2 * RSA implementation just sufficient for ssh client-side
5 * Rewritten for more speed by Joris van Rantwijk, Jun 1999.
16 int makekey(unsigned char *data, struct RSAKey *result,
17 unsigned char **keystr, int order)
19 unsigned char *p = data;
24 for (i = 0; i < 4; i++)
25 result->bits = (result->bits << 8) + *p++;
30 * order=0 means exponent then modulus (the keys sent by the
31 * server). order=1 means modulus then exponent (the keys
32 * stored in a keyfile).
36 p += ssh1_read_bignum(p, result ? &result->exponent : NULL);
38 result->bytes = (((p[0] << 8) + p[1]) + 7) / 8;
41 p += ssh1_read_bignum(p, result ? &result->modulus : NULL);
43 p += ssh1_read_bignum(p, result ? &result->exponent : NULL);
48 int makeprivate(unsigned char *data, struct RSAKey *result)
50 return ssh1_read_bignum(data, &result->private_exponent);
53 void rsaencrypt(unsigned char *data, int length, struct RSAKey *key)
59 memmove(data + key->bytes - length, data, length);
63 for (i = 2; i < key->bytes - length - 1; i++) {
65 data[i] = random_byte();
66 } while (data[i] == 0);
68 data[key->bytes - length - 1] = 0;
70 b1 = bignum_from_bytes(data, key->bytes);
72 b2 = modpow(b1, key->exponent, key->modulus);
75 for (i = key->bytes; i--;) {
76 *p++ = bignum_byte(b2, i);
83 Bignum rsadecrypt(Bignum input, struct RSAKey *key)
86 ret = modpow(input, key->private_exponent, key->modulus);
90 int rsastr_len(struct RSAKey *key)
97 mdlen = (bignum_bitcount(md) + 15) / 16;
98 exlen = (bignum_bitcount(ex) + 15) / 16;
99 return 4 * (mdlen + exlen) + 20;
102 void rsastr_fmt(char *str, struct RSAKey *key)
105 int len = 0, i, nibbles;
106 static const char hex[] = "0123456789abcdef";
111 len += sprintf(str + len, "0x");
113 nibbles = (3 + bignum_bitcount(ex)) / 4;
116 for (i = nibbles; i--;)
117 str[len++] = hex[(bignum_byte(ex, i / 2) >> (4 * (i % 2))) & 0xF];
119 len += sprintf(str + len, ",0x");
121 nibbles = (3 + bignum_bitcount(md)) / 4;
124 for (i = nibbles; i--;)
125 str[len++] = hex[(bignum_byte(md, i / 2) >> (4 * (i % 2))) & 0xF];
131 * Generate a fingerprint string for the key. Compatible with the
132 * OpenSSH fingerprint code.
134 void rsa_fingerprint(char *str, int len, struct RSAKey *key)
136 struct MD5Context md5c;
137 unsigned char digest[16];
138 char buffer[16 * 3 + 40];
142 numlen = ssh1_bignum_length(key->modulus) - 2;
143 for (i = numlen; i--;) {
144 unsigned char c = bignum_byte(key->modulus, i);
145 MD5Update(&md5c, &c, 1);
147 numlen = ssh1_bignum_length(key->exponent) - 2;
148 for (i = numlen; i--;) {
149 unsigned char c = bignum_byte(key->exponent, i);
150 MD5Update(&md5c, &c, 1);
152 MD5Final(digest, &md5c);
154 sprintf(buffer, "%d ", bignum_bitcount(key->modulus));
155 for (i = 0; i < 16; i++)
156 sprintf(buffer + strlen(buffer), "%s%02x", i ? ":" : "",
158 strncpy(str, buffer, len);
161 if (key->comment && slen < len - 1) {
163 strncpy(str + slen + 1, key->comment, len - slen - 1);
169 * Verify that the public data in an RSA key matches the private
170 * data. We also check the private data itself: we ensure that p >
171 * q and that iqmp really is the inverse of q mod p.
