2 * RSA implementation just sufficient for ssh client-side
4 * Modified by Joris, Jun 1999.
20 typedef unsigned short *Bignum;
22 static unsigned short Zero[1] = { 0 };
24 #if defined TESTMODE || defined RSADEBUG
28 #define debug(x) bndebug(#x,x)
30 static void bndebug(char *name, Bignum b) {
32 int w = 50-level-strlen(name)-5*b[0];
36 dprintf("%*s%s%*s", level, "", name, w, "");
37 for (i=b[0]; i>0; i--)
38 dprintf(" %04x", b[i]);
41 #define dmsg(x) do {if(level<DLVL){dprintf("%*s",level,"");printf x;}} while(0)
42 #define enter(x) do { dmsg(x); level += 4; } while(0)
43 #define leave(x) do { level -= 4; dmsg(x); } while(0)
51 static Bignum newbn(int length) {
52 Bignum b = malloc((length+1)*sizeof(unsigned short));
59 static void freebn(Bignum b) {
67 * Input is in the first len words of a and b.
68 * Result is returned in the first 2*len words of c.
70 static void bigmul(unsigned short *a, unsigned short *b, unsigned short *c,
76 for (j = len - 1; j >= 0; j--)
79 for (i = len - 1; i >= 0; i--) {
82 for (j = len - 1; j >= 0; j--) {
83 t += ai * (unsigned long) b[j];
84 t += (unsigned long) c[i+j+1];
95 * Input in first 2*len words of a and first len words of m.
96 * Output in first 2*len words of a (of which first len words will be zero).
97 * The MSW of m MUST have its high bit set.
99 static void bigmod(unsigned short *a, unsigned short *m, int len)
101 unsigned short m0, m1;
105 /* Special case for len == 1 */
107 a[1] = (((long) a[0] << 16) + a[1]) % m[0];
115 for (i = 0; i <= len; i++) {
117 unsigned int q, r, c;
126 /* Find q = h:a[i] / m0 */
127 t = ((unsigned long) h << 16) + a[i];
131 /* Refine our estimate of q by looking at
132 h:a[i]:a[i+1] / m0:m1 */
133 t = (long) m1 * (long) q;
134 if (t > ((unsigned long) r << 16) + a[i+1]) {
137 r = (r + m0) & 0xffff; /* overflow? */
138 if (r >= m0 && t > ((unsigned long) r << 16) + a[i+1])
142 /* Substract q * m from a[i...] */
144 for (k = len - 1; k >= 0; k--) {
145 t = (long) q * (long) m[k];
148 if ((unsigned short) t > a[i+k]) c++;
149 a[i+k] -= (unsigned short) t;
152 /* Add back m in case of borrow */
155 for (k = len - 1; k >= 0; k--) {
167 * Compute (base ^ exp) % mod.
168 * The base MUST be smaller than the modulus.
169 * The most significant word of mod MUST be non-zero.
170 * We assume that the result array is the same size as the mod array.
