word */ |
257 | p += ssh1_read_bignum(p, NULL); /* exponent */ |
258 | p += ssh1_read_bignum(p, NULL); /* modulus */ |
259 | |
260 | return p - (unsigned char *)data; |
261 | } |
262 | |
32874aea |
263 | void freersakey(struct RSAKey *key) |
264 | { |
265 | if (key->modulus) |
266 | freebn(key->modulus); |
267 | if (key->exponent) |
268 | freebn(key->exponent); |
269 | if (key->private_exponent) |
270 | freebn(key->private_exponent); |
271 | if (key->comment) |
272 | sfree(key->comment); |
5c58ad2d |
273 | } |
85cc02bb |
274 | |
275 | /* ---------------------------------------------------------------------- |
276 | * Implementation of the ssh-rsa signing key type. |
277 | */ |
278 | |
32874aea |
279 | static void getstring(char **data, int *datalen, char **p, int *length) |
280 | { |
85cc02bb |
281 | *p = NULL; |
282 | if (*datalen < 4) |
32874aea |
283 | return; |
85cc02bb |
284 | *length = GET_32BIT(*data); |
32874aea |
285 | *datalen -= 4; |
286 | *data += 4; |
85cc02bb |
287 | if (*datalen < *length) |
32874aea |
288 | return; |
85cc02bb |
289 | *p = *data; |
32874aea |
290 | *data += *length; |
291 | *datalen -= *length; |
85cc02bb |
292 | } |
32874aea |
293 | static Bignum getmp(char **data, int *datalen) |
294 | { |
85cc02bb |
295 | char *p; |
296 | int length; |
297 | Bignum b; |
298 | |
299 | getstring(data, datalen, &p, &length); |
300 | if (!p) |
32874aea |
301 | return NULL; |
9bf430c9 |
302 | b = bignum_from_bytes((unsigned char *)p, length); |
85cc02bb |
303 | return b; |
304 | } |
305 | |
32874aea |
306 | static void *rsa2_newkey(char *data, int len) |
307 | { |
85cc02bb |
308 | char *p; |
309 | int slen; |
310 | struct RSAKey *rsa; |
311 | |
312 | rsa = smalloc(sizeof(struct RSAKey)); |
32874aea |
313 | if (!rsa) |
314 | return NULL; |
85cc02bb |
315 | getstring(&data, &len, &p, &slen); |
316 | |
45cebe79 |
317 | if (!p || slen != 7 || memcmp(p, "ssh-rsa", 7)) { |
85cc02bb |
318 | sfree(rsa); |
319 | return NULL; |
320 | } |
321 | rsa->exponent = getmp(&data, &len); |
322 | rsa->modulus = getmp(&data, &len); |
323 | rsa->private_exponent = NULL; |
324 | rsa->comment = NULL; |
325 | |
326 | return rsa; |
327 | } |
328 | |
32874aea |
329 | static void rsa2_freekey(void *key) |
330 | { |
331 | struct RSAKey *rsa = (struct RSAKey *) key; |
85cc02bb |
332 | freersakey(rsa); |
333 | sfree(rsa); |
334 | } |
335 | |
32874aea |
336 | static char *rsa2_fmtkey(void *key) |
337 | { |
338 | struct RSAKey *rsa = (struct RSAKey *) key; |
85cc02bb |
339 | char *p; |
340 | int len; |
32874aea |
341 | |
85cc02bb |
342 | len = rsastr_len(rsa); |
343 | p = smalloc(len); |
32874aea |
344 | rsastr_fmt(p, rsa); |
85cc02bb |
345 | return p; |
346 | } |
347 | |
32874aea |
348 | static unsigned char *rsa2_public_blob(void *key, int *len) |
349 | { |
