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use crate::error;
use alloc::string::ToString;
use alloc::vec::Vec;
use scroll::Pread;
use super::options;
use super::section_table;
use crate::pe::data_directories::DataDirectory;
use core::cmp;
use log::debug;
pub fn is_in_range(rva: usize, r1: usize, r2: usize) -> bool {
r1 <= rva && rva < r2
}
// reference: Peter Ferrie. Reliable algorithm to extract overlay of a PE. https://bit.ly/2vBX2bR
#[inline]
fn aligned_pointer_to_raw_data(pointer_to_raw_data: usize) -> usize {
const PHYSICAL_ALIGN: usize = 0x1ff;
pointer_to_raw_data & !PHYSICAL_ALIGN
}
#[inline]
fn section_read_size(section: §ion_table::SectionTable, file_alignment: u32) -> usize {
fn round_size(size: usize) -> usize {
const PAGE_MASK: usize = 0xfff;
(size + PAGE_MASK) & !PAGE_MASK
}
// Paraphrased from https://reverseengineering.stackexchange.com/a/4326 (by Peter Ferrie).
//
// Handles the corner cases such as mis-aligned pointers (round down) and sizes (round up)
// Further rounding corner cases:
// - the physical pointer should be rounded down to a multiple of 512, regardless of the value in the header
// - the read size is rounded up by using a combination of the file alignment and 4kb
// - the virtual size is always rounded up to a multiple of 4kb, regardless of the value in the header.
//
// Reference C implementation:
//
// long pointerToRaw = section.get(POINTER_TO_RAW_DATA);
// long alignedpointerToRaw = pointerToRaw & ~0x1ff;
// long sizeOfRaw = section.get(SIZE_OF_RAW_DATA);
// long readsize = ((pointerToRaw + sizeOfRaw) + filealign - 1) & ~(filealign - 1)) - alignedpointerToRaw;
// readsize = min(readsize, (sizeOfRaw + 0xfff) & ~0xfff);
// long virtsize = section.get(VIRTUAL_SIZE);
//
// if (virtsize)
// {
// readsize = min(readsize, (virtsize + 0xfff) & ~0xfff);
// }
let file_alignment = file_alignment as usize;
let size_of_raw_data = section.size_of_raw_data as usize;
let virtual_size = section.virtual_size as usize;
let read_size = {
let read_size =
((section.pointer_to_raw_data as usize + size_of_raw_data + file_alignment - 1)
& !(file_alignment - 1))
- aligned_pointer_to_raw_data(section.pointer_to_raw_data as usize);
cmp::min(read_size, round_size(size_of_raw_data))
};
if virtual_size == 0 {
read_size
} else {
cmp::min(read_size, round_size(virtual_size))
}
}
fn rva2offset(rva: usize, section: §ion_table::SectionTable) -> usize {
(rva - section.virtual_address as usize)
+ aligned_pointer_to_raw_data(section.pointer_to_raw_data as usize)
}
fn is_in_section(rva: usize, section: §ion_table::SectionTable, file_alignment: u32) -> bool {
let section_rva = section.virtual_address as usize;
is_in_range(
rva,
section_rva,
section_rva + section_read_size(section, file_alignment),
)
}
pub fn find_offset(
rva: usize,
sections: &[section_table::SectionTable],
file_alignment: u32,
opts: &options::ParseOptions,
) -> Option<usize> {
if opts.resolve_rva {
if file_alignment == 0 || file_alignment & (file_alignment - 1) != 0 {
return None;
}
for (i, section) in sections.iter().enumerate() {
debug!(
"Checking {} for {:#x} ∈ {:#x}..{:#x}",
section.name().unwrap_or(""),
rva,
section.virtual_address,
section.virtual_address + section.virtual_size
);
if is_in_section(rva, §ion, file_alignment) {
let offset = rva2offset(rva, §ion);
debug!(
"Found in section {}({}), remapped into offset {:#x}",
section.name().unwrap_or(""),
i,
offset
);
return Some(offset);
}
}
None
} else {
Some(rva)
}
}
pub fn find_offset_or(
rva: usize,
sections: &[section_table::SectionTable],
file_alignment: u32,
opts: &options::ParseOptions,
msg: &str,
) -> error::Result<usize> {
find_offset(rva, sections, file_alignment, opts)
.ok_or_else(|| error::Error::Malformed(msg.to_string()))
}
pub fn try_name<'a>(
bytes: &'a [u8],
rva: usize,
sections: &[section_table::SectionTable],
file_alignment: u32,
opts: &options::ParseOptions,
) -> error::Result<&'a str> {
match find_offset(rva, sections, file_alignment, opts) {
Some(offset) => Ok(bytes.pread::<&str>(offset)?),
None => Err(error::Error::Malformed(format!(
"Cannot find name from rva {:#x} in sections: {:?}",
rva, sections
))),
}
}
pub fn get_data<'a, T>(
bytes: &'a [u8],
sections: &[section_table::SectionTable],
directory: DataDirectory,
file_alignment: u32,
) -> error::Result<T>
where
T: scroll::ctx::TryFromCtx<'a, scroll::Endian, Error = scroll::Error>,
{
get_data_with_opts(
bytes,
sections,
directory,
file_alignment,
&options::ParseOptions::default(),
)
}
pub fn get_data_with_opts<'a, T>(
bytes: &'a [u8],
sections: &[section_table::SectionTable],
directory: DataDirectory,
file_alignment: u32,
opts: &options::ParseOptions,
) -> error::Result<T>
where
T: scroll::ctx::TryFromCtx<'a, scroll::Endian, Error = scroll::Error>,
{
let rva = directory.virtual_address as usize;
let offset = find_offset(rva, sections, file_alignment, opts)
.ok_or_else(|| error::Error::Malformed(directory.virtual_address.to_string()))?;
let result: T = bytes.pread_with(offset, scroll::LE)?;
Ok(result)
}
pub(crate) fn pad(length: usize, alignment: Option<usize>) -> Option<Vec<u8>> {
match alignment {
Some(alignment) => {
let overhang = length % alignment;
if overhang != 0 {
let repeat = alignment - overhang;
Some(vec![0u8; repeat])
} else {
None
}
}
None => None,
}
}
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