def _CreateLoadForCompressedSection(data):
"""Creates a LOAD segment to previously created COMPRESSED_SECTION_NAME."""
elf_hdr = elf_headers.ElfHeader(data)
section_offset = None
section_size = None
for shdr in elf_hdr.GetSectionHeaders():
if shdr.GetStrName() == COMPRESSED_SECTION_NAME:
section_offset = shdr.sh_offset
section_size = shdr.sh_size
break
if section_offset is None:
raise RuntimeError('Failed to locate {} section in file'.format(
COMPRESSED_SECTION_NAME))
unaligned_new_vaddr = _FindNewVaddr(elf_hdr.GetProgramHeaders())
new_vaddr = MatchVaddrAlignment(unaligned_new_vaddr, section_offset)
elf_hdr.AddProgramHeader(
elf_headers.ProgramHeader.Create(
elf_hdr.byte_order,
p_type=elf_headers.ProgramHeader.Type.PT_LOAD,
p_flags=elf_headers.ProgramHeader.Flags.PF_R,
p_offset=section_offset,
p_vaddr=new_vaddr,
p_paddr=new_vaddr,
p_filesz=section_size,
p_memsz=section_size,
p_align=ADDRESS_ALIGN,
))
elf_hdr.PatchData(data)
def testElfHeaderNoopPatching(self):
"""Patching the ELF without any changes."""
with open(self.library_path, 'rb') as f:
data = bytearray(f.read())
data_copy = data[:]
elf = elf_headers.ElfHeader(data)
elf.PatchData(data)
self.assertEqual(data, data_copy)
def testElfHeaderPatchingAndParsing(self):
"""Patching the ELF and validating that it worked."""
with open(self.library_path, 'rb') as f:
data = bytearray(f.read())
elf = elf_headers.ElfHeader(data)
# Changing some values.
elf.e_ehsize = 42
elf.GetProgramHeaders()[0].p_align = 1
elf.GetProgramHeaders()[0].p_filesz = 10
elf.PatchData(data)
updated_elf = elf_headers.ElfHeader(data)
# Validating all of the ELF header fields.
self.assertEqual(updated_elf.e_type, elf.e_type)
self.assertEqual(updated_elf.e_entry, elf.e_entry)
self.assertEqual(updated_elf.e_phoff, elf.e_phoff)
self.assertEqual(updated_elf.e_shoff, elf.e_shoff)
self.assertEqual(updated_elf.e_flags, elf.e_flags)
self.assertEqual(updated_elf.e_ehsize, 42)
self.assertEqual(updated_elf.e_phentsize, elf.e_phentsize)
self.assertEqual(updated_elf.e_phnum, elf.e_phnum)
self.assertEqual(updated_elf.e_shentsize, elf.e_shentsize)
self.assertEqual(updated_elf.e_shnum, elf.e_shnum)
self.assertEqual(updated_elf.e_shstrndx, elf.e_shstrndx)
# Validating all of the fields of the first segment.
load_phdr = elf.GetProgramHeaders()[0]
updated_load_phdr = updated_elf.GetProgramHeaders()[0]
self.assertEqual(updated_load_phdr.p_offset, load_phdr.p_offset)
self.assertEqual(updated_load_phdr.p_vaddr, load_phdr.p_vaddr)
self.assertEqual(updated_load_phdr.p_paddr, load_phdr.p_paddr)
self.assertEqual(updated_load_phdr.p_filesz, 10)
self.assertEqual(updated_load_phdr.p_memsz, load_phdr.p_memsz)
self.assertEqual(updated_load_phdr.p_flags, load_phdr.p_flags)
self.assertEqual(updated_load_phdr.p_align, 1)
def testElfHeaderParsing(self):
with open(self.library_path, 'rb') as f:
data = f.read()
elf = elf_headers.ElfHeader(data)
# Validating all of the ELF header fields.
self.assertEqual(elf.e_type, elf_headers.ElfHeader.EType.ET_DYN)
self.assertEqual(elf.e_entry, 0x1040)
self.assertEqual(elf.e_phoff, 64)
self.assertEqual(elf.e_shoff, 14136)
self.assertEqual(elf.e_flags, 0)
self.assertEqual(elf.e_ehsize, 64)
self.assertEqual(elf.e_phentsize, 56)
self.assertEqual(elf.e_phnum, 8)
self.assertEqual(elf.e_shentsize, 64)
self.assertEqual(elf.e_shnum, 26)
self.assertEqual(elf.e_shstrndx, 25)
