use crate::EventSectionReader;
use crate::{AliasSectionReader, InstanceSectionReader};
use crate::{BinaryReader, BinaryReaderError, FunctionBody, Range, Result};
use crate::{DataSectionReader, ElementSectionReader, ExportSectionReader};
use crate::{FunctionSectionReader, ImportSectionReader, TypeSectionReader};
use crate::{GlobalSectionReader, MemorySectionReader, TableSectionReader};
use std::convert::TryInto;
use std::fmt;
use std::iter;
/// An incremental parser of a binary WebAssembly module.
///
/// This type is intended to be used to incrementally parse a WebAssembly module
/// as bytes become available for the module. This can also be used to parse
/// modules that are already entirely resident within memory.
///
/// This primary function for a parser is the [`Parser::parse`] function which
/// will incrementally consume input. You can also use the [`Parser::parse_all`]
/// function to parse a module that is entirely resident in memory.
#[derive(Debug, Clone)]
pub struct Parser {
state: State,
offset: u64,
max_size: u64,
}
#[derive(Debug, Clone)]
enum State {
ModuleHeader,
SectionStart,
FunctionBody { remaining: u32, len: u32 },
Module { remaining: u32, len: u32 },
}
/// A successful return payload from [`Parser::parse`].
///
/// On success one of two possible values can be returned, either that more data
/// is needed to continue parsing or a chunk of the input was parsed, indicating
/// how much of it was parsed.
#[derive(Debug)]
pub enum Chunk<'a> {
/// This can be returned at any time and indicates that more data is needed
/// to proceed with parsing. Zero bytes were consumed from the input to
/// [`Parser::parse`]. The `usize` value here is a hint as to how many more
/// bytes are needed to continue parsing.
NeedMoreData(u64),
/// A chunk was successfully parsed.
Parsed {
/// This many bytes of the `data` input to [`Parser::parse`] were
/// consumed to produce `payload`.
consumed: usize,
/// The value that we actually parsed.
payload: Payload<'a>,
},
}
/// Values that can be parsed from a wasm module.
///
/// This enumeration is all possible chunks of pieces that can be parsed by a
/// [`Parser`] from a binary WebAssembly module. Note that for many sections the
/// entire section is parsed all at once, whereas other functions, like the code
/// section, are parsed incrementally. This is a distinction where some
/// sections, like the type section, are required to be fully resident in memory
/// (fully downloaded) before proceeding. Other sections, like the code section,
/// can be processed in a streaming fashion where each function is extracted
/// individually so it can possibly be shipped to another thread while you wait
/// for more functions to get downloaded.
///
/// Note that payloads, when returned, do not indicate that the wasm module is
/// valid. For example when you receive a `Payload::TypeSection` the type
/// section itself has not yet actually been parsed. The reader returned will be
/// able to parse it, but you'll have to actually iterate the reader to do the
/// full parse. Each payload returned is intended to be a *window* into the
/// original `data` passed to [`Parser::parse`] which can be further processed
/// if necessary.
pub enum Payload<'a> {
/// Indicates the header of a WebAssembly binary.
///
/// This header also indicates the version number that was parsed, which is
/// currently always 1.
Version {
/// The version number found
num: u32,
/// The range of bytes that were parsed to consume the header of the
/// module. Note that this range is relative to the start of the byte
/// stream.
range: Range,
},
/// A type section was received, and the provided reader can be used to
/// parse the contents of the type section.
TypeSection(crate::TypeSectionReader<'a>),
/// A import section was received, and the provided reader can be used to
/// parse the contents of the import section.
ImportSection(crate::ImportSectionReader<'a>),
/// An alias section was received, and the provided reader can be used to
/// parse the contents of the alias section.
AliasSection(crate::AliasSectionReader<'a>),
/// An instance section was received, and the provided reader can be used to
/// parse the contents of the instance section.
InstanceSection(crate::InstanceSectionReader<'a>),
/// A function section was received, and the provided reader can be used to
/// parse the contents of the function section.
FunctionSection(crate::FunctionSectionReader<'a>),
/// A table section was received, and the provided reader can be used to
/// parse the contents of the table section.
TableSection(crate::TableSectionReader<'a>),
/// A memory section was received, and the provided reader can be used to
/// parse the contents of the memory section.
MemorySection(crate::MemorySectionReader<'a>),
/// An event section was received, and the provided reader can be used to
/// parse the contents of the event section.
EventSection(crate::EventSectionReader<'a>),
/// A global section was received, and the provided reader can be used to
/// parse the contents of the global section.
GlobalSection(crate::GlobalSectionReader<'a>),
/// An export section was received, and the provided reader can be used to
/// parse the contents of the export section.
ExportSection(crate::ExportSectionReader<'a>),
/// A start section was received, and the `u32` here is the index of the
/// start function.
StartSection {
/// The start function index
func: u32,
/// The range of bytes that specify the `func` field, specified in
/// offsets relative to the start of the byte stream.
range: Range,
},
/// An element section was received, and the provided reader can be used to
/// parse the contents of the element section.
ElementSection(crate::ElementSectionReader<'a>),
/// A data count section was received, and the `u32` here is the contents of
/// the data count section.
