| 1 | /* $Id: SUPR3HardenedMain-darwin.cpp 87031 2020-12-02 11:57:03Z 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) 2017-2020 Oracle Corporation
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| 8 | *
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| 9 | * This file is part of VirtualBox Open Source Edition (OSE), as
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| 10 | * available from http://www.virtualbox.org. This file is free software;
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| 11 | * you can redistribute it and/or modify it under the terms of the GNU
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| 12 | * General Public License (GPL) as published by the Free Software
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| 13 | * Foundation, in version 2 as it comes in the "COPYING" file of the
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| 14 | * VirtualBox OSE distribution. VirtualBox OSE is distributed in the
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| 15 | * hope that it will be useful, but WITHOUT ANY WARRANTY of any kind.
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| 16 | *
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| 17 | * The contents of this file may alternatively be used under the terms
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| 18 | * of the Common Development and Distribution License Version 1.0
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| 19 | * (CDDL) only, as it comes in the "COPYING.CDDL" file of the
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| 20 | * VirtualBox OSE distribution, in which case the provisions of the
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| 21 | * CDDL are applicable instead of those of the GPL.
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| 22 | *
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| 23 | * You may elect to license modified versions of this file under the
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| 24 | * terms and conditions of either the GPL or the CDDL or both.
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| 25 | */
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| 26 |
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| 27 |
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| 28 | /*********************************************************************************************************************************
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| 29 | * Header Files *
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| 30 | *********************************************************************************************************************************/
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| 31 | #include <VBox/err.h>
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| 32 | #include <VBox/sup.h>
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| 33 |
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| 34 | #include <iprt/path.h>
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| 35 | #include <iprt/string.h>
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| 36 |
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| 37 | #include <dlfcn.h>
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| 38 | #include <sys/mman.h>
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| 39 | #include <errno.h>
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| 40 | #include <sys/sysctl.h> /* sysctlbyname() */
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| 41 | #include <stdio.h>
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| 42 | #include <stdint.h>
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| 43 | #include <unistd.h> /* issetugid() */
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| 44 | #include <mach-o/dyld.h>
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| 45 |
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| 46 | #include "SUPLibInternal.h"
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| 47 |
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| 48 |
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| 49 | /*********************************************************************************************************************************
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| 50 | * Defined Constants And Macros *
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| 51 | *********************************************************************************************************************************/
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| 52 |
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| 53 |
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| 54 | /*********************************************************************************************************************************
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| 55 | * Structures and Typedefs *
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| 56 | *********************************************************************************************************************************/
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| 57 |
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| 58 | /**
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| 59 | * Interpose table entry.
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| 60 | */
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| 61 | typedef struct DYLDINTERPOSE
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| 62 | {
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| 63 | /** The symbol address to replace with. */
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| 64 | const void *pvReplacement;
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| 65 | /** The replaced symbol address. */
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| 66 | const void *pvReplacee;
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| 67 | } DYLDINTERPOSE;
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| 68 | /** Pointer to an interposer table entry. */
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| 69 | typedef DYLDINTERPOSE *PDYLDINTERPOSE;
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| 70 | /** Pointer to a const interposer table entry. */
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| 71 | typedef const DYLDINTERPOSE *PCDYLDINTERPOSE;
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| 72 |
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| 73 | /** @sa dyld_dynamic_interpose(). */
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| 74 | typedef const mach_header * FNDYLDDYNAMICINTERPOSE(const struct mach_header* mh, PCDYLDINTERPOSE paSym, size_t cSyms);
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| 75 | typedef FNDYLDDYNAMICINTERPOSE *PFNDYLDDYNAMICINTERPOSE;
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| 76 |
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| 77 | /** @sa dlopen(). */
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| 78 | typedef void *FNDLOPEN(const char *path, int mode);
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| 79 | typedef FNDLOPEN *PFNDLOPEN;
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| 80 |
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| 81 |
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| 82 | /*********************************************************************************************************************************
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| 83 | * Internal Functions *
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| 84 | *********************************************************************************************************************************/
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| 85 |
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| 86 | extern "C" void _dyld_register_func_for_add_image(void (*func)(const struct mach_header* mh, intptr_t vmaddr_slide));
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| 87 |
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| 88 | static void * supR3HardenedDarwinDlopenInterpose(const char *path, int mode);
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| 89 | static int supR3HardenedDarwinIssetugidInterpose(void);
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| 90 |
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| 91 |
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| 92 | /*********************************************************************************************************************************
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| 93 | * Global Variables *
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| 94 | *********************************************************************************************************************************/
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| 95 | /** Flag whether macOS 11.x (BigSur) was detected. */
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| 96 | static bool g_fMacOs11 = false;
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| 97 | /** Resolved dyld_dynamic_interpose() value. */
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| 98 | static PFNDYLDDYNAMICINTERPOSE g_pfnDyldDynamicInterpose = NULL;
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| 99 | /** Pointer to the real dlopen() function used from the interposer when verification succeeded. */
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| 100 | static PFNDLOPEN g_pfnDlopenReal = NULL;
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| 101 | /**
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| 102 | * The interposer table.
