374330e2 |
1 | /* |
2 | * RSA implementation just sufficient for ssh client-side |
3 | * initialisation step |
4644b0ce |
4 | * |
5 | * Rewritten for more speed by Joris van Rantwijk, Jun 1999. |
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6 | */ |
7 | |
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8 | #include <stdio.h> |
9 | #include <stdlib.h> |
10 | #include <string.h> |
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11 | #include <assert.h> |
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12 | |
e5574168 |
13 | #include "ssh.h" |
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14 | |
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15 | |
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16 | int makekey(unsigned char *data, struct RSAKey *result, |
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17 | unsigned char **keystr, int order) { |
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18 | unsigned char *p = data; |
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19 | int i; |
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20 | |
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21 | if (result) { |
22 | result->bits = 0; |
23 | for (i=0; i<4; i++) |
24 | result->bits = (result->bits << 8) + *p++; |
25 | } else |
26 | p += 4; |
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27 | |
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28 | /* |
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). |
32 | */ |
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33 | |
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34 | if (order == 0) |
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35 | p += ssh1_read_bignum(p, result ? &result->exponent : NULL); |
36 | if (result) |
37 | result->bytes = (((p[0] << 8) + p[1]) + 7) / 8; |
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38 | if (keystr) *keystr = p+2; |
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39 | p += ssh1_read_bignum(p, result ? &result->modulus : NULL); |
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40 | if (order == 1) |
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41 | p += ssh1_read_bignum(p, result ? &result->exponent : NULL); |
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42 | |
43 | return p - data; |
44 | } |
45 | |
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46 | int makeprivate(unsigned char *data, struct RSAKey *result) { |
47 | return ssh1_read_bignum(data, &result->private_exponent); |
48 | } |
49 | |
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50 | void rsaencrypt(unsigned char *data, int length, struct RSAKey *key) { |
51 | Bignum b1, b2; |
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52 | int i; |
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53 | unsigned char *p; |
54 | |
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55 | memmove(data+key->bytes-length, data, length); |
56 | data[0] = 0; |
57 | data[1] = 2; |
58 | |
59 | for (i = 2; i < key->bytes-length-1; i++) { |
60 | do { |
61 | data[i] = random_byte(); |
62 | } while (data[i] == 0); |
63 | } |
64 | data[key->bytes-length-1] = 0; |
65 | |
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66 | b1 = bignum_from_bytes(data, key->bytes); |
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67 | |
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68 | b2 = modpow(b1, key->exponent, key->modulus); |
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69 | |
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70 | p = data; |
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71 | for (i=key->bytes; i-- ;) { |
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72 | *p++ = bignum_byte(b2, i); |
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73 | } |
74 | |
75 | freebn(b1); |
76 | freebn(b2); |
77 | } |
78 | |
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79 | Bignum rsadecrypt(Bignum input, struct RSAKey *key) { |
80 | Bignum ret; |
59600f67 |
81 | ret = modpow(input, key->private_exponent, key->modulus); |