173 int rsa_verify(struct RSAKey *key)
175 Bignum n, ed, pm1, qm1;
178 /* n must equal pq. */
179 n = bigmul(key->p, key->q);
180 cmp = bignum_cmp(n, key->modulus);
185 /* e * d must be congruent to 1, modulo (p-1) and modulo (q-1). */
186 pm1 = copybn(key->p);
188 ed = modmul(key->exponent, key->private_exponent, pm1);
189 cmp = bignum_cmp(ed, One);
194 qm1 = copybn(key->q);
196 ed = modmul(key->exponent, key->private_exponent, qm1);
197 cmp = bignum_cmp(ed, One);
205 if (bignum_cmp(key->p, key->q) <= 0)
209 * Ensure iqmp * q is congruent to 1, modulo p.
211 n = modmul(key->iqmp, key->q, key->p);
212 cmp = bignum_cmp(n, One);
220 void freersakey(struct RSAKey *key)
223 freebn(key->modulus);
225 freebn(key->exponent);
226 if (key->private_exponent)
227 freebn(key->private_exponent);
232 /* ----------------------------------------------------------------------
233 * Implementation of the ssh-rsa signing key type.
236 #define GET_32BIT(cp) \
237 (((unsigned long)(unsigned char)(cp)[0] << 24) | \
238 ((unsigned long)(unsigned char)(cp)[1] << 16) | \
239 ((unsigned long)(unsigned char)(cp)[2] << 8) | \
240 ((unsigned long)(unsigned char)(cp)[3]))
242 #define PUT_32BIT(cp, value) { \
243 (cp)[0] = (unsigned char)((value) >> 24); \
244 (cp)[1] = (unsigned char)((value) >> 16); \
245 (cp)[2] = (unsigned char)((value) >> 8); \
246 (cp)[3] = (unsigned char)(value); }
248 static void getstring(char **data, int *datalen, char **p, int *length)
253 *length = GET_32BIT(*data);
256 if (*datalen < *length)
262 static Bignum getmp(char **data, int *datalen)
268 getstring(data, datalen, &p, &length);
271 b = bignum_from_bytes(p, length);
275 static void *rsa2_newkey(char *data, int len)
281 rsa = smalloc(sizeof(struct RSAKey));
284 getstring(&data, &len, &p, &slen);
286 if (!p || slen != 7 || memcmp(p, "ssh-rsa", 7)) {
290 rsa->exponent = getmp(&data, &len);
291 rsa->modulus = getmp(&data, &len);
292 rsa->private_exponent = NULL;
298 static void rsa2_freekey(void *key)
300 struct RSAKey *rsa = (struct RSAKey *) key;
305 static char *rsa2_fmtkey(void *key)
307 struct RSAKey *rsa = (struct RSAKey *) key;
311 len = rsastr_len(rsa);
317 static unsigned char *rsa2_public_blob(void *key, int *len)
319 struct RSAKey *rsa = (struct RSAKey *) key;
320 int elen, mlen, bloblen;
322 unsigned char *blob, *p;
324 elen = (bignum_bitcount(rsa->exponent) + 8) / 8;
325 mlen = (bignum_bitcount(rsa->modulus) + 8) / 8;
328 * string "ssh-rsa", mpint exp, mpint mod. Total 19+elen+mlen.
329 * (three length fields, 12+7=19).
