[apple/security.git] / libsecurity_utilities / lib / macho++.cpp

/*
 * Copyright (c) 2006-2013 Apple Computer, Inc. All Rights Reserved.
 * 
 * @APPLE_LICENSE_HEADER_START@
 * 
 * This file contains Original Code and/or Modifications of Original Code
 * as defined in and that are subject to the Apple Public Source License
 * Version 2.0 (the 'License'). You may not use this file except in
 * compliance with the License. Please obtain a copy of the License at
 * http://www.opensource.apple.com/apsl/ and read it before using this
 * file.
 * 
 * The Original Code and all software distributed under the License are
 * distributed on an 'AS IS' basis, WITHOUT WARRANTY OF ANY KIND, EITHER
 * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
 * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE, QUIET ENJOYMENT OR NON-INFRINGEMENT.
 * Please see the License for the specific language governing rights and
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 */

//
// macho++ - Mach-O object file helpers
//
#include "macho++.h"
#include <security_utilities/memutils.h>
#include <security_utilities/endian.h>
#include <mach-o/dyld.h>

namespace Security {


//
// Architecture values
//
Architecture::Architecture(const fat_arch &arch)
        : pair<cpu_type_t, cpu_subtype_t>(arch.cputype, arch.cpusubtype)
{
}

Architecture::Architecture(const char *name)
{
        if (const NXArchInfo *nxa = NXGetArchInfoFromName(name)) {
                this->first = nxa->cputype;
                this->second = nxa->cpusubtype;
        } else {
                this->first = this->second = none;
        }
}


//
// The local architecture.
//
// We take this from ourselves - the architecture of our main program Mach-O binary.
// There's the NXGetLocalArchInfo API, but it insists on saying "i386" on modern
// x86_64-centric systems, and lies to ppc (Rosetta) programs claiming they're native ppc.
// So let's not use that.
//
Architecture Architecture::local()
{
        return MainMachOImage().architecture();
}


//
// Translate between names and numbers
//
const char *Architecture::name() const
{
        if (const NXArchInfo *info = NXGetArchInfoFromCpuType(cpuType(), cpuSubtype()))
                return info->name;
        else
                return NULL;
}

std::string Architecture::displayName() const
{
        if (const char *s = this->name())
                return s;
        char buf[20];
        snprintf(buf, sizeof(buf), "(%d:%d)", cpuType(), cpuSubtype());
        return buf;
}
        

//
// Compare architectures.
// This is asymmetrical; the second argument provides for some templating.
//
bool Architecture::matches(const Architecture &templ) const
{
        if (first != templ.first)
                return false;   // main architecture mismatch
        if (templ.second == CPU_SUBTYPE_MULTIPLE)
                return true;    // subtype wildcard
        // match subtypes, ignoring feature bits
        return ((second ^ templ.second) & ~CPU_SUBTYPE_MASK) == 0;
}


//
// MachOBase contains knowledge of the Mach-O object file format,
// but abstracts from any particular sourcing. It must be subclassed,
// and the subclass must provide the file header and commands area
// during its construction. Memory is owned by the subclass.
//
MachOBase::~MachOBase()
{ /* virtual */ }

// provide the Mach-O file header, somehow
void MachOBase::initHeader(const mach_header *header)
{
        mHeader = header;
        switch (mHeader->magic) {
        case MH_MAGIC:
                mFlip = false;
                m64 = false;
                break;
        case MH_CIGAM:
                mFlip = true;
                m64 = false;
                break;
        case MH_MAGIC_64:
                mFlip = false;
                m64 = true;
                break;
        case MH_CIGAM_64:
                mFlip = true;
                m64 = true;
                break;
        default:
                UnixError::throwMe(ENOEXEC);
        }
}

// provide the Mach-O commands section, somehow
void MachOBase::initCommands(const load_command *commands)
{
        mCommands = commands;
        mEndCommands = LowLevelMemoryUtilities::increment<load_command>(commands, flip(mHeader->sizeofcmds));
        if (mCommands + 1 > mEndCommands)       // ensure initial load command core available
                UnixError::throwMe(ENOEXEC);
}


size_t MachOBase::headerSize() const
{
        return m64 ? sizeof(mach_header_64) : sizeof(mach_header);
}

size_t MachOBase::commandSize() const
{
        return flip(mHeader->sizeofcmds);
}


