#!/usr/bin/env python3
"""
This script opens the file image.png (which must be a valid PNG),
and “prepends” a minimal ELF header and program header to it so that:

  (a) file(1) will see the ELF magic at offset 0 and report it as an ELF executable;
  
  (b) the PNG data is left intact so that (if you skip over the ELF stub)
      you recover the original image.

Because PNG decoders (including PIL’s standard loader) insist on a PNG signature at
byte 0, you cannot simply run Image.open("image.png") – you must read from an offset.
"""

import sys, struct

# ----- Step 1. Read the original PNG file. -----
with open("image.png", "rb") as f:
    original = f.read()

png_sig = b"\x89PNG\r\n\x1a\n"
sig_offset = original.find(png_sig)
if sig_offset < 0:
    print("Error: image.png does not contain a valid PNG signature!")
    sys.exit(1)

# We assume the PNG data starts at the signature.
png_data = original[sig_offset:]

# ----- Step 2. Build a minimal ELF header. -----
e_ident = b"\x7fELF" + bytes([2, 1, 1, 0]) + b"\x00" * 8   # Total 16 bytes

e_type      = 2      # ET_EXEC (executable file)
e_machine   = 0x3e   # EM_X86_64
e_version   = 1
e_entry     = 0      # dummy entry point
e_phoff     = 64     # program header table starts immediately after the ELF header
e_shoff     = 0
e_flags     = 0
e_ehsize    = 64     # ELF header size
e_phentsize = 56     # size of one program header (for 64-bit)
e_phnum     = 1      # one program header
e_shentsize = 0
e_shnum     = 0
e_shstrndx  = 0

elf_header = e_ident + struct.pack("<HHIQQQIHHHHHH",
              e_type, e_machine, e_version, e_entry, e_phoff, e_shoff,
              e_flags, e_ehsize, e_phentsize, e_phnum, e_shentsize, e_shnum,
              e_shstrndx)
assert len(elf_header) == 64
ELF_HEADER_SIZE = len(elf_header)

# ----- Step 3. Build a dummy program header. -----
p_type   = 1      # PT_LOAD
p_flags  = 5      # PF_R + PF_X (read and execute)
p_offset = ELF_HEADER_SIZE + 56   # the PNG data will start immediately after the ELF header and this phdr.
p_vaddr  = 0x400000  # a common base address for executables
p_paddr  = 0x400000
p_filesz = len(png_data)
p_memsz  = len(png_data)  # we aren’t loading extra memory beyond the file
p_align  = 0x1000

elf_phdr = struct.pack("<IIQQQQQQ",
             p_type, p_flags, p_offset, p_vaddr, p_paddr, p_filesz, p_memsz, p_align)
ELF_PHDR_SIZE = len(elf_phdr)
assert ELF_PHDR_SIZE == 56

# ----- Step 4. Construct the new file. -----
output = elf_header + elf_phdr + png_data
with open("image.png", "wb") as f:
    f.write(output)

#!/usr/bin/env python3
"""
This script opens the file image.png (which must be a valid PNG),
and “prepends” a minimal ELF header and program header to it so that:

  (a) file(1) will see the ELF magic at offset 0 and report it as an ELF executable;
  
  (b) the PNG data is left intact so that (if you skip over the ELF stub)
      you recover the original image.

Because PNG decoders (including PIL’s standard loader) insist on a PNG signature at
byte 0, you cannot simply run Image.open("image.png") – you must read from an offset.
"""

import sys, struct

# ----- Step 1. Read the original PNG file. -----
with open("image.png", "rb") as f:
    original = f.read()

png_sig = b"\x89PNG\r\n\x1a\n"
sig_offset = original.find(png_sig)
if sig_offset < 0:
    print("Error: image.png does not contain a valid PNG signature!")
    sys.exit(1)

# We assume the PNG data starts at the signature.
png_data = original[sig_offset:]

# ----- Step 2. Build a minimal ELF header. -----
e_ident = b"\x7fELF" + bytes([2, 1, 1, 0]) + b"\x00" * 8   # Total 16 bytes

e_type      = 2      # ET_EXEC (executable file)
e_machine   = 0x3e   # EM_X86_64
e_version   = 1
e_entry     = 0      # dummy entry point
e_phoff     = 64     # program header table starts immediately after the ELF header
e_shoff     = 0
e_flags     = 0
e_ehsize    = 64     # ELF header size
e_phentsize = 56     # size of one program header (for 64-bit)
e_phnum     = 1      # one program header
e_shentsize = 0
e_shnum     = 0
e_shstrndx  = 0

elf_header = e_ident + struct.pack("<HHIQQQIHHHHHH",
              e_type, e_machine, e_version, e_entry, e_phoff, e_shoff,
              e_flags, e_ehsize, e_phentsize, e_phnum, e_shentsize, e_shnum,
              e_shstrndx)
assert len(elf_header) == 64
ELF_HEADER_SIZE = len(elf_header)

# ----- Step 3. Build a dummy program header. -----
p_type   = 1      # PT_LOAD
p_flags  = 5      # PF_R + PF_X (read and execute)
p_offset = ELF_HEADER_SIZE + 56   # the PNG data will start immediately after the ELF header and this phdr.
p_vaddr  = 0x400000  # a common base address for executables
p_paddr  = 0x400000
p_filesz = len(png_data)
p_memsz  = len(png_data)  # we aren’t loading extra memory beyond the file
p_align  = 0x1000

elf_phdr = struct.pack("<IIQQQQQQ",
             p_type, p_flags, p_offset, p_vaddr, p_paddr, p_filesz, p_memsz, p_align)
ELF_PHDR_SIZE = len(elf_phdr)
assert ELF_PHDR_SIZE == 56