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| 103 | */
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| 104 | static const DYLDINTERPOSE g_aInterposers[] =
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| 105 | {
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| 106 | { (const void *)(uintptr_t)&supR3HardenedDarwinDlopenInterpose, (const void *)(uintptr_t)&dlopen },
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| 107 | { (const void *)(uintptr_t)&supR3HardenedDarwinIssetugidInterpose, (const void *)(uintptr_t)&issetugid }
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| 108 | };
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| 109 |
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| 110 |
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| 111 | /**
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| 112 | * dlopen() interposer which verifies that the path to be loaded meets the criteria for hardened builds.
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| 113 | *
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| 114 | * @sa dlopen() man page.
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| 115 | */
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| 116 | static void * supR3HardenedDarwinDlopenInterpose(const char *path, int mode)
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| 117 | {
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| 118 | /*
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| 119 | * Giving NULL as the filename indicates opening the main program which is fine
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| 120 | * We are already loaded and executing after all.
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| 121 | *
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| 122 | * Filenames without any path component (whether absolute or relative) are allowed
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| 123 | * unconditionally too as the loader will only search the default paths configured by root.
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| 124 | */
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| 125 | if ( path
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| 126 | && strchr(path, '/') != NULL)
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| 127 | {
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| 128 | int rc = VINF_SUCCESS;
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| 129 |
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| 130 | /*
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| 131 | * Starting with macOS 11.0 (BigSur) system provided libraries
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| 132 | * under /System/Libraries are not stored on the filesystem anymore
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| 133 | * but in a dynamic linker cache. The integrity of the linker cache
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| 134 | * is maintained by the system and dyld. Our verification code fails because
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| 135 | * it can't find the file.
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| 136 | * The obvious solution is to exclude paths starting with /System/Libraries
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| 137 | * when we run on BigSur. Other paths are still subject to verification.
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| 138 | */
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| 139 | if ( !g_fMacOs11
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| 140 | || strncmp(path, RT_STR_TUPLE("/System/Library")))
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| 141 | rc = supR3HardenedVerifyFileFollowSymlinks(path, RTHCUINTPTR_MAX, true /* fMaybe3rdParty */,
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| 142 | NULL /* pErrInfo */);
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| 143 | if (RT_FAILURE(rc))
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| 144 | return NULL;
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| 145 | }
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| 146 |
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| 147 | return g_pfnDlopenReal(path, mode);
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| 148 | }
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| 149 |
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| 150 |
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| 151 | /**
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| 152 | * Override this one to try hide the fact that we're setuid to root orginially.
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| 153 | *
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| 154 | * @sa issetugid() man page.
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| 155 | *
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| 156 | * Mac OS X: Really ugly hack to bypass a set-uid check in AppKit.
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| 157 | *
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| 158 | * This will modify the issetugid() function to always return zero. This must
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| 159 | * be done _before_ AppKit is initialized, otherwise it will refuse to play ball
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| 160 | * with us as it distrusts set-uid processes since Snow Leopard. We, however,
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| 161 | * have carefully dropped all root privileges at this point and there should be
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| 162 | * no reason for any security concern here.
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| 163 | */
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| 164 | static int supR3HardenedDarwinIssetugidInterpose(void)
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| 165 | {
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| 166 | Dl_info Info = {0};
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| 167 | char szMsg[512];
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| 168 | size_t cchMsg;
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| 169 | const void * uCaller = __builtin_return_address(0);
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| 170 | if (dladdr(uCaller, &Info))
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| 171 | cchMsg = snprintf(szMsg, sizeof(szMsg), "DEBUG: issetugid_for_AppKit was called by %p %s::%s+%p (via %p)\n",
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| 172 | uCaller, Info.dli_fname, Info.dli_sname, (void *)((uintptr_t)uCaller - (uintptr_t)Info.dli_saddr), __builtin_return_address(1));
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| 173 | else
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| 174 | 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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| 175 | write(2, szMsg, cchMsg);
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| 176 | return 0;
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| 177 | }
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| 178 |
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| 179 |
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| 180 | /**
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| 181 | * Callback to get notified of new images being loaded to be able to apply our dlopn() interposer.
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| 182 | *
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| 183 | * @returns nothing.
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| 184 | * @param mh Pointer to the mach header of the loaded image.
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| 185 | * @param vmaddr_slide The slide value for ASLR.
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| 186 | */
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| 187 | static DECLCALLBACK(void) supR3HardenedDarwinAddImage(const struct mach_header* mh, intptr_t vmaddr_slide)
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| 188 | {
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| 189 | RT_NOREF(vmaddr_slide);
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| 190 |
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| 191 | g_pfnDyldDynamicInterpose((const struct mach_header*)mh, &g_aInterposers[0], RT_ELEMENTS(g_aInterposers));
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| 192 | }
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| 193 |
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| 194 |
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| 195 | /**
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| 196 | * Hardening initialization for macOS hosts.