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82 | return ret; |
83 | } |
84 | |
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85 | int rsastr_len(struct RSAKey *key) { |
86 | Bignum md, ex; |
3709bfe9 |
87 | int mdlen, exlen; |
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88 | |
89 | md = key->modulus; |
90 | ex = key->exponent; |
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91 | mdlen = (ssh1_bignum_bitcount(md)+15) / 16; |
92 | exlen = (ssh1_bignum_bitcount(ex)+15) / 16; |
93 | return 4 * (mdlen+exlen) + 20; |
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94 | } |
95 | |
96 | void rsastr_fmt(char *str, struct RSAKey *key) { |
97 | Bignum md, ex; |
d5859615 |
98 | int len = 0, i, nibbles; |
99 | static const char hex[] = "0123456789abcdef"; |
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100 | |
101 | md = key->modulus; |
102 | ex = key->exponent; |
103 | |
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104 | len += sprintf(str+len, "0x"); |
105 | |
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]; |
109 | |
110 | len += sprintf(str+len, ",0x"); |
111 | |
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]; |
115 | |
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116 | str[len] = '\0'; |
117 | } |
118 | |
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119 | /* |
120 | * Generate a fingerprint string for the key. Compatible with the |
121 | * OpenSSH fingerprint code. |
122 | */ |
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]; |
127 | int numlen, slen, i; |
128 | |
129 | MD5Init(&md5c); |
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); |
134 | } |
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); |
139 | } |
140 | MD5Final(digest, &md5c); |
141 | |
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'; |
146 | slen = strlen(str); |
147 | if (key->comment && slen < len-1) { |
148 | str[slen] = ' '; |
149 | strncpy(str+slen+1, key->comment, len-slen-1); |
150 | str[len-1] = '\0'; |
151 | } |
152 | } |
153 | |
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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); |
dcbde236 |
158 | if (key->comment) sfree(key->comment); |
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159 | } |
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160 | |
161 | /* ---------------------------------------------------------------------- |
162 | * Implementation of the ssh-rsa signing key type. |
163 | */ |
164 | |
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])) |
170 | |
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); } |
176 | |
177 | static void getstring(char **data, int *datalen, char **p, int *length) { |
178 | *p = NULL; |
179 | if (*datalen < 4) |
180 | return; |
181 | *length = GET_32BIT(*data); |
182 | *datalen -= 4; *data += 4; |
183 | if (*datalen < *length) |
184 | return; |
185 | *p = *data; |
186 | *data += *length; *datalen -= *length; |
187 | } |
188 | static Bignum getmp(char **data, int *datalen) { |
189 | char *p; |
190 | int length; |
191 | Bignum b; |
192 | |
193 | getstring(data, datalen, &p, &length); |
194 | if (!p) |
195 | return NULL; |
196 | b = bignum_from_bytes(p, length); |
197 | return b; |
198 | } |
199 | |
200 | static void *rsa2_newkey(char *data, int len) { |
201 | char *p; |
202 | int slen; |
203 | struct RSAKey *rsa; |
204 | |
205 | rsa = smalloc(sizeof(struct RSAKey)); |
206 | if (!rsa) return NULL; |
207 | getstring(&data, &len, &p, &slen); |
208 | |
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209 | if (!p || slen != 7 || memcmp(p, "ssh-rsa", 7)) { |
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210 | sfree(rsa); |
211 | return NULL; |
212 | } |
213 | rsa->exponent = getmp(&data, &len); |
214 | rsa->modulus = getmp(&data, &len); |
215 | rsa->private_exponent = NULL; |
216 | rsa->comment = NULL; |
217 | |
218 | return rsa; |
219 | } |
220 | |
221 | static void rsa2_freekey(void *key) { |
222 | struct RSAKey *rsa = (struct RSAKey *)key; |
223 | freersakey(rsa); |
224 | sfree(rsa); |
225 | } |
226 | |
