1// Copyright (c) 2012 The Chromium Authors. All rights reserved.
2// Use of this source code is governed by a BSD-style license that can be
3// found in the LICENSE file.
4
5// This is a list of environment variables which the ELF loader unsets when
6// loading a SUID binary. Because they are unset rather than just ignored, they
7// aren't passed to child processes of SUID processes either.
8//
9// We need to save these environment variables before running a SUID sandbox
10// and restore them before running child processes (but after dropping root).
11//
12// List gathered from glibc sources (00ebd7ed58df389a78e41dece058048725cb585e):
13//   sysdeps/unix/sysv/linux/i386/dl-librecon.h
14//   sysdeps/generic/unsecvars.h
15
16#ifndef SANDBOX_LINUX_SUID_SUID_UNSAFE_ENVIRONMENT_VARIABLES_H_
17#define SANDBOX_LINUX_SUID_SUID_UNSAFE_ENVIRONMENT_VARIABLES_H_
18
19#include <stdint.h>
20#include <stdlib.h>  // malloc
21#include <string.h>  // memcpy
22
23static const char* kSUIDUnsafeEnvironmentVariables[] = {
24  "LD_AOUT_LIBRARY_PATH",
25  "LD_AOUT_PRELOAD",
26  "GCONV_PATH",
27  "GETCONF_DIR",
28  "HOSTALIASES",
29  "LD_AUDIT",
30  "LD_DEBUG",
31  "LD_DEBUG_OUTPUT",
32  "LD_DYNAMIC_WEAK",
33  "LD_LIBRARY_PATH",
34  "LD_ORIGIN_PATH",
35  "LD_PRELOAD",
36  "LD_PROFILE",
37  "LD_SHOW_AUXV",
38  "LD_USE_LOAD_BIAS",
39  "LOCALDOMAIN",
40  "LOCPATH",
41  "MALLOC_TRACE",
42  "NIS_PATH",
43  "NLSPATH",
44  "RESOLV_HOST_CONF",
45  "RES_OPTIONS",
46  "TMPDIR",
47  "TZDIR",
48  NULL,
49};
50
51// Return a malloc allocated string containing the 'saved' environment variable
52// name for a given environment variable.
53static inline char* SandboxSavedEnvironmentVariable(const char* envvar) {
54  const size_t envvar_len = strlen(envvar);
55  const size_t kMaxSizeT = (size_t) -1;
56
57  if (envvar_len > kMaxSizeT - 1 - 8)
58    return NULL;
59
60  const size_t saved_envvarlen = envvar_len + 1 /* NUL terminator */ +
61                                              8 /* strlen("SANDBOX_") */;
62  char* const saved_envvar = (char*) malloc(saved_envvarlen);
63  if (!saved_envvar)
64    return NULL;
65
66  memcpy(saved_envvar, "SANDBOX_", 8);
67  memcpy(saved_envvar + 8, envvar, envvar_len);
68  saved_envvar[8 + envvar_len] = 0;
69
70  return saved_envvar;
71}
72
73#endif  // SANDBOX_LINUX_SUID_SUID_UNSAFE_ENVIRONMENT_VARIABLES_H_
74