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# Section Operations
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Methods for working with PE sections, including accessing section data and metadata. Sections contain the actual code, data, and resources of the PE file, organized into logical segments with specific characteristics and permissions.
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## Capabilities
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### Section Access
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Locate and access sections by address or offset.
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```python { .api }
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def get_section_by_rva(self, rva):
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"""
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Get section containing the specified RVA.
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Args:
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rva (int): Relative virtual address
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Returns:
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SectionStructure: Section containing the RVA, or None if not found
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"""
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def get_section_by_offset(self, offset):
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"""
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Get section containing the specified file offset.
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Args:
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offset (int): File offset
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Returns:
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SectionStructure: Section containing the offset, or None if not found
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"""
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```
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### Section Data Management
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Apply modifications made to section data back to the PE structure.
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```python { .api }
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def merge_modified_section_data(self):
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"""
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Update PE internal data with modified section data.
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This method applies any changes made to section data back to the
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main PE data structure, ensuring consistency between section objects
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and the underlying file data. Must be called after modifying section
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data through section.set_data() or direct manipulation.
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"""
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```
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### SectionStructure Methods
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Individual section objects provide detailed access to section data and properties.
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```python { .api }
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class SectionStructure:
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def get_data(self, start=None, length=None, ignore_padding=False):
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"""
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Get section data.
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Args:
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start (int, optional): Start offset within section
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length (int, optional): Number of bytes to read
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ignore_padding (bool): Whether to ignore alignment padding
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Returns:
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bytes: Section data
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"""
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def get_entropy(self):
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"""
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Calculate Shannon entropy of section data.
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Returns:
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float: Entropy value (0.0 to 8.0), higher values indicate more randomness
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"""
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def get_hash_md5(self):
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"""
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Calculate MD5 hash of section data.
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Returns:
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str: MD5 hash as hexadecimal string
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"""
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def get_hash_sha1(self):
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"""
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Calculate SHA-1 hash of section data.
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Returns:
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str: SHA-1 hash as hexadecimal string
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"""
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def get_hash_sha256(self):
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"""
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Calculate SHA-256 hash of section data.
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Returns:
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str: SHA-256 hash as hexadecimal string
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"""
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def get_hash_sha512(self):
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"""
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Calculate SHA-512 hash of section data.
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Returns:
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str: SHA-512 hash as hexadecimal string
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"""
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def contains_rva(self, rva):
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"""
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Check if section contains the specified RVA.
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Args:
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rva (int): Relative virtual address
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Returns:
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bool: True if RVA is within section bounds
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"""
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def contains_offset(self, offset):
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"""
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Check if section contains the specified file offset.
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Args:
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offset (int): File offset
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Returns:
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bool: True if offset is within section bounds
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"""
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```
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### Section Parsing
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Parse section headers from the PE file.
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```python { .api }
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def parse_sections(self, offset):
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"""
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Parse section headers starting at specified offset.
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Args:
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offset (int): File offset where section headers begin
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Populates:
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self.sections: List of SectionStructure objects
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"""
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```
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## Section Structure Attributes
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Each section in the `pe.sections` list is a `SectionStructure` object with the following key attributes:
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```python { .api }
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class SectionStructure:
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"""Represents a PE file section."""
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Name: bytes # Section name (8 bytes, null-padded)
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VirtualSize: int # Size of section when loaded in memory
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VirtualAddress: int # RVA where section is loaded
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SizeOfRawData: int # Size of section in file
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PointerToRawData: int # File offset to section data
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PointerToRelocations: int # File offset to relocations
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PointerToLinenumbers: int # File offset to line numbers
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NumberOfRelocations: int # Number of relocations
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NumberOfLinenumbers: int # Number of line number entries
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Characteristics: int # Section characteristics/flags
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def get_data(self, start=None, length=None):
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"""Get section data."""
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def set_data(self, data):
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"""Set section data."""
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def get_entropy(self):
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"""Calculate section entropy."""
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def get_hash_sha1(self):
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"""Get SHA1 hash of section data."""
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def get_hash_sha256(self):
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"""Get SHA256 hash of section data."""
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def get_hash_md5(self):
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"""Get MD5 hash of section data."""
