2 * RSA implementation just sufficient for ssh client-side
5 * Rewritten for more speed by Joris van Rantwijk, Jun 1999.
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]))
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); }
28 int makekey(unsigned char *data, struct RSAKey *result,
29 unsigned char **keystr, int order)
31 unsigned char *p = data;
36 for (i = 0; i < 4; i++)
37 result->bits = (result->bits << 8) + *p++;
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).
48 p += ssh1_read_bignum(p, result ? &result->exponent : NULL);
50 result->bytes = (((p[0] << 8) + p[1]) + 7) / 8;
53 p += ssh1_read_bignum(p, result ? &result->modulus : NULL);
55 p += ssh1_read_bignum(p, result ? &result->exponent : NULL);
60 int makeprivate(unsigned char *data, struct RSAKey *result)
62 return ssh1_read_bignum(data, &result->private_exponent);
65 void rsaencrypt(unsigned char *data, int length, struct RSAKey *key)
71 memmove(data + key->bytes - length, data, length);
75 for (i = 2; i < key->bytes - length - 1; i++) {
77 data[i] = random_byte();
78 } while (data[i] == 0);
80 data[key->bytes - length - 1] = 0;
82 b1 = bignum_from_bytes(data, key->bytes);
84 b2 = modpow(b1, key->exponent, key->modulus);
87 for (i = key->bytes; i--;) {
88 *p++ = bignum_byte(b2, i);
95 Bignum rsadecrypt(Bignum input, struct RSAKey *key)
98 ret = modpow(input, key->private_exponent, key->modulus);
102 int rsastr_len(struct RSAKey *key)
109 mdlen = (bignum_bitcount(md) + 15) / 16;
110 exlen = (bignum_bitcount(ex) + 15) / 16;
111 return 4 * (mdlen + exlen) + 20;
114 void rsastr_fmt(char *str, struct RSAKey *key)
117 int len = 0, i, nibbles;
118 static const char hex[] = "0123456789abcdef";
123 len += sprintf(str + len, "0x");
125 nibbles = (3 + bignum_bitcount(ex)) / 4;
128 for (i = nibbles; i--;)
129 str[len++] = hex[(bignum_byte(ex, i / 2) >> (4 * (i % 2))) & 0xF];
131 len += sprintf(str + len, ",0x");
133 nibbles = (3 + bignum_bitcount(md)) / 4;
136 for (i = nibbles; i--;)
137 str[len++] = hex[(bignum_byte(md, i / 2) >> (4 * (i % 2))) & 0xF];
143 * Generate a fingerprint string for the key. Compatible with the
144 * OpenSSH fingerprint code.
146 void rsa_fingerprint(char *str, int len, struct RSAKey *key)
148 struct MD5Context md5c;
149 unsigned char digest[16];
150 char buffer[16 * 3 + 40];
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);
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);
164 MD5Final(digest, &md5c);
166 sprintf(buffer, "%d ", bignum_bitcount(key->modulus));
167 for (i = 0; i < 16; i++)
168 sprintf(buffer + strlen(buffer), "%s%02x", i ? ":" : "",
170 strncpy(str, buffer, len);
173 if (key->comment && slen < len - 1) {
175 strncpy(str + slen + 1, key->comment, len - slen - 1);
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.
185 int rsa_verify(struct RSAKey *key)
187 Bignum n, ed, pm1, qm1;
190 /* n must equal pq. */
191 n = bigmul(key->p, key->q);
192 cmp = bignum_cmp(n, key->modulus);
197 /* e * d must be congruent to 1, modulo (p-1) and modulo (q-1). */
198 pm1 = copybn(key->p);
200 ed = modmul(key->exponent, key->private_exponent, pm1);
201 cmp = bignum_cmp(ed, One);
206 qm1 = copybn(key->q);
208 ed = modmul(key->exponent, key->private_exponent, qm1);
209 cmp = bignum_cmp(ed, One);
217 if (bignum_cmp(key->p, key->q) <= 0)
221 * Ensure iqmp * q is congruent to 1, modulo p.
223 n = modmul(key->iqmp, key->q, key->p);
224 cmp = bignum_cmp(n, One);
232 /* Public key blob as used by Pageant: exponent before modulus. */
233 unsigned char *rsa_public_blob(struct RSAKey *key, int *len)
238 length = (ssh1_bignum_length(key->modulus) +
239 ssh1_bignum_length(key->exponent) + 4);
240 ret = smalloc(length);
242 PUT_32BIT(ret, bignum_bitcount(key->modulus));
244 pos += ssh1_write_bignum(ret + pos, key->exponent);
245 pos += ssh1_write_bignum(ret + pos, key->modulus);
251 /* Given a public blob, determine its length. */
252 int rsa_public_blob_len(void *data)
254 unsigned char *p = (unsigned char *)data;
257 p += 4; /* length word */
258 p += ssh1_read_bignum(p, NULL); /* exponent */
259 p += ssh1_read_bignum(p, NULL); /* modulus */
261 return p - (unsigned char *)data;
264 void freersakey(struct RSAKey *key)
267 freebn(key->modulus);
269 freebn(key->exponent);
270 if (key->private_exponent)
271 freebn(key->private_exponent);
276 /* ----------------------------------------------------------------------
277 * Implementation of the ssh-rsa signing key type.
