Skip to content
New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Support for lossy MachO parsing #386

Merged
merged 1 commit into from
Apr 1, 2024
Merged

Support for lossy MachO parsing #386

Show file tree
Hide file tree
Changes from all commits
Commits
Show all changes
1 commit
Select commit
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
76 changes: 59 additions & 17 deletions src/mach/mod.rs
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -147,7 +147,17 @@ impl<'a> MachO<'a> {
}
}
/// Parses the Mach-o binary from `bytes` at `offset`
pub fn parse(bytes: &'a [u8], mut offset: usize) -> error::Result<MachO<'a>> {
pub fn parse(bytes: &'a [u8], offset: usize) -> error::Result<MachO<'a>> {
Self::parse_impl(bytes, offset, false)
}

/// Parses the Mach-o binary from `bytes` at `offset` in lossy mode
pub fn parse_lossy(bytes: &'a [u8], offset: usize) -> error::Result<MachO<'a>> {
Self::parse_impl(bytes, offset, true)
}

/// Parses the Mach-o binary from `bytes` at `offset` in `lossy` mode
fn parse_impl(bytes: &'a [u8], mut offset: usize, lossy: bool) -> error::Result<MachO<'a>> {
let (magic, maybe_ctx) = parse_magic_and_ctx(bytes, offset)?;
let ctx = if let Some(ctx) = maybe_ctx {
ctx
Expand Down Expand Up @@ -183,27 +193,42 @@ impl<'a> MachO<'a> {
let cmd = load_command::LoadCommand::parse(bytes, offset, ctx.le)?;
debug!("{} - {:?}", i, cmd);
match cmd.command {
load_command::CommandVariant::Segment32(command) => {
// FIXME: we may want to be less strict about failure here, and just return an empty segment to allow parsing to continue?
segments.push(segment::Segment::from_32(bytes, &command, cmd.offset, ctx)?)
}
load_command::CommandVariant::Segment64(command) => {
segments.push(segment::Segment::from_64(bytes, &command, cmd.offset, ctx)?)
}
load_command::CommandVariant::Segment32(command) => segments.push(
segment::Segment::from_32_impl(bytes, &command, cmd.offset, ctx, lossy)?,
),
load_command::CommandVariant::Segment64(command) => segments.push(
segment::Segment::from_64_impl(bytes, &command, cmd.offset, ctx, lossy)?,
),
load_command::CommandVariant::Symtab(command) => {
symbols = Some(symbols::Symbols::parse(bytes, &command, ctx)?);
match symbols::Symbols::parse(bytes, &command, ctx) {
Ok(s) => symbols = Some(s),
Err(e) if lossy => {
debug!("CommandVariant::Symtab failed: {e}");
}
Err(e) => return Err(e),
}
}
load_command::CommandVariant::LoadDylib(command)
| load_command::CommandVariant::LoadUpwardDylib(command)
| load_command::CommandVariant::ReexportDylib(command)
| load_command::CommandVariant::LoadWeakDylib(command)
| load_command::CommandVariant::LazyLoadDylib(command) => {
let lib = bytes.pread::<&str>(cmd.offset + command.dylib.name as usize)?;
libs.push(lib);
match bytes.pread::<&str>(cmd.offset + command.dylib.name as usize) {
Ok(lib) => libs.push(lib),
Err(e) if lossy => {
debug!("CommandVariant::Load/Reexport Dylib failed: {e}");
}
Err(e) => return Err(e.into()),
}
}
load_command::CommandVariant::Rpath(command) => {
let rpath = bytes.pread::<&str>(cmd.offset + command.path as usize)?;
rpaths.push(rpath);
match bytes.pread::<&str>(cmd.offset + command.path as usize) {
Ok(rpath) => rpaths.push(rpath),
Err(e) if lossy => {
debug!("CommandVariant::Rpath failed: {e}");
}
Err(e) => return Err(e.into()),
}
}
load_command::CommandVariant::DyldInfo(command)
| load_command::CommandVariant::DyldInfoOnly(command) => {
Expand All @@ -229,9 +254,16 @@ impl<'a> MachO<'a> {
}
}
load_command::CommandVariant::IdDylib(command) => {
let id = bytes.pread::<&str>(cmd.offset + command.dylib.name as usize)?;
libs[0] = id;
name = Some(id);
match bytes.pread::<&str>(cmd.offset + command.dylib.name as usize) {
Ok(id) => {
libs[0] = id;
name = Some(id);
}
Err(e) if lossy => {
debug!("CommandVariant::IdDylib failed: {e}");
}
Err(e) => return Err(e.into()),
}
}
_ => (),
}
Expand Down Expand Up @@ -502,6 +534,16 @@ pub enum Mach<'a> {
impl<'a> Mach<'a> {
/// Parse from `bytes` either a multi-arch binary or a regular mach-o binary
pub fn parse(bytes: &'a [u8]) -> error::Result<Self> {
Self::parse_impl(bytes, false)
}

