342 lines
12 KiB
Python
342 lines
12 KiB
Python
"""
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This module contains function to analyse dynamic library
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headers to extract system information
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Currently only for MacOSX
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Library file on macosx system starts with Mach-O or Fat field.
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This can be distinguish by first 32 bites and it is called magic number.
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Proper value of magic number is with suffix _MAGIC. Suffix _CIGAM means
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reversed bytes order.
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Both fields can occur in two types: 32 and 64 bytes.
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FAT field inform that this library contains few version of library
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(typically for different types version). It contains
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information where Mach-O headers starts.
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Each section started with Mach-O header contains one library
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(So if file starts with this field it contains only one version).
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After filed Mach-O there are section fields.
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Each of them starts with two fields:
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cmd - magic number for this command
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cmdsize - total size occupied by this section information.
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In this case only sections LC_VERSION_MIN_MACOSX (for macosx 10.13 and earlier)
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and LC_BUILD_VERSION (for macosx 10.14 and newer) are interesting,
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because them contains information about minimal system version.
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Important remarks:
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- For fat files this implementation looks for maximum number version.
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It not check if it is 32 or 64 and do not compare it with currently builded package.
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So it is possible to false report higher version that needed.
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- All structures signatures are taken form macosx header files.
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- I think that binary format will be more stable than `otool` output.
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and if apple introduce some changes both implementation will need to be updated.
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"""
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import ctypes
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import sys
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"""here the needed const and struct from mach-o header files"""
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FAT_MAGIC = 0xcafebabe
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FAT_CIGAM = 0xbebafeca
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FAT_MAGIC_64 = 0xcafebabf
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FAT_CIGAM_64 = 0xbfbafeca
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MH_MAGIC = 0xfeedface
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MH_CIGAM = 0xcefaedfe
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MH_MAGIC_64 = 0xfeedfacf
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MH_CIGAM_64 = 0xcffaedfe
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LC_VERSION_MIN_MACOSX = 0x24
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LC_BUILD_VERSION = 0x32
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mach_header_fields = [
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("magic", ctypes.c_uint32), ("cputype", ctypes.c_int),
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("cpusubtype", ctypes.c_int), ("filetype", ctypes.c_uint32),
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("ncmds", ctypes.c_uint32), ("sizeofcmds", ctypes.c_uint32),
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("flags", ctypes.c_uint32)
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]
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"""
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struct mach_header {
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uint32_t magic; /* mach magic number identifier */
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cpu_type_t cputype; /* cpu specifier */
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cpu_subtype_t cpusubtype; /* machine specifier */
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uint32_t filetype; /* type of file */
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uint32_t ncmds; /* number of load commands */
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uint32_t sizeofcmds; /* the size of all the load commands */
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uint32_t flags; /* flags */
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};
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typedef integer_t cpu_type_t;
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typedef integer_t cpu_subtype_t;
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"""
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mach_header_fields_64 = mach_header_fields + [("reserved", ctypes.c_uint32)]
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"""
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struct mach_header_64 {
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uint32_t magic; /* mach magic number identifier */
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cpu_type_t cputype; /* cpu specifier */
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cpu_subtype_t cpusubtype; /* machine specifier */
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uint32_t filetype; /* type of file */
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uint32_t ncmds; /* number of load commands */
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uint32_t sizeofcmds; /* the size of all the load commands */
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uint32_t flags; /* flags */
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uint32_t reserved; /* reserved */
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};
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"""
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fat_header_fields = [("magic", ctypes.c_uint32), ("nfat_arch", ctypes.c_uint32)]
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"""
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struct fat_header {
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uint32_t magic; /* FAT_MAGIC or FAT_MAGIC_64 */
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uint32_t nfat_arch; /* number of structs that follow */
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};
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"""
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fat_arch_fields = [
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("cputype", ctypes.c_int), ("cpusubtype", ctypes.c_int),
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("offset", ctypes.c_uint32), ("size", ctypes.c_uint32),
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("align", ctypes.c_uint32)
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]
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"""
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struct fat_arch {
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cpu_type_t cputype; /* cpu specifier (int) */
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cpu_subtype_t cpusubtype; /* machine specifier (int) */
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uint32_t offset; /* file offset to this object file */
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uint32_t size; /* size of this object file */
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uint32_t align; /* alignment as a power of 2 */
