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sshrsa.c should include misc.h in case I need to do debugging :-)
[u/mdw/putty] / sshrsa.c
1 /*
2 * RSA implementation just sufficient for ssh client-side
3 * initialisation step
4 *
5 * Rewritten for more speed by Joris van Rantwijk, Jun 1999.
6 */
7
8 #include <stdio.h>
9 #include <stdlib.h>
10 #include <string.h>
11 #include <assert.h>
12
13 #include "ssh.h"
14 #include "misc.h"
15
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); }
27
28 int makekey(unsigned char *data, struct RSAKey *result,
29 unsigned char **keystr, int order)
30 {
31 unsigned char *p = data;
32 int i;
33
34 if (result) {
35 result->bits = 0;
36 for (i = 0; i < 4; i++)
37 result->bits = (result->bits << 8) + *p++;
38 } else
39 p += 4;
40
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 */
46
47 if (order == 0)
48 p += ssh1_read_bignum(p, result ? &result->exponent : NULL);
49 if (result)
50 result->bytes = (((p[0] << 8) + p[1]) + 7) / 8;
51 if (keystr)
52 *keystr = p + 2;
53 p += ssh1_read_bignum(p, result ? &result->modulus : NULL);
54 if (order == 1)
55 p += ssh1_read_bignum(p, result ? &result->exponent : NULL);
56
57 return p - data;
58 }
59
60 int makeprivate(unsigned char *data, struct RSAKey *result)
61 {
62 return ssh1_read_bignum(data, &result->private_exponent);
63 }
64
65 void rsaencrypt(unsigned char *data, int length, struct RSAKey *key)
66 {
67 Bignum b1, b2;
68 int i;
69 unsigned char *p;
70
71 memmove(data + key->bytes - length, data, length);
72 data[0] = 0;
73 data[1] = 2;
74
75 for (i = 2; i < key->bytes - length - 1; i++) {
76 do {
77 data[i] = random_byte();
78 } while (data[i] == 0);
79 }
80 data[key->bytes - length - 1] = 0;
81
82 b1 = bignum_from_bytes(data, key->bytes);
83
84 b2 = modpow(b1, key->exponent, key->modulus);
85
86 p = data;
87 for (i = key->bytes; i--;) {
88 *p++ = bignum_byte(b2, i);
89 }
90
91 freebn(b1);
92 freebn(b2);
93 }
94
95 Bignum rsadecrypt(Bignum input, struct RSAKey *key)
96 {
97 Bignum ret;
98 ret = modpow(input, key->private_exponent, key->modulus);
99 return ret;
100 }
101
102 int rsastr_len(struct RSAKey *key)
103 {
104 Bignum md, ex;
105 int mdlen, exlen;
106
107 md = key->modulus;
108 ex = key->exponent;
109 mdlen = (bignum_bitcount(md) + 15) / 16;
110 exlen = (bignum_bitcount(ex) + 15) / 16;
111 return 4 * (mdlen + exlen) + 20;
112 }
113
114 void rsastr_fmt(char *str, struct RSAKey *key)
115 {
116 Bignum md, ex;
117 int len = 0, i, nibbles;
118 static const char hex[] = "0123456789abcdef";
119
120 md = key->modulus;
121 ex = key->exponent;
122
123 len += sprintf(str + len, "0x");
124
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];
130
131 len += sprintf(str + len, ",0x");
132
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];
138
139 str[len] = '\0';
140 }
141
142 /*
143 * Generate a fingerprint string for the key. Compatible with the
144 * OpenSSH fingerprint code.