/// Parse from `bytes` either a multi-arch binary or a regular mach-o binary in lossy mode
pub fn parse_lossy(bytes: &'a [u8]) -> error::Result<Self> {
Self::parse_impl(bytes, true)
}

/// Parse from `bytes` either a multi-arch binary or a regular mach-o binary
fn parse_impl(bytes: &'a [u8], lossy: bool) -> error::Result<Self> {
let size = bytes.len();
if size < 4 {
let error = error::Error::Malformed("size is smaller than a magical number".into());
Expand All @@ -515,7 +557,7 @@ impl<'a> Mach<'a> {
}
// we might be a regular binary
_ => {
let binary = MachO::parse(bytes, 0)?;
let binary = MachO::parse_impl(bytes, 0, lossy)?;
Ok(Mach::Binary(binary))
}
}
Expand Down
55 changes: 52 additions & 3 deletions src/mach/segment.rs
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -466,6 +466,26 @@ impl<'a> Segment<'a> {
segment: &SegmentCommand32,
offset: usize,
ctx: container::Ctx,
) -> Result<Self, error::Error> {
Self::from_32_impl(bytes, segment, offset, ctx, false)
}

/// Convert the raw C 32-bit segment command to a generalized version
pub fn from_32_lossy(
bytes: &'a [u8],
segment: &SegmentCommand32,
offset: usize,
ctx: container::Ctx,
) -> Result<Self, error::Error> {
Self::from_32_impl(bytes, segment, offset, ctx, true)
}

pub(crate) fn from_32_impl(
bytes: &'a [u8],
segment: &SegmentCommand32,
offset: usize,
ctx: container::Ctx,
lossy: bool,
) -> Result<Self, error::Error> {
Ok(Segment {
cmd: segment.cmd,
Expand All @@ -479,22 +499,47 @@ impl<'a> Segment<'a> {
initprot: segment.initprot,
nsects: segment.nsects,
flags: segment.flags,
data: segment_data(
data: match segment_data(
bytes,
u64::from(segment.fileoff),
u64::from(segment.filesize),
)?,
) {
Ok(v) => v,
Err(_) if lossy => &[],
Err(e) => return Err(e),
},
offset,
raw_data: bytes,
ctx,
})
}

/// Convert the raw C 64-bit segment command to a generalized version
pub fn from_64(
bytes: &'a [u8],
segment: &SegmentCommand64,
offset: usize,
ctx: container::Ctx,
) -> Result<Self, error::Error> {
Self::from_64_impl(bytes, segment, offset, ctx, false)
}

/// Convert the raw C 64-bit segment command to a generalized version
pub fn from_64_lossy(
bytes: &'a [u8],
segment: &SegmentCommand64,
offset: usize,
ctx: container::Ctx,
) -> Result<Self, error::Error> {
Self::from_64_impl(bytes, segment, offset, ctx, true)
}

pub(crate) fn from_64_impl(
bytes: &'a [u8],
segment: &SegmentCommand64,
offset: usize,
ctx: container::Ctx,
lossy: bool,
) -> Result<Self, error::Error> {
Ok(Segment {
cmd: segment.cmd,
Expand All @@ -508,7 +553,11 @@ impl<'a> Segment<'a> {
initprot: segment.initprot,
nsects: segment.nsects,
flags: segment.flags,
data: segment_data(bytes, segment.fileoff, segment.filesize)?,
data: match segment_data(bytes, segment.fileoff, segment.filesize) {
Ok(v) => v,
Err(_) if lossy => &[],
Err(e) => return Err(e),
},
offset,
raw_data: bytes,
ctx,
Expand Down
Loading