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};
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"""
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fat_arch_64_fields = [
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("cputype", ctypes.c_int), ("cpusubtype", ctypes.c_int),
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("offset", ctypes.c_uint64), ("size", ctypes.c_uint64),
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("align", ctypes.c_uint32), ("reserved", ctypes.c_uint32)
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]
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"""
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struct fat_arch_64 {
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cpu_type_t cputype; /* cpu specifier (int) */
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cpu_subtype_t cpusubtype; /* machine specifier (int) */
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uint64_t offset; /* file offset to this object file */
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uint64_t size; /* size of this object file */
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uint32_t align; /* alignment as a power of 2 */
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uint32_t reserved; /* reserved */
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};
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"""
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segment_base_fields = [("cmd", ctypes.c_uint32), ("cmdsize", ctypes.c_uint32)]
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"""base for reading segment info"""
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segment_command_fields = [
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("cmd", ctypes.c_uint32), ("cmdsize", ctypes.c_uint32),
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("segname", ctypes.c_char * 16), ("vmaddr", ctypes.c_uint32),
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("vmsize", ctypes.c_uint32), ("fileoff", ctypes.c_uint32),
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("filesize", ctypes.c_uint32), ("maxprot", ctypes.c_int),
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("initprot", ctypes.c_int), ("nsects", ctypes.c_uint32),
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("flags", ctypes.c_uint32),
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]
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"""
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struct segment_command { /* for 32-bit architectures */
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uint32_t cmd; /* LC_SEGMENT */
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uint32_t cmdsize; /* includes sizeof section structs */
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char segname[16]; /* segment name */
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uint32_t vmaddr; /* memory address of this segment */
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uint32_t vmsize; /* memory size of this segment */
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uint32_t fileoff; /* file offset of this segment */
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uint32_t filesize; /* amount to map from the file */
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vm_prot_t maxprot; /* maximum VM protection */
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vm_prot_t initprot; /* initial VM protection */
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uint32_t nsects; /* number of sections in segment */
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uint32_t flags; /* flags */
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};
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typedef int vm_prot_t;
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"""
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segment_command_fields_64 = [
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("cmd", ctypes.c_uint32), ("cmdsize", ctypes.c_uint32),
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("segname", ctypes.c_char * 16), ("vmaddr", ctypes.c_uint64),
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("vmsize", ctypes.c_uint64), ("fileoff", ctypes.c_uint64),
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("filesize", ctypes.c_uint64), ("maxprot", ctypes.c_int),
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("initprot", ctypes.c_int), ("nsects", ctypes.c_uint32),
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("flags", ctypes.c_uint32),
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]
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"""
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struct segment_command_64 { /* for 64-bit architectures */
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uint32_t cmd; /* LC_SEGMENT_64 */
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uint32_t cmdsize; /* includes sizeof section_64 structs */
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char segname[16]; /* segment name */
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uint64_t vmaddr; /* memory address of this segment */
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uint64_t vmsize; /* memory size of this segment */
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uint64_t fileoff; /* file offset of this segment */
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uint64_t filesize; /* amount to map from the file */
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vm_prot_t maxprot; /* maximum VM protection */
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vm_prot_t initprot; /* initial VM protection */
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uint32_t nsects; /* number of sections in segment */
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uint32_t flags; /* flags */
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};
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"""
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version_min_command_fields = segment_base_fields + \
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[("version", ctypes.c_uint32), ("sdk", ctypes.c_uint32)]
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"""
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struct version_min_command {
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uint32_t cmd; /* LC_VERSION_MIN_MACOSX or
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LC_VERSION_MIN_IPHONEOS or
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LC_VERSION_MIN_WATCHOS or
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LC_VERSION_MIN_TVOS */
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uint32_t cmdsize; /* sizeof(struct min_version_command) */
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uint32_t version; /* X.Y.Z is encoded in nibbles xxxx.yy.zz */
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uint32_t sdk; /* X.Y.Z is encoded in nibbles xxxx.yy.zz */
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};
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"""
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build_version_command_fields = segment_base_fields + \
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[("platform", ctypes.c_uint32), ("minos", ctypes.c_uint32),
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("sdk", ctypes.c_uint32), ("ntools", ctypes.c_uint32)]
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"""
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struct build_version_command {
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uint32_t cmd; /* LC_BUILD_VERSION */
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uint32_t cmdsize; /* sizeof(struct build_version_command) plus */
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/* ntools * sizeof(struct build_tool_version) */
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uint32_t platform; /* platform */
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uint32_t minos; /* X.Y.Z is encoded in nibbles xxxx.yy.zz */
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uint32_t sdk; /* X.Y.Z is encoded in nibbles xxxx.yy.zz */
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uint32_t ntools; /* number of tool entries following this */
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};
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"""