280 static void getstring(char **data, int *datalen, char **p, int *length)
285 *length = GET_32BIT(*data);
288 if (*datalen < *length)
294 static Bignum getmp(char **data, int *datalen)
300 getstring(data, datalen, &p, &length);
303 b = bignum_from_bytes(p, length);
307 static void *rsa2_newkey(char *data, int len)
313 rsa = smalloc(sizeof(struct RSAKey));
316 getstring(&data, &len, &p, &slen);
318 if (!p || slen != 7 || memcmp(p, "ssh-rsa", 7)) {
322 rsa->exponent = getmp(&data, &len);
323 rsa->modulus = getmp(&data, &len);
324 rsa->private_exponent = NULL;
330 static void rsa2_freekey(void *key)
332 struct RSAKey *rsa = (struct RSAKey *) key;
337 static char *rsa2_fmtkey(void *key)
339 struct RSAKey *rsa = (struct RSAKey *) key;
343 len = rsastr_len(rsa);
349 static unsigned char *rsa2_public_blob(void *key, int *len)
351 struct RSAKey *rsa = (struct RSAKey *) key;
352 int elen, mlen, bloblen;
354 unsigned char *blob, *p;
356 elen = (bignum_bitcount(rsa->exponent) + 8) / 8;
357 mlen = (bignum_bitcount(rsa->modulus) + 8) / 8;
360 * string "ssh-rsa", mpint exp, mpint mod. Total 19+elen+mlen.
361 * (three length fields, 12+7=19).
363 bloblen = 19 + elen + mlen;
364 blob = smalloc(bloblen);
368 memcpy(p, "ssh-rsa", 7);
373 *p++ = bignum_byte(rsa->exponent, i);
377 *p++ = bignum_byte(rsa->modulus, i);
378 assert(p == blob + bloblen);
383 static unsigned char *rsa2_private_blob(void *key, int *len)
385 struct RSAKey *rsa = (struct RSAKey *) key;
386 int dlen, plen, qlen, ulen, bloblen;
388 unsigned char *blob, *p;
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;
396 * mpint private_exp, mpint p, mpint q, mpint iqmp. Total 16 +
399 bloblen = 16 + dlen + plen + qlen + ulen;
400 blob = smalloc(bloblen);
405 *p++ = bignum_byte(rsa->private_exponent, i);
409 *p++ = bignum_byte(rsa->p, i);
413 *p++ = bignum_byte(rsa->q, i);
417 *p++ = bignum_byte(rsa->iqmp, i);
418 assert(p == blob + bloblen);
423 static void *rsa2_createkey(unsigned char *pub_blob, int pub_len,
424 unsigned char *priv_blob, int priv_len)
427 char *pb = (char *) priv_blob;
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);
435 if (!rsa_verify(rsa)) {
443 static void *rsa2_openssh_createkey(unsigned char **blob, int *len)
445 char **b = (char **) blob;
448 rsa = smalloc(sizeof(struct RSAKey));
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);
460 if (!rsa->modulus || !rsa->exponent || !rsa->private_exponent ||
461 !rsa->iqmp || !rsa->p || !rsa->q) {
463 sfree(rsa->exponent);
464 sfree(rsa->private_exponent);
475 static int rsa2_openssh_fmtkey(void *key, unsigned char *blob, int len)
477 struct RSAKey *rsa = (struct RSAKey *) key;
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);
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);
496 ENC(rsa->private_exponent);
504 static char *rsa2_fingerprint(void *key)
506 struct RSAKey *rsa = (struct RSAKey *) key;
507 struct MD5Context md5c;
508 unsigned char digest[16], lenbuf[4];
509 char buffer[16 * 3 + 40];
514 MD5Update(&md5c, "\0\0\0\7ssh-rsa", 11);
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); \
523 ADD_BIGNUM(rsa->exponent);
524 ADD_BIGNUM(rsa->modulus);
527 MD5Final(digest, &md5c);
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 ? ":" : "",
533 ret = smalloc(strlen(buffer) + 1);
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:
544 * 00 -- this marks the end of the FFs; not part of the ASN.1 bit itself
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)
552 * 04 14 -- a primitive OCTET STRING of length 0x14
553 * [0x14 bytes of hash data follows]
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:
559 * id-sha1 OBJECT IDENTIFIER ::= {
560 * iso(1) identified-organization(3) oiw(14) secsig(3)
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,
568 #define ASN1_LEN ( (int) sizeof(asn1_weird_stuff) )
570 static int rsa2_verifysig(void *key, char *sig, int siglen,
571 char *data, int datalen)
573 struct RSAKey *rsa = (struct RSAKey *) key;
577 int bytes, i, j, ret;
578 unsigned char hash[20];
580 getstring(&sig, &siglen, &p, &slen);
581 if (!p || slen != 7 || memcmp(p, "ssh-rsa", 7)) {
584 in = getmp(&sig, &siglen);
585 out = modpow(in, rsa->exponent, rsa->modulus);
590 bytes = bignum_bitcount(rsa->modulus) / 8;
591 /* Top (partial) byte should be zero. */
592 if (bignum_byte(out, bytes - 1) != 0)
594 /* First whole byte should be 1. */
595 if (bignum_byte(out, bytes - 2) != 1)
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)
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])
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])
617 unsigned char *rsa2_sign(void *key, char *data, int datalen, int *siglen)
619 struct RSAKey *rsa = (struct RSAKey *) key;
620 unsigned char *bytes;
622 unsigned char hash[20];
626 SHA_Simple(data, datalen, hash);
628 nbytes = (bignum_bitcount(rsa->modulus) - 1) / 8;
629 bytes = smalloc(nbytes);
632 for (i = 1; i < nbytes - 20 - ASN1_LEN; i++)
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++)
639 in = bignum_from_bytes(bytes, nbytes);
642 out = modpow(in, rsa->private_exponent, rsa->modulus);
645 nbytes = (bignum_bitcount(out) + 7) / 8;
646 bytes = smalloc(4 + 7 + 4 + nbytes);
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);
654 *siglen = 4 + 7 + 4 + nbytes;
658 const struct ssh_signkey ssh_rsa = {
665 rsa2_openssh_createkey,