227 | static char *rsa2_fmtkey(void *key) { |
228 | struct RSAKey *rsa = (struct RSAKey *)key; |
229 | char *p; |
230 | int len; |
231 | |
232 | len = rsastr_len(rsa); |
233 | p = smalloc(len); |
234 | rsastr_fmt(p, rsa); |
235 | return p; |
236 | } |
237 | |
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238 | static unsigned char *rsa2_public_blob(void *key, int *len) { |
239 | struct RSAKey *rsa = (struct RSAKey *)key; |
240 | int elen, mlen, bloblen; |
241 | int i; |
242 | unsigned char *blob, *p; |
243 | |
244 | elen = (ssh1_bignum_bitcount(rsa->exponent)+8)/8; |
245 | mlen = (ssh1_bignum_bitcount(rsa->modulus)+8)/8; |
246 | |
247 | /* |
248 | * string "ssh-rsa", mpint exp, mpint mod. Total 19+elen+mlen. |
249 | * (three length fields, 12+7=19). |
250 | */ |
251 | bloblen = 19+elen+mlen; |
252 | blob = smalloc(bloblen); |
253 | p = blob; |
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); |
261 | *len = bloblen; |
262 | return blob; |
263 | } |
264 | |
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; |
268 | int i; |
269 | unsigned char *blob, *p; |
270 | |
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; |
275 | |
276 | /* |
277 | * mpint private_exp, mpint p, mpint q, mpint iqmp. Total 16 + |
278 | * sum of lengths. |
279 | */ |
280 | bloblen = 16+dlen+plen+qlen+ulen; |
281 | blob = smalloc(bloblen); |
282 | p = blob; |
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); |
292 | *len = bloblen; |
293 | return blob; |
294 | } |
295 | |
296 | static void *rsa2_createkey(unsigned char *pub_blob, int pub_len, |
297 | unsigned char *priv_blob, int priv_len) { |
298 | struct RSAKey *rsa; |
299 | char *pb = (char *)priv_blob; |
300 | |
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); |
306 | |
307 | return rsa; |
308 | } |
309 | |
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310 | static void *rsa2_openssh_createkey(unsigned char **blob, int *len) { |
311 | char **b = (char **)blob; |
312 | struct RSAKey *rsa; |
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313 | |
314 | rsa = smalloc(sizeof(struct RSAKey)); |
315 | if (!rsa) return NULL; |
316 | rsa->comment = NULL; |
317 | |
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); |
324 | |
325 | if (!rsa->modulus || !rsa->exponent || !rsa->private_exponent || |
326 | !rsa->iqmp || !rsa->p || !rsa->q) { |
327 | sfree(rsa->modulus); |
328 | sfree(rsa->exponent); |
329 | sfree(rsa->private_exponent); |
330 | sfree(rsa->iqmp); |
331 | sfree(rsa->p); |
332 | sfree(rsa->q); |
333 | sfree(rsa); |
334 | return NULL; |
335 | } |
336 | |
337 | return rsa; |
338 | } |
339 | |
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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]; |
345 | char *ret; |
346 | int numlen, i; |
347 | |
348 | MD5Init(&md5c); |
349 | MD5Update(&md5c, "\0\0\0\7ssh-rsa", 11); |
350 | |
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); \ |
357 | } |
358 | ADD_BIGNUM(rsa->exponent); |
359 | ADD_BIGNUM(rsa->modulus); |
360 | #undef ADD_BIGNUM |
361 | |
362 | MD5Final(digest, &md5c); |
363 | |
5d03233b |
364 | sprintf(buffer, "ssh-rsa %d ", ssh1_bignum_bitcount(rsa->modulus)); |
85cc02bb |
365 | for (i = 0; i < 16; i++) |
366 | sprintf(buffer+strlen(buffer), "%s%02x", i?":":"", digest[i]); |
367 | ret = smalloc(strlen(buffer)+1); |
368 | if (ret) |
369 | strcpy(ret, buffer); |
370 | return ret; |
371 | } |
372 | |
373 | /* |
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 |
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376 | * value. The meaning of it is: |
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377 | * |
378 | * 00 -- this marks the end of the FFs; not part of the ASN.1 bit itself |
379 | * |
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 |
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383 | * 2B 0E 03 02 1A -- object id { 1 3 14 3 2 26 } |
384 | * (the 1,3 comes from 0x2B = 43 = 40*1+3) |
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385 | * 05 00 -- NULL |
386 | * 04 14 -- a primitive OCTET STRING of length 0x14 |
387 | * [0x14 bytes of hash data follows] |
