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
= (bignum_bitcount(md
)+15) / 16;
92 exlen
= (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 + 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 + 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 ", 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);
155 * Verify that the public data in an RSA key matches the private
156 * data. We also check the private data itself: we ensure that p >
157 * q and that iqmp really is the inverse of q mod p.
159 int rsa_verify(struct RSAKey
*key
) {
160 Bignum n
, ed
, pm1
, qm1
;
163 /* n must equal pq. */
164 n
= bigmul(key
->p
, key
->q
);
165 cmp
= bignum_cmp(n
, key
->modulus
);
170 /* e * d must be congruent to 1, modulo (p-1) and modulo (q-1). */
171 pm1
= copybn(key
->p
);
173 ed
= modmul(key
->exponent
, key
->private_exponent
, pm1
);
174 cmp
= bignum_cmp(ed
, One
);
179 qm1
= copybn(key
->q
);
181 ed
= modmul(key
->exponent
, key
->private_exponent
, qm1
);
182 cmp
= bignum_cmp(ed
, One
);
190 if (bignum_cmp(key
->p
, key
->q
) <= 0)
194 * Ensure iqmp * q is congruent to 1, modulo p.
196 n
= modmul(key
->iqmp
, key
->q
, key
->p
);
197 cmp
= bignum_cmp(n
, One
);
205 void freersakey(struct RSAKey
*key
) {
206 if (key
->modulus
) freebn(key
->modulus
);
207 if (key
->exponent
) freebn(key
->exponent
);
208 if (key
->private_exponent
) freebn(key
->private_exponent
);
209 if (key
->comment
) sfree(key
->comment
);
212 /* ----------------------------------------------------------------------
213 * Implementation of the ssh-rsa signing key type.
216 #define GET_32BIT(cp) \
217 (((unsigned long)(unsigned char)(cp)[0] << 24) | \
218 ((unsigned long)(unsigned char)(cp)[1] << 16) | \
219 ((unsigned long)(unsigned char)(cp)[2] << 8) | \
220 ((unsigned long)(unsigned char)(cp)[3]))
222 #define PUT_32BIT(cp, value) { \
223 (cp)[0] = (unsigned char)((value) >> 24); \
224 (cp)[1] = (unsigned char)((value) >> 16); \
225 (cp)[2] = (unsigned char)((value) >> 8); \
226 (cp)[3] = (unsigned char)(value); }
228 static void getstring(char **data
, int *datalen
, char **p
, int *length
) {
232 *length
= GET_32BIT(*data
);
233 *datalen
-= 4; *data
+= 4;
234 if (*datalen
< *length
)
237 *data
+= *length
; *datalen
-= *length
;
239 static Bignum
getmp(char **data
, int *datalen
) {
244 getstring(data
, datalen
, &p
, &length
);
247 b
= bignum_from_bytes(p
, length
);
251 static void *rsa2_newkey(char *data
, int len
) {
256 rsa
= smalloc(sizeof(struct RSAKey
));
257 if (!rsa
) return NULL
;
258 getstring(&data
, &len
, &p
, &slen
);
260 if (!p
|| slen
!= 7 || memcmp(p
, "ssh-rsa", 7)) {
264 rsa
->exponent
= getmp(&data
, &len
);
265 rsa
->modulus
= getmp(&data
, &len
);
266 rsa
->private_exponent
= NULL
;
272 static void rsa2_freekey(void *key
) {
273 struct RSAKey
*rsa
= (struct RSAKey
*)key
;
278 static char *rsa2_fmtkey(void *key
) {
279 struct RSAKey
*rsa
= (struct RSAKey
*)key
;
283 len
= rsastr_len(rsa
);
289 static unsigned char *rsa2_public_blob(void *key
, int *len
) {
290 struct RSAKey
*rsa
= (struct RSAKey
*)key
;
291 int elen
, mlen
, bloblen
;
293 unsigned char *blob
, *p
;
295 elen
= (bignum_bitcount(rsa
->exponent
)+8)/8;
296 mlen
= (bignum_bitcount(rsa
->modulus
)+8)/8;
299 * string "ssh-rsa", mpint exp, mpint mod. Total 19+elen+mlen.
300 * (three length fields, 12+7=19).