145 */
146 void rsa_fingerprint(char *str, int len, struct RSAKey *key)
147 {
148 struct MD5Context md5c;
149 unsigned char digest[16];
150 char buffer[16 * 3 + 40];
151 int numlen, slen, i;
152
153 MD5Init(&md5c);
154 numlen = ssh1_bignum_length(key->modulus) - 2;
155 for (i = numlen; i--;) {
156 unsigned char c = bignum_byte(key->modulus, i);
157 MD5Update(&md5c, &c, 1);
158 }
159 numlen = ssh1_bignum_length(key->exponent) - 2;
160 for (i = numlen; i--;) {
161 unsigned char c = bignum_byte(key->exponent, i);
162 MD5Update(&md5c, &c, 1);
163 }
164 MD5Final(digest, &md5c);
165
166 sprintf(buffer, "%d ", bignum_bitcount(key->modulus));
167 for (i = 0; i < 16; i++)
168 sprintf(buffer + strlen(buffer), "%s%02x", i ? ":" : "",
169 digest[i]);
170 strncpy(str, buffer, len);
171 str[len - 1] = '\0';
172 slen = strlen(str);
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';
177 }
178 }
179
180 /*
181 * Verify that the public data in an RSA key matches the private
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.
184 */
185 int rsa_verify(struct RSAKey *key)
186 {
187 Bignum n, ed, pm1, qm1;
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
197 /* e * d must be congruent to 1, modulo (p-1) and modulo (q-1). */
198 pm1 = copybn(key->p);
199 decbn(pm1);
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
206 qm1 = copybn(key->q);
207 decbn(qm1);
208 ed = modmul(key->exponent, key->private_exponent, qm1);
209 cmp = bignum_cmp(ed, One);
210 sfree(ed);
211 if (cmp != 0)
212 return 0;
213
214 /*
215 * Ensure p > q.
216 */
217 if (bignum_cmp(key->p, key->q) <= 0)
218 return 0;
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)
227 return 0;
228
229 return 1;
230 }
231
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;
255 int ret;
256
257 p += 4; /* length word */
258 p += ssh1_read_bignum(p, NULL); /* exponent */
259 p += ssh1_read_bignum(p, NULL); /* modulus */
260
261 return p - (unsigned char *)data;
262 }
263
264 void freersakey(struct RSAKey *key)
265 {
266 if (key->modulus)
267 freebn(key->modulus);
268 if (key->exponent)
269 freebn(key->exponent);
270 if (key->private_exponent)
271 freebn(key->private_exponent);
272 if (key->comment)
273 sfree(key->comment);
274 }
275
276 /* ----------------------------------------------------------------------
277 * Implementation of the ssh-rsa signing key type.
278 */
279
280 static void getstring(char **data, int *datalen, char **p, int *length)
281 {
282 *p = NULL;
283 if (*datalen < 4)
284 return;
285 *length = GET_32BIT(*data);
286 *datalen -= 4;
287 *data += 4;
288 if (*datalen < *length)
289 return;
290 *p = *data;
291 *data += *length;
292 *datalen -= *length;
293 }
294 static Bignum getmp(char **data, int *datalen)
295 {
296 char *p;
297 int length;
298 Bignum b;
299
300 getstring(data, datalen, &p, &length);
301 if (!p)
302 return NULL;
303 b = bignum_from_bytes(p, length);
304 return b;
305 }
306
307 static void *rsa2_newkey(char *data, int len)
308 {
309 char *p;
310 int slen;
311 struct RSAKey *rsa;
312
313 rsa = smalloc(sizeof(struct RSAKey));
314 if (!rsa)
315 return NULL;
316 getstring(&data, &len, &p, &slen);
317
318 if (!p || slen != 7 || memcmp(p, "ssh-rsa", 7)) {
319 sfree(rsa);
320 return NULL;
321 }
322 rsa->exponent = getmp(&data, &len);
323 rsa->modulus = getmp(&data, &len);
324 rsa->private_exponent = NULL;
325 rsa->comment = NULL;
326
327 return rsa;
328 }
329
330 static void rsa2_freekey(void *key)
331 {
332 struct RSAKey *rsa = (struct RSAKey *) key;
333 freersakey(rsa);
334 sfree(rsa);
335 }
336
337 static char *rsa2_fmtkey(void *key)
338 {
339 struct RSAKey *rsa = (struct RSAKey *) key;
340 char *p;
341 int len;
342
343 len = rsastr_len(rsa);
344 p = smalloc(len);
345 rsastr_fmt(p, rsa);
346 return p;
347 }
348
349 static unsigned char *rsa2_public_blob(void *key, int *len)
350 {
351 struct RSAKey *rsa = (struct RSAKey *) key;
352 int elen, mlen, bloblen;
353 int i;
354 unsigned char *blob, *p;
355
356 elen = (bignum_bitcount(rsa->exponent) + 8) / 8;
357 mlen = (bignum_bitcount(rsa->modulus) + 8) / 8;
358
359 /*
360 * string "ssh-rsa", mpint exp, mpint mod. Total 19+elen+mlen.
