compilers/linux86-0.16.17/libc/misc/crypt.c

   1 /* TEA based crypt(), version 0.0 <ndf@linux.mit.edu>
   2  * It looks like there are problems with key bits carrying through
   3  * to the encryted data, and I want to get rid of that libc call..
   4  * This is just so rob could see it ;) */
   5
   6 /*
   7  * I've:
   8  *   Compared the TEA implementation to a reference source - OK
   9  *   Reduced the cycles count from 64 to 32 (the suggested value)
  10  *   Changed the types of 'n' and 'i' for better code with bcc.
  11  *   Removed a possible overrun of rkey by looping the values, it's now
  12  *   possible to _choose_ every bit of the 128bit PW with a 32 character word.
  13  *   Corrected the output transformation, it lost bits between words.
  14  *   Cleaned out all trace of the uncrypted PW from rkey.
  15  *
  16  *  RDB.
  17  */
  18
  19 #include <stdlib.h>
  20
  21 char *
  22 crypt(const char * key, const char * salt)
  23 {
  24   /* n is the number of cycles (2 rounds/cycle),
  25      delta is a golden # derivative,
  26      k is the key, v is the data to be encrypted. */
  27
  28   unsigned long v[2], sum=0, delta=0x9e3779b9, k[4];
  29   int n=32, i, j;
  30   static char rkey[16];
  31
  32   /* Our constant string will be a string of zeros .. */
  33   v[0]=v[1]=k[0]=k[1]=k[2]=k[3]=0;
  34   for(i=0;i<16;i++) rkey[i]=0;
  35
  36   rkey[0]=*salt;
  37   rkey[1]=salt[1];
  38   for (j=2,i=0;key[i];i++,j=((j+1)&15))
  39      rkey[j]=(rkey[j]<<4)+(rkey[j]>>4)+ key[i];
  40
  41   memcpy(k, rkey, 4*sizeof(long));
  42
  43   while (n-->0) {
  44     sum += delta;
  45     v[0] += (v[1]<<4)+k[0] ^ v[1]+sum ^ (v[1]>>5)+k[1];
  46     v[1] += (v[0]<<4)+k[2] ^ v[0]+sum ^ (v[0]>>5)+k[3];
  47   }
  48
  49   /* Remove any trace of key */
  50   for(i=0;i<16;i++) rkey[i]=0;
  51   *rkey=*salt; rkey[1]=salt[1];
  52
  53   /* Now we need to unpack the bits and map it to "A-Za-z0-9./" for printing
  54      in /etc/passwd */
  55   sum=v[0];
  56   for (i=2;i<13;i++)
  57     {
  58       /* This unpacks the 6 bit data, each cluster into its own byte */
  59       rkey[i]=(sum&0x3F);
  60       sum>>=6;
  61       if(i==0+2) sum |= (v[1]<<26);
  62       if(i==5+2) sum |= (v[1]>>4);
  63
  64       /* Now we map to the proper chars */
  65       if (rkey[i]>=0 && rkey[i]<12) rkey[i]+=46;
  66       else if (rkey[i]>11 && rkey[i]<38) rkey[i]+=53;
  67       else if (rkey[i]>37 && rkey[i]<64) rkey[i]+=59;
  68       else return NULL;
  69     }
  70
  71   rkey[13]='\0';
  72   return rkey;
  73 }