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1 | /* |
2 | * RSA implementation just sufficient for ssh client-side |
3 | * initialisation step |
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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> |
12 | #include <windows.h> // FIXME |
13 | #include "putty.h" // FIXME |
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14 | |
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15 | #include "ssh.h" |
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16 | |
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17 | |
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18 | int makekey(unsigned char *data, struct RSAKey *result, |
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19 | unsigned char **keystr, int order) { |
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20 | unsigned char *p = data; |
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21 | int i; |
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22 | |
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23 | if (result) { |
24 | result->bits = 0; |
25 | for (i=0; i<4; i++) |
26 | result->bits = (result->bits << 8) + *p++; |
27 | } else |
28 | p += 4; |
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29 | |
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30 | /* |
31 | * order=0 means exponent then modulus (the keys sent by the |
32 | * server). order=1 means modulus then exponent (the keys |
33 | * stored in a keyfile). |
34 | */ |
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35 | |
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36 | if (order == 0) |
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37 | p += ssh1_read_bignum(p, result ? &result->exponent : NULL); |
38 | if (result) |
39 | result->bytes = (((p[0] << 8) + p[1]) + 7) / 8; |
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40 | if (keystr) *keystr = p+2; |
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41 | p += ssh1_read_bignum(p, result ? &result->modulus : NULL); |
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42 | if (order == 1) |
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43 | p += ssh1_read_bignum(p, result ? &result->exponent : NULL); |
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44 | |
45 | return p - data; |
46 | } |
47 | |
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48 | int makeprivate(unsigned char *data, struct RSAKey *result) { |
49 | return ssh1_read_bignum(data, &result->private_exponent); |
50 | } |
51 | |
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52 | void rsaencrypt(unsigned char *data, int length, struct RSAKey *key) { |
53 | Bignum b1, b2; |
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54 | int i; |
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55 | unsigned char *p; |
56 | |
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57 | memmove(data+key->bytes-length, data, length); |
58 | data[0] = 0; |
59 | data[1] = 2; |
60 | |
61 | for (i = 2; i < key->bytes-length-1; i++) { |
62 | do { |
63 | data[i] = random_byte(); |
64 | } while (data[i] == 0); |
65 | } |
66 | data[key->bytes-length-1] = 0; |
67 | |
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68 | b1 = bignum_from_bytes(data, key->bytes); |
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69 | |
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70 | b2 = modpow(b1, key->exponent, key->modulus); |
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71 | |
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72 | p = data; |