361 * (three length fields, 12+7=19).
362 */
363 bloblen = 19 + elen + mlen;
364 blob = smalloc(bloblen);
365 p = blob;
366 PUT_32BIT(p, 7);
367 p += 4;
368 memcpy(p, "ssh-rsa", 7);
369 p += 7;
370 PUT_32BIT(p, elen);
371 p += 4;
372 for (i = elen; i--;)
373 *p++ = bignum_byte(rsa->exponent, i);
374 PUT_32BIT(p, mlen);
375 p += 4;
376 for (i = mlen; i--;)
377 *p++ = bignum_byte(rsa->modulus, i);
378 assert(p == blob + bloblen);
379 *len = bloblen;
380 return blob;
381 }
382
383 static unsigned char *rsa2_private_blob(void *key, int *len)
384 {
385 struct RSAKey *rsa = (struct RSAKey *) key;
386 int dlen, plen, qlen, ulen, bloblen;
387 int i;
388 unsigned char *blob, *p;
389
390 dlen = (bignum_bitcount(rsa->private_exponent) + 8) / 8;
391 plen = (bignum_bitcount(rsa->p) + 8) / 8;
392 qlen = (bignum_bitcount(rsa->q) + 8) / 8;
393 ulen = (bignum_bitcount(rsa->iqmp) + 8) / 8;
394
395 /*
396 * mpint private_exp, mpint p, mpint q, mpint iqmp. Total 16 +
397 * sum of lengths.
398 */
399 bloblen = 16 + dlen + plen + qlen + ulen;
400 blob = smalloc(bloblen);
401 p = blob;
402 PUT_32BIT(p, dlen);
403 p += 4;
404 for (i = dlen; i--;)
405 *p++ = bignum_byte(rsa->private_exponent, i);
406 PUT_32BIT(p, plen);
407 p += 4;
408 for (i = plen; i--;)
409 *p++ = bignum_byte(rsa->p, i);
410 PUT_32BIT(p, qlen);
411 p += 4;
412 for (i = qlen; i--;)
413 *p++ = bignum_byte(rsa->q, i);
414 PUT_32BIT(p, ulen);
415 p += 4;
416 for (i = ulen; i--;)
417 *p++ = bignum_byte(rsa->iqmp, i);
418 assert(p == blob + bloblen);
419 *len = bloblen;
420 return blob;
421 }
422
423 static void *rsa2_createkey(unsigned char *pub_blob, int pub_len,
424 unsigned char *priv_blob, int priv_len)
425 {
426 struct RSAKey *rsa;
427 char *pb = (char *) priv_blob;
428
429 rsa = rsa2_newkey((char *) pub_blob, pub_len);
430 rsa->private_exponent = getmp(&pb, &priv_len);
431 rsa->p = getmp(&pb, &priv_len);
432 rsa->q = getmp(&pb, &priv_len);
433 rsa->iqmp = getmp(&pb, &priv_len);
434
435 if (!rsa_verify(rsa)) {
436 rsa2_freekey(rsa);
437 return NULL;
438 }
439
440 return rsa;
441 }
442
443 static void *rsa2_openssh_createkey(unsigned char **blob, int *len)
444 {
445 char **b = (char **) blob;
446 struct RSAKey *rsa;
447
448 rsa = smalloc(sizeof(struct RSAKey));
449 if (!rsa)
450 return NULL;
451 rsa->comment = NULL;
452
453 rsa->modulus = getmp(b, len);
454 rsa->exponent = getmp(b, len);
455 rsa->private_exponent = getmp(b, len);
456 rsa->iqmp = getmp(b, len);
457 rsa->p = getmp(b, len);
458 rsa->q = getmp(b, len);
459
460 if (!rsa->modulus || !rsa->exponent || !rsa->private_exponent ||
461 !rsa->iqmp || !rsa->p || !rsa->q) {
462 sfree(rsa->modulus);
463 sfree(rsa->exponent);
464 sfree(rsa->private_exponent);
465 sfree(rsa->iqmp);
466 sfree(rsa->p);
467 sfree(rsa->q);
468 sfree(rsa);
469 return NULL;
470 }
471
