374330e2 |
1 | /* |
2 | * RSA implementation just sufficient for ssh client-side |
3 | * initialisation step |
4 | */ |
5 | |
6 | /*#include <windows.h> |
7 | #define RSADEBUG |
8 | #define DLVL 2 |
9 | #include "stel.h"*/ |
10 | |
11 | #include <stdio.h> |
12 | #include <stdlib.h> |
13 | #include <string.h> |
14 | |
15 | #include "ssh.h" |
16 | |
17 | typedef unsigned short *Bignum; |
18 | |
19 | static unsigned short Zero[1] = { 0 }; |
20 | |
21 | #if defined TESTMODE || defined RSADEBUG |
22 | #ifndef DLVL |
23 | #define DLVL 10000 |
24 | #endif |
25 | #define debug(x) bndebug(#x,x) |
26 | static int level = 0; |
27 | static void bndebug(char *name, Bignum b) { |
28 | int i; |
29 | int w = 50-level-strlen(name)-5*b[0]; |
30 | if (level >= DLVL) |
31 | return; |
32 | if (w < 0) w = 0; |
33 | dprintf("%*s%s%*s", level, "", name, w, ""); |
34 | for (i=b[0]; i>0; i--) |
35 | dprintf(" %04x", b[i]); |
36 | dprintf("\n"); |
37 | } |
38 | #define dmsg(x) do {if(level<DLVL){dprintf("%*s",level,"");printf x;}} while(0) |
39 | #define enter(x) do { dmsg(x); level += 4; } while(0) |
40 | #define leave(x) do { level -= 4; dmsg(x); } while(0) |
41 | #else |
42 | #define debug(x) |
43 | #define dmsg(x) |
44 | #define enter(x) |
45 | #define leave(x) |
46 | #endif |
47 | |
48 | static Bignum newbn(int length) { |
49 | Bignum b = malloc((length+1)*sizeof(unsigned short)); |
50 | if (!b) |
51 | abort(); /* FIXME */ |
52 | b[0] = length; |
53 | return b; |
54 | } |
55 | |
56 | static void freebn(Bignum b) { |
57 | free(b); |
58 | } |
59 | |
60 | static int msb(Bignum r) { |
61 | int i; |
62 | int j; |
63 | unsigned short n; |
64 | |
65 | for (i=r[0]; i>0; i--) |
66 | if (r[i]) |
67 | break; |
68 | |
69 | j = (i-1)*16; |
70 | n = r[i]; |
71 | if (n & 0xFF00) j += 8, n >>= 8; |
72 | if (n & 0x00F0) j += 4, n >>= 4; |
73 | if (n & 0x000C) j += 2, n >>= 2; |
74 | if (n & 0x0002) j += 1, n >>= 1; |
75 | |
76 | return j; |
77 | } |
78 | |
79 | static void add(Bignum r1, Bignum r2, Bignum result) { |
80 | int i; |
81 | long stuff = 0; |
82 | |
83 | enter((">add\n")); |
84 | debug(r1); |
85 | debug(r2); |
86 | |
87 | for (i = 1 ;; i++) { |
88 | if (i <= r1[0]) |
89 | stuff += r1[i]; |
90 | if (i <= r2[0]) |
91 | stuff += r2[i]; |
92 | if (i <= result[0]) |
93 | result[i] = stuff & 0xFFFFU; |
94 | if (i > r1[0] && i > r2[0] && i >= result[0]) |
95 | break; |
96 | stuff >>= 16; |
97 | } |
98 | |
99 | debug(result); |
100 | leave(("<add\n")); |
101 | } |
102 | |
103 | static void sub(Bignum r1, Bignum r2, Bignum result) { |
104 | int i; |
105 | long stuff = 0; |
106 | |
107 | enter((">sub\n")); |
108 | debug(r1); |
109 | debug(r2); |
110 | |
111 | for (i = 1 ;; i++) { |
112 | if (i <= r1[0]) |
113 | stuff += r1[i]; |
114 | if (i <= r2[0]) |
115 | stuff -= r2[i]; |
116 | if (i <= result[0]) |
117 | result[i] = stuff & 0xFFFFU; |
118 | if (i > r1[0] && i > r2[0] && i >= result[0]) |
119 | break; |
120 | stuff = stuff<0 ? -1 : 0; |
121 | } |
122 | |
123 | debug(result); |
124 | leave(("<sub\n")); |
125 | } |
126 | |
127 | static int ge(Bignum r1, Bignum r2) { |
128 | int i; |
129 | |
130 | enter((">ge\n")); |
131 | debug(r1); |
132 | debug(r2); |
133 | |
134 | if (r1[0] < r2[0]) |
135 | i = r2[0]; |
136 | else |
137 | i = r1[0]; |
138 | |
139 | while (i > 0) { |
140 | unsigned short n1 = (i > r1[0] ? 0 : r1[i]); |
141 | unsigned short n2 = (i > r2[0] ? 0 : r2[i]); |