# Validating types and amounts of all segments excluding GNU specific ones.
phdrs = elf.GetPhdrs()
self.assertEqual(len(phdrs), 8)
phdr_types = [
elf_headers.ProgramHeader.Type.PT_LOAD,
elf_headers.ProgramHeader.Type.PT_LOAD,
elf_headers.ProgramHeader.Type.PT_LOAD,
elf_headers.ProgramHeader.Type.PT_LOAD,
elf_headers.ProgramHeader.Type.PT_DYNAMIC,
None,
None,
None,
]
for i in range(0, len(phdrs)):
if phdr_types[i] is not None:
self.assertEqual(phdrs[i].p_type, phdr_types[i])
# Validating all of the fields of the first segment.
load_phdr = phdrs[0]
self.assertEqual(load_phdr.p_offset, 0x0)
self.assertEqual(load_phdr.p_vaddr, 0x0)
self.assertEqual(load_phdr.p_paddr, 0x0)
self.assertEqual(load_phdr.p_filesz, 0x468)
self.assertEqual(load_phdr.p_memsz, 0x468)
self.assertEqual(load_phdr.p_flags, 0b100)
self.assertEqual(load_phdr.p_align, 0x1000)
# Validating offsets of the second segment
load_phdr = phdrs[1]
self.assertEqual(load_phdr.p_offset, 0x1000)
self.assertEqual(load_phdr.p_vaddr, 0x1000)
self.assertEqual(load_phdr.p_paddr, 0x1000)
def _MovePhdrToTheEnd(data):
"""Moves Phdrs to the end of the file and adjusts all references to it."""
elf_hdr = elf_headers.ElfHeader(data)
# If program headers are already in the end of the file, nothing to do.
if elf_hdr.e_phoff + elf_hdr.e_phnum * elf_hdr.e_phentsize == len(data):
return
old_phoff = elf_hdr.e_phoff
new_phoff = elf_hdr.e_phoff = len(data)
unaligned_new_vaddr = _FindNewVaddr(elf_hdr.GetProgramHeaders())
new_vaddr = MatchVaddrAlignment(unaligned_new_vaddr, new_phoff)
# Since we moved the PHDR section to the end of the file, we need to create a
# new LOAD segment to load it in.
current_filesize = elf_hdr.e_phnum * elf_hdr.e_phentsize
# We are using current_filesize while adding new program header due to
# AddProgramHeader handling the increase of size due to addition of new
# header.
elf_hdr.AddProgramHeader(
elf_headers.ProgramHeader.Create(
elf_hdr.byte_order,
p_type=elf_headers.ProgramHeader.Type.PT_LOAD,
p_flags=elf_headers.ProgramHeader.Flags.PF_R,
p_offset=new_phoff,
p_vaddr=new_vaddr,
p_paddr=new_vaddr,
p_filesz=current_filesize,
p_memsz=current_filesize,
p_align=ADDRESS_ALIGN,
))
# PHDR segment if it exists should point to the new location.
for phdr in elf_hdr.GetProgramHeadersByType(
elf_headers.ProgramHeader.Type.PT_PHDR):
phdr.p_offset = new_phoff
phdr.p_vaddr = new_vaddr
phdr.p_paddr = new_vaddr
phdr.p_align = ADDRESS_ALIGN
# We need to replace the previous phdr placement with zero bytes to fail
# fast if dynamic linker doesn't like the new program header.
previous_phdr_size = (elf_hdr.e_phnum - 1) * elf_hdr.e_phentsize
data[old_phoff:old_phoff + previous_phdr_size] = [0] * previous_phdr_size
# Updating ELF header to point to the new location.
elf_hdr.PatchData(data)
def _FileRangeToVirtualAddressRange(data, l, r):
"""Returns virtual address range corresponding to given file range.
Since we have to resolve them by their virtual address, parsing of LOAD
segments is required here.
"""
elf = elf_headers.ElfHeader(data)
for phdr in elf.GetPhdrs():
if phdr.p_type == elf_headers.ProgramHeader.Type.PT_LOAD.value:
# Current version of the prototype only supports ranges which are fully
# contained inside one LOAD segment. It should cover most of the common
# cases.
if phdr.p_offset >= r or phdr.p_offset + phdr.p_filesz <= l:
# Range doesn't overlap.
continue
if phdr.p_offset > l or phdr.p_offset + phdr.p_filesz < r:
# Range overlap with LOAD segment but isn't fully covered by it.
raise RuntimeError(
'Range is not contained within one LOAD segment')
l_virt = phdr.p_vaddr + (l - phdr.p_offset)
r_virt = phdr.p_vaddr + (r - phdr.p_offset)
return l_virt, r_virt
raise RuntimeError('Specified range is outside of all LOAD segments.')