//
// Create a MachO object from an open file and a starting offset.
// We load (only) the header and load commands into memory at that time.
// Note that the offset must be relative to the start of the containing file
// (not relative to some intermediate container).
//
MachO::MachO(FileDesc fd, size_t offset, size_t length)
        : FileDesc(fd), mOffset(offset), mLength(length ? length : (fd.fileSize() - offset))
{
        size_t size = fd.read(&mHeaderBuffer, sizeof(mHeaderBuffer), mOffset);
        if (size != sizeof(mHeaderBuffer))
                UnixError::throwMe(ENOEXEC);
        this->initHeader(&mHeaderBuffer);
        size_t cmdSize = this->commandSize();
        mCommandBuffer = (load_command *)malloc(cmdSize);
        if (!mCommandBuffer)
                UnixError::throwMe();
        if (fd.read(mCommandBuffer, cmdSize, this->headerSize() + mOffset) != cmdSize)
                UnixError::throwMe(ENOEXEC);
        this->initCommands(mCommandBuffer);
}

MachO::~MachO()
{
        ::free(mCommandBuffer);
}


//
// Create a MachO object that is (entirely) mapped into memory.
// The caller must ensire that the underlying mapping persists
// at least as long as our object.
//
MachOImage::MachOImage(const void *address)
{
        this->initHeader((const mach_header *)address);
        this->initCommands(LowLevelMemoryUtilities::increment<const load_command>(address, this->headerSize()));
}


//
// Locate the Mach-O image of the main program
//
MainMachOImage::MainMachOImage()
        : MachOImage(mainImageAddress())
{
}

const void *MainMachOImage::mainImageAddress()
{
        return _dyld_get_image_header(0);
}


//
// Return various header fields
//
Architecture MachOBase::architecture() const
{
        return Architecture(flip(mHeader->cputype), flip(mHeader->cpusubtype));
}

uint32_t MachOBase::type() const
{
        return flip(mHeader->filetype);
}

uint32_t MachOBase::flags() const
{
        return flip(mHeader->flags);
}


//
// Iterate through load commands
//
const load_command *MachOBase::nextCommand(const load_command *command) const
{
        using LowLevelMemoryUtilities::increment;
        command = increment<const load_command>(command, flip(command->cmdsize));
        if (command >= mEndCommands)    // end of load commands
                return NULL;
        if (increment(command, sizeof(load_command)) > mEndCommands
                || increment(command, flip(command->cmdsize)) > mEndCommands)
                UnixError::throwMe(ENOEXEC);
        return command;
}


//
// Find a specific load command, by command number.
// If there are multiples, returns the first one found.
//
const load_command *MachOBase::findCommand(uint32_t cmd) const
{
        for (const load_command *command = loadCommands(); command; command = nextCommand(command))
                if (flip(command->cmd) == cmd)
                        return command;
        return NULL;
}


//
// Locate a segment command, by name
//      
const segment_command *MachOBase::findSegment(const char *segname) const
{
        for (const load_command *command = loadCommands(); command; command = nextCommand(command)) {
                switch (flip(command->cmd)) {
                case LC_SEGMENT:
                case LC_SEGMENT_64:
                        {
                                const segment_command *seg = reinterpret_cast<const segment_command *>(command);
                                if (!strcmp(seg->segname, segname))
                                        return seg;
                                break;
                        }
                default:
                        break;
                }
        }
        return NULL;
}

const section *MachOBase::findSection(const char *segname, const char *sectname) const
{
        using LowLevelMemoryUtilities::increment;
        if (const segment_command *seg = findSegment(segname)) {
                if (is64()) {
                        const segment_command_64 *seg64 = reinterpret_cast<const segment_command_64 *>(seg);
                        const section_64 *sect = increment<const section_64>(seg64 + 1, 0);
                        for (unsigned n = flip(seg64->nsects); n > 0; n--, sect++) {
                                if (!strcmp(sect->sectname, sectname))
                                        return reinterpret_cast<const section *>(sect);
                        }
                } else {
                        const section *sect = increment<const section>(seg + 1, 0);
                        for (unsigned n = flip(seg->nsects); n > 0; n--, sect++) {
                                if (!strcmp(sect->sectname, sectname))
                                        return sect;
                        }
                }
        }
        return NULL;
}


//
// Translate a union lc_str into the string it denotes.
// Returns NULL (no exceptions) if the entry is corrupt.
//
const char *MachOBase::string(const load_command *cmd, const lc_str &str) const
{
        size_t offset = flip(str.offset);
        const char *sp = LowLevelMemoryUtilities::increment<const char>(cmd, offset);
        if (offset + strlen(sp) + 1 > flip(cmd->cmdsize))       // corrupt string reference
                return NULL;
        return sp;
}


