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/* TEA based crypt(), version 0.0 <ndf@linux.mit.edu>
* It looks like there are problems with key bits carrying through
* to the encryted data, and I want to get rid of that libc call..
* This is just so rob could see it ;) */
/*
* I've:
* Compared the TEA implementation to a reference source - OK
* Noted the cycles count at 64 is twice the suggested value.
* Changed the types of 'n' and 'i' for better code with bcc.
* Removed a possible overrun of rkey by looping the values, it's now
* possible to _choose_ every bit of the 128bit PW with a 32 character word.
* Corrected the output transformation, it lost bits between words.
* Cleaned out all trace of the uncrypted PW from rkey.
*
* RDB.
*/
#include <stdlib.h>
char *
crypt(const char * key, const char * salt)
{
/* n is the number of cycles (2 rounds/cycle),
delta is a golden # derivative,
k is the key, v is the data to be encrypted. */
unsigned long v[2], sum=0, delta=0x9e3779b9, k[4];
int n=64, i, j;
static char rkey[16];
/* Our constant string will be a string of zeros .. */
v[0]=v[1]=k[0]=k[1]=k[2]=k[3]=0;
for(i=0;i<16;i++) rkey[i]=0;
rkey[0]=*salt;
rkey[1]=salt[1];
for (j=2,i=0;key[i];i++,j=((j+1)&15))
rkey[j]=(rkey[j]<<4)+(rkey[j]>>4)+ key[i];
memcpy(k, rkey, 4*sizeof(long));
while (n-->0) {
sum += delta;
v[0] += (v[1]<<4)+k[0] ^ v[1]+sum ^ (v[1]>>5)+k[1];
v[1] += (v[0]<<4)+k[2] ^ v[0]+sum ^ (v[0]>>5)+k[3];
}
/* Remove any trace of key */
for(i=0;i<16;i++) rkey[i]=0;
*rkey=*salt; rkey[1]=salt[1];
/* Now we need to unpack the bits and map it to "A-Za-z0-9./" for printing
in /etc/passwd */
sum=v[0];
for (i=2;i<13;i++)
{
/* This unpacks the 6 bit data, each cluster into its own byte */
rkey[i]=(sum&0x3F);
sum>>=6;
if(i==0+2) sum |= (v[1]<<26);
if(i==5+2) sum |= (v[1]>>4);
/* Now we map to the proper chars */
if (rkey[i]>=0 && rkey[i]<12) rkey[i]+=46;
else if (rkey[i]>11 && rkey[i]<38) rkey[i]+=53;
else if (rkey[i]>37 && rkey[i]<64) rkey[i]+=59;
else return NULL;
}
rkey[13]='\0';
return rkey;
}
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