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| 197 | *
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| 198 | * @returns nothing.
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| 199 | *
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| 200 | * @note Doesn't return on error.
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| 201 | */
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| 202 | DECLHIDDEN(void) supR3HardenedDarwinInit(void)
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| 203 | {
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| 204 | /*
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| 205 | * Check whether we are running on macOS BigSur by checking kern.osproductversion
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| 206 | * available since some point in 2018.
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| 207 | */
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| 208 | char szVers[256]; RT_ZERO(szVers);
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| 209 | size_t cbVers = sizeof(szVers);
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| 210 | int rc = sysctlbyname("kern.osproductversion", &szVers[0], &cbVers, NULL, 0);
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| 211 | if ( !rc
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| 212 | && !memcmp(&szVers[0], RT_STR_TUPLE("10.16")))
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| 213 | g_fMacOs11 = true;
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| 214 |
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| 215 | /* 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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| 216 | g_pfnDlopenReal = (PFNDLOPEN)dlsym(RTLD_DEFAULT, "dlopen");
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| 217 | g_pfnDyldDynamicInterpose = (PFNDYLDDYNAMICINTERPOSE)dlsym(RTLD_DEFAULT, "dyld_dynamic_interpose");
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| 218 | if (!g_pfnDyldDynamicInterpose)
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| 219 | supR3HardenedFatalMsg("supR3HardenedDarwinInit", kSupInitOp_Integrity, VERR_SYMBOL_NOT_FOUND,
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| 220 | "Failed to find dyld_dynamic_interpose()");
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| 221 |
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| 222 | /*
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| 223 | * The following will causes our add image notification to be called for all images loaded so far.
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| 224 | * The callback will set up the interposer.
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| 225 | */
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| 226 | _dyld_register_func_for_add_image(supR3HardenedDarwinAddImage);
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| 227 | }
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| 228 |
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| 229 |
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| 230 |
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| 231 | /*
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| 232 | * assert.cpp
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| 233 | *
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| 234 | * ASSUMES working DECLHIDDEN or there will be symbol confusion!
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| 235 | */
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| 236 |
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| 237 | RTDATADECL(char) g_szRTAssertMsg1[1024];
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| 238 | RTDATADECL(char) g_szRTAssertMsg2[4096];
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| 239 | RTDATADECL(const char * volatile) g_pszRTAssertExpr;
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| 240 | RTDATADECL(const char * volatile) g_pszRTAssertFile;
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| 241 | RTDATADECL(uint32_t volatile) g_u32RTAssertLine;
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| 242 | RTDATADECL(const char * volatile) g_pszRTAssertFunction;
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| 243 |
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| 244 | RTDECL(bool) RTAssertMayPanic(void)
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| 245 | {
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| 246 | return true;
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| 247 | }
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| 248 |
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| 249 |
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| 250 | RTDECL(void) RTAssertMsg1(const char *pszExpr, unsigned uLine, const char *pszFile, const char *pszFunction)
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| 251 | {
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| 252 | /*
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| 253 | * Fill in the globals.
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| 254 | */
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| 255 | g_pszRTAssertExpr = pszExpr;
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| 256 | g_pszRTAssertFile = pszFile;
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| 257 | g_pszRTAssertFunction = pszFunction;
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| 258 | g_u32RTAssertLine = uLine;
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| 259 | snprintf(g_szRTAssertMsg1, sizeof(g_szRTAssertMsg1),
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| 260 | "\n!!Assertion Failed!!\n"
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| 261 | "Expression: %s\n"
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| 262 | "Location : %s(%u) %s\n",
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| 263 | pszExpr, pszFile, uLine, pszFunction);
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| 264 | }
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| 265 |
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| 266 |
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| 267 | RTDECL(void) RTAssertMsg2V(const char *pszFormat, va_list va)
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| 268 | {
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| 269 | vsnprintf(g_szRTAssertMsg2, sizeof(g_szRTAssertMsg2), pszFormat, va);
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| 270 | if (g_enmSupR3HardenedMainState < SUPR3HARDENEDMAINSTATE_CALLED_TRUSTED_MAIN)
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| 271 | supR3HardenedFatalMsg(g_pszRTAssertExpr, kSupInitOp_Misc, VERR_INTERNAL_ERROR,
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| 272 | "%s%s", g_szRTAssertMsg1, g_szRTAssertMsg2);
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| 273 | else
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| 274 | supR3HardenedError(VERR_INTERNAL_ERROR, false/*fFatal*/, "%s%s", g_szRTAssertMsg1, g_szRTAssertMsg2);
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| 275 | }
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| 276 |
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