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73 | for (i=key->bytes; i-- ;) { |
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74 | *p++ = bignum_byte(b2, i); |
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75 | } |
76 | |
77 | freebn(b1); |
78 | freebn(b2); |
79 | } |
80 | |
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81 | Bignum rsadecrypt(Bignum input, struct RSAKey *key) { |
82 | Bignum ret; |
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83 | ret = modpow(input, key->private_exponent, key->modulus); |
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84 | return ret; |
85 | } |
86 | |
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87 | int rsastr_len(struct RSAKey *key) { |
88 | Bignum md, ex; |
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89 | int mdlen, exlen; |
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90 | |
91 | md = key->modulus; |
92 | ex = key->exponent; |
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93 | mdlen = (ssh1_bignum_bitcount(md)+15) / 16; |
94 | exlen = (ssh1_bignum_bitcount(ex)+15) / 16; |
95 | return 4 * (mdlen+exlen) + 20; |
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96 | } |
97 | |
98 | void rsastr_fmt(char *str, struct RSAKey *key) { |
99 | Bignum md, ex; |
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100 | int len = 0, i, nibbles; |
101 | static const char hex[] = "0123456789abcdef"; |
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102 | |
103 | md = key->modulus; |
104 | ex = key->exponent; |
105 | |
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106 | len += sprintf(str+len, "0x"); |
107 | |
108 | nibbles = (3 + ssh1_bignum_bitcount(ex))/4; if (nibbles<1) nibbles=1; |
109 | for (i=nibbles; i-- ;) |
110 | str[len++] = hex[(bignum_byte(ex, i/2) >> (4*(i%2))) & 0xF]; |
111 | |
112 | len += sprintf(str+len, ",0x"); |
113 | |
114 | nibbles = (3 + ssh1_bignum_bitcount(md))/4; if (nibbles<1) nibbles=1; |
115 | for (i=nibbles; i-- ;) |
116 | str[len++] = hex[(bignum_byte(md, i/2) >> (4*(i%2))) & 0xF]; |
117 | |
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118 | str[len] = '\0'; |
119 | } |
120 | |
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121 | /* |
122 | * Generate a fingerprint string for the key. Compatible with the |
123 | * OpenSSH fingerprint code. |
124 | */ |
125 | void rsa_fingerprint(char *str, int len, struct RSAKey *key) { |
126 | struct MD5Context md5c; |
127 | unsigned char digest[16]; |
128 | char buffer[16*3+40]; |
129 | int numlen, slen, i; |
130 | |
131 | MD5Init(&md5c); |
132 | numlen = ssh1_bignum_length(key->modulus) - 2; |
133 | for (i = numlen; i-- ;) { |
134 | unsigned char c = bignum_byte(key->modulus, i); |
135 | MD5Update(&md5c, &c, 1); |
136 | } |
137 | numlen = ssh1_bignum_length(key->exponent) - 2; |
138 | for (i = numlen; i-- ;) { |
139 | unsigned char c = bignum_byte(key->exponent, i); |
140 | MD5Update(&md5c, &c, 1); |
141 | } |
142 | MD5Final(digest, &md5c); |
143 | |
144 | sprintf(buffer, "%d ", ssh1_bignum_bitcount(key->modulus)); |
145 | for (i = 0; i < 16; i++) |
146 | sprintf(buffer+strlen(buffer), "%s%02x", i?":":"", digest[i]); |
147 | strncpy(str, buffer, len); str[len-1] = '\0'; |
148 | slen = strlen(str); |
149 | if (key->comment && slen < len-1) { |
150 | str[slen] = ' '; |
151 | strncpy(str+slen+1, key->comment, len-slen-1); |
152 | str[len-1] = '\0'; |
153 | } |
154 | } |
155 | |
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156 | void freersakey(struct RSAKey *key) { |
157 | if (key->modulus) freebn(key->modulus); |
