79 linhas
2.2 KiB
C
79 linhas
2.2 KiB
C
/*
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prg.c version 20150811
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Andreas Hülsing
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Public domain.
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*/
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#include "chacha.h"
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#include "prg.h"
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#include <stdio.h>
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#include <openssl/sha.h>
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#include <openssl/hmac.h>
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#include <openssl/evp.h>
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const unsigned char zero_nonce[12] = {0};
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/**
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* Generates rlen output bytes using ChaCha20 with a zero nonce and counter = 0
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*/
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void prg(unsigned char *r, unsigned long long rlen, const unsigned char *key, unsigned int key_len)
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{
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if (key_len == 32) {
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CRYPTO_chacha_20_keystream(r, rlen, key, zero_nonce, 0);
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}
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else {
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if (key_len == 64) {
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unsigned long long left = rlen;
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u_int32_t counter = 0;
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unsigned char *c = (unsigned char*)&counter;
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unsigned int length;
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unsigned int i = 0;
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unsigned char tmp[64];
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while (left > 0) {
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HMAC(EVP_sha512(), key, key_len, c , 4, tmp, &length);
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if (length != 64) {
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fprintf(stderr, "HMAC outputs %d bytes... That should not happen...", length);
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}
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for (i = 0; ((i < length) && (i < left)); i++) {
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r[rlen-left+i] = tmp[i];
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}
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left -= length;
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counter++;
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}
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}
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else {
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fprintf(stderr,"prg.c:: Code only supports 32 byte and 64 byte seeds");
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}
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}
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}
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/**
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* Generates n output bytes using ChaCha20 (n=32) or HMAC-SHA2-512 (n=64).
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*
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* For ChaCha, nonce and counter are set depending on the address addr. For HMAC, addr is used as message.
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*/
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void prg_with_counter(unsigned char *r, const unsigned char *key, unsigned int n, const unsigned char addr[16])
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{
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int i;
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unsigned char nonce[12];
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if (n == 32) {
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for (i = 0; i < 12; i++) {
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nonce[i] = addr[i];
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}
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uint32_t counter;
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counter = (((uint32_t)addr[12]) << 24) | (((uint32_t)addr[13]) << 16) | (((uint32_t)addr[14]) << 8) | addr[15];
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// TODO: Check address handling. Endianess?
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CRYPTO_chacha_20_keystream(r, n, key, nonce, counter);
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}
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else {
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if (n == 64) {
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unsigned int length;
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HMAC(EVP_sha512(), key, n, addr, 16, r, &length);
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if (length != 64) {
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fprintf(stderr, "HMAC outputs %d bytes... That should not happen...", length);
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}
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}
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else {
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fprintf(stderr,"prg.c:: Code only supports 32 byte and 64 byte seeds");
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}
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}
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} |