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) {
18 unsigned char *p = data;
24 result->bits = (result->bits << 8) + *p++;
29 * order=0 means exponent then modulus (the keys sent by the
30 * server). order=1 means modulus then exponent (the keys
31 * stored in a keyfile).
35 p += ssh1_read_bignum(p, result ? &result->exponent : NULL);
37 result->bytes = (((p[0] << 8) + p[1]) + 7) / 8;
38 if (keystr) *keystr = p+2;
39 p += ssh1_read_bignum(p, result ? &result->modulus : NULL);
41 p += ssh1_read_bignum(p, result ? &result->exponent : NULL);
46 int makeprivate(unsigned char *data, struct RSAKey *result) {
47 return ssh1_read_bignum(data, &result->private_exponent);
50 void rsaencrypt(unsigned char *data, int length, struct RSAKey *key) {
55 memmove(data+key->bytes-length, data, length);
59 for (i = 2; i < key->bytes-length-1; i++) {
61 data[i] = random_byte();
62 } while (data[i] == 0);
64 data[key->bytes-length-1] = 0;
66 b1 = bignum_from_bytes(data, key->bytes);
68 b2 = modpow(b1, key->exponent, key->modulus);
71 for (i=key->bytes; i-- ;) {
72 *p++ = bignum_byte(b2, i);
79 Bignum rsadecrypt(Bignum input, struct RSAKey *key) {
81 ret = modpow(input, key->private_exponent, key->modulus);
85 int rsastr_len(struct RSAKey *key) {
91 mdlen = (ssh1_bignum_bitcount(md)+15) / 16;
92 exlen = (ssh1_bignum_bitcount(ex)+15) / 16;
93 return 4 * (mdlen+exlen) + 20;
96 void rsastr_fmt(char *str, struct RSAKey *key) {
98 int len = 0, i, nibbles;
99 static const char hex[] = "0123456789abcdef";
104 len += sprintf(str+len, "0x");
106 nibbles = (3 + ssh1_bignum_bitcount(ex))/4; if (nibbles<1) nibbles=1;
107 for (i=nibbles; i-- ;)
108 str[len++] = hex[(bignum_byte(ex, i/2) >> (4*(i%2))) & 0xF];
110 len += sprintf(str+len, ",0x");
112 nibbles = (3 + ssh1_bignum_bitcount(md))/4; if (nibbles<1) nibbles=1;
113 for (i=nibbles; i-- ;)
114 str[len++] = hex[(bignum_byte(md, i/2) >> (4*(i%2))) & 0xF];
120 * Generate a fingerprint string for the key. Compatible with the
121 * OpenSSH fingerprint code.
123 void rsa_fingerprint(char *str, int len, struct RSAKey *key) {
124 struct MD5Context md5c;
125 unsigned char digest[16];
126 char buffer[16*3+40];
130 numlen = ssh1_bignum_length(key->modulus) - 2;
131 for (i = numlen; i-- ;) {
132 unsigned char c = bignum_byte(key->modulus, i);
133 MD5Update(&md5c, &c, 1);
135 numlen = ssh1_bignum_length(key->exponent) - 2;
136 for (i = numlen; i-- ;) {
137 unsigned char c = bignum_byte(key->exponent, i);
138 MD5Update(&md5c, &c, 1);
140 MD5Final(digest, &md5c);
142 sprintf(buffer, "%d ", ssh1_bignum_bitcount(key->modulus));
143 for (i = 0; i < 16; i++)
144 sprintf(buffer+strlen(buffer), "%s%02x", i?":":"", digest[i]);
145 strncpy(str, buffer, len); str[len-1] = '\0';
147 if (key->comment && slen < len-1) {
149 strncpy(str+slen+1, key->comment, len-slen-1);
154 void freersakey(struct RSAKey *key) {
155 if (key->modulus) freebn(key->modulus);
156 if (key->exponent) freebn(key->exponent);
157 if (key->private_exponent) freebn(key->private_exponent);
158 if (key->comment) sfree(key->comment);
161 /* ----------------------------------------------------------------------
162 * Implementation of the ssh-rsa signing key type.