331 bloblen = 19 + elen + mlen;
332 blob = smalloc(bloblen);
336 memcpy(p, "ssh-rsa", 7);
341 *p++ = bignum_byte(rsa->exponent, i);
345 *p++ = bignum_byte(rsa->modulus, i);
346 assert(p == blob + bloblen);
351 static unsigned char *rsa2_private_blob(void *key, int *len)
353 struct RSAKey *rsa = (struct RSAKey *) key;
354 int dlen, plen, qlen, ulen, bloblen;
356 unsigned char *blob, *p;
358 dlen = (bignum_bitcount(rsa->private_exponent) + 8) / 8;
359 plen = (bignum_bitcount(rsa->p) + 8) / 8;
360 qlen = (bignum_bitcount(rsa->q) + 8) / 8;
361 ulen = (bignum_bitcount(rsa->iqmp) + 8) / 8;
364 * mpint private_exp, mpint p, mpint q, mpint iqmp. Total 16 +
367 bloblen = 16 + dlen + plen + qlen + ulen;
368 blob = smalloc(bloblen);
373 *p++ = bignum_byte(rsa->private_exponent, i);
377 *p++ = bignum_byte(rsa->p, i);
381 *p++ = bignum_byte(rsa->q, i);
385 *p++ = bignum_byte(rsa->iqmp, i);
386 assert(p == blob + bloblen);
391 static void *rsa2_createkey(unsigned char *pub_blob, int pub_len,
392 unsigned char *priv_blob, int priv_len)
395 char *pb = (char *) priv_blob;
397 rsa = rsa2_newkey((char *) pub_blob, pub_len);
398 rsa->private_exponent = getmp(&pb, &priv_len);
399 rsa->p = getmp(&pb, &priv_len);
400 rsa->q = getmp(&pb, &priv_len);
401 rsa->iqmp = getmp(&pb, &priv_len);
403 if (!rsa_verify(rsa)) {
411 static void *rsa2_openssh_createkey(unsigned char **blob, int *len)
413 char **b = (char **) blob;
416 rsa = smalloc(sizeof(struct RSAKey));
421 rsa->modulus = getmp(b, len);
422 rsa->exponent = getmp(b, len);
423 rsa->private_exponent = getmp(b, len);
424 rsa->iqmp = getmp(b, len);
425 rsa->p = getmp(b, len);
426 rsa->q = getmp(b, len);
428 if (!rsa->modulus || !rsa->exponent || !rsa->private_exponent ||
429 !rsa->iqmp || !rsa->p || !rsa->q) {
431 sfree(rsa->exponent);
432 sfree(rsa->private_exponent);
443 static int rsa2_openssh_fmtkey(void *key, unsigned char *blob, int len)
445 struct RSAKey *rsa = (struct RSAKey *) key;
449 ssh2_bignum_length(rsa->modulus) +
450 ssh2_bignum_length(rsa->exponent) +
451 ssh2_bignum_length(rsa->private_exponent) +
452 ssh2_bignum_length(rsa->iqmp) +
453 ssh2_bignum_length(rsa->p) + ssh2_bignum_length(rsa->q);
460 PUT_32BIT(blob+bloblen, ssh2_bignum_length((x))-4); bloblen += 4; \
461 for (i = ssh2_bignum_length((x))-4; i-- ;) blob[bloblen++]=bignum_byte((x),i);
464 ENC(rsa->private_exponent);
472 static char *rsa2_fingerprint(void *key)
474 struct RSAKey *rsa = (struct RSAKey *) key;
475 struct MD5Context md5c;
476 unsigned char digest[16], lenbuf[4];
477 char buffer[16 * 3 + 40];
482 MD5Update(&md5c, "\0\0\0\7ssh-rsa", 11);
484 #define ADD_BIGNUM(bignum) \
485 numlen = (bignum_bitcount(bignum)+8)/8; \
486 PUT_32BIT(lenbuf, numlen); MD5Update(&md5c, lenbuf, 4); \
487 for (i = numlen; i-- ;) { \
488 unsigned char c = bignum_byte(bignum, i); \
489 MD5Update(&md5c, &c, 1); \
491 ADD_BIGNUM(rsa->exponent);
492 ADD_BIGNUM(rsa->modulus);
495 MD5Final(digest, &md5c);
497 sprintf(buffer, "ssh-rsa %d ", bignum_bitcount(rsa->modulus));
498 for (i = 0; i < 16; i++)
499 sprintf(buffer + strlen(buffer), "%s%02x", i ? ":" : "",
501 ret = smalloc(strlen(buffer) + 1);
