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/*
* Copyright (c) 2018 Balabit
*
* This library is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* License as published by the Free Software Foundation; either
* version 2.1 of the License, or (at your option) any later version.
*
* This library is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public
* License along with this library; if not, write to the Free Software
* Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
*
* As an additional exemption you are allowed to compile & link against the
* OpenSSL libraries as published by the OpenSSL project. See the file
* COPYING for details.
*
*/
#include <sys/mman.h>
#include <stddef.h>
#include <string.h>
#include <errno.h>
#include <unistd.h>
#include <stdio.h>
#include "nondumpable-allocator.h"
#define ALLOCATION_HEADER_SIZE offsetof(Allocation, user_data)
#define BUFFER_TO_ALLOCATION(buffer) ((Allocation *) ((guint8 *) buffer - ALLOCATION_HEADER_SIZE))
static void
_silent(gchar *summary, gchar *reason)
{
}
NonDumpableLogger logger_debug_fn INTERNAL = _silent;
NonDumpableLogger logger_fatal_fn INTERNAL = _silent;
void
nondumpable_setlogger(NonDumpableLogger _debug, NonDumpableLogger _fatal)
{
logger_debug_fn = _debug;
logger_fatal_fn = _fatal;
}
#define logger_debug(summary, fmt, ...) \
{ \
gchar *reason = g_strdup_printf(fmt, __VA_ARGS__); \
logger_debug_fn(summary, reason); \
g_free(reason); \
}
#define logger_fatal(summary, fmt, ...) \
{ \
gchar *reason = g_strdup_printf(fmt, __VA_ARGS__); \
logger_fatal_fn(summary, reason); \
g_free(reason); \
}
typedef struct
{
gsize alloc_size;
gsize data_len;
guint8 user_data[];
} Allocation;
static gboolean
_exclude_memory_from_core_dump(gpointer area, gsize len)
{
#if defined(MADV_DONTDUMP)
if (madvise(area, len, MADV_DONTDUMP) < 0)
{
if (errno == EINVAL)
{
logger_debug("secret storage: MADV_DONTDUMP not supported",
"len: %"G_GSIZE_FORMAT", errno: %d\n", len, errno);
return TRUE;
}
logger_fatal("secret storage: cannot madvise buffer", "errno: %d\n", errno);
return FALSE;
}
#endif
return TRUE;
}
static gpointer
_mmap(gsize len)
{
gpointer area = mmap(NULL, len, PROT_READ|PROT_WRITE, MAP_ANONYMOUS|MAP_PRIVATE, -1, 0);
if (area == MAP_FAILED)
{
logger_fatal("secret storage: cannot mmap buffer",
"len: %"G_GSIZE_FORMAT", errno: %d\n", len, errno);
return MAP_FAILED;
}
if (!_exclude_memory_from_core_dump(area, len))
goto err_munmap;
if (mlock(area, len) < 0)
{
gchar *hint = (errno == ENOMEM) ? ". Maybe RLIMIT_MEMLOCK is too small?" : "";
logger_fatal("secret storage: cannot lock buffer", "len: %"G_GSIZE_FORMAT", errno: %d%s\n", len, errno, hint);
goto err_munmap;
}
return area;
err_munmap:
munmap(area, len);
return MAP_FAILED;
}
static gsize
round_to_nearest(gsize number, gsize base)
{
return number + (base - (number % base));
}
gpointer
nondumpable_buffer_alloc(gsize len)
{
gsize minimum_size = len + ALLOCATION_HEADER_SIZE;
gsize pagesize = sysconf(_SC_PAGE_SIZE);
gsize alloc_size = round_to_nearest(minimum_size, pagesize);
Allocation *buffer = _mmap(alloc_size);
if (buffer == MAP_FAILED)
return NULL;
buffer->alloc_size = alloc_size;
buffer->data_len = len;
return buffer->user_data;
}
void
nondumpable_mem_zero(gpointer s, gsize len)
{
volatile guchar *p = s;
for (gsize i = 0; i < len; ++i)
p[i] = 0;
}
void
nondumpable_buffer_free(gpointer buffer)
{
Allocation *allocation = BUFFER_TO_ALLOCATION(buffer);
nondumpable_mem_zero(allocation->user_data, allocation->data_len);
munmap(allocation, allocation->alloc_size);
}
gpointer
nondumpable_buffer_realloc(gpointer buffer, gsize len)
{
Allocation *allocation = BUFFER_TO_ALLOCATION(buffer);
if (allocation->alloc_size >= len + ALLOCATION_HEADER_SIZE)
{
allocation->data_len = len;
return allocation->user_data;
}
gpointer new_buffer = nondumpable_buffer_alloc(len);
nondumpable_memcpy(new_buffer, allocation->user_data, allocation->data_len);
nondumpable_buffer_free(buffer);
return new_buffer;
}
/* glibc implementation of memcpy can use stack, exposing parts of the secrets */
gpointer
nondumpable_memcpy(gpointer dest, gpointer src, gsize len)
{
gchar *_dest = dest;
gchar *_src = src;
for (gsize i = 0; i < len; i++)
{
_dest[i] = _src[i];
}
return dest;
}
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