165 #define GET_32BIT(cp) \
166 (((unsigned long)(unsigned char)(cp)[0] << 24) | \
167 ((unsigned long)(unsigned char)(cp)[1] << 16) | \
168 ((unsigned long)(unsigned char)(cp)[2] << 8) | \
169 ((unsigned long)(unsigned char)(cp)[3]))
171 #define PUT_32BIT(cp, value) { \
172 (cp)[0] = (unsigned char)((value) >> 24); \
173 (cp)[1] = (unsigned char)((value) >> 16); \
174 (cp)[2] = (unsigned char)((value) >> 8); \
175 (cp)[3] = (unsigned char)(value); }
177 static void getstring(char **data, int *datalen, char **p, int *length) {
181 *length = GET_32BIT(*data);
182 *datalen -= 4; *data += 4;
183 if (*datalen < *length)
186 *data += *length; *datalen -= *length;
188 static Bignum getmp(char **data, int *datalen) {
193 getstring(data, datalen, &p, &length);
196 b = bignum_from_bytes(p, length);
200 static void *rsa2_newkey(char *data, int len) {
205 rsa = smalloc(sizeof(struct RSAKey));
206 if (!rsa) return NULL;
207 getstring(&data, &len, &p, &slen);
209 if (!p || slen != 7 || memcmp(p, "ssh-rsa", 7)) {
213 rsa->exponent = getmp(&data, &len);
214 rsa->modulus = getmp(&data, &len);
215 rsa->private_exponent = NULL;
221 static void rsa2_freekey(void *key) {
222 struct RSAKey *rsa = (struct RSAKey *)key;
227 static char *rsa2_fmtkey(void *key) {
228 struct RSAKey *rsa = (struct RSAKey *)key;
232 len = rsastr_len(rsa);
238 static unsigned char *rsa2_public_blob(void *key, int *len) {
239 struct RSAKey *rsa = (struct RSAKey *)key;
240 int elen, mlen, bloblen;
242 unsigned char *blob, *p;
244 elen = (ssh1_bignum_bitcount(rsa->exponent)+8)/8;
245 mlen = (ssh1_bignum_bitcount(rsa->modulus)+8)/8;
248 * string "ssh-rsa", mpint exp, mpint mod. Total 19+elen+mlen.
249 * (three length fields, 12+7=19).
251 bloblen = 19+elen+mlen;
252 blob = smalloc(bloblen);
254 PUT_32BIT(p, 7); p += 4;
255 memcpy(p, "ssh-rsa", 7); p += 7;
256 PUT_32BIT(p, elen); p += 4;
257 for (i = elen; i-- ;) *p++ = bignum_byte(rsa->exponent, i);
258 PUT_32BIT(p, mlen); p += 4;
259 for (i = mlen; i-- ;) *p++ = bignum_byte(rsa->modulus, i);
260 assert(p == blob + bloblen);
265 static unsigned char *rsa2_private_blob(void *key, int *len) {
266 struct RSAKey *rsa = (struct RSAKey *)key;
267 int dlen, plen, qlen, ulen, bloblen;
269 unsigned char *blob, *p;
271 dlen = (ssh1_bignum_bitcount(rsa->private_exponent)+8)/8;
272 plen = (ssh1_bignum_bitcount(rsa->p)+8)/8;
273 qlen = (ssh1_bignum_bitcount(rsa->q)+8)/8;
274 ulen = (ssh1_bignum_bitcount(rsa->iqmp)+8)/8;
277 * mpint private_exp, mpint p, mpint q, mpint iqmp. Total 16 +
280 bloblen = 16+dlen+plen+qlen+ulen;
281 blob = smalloc(bloblen);
283 PUT_32BIT(p, dlen); p += 4;
284 for (i = dlen; i-- ;) *p++ = bignum_byte(rsa->private_exponent, i);
285 PUT_32BIT(p, plen); p += 4;
286 for (i = plen; i-- ;) *p++ = bignum_byte(rsa->p, i);
287 PUT_32BIT(p, qlen); p += 4;
288 for (i = qlen; i-- ;) *p++ = bignum_byte(rsa->q, i);
289 PUT_32BIT(p, ulen); p += 4;
290 for (i = ulen; i-- ;) *p++ = bignum_byte(rsa->iqmp, i);
291 assert(p == blob + bloblen);
296 static void *rsa2_createkey(unsigned char *pub_blob, int pub_len,
297 unsigned char *priv_blob, int priv_len) {
299 char *pb = (char *)priv_blob;
301 rsa = rsa2_newkey((char *)pub_blob, pub_len);
302 rsa->private_exponent = getmp(&pb, &priv_len);
303 rsa->p = getmp(&pb, &priv_len);
304 rsa->q = getmp(&pb, &priv_len);
305 rsa->iqmp = getmp(&pb, &priv_len);
310 static void *rsa2_openssh_createkey(unsigned char **blob, int *len) {
311 char **b = (char **)blob;
314 rsa = smalloc(sizeof(struct RSAKey));
315 if (!rsa) return NULL;
318 rsa->modulus = getmp(b, len);
319 rsa->exponent = getmp(b, len);
320 rsa->private_exponent = getmp(b, len);
321 rsa->iqmp = getmp(b, len);
322 rsa->p = getmp(b, len);