350 | struct RSAKey *rsa = (struct RSAKey *) key; |
65a22376 |
351 | int elen, mlen, bloblen; |
352 | int i; |
353 | unsigned char *blob, *p; |
354 | |
32874aea |
355 | elen = (bignum_bitcount(rsa->exponent) + 8) / 8; |
356 | mlen = (bignum_bitcount(rsa->modulus) + 8) / 8; |
65a22376 |
357 | |
358 | /* |
359 | * string "ssh-rsa", mpint exp, mpint mod. Total 19+elen+mlen. |
360 | * (three length fields, 12+7=19). |
361 | */ |
32874aea |
362 | bloblen = 19 + elen + mlen; |
65a22376 |
363 | blob = smalloc(bloblen); |
364 | p = blob; |
32874aea |
365 | PUT_32BIT(p, 7); |
366 | p += 4; |
367 | memcpy(p, "ssh-rsa", 7); |
368 | p += 7; |
369 | PUT_32BIT(p, elen); |
370 | p += 4; |
371 | for (i = elen; i--;) |
372 | *p++ = bignum_byte(rsa->exponent, i); |
373 | PUT_32BIT(p, mlen); |
374 | p += 4; |
375 | for (i = mlen; i--;) |
376 | *p++ = bignum_byte(rsa->modulus, i); |
65a22376 |
377 | assert(p == blob + bloblen); |
378 | *len = bloblen; |
379 | return blob; |
380 | } |
381 | |
32874aea |
382 | static unsigned char *rsa2_private_blob(void *key, int *len) |
383 | { |
384 | struct RSAKey *rsa = (struct RSAKey *) key; |
65a22376 |
385 | int dlen, plen, qlen, ulen, bloblen; |
386 | int i; |
387 | unsigned char *blob, *p; |
388 | |
32874aea |
389 | dlen = (bignum_bitcount(rsa->private_exponent) + 8) / 8; |
390 | plen = (bignum_bitcount(rsa->p) + 8) / 8; |
391 | qlen = (bignum_bitcount(rsa->q) + 8) / 8; |
392 | ulen = (bignum_bitcount(rsa->iqmp) + 8) / 8; |
65a22376 |
393 | |
394 | /* |
395 | * mpint private_exp, mpint p, mpint q, mpint iqmp. Total 16 + |
396 | * sum of lengths. |
397 | */ |
32874aea |
398 | bloblen = 16 + dlen + plen + qlen + ulen; |
65a22376 |
399 | blob = smalloc(bloblen); |
400 | p = blob; |
32874aea |
401 | PUT_32BIT(p, dlen); |
402 | p += 4; |
403 | for (i = dlen; i--;) |
404 | *p++ = bignum_byte(rsa->private_exponent, i); |
405 | PUT_32BIT(p, plen); |
406 | p += 4; |
407 | for (i = plen; i--;) |
408 | *p++ = bignum_byte(rsa->p, i); |
409 | PUT_32BIT(p, qlen); |
410 | p += 4; |
411 | for (i = qlen; i--;) |
412 | *p++ = bignum_byte(rsa->q, i); |
413 | PUT_32BIT(p, ulen); |
414 | p += 4; |
415 | for (i = ulen; i--;) |
416 | *p++ = bignum_byte(rsa->iqmp, i); |
65a22376 |
417 | assert(p == blob + bloblen); |
418 | *len = bloblen; |
419 | return blob; |
420 | } |
421 | |
422 | static void *rsa2_createkey(unsigned char *pub_blob, int pub_len, |
32874aea |
423 | unsigned char *priv_blob, int priv_len) |
424 | { |
65a22376 |
425 | struct RSAKey *rsa; |
32874aea |
426 | char *pb = (char *) priv_blob; |
427 | |
428 | rsa = rsa2_newkey((char *) pub_blob, pub_len); |
65a22376 |
429 | rsa->private_exponent = getmp(&pb, &priv_len); |
430 | rsa->p = getmp(&pb, &priv_len); |
431 | rsa->q = getmp(&pb, &priv_len); |
432 | rsa->iqmp = getmp(&pb, &priv_len); |
433 | |
98f022f5 |