DataCountSection {
/// The number of data segments.
count: u32,
/// The range of bytes that specify the `count` field, specified in
/// offsets relative to the start of the byte stream.
range: Range,
},
/// A data section was received, and the provided reader can be used to
/// parse the contents of the data section.
DataSection(crate::DataSectionReader<'a>),
/// A custom section was found.
CustomSection {
/// The name of the custom section.
name: &'a str,
/// The offset, relative to the start of the original module, that the
/// payload for this custom section starts at.
data_offset: usize,
/// The actual contents of the custom section.
data: &'a [u8],
},
/// Indicator of the start of the code section.
///
/// This entry is returned whenever the code section starts. The `count`
/// field indicates how many entries are in this code section. After
/// receiving this start marker you're guaranteed that the next `count`
/// items will be either `CodeSectionEntry` or an error will be returned.
///
/// This, unlike other sections, is intended to be used for streaming the
/// contents of the code section. The code section is not required to be
/// fully resident in memory when we parse it. Instead a [`Parser`] is
/// capable of parsing piece-by-piece of a code section.
CodeSectionStart {
/// The number of functions in this section.
count: u32,
/// The range of bytes that represent this section, specified in
/// offsets relative to the start of the byte stream.
range: Range,
/// The size, in bytes, of the remaining contents of this section.
///
/// This can be used in combination with [`Parser::skip_section`]
/// where the caller will know how many bytes to skip before feeding
/// bytes into `Parser` again.
size: u32,
},
/// An entry of the code section, a function, was parsed.
///
/// This entry indicates that a function was successfully received from the
/// code section, and the payload here is the window into the original input
/// where the function resides. Note that the function itself has not been
/// parsed, it's only been outlined. You'll need to process the
/// `FunctionBody` provided to test whether it parses and/or is valid.
CodeSectionEntry(crate::FunctionBody<'a>),
/// Indicator of the start of the module code section.
///
/// This behaves the same as the `CodeSectionStart` payload being returned.
/// You're guaranteed the next `count` items will be of type
/// `ModuleSectionEntry`.
ModuleSectionStart {
/// The number of inline modules in this section.
count: u32,
/// The range of bytes that represent this section, specified in
/// offsets relative to the start of the byte stream.
range: Range,
/// The size, in bytes, of the remaining contents of this section.
size: u32,
},
/// An entry of the module code section, a module, was parsed.
///
/// This variant is special in that it returns a sub-`Parser`. Upon
/// receiving a `ModuleSectionEntry` it is expected that the returned
/// `Parser` will be used instead of the parent `Parser` until the parse has
/// finished. You'll need to feed data into the `Parser` returned until it
/// returns `Payload::End`. After that you'll switch back to the parent
/// parser to resume parsing the rest of the module code section.
///
/// Note that binaries will not be parsed correctly if you feed the data for
/// a nested module into the parent [`Parser`].
ModuleSectionEntry {
/// The parser to use to parse the contents of the nested submodule.
/// This parser should be used until it reports `End`.
parser: Parser,
/// The range of bytes, relative to the start of the input stream, of
/// the bytes containing this submodule.
range: Range,
},
/// An unknown section was found.
///
/// This variant is returned for all unknown sections in a wasm file. This
/// likely wants to be interpreted as an error by consumers of the parser,
/// but this can also be used to parse sections unknown to wasmparser at
/// this time.
UnknownSection {
/// The 8-bit identifier for this section.
id: u8,
/// The contents of this section.
contents: &'a [u8],
/// The range of bytes, relative to the start of the original data
/// stream, that the contents of this section reside in.
range: Range,
},
/// The end of the WebAssembly module was reached.
End,
}
impl Parser {
/// Creates a new module parser.
///
/// Reports errors and ranges relative to `offset` provided, where `offset`
/// is some logical offset within the input stream that we're parsing.
pub fn new(offset: u64) -> Parser {
Parser {
state: State::ModuleHeader,
offset,
max_size: u64::max_value(),
}
}
/// Attempts to parse a chunk of data.
///
/// This method will attempt to parse the next incremental portion of a
/// WebAssembly binary. Data available for the module is provided as `data`,
/// and the data can be incomplete if more data has yet to arrive for the
/// module. The `eof` flag indicates whether `data` represents all possible
/// data for the module and no more data will ever be received.
///
/// There are two ways parsing can succeed with this method:
///
/// * `Chunk::NeedMoreData` - this indicates that there is not enough bytes
/// in `data` to parse a chunk of this module. The caller needs to wait
/// for more data to be available in this situation before calling this
/// method again. It is guaranteed that this is only returned if `eof` is
/// `false`.
///
/// * `Chunk::Parsed` - this indicates that a chunk of the input was
/// successfully parsed. The payload is available in this variant of what
/// was parsed, and this also indicates how many bytes of `data` was
/// consumed. It's expected that the caller will not provide these bytes
/// back to the [`Parser`] again.
///
/// Note that all `Chunk` return values are connected, with a lifetime, to
/// the input buffer. Each parsed chunk borrows the input buffer and is a
/// view into it for successfully parsed chunks.
///
/// It is expected that you'll call this method until `Payload::End` is
/// reached, at which point you're guaranteed that the module has completely
/// parsed. Note that complete parsing, for the top-level wasm module,
/// implies that `data` is empty and `eof` is `true`.