302 bloblen
= 19+elen
+mlen
;
303 blob
= smalloc(bloblen
);
305 PUT_32BIT(p
, 7); p
+= 4;
306 memcpy(p
, "ssh-rsa", 7); p
+= 7;
307 PUT_32BIT(p
, elen
); p
+= 4;
308 for (i
= elen
; i
-- ;) *p
++ = bignum_byte(rsa
->exponent
, i
);
309 PUT_32BIT(p
, mlen
); p
+= 4;
310 for (i
= mlen
; i
-- ;) *p
++ = bignum_byte(rsa
->modulus
, i
);
311 assert(p
== blob
+ bloblen
);
316 static unsigned char *rsa2_private_blob(void *key
, int *len
) {
317 struct RSAKey
*rsa
= (struct RSAKey
*)key
;
318 int dlen
, plen
, qlen
, ulen
, bloblen
;
320 unsigned char *blob
, *p
;
322 dlen
= (bignum_bitcount(rsa
->private_exponent
)+8)/8;
323 plen
= (bignum_bitcount(rsa
->p
)+8)/8;
324 qlen
= (bignum_bitcount(rsa
->q
)+8)/8;
325 ulen
= (bignum_bitcount(rsa
->iqmp
)+8)/8;
328 * mpint private_exp, mpint p, mpint q, mpint iqmp. Total 16 +
331 bloblen
= 16+dlen
+plen
+qlen
+ulen
;
332 blob
= smalloc(bloblen
);
334 PUT_32BIT(p
, dlen
); p
+= 4;
335 for (i
= dlen
; i
-- ;) *p
++ = bignum_byte(rsa
->private_exponent
, i
);
336 PUT_32BIT(p
, plen
); p
+= 4;
337 for (i
= plen
; i
-- ;) *p
++ = bignum_byte(rsa
->p
, i
);
338 PUT_32BIT(p
, qlen
); p
+= 4;
339 for (i
= qlen
; i
-- ;) *p
++ = bignum_byte(rsa
->q
, i
);
340 PUT_32BIT(p
, ulen
); p
+= 4;
341 for (i
= ulen
; i
-- ;) *p
++ = bignum_byte(rsa
->iqmp
, i
);
342 assert(p
== blob
+ bloblen
);
347 static void *rsa2_createkey(unsigned char *pub_blob
, int pub_len
,
348 unsigned char *priv_blob
, int priv_len
) {
350 char *pb
= (char *)priv_blob
;
352 rsa
= rsa2_newkey((char *)pub_blob
, pub_len
);
353 rsa
->private_exponent
= getmp(&pb
, &priv_len
);
354 rsa
->p
= getmp(&pb
, &priv_len
);
355 rsa
->q
= getmp(&pb
, &priv_len
);
356 rsa
->iqmp
= getmp(&pb
, &priv_len
);
358 if (!rsa_verify(rsa
)) {
366 static void *rsa2_openssh_createkey(unsigned char **blob
, int *len
) {
367 char **b
= (char **)blob
;
370 rsa
= smalloc(sizeof(struct RSAKey
));
371 if (!rsa
) return NULL
;
374 rsa
->modulus
= getmp(b
, len
);
375 rsa
->exponent
= getmp(b
, len
);
376 rsa
->private_exponent
= getmp(b
, len
);
377 rsa
->iqmp
= getmp(b
, len
);
378 rsa
->p
= getmp(b
, len
);
379 rsa
->q
= getmp(b
, len
);
381 if (!rsa
->modulus
|| !rsa
->exponent
|| !rsa
->private_exponent
||
382 !rsa
->iqmp
|| !rsa
->p
|| !rsa
->q
) {
384 sfree(rsa
->exponent
);
385 sfree(rsa
->private_exponent
);
396 static int rsa2_openssh_fmtkey(void *key
, unsigned char *blob
, int len
) {
397 struct RSAKey
*rsa
= (struct RSAKey
*)key
;
401 ssh2_bignum_length(rsa
->modulus
) +
402 ssh2_bignum_length(rsa
->exponent
) +
403 ssh2_bignum_length(rsa
->private_exponent
) +
404 ssh2_bignum_length(rsa
->iqmp
) +
405 ssh2_bignum_length(rsa
->p
) +
406 ssh2_bignum_length(rsa
->q
);
413 PUT_32BIT(blob+bloblen, ssh2_bignum_length((x))-4); bloblen += 4; \
414 for (i = ssh2_bignum_length((x))-4; i-- ;) blob[bloblen++]=bignum_byte((x),i);
417 ENC(rsa
->private_exponent
);
425 static char *rsa2_fingerprint(void *key
) {
426 struct RSAKey
*rsa
= (struct RSAKey
*)key
;
427 struct MD5Context md5c
;
428 unsigned char digest
[16], lenbuf
[4];
429 char buffer
[16*3+40];
434 MD5Update(&md5c
, "\0\0\0\7ssh-rsa", 11);
436 #define ADD_BIGNUM(bignum) \
437 numlen = (bignum_bitcount(bignum)+8)/8; \
438 PUT_32BIT(lenbuf, numlen); MD5Update(&md5c, lenbuf, 4); \
439 for (i = numlen; i-- ;) { \
440 unsigned char c = bignum_byte(bignum, i); \
441 MD5Update(&md5c, &c, 1); \
443 ADD_BIGNUM(rsa
->exponent
);
444 ADD_BIGNUM(rsa
->modulus
);
447 MD5Final(digest
, &md5c
);
449 sprintf(buffer
, "ssh-rsa %d ", bignum_bitcount(rsa
->modulus
));
450 for (i
= 0; i
< 16; i
++)
451 sprintf(buffer
+strlen(buffer
), "%s%02x", i?