508 * This is the magic ASN.1/DER prefix that goes in the decoded
509 * signature, between the string of FFs and the actual SHA hash
510 * value. The meaning of it is:
512 * 00 -- this marks the end of the FFs; not part of the ASN.1 bit itself
514 * 30 21 -- a constructed SEQUENCE of length 0x21
515 * 30 09 -- a constructed sub-SEQUENCE of length 9
516 * 06 05 -- an object identifier, length 5
517 * 2B 0E 03 02 1A -- object id { 1 3 14 3 2 26 }
518 * (the 1,3 comes from 0x2B = 43 = 40*1+3)
520 * 04 14 -- a primitive OCTET STRING of length 0x14
521 * [0x14 bytes of hash data follows]
523 * The object id in the middle there is listed as `id-sha1' in
524 * ftp://ftp.rsasecurity.com/pub/pkcs/pkcs-1/pkcs-1v2-1d2.asn (the
525 * ASN module for PKCS #1) and its expanded form is as follows:
527 * id-sha1 OBJECT IDENTIFIER ::= {
528 * iso(1) identified-organization(3) oiw(14) secsig(3)
531 static unsigned char asn1_weird_stuff[] = {
532 0x00, 0x30, 0x21, 0x30, 0x09, 0x06, 0x05, 0x2B,
533 0x0E, 0x03, 0x02, 0x1A, 0x05, 0x00, 0x04, 0x14,
536 #define ASN1_LEN ( (int) sizeof(asn1_weird_stuff) )
538 static int rsa2_verifysig(void *key, char *sig, int siglen,
539 char *data, int datalen)
541 struct RSAKey *rsa = (struct RSAKey *) key;
545 int bytes, i, j, ret;
546 unsigned char hash[20];
548 getstring(&sig, &siglen, &p, &slen);
549 if (!p || slen != 7 || memcmp(p, "ssh-rsa", 7)) {
552 in = getmp(&sig, &siglen);
553 out = modpow(in, rsa->exponent, rsa->modulus);
558 bytes = bignum_bitcount(rsa->modulus) / 8;
559 /* Top (partial) byte should be zero. */
560 if (bignum_byte(out, bytes - 1) != 0)
562 /* First whole byte should be 1. */
563 if (bignum_byte(out, bytes - 2) != 1)
565 /* Most of the rest should be FF. */
566 for (i = bytes - 3; i >= 20 + ASN1_LEN; i--) {
567 if (bignum_byte(out, i) != 0xFF)
570 /* Then we expect to see the asn1_weird_stuff. */
571 for (i = 20 + ASN1_LEN - 1, j = 0; i >= 20; i--, j++) {
572 if (bignum_byte(out, i) != asn1_weird_stuff[j])
575 /* Finally, we expect to see the SHA-1 hash of the signed data. */
576 SHA_Simple(data, datalen, hash);
577 for (i = 19, j = 0; i >= 0; i--, j++) {
578 if (bignum_byte(out, i) != hash[j])
585 unsigned char *rsa2_sign(void *key, char *data, int datalen, int *siglen)
587 struct RSAKey *rsa = (struct RSAKey *) key;
588 unsigned char *bytes;
590 unsigned char hash[20];
594 SHA_Simple(data, datalen, hash);
596 nbytes = (bignum_bitcount(rsa->modulus) - 1) / 8;
597 bytes = smalloc(nbytes);
600 for (i = 1; i < nbytes - 20 - ASN1_LEN; i++)
602 for (i = nbytes - 20 - ASN1_LEN, j = 0; i < nbytes - 20; i++, j++)
603 bytes[i] = asn1_weird_stuff[j];
604 for (i = nbytes - 20, j = 0; i < nbytes; i++, j++)
607 in = bignum_from_bytes(bytes, nbytes);
610 out = modpow(in, rsa->private_exponent, rsa->modulus);
613 nbytes = (bignum_bitcount(out) + 7) / 8;
614 bytes = smalloc(4 + 7 + 4 + nbytes);
616 memcpy(bytes + 4, "ssh-rsa", 7);
617 PUT_32BIT(bytes + 4 + 7, nbytes);
618 for (i = 0; i < nbytes; i++)
619 bytes[4 + 7 + 4 + i] = bignum_byte(out, nbytes - 1 - i);
622 *siglen = 4 + 7 + 4 + nbytes;
626 const struct ssh_signkey ssh_rsa = {
633 rsa2_openssh_createkey,