///
/// # Errors
///
/// Parse errors are returned as an `Err`. Errors can happen when the
/// structure of the module is unexpected, or if sections are too large for
/// example. Note that errors are not returned for malformed *contents* of
/// sections here. Sections are generally not individually parsed and each
/// returned [`Payload`] needs to be iterated over further to detect all
/// errors.
///
/// # Examples
///
/// An example of reading a wasm file from a stream (`std::io::Read`) and
/// incrementally parsing it.
///
/// ```
/// use std::io::Read;
/// use anyhow::Result;
/// use wasmparser::{Parser, Chunk, Payload::*};
///
/// fn parse(mut reader: impl Read) -> Result<()> {
/// let mut buf = Vec::new();
/// let mut parser = Parser::new(0);
/// let mut eof = false;
/// let mut stack = Vec::new();
///
/// loop {
/// let (payload, consumed) = match parser.parse(&buf, eof)? {
/// Chunk::NeedMoreData(hint) => {
/// assert!(!eof); // otherwise an error would be returned
///
/// // Use the hint to preallocate more space, then read
/// // some more data into our buffer.
/// //
/// // Note that the buffer management here is not ideal,
/// // but it's compact enough to fit in an example!
/// let len = buf.len();
/// buf.extend((0..hint).map(|_| 0u8));
/// let n = reader.read(&mut buf[len..])?;
/// buf.truncate(len + n);
/// eof = n == 0;
/// continue;
/// }
///
/// Chunk::Parsed { consumed, payload } => (payload, consumed),
/// };
///
/// match payload {
/// // Each of these would be handled individually as necessary
/// Version { .. } => { /* ... */ }
/// TypeSection(_) => { /* ... */ }
/// ImportSection(_) => { /* ... */ }
/// AliasSection(_) => { /* ... */ }
/// InstanceSection(_) => { /* ... */ }
/// FunctionSection(_) => { /* ... */ }
/// TableSection(_) => { /* ... */ }
/// MemorySection(_) => { /* ... */ }
/// EventSection(_) => { /* ... */ }
/// GlobalSection(_) => { /* ... */ }
/// ExportSection(_) => { /* ... */ }
/// StartSection { .. } => { /* ... */ }
/// ElementSection(_) => { /* ... */ }
/// DataCountSection { .. } => { /* ... */ }
/// DataSection(_) => { /* ... */ }
///
/// // Here we know how many functions we'll be receiving as
/// // `CodeSectionEntry`, so we can prepare for that, and
/// // afterwards we can parse and handle each function
/// // individually.
/// CodeSectionStart { .. } => { /* ... */ }
/// CodeSectionEntry(body) => {
/// // here we can iterate over `body` to parse the function
/// // and its locals
/// }
///
/// // When parsing nested modules we need to switch which
/// // `Parser` we're using.
/// ModuleSectionStart { .. } => { /* ... */ }
/// ModuleSectionEntry { parser: subparser, .. } => {
/// stack.push(parser);
/// parser = subparser;
/// }
///
/// CustomSection { name, .. } => { /* ... */ }
///
/// // most likely you'd return an error here
/// UnknownSection { id, .. } => { /* ... */ }
///
/// // Once we've reached the end of a module we either resume
/// // at the parent module or we break out of the loop because
/// // we're done.
/// End => {
/// if let Some(parent_parser) = stack.pop() {
/// parser = parent_parser;
/// } else {
/// break;
/// }
/// }
/// }
///
/// // once we're done processing the payload we can forget the
/// // original.
/// buf.drain(..consumed);
/// }
///
/// Ok(())
/// }
///
/// # parse(&b"\0asm\x01\0\0\0"[..]).unwrap();
/// ```
pub fn parse<'a>(&mut self, data: &'a [u8], eof: bool) -> Result<Chunk<'a>> {
let (data, eof) = if usize_to_u64(data.len()) > self.max_size {
(&data[..(self.max_size as usize)], true)
} else {
(data, eof)
};
// TODO: thread through `offset: u64` to `BinaryReader`, remove
// the cast here.
let mut reader = BinaryReader::new_with_offset(data, self.offset as usize);
match self.parse_reader(&mut reader, eof) {
Ok(payload) => {
// Be sure to update our offset with how far we got in the
// reader
self.offset += usize_to_u64(reader.position);
self.max_size -= usize_to_u64(reader.position);
Ok(Chunk::Parsed {
consumed: reader.position,
payload,
})
}
Err(e) => {
// If we're at EOF then there's no way we can recover from any
// error, so continue to propagate it.
if eof {
return Err(e);
}
// If our error doesn't look like it can be resolved with more
// data being pulled down, then propagate it, otherwise switch
// the error to "feed me please"
match e.inner.needed_hint {
Some(hint) => Ok(Chunk::NeedMoreData(usize_to_u64(hint))),
None => Err(e),
}
}
}
}
fn parse_reader<'a>(
&mut self,
reader: &mut BinaryReader<'a>,
eof: bool,
) -> Result<Payload<'a>> {
use Payload::*;
match self.state {
State::ModuleHeader => {
let start = reader.original_position();
let num = reader.read_file_header()?;
self.state = State::SectionStart;
Ok(Version {
num,
range: Range {
start,
end: reader.original_position(),
},
})
}
State::SectionStart => {
// If we're at eof and there are no bytes in our buffer, then
// that means we reached the end of the wasm file since it's
// just a bunch of sections concatenated after the module
// header.