158 | if (key->exponent) freebn(key->exponent); |
159 | if (key->private_exponent) freebn(key->private_exponent); |
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160 | if (key->comment) sfree(key->comment); |
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161 | } |
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162 | |
163 | /* ---------------------------------------------------------------------- |
164 | * Implementation of the ssh-rsa signing key type. |
165 | */ |
166 | |
167 | #define GET_32BIT(cp) \ |
168 | (((unsigned long)(unsigned char)(cp)[0] << 24) | \ |
169 | ((unsigned long)(unsigned char)(cp)[1] << 16) | \ |
170 | ((unsigned long)(unsigned char)(cp)[2] << 8) | \ |
171 | ((unsigned long)(unsigned char)(cp)[3])) |
172 | |
173 | #define PUT_32BIT(cp, value) { \ |
174 | (cp)[0] = (unsigned char)((value) >> 24); \ |
175 | (cp)[1] = (unsigned char)((value) >> 16); \ |
176 | (cp)[2] = (unsigned char)((value) >> 8); \ |
177 | (cp)[3] = (unsigned char)(value); } |
178 | |
179 | static void getstring(char **data, int *datalen, char **p, int *length) { |
180 | *p = NULL; |
181 | if (*datalen < 4) |
182 | return; |
183 | *length = GET_32BIT(*data); |
184 | *datalen -= 4; *data += 4; |
185 | if (*datalen < *length) |
186 | return; |
187 | *p = *data; |
188 | *data += *length; *datalen -= *length; |
189 | } |
190 | static Bignum getmp(char **data, int *datalen) { |
191 | char *p; |
192 | int length; |
193 | Bignum b; |
194 | |
195 | getstring(data, datalen, &p, &length); |
196 | if (!p) |
197 | return NULL; |
198 | b = bignum_from_bytes(p, length); |
199 | return b; |
200 | } |
201 | |
202 | static void *rsa2_newkey(char *data, int len) { |
203 | char *p; |
204 | int slen; |
205 | struct RSAKey *rsa; |
206 | |
207 | rsa = smalloc(sizeof(struct RSAKey)); |
208 | if (!rsa) return NULL; |
209 | getstring(&data, &len, &p, &slen); |
210 | |
211 | if (!p || memcmp(p, "ssh-rsa", 7)) { |
212 | sfree(rsa); |
213 | return NULL; |
214 | } |
215 | rsa->exponent = getmp(&data, &len); |
216 | rsa->modulus = getmp(&data, &len); |
217 | rsa->private_exponent = NULL; |
218 | rsa->comment = NULL; |
219 | |
220 | return rsa; |
221 | } |
222 | |
223 | static void rsa2_freekey(void *key) { |
224 | struct RSAKey *rsa = (struct RSAKey *)key; |
225 | freersakey(rsa); |
226 | sfree(rsa); |
227 | } |
228 | |
229 | static char *rsa2_fmtkey(void *key) { |
230 | struct RSAKey *rsa = (struct RSAKey *)key; |
231 | char *p; |
232 | int len; |
233 | |
234 | len = rsastr_len(rsa); |
235 | p = smalloc(len); |
236 | rsastr_fmt(p, rsa); |
237 | return p; |
238 | } |
239 | |
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240 | static unsigned char *rsa2_public_blob(void *key, int *len) { |
241 | struct RSAKey *rsa = (struct RSAKey *)key; |
242 | int elen, mlen, bloblen; |
243 | int i; |
244 | unsigned char *blob, *p; |
245 | |
246 | elen = (ssh1_bignum_bitcount(rsa->exponent)+8)/8; |
247 | mlen = (ssh1_bignum_bitcount(rsa->modulus)+8)/8; |
248 | |
249 | /* |
250 | * string "ssh-rsa", mpint exp, mpint mod. Total 19+elen+mlen. |
251 | * (three length fields, 12+7=19). |
252 | */ |
253 | bloblen = 19+elen+mlen; |
254 | blob = smalloc(bloblen); |
255 | p = blob; |
256 | PUT_32BIT(p, 7); p += 4; |
257 | memcpy(p, "ssh-rsa", 7); p += 7; |
258 | PUT_32BIT(p, elen); p += 4; |
259 | for (i = elen; i-- ;) *p++ = bignum_byte(rsa->exponent, i); |
260 | PUT_32BIT(p, mlen); p += 4; |
261 | for (i = mlen; i-- ;) *p++ = bignum_byte(rsa->modulus, i); |
262 | assert(p == blob + bloblen); |
263 | *len = bloblen; |