96a73db9 |
388 | * |
389 | * The object id in the middle there is listed as `id-sha1' in |
390 | * ftp://ftp.rsasecurity.com/pub/pkcs/pkcs-1/pkcs-1v2-1d2.asn (the |
391 | * ASN module for PKCS #1) and its expanded form is as follows: |
392 | * |
393 | * id-sha1 OBJECT IDENTIFIER ::= { |
394 | * iso(1) identified-organization(3) oiw(14) secsig(3) |
395 | * algorithms(2) 26 } |
85cc02bb |
396 | */ |
397 | static unsigned char asn1_weird_stuff[] = { |
398 | 0x00,0x30,0x21,0x30,0x09,0x06,0x05,0x2B, |
399 | 0x0E,0x03,0x02,0x1A,0x05,0x00,0x04,0x14, |
400 | }; |
401 | |
d8770b12 |
402 | #define ASN1_LEN ( (int) sizeof(asn1_weird_stuff) ) |
403 | |
85cc02bb |
404 | static int rsa2_verifysig(void *key, char *sig, int siglen, |
405 | char *data, int datalen) { |
406 | struct RSAKey *rsa = (struct RSAKey *)key; |
407 | Bignum in, out; |
408 | char *p; |
409 | int slen; |
410 | int bytes, i, j, ret; |
411 | unsigned char hash[20]; |
412 | |
413 | getstring(&sig, &siglen, &p, &slen); |
414 | if (!p || slen != 7 || memcmp(p, "ssh-rsa", 7)) { |
415 | return 0; |
416 | } |
417 | in = getmp(&sig, &siglen); |
418 | out = modpow(in, rsa->exponent, rsa->modulus); |
419 | freebn(in); |
420 | |
421 | ret = 1; |
422 | |
423 | bytes = ssh1_bignum_bitcount(rsa->modulus) / 8; |
424 | /* Top (partial) byte should be zero. */ |
425 | if (bignum_byte(out, bytes-1) != 0) |
426 | ret = 0; |
427 | /* First whole byte should be 1. */ |
428 | if (bignum_byte(out, bytes-2) != 1) |
429 | ret = 0; |
430 | /* Most of the rest should be FF. */ |
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431 | for (i = bytes-3; i >= 20 + ASN1_LEN; i--) { |
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432 | if (bignum_byte(out, i) != 0xFF) |
433 | ret = 0; |
434 | } |
435 | /* Then we expect to see the asn1_weird_stuff. */ |
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436 | for (i = 20 + ASN1_LEN - 1, j=0; i >= 20; i--,j++) { |
85cc02bb |
437 | if (bignum_byte(out, i) != asn1_weird_stuff[j]) |
438 | ret = 0; |
439 | } |
440 | /* Finally, we expect to see the SHA-1 hash of the signed data. */ |
441 | SHA_Simple(data, datalen, hash); |
442 | for (i = 19, j=0; i >= 0; i--,j++) { |
443 | if (bignum_byte(out, i) != hash[j]) |
444 | ret = 0; |
445 | } |
446 | |
447 | return ret; |
448 | } |
449 | |
65a22376 |
450 | unsigned char *rsa2_sign(void *key, char *data, int datalen, int *siglen) { |
451 | struct RSAKey *rsa = (struct RSAKey *)key; |
452 | unsigned char *bytes; |
453 | int nbytes; |
454 | unsigned char hash[20]; |
455 | Bignum in, out; |
456 | int i, j; |
457 | |
458 | SHA_Simple(data, datalen, hash); |
459 | |
460 | nbytes = (ssh1_bignum_bitcount(rsa->modulus)-1) / 8; |
461 | bytes = smalloc(nbytes); |
462 | |
463 | bytes[0] = 1; |
d8770b12 |
464 | for (i = 1; i < nbytes-20-ASN1_LEN; i++) |
65a22376 |
465 | bytes[i] = 0xFF; |
d8770b12 |
466 | for (i = nbytes-20-ASN1_LEN, j=0; i < nbytes-20; i++,j++) |
65a22376 |
467 | bytes[i] = asn1_weird_stuff[j]; |
468 | for (i = nbytes-20, j=0; i < nbytes; i++,j++) |
469 | bytes[i] = hash[j]; |
470 | |
471 | in = bignum_from_bytes(bytes, nbytes); |
472 | sfree(bytes); |
473 | |
474 | out = modpow(in, rsa->private_exponent, rsa->modulus); |
475 | freebn(in); |
476 | |
477 | nbytes = (ssh1_bignum_bitcount(out)+7)/8; |
478 | bytes = smalloc(4+7+4+nbytes); |
479 | PUT_32BIT(bytes, 7); |
480 | memcpy(bytes+4, "ssh-rsa", 7); |
481 | PUT_32BIT(bytes+4+7, nbytes); |
482 | for (i = 0; i < nbytes; i++) |
483 | bytes[4+7+4+i] = bignum_byte(out, nbytes-1-i); |
484 | freebn(out); |
485 | |
486 | *siglen = 4+7+4+nbytes; |
487 | return bytes; |
85cc02bb |
488 | } |
489 | |
65a22376 |
490 | const struct ssh_signkey ssh_rsa = { |
85cc02bb |
491 | rsa2_newkey, |
492 | rsa2_freekey, |
493 | rsa2_fmtkey, |
65a22376 |
494 | rsa2_public_blob, |
495 | rsa2_private_blob, |
496 | rsa2_createkey, |
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497 | rsa2_openssh_createkey, |
85cc02bb |
498 | rsa2_fingerprint, |
499 | rsa2_verifysig, |
500 | rsa2_sign, |
501 | "ssh-rsa", |
502 | "rsa2" |
503 | }; |