if eof && reader.bytes_remaining() == 0 {
return Ok(Payload::End);
}
let id = reader.read_var_u7()? as u8;
let len_pos = reader.position;
let mut len = reader.read_var_u32()?;
// Test to make sure that this section actually fits within
// `Parser::max_size`. This doesn't matter for top-level modules
// but it is required for nested modules to correctly ensure
// that all sections live entirely within their section of the
// file.
let section_overflow = self
.max_size
.checked_sub(usize_to_u64(reader.position))
.and_then(|s| s.checked_sub(len.into()))
.is_none();
if section_overflow {
return Err(BinaryReaderError::new("section too large", len_pos));
}
match id {
0 => {
let mut content = subreader(reader, len)?;
// Note that if this fails we can't read any more bytes,
// so clear the "we'd succeed if we got this many more
// bytes" because we can't recover from "eof" at this point.
let name = content.read_string().map_err(clear_hint)?;
Ok(Payload::CustomSection {
name,
data_offset: content.original_position(),
data: content.remaining_buffer(),
})
}
1 => section(reader, len, TypeSectionReader::new, TypeSection),
2 => section(reader, len, ImportSectionReader::new, ImportSection),
3 => section(reader, len, FunctionSectionReader::new, FunctionSection),
4 => section(reader, len, TableSectionReader::new, TableSection),
5 => section(reader, len, MemorySectionReader::new, MemorySection),
6 => section(reader, len, GlobalSectionReader::new, GlobalSection),
7 => section(reader, len, ExportSectionReader::new, ExportSection),
8 => {
let (func, range) = single_u32(reader, len, "start")?;
Ok(StartSection { func, range })
}
9 => section(reader, len, ElementSectionReader::new, ElementSection),
10 => {
let start = reader.original_position();
let count = delimited(reader, &mut len, |r| r.read_var_u32())?;
let range = Range {
start,
end: reader.original_position() + len as usize,
};
self.state = State::FunctionBody {
remaining: count,
len,
};
Ok(CodeSectionStart {
count,
range,
size: len,
})
}
11 => section(reader, len, DataSectionReader::new, DataSection),
12 => {
let (count, range) = single_u32(reader, len, "data count")?;
Ok(DataCountSection { count, range })
}
13 => section(reader, len, EventSectionReader::new, EventSection),
14 => {
let start = reader.original_position();
let count = delimited(reader, &mut len, |r| r.read_var_u32())?;
let range = Range {
start,
end: reader.original_position() + len as usize,
};
self.state = State::Module {
remaining: count,
len,
};
Ok(ModuleSectionStart {
count,
range,
size: len,
})
}
15 => section(reader, len, InstanceSectionReader::new, InstanceSection),
16 => section(reader, len, AliasSectionReader::new, AliasSection),
id => {
let offset = reader.original_position();
let contents = reader.read_bytes(len as usize)?;
let range = Range {
start: offset,
end: offset + len as usize,
};
Ok(UnknownSection {
id,
contents,
range,
})
}
}
}
// Once we hit 0 remaining incrementally parsed items, with 0
// remaining bytes in each section, we're done and can switch back
// to parsing sections.
State::FunctionBody {
remaining: 0,
len: 0,
}
| State::Module {
remaining: 0,
len: 0,
} => {
self.state = State::SectionStart;
self.parse_reader(reader, eof)
}
// ... otherwise trailing bytes with no remaining entries in these
// sections indicates an error.
State::FunctionBody { remaining: 0, len } | State::Module { remaining: 0, len } => {
debug_assert!(len > 0);
let offset = reader.original_position();
Err(BinaryReaderError::new(
"trailing bytes at end of section",
offset,
))
}
// Functions are relatively easy to parse when we know there's at
// least one remaining and at least one byte available to read
// things.
//
// We use the remaining length try to read a u32 size of the
// function, and using that size we require the entire function be
// resident in memory. This means that we're reading whole chunks of
// functions at a time.
//
// Limiting via `Parser::max_size` (nested modules) happens above in
// `fn parse`, and limiting by our section size happens via
// `delimited`. Actual parsing of the function body is delegated to
// the caller to iterate over the `FunctionBody` structure.
State::FunctionBody { remaining, mut len } => {
let body = delimited(reader, &mut len, |r| {
let size = r.read_var_u32()?;
let offset = r.original_position();
Ok(FunctionBody::new(offset, r.read_bytes(size as usize)?))
})?;
self.state = State::FunctionBody {
remaining: remaining - 1,
len,
};
Ok(CodeSectionEntry(body))
}
// Modules are trickier than functions. What's going to happen here
// is that we'll be offloading parsing to a sub-`Parser`. This
// sub-`Parser` will be delimited to not read past the size of the
// module that's specified.
//
// So the first thing that happens here is we read the size of the
// module. We use `delimited` to make sure the bytes specifying the
// size of the module are themselves within the module code section.
//
// Once we've read the size of a module, however, there's a few
// pieces of state that we need to update. We as a parser will not
// receive the next `size` bytes, so we need to update our internal
// bookkeeping to account for that:
//
// * The `len`, number of bytes remaining in this section, is
// decremented by `size`. This can underflow, however, meaning
// that the size of the module doesn't fit within the section.