def testElfHeaderSectionNames(self):
"""Test that the section names are correctly resolved"""
with open(self.library_path, 'rb') as f:
data = f.read()
elf = elf_headers.ElfHeader(data)
section_names = [
'',
'.hash',
'.gnu.hash',
'.dynsym',
'.dynstr',
'.gnu.version',
'.gnu.version_r',
'.rela.dyn',
'.init',
'.plt',
'.plt.got',
'.text',
'.fini',
'.eh_frame_hdr',
'.eh_frame',
'.init_array',
'.fini_array',
'.dynamic',
'.got',
'.got.plt',
'.data',
'.bss',
'.comment',
'.symtab',
'.strtab',
'.shstrtab',
]
shdrs = elf.GetSectionHeaders()
for i in range(0, len(shdrs)):
self.assertEqual(shdrs[i].GetStrName(), section_names[i])
def testElfHeaderParsing(self):
with open(self.library_path, 'rb') as f:
data = f.read()
elf = elf_headers.ElfHeader(data)
# Validating all of the ELF header fields.
self.assertEqual(elf.e_type, elf_headers.ElfHeader.EType.ET_DYN)
self.assertEqual(elf.e_entry, 0x1040)
self.assertEqual(elf.e_phoff, 64)
self.assertEqual(elf.e_shoff, 14136)
self.assertEqual(elf.e_flags, 0)
self.assertEqual(elf.e_ehsize, 64)
self.assertEqual(elf.e_phentsize, 56)
self.assertEqual(elf.e_phnum, 8)
self.assertEqual(elf.e_shentsize, 64)
self.assertEqual(elf.e_shnum, 26)
self.assertEqual(elf.e_shstrndx, 25)
# Validating types and amount of all segments excluding GNU specific ones.
phdrs = elf.GetProgramHeaders()
self.assertEqual(len(phdrs), 8)
phdr_types = [
elf_headers.ProgramHeader.Type.PT_LOAD,
elf_headers.ProgramHeader.Type.PT_LOAD,
elf_headers.ProgramHeader.Type.PT_LOAD,
elf_headers.ProgramHeader.Type.PT_LOAD,
elf_headers.ProgramHeader.Type.PT_DYNAMIC,
None, # Non-standard segment: GNU_EH_FRAME
None, # Non-standard segment: GNU_STACK
None, # Non-standard segment: GNU_RELRO
]
for i in range(0, len(phdrs)):
if phdr_types[i] is not None:
self.assertEqual(phdrs[i].p_type, phdr_types[i])
# Validating all of the fields of the first segment.
load_phdr = phdrs[0]
self.assertEqual(load_phdr.p_offset, 0x0)
self.assertEqual(load_phdr.p_vaddr, 0x0)
self.assertEqual(load_phdr.p_paddr, 0x0)
self.assertEqual(load_phdr.p_filesz, 0x468)
self.assertEqual(load_phdr.p_memsz, 0x468)
self.assertEqual(load_phdr.p_flags, 0b100)
self.assertEqual(load_phdr.p_align, 0x1000)
# Validating offsets of the second segment
load_phdr = phdrs[1]
self.assertEqual(load_phdr.p_offset, 0x1000)
self.assertEqual(load_phdr.p_vaddr, 0x1000)
self.assertEqual(load_phdr.p_paddr, 0x1000)
# Validating types and amount of sections excluding GNU ones.
shdrs = elf.GetSectionHeaders()
self.assertEqual(len(shdrs), 26)
shdr_types = [
elf_headers.SectionHeader.Type.SHT_NULL,
elf_headers.SectionHeader.Type.SHT_HASH,
None, # Non-standard section: GNU_HASH
elf_headers.SectionHeader.Type.SHT_DYNSYM,
elf_headers.SectionHeader.Type.SHT_STRTAB,
None, # Non-standard section: VERSYM
None, # Non-standard section: VERNEED
elf_headers.SectionHeader.Type.SHT_RELA,
elf_headers.SectionHeader.Type.SHT_PROGBITS,
elf_headers.SectionHeader.Type.SHT_PROGBITS,
elf_headers.SectionHeader.Type.SHT_PROGBITS,
elf_headers.SectionHeader.Type.SHT_PROGBITS,
elf_headers.SectionHeader.Type.SHT_PROGBITS,
elf_headers.SectionHeader.Type.SHT_PROGBITS,
elf_headers.SectionHeader.Type.SHT_PROGBITS,
None, # Non-standard section: INIT_ARRAY
None, # Non-standard section: FINI_ARRAY
elf_headers.SectionHeader.Type.SHT_DYNAMIC,
elf_headers.SectionHeader.Type.SHT_PROGBITS,
elf_headers.SectionHeader.Type.SHT_PROGBITS,
elf_headers.SectionHeader.Type.SHT_PROGBITS,
elf_headers.SectionHeader.Type.SHT_NOBITS,
elf_headers.SectionHeader.Type.SHT_PROGBITS,
elf_headers.SectionHeader.Type.SHT_SYMTAB,
elf_headers.SectionHeader.Type.SHT_STRTAB,
elf_headers.SectionHeader.Type.SHT_STRTAB,
]
for i in range(0, len(shdrs)):
if shdr_types[i] is not None:
self.assertEqual(shdrs[i].sh_type, shdr_types[i])
