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view libtomcrypt/notes/etc/saferp_optimizer.c @ 1790:42745af83b7d

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Introduce extra delay before closing unauthenticated sessions To make it harder for attackers, introduce a delay to keep an unauthenticated session open a bit longer, thus blocking a connection slot until after the delay. Without this, while there is a limit on the amount of attempts an attacker can make at the same time (MAX_UNAUTH_PER_IP), the time taken by dropbear to handle one attempt is still short and thus for each of the allowed parallel attempts many attempts can be chained one after the other. The attempt rate is then: "MAX_UNAUTH_PER_IP / <process time of one attempt>". With the delay, this rate becomes: "MAX_UNAUTH_PER_IP / UNAUTH_CLOSE_DELAY".
author Thomas De Schampheleire <thomas.de_schampheleire@nokia.com>
date Wed, 15 Feb 2017 13:53:04 +0100
parents 6dba84798cd5
children
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/* emits an optimized version of LTC_SAFER+ ... only does encrypt so far... */

#include <stdio.h>
#include <string.h>

/* This is the "Armenian" Shuffle.  It takes the input from b and stores it in b2 */
#define SHUF\
    b2[0] = b[8]; b2[1] = b[11]; b2[2] = b[12]; b2[3] = b[15];   \
    b2[4] = b[2]; b2[5] = b[1]; b2[6] = b[6]; b2[7] = b[5];      \
    b2[8] = b[10]; b2[9] = b[9]; b2[10] = b[14]; b2[11] = b[13]; \
    b2[12] = b[0]; b2[13] = b[7]; b2[14] = b[4]; b2[15] = b[3]; memcpy(b, b2, sizeof(b));

/* This is the inverse shuffle.  It takes from b and gives to b2 */
#define iSHUF(b, b2)                                               \
    b2[0] = b[12]; b2[1] = b[5]; b2[2] = b[4]; b2[3] = b[15];      \
    b2[4] = b[14]; b2[5] = b[7]; b2[6] = b[6]; b2[7] = b[13];      \
    b2[8] = b[0]; b2[9] = b[9]; b2[10] = b[8]; b2[11] = b[1];      \
    b2[12] = b[2]; b2[13] = b[11]; b2[14] = b[10]; b2[15] = b[3]; memcpy(b, b2, sizeof(b));
    
#define ROUND(b, i)                                                                        \
    b[0]  = (safer_ebox[(b[0] ^ skey->saferp.K[i][0]) & 255] + skey->saferp.K[i+1][0]) & 255;    \
    b[1]  = safer_lbox[(b[1] + skey->saferp.K[i][1]) & 255] ^ skey->saferp.K[i+1][1];            \
    b[2]  = safer_lbox[(b[2] + skey->saferp.K[i][2]) & 255] ^ skey->saferp.K[i+1][2];            \
    b[3]  = (safer_ebox[(b[3] ^ skey->saferp.K[i][3]) & 255] + skey->saferp.K[i+1][3]) & 255;    \
    b[4]  = (safer_ebox[(b[4] ^ skey->saferp.K[i][4]) & 255] + skey->saferp.K[i+1][4]) & 255;    \
    b[5]  = safer_lbox[(b[5] + skey->saferp.K[i][5]) & 255] ^ skey->saferp.K[i+1][5];            \
    b[6]  = safer_lbox[(b[6] + skey->saferp.K[i][6]) & 255] ^ skey->saferp.K[i+1][6];            \
    b[7]  = (safer_ebox[(b[7] ^ skey->saferp.K[i][7]) & 255] + skey->saferp.K[i+1][7]) & 255;    \
    b[8]  = (safer_ebox[(b[8] ^ skey->saferp.K[i][8]) & 255] + skey->saferp.K[i+1][8]) & 255;    \
    b[9]  = safer_lbox[(b[9] + skey->saferp.K[i][9]) & 255] ^ skey->saferp.K[i+1][9];            \
    b[10] = safer_lbox[(b[10] + skey->saferp.K[i][10]) & 255] ^ skey->saferp.K[i+1][10];         \
    b[11] = (safer_ebox[(b[11] ^ skey->saferp.K[i][11]) & 255] + skey->saferp.K[i+1][11]) & 255; \
    b[12] = (safer_ebox[(b[12] ^ skey->saferp.K[i][12]) & 255] + skey->saferp.K[i+1][12]) & 255; \
    b[13] = safer_lbox[(b[13] + skey->saferp.K[i][13]) & 255] ^ skey->saferp.K[i+1][13];         \
    b[14] = safer_lbox[(b[14] + skey->saferp.K[i][14]) & 255] ^ skey->saferp.K[i+1][14];         \
    b[15] = (safer_ebox[(b[15] ^ skey->saferp.K[i][15]) & 255] + skey->saferp.K[i+1][15]) & 255;        

int main(void)
{
   int b[16], b2[16], x, y, z;
   
