git.distorted.org.uk Git - u/mdw/putty/blob - sshrsa.c

   1 /*
   2  * RSA implementation just sufficient for ssh client-side
   3  * initialisation step
   4  *
   5  * Rewritten for more speed by Joris van Rantwijk, Jun 1999.
   6  */
   7
   8 #include <stdio.h>
   9 #include <stdlib.h>
  10 #include <string.h>
  11
  12 #if defined TESTMODE || defined RSADEBUG
  13 #ifndef DLVL
  14 #define DLVL 10000
  15 #endif
  16 #define debug(x) bndebug(#x,x)
  17 static int level = 0;
  18 static void bndebug(char *name, Bignum b) {
  19     int i;
  20     int w = 50-level-strlen(name)-5*b[0];
  21     if (level >= DLVL)
  22         return;
  23     if (w < 0) w = 0;
  24     dprintf("%*s%s%*s", level, "", name, w, "");
  25     for (i=b[0]; i>0; i--)
  26         dprintf(" %04x", b[i]);
  27     dprintf("\n");
  28 }
  29 #define dmsg(x) do {if(level<DLVL){dprintf("%*s",level,"");printf x;}} while(0)
  30 #define enter(x) do { dmsg(x); level += 4; } while(0)
  31 #define leave(x) do { level -= 4; dmsg(x); } while(0)
  32 #else
  33 #define debug(x)
  34 #define dmsg(x)
  35 #define enter(x)
  36 #define leave(x)
  37 #endif
  38
  39 #include "ssh.h"
  40
  41 int makekey(unsigned char *data, struct RSAKey *result,
  42             unsigned char **keystr) {
  43     unsigned char *p = data;
  44     Bignum bn[2];
  45     int i, j;
  46     int w, b;
  47
  48     result->bits = 0;
  49     for (i=0; i<4; i++)
  50         result->bits = (result->bits << 8) + *p++;
  51
  52     for (j=0; j<2; j++) {
  53
  54         w = 0;
  55         for (i=0; i<2; i++)
  56             w = (w << 8) + *p++;
  57
  58         result->bytes = b = (w+7)/8;   /* bits -> bytes */
  59         w = (w+15)/16;                 /* bits -> words */
  60
  61         bn[j] = newbn(w);
  62
  63         if (keystr) *keystr = p;       /* point at key string, second time */
  64
  65         for (i=1; i<=w; i++)
  66             bn[j][i] = 0;
  67         for (i=b; i-- ;) {
  68             unsigned char byte = *p++;
  69             if (i & 1)
  70                 bn[j][1+i/2] |= byte<<8;
  71             else
  72                 bn[j][1+i/2] |= byte;
  73         }
  74
  75         debug(bn[j]);
  76
  77     }
  78
  79     result->exponent = bn[0];
  80     result->modulus = bn[1];
  81
  82     return p - data;
  83 }
  84
  85 void rsaencrypt(unsigned char *data, int length, struct RSAKey *key) {
  86     Bignum b1, b2;
  87     int w, i;
  88     unsigned char *p;
  89
  90     debug(key->exponent);
  91
  92     memmove(data+key->bytes-length, data, length);
  93     data[0] = 0;
  94     data[1] = 2;
  95
  96     for (i = 2; i < key->bytes-length-1; i++) {
  97         do {
  98             data[i] = random_byte();
  99         } while (data[i] == 0);
 100     }
 101     data[key->bytes-length-1] = 0;
 102
 103     w = (key->bytes+1)/2;
 104
 105     b1 = newbn(w);
 106     b2 = newbn(w);
 107
 108     p = data;
 109     for (i=1; i<=w; i++)
 110         b1[i] = 0;
 111     for (i=key->bytes; i-- ;) {
 112         unsigned char byte = *p++;
 113         if (i & 1)
 114             b1[1+i/2] |= byte<<8;
 115         else
 116             b1[1+i/2] |= byte;
 117     }
 118
 119     debug(b1);
 120
 121     modpow(b1, key->exponent, key->modulus, b2);
 122
 123     debug(b2);
 124
 125     p = data;
 126     for (i=key->bytes; i-- ;) {
 127         unsigned char b;
 128         if (i & 1)
 129             b = b2[1+i/2] >> 8;
 130         else
 131             b = b2[1+i/2] & 0xFF;
 132         *p++ = b;
 133     }
 134
 135     freebn(b1);
 136     freebn(b2);
 137 }
 138
 139 int rsastr_len(struct RSAKey *key) {
 140     Bignum md, ex;
 141
 142     md = key->modulus;
 143     ex = key->exponent;
 144     return 4 * (ex[0]+md[0]) + 10;
 145 }
 146
 147 void rsastr_fmt(char *str, struct RSAKey *key) {
 148     Bignum md, ex;
 149     int len = 0, i;
 150
 151     md = key->modulus;
 152     ex = key->exponent;
 153
 154     for (i=1; i<=ex[0]; i++) {
 155         sprintf(str+len, "%04x", ex[i]);
 156         len += strlen(str+len);
 157     }
 158     str[len++] = '/';
 159     for (i=1; i<=md[0]; i++) {
 160         sprintf(str+len, "%04x", md[i]);
 161         len += strlen(str+len);
 162     }
 163     str[len] = '\0';
 164 }
 165
 166 #ifdef TESTMODE
 167
 168 #ifndef NODDY
 169 #define p1 10007
 170 #define p2 10069
 171 #define p3 10177
 172 #else
 173 #define p1 3
 174 #define p2 7
 175 #define p3 13
 176 #endif
 177
 178 unsigned short P1[2] = { 1, p1 };
 179 unsigned short P2[2] = { 1, p2 };
 180 unsigned short P3[2] = { 1, p3 };
 181 unsigned short bigmod[5] = { 4, 0, 0, 0, 32768U };
 182 unsigned short mod[5] = { 4, 0, 0, 0, 0 };
 183 unsigned short a[5] = { 4, 0, 0, 0, 0 };
 184 unsigned short b[5] = { 4, 0, 0, 0, 0 };
 185 unsigned short c[5] = { 4, 0, 0, 0, 0 };
 186 unsigned short One[2] = { 1, 1 };
 187 unsigned short Two[2] = { 1, 2 };
 188
 189 int main(void) {
 190     modmult(P1, P2, bigmod, a);   debug(a);
 191     modmult(a, P3, bigmod, mod);  debug(mod);
 192
 193     sub(P1, One, a);              debug(a);
 194     sub(P2, One, b);              debug(b);
 195     modmult(a, b, bigmod, c);     debug(c);
 196     sub(P3, One, a);              debug(a);
 197     modmult(a, c, bigmod, b);     debug(b);
 198
 199     modpow(Two, b, mod, a);       debug(a);
 200
 201     return 0;
 202 }
 203
 204 #endif