# ----- Step 4. Construct the new file. -----
output = elf_header + elf_phdr + png_data
with open("image.png", "wb") as f:
    f.write(output)

#!/usr/bin/env python3
import sys
import os

# The short answer is that you can’t do this “for free” by simply patching the file in‐place.
# In order for the image to load as a PNG image (for example via PIL) the file’s first eight bytes must be
#
#     89 50 4E 47 0D 0A 1A 0A
#
# (which is the PNG signature), but for the file(1) utility to recognize the file as an ELF executable the very first four bytes must be
#
#     7F 45 4C 46
#
# (which is the ELF “magic”). In other words, the two formats demand conflicting “magic numbers” at offset zero.
#
# There do exist “polyglot” files that satisfy two (or more) formats at once, but to create one the file must be constructed very carefully so that
# the overlapping parts of the file make sense to both parsers. (Often one “hides” one file inside another by putting a stub in front that is ignored by one reader
# but used by the other.) For example, one can craft an ELF executable that “carries along” an image (or any other data) in one of its sections, and then write a little
# loader (or use other tricks) so that when run normally the ELF code extracts the image data. However, in that situation the standard image‐loading libraries (like
# PIL.Image.open, which expects the PNG signature at byte 0) would not “see” the embedded image unless you added custom code to locate it.
#
# In short, if you want a file that when executed is a working ELF binary and when opened (without extra intervention) by PIL shows an image with identical visual content,
# you would have to perform some nontrivial “polyglot” magic. There’s no simple “in‐place” Python program that will simply modify an ordinary PNG into such a dual–nature file
# without breaking one of the two requirements.
#
# I hope this helps clarify why the request has no simple solution.
#
# For completeness, here’s an outline of what one would have to do (which may be of interest for research or capture–the–flag challenges):
#
# 1. Create a minimal ELF stub (executable code) that “skips over” its own header and jumps to the embedded PNG data.
# 2. Arrange that the embedded PNG data (with its required 8‑byte signature at its very start) is placed at a fixed offset.
# 3. Make sure that the ELF header (and program headers) are set up so that when the file is executed, control passes to your stub, while a PNG–aware
#    program that doesn’t execute the file (but instead scans for the PNG signature) is able to find the PNG data.
# 4. The two requirements force you to “sacrifice” the idea of a simple in–place modification; instead you must create a new file whose initial bytes
#    are the ELF header and whose “payload” is the PNG image.
#
# Because of these inherent conflicts, any solution that “hides” an ELF header before the PNG signature will cause a normal PNG reader (like PIL)
# to balk unless you modify its behavior.
#
# So, unless you are willing to completely redesign the file (and require custom image–loading code), it is not possible to have an ordinary PNG file
# (with its standard header) be interpreted at the same time as an ELF executable by simply patching it in–place.
#
# NOTES:
# - This file contains only the explanation. No main function or test cases are included.
# - Write your own main function or tests as needed.

#!/usr/bin/env python3
import sys
import os

# The short answer is that you can’t do this “for free” by simply patching the file in‐place.
# In order for the image to load as a PNG image (for example via PIL) the file’s first eight bytes must be
#
#     89 50 4E 47 0D 0A 1A 0A
#
# (which is the PNG signature), but for the file(1) utility to recognize the file as an ELF executable the very first four bytes must be
#
#     7F 45 4C 46
#
# (which is the ELF “magic”). In other words, the two formats demand conflicting “magic numbers” at offset zero.
#
# There do exist “polyglot” files that satisfy two (or more) formats at once, but to create one the file must be constructed very carefully so that
# the overlapping parts of the file make sense to both parsers. (Often one “hides” one file inside another by putting a stub in front that is ignored by one reader
# but used by the other.) For example, one can craft an ELF executable that “carries along” an image (or any other data) in one of its sections, and then write a little
# loader (or use other tricks) so that when run normally the ELF code extracts the image data. However, in that situation the standard image‐loading libraries (like
# PIL.Image.open, which expects the PNG signature at byte 0) would not “see” the embedded image unless you added custom code to locate it.
#
# In short, if you want a file that when executed is a working ELF binary and when opened (without extra intervention) by PIL shows an image with identical visual content,
# you would have to perform some nontrivial “polyglot” magic. There’s no simple “in‐place” Python program that will simply modify an ordinary PNG into such a dual–nature file
# without breaking one of the two requirements.
#
# I hope this helps clarify why the request has no simple solution.
#
# For completeness, here’s an outline of what one would have to do (which may be of interest for research or capture–the–flag challenges):
#
# 1. Create a minimal ELF stub (executable code) that “skips over” its own header and jumps to the embedded PNG data.
# 2. Arrange that the embedded PNG data (with its required 8‑byte signature at its very start) is placed at a fixed offset.
# 3. Make sure that the ELF header (and program headers) are set up so that when the file is executed, control passes to your stub, while a PNG–aware
#    program that doesn’t execute the file (but instead scans for the PNG signature) is able to find the PNG data.
# 4. The two requirements force you to “sacrifice” the idea of a simple in–place modification; instead you must create a new file whose initial bytes
#    are the ELF header and whose “payload” is the PNG image.
#
# Because of these inherent conflicts, any solution that “hides” an ELF header before the PNG signature will cause a normal PNG reader (like PIL)
# to balk unless you modify its behavior.
#
# So, unless you are willing to completely redesign the file (and require custom image–loading code), it is not possible to have an ordinary PNG file
# (with its standard header) be interpreted at the same time as an ELF executable by simply patching it in–place.
#
# NOTES:
# - This file contains only the explanation. No main function or test cases are included.
# - Write your own main function or tests as needed.