//
// Figure out where the Code Signing information starts in the Mach-O binary image.
// The code signature is at the end of the file, and identified
// by a specially-named section. So its starting offset is also the end
// of the signable part.
// Note that the offset returned is relative to the start of the Mach-O image.
// Returns zero if not found (usually indicating that the binary was not signed).
//
const linkedit_data_command *MachOBase::findCodeSignature() const
{
        if (const load_command *cmd = findCommand(LC_CODE_SIGNATURE))
                return reinterpret_cast<const linkedit_data_command *>(cmd);
        return NULL;            // not found
}

size_t MachOBase::signingOffset() const
{
        if (const linkedit_data_command *lec = findCodeSignature())
                return flip(lec->dataoff);
        else
                return 0;
}

size_t MachOBase::signingLength() const
{
        if (const linkedit_data_command *lec = findCodeSignature())
                return flip(lec->datasize);
        else
                return 0;
}

const linkedit_data_command *MachOBase::findLibraryDependencies() const
{
        if (const load_command *cmd = findCommand(LC_DYLIB_CODE_SIGN_DRS))
                return reinterpret_cast<const linkedit_data_command *>(cmd);
        return NULL;            // not found
}


//
// Return the signing-limit length for this Mach-O binary image.
// This is the signingOffset if present, or the full length if not.
//
size_t MachO::signingExtent() const
{
        if (size_t offset = signingOffset())
                return offset;
        else
                return length();
}


//
// I/O operations
//
void MachO::seek(size_t offset)
{
        FileDesc::seek(mOffset + offset);
}

CFDataRef MachO::dataAt(size_t offset, size_t size)
{
        CFMallocData buffer(size);
        if (this->read(buffer, size, mOffset + offset) != size)
                UnixError::throwMe();
        return buffer;
}


//
// Fat (aka universal) file wrappers.
// The offset is relative to the start of the containing file.
//
Universal::Universal(FileDesc fd, size_t offset /* = 0 */)
        : FileDesc(fd), mBase(offset)
{
        union {
                fat_header header;              // if this is a fat file
                mach_header mheader;    // if this is a thin file
        };
        const size_t size = max(sizeof(header), sizeof(mheader));
        if (fd.read(&header, size, offset) != size)
                UnixError::throwMe(ENOEXEC);
        switch (header.magic) {
        case FAT_MAGIC:
        case FAT_CIGAM:
                {
                        //
                        // Hack alert.
                        // Under certain circumstances (15001604), mArchCount under-counts the architectures
                        // by one, and special testing is required to validate the extra-curricular entry.
                        // We always read an extra entry; in the situations where this might hit end-of-file,
                        // we are content to fail.
                        //
                        mArchCount = ntohl(header.nfat_arch);
                        size_t archSize = sizeof(fat_arch) * (mArchCount + 1);
                        mArchList = (fat_arch *)malloc(archSize);
                        if (!mArchList)
                                UnixError::throwMe();
                        if (fd.read(mArchList, archSize, mBase + sizeof(header)) != archSize) {
                                ::free(mArchList);
                                UnixError::throwMe(ENOEXEC);
                        }
                        for (fat_arch *arch = mArchList; arch <= mArchList + mArchCount; arch++) {
                                n2hi(arch->cputype);
                                n2hi(arch->cpusubtype);
                                n2hi(arch->offset);
                                n2hi(arch->size);
                                n2hi(arch->align);
                        }
                        const fat_arch *last_arch = mArchList + mArchCount;
                        if (last_arch->cputype == (CPU_ARCH_ABI64 | CPU_TYPE_ARM)) {
                                mArchCount++;
                        }
                        secdebug("macho", "%p is a fat file with %d architectures",
                                this, mArchCount);
                        break;
                }
        case MH_MAGIC:
        case MH_MAGIC_64:
                mArchList = NULL;
                mArchCount = 0;
                mThinArch = Architecture(mheader.cputype, mheader.cpusubtype);
                secdebug("macho", "%p is a thin file (%s)", this, mThinArch.name());
                break;
        case MH_CIGAM:
        case MH_CIGAM_64:
                mArchList = NULL;
                mArchCount = 0;
                mThinArch = Architecture(flip(mheader.cputype), flip(mheader.cpusubtype));
                secdebug("macho", "%p is a thin file (%s)", this, mThinArch.name());
                break;
        default:
                UnixError::throwMe(ENOEXEC);
        }
}

