/*
 *  Copyright 2014-2022 The GmSSL Project. All Rights Reserved.
 *
 *  Licensed under the Apache License, Version 2.0 (the License); you may
 *  not use this file except in compliance with the License.
 *
 *  http://www.apache.org/licenses/LICENSE-2.0
 */



#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <stdint.h>
#include <gmssl/error.h>

static int OPENSSL_hexchar2int(unsigned char c)
{
    switch (c) {
    case '0':
        return 0;
    case '1':
        return 1;
    case '2':
        return 2;
    case '3':
        return 3;
    case '4':
          return 4;
    case '5':
          return 5;
    case '6':
          return 6;
    case '7':
          return 7;
    case '8':
          return 8;
    case '9':
          return 9;
    case 'a':
    case 'A':
          return 0x0A;
    case 'b': case 'B':
          return 0x0B;
    case 'c': case 'C':
          return 0x0C;
    case 'd': case 'D':
          return 0x0D;
    case 'e': case 'E':
          return 0x0E;
    case 'f': case 'F':
          return 0x0F;
    }
    return -1;
}

static unsigned char *OPENSSL_hexstr2buf(const char *str, size_t *len)
{
    unsigned char *hexbuf, *q;
    unsigned char ch, cl;
    int chi, cli;
    const unsigned char *p;
    size_t s;

    s = strlen(str);
    if ((hexbuf = malloc(s >> 1)) == NULL) {
        return NULL;
    }
    for (p = (const unsigned char *)str, q = hexbuf; *p; ) {
        ch = *p++;
        if (ch == ':')
            continue;
        cl = *p++;
        if (!cl) {
            //CRYPTOerr(CRYPTO_F_OPENSSL_HEXSTR2BUF, CRYPTO_R_ODD_NUMBER_OF_DIGITS);
            free(hexbuf);
            return NULL;
        }
        cli = OPENSSL_hexchar2int(cl);
        chi = OPENSSL_hexchar2int(ch);
        if (cli < 0 || chi < 0) {
            free(hexbuf);
            //CRYPTOerr(CRYPTO_F_OPENSSL_HEXSTR2BUF, CRYPTO_R_ILLEGAL_HEX_DIGIT);
            return NULL;
        }
        *q++ = (unsigned char)((chi << 4) | cli);
    }

    if (len)
        *len = q - hexbuf;
    return hexbuf;
}


static int hexchar2int(char c)
{
	if      ('0' <= c && c <= '9') return c - '0';
	else if ('a' <= c && c <= 'f') return c - 'a' + 10;
	else if ('A' <= c && c <= 'F') return c - 'A' + 10;
	else return -1;
}

int hex2bin(const char *in, size_t inlen, uint8_t *out)
{
	int c;
	if (inlen % 2) {
		error_print_msg("hex %s len = %zu\n", in, inlen);
		return -1;
	}

	while (inlen) {
		if ((c = hexchar2int(*in++)) < 0) {
			error_print();
			return -1;
		}
		*out = (uint8_t)c << 4;
		if ((c = hexchar2int(*in++)) < 0) {
			error_print();
			return -1;
		}
		*out |= (uint8_t)c;
		inlen -= 2;
		out++;
	}
	return 1;
}

int hex_to_bytes(const char *in, size_t inlen, uint8_t *out, size_t *outlen)
{
	*outlen = inlen/2;
	return hex2bin(in, inlen, out);
}


void memxor(void *r, const void *a, size_t len)
{
	uint8_t *pr = r;
	const uint8_t *pa = a;
	size_t i;
	for (i = 0; i < len; i++) {
		pr[i] ^= pa[i];
	}

}


void gmssl_memxor(void *r, const void *a, const void *b, size_t len)
{
	uint8_t *pr = r;
	const uint8_t *pa = a;
	const uint8_t *pb = b;
	size_t i;
	for (i = 0; i < len; i++) {
		pr[i] = pa[i] ^ pb[i];
	}
}


// Note: comments and code from OpenSSL crypto/cryptlib.c:CRYPTO_memcmp()
/* volatile unsigned char* pointers are there because
 * 1. Accessing a variable declared volatile via a pointer
 *    that lacks a volatile qualifier causes undefined behavior.
 * 2. When the variable itself is not volatile the compiler is
 *    not required to keep all those reads and can convert
 *    this into canonical memcmp() which doesn't read the whole block.
 * Pointers to volatile resolve the first problem fully. The second
 * problem cannot be resolved in any Standard-compliant way but this
 * works the problem around. Compilers typically react to
 * pointers to volatile by preserving the reads and writes through them.
 * The latter is not required by the Standard if the memory pointed to
 * is not volatile.
 * Pointers themselves are volatile in the function signature to work
 * around a subtle bug in gcc 4.6+ which causes writes through
 * pointers to volatile to not be emitted in some rare,
 * never needed in real life, pieces of code.
 */
int gmssl_secure_memcmp(const volatile void * volatile in_a, const volatile void * volatile in_b, size_t len)
{
	size_t i;
	const volatile unsigned char *a = in_a;
	const volatile unsigned char *b = in_b;
	unsigned char x = 0;

	for (i = 0; i < len; i++) {
		x |= a[i] ^ b[i];
	}

	return x;
}

/*
 * Pointer to memset is volatile so that compiler must de-reference
 * the pointer and can't assume that it points to any function in
 * particular (such as memset, which it then might further "optimize")
 */
typedef void *(*memset_t)(void *, int, size_t);

static volatile memset_t memset_func = memset;

void gmssl_secure_clear(void *ptr, size_t len)
{
	memset_func(ptr, 0, len);
}

int mem_is_zero(const uint8_t *buf, size_t len)
{
	int ret = 1;
	size_t i;
	for (i = 0; i < len; i++) {
		if (buf[i]) ret = 0;
	}
	return ret;
}