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```
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## Usage Examples
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### Basic Section Analysis
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```python
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import pefile
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with pefile.PE('executable.exe') as pe:
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print("Section Analysis:")
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print("-" * 60)
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print(f"{'Name':<10} {'VirtAddr':<10} {'VirtSize':<10} {'RawSize':<10} {'Entropy':<8}")
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print("-" * 60)
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for section in pe.sections:
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name = section.Name.decode('utf-8').strip('\x00')
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virt_addr = f"0x{section.VirtualAddress:08x}"
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virt_size = f"0x{section.VirtualSize:08x}"
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raw_size = f"0x{section.SizeOfRawData:08x}"
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entropy = f"{section.get_entropy():.2f}"
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print(f"{name:<10} {virt_addr:<10} {virt_size:<10} {raw_size:<10} {entropy:<8}")
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```
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### Section Characteristics Analysis
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```python
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import pefile
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with pefile.PE('executable.exe') as pe:
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print("Section Characteristics:")
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print("-" * 40)
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for section in pe.sections:
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name = section.Name.decode('utf-8').strip('\x00')
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characteristics = section.Characteristics
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print(f"\nSection: {name}")
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print(f"Characteristics: 0x{characteristics:08x}")
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# Decode characteristics flags
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flags = []
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if characteristics & 0x00000020: # IMAGE_SCN_CNT_CODE
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flags.append("CODE")
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if characteristics & 0x00000040: # IMAGE_SCN_CNT_INITIALIZED_DATA
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flags.append("INITIALIZED_DATA")
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if characteristics & 0x00000080: # IMAGE_SCN_CNT_UNINITIALIZED_DATA
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flags.append("UNINITIALIZED_DATA")
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if characteristics & 0x20000000: # IMAGE_SCN_MEM_EXECUTE
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flags.append("EXECUTABLE")
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if characteristics & 0x40000000: # IMAGE_SCN_MEM_READ
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flags.append("READABLE")
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if characteristics & 0x80000000: # IMAGE_SCN_MEM_WRITE
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flags.append("WRITABLE")
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if flags:
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print(f"Flags: {', '.join(flags)}")
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```
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### Section Data Extraction
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```python
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import pefile
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import os
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with pefile.PE('executable.exe') as pe:
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# Create directory for section dumps
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output_dir = 'section_dumps'
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os.makedirs(output_dir, exist_ok=True)
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for i, section in enumerate(pe.sections):
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name = section.Name.decode('utf-8').strip('\x00')
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# Get section data
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section_data = section.get_data()
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# Save section to file
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filename = f"{output_dir}/{i:02d}_{name}.bin"
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with open(filename, 'wb') as f:
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f.write(section_data)
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print(f"Extracted {name}: {len(section_data)} bytes -> {filename}")
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# Calculate hashes
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sha256 = section.get_hash_sha256()
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md5 = section.get_hash_md5()
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entropy = section.get_entropy()
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print(f" SHA256: {sha256}")
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print(f" MD5: {md5}")
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print(f" Entropy: {entropy:.3f}")
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```
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### Section Modification
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```python
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import pefile
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# Load PE file
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pe = pefile.PE('executable.exe')
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# Find text section
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text_section = None
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for section in pe.sections:
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name = section.Name.decode('utf-8').strip('\x00')
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if name == '.text':
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text_section = section
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break
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if text_section:
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print(f"Found .text section at RVA 0x{text_section.VirtualAddress:08x}")
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# Get current section data
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original_data = text_section.get_data()
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print(f"Original size: {len(original_data)} bytes")
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# Modify section data (example: NOP out first few bytes)
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modified_data = bytearray(original_data)
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modified_data[0:10] = b'\x90' * 10 # NOP instructions
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# Set modified data back to section
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text_section.set_data(bytes(modified_data))
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# Apply changes to PE structure
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pe.merge_modified_section_data()
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# Write modified PE
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pe.write('modified_executable.exe')
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print("Modified executable saved")
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pe.close()
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```
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### Finding Sections by Address
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```python
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import pefile
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with pefile.PE('executable.exe') as pe:
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# Find section containing entry point
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entry_point = pe.OPTIONAL_HEADER.AddressOfEntryPoint
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entry_section = pe.get_section_by_rva(entry_point)
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if entry_section:
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name = entry_section.Name.decode('utf-8').strip('\x00')
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print(f"Entry point 0x{entry_point:08x} is in section: {name}")
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# Calculate offset within section
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section_offset = entry_point - entry_section.VirtualAddress
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print(f"Offset within section: 0x{section_offset:08x}")
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# Find section containing specific file offset
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file_offset = 0x1000
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offset_section = pe.get_section_by_offset(file_offset)
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if offset_section:
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name = offset_section.Name.decode('utf-8').strip('\x00')
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print(f"File offset 0x{file_offset:08x} is in section: {name}")
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```
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### Section Entropy Analysis
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```python
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import pefile
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def analyze_entropy(pe):
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"""Analyze section entropy to detect packing."""
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print("Entropy Analysis:")
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print("-" * 30)
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high_entropy_sections = []
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for section in pe.sections:
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name = section.Name.decode('utf-8').strip('\x00')
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entropy = section.get_entropy()
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print(f"{name:<10}: {entropy:.3f}")
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# Flag high entropy sections (possibly packed/encrypted)
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if entropy > 7.0: # High entropy threshold
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high_entropy_sections.append((name, entropy))
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if high_entropy_sections:
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print("\nHigh entropy sections (possibly packed):")
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for name, entropy in high_entropy_sections:
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print(f" {name}: {entropy:.3f}")
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return high_entropy_sections
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# Usage
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with pefile.PE('executable.exe') as pe:
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high_entropy = analyze_entropy(pe)
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```
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### Section Alignment Utilities
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```python
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import pefile
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with pefile.PE('executable.exe') as pe:
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file_alignment = pe.OPTIONAL_HEADER.FileAlignment
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section_alignment = pe.OPTIONAL_HEADER.SectionAlignment
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print(f"File Alignment: 0x{file_alignment:x}")
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print(f"Section Alignment: 0x{section_alignment:x}")
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print()
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for section in pe.sections:
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name = section.Name.decode('utf-8').strip('\x00')
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# Check alignment
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raw_addr_aligned = (section.PointerToRawData % file_alignment) == 0
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virt_addr_aligned = (section.VirtualAddress % section_alignment) == 0
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print(f"Section {name}:")
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print(f" Raw Address: 0x{section.PointerToRawData:08x} (aligned: {raw_addr_aligned})")
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print(f" Virtual Address: 0x{section.VirtualAddress:08x} (aligned: {virt_addr_aligned})")
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```