1 | /* $Id: SUPR3HardenedMain-darwin.cpp 99739 2023-05-11 01:01:08Z vboxsync $ */
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2 | /** @file
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3 | * VirtualBox Support Library - Hardened main(), posix bits.
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4 | */
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5 |
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6 | /*
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7 | * Copyright (C) 2017-2023 Oracle and/or its affiliates.
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8 | *
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9 | * This file is part of VirtualBox base platform packages, as
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10 | * available from https://www.virtualbox.org.
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11 | *
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12 | * This program is free software; you can redistribute it and/or
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13 | * modify it under the terms of the GNU General Public License
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14 | * as published by the Free Software Foundation, in version 3 of the
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15 | * License.
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16 | *
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17 | * This program is distributed in the hope that it will be useful, but
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18 | * WITHOUT ANY WARRANTY; without even the implied warranty of
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19 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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20 | * General Public License for more details.
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21 | *
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22 | * You should have received a copy of the GNU General Public License
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23 | * along with this program; if not, see <https://www.gnu.org/licenses>.
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24 | *
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25 | * The contents of this file may alternatively be used under the terms
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26 | * of the Common Development and Distribution License Version 1.0
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27 | * (CDDL), a copy of it is provided in the "COPYING.CDDL" file included
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28 | * in the VirtualBox distribution, in which case the provisions of the
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29 | * CDDL are applicable instead of those of the GPL.
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30 | *
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31 | * You may elect to license modified versions of this file under the
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32 | * terms and conditions of either the GPL or the CDDL or both.
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33 | *
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34 | * SPDX-License-Identifier: GPL-3.0-only OR CDDL-1.0
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35 | */
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36 |
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37 |
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38 | /*********************************************************************************************************************************
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39 | * Header Files *
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40 | *********************************************************************************************************************************/
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41 | #include <VBox/err.h>
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42 | #include <VBox/sup.h>
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43 |
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44 | #include <iprt/path.h>
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45 | #include <iprt/string.h>
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46 |
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47 | #include <dlfcn.h>
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48 | #include <sys/mman.h>
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49 | #include <errno.h>
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50 | #include <sys/sysctl.h> /* sysctlbyname() */
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51 | #include <stdio.h>
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52 | #include <stdint.h>
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53 | #include <unistd.h> /* issetugid() */
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54 | #include <mach-o/dyld.h>
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55 |
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56 | #include "SUPLibInternal.h"
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57 |
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58 |
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59 | /*********************************************************************************************************************************
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60 | * Defined Constants And Macros *
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61 | *********************************************************************************************************************************/
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62 |
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63 |
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64 | /*********************************************************************************************************************************
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65 | * Structures and Typedefs *
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66 | *********************************************************************************************************************************/
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67 |
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68 | /**
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69 | * Interpose table entry.
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70 | */
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71 | typedef struct DYLDINTERPOSE
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72 | {
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73 | /** The symbol address to replace with. */
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74 | const void *pvReplacement;
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75 | /** The replaced symbol address. */
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76 | const void *pvReplacee;
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77 | } DYLDINTERPOSE;
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78 | /** Pointer to an interposer table entry. */
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79 | typedef DYLDINTERPOSE *PDYLDINTERPOSE;
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80 | /** Pointer to a const interposer table entry. */
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81 | typedef const DYLDINTERPOSE *PCDYLDINTERPOSE;
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82 |
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83 | /** @sa dyld_dynamic_interpose(). */
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84 | typedef const mach_header *FNDYLDDYNAMICINTERPOSE(const struct mach_header *mh, PCDYLDINTERPOSE paSym, size_t cSyms);
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85 | /** Pointer to dyld_dynamic_interpose. */
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86 | typedef FNDYLDDYNAMICINTERPOSE *PFNDYLDDYNAMICINTERPOSE;
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87 |
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88 | /** @sa dlopen(). */
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89 | typedef void *FNDLOPEN(const char *path, int mode);
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90 | /** Pointer to dlopen. */
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91 | typedef FNDLOPEN *PFNDLOPEN;
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92 |
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93 |
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94 | /*********************************************************************************************************************************
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95 | * Internal Functions *
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96 | *********************************************************************************************************************************/
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97 | extern "C" void _dyld_register_func_for_add_image(void (*func)(const struct mach_header *mh, intptr_t vmaddr_slide));
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98 |
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99 | static void *supR3HardenedDarwinDlopenInterpose(const char *path, int mode);
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100 | static int supR3HardenedDarwinIssetugidInterpose(void);
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101 |
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102 |
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103 | /*********************************************************************************************************************************
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104 | * Global Variables *
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105 | *********************************************************************************************************************************/
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106 | /** Flag whether macOS 11.x (BigSur) or later was detected.