434 | if (!rsa_verify(rsa)) { |
435 | rsa2_freekey(rsa); |
436 | return NULL; |
437 | } |
438 | |
65a22376 |
439 | return rsa; |
440 | } |
441 | |
32874aea |
442 | static void *rsa2_openssh_createkey(unsigned char **blob, int *len) |
443 | { |
444 | char **b = (char **) blob; |
45cebe79 |
445 | struct RSAKey *rsa; |
45cebe79 |
446 | |
447 | rsa = smalloc(sizeof(struct RSAKey)); |
32874aea |
448 | if (!rsa) |
449 | return NULL; |
45cebe79 |
450 | rsa->comment = NULL; |
451 | |
452 | rsa->modulus = getmp(b, len); |
453 | rsa->exponent = getmp(b, len); |
454 | rsa->private_exponent = getmp(b, len); |
455 | rsa->iqmp = getmp(b, len); |
456 | rsa->p = getmp(b, len); |
457 | rsa->q = getmp(b, len); |
458 | |
459 | if (!rsa->modulus || !rsa->exponent || !rsa->private_exponent || |
460 | !rsa->iqmp || !rsa->p || !rsa->q) { |
461 | sfree(rsa->modulus); |
462 | sfree(rsa->exponent); |
463 | sfree(rsa->private_exponent); |
464 | sfree(rsa->iqmp); |
465 | sfree(rsa->p); |
466 | sfree(rsa->q); |
467 | sfree(rsa); |
468 | return NULL; |
469 | } |
470 | |
471 | return rsa; |
472 | } |
473 | |
32874aea |
474 | static int rsa2_openssh_fmtkey(void *key, unsigned char *blob, int len) |
475 | { |
476 | struct RSAKey *rsa = (struct RSAKey *) key; |
ddecd643 |
477 | int bloblen, i; |
478 | |
479 | bloblen = |
480 | ssh2_bignum_length(rsa->modulus) + |
481 | ssh2_bignum_length(rsa->exponent) + |
482 | ssh2_bignum_length(rsa->private_exponent) + |
483 | ssh2_bignum_length(rsa->iqmp) + |
32874aea |
484 | ssh2_bignum_length(rsa->p) + ssh2_bignum_length(rsa->q); |
ddecd643 |
485 | |
486 | if (bloblen > len) |
487 | return bloblen; |
488 | |
489 | bloblen = 0; |
490 | #define ENC(x) \ |
491 | PUT_32BIT(blob+bloblen, ssh2_bignum_length((x))-4); bloblen += 4; \ |
492 | for (i = ssh2_bignum_length((x))-4; i-- ;) blob[bloblen++]=bignum_byte((x),i); |
493 | ENC(rsa->modulus); |
494 | ENC(rsa->exponent); |
495 | ENC(rsa->private_exponent); |
496 | ENC(rsa->iqmp); |
497 | ENC(rsa->p); |
498 | ENC(rsa->q); |
499 | |
500 | return bloblen; |
501 | } |
502 | |
32874aea |
503 | static char *rsa2_fingerprint(void *key) |
504 | { |
505 | struct RSAKey *rsa = (struct RSAKey *) key; |
85cc02bb |
506 | struct MD5Context md5c; |
507 | unsigned char digest[16], lenbuf[4]; |
32874aea |
508 | char buffer[16 * 3 + 40]; |
85cc02bb |
509 | char *ret; |
510 | int numlen, i; |
511 | |
512 | MD5Init(&md5c); |
9bf430c9 |
513 | MD5Update(&md5c, (unsigned char *)"\0\0\0\7ssh-rsa", 11); |
85cc02bb |
514 | |
515 | #define ADD_BIGNUM(bignum) \ |
ddecd643 |
516 | numlen = (bignum_bitcount(bignum)+8)/8; \ |
85cc02bb |
517 | PUT_32BIT(lenbuf, numlen); MD5Update(&md5c, lenbuf, 4); \ |
518 | for (i = numlen; i-- ;) { \ |
519 | unsigned char c = bignum_byte(bignum, i); \ |
520 | MD5Update(&md5c, &c, 1); \ |
521 | } |