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def swap32(x):
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return (((x << 24) & 0xFF000000) |
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((x << 8) & 0x00FF0000) |
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((x >> 8) & 0x0000FF00) |
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((x >> 24) & 0x000000FF))
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def get_base_class_and_magic_number(lib_file, seek=None):
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if seek is None:
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seek = lib_file.tell()
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else:
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lib_file.seek(seek)
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magic_number = ctypes.c_uint32.from_buffer_copy(
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lib_file.read(ctypes.sizeof(ctypes.c_uint32))).value
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# Handle wrong byte order
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if magic_number in [FAT_CIGAM, FAT_CIGAM_64, MH_CIGAM, MH_CIGAM_64]:
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if sys.byteorder == "little":
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BaseClass = ctypes.BigEndianStructure
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else:
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BaseClass = ctypes.LittleEndianStructure
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magic_number = swap32(magic_number)
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else:
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BaseClass = ctypes.Structure
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lib_file.seek(seek)
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return BaseClass, magic_number
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def read_data(struct_class, lib_file):
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return struct_class.from_buffer_copy(lib_file.read(
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ctypes.sizeof(struct_class)))
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def extract_macosx_min_system_version(path_to_lib):
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with open(path_to_lib, "rb") as lib_file:
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BaseClass, magic_number = get_base_class_and_magic_number(lib_file, 0)
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if magic_number not in [FAT_MAGIC, FAT_MAGIC_64, MH_MAGIC, MH_MAGIC_64]:
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return
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if magic_number in [FAT_MAGIC, FAT_CIGAM_64]:
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class FatHeader(BaseClass):
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_fields_ = fat_header_fields
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fat_header = read_data(FatHeader, lib_file)
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if magic_number == FAT_MAGIC:
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class FatArch(BaseClass):
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_fields_ = fat_arch_fields
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else:
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class FatArch(BaseClass):
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_fields_ = fat_arch_64_fields
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fat_arch_list = [read_data(FatArch, lib_file) for _ in range(fat_header.nfat_arch)]
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versions_list = []
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for el in fat_arch_list:
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try:
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version = read_mach_header(lib_file, el.offset)
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if version is not None:
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versions_list.append(version)
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except ValueError:
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pass
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if len(versions_list) > 0:
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return max(versions_list)
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else:
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return None
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else:
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try:
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return read_mach_header(lib_file, 0)
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except ValueError:
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"""when some error during read library files"""
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return None
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def read_mach_header(lib_file, seek=None):
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"""
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This funcition parse mach-O header and extract
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information about minimal system version
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:param lib_file: reference to opened library file with pointer
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"""
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if seek is not None:
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lib_file.seek(seek)
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base_class, magic_number = get_base_class_and_magic_number(lib_file)
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arch = "32" if magic_number == MH_MAGIC else "64"
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class SegmentBase(base_class):
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_fields_ = segment_base_fields
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if arch == "32":
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class MachHeader(base_class):
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_fields_ = mach_header_fields
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else:
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class MachHeader(base_class):
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_fields_ = mach_header_fields_64
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mach_header = read_data(MachHeader, lib_file)
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for _i in range(mach_header.ncmds):
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pos = lib_file.tell()
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segment_base = read_data(SegmentBase, lib_file)
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lib_file.seek(pos)
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if segment_base.cmd == LC_VERSION_MIN_MACOSX:
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class VersionMinCommand(base_class):
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_fields_ = version_min_command_fields
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version_info = read_data(VersionMinCommand, lib_file)
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return parse_version(version_info.version)
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elif segment_base.cmd == LC_BUILD_VERSION:
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class VersionBuild(base_class):
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_fields_ = build_version_command_fields
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version_info = read_data(VersionBuild, lib_file)
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return parse_version(version_info.minos)
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else:
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lib_file.seek(pos + segment_base.cmdsize)
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continue
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def parse_version(version):
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x = (version & 0xffff0000) >> 16
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y = (version & 0x0000ff00) >> 8
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z = (version & 0x000000ff)
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return x, y, z
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