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107 | * See comments in supR3HardenedDarwinDlopenInterpose for details. */
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108 | static bool g_fMacOs11Plus = false;
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109 | /** Resolved dyld_dynamic_interpose() value. */
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110 | static PFNDYLDDYNAMICINTERPOSE g_pfnDyldDynamicInterpose = NULL;
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111 | /** Pointer to the real dlopen() function used from the interposer when verification succeeded. */
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112 | static PFNDLOPEN g_pfnDlopenReal = NULL;
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113 | /**
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114 | * The interposer table.
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115 | */
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116 | static const DYLDINTERPOSE g_aInterposers[] =
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117 | {
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118 | { (const void *)(uintptr_t)&supR3HardenedDarwinDlopenInterpose, (const void *)(uintptr_t)&dlopen },
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119 | { (const void *)(uintptr_t)&supR3HardenedDarwinIssetugidInterpose, (const void *)(uintptr_t)&issetugid }
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120 | };
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121 |
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122 |
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123 | /**
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124 | * dlopen() interposer which verifies that the path to be loaded meets the criteria for hardened builds.
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125 | *
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126 | * @sa dlopen() man page.
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127 | */
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128 | static void *supR3HardenedDarwinDlopenInterpose(const char *path, int mode)
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129 | {
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130 | /*
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131 | * Giving NULL as the filename indicates opening the main program which is fine
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132 | * We are already loaded and executing after all.
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133 | *
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134 | * Filenames without any path component (whether absolute or relative) are allowed
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135 | * unconditionally too as the loader will only search the default paths configured by root.
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136 | */
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137 | if ( path
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138 | && strchr(path, '/') != NULL)
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139 | {
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140 | int rc = VINF_SUCCESS;
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141 |
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142 | /*
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143 | * Starting with macOS 11.0 (BigSur) system provided libraries
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144 | * under /System/Libraries are not stored on the filesystem anymore
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145 | * but in a dynamic linker cache. The integrity of the linker cache
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146 | * is maintained by the system and dyld. Our verification code fails because
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147 | * it can't find the file.
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148 | * The obvious solution is to exclude paths starting with /System/Libraries
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149 | * when we run on BigSur. Other paths are still subject to verification.
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150 | */
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151 | if ( !g_fMacOs11Plus
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152 | || strncmp(path, RT_STR_TUPLE("/System/Library")))
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153 | rc = supR3HardenedVerifyFileFollowSymlinks(path, RTHCUINTPTR_MAX, true /* fMaybe3rdParty */,
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154 | NULL /* pErrInfo */);
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155 | if (RT_FAILURE(rc))
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156 | return NULL;
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157 | }
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158 |
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159 | return g_pfnDlopenReal(path, mode);
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160 | }
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161 |
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162 |
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163 | /**
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164 | * Override this one to try hide the fact that we're setuid to root orginially.
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165 | *
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166 | * @sa issetugid() man page.
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167 | *
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168 | * Mac OS X: Really ugly hack to bypass a set-uid check in AppKit.
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169 | *
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170 | * This will modify the issetugid() function to always return zero. This must
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171 | * be done _before_ AppKit is initialized, otherwise it will refuse to play ball
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172 | * with us as it distrusts set-uid processes since Snow Leopard. We, however,
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173 | * have carefully dropped all root privileges at this point and there should be
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174 | * no reason for any security concern here.
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175 | */
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176 | static int supR3HardenedDarwinIssetugidInterpose(void)
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177 | {
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178 | #ifdef DEBUG
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179 | Dl_info Info = {0};
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180 | char szMsg[512];
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181 | size_t cchMsg;
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182 | const void * uCaller = __builtin_return_address(0);
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183 | if (dladdr(uCaller, &Info))
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184 | cchMsg = snprintf(szMsg, sizeof(szMsg), "DEBUG: issetugid_for_AppKit was called by %p %s::%s+%p (via %p)\n",
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185 | uCaller, Info.dli_fname, Info.dli_sname, (void *)((uintptr_t)uCaller - (uintptr_t)Info.dli_saddr), __builtin_return_address(1));
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186 | else
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187 | cchMsg = snprintf(szMsg, sizeof(szMsg), "DEBUG: issetugid_for_AppKit was called by %p (via %p)\n", uCaller, __builtin_return_address(1));
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188 | write(2, szMsg, cchMsg);
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189 | #endif
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190 | return 0;
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191 | }
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192 |
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193 |
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194 | /**
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195 | * Callback to get notified of new images being loaded to be able to apply our dlopn() interposer.
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196 | *
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197 | * @param mh Pointer to the mach header of the loaded image.
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198 | * @param vmaddr_slide The slide value for ASLR.
