qmachparser.cpp - mozsearch

++ // Copyright (C) 2016 Intel Corporation.

++ // SPDX-License-Identifier: LicenseRef-Qt-Commercial OR LGPL-3.0-only OR GPL-2.0-only OR GPL-3.0-only

++ // Qt-Security score:critical reason:data-parser

++

++ #include "qmachparser_p.h"

++

++ #include <qendian.h>

++

++ #include <optional>

++

++ #include <mach-o/loader.h>

++ #include <mach-o/fat.h>

++

++ QT_BEGIN_NAMESPACE

++

++ using namespace Qt::StringLiterals;

++

++ // Whether we include some extra validity checks

++ // (checks to ensure we don't read out-of-bounds are always included)

++ static constexpr bool IncludeValidityChecks = true;

++

++ #if defined(Q_PROCESSOR_X86_64)

++ #  define MACHO64

++ static const cpu_type_t my_cputype = CPU_TYPE_X86_64;

++ #elif defined(Q_PROCESSOR_X86_32)

++ static const cpu_type_t my_cputype = CPU_TYPE_X86;

++ #elif defined(Q_PROCESSOR_POWER_64)

++ #  define MACHO64

++ static const cpu_type_t my_cputype = CPU_TYPE_POWERPC64;

++ #elif defined(Q_PROCESSOR_POWER_32)

++ static const cpu_type_t my_cputype = CPU_TYPE_POWERPC;

++ #elif defined(Q_PROCESSOR_ARM_64)

++ #  define MACHO64

++ static const cpu_type_t my_cputype = CPU_TYPE_ARM64;

++ #elif defined(Q_PROCESSOR_ARM)

++ static const cpu_type_t my_cputype = CPU_TYPE_ARM;

++ #else

++ #  error "Unknown CPU type"

++ #endif

++

++ #ifdef MACHO64

++ #  undef MACHO64

++ typedef mach_header_64 my_mach_header;

++ typedef segment_command_64 my_segment_command;

++ typedef section_64 my_section;

++ static const uint32_t my_magic = MH_MAGIC_64;

++ #else

++ typedef mach_header my_mach_header;

++ typedef segment_command my_segment_command;

++ typedef section my_section;

++ static const uint32_t my_magic = MH_MAGIC;

++ #endif

++

++ Q_DECL_COLD_FUNCTION

++ static QLibraryScanResult notfound(const QString &reason, QString *errorString)

++ {

++     *errorString = QLibrary::tr("'%1' is not a valid Mach-O binary (%2)")

++             .arg(*errorString, reason.isEmpty() ? QLibrary::tr("file is corrupt") : reason);

++     return {};

++ }

++

++ // Returns whether the binary is encrypted, or nullopt if the load-command table

++ // is malformed or extends past the end of the (mmapped) file.

++ static std::optional<bool> isEncrypted(const my_mach_header *header, ulong fdlen)

++ {

++     auto commandCursor = uintptr_t(header) + sizeof(my_mach_header);

++     // QMachOParser::parse() verifies that fdlen is large enough for at least

++     // my_mach_header + load_command.

++     ulong minsize = sizeof(my_mach_header);

++

++     for (uint32_t i = 0; i < header->ncmds; ++i) {

++         // We must be able to read the load command header (cmd + cmdsize).

++         if (Q_UNLIKELY(fdlen - sizeof(load_command) < minsize))

++             return std::nullopt;

++

++         load_command *loadCommand = reinterpret_cast<load_command *>(commandCursor);

++         const uint32_t cmdsize = loadCommand->cmdsize;

++

++         // A load command must at least contain its own header

++         if (Q_UNLIKELY(cmdsize < sizeof(load_command)))

++             return std::nullopt;

++

++         // cmdsize can't be trusted until validated against fdlen

++         if (qAddOverflow(minsize, ulong(cmdsize), &minsize) || Q_UNLIKELY(minsize > fdlen))

++             return std::nullopt;

++

++         if (loadCommand->cmd == LC_ENCRYPTION_INFO || loadCommand->cmd == LC_ENCRYPTION_INFO_64) {

++             // The layout of encryption_info_command and encryption_info_command_64 is the same

++             // up until and including cryptid, so we can treat it as encryption_info_command.