264 | return blob; |
265 | } |
266 | |
267 | static unsigned char *rsa2_private_blob(void *key, int *len) { |
268 | struct RSAKey *rsa = (struct RSAKey *)key; |
269 | int dlen, plen, qlen, ulen, bloblen; |
270 | int i; |
271 | unsigned char *blob, *p; |
272 | |
273 | dlen = (ssh1_bignum_bitcount(rsa->private_exponent)+8)/8; |
274 | plen = (ssh1_bignum_bitcount(rsa->p)+8)/8; |
275 | qlen = (ssh1_bignum_bitcount(rsa->q)+8)/8; |
276 | ulen = (ssh1_bignum_bitcount(rsa->iqmp)+8)/8; |
277 | |
278 | /* |
279 | * mpint private_exp, mpint p, mpint q, mpint iqmp. Total 16 + |
280 | * sum of lengths. |
281 | */ |
282 | bloblen = 16+dlen+plen+qlen+ulen; |
283 | blob = smalloc(bloblen); |
284 | p = blob; |
285 | PUT_32BIT(p, dlen); p += 4; |
286 | for (i = dlen; i-- ;) *p++ = bignum_byte(rsa->private_exponent, i); |
287 | PUT_32BIT(p, plen); p += 4; |
288 | for (i = plen; i-- ;) *p++ = bignum_byte(rsa->p, i); |
289 | PUT_32BIT(p, qlen); p += 4; |
290 | for (i = qlen; i-- ;) *p++ = bignum_byte(rsa->q, i); |
291 | PUT_32BIT(p, ulen); p += 4; |
292 | for (i = ulen; i-- ;) *p++ = bignum_byte(rsa->iqmp, i); |
293 | assert(p == blob + bloblen); |
294 | *len = bloblen; |
295 | return blob; |
296 | } |
297 | |
298 | static void *rsa2_createkey(unsigned char *pub_blob, int pub_len, |
299 | unsigned char *priv_blob, int priv_len) { |
300 | struct RSAKey *rsa; |
301 | char *pb = (char *)priv_blob; |
302 | |
303 | rsa = rsa2_newkey((char *)pub_blob, pub_len); |
304 | rsa->private_exponent = getmp(&pb, &priv_len); |
305 | rsa->p = getmp(&pb, &priv_len); |
306 | rsa->q = getmp(&pb, &priv_len); |
307 | rsa->iqmp = getmp(&pb, &priv_len); |
308 | |
309 | return rsa; |
310 | } |
311 | |
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312 | static char *rsa2_fingerprint(void *key) { |
313 | struct RSAKey *rsa = (struct RSAKey *)key; |
314 | struct MD5Context md5c; |
315 | unsigned char digest[16], lenbuf[4]; |
316 | char buffer[16*3+40]; |
317 | char *ret; |
318 | int numlen, i; |
319 | |
320 | MD5Init(&md5c); |
321 | MD5Update(&md5c, "\0\0\0\7ssh-rsa", 11); |
322 | |
323 | #define ADD_BIGNUM(bignum) \ |
324 | numlen = (ssh1_bignum_bitcount(bignum)+8)/8; \ |
325 | PUT_32BIT(lenbuf, numlen); MD5Update(&md5c, lenbuf, 4); \ |
326 | for (i = numlen; i-- ;) { \ |
327 | unsigned char c = bignum_byte(bignum, i); \ |
328 | MD5Update(&md5c, &c, 1); \ |
329 | } |
330 | ADD_BIGNUM(rsa->exponent); |
331 | ADD_BIGNUM(rsa->modulus); |
332 | #undef ADD_BIGNUM |
333 | |
334 | MD5Final(digest, &md5c); |
335 | |
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336 | sprintf(buffer, "ssh-rsa %d ", ssh1_bignum_bitcount(rsa->modulus)); |
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337 | for (i = 0; i < 16; i++) |
338 | sprintf(buffer+strlen(buffer), "%s%02x", i?":":"", digest[i]); |
339 | ret = smalloc(strlen(buffer)+1); |
340 | if (ret) |
341 | strcpy(ret, buffer); |
342 | return ret; |
343 | } |
344 | |
345 | /* |
346 | * This is the magic ASN.1/DER prefix that goes in the decoded |
347 | * signature, between the string of FFs and the actual SHA hash |
348 | * value. As closely as I can tell, the meaning of it is: |
349 | * |
350 | * 00 -- this marks the end of the FFs; not part of the ASN.1 bit itself |
351 | * |
352 | * 30 21 -- a constructed SEQUENCE of length 0x21 |
353 | * 30 09 -- a constructed sub-SEQUENCE of length 9 |
354 | * 06 05 -- an object identifier, length 5 |
355 | * 2B 0E 03 02 1A -- |
356 | * 05 00 -- NULL |
357 | * 04 14 -- a primitive OCTET STRING of length 0x14 |
358 | * [0x14 bytes of hash data follows] |
359 | */ |