472 return rsa;
473 }
474
475 static int rsa2_openssh_fmtkey(void *key, unsigned char *blob, int len)
476 {
477 struct RSAKey *rsa = (struct RSAKey *) key;
478 int bloblen, i;
479
480 bloblen =
481 ssh2_bignum_length(rsa->modulus) +
482 ssh2_bignum_length(rsa->exponent) +
483 ssh2_bignum_length(rsa->private_exponent) +
484 ssh2_bignum_length(rsa->iqmp) +
485 ssh2_bignum_length(rsa->p) + ssh2_bignum_length(rsa->q);
486
487 if (bloblen > len)
488 return bloblen;
489
490 bloblen = 0;
491 #define ENC(x) \
492 PUT_32BIT(blob+bloblen, ssh2_bignum_length((x))-4); bloblen += 4; \
493 for (i = ssh2_bignum_length((x))-4; i-- ;) blob[bloblen++]=bignum_byte((x),i);
494 ENC(rsa->modulus);
495 ENC(rsa->exponent);
496 ENC(rsa->private_exponent);
497 ENC(rsa->iqmp);
498 ENC(rsa->p);
499 ENC(rsa->q);
500
501 return bloblen;
502 }
503
504 static char *rsa2_fingerprint(void *key)
505 {
506 struct RSAKey *rsa = (struct RSAKey *) key;
507 struct MD5Context md5c;
508 unsigned char digest[16], lenbuf[4];
509 char buffer[16 * 3 + 40];
510 char *ret;
511 int numlen, i;
512
513 MD5Init(&md5c);
514 MD5Update(&md5c, "\0\0\0\7ssh-rsa", 11);
515
516 #define ADD_BIGNUM(bignum) \
517 numlen = (bignum_bitcount(bignum)+8)/8; \
518 PUT_32BIT(lenbuf, numlen); MD5Update(&md5c, lenbuf, 4); \
519 for (i = numlen; i-- ;) { \
520 unsigned char c = bignum_byte(bignum, i); \
521 MD5Update(&md5c, &c, 1); \
522 }
523 ADD_BIGNUM(rsa->exponent);
524 ADD_BIGNUM(rsa->modulus);
525 #undef ADD_BIGNUM
526
527 MD5Final(digest, &md5c);
528
529 sprintf(buffer, "ssh-rsa %d ", bignum_bitcount(rsa->modulus));
530 for (i = 0; i < 16; i++)
531 sprintf(buffer + strlen(buffer), "%s%02x", i ? ":" : "",
532 digest[i]);
533 ret = smalloc(strlen(buffer) + 1);
534 if (ret)
535 strcpy(ret, buffer);
536 return ret;
537 }
538
539 /*
540 * This is the magic ASN.1/DER prefix that goes in the decoded
541 * signature, between the string of FFs and the actual SHA hash
542 * value. The meaning of it is:
543 *
544 * 00 -- this marks the end of the FFs; not part of the ASN.1 bit itself
545 *
546 * 30 21 -- a constructed SEQUENCE of length 0x21
547 * 30 09 -- a constructed sub-SEQUENCE of length 9
548 * 06 05 -- an object identifier, length 5
549 * 2B 0E 03 02 1A -- object id { 1 3 14 3 2 26 }
550 * (the 1,3 comes from 0x2B = 43 = 40*1+3)
551 * 05 00 -- NULL
552 * 04 14 -- a primitive OCTET STRING of length 0x14
553 * [0x14 bytes of hash data follows]
554 *
555 * The object id in the middle there is listed as `id-sha1' in
556 * ftp://ftp.rsasecurity.com/pub/pkcs/pkcs-1/pkcs-1v2-1d2.asn (the
557 * ASN module for PKCS #1) and its expanded form is as follows:
558 *
559 * id-sha1 OBJECT IDENTIFIER ::= {
560 * iso(1) identified-organization(3) oiw(14) secsig(3)
561 * algorithms(2) 26 }
562 */
563 static unsigned char asn1_weird_stuff[] = {