//
// * Our `Parser::max_size` field needs to account for the bytes
// that we're reading. Note that this is guaranteed to not
// underflow, however, because whenever we parse a section header
// we guarantee that its contents fit within our `max_size`.
//
// To update `len` we do that when updating `self.state`, and to
// update `max_size` we do that inline. Note that this will get
// further tweaked after we return with the bytes we read specifying
// the size of the module itself.
State::Module { remaining, mut len } => {
let size = delimited(reader, &mut len, |r| r.read_var_u32())?;
match len.checked_sub(size) {
Some(i) => len = i,
None => {
return Err(BinaryReaderError::new(
"Unexpected EOF",
reader.original_position(),
));
}
}
self.state = State::Module {
remaining: remaining - 1,
len,
};
let range = Range {
start: reader.original_position(),
end: reader.original_position() + size as usize,
};
self.max_size -= u64::from(size);
self.offset += u64::from(size);
let mut parser = Parser::new(usize_to_u64(reader.original_position()));
parser.max_size = size.into();
Ok(ModuleSectionEntry { parser, range })
}
}
}
/// Convenience function that can be used to parse a module entirely
/// resident in memory.
///
/// This function will parse the `data` provided as a WebAssembly module,
/// assuming that `data` represents the entire WebAssembly module.
///
/// Note that when this function yields `ModuleSectionEntry`
/// no action needs to be taken with the returned parser. The parser will be
/// automatically switched to internally and more payloads will continue to
/// get returned.
pub fn parse_all<'a>(
self,
mut data: &'a [u8],
) -> impl Iterator<Item = Result<Payload<'a>>> + 'a {
let mut stack = Vec::new();
let mut cur = self;
let mut done = false;
iter::from_fn(move || {
if done {
return None;
}
let payload = match cur.parse(data, true) {
// Propagate all errors
Err(e) => return Some(Err(e)),
// This isn't possible because `eof` is always true.
Ok(Chunk::NeedMoreData(_)) => unreachable!(),
Ok(Chunk::Parsed { payload, consumed }) => {
data = &data[consumed..];
payload
}
};
match &payload {
// If a module ends then we either finished the current
// module or, if there's a parent, we switch back to
// resuming parsing the parent.
Payload::End => match stack.pop() {
Some(p) => cur = p,
None => done = true,
},
// When we enter a nested module then we need to update our
// current parser, saving off the previous state.
//
// Afterwards we turn the loop again to recurse in parsing the
// nested module.
Payload::ModuleSectionEntry { parser, range: _ } => {
stack.push(cur.clone());
cur = parser.clone();
}
_ => {}
}
Some(Ok(payload))
})
}
/// Skip parsing the code or module code section entirely.
///
/// This function can be used to indicate, after receiving
/// `CodeSectionStart` or `ModuleSectionStart`, that the section
/// will not be parsed.
///
/// The caller will be responsible for skipping `size` bytes (found in the
/// `CodeSectionStart` or `ModuleSectionStart` payload). Bytes should
/// only be fed into `parse` after the `size` bytes have been skipped.
///
/// # Panics
///
/// This function will panic if the parser is not in a state where it's
/// parsing the code or module code section.
///
/// # Examples
///
/// ```
/// use wasmparser::{Result, Parser, Chunk, Range, SectionReader, Payload::*};
///
/// fn objdump_headers(mut wasm: &[u8]) -> Result<()> {
/// let mut parser = Parser::new(0);
/// loop {
/// let payload = match parser.parse(wasm, true)? {
/// Chunk::Parsed { consumed, payload } => {
/// wasm = &wasm[consumed..];
/// payload
/// }
/// // this state isn't possible with `eof = true`
/// Chunk::NeedMoreData(_) => unreachable!(),
/// };
/// match payload {
/// TypeSection(s) => print_range("type section", &s.range()),
/// ImportSection(s) => print_range("import section", &s.range()),
/// // .. other sections
///
/// // Print the range of the code section we see, but don't
/// // actually iterate over each individual function.
/// CodeSectionStart { range, size, .. } => {
/// print_range("code section", &range);
/// parser.skip_section();
/// wasm = &wasm[size as usize..];
/// }
/// End => break,
/// _ => {}
/// }
/// }
/// Ok(())
/// }
///
/// fn print_range(section: &str, range: &Range) {
/// println!("{:>40}: {:#010x} - {:#010x}", section, range.start, range.end);
/// }
/// ```
pub fn skip_section(&mut self) {
let skip = match self.state {
State::FunctionBody { remaining: _, len } | State::Module { remaining: _, len } => len,
_ => panic!("wrong state to call `skip_section`"),
};
self.offset += u64::from(skip);
self.max_size -= u64::from(skip);
self.state = State::SectionStart;
}
}
fn usize_to_u64(a: usize) -> u64 {
a.try_into().unwrap()
}
/// Parses an entire section resident in memory into a `Payload`.
