зеркало из https://github.com/github/putty.git
413 строки
7.9 KiB
C
413 строки
7.9 KiB
C
/*
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* RSA implementation just sufficient for ssh client-side
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* initialisation step
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*/
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/*#include <windows.h>
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#define RSADEBUG
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#define DLVL 2
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#include "stel.h"*/
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#include <stdio.h>
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#include <stdlib.h>
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#include <string.h>
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#include "ssh.h"
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typedef unsigned short *Bignum;
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static unsigned short Zero[1] = { 0 };
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#if defined TESTMODE || defined RSADEBUG
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#ifndef DLVL
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#define DLVL 10000
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#endif
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#define debug(x) bndebug(#x,x)
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static int level = 0;
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static void bndebug(char *name, Bignum b) {
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int i;
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int w = 50-level-strlen(name)-5*b[0];
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if (level >= DLVL)
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return;
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if (w < 0) w = 0;
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dprintf("%*s%s%*s", level, "", name, w, "");
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for (i=b[0]; i>0; i--)
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dprintf(" %04x", b[i]);
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dprintf("\n");
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}
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#define dmsg(x) do {if(level<DLVL){dprintf("%*s",level,"");printf x;}} while(0)
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#define enter(x) do { dmsg(x); level += 4; } while(0)
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#define leave(x) do { level -= 4; dmsg(x); } while(0)
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#else
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#define debug(x)
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#define dmsg(x)
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#define enter(x)
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#define leave(x)
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#endif
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static Bignum newbn(int length) {
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Bignum b = malloc((length+1)*sizeof(unsigned short));
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if (!b)
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abort(); /* FIXME */
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b[0] = length;
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return b;
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}
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static void freebn(Bignum b) {
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free(b);
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}
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static int msb(Bignum r) {
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int i;
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int j;
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unsigned short n;
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for (i=r[0]; i>0; i--)
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if (r[i])
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break;
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j = (i-1)*16;
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n = r[i];
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if (n & 0xFF00) j += 8, n >>= 8;
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if (n & 0x00F0) j += 4, n >>= 4;
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if (n & 0x000C) j += 2, n >>= 2;
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if (n & 0x0002) j += 1, n >>= 1;
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return j;
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}
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static void add(Bignum r1, Bignum r2, Bignum result) {
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int i;
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long stuff = 0;
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enter((">add\n"));
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debug(r1);
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debug(r2);
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for (i = 1 ;; i++) {
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if (i <= r1[0])
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stuff += r1[i];
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if (i <= r2[0])
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stuff += r2[i];
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if (i <= result[0])
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result[i] = stuff & 0xFFFFU;
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if (i > r1[0] && i > r2[0] && i >= result[0])
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break;
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stuff >>= 16;
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}
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debug(result);
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leave(("<add\n"));
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}
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static void sub(Bignum r1, Bignum r2, Bignum result) {
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int i;
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long stuff = 0;
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enter((">sub\n"));
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debug(r1);
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debug(r2);
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for (i = 1 ;; i++) {
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if (i <= r1[0])
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stuff += r1[i];
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if (i <= r2[0])
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stuff -= r2[i];
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if (i <= result[0])
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result[i] = stuff & 0xFFFFU;
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if (i > r1[0] && i > r2[0] && i >= result[0])
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break;
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stuff = stuff<0 ? -1 : 0;
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}
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debug(result);
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leave(("<sub\n"));
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}
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static int ge(Bignum r1, Bignum r2) {
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int i;
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enter((">ge\n"));
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debug(r1);
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debug(r2);
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if (r1[0] < r2[0])
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i = r2[0];
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else
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i = r1[0];
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while (i > 0) {
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unsigned short n1 = (i > r1[0] ? 0 : r1[i]);
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unsigned short n2 = (i > r2[0] ? 0 : r2[i]);
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if (n1 > n2) {
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dmsg(("greater\n"));
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leave(("<ge\n"));
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return 1; /* r1 > r2 */
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} else if (n1 < n2) {
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dmsg(("less\n"));
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leave(("<ge\n"));
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return 0; /* r1 < r2 */
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}
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i--;
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}
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dmsg(("equal\n"));
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leave(("<ge\n"));
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return 1; /* r1 = r2 */
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}
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static void modmult(Bignum r1, Bignum r2, Bignum modulus, Bignum result) {
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Bignum temp = newbn(modulus[0]+1);
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Bignum tmp2 = newbn(modulus[0]+1);
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int i;
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int bit, bits, digit, smallbit;
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enter((">modmult\n"));
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debug(r1);
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debug(r2);
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debug(modulus);
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for (i=1; i<=result[0]; i++)
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result[i] = 0; /* result := 0 */
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for (i=1; i<=temp[0]; i++)
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temp[i] = (i > r2[0] ? 0 : r2[i]); /* temp := r2 */
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bits = 1+msb(r1);
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for (bit = 0; bit < bits; bit++) {
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digit = 1 + bit / 16;
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smallbit = bit % 16;
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debug(temp);
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if (digit <= r1[0] && (r1[digit] & (1<<smallbit))) {
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dmsg(("bit %d\n", bit));
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add(temp, result, tmp2);
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if (ge(tmp2, modulus))
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sub(tmp2, modulus, result);
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else
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add(tmp2, Zero, result);
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debug(result);
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}
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add(temp, temp, tmp2);
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if (ge(tmp2, modulus))
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sub(tmp2, modulus, temp);
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else
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add(tmp2, Zero, temp);
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}
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freebn(temp);
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freebn(tmp2);