172 static void modpow(Bignum base, Bignum exp, Bignum mod, Bignum result)
174 unsigned short *a, *b, *n, *m;
178 /* Allocate m of size mlen, copy mod to m */
179 /* We use big endian internally */
181 m = malloc(mlen * sizeof(unsigned short));
182 for (j = 0; j < mlen; j++) m[j] = mod[mod[0] - j];
184 /* Shift m left to make msb bit set */
185 for (mshift = 0; mshift < 15; mshift++)
186 if ((m[0] << mshift) & 0x8000) break;
188 for (i = 0; i < mlen - 1; i++)
189 m[i] = (m[i] << mshift) | (m[i+1] >> (16-mshift));
190 m[mlen-1] = m[mlen-1] << mshift;
193 /* Allocate n of size mlen, copy base to n */
194 n = malloc(mlen * sizeof(unsigned short));
196 for (j = 0; j < i; j++) n[j] = 0;
197 for (j = 0; j < base[0]; j++) n[i+j] = base[base[0] - j];
199 /* Allocate a and b of size 2*mlen. Set a = 1 */
200 a = malloc(2 * mlen * sizeof(unsigned short));
201 b = malloc(2 * mlen * sizeof(unsigned short));
202 for (i = 0; i < 2*mlen; i++) a[i] = 0;
205 /* Skip leading zero bits of exp. */
207 while (i < exp[0] && (exp[exp[0] - i] & (1 << j)) == 0) {
209 if (j < 0) { i++; j = 15; }
212 /* Main computation */
215 bigmul(a + mlen, a + mlen, b, mlen);
217 if ((exp[exp[0] - i] & (1 << j)) != 0) {
218 bigmul(b + mlen, n, a, mlen);
229 /* Fixup result in case the modulus was shifted */
231 for (i = mlen - 1; i < 2*mlen - 1; i++)
232 a[i] = (a[i] << mshift) | (a[i+1] >> (16-mshift));
233 a[2*mlen-1] = a[2*mlen-1] << mshift;
235 for (i = 2*mlen - 1; i >= mlen; i--)
236 a[i] = (a[i] >> mshift) | (a[i-1] << (16-mshift));
239 /* Copy result to buffer */
240 for (i = 0; i < mlen; i++)
241 result[result[0] - i] = a[i+mlen];
243 /* Free temporary arrays */
244 for (i = 0; i < 2*mlen; i++) a[i] = 0; free(a);
245 for (i = 0; i < 2*mlen; i++) b[i] = 0; free(b);
246 for (i = 0; i < mlen; i++) m[i] = 0; free(m);
247 for (i = 0; i < mlen; i++) n[i] = 0; free(n);
252 static int msb(Bignum r) {
257 for (i=r[0]; i>0; i--)
263 if (n & 0xFF00) j += 8, n >>= 8;
264 if (n & 0x00F0) j += 4, n >>= 4;
265 if (n & 0x000C) j += 2, n >>= 2;
266 if (n & 0x0002) j += 1, n >>= 1;
271 static void add(Bignum r1, Bignum r2, Bignum result) {
285 result[i] = stuff & 0xFFFFU;
286 if (i > r1[0] && i > r2[0] && i >= result[0])
295 static void sub(Bignum r1, Bignum r2, Bignum result) {
309 result[i] = stuff & 0xFFFFU;
310 if (i > r1[0] && i > r2[0] && i >= result[0])
312 stuff = stuff<0 ? -1 : 0;
319 static int ge(Bignum r1, Bignum r2) {
332 unsigned short n1 = (i > r1[0] ? 0 : r1[i]);
333 unsigned short n2 = (i > r2[0] ? 0 : r2[i]);
338 return 1; /* r1 > r2 */
339 } else if (n1 < n2) {
342 return 0; /* r1 < r2 */
350 return 1; /* r1 = r2 */
353 static void modmult(Bignum r1, Bignum r2, Bignum modulus, Bignum result) {
354 Bignum temp = newbn(modulus[0]+1);
355 Bignum tmp2 = newbn(modulus[0]+1);
357 int bit, bits, digit, smallbit;
359 enter((">modmult\n"));
364 for (i=1; i<=result[0]; i++)
365 result[i] = 0; /* result := 0 */
366 for (i=1; i<=temp[0]; i++)
367 temp[i] = (i > r2[0] ? 0 : r2[i]); /* temp := r2 */
371 for (bit = 0; bit < bits; bit++) {
372 digit = 1 + bit / 16;
376 if (digit <= r1[0] && (r1[digit] & (1<<smallbit))) {