///
/// Requires that `len` bytes are resident in `reader` and uses `ctor`/`variant`
/// to construct the section to return.
fn section<'a, T>(
reader: &mut BinaryReader<'a>,
len: u32,
ctor: fn(&'a [u8], usize) -> Result<T>,
variant: fn(T) -> Payload<'a>,
) -> Result<Payload<'a>> {
let offset = reader.original_position();
let payload = reader.read_bytes(len as usize)?;
// clear the hint for "need this many more bytes" here because we already
// read all the bytes, so it's not possible to read more bytes if this
// fails.
let reader = ctor(payload, offset).map_err(clear_hint)?;
Ok(variant(reader))
}
/// Creates a new `BinaryReader` from the given `reader` which will be reading
/// the first `len` bytes.
///
/// This means that `len` bytes must be resident in memory at the time of this
/// reading.
fn subreader<'a>(reader: &mut BinaryReader<'a>, len: u32) -> Result<BinaryReader<'a>> {
let offset = reader.original_position();
let payload = reader.read_bytes(len as usize)?;
Ok(BinaryReader::new_with_offset(payload, offset))
}
/// Reads a section that is represented by a single uleb-encoded `u32`.
fn single_u32<'a>(reader: &mut BinaryReader<'a>, len: u32, desc: &str) -> Result<(u32, Range)> {
let range = Range {
start: reader.original_position(),
end: reader.original_position() + len as usize,
};
let mut content = subreader(reader, len)?;
// We can't recover from "unexpected eof" here because our entire section is
// already resident in memory, so clear the hint for how many more bytes are
// expected.
let index = content.read_var_u32().map_err(clear_hint)?;
if !content.eof() {
return Err(BinaryReaderError::new(
format!("Unexpected content in the {} section", desc),
content.original_position(),
));
}
Ok((index, range))
}
/// Attempts to parse using `f`.
///
/// This will update `*len` with the number of bytes consumed, and it will cause
/// a failure to be returned instead of the number of bytes consumed exceeds
/// what `*len` currently is.
fn delimited<'a, T>(
reader: &mut BinaryReader<'a>,
len: &mut u32,
f: impl FnOnce(&mut BinaryReader<'a>) -> Result<T>,
) -> Result<T> {
let start = reader.position;
let ret = f(reader)?;
*len = match (reader.position - start)
.try_into()
.ok()
.and_then(|i| len.checked_sub(i))
{
Some(i) => i,
None => return Err(BinaryReaderError::new("Unexpected EOF", start)),
};
Ok(ret)
}
impl Default for Parser {
fn default() -> Parser {
Parser::new(0)
}
}
impl fmt::Debug for Payload<'_> {
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
use Payload::*;
match self {
CustomSection {
name,
data_offset,
data: _,
} => f
.debug_struct("CustomSection")
.field("name", name)
.field("data_offset", data_offset)
.field("data", &"...")
.finish(),
Version { num, range } => f
.debug_struct("Version")
.field("num", num)
.field("range", range)
.finish(),
TypeSection(_) => f.debug_tuple("TypeSection").field(&"...").finish(),
ImportSection(_) => f.debug_tuple("ImportSection").field(&"...").finish(),
AliasSection(_) => f.debug_tuple("AliasSection").field(&"...").finish(),
InstanceSection(_) => f.debug_tuple("InstanceSection").field(&"...").finish(),
FunctionSection(_) => f.debug_tuple("FunctionSection").field(&"...").finish(),
TableSection(_) => f.debug_tuple("TableSection").field(&"...").finish(),
MemorySection(_) => f.debug_tuple("MemorySection").field(&"...").finish(),
EventSection(_) => f.debug_tuple("EventSection").field(&"...").finish(),
GlobalSection(_) => f.debug_tuple("GlobalSection").field(&"...").finish(),
ExportSection(_) => f.debug_tuple("ExportSection").field(&"...").finish(),
ElementSection(_) => f.debug_tuple("ElementSection").field(&"...").finish(),
DataSection(_) => f.debug_tuple("DataSection").field(&"...").finish(),
StartSection { func, range } => f
.debug_struct("StartSection")
.field("func", func)
.field("range", range)
.finish(),
DataCountSection { count, range } => f
.debug_struct("DataCountSection")
.field("count", count)
.field("range", range)
.finish(),
CodeSectionStart { count, range, size } => f
.debug_struct("CodeSectionStart")
.field("count", count)
.field("range", range)
.field("size", size)
.finish(),
CodeSectionEntry(_) => f.debug_tuple("CodeSectionEntry").field(&"...").finish(),
ModuleSectionStart { count, range, size } => f
.debug_struct("ModuleSectionStart")
.field("count", count)
.field("range", range)
.field("size", size)
.finish(),
ModuleSectionEntry { parser: _, range } => f
.debug_struct("ModuleSectionEntry")
.field("range", range)
.finish(),
