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use crate::error::{self, Error};
use crate::pe::relocation;
use alloc::borrow::Cow;
use alloc::string::{String, ToString};
use alloc::vec::Vec;
use scroll::{ctx, Pread, Pwrite};
#[repr(C)]
#[derive(Debug, PartialEq, Clone, Default)]
pub struct SectionTable {
pub name: [u8; 8],
pub real_name: Option<String>,
pub virtual_size: u32,
pub virtual_address: u32,
pub size_of_raw_data: u32,
pub pointer_to_raw_data: u32,
pub pointer_to_relocations: u32,
pub pointer_to_linenumbers: u32,
pub number_of_relocations: u16,
pub number_of_linenumbers: u16,
pub characteristics: u32,
}
pub const SIZEOF_SECTION_TABLE: usize = 8 * 5;
// Decodes a string table entry in base 64 (//AAAAAA). Expects string without
// prefixed slashes.
fn base64_decode_string_entry(s: &str) -> Result<usize, ()> {
assert!(s.len() <= 6, "String too long, possible overflow.");
let mut val = 0;
for c in s.bytes() {
let v = if b'A' <= c && c <= b'Z' {
// 00..=25
c - b'A'
} else if b'a' <= c && c <= b'z' {
// 26..=51
c - b'a' + 26
} else if b'0' <= c && c <= b'9' {
// 52..=61
c - b'0' + 52
} else if c == b'+' {
// 62
62
} else if c == b'/' {
// 63
63
} else {
return Err(());
};
val = val * 64 + v as usize;
}
Ok(val)
}
impl SectionTable {
pub fn parse(
bytes: &[u8],
offset: &mut usize,
string_table_offset: usize,
) -> error::Result<Self> {
let mut table = SectionTable::default();
let mut name = [0u8; 8];
name.copy_from_slice(bytes.gread_with(offset, 8)?);
table.name = name;
table.virtual_size = bytes.gread_with(offset, scroll::LE)?;
table.virtual_address = bytes.gread_with(offset, scroll::LE)?;
table.size_of_raw_data = bytes.gread_with(offset, scroll::LE)?;
table.pointer_to_raw_data = bytes.gread_with(offset, scroll::LE)?;
table.pointer_to_relocations = bytes.gread_with(offset, scroll::LE)?;
table.pointer_to_linenumbers = bytes.gread_with(offset, scroll::LE)?;
table.number_of_relocations = bytes.gread_with(offset, scroll::LE)?;
table.number_of_linenumbers = bytes.gread_with(offset, scroll::LE)?;
table.characteristics = bytes.gread_with(offset, scroll::LE)?;
if let Some(idx) = table.name_offset()? {
table.real_name = Some(bytes.pread::<&str>(string_table_offset + idx)?.to_string());
}
Ok(table)
}
pub fn data<'a, 'b: 'a>(&'a self, pe_bytes: &'b [u8]) -> error::Result<Option<Cow<[u8]>>> {
let section_start: usize = self.pointer_to_raw_data.try_into().map_err(|_| {
Error::Malformed(format!("Virtual address cannot fit in platform `usize`"))
})?;
// assert!(self.virtual_size <= self.size_of_raw_data);
// if vsize > size_of_raw_data, the section is zero padded.
let section_end: usize = section_start
+ usize::try_from(self.size_of_raw_data).map_err(|_| {
Error::Malformed(format!("Virtual size cannot fit in platform `usize`"))
})?;
let original_bytes = pe_bytes.get(section_start..section_end).map(Cow::Borrowed);
if original_bytes.is_some() && self.virtual_size > self.size_of_raw_data {
let mut bytes: Vec<u8> = Vec::new();
bytes.resize(self.size_of_raw_data.try_into()?, 0);
bytes.copy_from_slice(&original_bytes.unwrap());
bytes.resize(self.virtual_size.try_into()?, 0);
Ok(Some(Cow::Owned(bytes)))
} else {
Ok(original_bytes)
}
}
pub fn name_offset(&self) -> error::Result<Option<usize>> {
if self.name[0] == b'/' {
let idx: usize = if self.name[1] == b'/' {
let b64idx = self.name.pread::<&str>(2)?;
base64_decode_string_entry(b64idx).map_err(|_| {
Error::Malformed(format!(
"Invalid indirect section name //{}: base64 decoding failed",
b64idx
))
})?
} else {
let name = self.name.pread::<&str>(1)?;
name.parse().map_err(|err| {
Error::Malformed(format!("Invalid indirect section name /{}: {}", name, err))
})?