522 | ADD_BIGNUM(rsa->exponent); |
523 | ADD_BIGNUM(rsa->modulus); |
524 | #undef ADD_BIGNUM |
525 | |
526 | MD5Final(digest, &md5c); |
527 | |
ddecd643 |
528 | sprintf(buffer, "ssh-rsa %d ", bignum_bitcount(rsa->modulus)); |
85cc02bb |
529 | for (i = 0; i < 16; i++) |
32874aea |
530 | sprintf(buffer + strlen(buffer), "%s%02x", i ? ":" : "", |
531 | digest[i]); |
532 | ret = smalloc(strlen(buffer) + 1); |
85cc02bb |
533 | if (ret) |
32874aea |
534 | strcpy(ret, buffer); |
85cc02bb |
535 | return ret; |
536 | } |
537 | |
538 | /* |
539 | * This is the magic ASN.1/DER prefix that goes in the decoded |
540 | * signature, between the string of FFs and the actual SHA hash |
96a73db9 |
541 | * value. The meaning of it is: |
85cc02bb |
542 | * |
543 | * 00 -- this marks the end of the FFs; not part of the ASN.1 bit itself |
544 | * |
545 | * 30 21 -- a constructed SEQUENCE of length 0x21 |
546 | * 30 09 -- a constructed sub-SEQUENCE of length 9 |
547 | * 06 05 -- an object identifier, length 5 |
96a73db9 |
548 | * 2B 0E 03 02 1A -- object id { 1 3 14 3 2 26 } |
549 | * (the 1,3 comes from 0x2B = 43 = 40*1+3) |
85cc02bb |
550 | * 05 00 -- NULL |
551 | * 04 14 -- a primitive OCTET STRING of length 0x14 |
552 | * [0x14 bytes of hash data follows] |
96a73db9 |
553 | * |
554 | * The object id in the middle there is listed as `id-sha1' in |
555 | * ftp://ftp.rsasecurity.com/pub/pkcs/pkcs-1/pkcs-1v2-1d2.asn (the |
556 | * ASN module for PKCS #1) and its expanded form is as follows: |
557 | * |
558 | * id-sha1 OBJECT IDENTIFIER ::= { |
559 | * iso(1) identified-organization(3) oiw(14) secsig(3) |
560 | * algorithms(2) 26 } |
85cc02bb |
561 | */ |
b5864f2c |
562 | static const unsigned char asn1_weird_stuff[] = { |
32874aea |
563 | 0x00, 0x30, 0x21, 0x30, 0x09, 0x06, 0x05, 0x2B, |
564 | 0x0E, 0x03, 0x02, 0x1A, 0x05, 0x00, 0x04, 0x14, |
85cc02bb |
565 | }; |
566 | |
d8770b12 |
567 | #define ASN1_LEN ( (int) sizeof(asn1_weird_stuff) ) |
568 | |
85cc02bb |
569 | static int rsa2_verifysig(void *key, char *sig, int siglen, |
32874aea |
570 | char *data, int datalen) |
571 | { |
572 | struct RSAKey *rsa = (struct RSAKey *) key; |
85cc02bb |
573 | Bignum in, out; |
574 | char *p; |
575 | int slen; |
576 | int bytes, i, j, ret; |
577 | unsigned char hash[20]; |
578 | |
579 | getstring(&sig, &siglen, &p, &slen); |
580 | if (!p || slen != 7 || memcmp(p, "ssh-rsa", 7)) { |
32874aea |
581 | return 0; |
85cc02bb |
582 | } |
583 | in = getmp(&sig, &siglen); |
584 | out = modpow(in, rsa->exponent, rsa->modulus); |
585 | freebn(in); |
586 | |
587 | ret = 1; |
588 | |
ddecd643 |
589 | bytes = bignum_bitcount(rsa->modulus) / 8; |
85cc02bb |
590 | /* Top (partial) byte should be zero. */ |
32874aea |
591 | if (bignum_byte(out, bytes - 1) != 0) |
592 | ret = 0; |
85cc02bb |