377 dmsg(("bit %d\n", bit));
378 add(temp, result, tmp2);
379 if (ge(tmp2, modulus))
380 sub(tmp2, modulus, result);
382 add(tmp2, Zero, result);
386 add(temp, temp, tmp2);
387 if (ge(tmp2, modulus))
388 sub(tmp2, modulus, temp);
390 add(tmp2, Zero, temp);
397 leave(("<modmult\n"));
400 static void modpow(Bignum r1, Bignum r2, Bignum modulus, Bignum result) {
401 Bignum temp = newbn(modulus[0]+1);
402 Bignum tmp2 = newbn(modulus[0]+1);
404 int bit, bits, digit, smallbit;
406 enter((">modpow\n"));
411 for (i=1; i<=result[0]; i++)
412 result[i] = (i==1); /* result := 1 */
413 for (i=1; i<=temp[0]; i++)
414 temp[i] = (i > r1[0] ? 0 : r1[i]); /* temp := r1 */
418 for (bit = 0; bit < bits; bit++) {
419 digit = 1 + bit / 16;
423 if (digit <= r2[0] && (r2[digit] & (1<<smallbit))) {
424 dmsg(("bit %d\n", bit));
425 modmult(temp, result, modulus, tmp2);
426 add(tmp2, Zero, result);
430 modmult(temp, temp, modulus, tmp2);
431 add(tmp2, Zero, temp);
438 leave(("<modpow\n"));
443 int makekey(unsigned char *data, struct RSAKey *result,
444 unsigned char **keystr) {
445 unsigned char *p = data;
452 result->bits = (result->bits << 8) + *p++;
454 for (j=0; j<2; j++) {
460 result->bytes = b = (w+7)/8; /* bits -> bytes */
461 w = (w+15)/16; /* bits -> words */
465 if (keystr) *keystr = p; /* point at key string, second time */
469 for (i=0; i<b; i++) {
470 unsigned char byte = *p++;
472 bn[j][w-i/2] |= byte;
474 bn[j][w-i/2] |= byte<<8;
481 result->exponent = bn[0];
482 result->modulus = bn[1];
487 void rsaencrypt(unsigned char *data, int length, struct RSAKey *key) {
492 debug(key->exponent);
494 memmove(data+key->bytes-length, data, length);
498 for (i = 2; i < key->bytes-length-1; i++) {
500 data[i] = random_byte();
501 } while (data[i] == 0);
503 data[key->bytes-length-1] = 0;
505 w = (key->bytes+1)/2;
513 for (i=0; i<key->bytes; i++) {
514 unsigned char byte = *p++;
515 if ((key->bytes-i) & 1)
518 b1[w-i/2] |= byte<<8;
523 modpow(b1, key->exponent, key->modulus, b2);
528 for (i=0; i<key->bytes; i++) {
531 b = b2[w-i/2] & 0xFF;
541 int rsastr_len(struct RSAKey *key) {
546 return 4 * (ex[0]+md[0]) + 10;
549 void rsastr_fmt(char *str, struct RSAKey *key) {
556 for (i=1; i<=ex[0]; i++) {
557 sprintf(str+len, "%04x", ex[i]);
558 len += strlen(str+len);
561 for (i=1; i<=md[0]; i++) {
562 sprintf(str+len, "%04x", md[i]);
563 len += strlen(str+len);
580 unsigned short P1[2] = { 1, p1 };
581 unsigned short P2[2] = { 1, p2 };
582 unsigned short P3[2] = { 1, p3 };
583 unsigned short bigmod[5] = { 4, 0, 0, 0, 32768U };
584 unsigned short mod[5] = { 4, 0, 0, 0, 0 };
585 unsigned short a[5] = { 4, 0, 0, 0, 0 };
586 unsigned short b[5] = { 4, 0, 0, 0, 0 };
587 unsigned short c[5] = { 4, 0, 0, 0, 0 };
588 unsigned short One[2] = { 1, 1 };
589 unsigned short Two[2] = { 1, 2 };
592 modmult(P1, P2, bigmod, a); debug(a);
593 modmult(a, P3, bigmod, mod); debug(mod);
595 sub(P1, One, a); debug(a);
596 sub(P2, One, b); debug(b);
597 modmult(a, b, bigmod, c); debug(c);
598 sub(P3, One, a); debug(a);
599 modmult(a, c, bigmod, b); debug(b);
601 modpow(Two, b, mod, a); debug(a);