};
Ok(Some(idx))
} else {
Ok(None)
}
}
#[allow(clippy::useless_let_if_seq)]
pub fn set_name_offset(&mut self, mut idx: usize) -> error::Result<()> {
if idx <= 9_999_999 {
// 10^7 - 1
// write!(&mut self.name[1..], "{}", idx) without using io::Write.
// We write into a temporary since we calculate digits starting at the right.
let mut name = [0; 7];
let mut len = 0;
if idx == 0 {
name[6] = b'0';
len = 1;
} else {
while idx != 0 {
let rem = (idx % 10) as u8;
idx /= 10;
name[6 - len] = b'0' + rem;
len += 1;
}
}
self.name = [0; 8];
self.name[0] = b'/';
self.name[1..][..len].copy_from_slice(&name[7 - len..]);
Ok(())
} else if idx as u64 <= 0xfff_fff_fff {
// 64^6 - 1
self.name[0] = b'/';
self.name[1] = b'/';
for i in 0..6 {
let rem = (idx % 64) as u8;
idx /= 64;
let c = match rem {
0..=25 => b'A' + rem,
26..=51 => b'a' + rem - 26,
52..=61 => b'0' + rem - 52,
62 => b'+',
63 => b'/',
_ => unreachable!(),
};
self.name[7 - i] = c;
}
Ok(())
} else {
Err(Error::Malformed(format!(
"Invalid section name offset: {}",
idx
)))
}
}
pub fn name(&self) -> error::Result<&str> {
match self.real_name.as_ref() {
Some(s) => Ok(s),
None => Ok(self.name.pread(0)?),
}
}
pub fn relocations<'a>(&self, bytes: &'a [u8]) -> error::Result<relocation::Relocations<'a>> {
let offset = self.pointer_to_relocations as usize;
let number = self.number_of_relocations as usize;
relocation::Relocations::parse(bytes, offset, number)
}
/// Tests if `another_section` on-disk ranges will collide.
pub fn overlaps_with(&self, another_section: &SectionTable) -> bool {
let self_end = self.pointer_to_raw_data + self.size_of_raw_data;
let another_end = another_section.pointer_to_raw_data + another_section.size_of_raw_data;
!((self_end <= another_section.pointer_to_raw_data)
|| (another_end <= self.pointer_to_raw_data))
}
}
impl ctx::SizeWith<scroll::Endian> for SectionTable {
fn size_with(_ctx: &scroll::Endian) -> usize {
SIZEOF_SECTION_TABLE
}
}
impl ctx::TryIntoCtx<scroll::Endian> for &SectionTable {
type Error = error::Error;
fn try_into_ctx(self, bytes: &mut [u8], ctx: scroll::Endian) -> Result<usize, Self::Error> {
let offset = &mut 0;
bytes.gwrite(&self.name[..], offset)?;
bytes.gwrite_with(self.virtual_size, offset, ctx)?;
bytes.gwrite_with(self.virtual_address, offset, ctx)?;
bytes.gwrite_with(self.size_of_raw_data, offset, ctx)?;
bytes.gwrite_with(self.pointer_to_raw_data, offset, ctx)?;
bytes.gwrite_with(self.pointer_to_relocations, offset, ctx)?;
bytes.gwrite_with(self.pointer_to_linenumbers, offset, ctx)?;
bytes.gwrite_with(self.number_of_relocations, offset, ctx)?;
bytes.gwrite_with(self.number_of_linenumbers, offset, ctx)?;
bytes.gwrite_with(self.characteristics, offset, ctx)?;
Ok(SIZEOF_SECTION_TABLE)
}
}
impl ctx::IntoCtx<scroll::Endian> for &SectionTable {
fn into_ctx(self, bytes: &mut [u8], ctx: scroll::Endian) {
bytes.pwrite_with(self, 0, ctx).unwrap();
}
}
/// The section should not be padded to the next boundary. This flag is obsolete and is replaced
/// by `IMAGE_SCN_ALIGN_1BYTES`. This is valid only for object files.
pub const IMAGE_SCN_TYPE_NO_PAD: u32 = 0x0000_0008;
/// The section contains executable code.
pub const IMAGE_SCN_CNT_CODE: u32 = 0x0000_0020;
/// The section contains initialized data.
pub const IMAGE_SCN_CNT_INITIALIZED_DATA: u32 = 0x0000_0040;
/// The section contains uninitialized data.
pub const IMAGE_SCN_CNT_UNINITIALIZED_DATA: u32 = 0x0000_0080;
pub const IMAGE_SCN_LNK_OTHER: u32 = 0x0000_0100;
/// The section contains comments or other information. The .drectve section has this type.