/* -- ENCRYPT ---  */
   for (x = 0; x < 16; x++) b[x] = x;
   /* emit encrypt preabmle  */
printf(
"void saferp_ecb_encrypt(const unsigned char *pt, unsigned char *ct, symmetric_key *skey)\n"
"{\n"
"   int x;\n"
"   unsigned char b[16];\n"
"\n"
"   LTC_ARGCHK(pt   != NULL);\n"
"   LTC_ARGCHK(ct   != NULL);\n"
"   LTC_ARGCHK(skey != NULL);\n"
"\n"
"   /* do eight rounds */\n"
"   for (x = 0; x < 16; x++) {\n"
"       b[x] = pt[x];\n"
"   }\n");   

   /* do 8 rounds of ROUND; LT; */
   for (x = 0; x < 8; x++) {
       /* ROUND(..., x*2) */
       for (y = 0; y < 16; y++) {
printf("b[%d] = (safer_%cbox[(b[%d] %c skey->saferp.K[%d][%d]) & 255] %c skey->saferp.K[%d][%d]) & 255;\n",
          b[y], "elle"[y&3], b[y], "^++^"[y&3],      x*2, y, "+^^+"[y&3], x*2+1, y);
       }
       
       /* LT */
       for (y = 0; y < 4; y++) {
printf("   b[%d]  = (b[%d] + (b[%d] = (b[%d] + b[%d]) & 255)) & 255;\n", b[0], b[0], b[1], b[0], b[1]);
printf("   b[%d]  = (b[%d] + (b[%d] = (b[%d] + b[%d]) & 255)) & 255;\n", b[2], b[2], b[3], b[3], b[2]);
printf("   b[%d]  = (b[%d] + (b[%d] = (b[%d] + b[%d]) & 255)) & 255;\n", b[4], b[4], b[5], b[5], b[4]);
printf("   b[%d]  = (b[%d] + (b[%d] = (b[%d] + b[%d]) & 255)) & 255;\n", b[6], b[6], b[7], b[7], b[6]);
printf("   b[%d]  = (b[%d] + (b[%d] = (b[%d] + b[%d]) & 255)) & 255;\n", b[8], b[8], b[9], b[9], b[8]);
printf("   b[%d]  = (b[%d] + (b[%d] = (b[%d] + b[%d]) & 255)) & 255;\n", b[10], b[10], b[11], b[11], b[10]);
printf("   b[%d]  = (b[%d] + (b[%d] = (b[%d] + b[%d]) & 255)) & 255;\n", b[12], b[12], b[13], b[13], b[12]);
printf("   b[%d]  = (b[%d] + (b[%d] = (b[%d] + b[%d]) & 255)) & 255;\n", b[14], b[14], b[15], b[15], b[14]);
      if (y < 3) {
         SHUF;
      }         
      }   
  }
  
printf(
"   if (skey->saferp.rounds <= 8) {\n");
/* finish */
   for (x = 0; x < 16; x++) {
   printf(
"      ct[%d] = (b[%d] %c skey->saferp.K[skey->saferp.rounds*2][%d]) & 255;\n",
       x, b[x], "^++^"[x&3], x);
   }   
   printf("      return;\n   }\n");
  
  /* 192-bit keys */
printf(  
"   /* 192-bit key? */\n"
"   if (skey->saferp.rounds > 8) {\n");
  
   /* do 4 rounds of ROUND; LT; */
   for (x = 8; x < 12; x++) {
       /* ROUND(..., x*2) */
       for (y = 0; y < 16; y++) {
printf("b[%d] = (safer_%cbox[(b[%d] %c skey->saferp.K[%d][%d]) & 255] %c skey->saferp.K[%d][%d]) & 255;\n",
          b[y], "elle"[y&3], b[y], "^++^"[y&3],      x*2, y, "+^^+"[y&3], x*2+1, y);
       }
       