":":"", digest
[i
]);
452 ret
= smalloc(strlen(buffer
)+1);
459 * This is the magic ASN.1/DER prefix that goes in the decoded
460 * signature, between the string of FFs and the actual SHA hash
461 * value. The meaning of it is:
463 * 00 -- this marks the end of the FFs; not part of the ASN.1 bit itself
465 * 30 21 -- a constructed SEQUENCE of length 0x21
466 * 30 09 -- a constructed sub-SEQUENCE of length 9
467 * 06 05 -- an object identifier, length 5
468 * 2B 0E 03 02 1A -- object id { 1 3 14 3 2 26 }
469 * (the 1,3 comes from 0x2B = 43 = 40*1+3)
471 * 04 14 -- a primitive OCTET STRING of length 0x14
472 * [0x14 bytes of hash data follows]
474 * The object id in the middle there is listed as `id-sha1' in
475 * ftp://ftp.rsasecurity.com/pub/pkcs/pkcs-1/pkcs-1v2-1d2.asn (the
476 * ASN module for PKCS #1) and its expanded form is as follows:
478 * id-sha1 OBJECT IDENTIFIER ::= {
479 * iso(1) identified-organization(3) oiw(14) secsig(3)
482 static unsigned char asn1_weird_stuff
[] = {
483 0x00,0x30,0x21,0x30,0x09,0x06,0x05,0x2B,
484 0x0E,0x03,0x02,0x1A,0x05,0x00,0x04,0x14,
487 #define ASN1_LEN ( (int) sizeof(asn1_weird_stuff) )
489 static int rsa2_verifysig(void *key
, char *sig
, int siglen
,
490 char *data
, int datalen
) {
491 struct RSAKey
*rsa
= (struct RSAKey
*)key
;
495 int bytes
, i
, j
, ret
;
496 unsigned char hash
[20];
498 getstring(&sig
, &siglen
, &p
, &slen
);
499 if (!p
|| slen
!= 7 || memcmp(p
, "ssh-rsa", 7)) {
502 in
= getmp(&sig
, &siglen
);
503 out
= modpow(in
, rsa
->exponent
, rsa
->modulus
);
508 bytes
= bignum_bitcount(rsa
->modulus
) / 8;
509 /* Top (partial) byte should be zero. */
510 if (bignum_byte(out
, bytes
-1) != 0)
512 /* First whole byte should be 1. */
513 if (bignum_byte(out
, bytes
-2) != 1)
515 /* Most of the rest should be FF. */
516 for (i
= bytes
-3; i
>= 20 + ASN1_LEN
; i
--) {
517 if (bignum_byte(out
, i
) != 0xFF)
520 /* Then we expect to see the asn1_weird_stuff. */
521 for (i
= 20 + ASN1_LEN
- 1, j
=0; i
>= 20; i
--,j
++) {
522 if (bignum_byte(out
, i
) != asn1_weird_stuff
[j
])
525 /* Finally, we expect to see the SHA-1 hash of the signed data. */
526 SHA_Simple(data
, datalen
, hash
);
527 for (i
= 19, j
=0; i
>= 0; i
--,j
++) {
528 if (bignum_byte(out
, i
) != hash
[j
])
535 unsigned char *rsa2_sign(void *key
, char *data
, int datalen
, int *siglen
) {
536 struct RSAKey
*rsa
= (struct RSAKey
*)key
;
537 unsigned char *bytes
;
539 unsigned char hash
[20];
543 SHA_Simple(data
, datalen
, hash
);
545 nbytes
= (bignum_bitcount(rsa
->modulus
)-1) / 8;
546 bytes
= smalloc(nbytes
);
549 for (i
= 1; i
< nbytes
-20-ASN1_LEN
; i
++)
551 for (i
= nbytes
-20-ASN1_LEN
, j
=0; i
< nbytes
-20; i
++,j
++)
552 bytes
[i
] = asn1_weird_stuff
[j
];
553 for (i
= nbytes
-20, j
=0; i
< nbytes
; i
++,j
++)
556 in
= bignum_from_bytes(bytes
, nbytes
);
559 out
= modpow(in
, rsa
->private_exponent
, rsa
->modulus
);
562 nbytes
= (bignum_bitcount(out
)+7)/8;
563 bytes
= smalloc(4+7+4+nbytes
);
565 memcpy(bytes
+4, "ssh-rsa", 7);
566 PUT_32BIT(bytes
+4+7, nbytes
);
567 for (i
= 0; i
< nbytes
; i
++)
568 bytes
[4+7+4+i
] = bignum_byte(out
, nbytes
-1-i
);
571 *siglen
= 4+7+4+nbytes
;
575 const struct ssh_signkey ssh_rsa
= {
582 rsa2_openssh_createkey
,