593 | /* First whole byte should be 1. */ |
32874aea |
594 | if (bignum_byte(out, bytes - 2) != 1) |
595 | ret = 0; |
85cc02bb |
596 | /* Most of the rest should be FF. */ |
32874aea |
597 | for (i = bytes - 3; i >= 20 + ASN1_LEN; i--) { |
598 | if (bignum_byte(out, i) != 0xFF) |
599 | ret = 0; |
85cc02bb |
600 | } |
601 | /* Then we expect to see the asn1_weird_stuff. */ |
32874aea |
602 | for (i = 20 + ASN1_LEN - 1, j = 0; i >= 20; i--, j++) { |
603 | if (bignum_byte(out, i) != asn1_weird_stuff[j]) |
604 | ret = 0; |
85cc02bb |
605 | } |
606 | /* Finally, we expect to see the SHA-1 hash of the signed data. */ |
607 | SHA_Simple(data, datalen, hash); |
32874aea |
608 | for (i = 19, j = 0; i >= 0; i--, j++) { |
609 | if (bignum_byte(out, i) != hash[j]) |
610 | ret = 0; |
85cc02bb |
611 | } |
612 | |
613 | return ret; |
614 | } |
615 | |
164feb13 |
616 | static unsigned char *rsa2_sign(void *key, char *data, int datalen, |
617 | int *siglen) |
32874aea |
618 | { |
619 | struct RSAKey *rsa = (struct RSAKey *) key; |
65a22376 |
620 | unsigned char *bytes; |
621 | int nbytes; |
622 | unsigned char hash[20]; |
623 | Bignum in, out; |
624 | int i, j; |
625 | |
626 | SHA_Simple(data, datalen, hash); |
627 | |
32874aea |
628 | nbytes = (bignum_bitcount(rsa->modulus) - 1) / 8; |
65a22376 |
629 | bytes = smalloc(nbytes); |
630 | |
631 | bytes[0] = 1; |
32874aea |
632 | for (i = 1; i < nbytes - 20 - ASN1_LEN; i++) |
65a22376 |
633 | bytes[i] = 0xFF; |
32874aea |
634 | for (i = nbytes - 20 - ASN1_LEN, j = 0; i < nbytes - 20; i++, j++) |
65a22376 |
635 | bytes[i] = asn1_weird_stuff[j]; |
32874aea |
636 | for (i = nbytes - 20, j = 0; i < nbytes; i++, j++) |
65a22376 |
637 | bytes[i] = hash[j]; |
638 | |
639 | in = bignum_from_bytes(bytes, nbytes); |
640 | sfree(bytes); |
641 | |
642 | out = modpow(in, rsa->private_exponent, rsa->modulus); |
643 | freebn(in); |
644 | |
32874aea |
645 | nbytes = (bignum_bitcount(out) + 7) / 8; |
646 | bytes = smalloc(4 + 7 + 4 + nbytes); |
65a22376 |
647 | PUT_32BIT(bytes, 7); |
32874aea |
648 | memcpy(bytes + 4, "ssh-rsa", 7); |
649 | PUT_32BIT(bytes + 4 + 7, nbytes); |
65a22376 |
650 | for (i = 0; i < nbytes; i++) |
32874aea |
651 | bytes[4 + 7 + 4 + i] = bignum_byte(out, nbytes - 1 - i); |
65a22376 |
652 | freebn(out); |
653 | |
32874aea |
654 | *siglen = 4 + 7 + 4 + nbytes; |
65a22376 |
655 | return bytes; |
85cc02bb |
656 | } |
657 | |
65a22376 |
658 | const struct ssh_signkey ssh_rsa = { |
85cc02bb |
659 | rsa2_newkey, |
660 | rsa2_freekey, |
661 | rsa2_fmtkey, |
65a22376 |
662 | rsa2_public_blob, |
663 | rsa2_private_blob, |
664 | rsa2_createkey, |
45cebe79 |
665 | rsa2_openssh_createkey, |
ddecd643 |
666 | rsa2_openssh_fmtkey, |
85cc02bb |
667 | rsa2_fingerprint, |
668 | rsa2_verifysig, |
669 | rsa2_sign, |
670 | "ssh-rsa", |
671 | "rsa2" |
672 | }; |