UnknownSection { id, range, .. } => f
.debug_struct("UnknownSection")
.field("id", id)
.field("range", range)
.finish(),
End => f.write_str("End"),
}
}
}
fn clear_hint(mut err: BinaryReaderError) -> BinaryReaderError {
err.inner.needed_hint = None;
err
}
#[cfg(test)]
mod tests {
use super::*;
macro_rules! assert_matches {
($a:expr, $b:pat $(,)?) => {
match $a {
$b => {}
a => panic!("`{:?}` doesn't match `{}`", a, stringify!($b)),
}
};
}
#[test]
fn header() {
assert!(Parser::default().parse(&[], true).is_err());
assert_matches!(
Parser::default().parse(&[], false),
Ok(Chunk::NeedMoreData(4)),
);
assert_matches!(
Parser::default().parse(b"\0", false),
Ok(Chunk::NeedMoreData(3)),
);
assert_matches!(
Parser::default().parse(b"\0asm", false),
Ok(Chunk::NeedMoreData(4)),
);
assert_matches!(
Parser::default().parse(b"\0asm\x01\0\0\0", false),
Ok(Chunk::Parsed {
consumed: 8,
payload: Payload::Version { num: 1, .. },
}),
);
}
fn parser_after_header() -> Parser {
let mut p = Parser::default();
assert_matches!(
p.parse(b"\0asm\x01\0\0\0", false),
Ok(Chunk::Parsed {
consumed: 8,
payload: Payload::Version { num: 1, .. },
}),
);
return p;
}
#[test]
fn start_section() {
assert_matches!(
parser_after_header().parse(&[], false),
Ok(Chunk::NeedMoreData(1)),
);
assert!(parser_after_header().parse(&[8], true).is_err());
assert!(parser_after_header().parse(&[8, 1], true).is_err());
assert!(parser_after_header().parse(&[8, 2], true).is_err());
assert_matches!(
parser_after_header().parse(&[8], false),
Ok(Chunk::NeedMoreData(1)),
);
assert_matches!(
parser_after_header().parse(&[8, 1], false),
Ok(Chunk::NeedMoreData(1)),
);
assert_matches!(
parser_after_header().parse(&[8, 2], false),
Ok(Chunk::NeedMoreData(2)),
);
assert_matches!(
parser_after_header().parse(&[8, 1, 1], false),
Ok(Chunk::Parsed {
consumed: 3,
payload: Payload::StartSection { func: 1, .. },
}),
);
assert!(parser_after_header().parse(&[8, 2, 1, 1], false).is_err());
assert!(parser_after_header().parse(&[8, 0], false).is_err());
}
#[test]
fn end_works() {
assert_matches!(
parser_after_header().parse(&[], true),
Ok(Chunk::Parsed {
consumed: 0,
payload: Payload::End,
}),
);
}
#[test]
fn type_section() {
assert!(parser_after_header().parse(&[1], true).is_err());
assert!(parser_after_header().parse(&[1, 0], false).is_err());
// assert!(parser_after_header().parse(&[8, 2], true).is_err());
assert_matches!(
parser_after_header().parse(&[1], false),
Ok(Chunk::NeedMoreData(1)),
);
assert_matches!(
parser_after_header().parse(&[1, 1], false),
Ok(Chunk::NeedMoreData(1)),
);
assert_matches!(
parser_after_header().parse(&[1, 1, 1], false),
Ok(Chunk::Parsed {
consumed: 3,
payload: Payload::TypeSection(_),
}),
);
assert_matches!(
parser_after_header().parse(&[1, 1, 1, 2, 3, 4], false),
Ok(Chunk::Parsed {
consumed: 3,
payload: Payload::TypeSection(_),
}),
);
}
#[test]
fn custom_section() {
assert!(parser_after_header().parse(&[0], true).is_err());
assert!(parser_after_header().parse(&[0, 0], false).is_err());
assert!(parser_after_header().parse(&[0, 1, 1], false).is_err());
assert_matches!(
parser_after_header().parse(&[0, 2, 1], false),
Ok(Chunk::NeedMoreData(1)),
);
assert_matches!(
parser_after_header().parse(&[0, 1, 0], false),
Ok(Chunk::Parsed {
consumed: 3,
payload: Payload::CustomSection {
name: "",
data_offset: 11,
data: b"",
},
}),
);
assert_matches!(
parser_after_header().parse(&[0, 2, 1, b'a'], false),
Ok(Chunk::Parsed {
consumed: 4,
payload: Payload::CustomSection {
name: "a",
data_offset: 12,
data: b"",
},
}),
);
assert_matches!(
parser_after_header().parse(&[0, 2, 0, b'a'], false),
Ok(Chunk::Parsed {
consumed: 4,
payload: Payload::CustomSection {
name: "",
data_offset: 11,
data: b"a",
},
}),
);
}
#[test]
fn function_section() {
assert!(parser_after_header().parse(&[10], true).is_err());
assert!(parser_after_header().parse(&[10, 0], true).is_err());
assert!(parser_after_header().parse(&[10, 1], true).is_err());
assert_matches!(
parser_after_header().parse(&[10], false),
Ok(Chunk::NeedMoreData(1))
);
assert_matches!(
parser_after_header().parse(&[10, 1], false),
Ok(Chunk::NeedMoreData(1))
);
let mut p = parser_after_header();
assert_matches!(
p.parse(&[10, 1, 0], false),
Ok(Chunk::Parsed {
consumed: 3,
payload: Payload::CodeSectionStart { count: 0, .. },
}),
);
assert_matches!(
p.parse(&[], true),
Ok(Chunk::Parsed {
consumed: 0,
payload: Payload::End,
}),
);
let mut p = parser_after_header();
assert_matches!(
p.parse(&[10, 2, 1, 0], false),