/// This is valid for object files only.
pub const IMAGE_SCN_LNK_INFO: u32 = 0x0000_0200;
/// The section will not become part of the image. This is valid only for object files.
pub const IMAGE_SCN_LNK_REMOVE: u32 = 0x0000_0800;
/// The section contains COMDAT data. This is valid only for object files.
pub const IMAGE_SCN_LNK_COMDAT: u32 = 0x0000_1000;
/// The section contains data referenced through the global pointer (GP).
pub const IMAGE_SCN_GPREL: u32 = 0x0000_8000;
pub const IMAGE_SCN_MEM_PURGEABLE: u32 = 0x0002_0000;
pub const IMAGE_SCN_MEM_16BIT: u32 = 0x0002_0000;
pub const IMAGE_SCN_MEM_LOCKED: u32 = 0x0004_0000;
pub const IMAGE_SCN_MEM_PRELOAD: u32 = 0x0008_0000;
pub const IMAGE_SCN_ALIGN_1BYTES: u32 = 0x0010_0000;
pub const IMAGE_SCN_ALIGN_2BYTES: u32 = 0x0020_0000;
pub const IMAGE_SCN_ALIGN_4BYTES: u32 = 0x0030_0000;
pub const IMAGE_SCN_ALIGN_8BYTES: u32 = 0x0040_0000;
pub const IMAGE_SCN_ALIGN_16BYTES: u32 = 0x0050_0000;
pub const IMAGE_SCN_ALIGN_32BYTES: u32 = 0x0060_0000;
pub const IMAGE_SCN_ALIGN_64BYTES: u32 = 0x0070_0000;
pub const IMAGE_SCN_ALIGN_128BYTES: u32 = 0x0080_0000;
pub const IMAGE_SCN_ALIGN_256BYTES: u32 = 0x0090_0000;
pub const IMAGE_SCN_ALIGN_512BYTES: u32 = 0x00A0_0000;
pub const IMAGE_SCN_ALIGN_1024BYTES: u32 = 0x00B0_0000;
pub const IMAGE_SCN_ALIGN_2048BYTES: u32 = 0x00C0_0000;
pub const IMAGE_SCN_ALIGN_4096BYTES: u32 = 0x00D0_0000;
pub const IMAGE_SCN_ALIGN_8192BYTES: u32 = 0x00E0_0000;
pub const IMAGE_SCN_ALIGN_MASK: u32 = 0x00F0_0000;
/// The section contains extended relocations.
pub const IMAGE_SCN_LNK_NRELOC_OVFL: u32 = 0x0100_0000;
/// The section can be discarded as needed.
pub const IMAGE_SCN_MEM_DISCARDABLE: u32 = 0x0200_0000;
/// The section cannot be cached.
pub const IMAGE_SCN_MEM_NOT_CACHED: u32 = 0x0400_0000;
/// The section is not pageable.
pub const IMAGE_SCN_MEM_NOT_PAGED: u32 = 0x0800_0000;
/// The section can be shared in memory.
pub const IMAGE_SCN_MEM_SHARED: u32 = 0x1000_0000;
/// The section can be executed as code.
pub const IMAGE_SCN_MEM_EXECUTE: u32 = 0x2000_0000;
/// The section can be read.
pub const IMAGE_SCN_MEM_READ: u32 = 0x4000_0000;
/// The section can be written to.
pub const IMAGE_SCN_MEM_WRITE: u32 = 0x8000_0000;
#[cfg(test)]
mod tests {
use super::*;
#[test]
fn set_name_offset() {
let mut section = SectionTable::default();
for &(offset, name) in [
(0usize, b"/0\0\0\0\0\0\0"),
(1, b"/1\0\0\0\0\0\0"),
(9_999_999, b"/9999999"),
(10_000_000, b"//AAmJaA"),
#[cfg(target_pointer_width = "64")]
(0xfff_fff_fff, b"////////"),
]
.iter()
{
section.set_name_offset(offset).unwrap();
assert_eq!(§ion.name, name);
assert_eq!(section.name_offset().unwrap(), Some(offset));
}
#[cfg(target_pointer_width = "64")]
assert!(section.set_name_offset(0x1_000_000_000).is_err());
}
}