Universal::~Universal()
{
        ::free(mArchList);
}


//
// Get the "local" architecture from the fat file
// Throws ENOEXEC if not found.
//
MachO *Universal::architecture() const
{
        if (isUniversal())
                return findImage(bestNativeArch());
        else
                return new MachO(*this, mBase);
}

size_t Universal::archOffset() const
{
        if (isUniversal())
                return mBase + findArch(bestNativeArch())->offset;
        else
                return mBase;
}


//
// Get the specified architecture from the fat file
// Throws ENOEXEC if not found.
//
MachO *Universal::architecture(const Architecture &arch) const
{
        if (isUniversal())
                return findImage(arch);
        else if (mThinArch.matches(arch))
                return new MachO(*this, mBase);
        else
                UnixError::throwMe(ENOEXEC);
}

size_t Universal::archOffset(const Architecture &arch) const
{
        if (isUniversal())
                return mBase + findArch(arch)->offset;
        else if (mThinArch.matches(arch))
                return 0;
        else
                UnixError::throwMe(ENOEXEC);
}


//
// Get the architecture at a specified offset from the fat file.
// Throws an exception of the offset does not point at a Mach-O image.
//
MachO *Universal::architecture(size_t offset) const
{
        if (isUniversal())
                return new MachO(*this, offset);
        else if (offset == mBase)
                return new MachO(*this);
        else
                UnixError::throwMe(ENOEXEC);
}


//
// Locate an architecture from the fat file's list.
// Throws ENOEXEC if not found.
//
const fat_arch *Universal::findArch(const Architecture &target) const
{
        assert(isUniversal());
        const fat_arch *end = mArchList + mArchCount;
        // exact match
        for (const fat_arch *arch = mArchList; arch < end; ++arch)
                if (arch->cputype == target.cpuType()
                        && arch->cpusubtype == target.cpuSubtype())
                        return arch;
        // match for generic model of main architecture
        for (const fat_arch *arch = mArchList; arch < end; ++arch)
                if (arch->cputype == target.cpuType() && arch->cpusubtype == 0)
                        return arch;
        // match for any subarchitecture of the main architecture (questionable)
        for (const fat_arch *arch = mArchList; arch < end; ++arch)
                if (arch->cputype == target.cpuType())
                        return arch;
        // no match
        UnixError::throwMe(ENOEXEC);    // not found    
}

MachO *Universal::findImage(const Architecture &target) const
{
        const fat_arch *arch = findArch(target);
        return new MachO(*this, mBase + arch->offset, arch->size);
}


//
// Find the best-matching architecture for this fat file.
// We pick the native architecture if it's available.
// If it contains exactly one architecture, we take that.
// Otherwise, we throw.
//
Architecture Universal::bestNativeArch() const
{
        if (isUniversal()) {
                // ask the NXArch API for our native architecture
                const Architecture native = Architecture::local();
                if (fat_arch *match = NXFindBestFatArch(native.cpuType(), native.cpuSubtype(), mArchList, mArchCount))
                        return *match;
                // if the system can't figure it out, pick (arbitrarily) the first one
                return mArchList[0];
        } else
                return mThinArch;
}


//
// List all architectures from the fat file's list.
//
void Universal::architectures(Architectures &archs)
{
        if (isUniversal()) {
                for (unsigned n = 0; n < mArchCount; n++)
                        archs.insert(mArchList[n]);
        } else {
                auto_ptr<MachO> macho(architecture());
                archs.insert(macho->architecture());
        }
}


//
// Quickly guess the Mach-O type of a file.
// Returns type zero if the file isn't Mach-O or Universal.
// Always looks at the start of the file, and does not change the file pointer.
//
uint32_t Universal::typeOf(FileDesc fd)
{
        mach_header header;
        int max_tries = 3;
        if (fd.read(&header, sizeof(header), 0) != sizeof(header))
                return 0;
        while (max_tries > 0) {
                switch (header.magic) {
                case MH_MAGIC:
                case MH_MAGIC_64:
                        return header.filetype;
                        break;
                case MH_CIGAM:
                case MH_CIGAM_64:
                        return flip(header.filetype);
                        break;
                case FAT_MAGIC:
                case FAT_CIGAM:
                        {
                                const fat_arch *arch1 =
                                        LowLevelMemoryUtilities::increment<fat_arch>(&header, sizeof(fat_header));
                                if (fd.read(&header, sizeof(header), ntohl(arch1->offset)) != sizeof(header))
                                        return 0;
                                max_tries--;
                                continue;
                        }
                default:
                        return 0;
                }
        }
    return 0;
}


} // Security