# Validate all fields of the first and second section, since the first one
# is NULL section.
shdr = shdrs[0]
self.assertEqual(shdr.sh_flags, 0)
self.assertEqual(shdr.sh_addr, 0x0)
self.assertEqual(shdr.sh_offset, 0x0)
self.assertEqual(shdr.sh_size, 0x0)
self.assertEqual(shdr.sh_link, 0)
self.assertEqual(shdr.sh_info, 0)
self.assertEqual(shdr.sh_addralign, 0)
self.assertEqual(shdr.sh_entsize, 0)
shdr = shdrs[1]
self.assertEqual(shdr.sh_flags, 2)
self.assertEqual(shdr.sh_addr, 0x200)
self.assertEqual(shdr.sh_offset, 0x200)
self.assertEqual(shdr.sh_size, 0x30)
self.assertEqual(shdr.sh_link, 3)
self.assertEqual(shdr.sh_info, 0)
self.assertEqual(shdr.sh_addralign, 8)
self.assertEqual(shdr.sh_entsize, 4)
def _SplitLoadSegmentAndNullifyRange(data, l, r):
"""Find LOAD segment covering [l, r) and splits it into three segments.
Split is done so one of the LOAD segments contains only [l, r) and nothing
else. If the range is located at the start or at the end of the segment less
than three segments may be created.
The resulting LOAD segment containing [l, r) is edited so it sets the
corresponding virtual address range to zeroes, ignoring file content.
"""
elf_hdr = elf_headers.ElfHeader(data)
range_phdr = None
for phdr in elf_hdr.GetProgramHeadersByType(
elf_headers.ProgramHeader.Type.PT_LOAD):
if phdr.p_offset <= l and phdr.FilePositionEnd() >= r:
range_phdr = phdr
break
if range_phdr is None:
raise RuntimeError('No LOAD segment covering the range found')
# The range_phdr will become the LOAD segment containing the [l, r) range
# but we need to create the additional two segments.
left_segment_size = l - range_phdr.p_offset
if left_segment_size > 0:
# Creating LOAD segment containing the [phdr.p_offset, l) part.
elf_hdr.AddProgramHeader(
elf_headers.ProgramHeader.Create(
elf_hdr.byte_order,
p_type=range_phdr.p_type,
p_flags=range_phdr.p_flags,
p_offset=range_phdr.p_offset,
p_vaddr=range_phdr.p_vaddr,
p_paddr=range_phdr.p_paddr,
p_filesz=left_segment_size,
p_memsz=left_segment_size,
p_align=range_phdr.p_align,
))
if range_phdr.p_offset + range_phdr.p_memsz > r:
# Creating LOAD segment containing the [r, phdr.p_offset + phdr.p_memsz).
right_segment_delta = r - range_phdr.p_offset
right_segment_address = range_phdr.p_vaddr + right_segment_delta
right_segment_filesize = max(range_phdr.p_filesz - right_segment_delta,
0)
right_segment_memsize = range_phdr.p_memsz - right_segment_delta
elf_hdr.AddProgramHeader(
elf_headers.ProgramHeader.Create(
elf_hdr.byte_order,
p_type=range_phdr.p_type,
p_flags=range_phdr.p_flags,
p_offset=r,
p_vaddr=right_segment_address,
p_paddr=right_segment_address,
p_filesz=right_segment_filesize,
p_memsz=right_segment_memsize,
p_align=range_phdr.p_align,
))
# Modifying the range_phdr
central_segment_address = range_phdr.p_vaddr + left_segment_size
range_phdr.p_offset = l
range_phdr.p_vaddr = central_segment_address
range_phdr.p_paddr = central_segment_address
range_phdr.p_filesz = 0
range_phdr.p_memsz = r - l
elf_hdr.PatchData(data)