360 | static unsigned char asn1_weird_stuff[] = { |
361 | 0x00,0x30,0x21,0x30,0x09,0x06,0x05,0x2B, |
362 | 0x0E,0x03,0x02,0x1A,0x05,0x00,0x04,0x14, |
363 | }; |
364 | |
365 | static int rsa2_verifysig(void *key, char *sig, int siglen, |
366 | char *data, int datalen) { |
367 | struct RSAKey *rsa = (struct RSAKey *)key; |
368 | Bignum in, out; |
369 | char *p; |
370 | int slen; |
371 | int bytes, i, j, ret; |
372 | unsigned char hash[20]; |
373 | |
374 | getstring(&sig, &siglen, &p, &slen); |
375 | if (!p || slen != 7 || memcmp(p, "ssh-rsa", 7)) { |
376 | return 0; |
377 | } |
378 | in = getmp(&sig, &siglen); |
379 | out = modpow(in, rsa->exponent, rsa->modulus); |
380 | freebn(in); |
381 | |
382 | ret = 1; |
383 | |
384 | bytes = ssh1_bignum_bitcount(rsa->modulus) / 8; |
385 | /* Top (partial) byte should be zero. */ |
386 | if (bignum_byte(out, bytes-1) != 0) |
387 | ret = 0; |
388 | /* First whole byte should be 1. */ |
389 | if (bignum_byte(out, bytes-2) != 1) |
390 | ret = 0; |
391 | /* Most of the rest should be FF. */ |
392 | for (i = bytes-3; i >= 20 + sizeof(asn1_weird_stuff); i--) { |
393 | if (bignum_byte(out, i) != 0xFF) |
394 | ret = 0; |
395 | } |
396 | /* Then we expect to see the asn1_weird_stuff. */ |
397 | for (i = 20 + sizeof(asn1_weird_stuff) - 1, j=0; i >= 20; i--,j++) { |
398 | if (bignum_byte(out, i) != asn1_weird_stuff[j]) |
399 | ret = 0; |
400 | } |
401 | /* Finally, we expect to see the SHA-1 hash of the signed data. */ |
402 | SHA_Simple(data, datalen, hash); |
403 | for (i = 19, j=0; i >= 0; i--,j++) { |
404 | if (bignum_byte(out, i) != hash[j]) |
405 | ret = 0; |
406 | } |
407 | |
408 | return ret; |
409 | } |
410 | |
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411 | unsigned char *rsa2_sign(void *key, char *data, int datalen, int *siglen) { |
412 | struct RSAKey *rsa = (struct RSAKey *)key; |
413 | unsigned char *bytes; |
414 | int nbytes; |
415 | unsigned char hash[20]; |
416 | Bignum in, out; |
417 | int i, j; |
418 | |
419 | SHA_Simple(data, datalen, hash); |
420 | |
421 | nbytes = (ssh1_bignum_bitcount(rsa->modulus)-1) / 8; |
422 | bytes = smalloc(nbytes); |
423 | |
424 | bytes[0] = 1; |
425 | for (i = 1; i < nbytes-20-sizeof(asn1_weird_stuff); i++) |
426 | bytes[i] = 0xFF; |
427 | for (i = nbytes-20-sizeof(asn1_weird_stuff), j=0; i < nbytes-20; i++,j++) |
428 | bytes[i] = asn1_weird_stuff[j]; |
429 | for (i = nbytes-20, j=0; i < nbytes; i++,j++) |
430 | bytes[i] = hash[j]; |
431 | |
432 | in = bignum_from_bytes(bytes, nbytes); |
433 | sfree(bytes); |
434 | |
435 | out = modpow(in, rsa->private_exponent, rsa->modulus); |
436 | freebn(in); |
437 | |
438 | nbytes = (ssh1_bignum_bitcount(out)+7)/8; |
439 | bytes = smalloc(4+7+4+nbytes); |
440 | PUT_32BIT(bytes, 7); |
441 | memcpy(bytes+4, "ssh-rsa", 7); |
442 | PUT_32BIT(bytes+4+7, nbytes); |
443 | for (i = 0; i < nbytes; i++) |
444 | bytes[4+7+4+i] = bignum_byte(out, nbytes-1-i); |
445 | freebn(out); |
446 | |
447 | *siglen = 4+7+4+nbytes; |
448 | return bytes; |
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449 | } |
450 | |
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451 | const struct ssh_signkey ssh_rsa = { |
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452 | rsa2_newkey, |
453 | rsa2_freekey, |
454 | rsa2_fmtkey, |
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455 | rsa2_public_blob, |
456 | rsa2_private_blob, |
457 | rsa2_createkey, |
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458 | rsa2_fingerprint, |
459 | rsa2_verifysig, |
460 | rsa2_sign, |
461 | "ssh-rsa", |
462 | "rsa2" |
463 | }; |