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199 | */
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200 | static DECLCALLBACK(void) supR3HardenedDarwinAddImage(const struct mach_header *mh, intptr_t vmaddr_slide)
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201 | {
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202 | RT_NOREF(vmaddr_slide);
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203 |
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204 | g_pfnDyldDynamicInterpose(mh, &g_aInterposers[0], RT_ELEMENTS(g_aInterposers));
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205 | }
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206 |
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207 |
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208 | /**
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209 | * Hardening initialization for macOS hosts.
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210 | *
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211 | * @note Doesn't return on error.
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212 | */
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213 | DECLHIDDEN(void) supR3HardenedDarwinInit(void)
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214 | {
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215 | /*
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216 | * Check whether we are running on macOS BigSur by checking kern.osproductversion
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217 | * available since some point in 2018.
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218 | */
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219 | char szVers[256]; RT_ZERO(szVers);
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220 | size_t cbVers = sizeof(szVers);
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221 | int rc = sysctlbyname("kern.osproductversion", &szVers[0], &cbVers, NULL, 0);
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222 | if ( !rc
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223 | && memcmp(&szVers[0], RT_STR_TUPLE("10.16")) >= 0)
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224 | g_fMacOs11Plus = true;
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225 |
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226 | /* Saved to call real dlopen() later on, as we will interpose dlopen() from the main binary in the next step as well. */
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227 | g_pfnDlopenReal = (PFNDLOPEN)dlsym(RTLD_DEFAULT, "dlopen");
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228 | g_pfnDyldDynamicInterpose = (PFNDYLDDYNAMICINTERPOSE)dlsym(RTLD_DEFAULT, "dyld_dynamic_interpose");
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229 | if (!g_pfnDyldDynamicInterpose)
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230 | supR3HardenedFatalMsg("supR3HardenedDarwinInit", kSupInitOp_Integrity, VERR_SYMBOL_NOT_FOUND,
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231 | "Failed to find dyld_dynamic_interpose()");
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232 |
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233 | /*
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234 | * The following will causes our add image notification to be called for all images loaded so far.
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235 | * The callback will set up the interposer.
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236 | */
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237 | _dyld_register_func_for_add_image(supR3HardenedDarwinAddImage);
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238 | }
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239 |
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240 |
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241 |
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242 | /*
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243 | * assert.cpp
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244 | *
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245 | * ASSUMES working DECLHIDDEN or there will be symbol confusion!
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246 | */
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247 |
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248 | RTDATADECL(char) g_szRTAssertMsg1[1024];
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249 | RTDATADECL(char) g_szRTAssertMsg2[4096];
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250 | RTDATADECL(const char * volatile) g_pszRTAssertExpr;
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251 | RTDATADECL(const char * volatile) g_pszRTAssertFile;
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252 | RTDATADECL(uint32_t volatile) g_u32RTAssertLine;
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253 | RTDATADECL(const char * volatile) g_pszRTAssertFunction;
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254 |
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255 | RTDECL(bool) RTAssertMayPanic(void)
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256 | {
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257 | return true;
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258 | }
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259 |
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260 |
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261 | RTDECL(void) RTAssertMsg1(const char *pszExpr, unsigned uLine, const char *pszFile, const char *pszFunction)
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262 | {
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263 | /*
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264 | * Fill in the globals.
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265 | */
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266 | g_pszRTAssertExpr = pszExpr;
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267 | g_pszRTAssertFile = pszFile;
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268 | g_pszRTAssertFunction = pszFunction;
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269 | g_u32RTAssertLine = uLine;
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270 | snprintf(g_szRTAssertMsg1, sizeof(g_szRTAssertMsg1),
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271 | "\n!!Assertion Failed!!\n"
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272 | "Expression: %s\n"
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273 | "Location : %s(%u) %s\n",
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274 | pszExpr, pszFile, uLine, pszFunction);
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275 | }
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276 |
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277 |
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278 | RTDECL(void) RTAssertMsg2V(const char *pszFormat, va_list va)
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279 | {
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280 | vsnprintf(g_szRTAssertMsg2, sizeof(g_szRTAssertMsg2), pszFormat, va);
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281 | if (g_enmSupR3HardenedMainState < SUPR3HARDENEDMAINSTATE_CALLED_TRUSTED_MAIN)
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282 | supR3HardenedFatalMsg(g_pszRTAssertExpr, kSupInitOp_Misc, VERR_INTERNAL_ERROR,
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283 | "%s%s", g_szRTAssertMsg1, g_szRTAssertMsg2);
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284 | else
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285 | supR3HardenedError(VERR_INTERNAL_ERROR, false/*fFatal*/, "%s%s", g_szRTAssertMsg1, g_szRTAssertMsg2);
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286 | }
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287 |
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