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/* SPDX-License-Identifier: GPL-3.0-or-later */
/*
* base64_decode.c
*
* Copyright (C) 2022 David Oberhollenzer <goliath@infraroot.at>
*/
#include "config.h"
#include "util/util.h"
#include "util/test.h"
#include <ctype.h>
static int base64_digit(int c)
{
if (isupper(c))
return c - 'A';
if (islower(c))
return c - 'a' + 26;
if (isdigit(c))
return c - '0' + 52;
if (c == '+')
return 62;
if (c == '/' || c == '-')
return 63;
return -1;
}
int base64_decode(const char *in, size_t in_len, sqfs_u8 *out, size_t *out_len)
{
int i1, i2, i3, i4;
size_t count = 0;
while (in_len >= 4) {
i1 = base64_digit(*(in++));
i2 = base64_digit(*(in++));
i3 = *(in++);
i4 = *(in++);
in_len -= 4;
if (i1 < 0 || i2 < 0 || count >= *out_len)
goto fail;
out[count++] = (i1 << 2) | (i2 >> 4);
if (i3 == '=' || i3 == '_') {
if ((i4 != '=' && i4 != '_') || in_len > 0)
goto fail;
break;
}
i3 = base64_digit(i3);
if (i3 < 0 || count >= *out_len)
goto fail;
out[count++] = ((i2 & 0x0F) << 4) | (i3 >> 2);
if (i4 == '=' || i4 == '_') {
if (in_len > 0)
goto fail;
break;
}
i4 = base64_digit(i4);
if (i4 < 0 || count >= *out_len)
goto fail;
out[count++] = ((i3 & 0x3) << 6) | i4;
}
/* libarchive has this bizarre bastardization of truncated base64 */
if (in_len > 0) {
if (in_len == 1)
goto fail;
i1 = base64_digit(*(in++));
i2 = base64_digit(*(in++));
in_len -= 2;
if (i1 < 0 || i2 < 0 || count >= *out_len)
goto fail;
out[count++] = (i1 << 2) | (i2 >> 4);
if (in_len > 0) {
i3 = *(in++);
--in_len;
if (i3 != '=' && i3 != '_') {
i3 = base64_digit(i3);
if (i3 < 0 || count >= *out_len)
goto fail;
out[count++] = ((i2 & 0x0F) << 4) | (i3 >> 2);
}
}
}
*out_len = count;
return 0;
fail:
*out_len = 0;
return -1;
}
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