564 0x00, 0x30, 0x21, 0x30, 0x09, 0x06, 0x05, 0x2B,
565 0x0E, 0x03, 0x02, 0x1A, 0x05, 0x00, 0x04, 0x14,
566 };
567
568 #define ASN1_LEN ( (int) sizeof(asn1_weird_stuff) )
569
570 static int rsa2_verifysig(void *key, char *sig, int siglen,
571 char *data, int datalen)
572 {
573 struct RSAKey *rsa = (struct RSAKey *) key;
574 Bignum in, out;
575 char *p;
576 int slen;
577 int bytes, i, j, ret;
578 unsigned char hash[20];
579
580 getstring(&sig, &siglen, &p, &slen);
581 if (!p || slen != 7 || memcmp(p, "ssh-rsa", 7)) {
582 return 0;
583 }
584 in = getmp(&sig, &siglen);
585 out = modpow(in, rsa->exponent, rsa->modulus);
586 freebn(in);
587
588 ret = 1;
589
590 bytes = bignum_bitcount(rsa->modulus) / 8;
591 /* Top (partial) byte should be zero. */
592 if (bignum_byte(out, bytes - 1) != 0)
593 ret = 0;
594 /* First whole byte should be 1. */
595 if (bignum_byte(out, bytes - 2) != 1)
596 ret = 0;
597 /* Most of the rest should be FF. */
598 for (i = bytes - 3; i >= 20 + ASN1_LEN; i--) {
599 if (bignum_byte(out, i) != 0xFF)
600 ret = 0;
601 }
602 /* Then we expect to see the asn1_weird_stuff. */
603 for (i = 20 + ASN1_LEN - 1, j = 0; i >= 20; i--, j++) {
604 if (bignum_byte(out, i) != asn1_weird_stuff[j])
605 ret = 0;
606 }
607 /* Finally, we expect to see the SHA-1 hash of the signed data. */
608 SHA_Simple(data, datalen, hash);
609 for (i = 19, j = 0; i >= 0; i--, j++) {
610 if (bignum_byte(out, i) != hash[j])
611 ret = 0;
612 }
613
614 return ret;
615 }
616
617 unsigned char *rsa2_sign(void *key, char *data, int datalen, int *siglen)
618 {
619 struct RSAKey *rsa = (struct RSAKey *) key;
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
628 nbytes = (bignum_bitcount(rsa->modulus) - 1) / 8;
629 bytes = smalloc(nbytes);
630
631 bytes[0] = 1;
632 for (i = 1; i < nbytes - 20 - ASN1_LEN; i++)
633 bytes[i] = 0xFF;
634 for (i = nbytes - 20 - ASN1_LEN, j = 0; i < nbytes - 20; i++, j++)
635 bytes[i] = asn1_weird_stuff[j];
636 for (i = nbytes - 20, j = 0; i < nbytes; i++, j++)
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
645 nbytes = (bignum_bitcount(out) + 7) / 8;
646 bytes = smalloc(4 + 7 + 4 + nbytes);
647 PUT_32BIT(bytes, 7);
648 memcpy(bytes + 4, "ssh-rsa", 7);
649 PUT_32BIT(bytes + 4 + 7, nbytes);
650 for (i = 0; i < nbytes; i++)
651 bytes[4 + 7 + 4 + i] = bignum_byte(out, nbytes - 1 - i);
652 freebn(out);
653
654 *siglen = 4 + 7 + 4 + nbytes;
655 return bytes;
656 }
657
658 const struct ssh_signkey ssh_rsa = {
659 rsa2_newkey,
660 rsa2_freekey,
661 rsa2_fmtkey,
662 rsa2_public_blob,
663 rsa2_private_blob,
664 rsa2_createkey,
665 rsa2_openssh_createkey,
666 rsa2_openssh_fmtkey,
667 rsa2_fingerprint,
668 rsa2_verifysig,
669 rsa2_sign,
670 "ssh-rsa",
671 "rsa2"
672 };
Local modifications for Simon Tatham's `PuTTY' SSH client and terminal emulator