++             // Make sure the command is big enough to hold the field we read.

++             if (Q_UNLIKELY(cmdsize < sizeof(encryption_info_command)))

++                 return std::nullopt;

++             auto encryptionInfoCommand = reinterpret_cast<encryption_info_command*>(loadCommand);

++             return encryptionInfoCommand->cryptid != 0;

++         }

++

++         commandCursor += cmdsize;

++     }

++

++     return false;

++ }

++

++ QLibraryScanResult  QMachOParser::parse(const char *m_s, ulong fdlen, QString *errorString)

++ {

++     // The minimum size of a Mach-O binary we're interested in.

++     // It must have a full Mach header, at least one segment and at least one

++     // section. It's probably useless with just the "qtmetadata" section, but

++     // it's valid nonetheless.

++     // A fat binary must have this plus the fat header, of course.

++     static const size_t MinFileSize = sizeof(my_mach_header) + sizeof(my_segment_command) + sizeof(my_section);

++     static const size_t MinFatHeaderSize = sizeof(fat_header) + 2 * sizeof(fat_arch);

++

++     if (Q_UNLIKELY(fdlen < MinFileSize))

++         return notfound(QLibrary::tr("file too small"), errorString);

++

++     // find out if this is a fat Mach-O binary first

++     const my_mach_header *header = nullptr;

++     const fat_header *fat = reinterpret_cast<const fat_header *>(m_s);

++     if (fat->magic == qToBigEndian(FAT_MAGIC)) {

++         // find our architecture in the binary

++         const fat_arch *arch = reinterpret_cast<const fat_arch *>(fat + 1);

++         if (Q_UNLIKELY(fdlen < MinFatHeaderSize)) {

++             return notfound(QLibrary::tr("file too small"), errorString);

++         }

++

++         int count = qFromBigEndian(fat->nfat_arch);

++         if (Q_UNLIKELY(fdlen < sizeof(*fat) + sizeof(*arch) * count))

++             return notfound(QString(), errorString);

++

++         for (int i = 0; i < count; ++i) {

++             if (arch[i].cputype == qToBigEndian(my_cputype)) {

++                 // ### should we check the CPU subtype? Maybe on ARM?

++                 uint32_t size = qFromBigEndian(arch[i].size);

++                 uint32_t offset = qFromBigEndian(arch[i].offset);

++                 if (Q_UNLIKELY(size > fdlen) || Q_UNLIKELY(offset > fdlen)

++                         || Q_UNLIKELY(size + offset > fdlen) || Q_UNLIKELY(size < MinFileSize))

++                     return notfound(QString(), errorString);

++

++                 header = reinterpret_cast<const my_mach_header *>(m_s + offset);

++                 fdlen = size;

++                 break;

++             }

++         }

++         if (!header)

++             return notfound(QLibrary::tr("no suitable architecture in fat binary"), errorString);

++

++         // check the magic again

++         if (Q_UNLIKELY(header->magic != my_magic))

++             return notfound(QString(), errorString);

++     } else {

++         header = reinterpret_cast<const my_mach_header *>(m_s);

++         fat = 0;

++

++         // check magic

++         if (header->magic != my_magic)

++             return notfound(QLibrary::tr("invalid magic %1").arg(qFromBigEndian(header->magic),

++                                                                  8, 16, '0'_L1),

++                       errorString);

++     }

++

++     // from this point on, everything is in host byte order

++

++     // (re-)check the CPU type

++     // ### should we check the CPU subtype? Maybe on ARM?