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debug(result);
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leave(("<modmult\n"));
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}
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static void modpow(Bignum r1, Bignum r2, Bignum modulus, Bignum result) {
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Bignum temp = newbn(modulus[0]+1);
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Bignum tmp2 = newbn(modulus[0]+1);
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int i;
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int bit, bits, digit, smallbit;
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enter((">modpow\n"));
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debug(r1);
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debug(r2);
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debug(modulus);
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for (i=1; i<=result[0]; i++)
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result[i] = (i==1); /* result := 1 */
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for (i=1; i<=temp[0]; i++)
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temp[i] = (i > r1[0] ? 0 : r1[i]); /* temp := r1 */
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bits = 1+msb(r2);
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for (bit = 0; bit < bits; bit++) {
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digit = 1 + bit / 16;
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smallbit = bit % 16;
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debug(temp);
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if (digit <= r2[0] && (r2[digit] & (1<<smallbit))) {
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dmsg(("bit %d\n", bit));
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modmult(temp, result, modulus, tmp2);
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add(tmp2, Zero, result);
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debug(result);
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}
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modmult(temp, temp, modulus, tmp2);
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add(tmp2, Zero, temp);
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}
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freebn(temp);
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freebn(tmp2);
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debug(result);
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leave(("<modpow\n"));
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}
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int makekey(unsigned char *data, struct RSAKey *result,
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unsigned char **keystr) {
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unsigned char *p = data;
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Bignum bn[2];
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int i, j;
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int w, b;
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result->bits = 0;
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for (i=0; i<4; i++)
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result->bits = (result->bits << 8) + *p++;
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for (j=0; j<2; j++) {
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w = 0;
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for (i=0; i<2; i++)
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w = (w << 8) + *p++;
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result->bytes = b = (w+7)/8; /* bits -> bytes */
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w = (w+15)/16; /* bits -> words */
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bn[j] = newbn(w);
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if (keystr) *keystr = p; /* point at key string, second time */
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for (i=1; i<=w; i++)
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bn[j][i] = 0;
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for (i=0; i<b; i++) {
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unsigned char byte = *p++;
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if ((b-i) & 1)
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bn[j][w-i/2] |= byte;
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else
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bn[j][w-i/2] |= byte<<8;
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}
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debug(bn[j]);
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}
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result->exponent = bn[0];
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result->modulus = bn[1];
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return p - data;
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}
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void rsaencrypt(unsigned char *data, int length, struct RSAKey *key) {
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Bignum b1, b2;
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int w, i;
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unsigned char *p;
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debug(key->exponent);
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memmove(data+key->bytes-length, data, length);
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data[0] = 0;
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data[1] = 2;
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for (i = 2; i < key->bytes-length-1; i++) {
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do {
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data[i] = random_byte();
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} while (data[i] == 0);
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}
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data[key->bytes-length-1] = 0;
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w = (key->bytes+1)/2;
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b1 = newbn(w);
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b2 = newbn(w);
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p = data;
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for (i=1; i<=w; i++)
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b1[i] = 0;
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for (i=0; i<key->bytes; i++) {
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unsigned char byte = *p++;
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if ((key->bytes-i) & 1)
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b1[w-i/2] |= byte;
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else
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b1[w-i/2] |= byte<<8;
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}
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debug(b1);
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modpow(b1, key->exponent, key->modulus, b2);
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debug(b2);
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p = data;
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for (i=0; i<key->bytes; i++) {
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unsigned char b;
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if (i & 1)
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b = b2[w-i/2] & 0xFF;
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else
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b = b2[w-i/2] >> 8;
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*p++ = b;
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}
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freebn(b1);
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freebn(b2);
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}
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int rsastr_len(struct RSAKey *key) {
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Bignum md, ex;
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md = key->modulus;
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ex = key->exponent;
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return 4 * (ex[0]+md[0]) + 10;
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}
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void rsastr_fmt(char *str, struct RSAKey *key) {
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Bignum md, ex;
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int len = 0, i;
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md = key->modulus;
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ex = key->exponent;
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for (i=1; i<=ex[0]; i++) {
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sprintf(str+len, "%04x", ex[i]);
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len += strlen(str+len);
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}
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str[len++] = '/';
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for (i=1; i<=md[0]; i++) {
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sprintf(str+len, "%04x", md[i]);
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len += strlen(str+len);
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}
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str[len] = '\0';
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}
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#ifdef TESTMODE
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#ifndef NODDY
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#define p1 10007
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#define p2 10069
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#define p3 10177
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#else
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#define p1 3
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#define p2 7
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#define p3 13
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#endif
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unsigned short P1[2] = { 1, p1 };
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unsigned short P2[2] = { 1, p2 };
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unsigned short P3[2] = { 1, p3 };
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unsigned short bigmod[5] = { 4, 0, 0, 0, 32768U };
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unsigned short mod[5] = { 4, 0, 0, 0, 0 };
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unsigned short a[5] = { 4, 0, 0, 0, 0 };
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unsigned short b[5] = { 4, 0, 0, 0, 0 };
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unsigned short c[5] = { 4, 0, 0, 0, 0 };
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unsigned short One[2] = { 1, 1 };
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unsigned short Two[2] = { 1, 2 };
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int main(void) {
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modmult(P1, P2, bigmod, a); debug(a);
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modmult(a, P3, bigmod, mod); debug(mod);
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sub(P1, One, a); debug(a);
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sub(P2, One, b); debug(b);
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modmult(a, b, bigmod, c); debug(c);
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sub(P3, One, a); debug(a);
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modmult(a, c, bigmod, b); debug(b);
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modpow(Two, b, mod, a); debug(a);
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return 0;
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}
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#endif
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