       /* LT */
       for (y = 0; y < 4; y++) {
printf("   b[%d]  = (b[%d] + (b[%d] = (b[%d] + b[%d]) & 255)) & 255;\n", b[0], b[0], b[1], b[0], b[1]);
printf("   b[%d]  = (b[%d] + (b[%d] = (b[%d] + b[%d]) & 255)) & 255;\n", b[2], b[2], b[3], b[3], b[2]);
printf("   b[%d]  = (b[%d] + (b[%d] = (b[%d] + b[%d]) & 255)) & 255;\n", b[4], b[4], b[5], b[5], b[4]);
printf("   b[%d]  = (b[%d] + (b[%d] = (b[%d] + b[%d]) & 255)) & 255;\n", b[6], b[6], b[7], b[7], b[6]);
printf("   b[%d]  = (b[%d] + (b[%d] = (b[%d] + b[%d]) & 255)) & 255;\n", b[8], b[8], b[9], b[9], b[8]);
printf("   b[%d]  = (b[%d] + (b[%d] = (b[%d] + b[%d]) & 255)) & 255;\n", b[10], b[10], b[11], b[11], b[10]);
printf("   b[%d]  = (b[%d] + (b[%d] = (b[%d] + b[%d]) & 255)) & 255;\n", b[12], b[12], b[13], b[13], b[12]);
printf("   b[%d]  = (b[%d] + (b[%d] = (b[%d] + b[%d]) & 255)) & 255;\n", b[14], b[14], b[15], b[15], b[14]);
      if (y < 3) {
         SHUF;
      }         
      }   
  }
printf("}\n");
  
printf(
"   if (skey->saferp.rounds <= 12) {\n");
/* finish */
   for (x = 0; x < 16; x++) {
   printf(
"      ct[%d] = (b[%d] %c skey->saferp.K[skey->saferp.rounds*2][%d]) & 255;\n",
       x, b[x], "^++^"[x&3], x);
   }   
   printf("      return;\n   }\n");

  /* 256-bit keys */
printf(  
"   /* 256-bit key? */\n"
"   if (skey->saferp.rounds > 12) {\n");
  
   /* do 4 rounds of ROUND; LT; */
   for (x = 12; x < 16; x++) {
       /* ROUND(..., x*2) */
       for (y = 0; y < 16; y++) {
printf("b[%d] = (safer_%cbox[(b[%d] %c skey->saferp.K[%d][%d]) & 255] %c skey->saferp.K[%d][%d]) & 255;\n",
          b[y], "elle"[y&3], b[y], "^++^"[y&3],      x*2, y, "+^^+"[y&3], x*2+1, y);
       }
       
       /* LT */
       for (y = 0; y < 4; y++) {
printf("   b[%d]  = (b[%d] + (b[%d] = (b[%d] + b[%d]) & 255)) & 255;\n", b[0], b[0], b[1], b[0], b[1]);
printf("   b[%d]  = (b[%d] + (b[%d] = (b[%d] + b[%d]) & 255)) & 255;\n", b[2], b[2], b[3], b[3], b[2]);
printf("   b[%d]  = (b[%d] + (b[%d] = (b[%d] + b[%d]) & 255)) & 255;\n", b[4], b[4], b[5], b[5], b[4]);
printf("   b[%d]  = (b[%d] + (b[%d] = (b[%d] + b[%d]) & 255)) & 255;\n", b[6], b[6], b[7], b[7], b[6]);
printf("   b[%d]  = (b[%d] + (b[%d] = (b[%d] + b[%d]) & 255)) & 255;\n", b[8], b[8], b[9], b[9], b[8]);
printf("   b[%d]  = (b[%d] + (b[%d] = (b[%d] + b[%d]) & 255)) & 255;\n", b[10], b[10], b[11], b[11], b[10]);
printf("   b[%d]  = (b[%d] + (b[%d] = (b[%d] + b[%d]) & 255)) & 255;\n", b[12], b[12], b[13], b[13], b[12]);
printf("   b[%d]  = (b[%d] + (b[%d] = (b[%d] + b[%d]) & 255)) & 255;\n", b[14], b[14], b[15], b[15], b[14]);
      if (y < 3) {
         SHUF;
      }         
      }   
  }
/* finish */
   for (x = 0; x < 16; x++) {
   printf(
"      ct[%d] = (b[%d] %c skey->saferp.K[skey->saferp.rounds*2][%d]) & 255;\n",
       x, b[x], "^++^"[x&3], x);
   }   
   printf("   return;\n");
printf("   }\n}\n\n");

   return 0;
}


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