323 rsa->q = getmp(b, len);
325 if (!rsa->modulus || !rsa->exponent || !rsa->private_exponent ||
326 !rsa->iqmp || !rsa->p || !rsa->q) {
328 sfree(rsa->exponent);
329 sfree(rsa->private_exponent);
340 static char *rsa2_fingerprint(void *key) {
341 struct RSAKey *rsa = (struct RSAKey *)key;
342 struct MD5Context md5c;
343 unsigned char digest[16], lenbuf[4];
344 char buffer[16*3+40];
349 MD5Update(&md5c, "\0\0\0\7ssh-rsa", 11);
351 #define ADD_BIGNUM(bignum) \
352 numlen = (ssh1_bignum_bitcount(bignum)+8)/8; \
353 PUT_32BIT(lenbuf, numlen); MD5Update(&md5c, lenbuf, 4); \
354 for (i = numlen; i-- ;) { \
355 unsigned char c = bignum_byte(bignum, i); \
356 MD5Update(&md5c, &c, 1); \
358 ADD_BIGNUM(rsa->exponent);
359 ADD_BIGNUM(rsa->modulus);
362 MD5Final(digest, &md5c);
364 sprintf(buffer, "ssh-rsa %d ", ssh1_bignum_bitcount(rsa->modulus));
365 for (i = 0; i < 16; i++)
366 sprintf(buffer+strlen(buffer), "%s%02x", i?":":"", digest[i]);
367 ret = smalloc(strlen(buffer)+1);
374 * This is the magic ASN.1/DER prefix that goes in the decoded
375 * signature, between the string of FFs and the actual SHA hash
376 * value. As closely as I can tell, the meaning of it is:
378 * 00 -- this marks the end of the FFs; not part of the ASN.1 bit itself
380 * 30 21 -- a constructed SEQUENCE of length 0x21
381 * 30 09 -- a constructed sub-SEQUENCE of length 9
382 * 06 05 -- an object identifier, length 5
385 * 04 14 -- a primitive OCTET STRING of length 0x14
386 * [0x14 bytes of hash data follows]
388 static unsigned char asn1_weird_stuff[] = {
389 0x00,0x30,0x21,0x30,0x09,0x06,0x05,0x2B,
390 0x0E,0x03,0x02,0x1A,0x05,0x00,0x04,0x14,
393 #define ASN1_LEN ( (int) sizeof(asn1_weird_stuff) )
395 static int rsa2_verifysig(void *key, char *sig, int siglen,
396 char *data, int datalen) {
397 struct RSAKey *rsa = (struct RSAKey *)key;
401 int bytes, i, j, ret;
402 unsigned char hash[20];
404 getstring(&sig, &siglen, &p, &slen);
405 if (!p || slen != 7 || memcmp(p, "ssh-rsa", 7)) {
408 in = getmp(&sig, &siglen);
409 out = modpow(in, rsa->exponent, rsa->modulus);
414 bytes = ssh1_bignum_bitcount(rsa->modulus) / 8;
415 /* Top (partial) byte should be zero. */
416 if (bignum_byte(out, bytes-1) != 0)
418 /* First whole byte should be 1. */
419 if (bignum_byte(out, bytes-2) != 1)
421 /* Most of the rest should be FF. */
422 for (i = bytes-3; i >= 20 + ASN1_LEN; i--) {
423 if (bignum_byte(out, i) != 0xFF)
426 /* Then we expect to see the asn1_weird_stuff. */
427 for (i = 20 + ASN1_LEN - 1, j=0; i >= 20; i--,j++) {
428 if (bignum_byte(out, i) != asn1_weird_stuff[j])
431 /* Finally, we expect to see the SHA-1 hash of the signed data. */
432 SHA_Simple(data, datalen, hash);
433 for (i = 19, j=0; i >= 0; i--,j++) {
434 if (bignum_byte(out, i) != hash[j])
441 unsigned char *rsa2_sign(void *key, char *data, int datalen, int *siglen) {
442 struct RSAKey *rsa = (struct RSAKey *)key;
443 unsigned char *bytes;
445 unsigned char hash[20];
449 SHA_Simple(data, datalen, hash);
451 nbytes = (ssh1_bignum_bitcount(rsa->modulus)-1) / 8;
452 bytes = smalloc(nbytes);
455 for (i = 1; i < nbytes-20-ASN1_LEN; i++)
457 for (i = nbytes-20-ASN1_LEN, j=0; i < nbytes-20; i++,j++)
458 bytes[i] = asn1_weird_stuff[j];
459 for (i = nbytes-20, j=0; i < nbytes; i++,j++)
462 in = bignum_from_bytes(bytes, nbytes);
465 out = modpow(in, rsa->private_exponent, rsa->modulus);
468 nbytes = (ssh1_bignum_bitcount(out)+7)/8;
469 bytes = smalloc(4+7+4+nbytes);
471 memcpy(bytes+4, "ssh-rsa", 7);
472 PUT_32BIT(bytes+4+7, nbytes);
473 for (i = 0; i < nbytes; i++)
474 bytes[4+7+4+i] = bignum_byte(out, nbytes-1-i);
477 *siglen = 4+7+4+nbytes;
481 const struct ssh_signkey ssh_rsa = {
488 rsa2_openssh_createkey,