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// SPDX-License-Identifier: LGPL-2.1+
/*
* Copyright (C) 2018 Red Hat, Inc.
* Copyright (C) 2015 - 2019 Jason A. Donenfeld <Jason@zx2c4.com>. All Rights Reserved.
*/
#include "nm-default.h"
#include "nm-secret-utils.h"
#include <malloc.h>
/*****************************************************************************/
void
nm_explicit_bzero(void *s, gsize n)
{
/* gracefully handle n == 0. This is important, callers rely on it. */
if (G_UNLIKELY(n == 0))
return;
nm_assert(s);
#if defined(HAVE_DECL_EXPLICIT_BZERO) && HAVE_DECL_EXPLICIT_BZERO
explicit_bzero(s, n);
#else
{
volatile guint8 *p = s;
memset(s, '\0', n);
while (n-- > 0)
*(p++) = '\0';
}
#endif
}
void
nm_free_secret(char *secret)
{
gsize len;
if (!secret)
return;
#if GLIB_CHECK_VERSION(2, 44, 0)
/* Here we mix malloc() and g_malloc() API. Usually we avoid this,
* however since glib 2.44.0 we are in fact guaranteed that g_malloc()/g_free()
* just wraps malloc()/free(), so this is actually fine.
*
* See https://gitlab.gnome.org/GNOME/glib/commit/3be6ed60aa58095691bd697344765e715a327fc1
*/
len = malloc_usable_size(secret);
#else
len = strlen(secret);
#endif
nm_explicit_bzero(secret, len);
g_free(secret);
}
/*****************************************************************************/
char *
nm_secret_strchomp(char *secret)
{
gsize len;
g_return_val_if_fail(secret, NULL);
/* it's actually identical to g_strchomp(). However,
* the glib function does not document, that it clears the
* memory. For @secret, we don't only want to truncate trailing
* spaces, we want to overwrite them with NUL. */
len = strlen(secret);
while (len--) {
if (g_ascii_isspace((guchar) secret[len]))
secret[len] = '\0';
else
break;
}
return secret;
}
/*****************************************************************************/
GBytes *
nm_secret_copy_to_gbytes(gconstpointer mem, gsize mem_len)
{
NMSecretBuf *b;
if (mem_len == 0)
return g_bytes_new_static("", 0);
nm_assert(mem);
/* NUL terminate the buffer.
*
* The entire buffer is already malloc'ed and likely has some room for padding.
* Thus, in many situations, this additional byte will cause no overhead in
* practice.
*
* Even if it causes an overhead, do it just for safety. Yes, the returned
* bytes is not a NUL terminated string and no user must rely on this. Do
* not treat binary data as NUL terminated strings, unless you know what
* you are doing. Anyway, defensive FTW.
*/
b = nm_secret_buf_new(mem_len + 1);
memcpy(b->bin, mem, mem_len);
b->bin[mem_len] = 0;
return nm_secret_buf_to_gbytes_take(b, mem_len);
}
/*****************************************************************************/
NMSecretBuf *
nm_secret_buf_new(gsize len)
{
NMSecretBuf *secret;
nm_assert(len > 0);
secret = g_malloc(sizeof(NMSecretBuf) + len);
*((gsize *) &(secret->len)) = len;
return secret;
}
static void
_secret_buf_free(gpointer user_data)
{
NMSecretBuf *secret = user_data;
nm_assert(secret);
nm_assert(secret->len > 0);
nm_explicit_bzero(secret->bin, secret->len);
g_free(user_data);
}
GBytes *
nm_secret_buf_to_gbytes_take(NMSecretBuf *secret, gssize actual_len)
{
nm_assert(secret);
nm_assert(secret->len > 0);
nm_assert(actual_len == -1 || (actual_len >= 0 && actual_len <= secret->len));
return g_bytes_new_with_free_func(secret->bin,
actual_len >= 0 ? (gsize) actual_len : secret->len,
_secret_buf_free,
secret);
}
/*****************************************************************************/
/**
* nm_utils_memeqzero_secret:
* @data: the data pointer to check (may be %NULL if @length is zero).
* @length: the number of bytes to check.
*
* Checks that all bytes are zero. This always takes the same amount
* of time to prevent timing attacks.
*
* Returns: whether all bytes are zero.
*/
gboolean
nm_utils_memeqzero_secret(gconstpointer data, gsize length)
{
const guint8 *const key = data;
volatile guint8 acc = 0;
gsize i;
for (i = 0; i < length; i++) {
acc |= key[i];
asm volatile("" : "=r"(acc) : "0"(acc));
}
return 1 & ((acc - 1) >> 8);
}
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