134 lines
2.7 KiB
C
134 lines
2.7 KiB
C
/* simple XXTEA en/decrypt utility
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*
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* BSD Licence
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*
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* btea function is from
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* <https://secure.wikimedia.org/wikipedia/en/wiki/XXTEA#Reference_code>
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*
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* (c) by Sec <sec@42.org> 6/2011
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*/
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#include <stdint.h>
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#define DELTA 0x9e3779b9
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#define MX (((z>>5^y<<2) + (y>>3^z<<4)) ^ ((sum^y) + (k[(p&3)^e] ^ z)))
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#include "xxtea.h"
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uint32_t charp2uint32(uint8_t *data, uint8_t bytes)
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{
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uint32_t r = 0;
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if( bytes ){
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r |= *data++;
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}
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if( bytes > 1){
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r<<=8;
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r |= *data++;
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}
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if( bytes > 2){
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r<<=8;
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r |= *data++;
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}
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if( bytes > 3){
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r<<=8;
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r |= *data++;
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}
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return r;
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}
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void charp2uint32p(uint8_t* data, uint8_t n, uint32_t *v)
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{
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int i,j=0;
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int fullwords = n/4;
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for(i=0; i<fullwords*4; i+=4){
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v[j++] = charp2uint32(data+i,4);
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}
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uint8_t extrabytes = n - i;
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v[j] = charp2uint32(data+i,extrabytes);
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}
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void uint322charp(uint32_t data, uint8_t *buf, uint8_t bytes)
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{
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if( bytes ){
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buf[0] = data>>24;
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if( bytes > 1)
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buf[1] = (data>>16)&0xFF;
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if( bytes > 2)
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buf[2] = (data>>8)&0xFF;
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if( bytes > 3)
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buf[3] = (data>>0)&0xFF;
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}
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void uint32p2charp(uint8_t* data, uint8_t n, uint32_t *v)
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{
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int i;
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int fullwords = n/4;
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for(i=0; i<fullwords; i++){
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uint322charp(v[i],data+i*4,4);
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}
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uint8_t extrabytes = n - fullwords*4;
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uint322charp(v[i],data+i*4,extrabytes);
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}
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void xxtea_encode(uint8_t *data, int n, uint32_t const k[4])
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{
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uint32_t v[8]; //maximum 32 bytes
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int words = (n+3)/4;
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if( words > 8 )
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return;
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charp2uint32p(data, n, v);
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xxtea_encode_words(v, words, k);
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uint32p2charp(data, n, v);
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}
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void xxtea_decode(uint8_t *data, int n, uint32_t const k[4])
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{
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uint32_t v[8]; //maximum 32 bytes
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int words = (n+3)/4;
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if( words > 8 )
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return;
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charp2uint32p(data, n, v);
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xxtea_decode_words(v, words, k);
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uint32p2charp(data, n, v);
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}
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void xxtea_encode_words(uint32_t *v, int n, uint32_t const k[4])
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{
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uint32_t y, z, sum;
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unsigned p, rounds, e;
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rounds = 6 + 52/n;
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sum = 0;
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z = v[n-1];
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do {
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sum += DELTA;
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e = (sum >> 2) & 3;
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for (p=0; p<n-1; p++) {
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y = v[p+1];
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z = v[p] += MX;
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}
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y = v[0];
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z = v[n-1] += MX;
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} while (--rounds);
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}
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void xxtea_decode_words(uint32_t *v, int n, uint32_t const k[4]) {
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uint32_t y, z, sum;
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unsigned p, rounds, e;
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rounds = 6 + 52/n;
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sum = rounds*DELTA;
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y = v[0];
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do {
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e = (sum >> 2) & 3;
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for (p=n-1; p>0; p--) {
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z = v[p-1];
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y = v[p] -= MX;
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}
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z = v[n-1];
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y = v[0] -= MX;
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} while ((sum -= DELTA) != 0);
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}
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