142 | |
143 | if (n1 > n2) { |
144 | dmsg(("greater\n")); |
145 | leave(("<ge\n")); |
146 | return 1; /* r1 > r2 */ |
147 | } else if (n1 < n2) { |
148 | dmsg(("less\n")); |
149 | leave(("<ge\n")); |
150 | return 0; /* r1 < r2 */ |
151 | } |
152 | |
153 | i--; |
154 | } |
155 | |
156 | dmsg(("equal\n")); |
157 | leave(("<ge\n")); |
158 | return 1; /* r1 = r2 */ |
159 | } |
160 | |
161 | static void modmult(Bignum r1, Bignum r2, Bignum modulus, Bignum result) { |
162 | Bignum temp = newbn(modulus[0]+1); |
163 | Bignum tmp2 = newbn(modulus[0]+1); |
164 | int i; |
165 | int bit, bits, digit, smallbit; |
166 | |
167 | enter((">modmult\n")); |
168 | debug(r1); |
169 | debug(r2); |
170 | debug(modulus); |
171 | |
172 | for (i=1; i<=result[0]; i++) |
173 | result[i] = 0; /* result := 0 */ |
174 | for (i=1; i<=temp[0]; i++) |
175 | temp[i] = (i > r2[0] ? 0 : r2[i]); /* temp := r2 */ |
176 | |
177 | bits = 1+msb(r1); |
178 | |
179 | for (bit = 0; bit < bits; bit++) { |
180 | digit = 1 + bit / 16; |
181 | smallbit = bit % 16; |
182 | |
183 | debug(temp); |
184 | if (digit <= r1[0] && (r1[digit] & (1<<smallbit))) { |
185 | dmsg(("bit %d\n", bit)); |
186 | add(temp, result, tmp2); |
187 | if (ge(tmp2, modulus)) |
188 | sub(tmp2, modulus, result); |
189 | else |
190 | add(tmp2, Zero, result); |
191 | debug(result); |
192 | } |
193 | |
194 | add(temp, temp, tmp2); |
195 | if (ge(tmp2, modulus)) |
196 | sub(tmp2, modulus, temp); |
197 | else |
198 | add(tmp2, Zero, temp); |
199 | } |
200 | |
201 | freebn(temp); |
202 | freebn(tmp2); |
203 | |
204 | debug(result); |
205 | leave(("<modmult\n")); |
206 | } |
207 | |
208 | static void modpow(Bignum r1, Bignum r2, Bignum modulus, Bignum result) { |
209 | Bignum temp = newbn(modulus[0]+1); |
210 | Bignum tmp2 = newbn(modulus[0]+1); |
211 | int i; |
212 | int bit, bits, digit, smallbit; |
213 | |
214 | enter((">modpow\n")); |
215 | debug(r1); |
216 | debug(r2); |
217 | debug(modulus); |
218 | |
219 | for (i=1; i<=result[0]; i++) |
220 | result[i] = (i==1); /* result := 1 */ |
221 | for (i=1; i<=temp[0]; i++) |
222 | temp[i] = (i > r1[0] ? 0 : r1[i]); /* temp := r1 */ |
223 | |
224 | bits = 1+msb(r2); |
225 | |
226 | for (bit = 0; bit < bits; bit++) { |
227 | digit = 1 + bit / 16; |
228 | smallbit = bit % 16; |
229 | |
230 | debug(temp); |
231 | if (digit <= r2[0] && (r2[digit] & (1<<smallbit))) { |
232 | dmsg(("bit %d\n", bit)); |
233 | modmult(temp, result, modulus, tmp2); |
234 | add(tmp2, Zero, result); |
235 | debug(result); |
236 | } |
237 | |
238 | modmult(temp, temp, modulus, tmp2); |
239 | add(tmp2, Zero, temp); |
240 | } |
241 | |
242 | freebn(temp); |
243 | freebn(tmp2); |
244 | |
245 | debug(result); |
246 | leave(("<modpow\n")); |
247 | } |
248 | |
249 | int makekey(unsigned char *data, struct RSAKey *result, |
250 | unsigned char **keystr) { |
251 | unsigned char *p = data; |
252 | Bignum bn[2]; |
253 | int i, j; |
254 | int w, b; |
255 | |
256 | result->bits = 0; |
257 | for (i=0; i<4; i++) |
258 | result->bits = (result->bits << 8) + *p++; |
259 | |
260 | for (j=0; j<2; j++) { |
261 | |
262 | w = 0; |
263 | for (i=0; i<2; i++) |
264 | w = (w << 8) + *p++; |
265 | |
266 | result->bytes = b = (w+7)/8; /* bits -> bytes */ |
267 | w = (w+15)/16; /* bits -> words */ |
268 | |
269 | bn[j] = newbn(w); |
270 | |
271 | if (keystr) *keystr = p; /* point at key string, second time */ |
272 | |
273 | for (i=1; i<=w; i++) |