++     if (header->cputype != my_cputype) {

++         if (fat)

++             return notfound(QString(), errorString);

++         return notfound(QLibrary::tr("wrong architecture"), errorString);

++     }

++

++     // check the file type

++     if (Q_UNLIKELY(header->filetype != MH_BUNDLE && header->filetype != MH_DYLIB))

++         return notfound(QLibrary::tr("not a dynamic library"), errorString);

++

++     // find the __TEXT segment, "qtmetadata" section

++     const my_segment_command *seg = reinterpret_cast<const my_segment_command *>(header + 1);

++     ulong minsize = sizeof(*header);

++

++     for (uint i = 0; i < header->ncmds; ++i,

++          seg = reinterpret_cast<const my_segment_command *>(reinterpret_cast<const char *>(seg) + seg->cmdsize)) {

++         // We're sure that the file size includes at least one load command

++         // but we have to check anyway if we're past the first

++         if (Q_UNLIKELY(fdlen < minsize + sizeof(load_command)))

++             return notfound(QString(), errorString);

++

++         // cmdsize can't be trusted until validated

++         // so check it against fdlen anyway

++         // (these are unsigned operations, with overflow behavior specified in the standard)

++         minsize += seg->cmdsize;

++         if (Q_UNLIKELY(fdlen < minsize) || Q_UNLIKELY(fdlen < seg->cmdsize))

++             return notfound(QString(), errorString);

++

++         const uint32_t MyLoadCommand = sizeof(void *) > 4 ? LC_SEGMENT_64 : LC_SEGMENT;

++         if (seg->cmd != MyLoadCommand)

++             continue;

++

++         // is this the __TEXT segment?

++         if (strcmp(seg->segname, "__TEXT") == 0) {

++             const my_section *sect = reinterpret_cast<const my_section *>(seg + 1);

++             for (uint j = 0; j < seg->nsects; ++j) {

++                 // is this the "qtmetadata" section?

++                 if (strcmp(sect[j].sectname, "qtmetadata") != 0)

++                     continue;

++

++                 // found it!

++                 if (Q_UNLIKELY(fdlen < sect[j].offset) || Q_UNLIKELY(fdlen < sect[j].size)

++                         || Q_UNLIKELY(fdlen < sect[j].offset + sect[j].size))

++                     return notfound(QString(), errorString);

++

++                 if (sect[j].size < sizeof(QPluginMetaData::MagicHeader))

++                     return notfound(QLibrary::tr(".qtmetadata section is too small"), errorString);

++

++                 const std::optional<bool> binaryIsEncrypted = isEncrypted(header, fdlen);

++                 if (Q_UNLIKELY(!binaryIsEncrypted))

++                     return notfound(QLibrary::tr("corrupted encryption_info section"), errorString);

++                 qsizetype pos = reinterpret_cast<const char *>(header) - m_s + sect[j].offset;

++

++                 // We can not read the section data of encrypted libraries until they

++                 // have been dlopened(), so skip validity check if that's the case.

++                 if (IncludeValidityChecks && !*binaryIsEncrypted) {

++                     QByteArrayView expectedMagic = QByteArrayView::fromArray(QPluginMetaData::MagicString);

++                     QByteArrayView actualMagic = QByteArrayView(m_s + pos, expectedMagic.size());

++                     if (expectedMagic != actualMagic)

++                         return notfound(QLibrary::tr(".qtmetadata section has incorrect magic"), errorString);

++                 }

++

++                 pos += sizeof(QPluginMetaData::MagicString);

++                 return { pos, qsizetype(sect[j].size - sizeof(QPluginMetaData::MagicString)), *binaryIsEncrypted };

++             }

++         }

++

++         // other type of segment

++         seg = reinterpret_cast<const my_segment_command *>(reinterpret_cast<const char *>(seg) + seg->cmdsize);

++     }

++

++     // No .qtmetadata section was found

++     *errorString = QLibrary::tr("'%1' is not a Qt plugin").arg(*errorString);

++     return {};

++ }

++

++ QT_END_NAMESPACE

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