274 | bn[j][i] = 0; |
275 | for (i=0; i<b; i++) { |
276 | unsigned char byte = *p++; |
277 | if ((b-i) & 1) |
278 | bn[j][w-i/2] |= byte; |
279 | else |
280 | bn[j][w-i/2] |= byte<<8; |
281 | } |
282 | |
283 | debug(bn[j]); |
284 | |
285 | } |
286 | |
287 | result->exponent = bn[0]; |
288 | result->modulus = bn[1]; |
289 | |
290 | return p - data; |
291 | } |
292 | |
293 | void rsaencrypt(unsigned char *data, int length, struct RSAKey *key) { |
294 | Bignum b1, b2; |
295 | int w, i; |
296 | unsigned char *p; |
297 | |
298 | debug(key->exponent); |
299 | |
300 | memmove(data+key->bytes-length, data, length); |
301 | data[0] = 0; |
302 | data[1] = 2; |
303 | |
304 | for (i = 2; i < key->bytes-length-1; i++) { |
305 | do { |
306 | data[i] = random_byte(); |
307 | } while (data[i] == 0); |
308 | } |
309 | data[key->bytes-length-1] = 0; |
310 | |
311 | w = (key->bytes+1)/2; |
312 | |
313 | b1 = newbn(w); |
314 | b2 = newbn(w); |
315 | |
316 | p = data; |
317 | for (i=1; i<=w; i++) |
318 | b1[i] = 0; |
319 | for (i=0; i<key->bytes; i++) { |
320 | unsigned char byte = *p++; |
321 | if ((key->bytes-i) & 1) |
322 | b1[w-i/2] |= byte; |
323 | else |
324 | b1[w-i/2] |= byte<<8; |
325 | } |
326 | |
327 | debug(b1); |
328 | |
329 | modpow(b1, key->exponent, key->modulus, b2); |
330 | |
331 | debug(b2); |
332 | |
333 | p = data; |
334 | for (i=0; i<key->bytes; i++) { |
335 | unsigned char b; |
336 | if (i & 1) |
337 | b = b2[w-i/2] & 0xFF; |
338 | else |
339 | b = b2[w-i/2] >> 8; |
340 | *p++ = b; |
341 | } |
342 | |
343 | freebn(b1); |
344 | freebn(b2); |
345 | } |
346 | |
347 | int rsastr_len(struct RSAKey *key) { |
348 | Bignum md, ex; |
349 | |
350 | md = key->modulus; |
351 | ex = key->exponent; |
352 | return 4 * (ex[0]+md[0]) + 10; |
353 | } |
354 | |
355 | void rsastr_fmt(char *str, struct RSAKey *key) { |
356 | Bignum md, ex; |
357 | int len = 0, i; |
358 | |
359 | md = key->modulus; |
360 | ex = key->exponent; |
361 | |
362 | for (i=1; i<=ex[0]; i++) { |
363 | sprintf(str+len, "%04x", ex[i]); |
364 | len += strlen(str+len); |
365 | } |
366 | str[len++] = '/'; |
367 | for (i=1; i<=md[0]; i++) { |
368 | sprintf(str+len, "%04x", md[i]); |
369 | len += strlen(str+len); |
370 | } |
371 | str[len] = '\0'; |
372 | } |
373 | |
374 | #ifdef TESTMODE |
375 | |
376 | #ifndef NODDY |
377 | #define p1 10007 |
378 | #define p2 10069 |
379 | #define p3 10177 |
380 | #else |
381 | #define p1 3 |
382 | #define p2 7 |
383 | #define p3 13 |
384 | #endif |
385 | |
386 | unsigned short P1[2] = { 1, p1 }; |
387 | unsigned short P2[2] = { 1, p2 }; |
388 | unsigned short P3[2] = { 1, p3 }; |
389 | unsigned short bigmod[5] = { 4, 0, 0, 0, 32768U }; |
390 | unsigned short mod[5] = { 4, 0, 0, 0, 0 }; |
391 | unsigned short a[5] = { 4, 0, 0, 0, 0 }; |
392 | unsigned short b[5] = { 4, 0, 0, 0, 0 }; |
393 | unsigned short c[5] = { 4, 0, 0, 0, 0 }; |
394 | unsigned short One[2] = { 1, 1 }; |
395 | unsigned short Two[2] = { 1, 2 }; |
396 | |
397 | int main(void) { |
398 | modmult(P1, P2, bigmod, a); debug(a); |
399 | modmult(a, P3, bigmod, mod); debug(mod); |
400 | |
401 | sub(P1, One, a); debug(a); |
402 | sub(P2, One, b); debug(b); |
403 | modmult(a, b, bigmod, c); debug(c); |
404 | sub(P3, One, a); debug(a); |
405 | modmult(a, c, bigmod, b); debug(b); |
406 | |
407 | modpow(Two, b, mod, a); debug(a); |
408 | |
409 | return 0; |
410 | } |
411 | |
412 | #endif |