Ok(Chunk::Parsed {
consumed: 3,
payload: Payload::CodeSectionStart { count: 1, .. },
}),
);
assert_matches!(
p.parse(&[0], false),
Ok(Chunk::Parsed {
consumed: 1,
payload: Payload::CodeSectionEntry(_),
}),
);
assert_matches!(
p.parse(&[], true),
Ok(Chunk::Parsed {
consumed: 0,
payload: Payload::End,
}),
);
// 1 byte section with 1 function can't read the function body because
// the section is too small
let mut p = parser_after_header();
assert_matches!(
p.parse(&[10, 1, 1], false),
Ok(Chunk::Parsed {
consumed: 3,
payload: Payload::CodeSectionStart { count: 1, .. },
}),
);
assert_eq!(
p.parse(&[0], false).unwrap_err().message(),
"Unexpected EOF"
);
// section with 2 functions but section is cut off
let mut p = parser_after_header();
assert_matches!(
p.parse(&[10, 2, 2], false),
Ok(Chunk::Parsed {
consumed: 3,
payload: Payload::CodeSectionStart { count: 2, .. },
}),
);
assert_matches!(
p.parse(&[0], false),
Ok(Chunk::Parsed {
consumed: 1,
payload: Payload::CodeSectionEntry(_),
}),
);
assert_matches!(p.parse(&[], false), Ok(Chunk::NeedMoreData(1)));
assert_eq!(
p.parse(&[0], false).unwrap_err().message(),
"Unexpected EOF",
);
// trailing data is bad
let mut p = parser_after_header();
assert_matches!(
p.parse(&[10, 3, 1], false),
Ok(Chunk::Parsed {
consumed: 3,
payload: Payload::CodeSectionStart { count: 1, .. },
}),
);
assert_matches!(
p.parse(&[0], false),
Ok(Chunk::Parsed {
consumed: 1,
payload: Payload::CodeSectionEntry(_),
}),
);
assert_eq!(
p.parse(&[0], false).unwrap_err().message(),
"trailing bytes at end of section",
);
}
#[test]
fn module_code_errors() {
// no bytes to say size of section
assert!(parser_after_header().parse(&[14], true).is_err());
// section must start with a u32
assert!(parser_after_header().parse(&[14, 0], true).is_err());
// EOF before we finish reading the section
assert!(parser_after_header().parse(&[14, 1], true).is_err());
}
#[test]
fn module_code_one() {
let mut p = parser_after_header();
assert_matches!(p.parse(&[14], false), Ok(Chunk::NeedMoreData(1)));
assert_matches!(p.parse(&[14, 9], false), Ok(Chunk::NeedMoreData(1)));
// Module code section, 10 bytes large, one module.
assert_matches!(
p.parse(&[14, 10, 1], false),
Ok(Chunk::Parsed {
consumed: 3,
payload: Payload::ModuleSectionStart { count: 1, .. },
})
);
// Declare an empty module, which will be 8 bytes large for the header.
// Switch to the sub-parser on success.
let mut sub = match p.parse(&[8], false) {
Ok(Chunk::Parsed {
consumed: 1,
payload: Payload::ModuleSectionEntry { parser, .. },
}) => parser,
other => panic!("bad parse {:?}", other),
};
// Parse the header of the submodule with the sub-parser.
assert_matches!(sub.parse(&[], false), Ok(Chunk::NeedMoreData(4)));
assert_matches!(sub.parse(b"\0asm", false), Ok(Chunk::NeedMoreData(4)));
assert_matches!(
sub.parse(b"\0asm\x01\0\0\0", false),
Ok(Chunk::Parsed {
consumed: 8,
payload: Payload::Version { num: 1, .. },
}),
);
// The sub-parser should be byte-limited so the next byte shouldn't get
// consumed, it's intended for the parent parser.
assert_matches!(
sub.parse(&[10], false),
Ok(Chunk::Parsed {
consumed: 0,
payload: Payload::End,
}),
);
// The parent parser should now be back to resuming, and we simulate it
// being done with bytes to ensure that it's safely at the end,
// completing the module code section.
assert_matches!(p.parse(&[], false), Ok(Chunk::NeedMoreData(1)));
assert_matches!(
p.parse(&[], true),
Ok(Chunk::Parsed {
consumed: 0,
payload: Payload::End,
}),
);
}
#[test]
fn nested_section_too_big() {
let mut p = parser_after_header();
// Module code section, 12 bytes large, one module. This leaves 11 bytes
// of payload for the module definition itself.
assert_matches!(
p.parse(&[14, 12, 1], false),
Ok(Chunk::Parsed {
consumed: 3,
payload: Payload::ModuleSectionStart { count: 1, .. },
})
);
// Use one byte to say we're a 10 byte module, which fits exactly within
// our module code section.
let mut sub = match p.parse(&[10], false) {
Ok(Chunk::Parsed {
consumed: 1,
payload: Payload::ModuleSectionEntry { parser, .. },
}) => parser,
other => panic!("bad parse {:?}", other),
};
// use 8 bytes to parse the header, leaving 2 remaining bytes in our
// module.
assert_matches!(
sub.parse(b"\0asm\x01\0\0\0", false),
Ok(Chunk::Parsed {
consumed: 8,
payload: Payload::Version { num: 1, .. },
}),
);
// We can't parse a section which declares its bigger than the outer
// module. This is section 1, one byte big, with one content byte. The
// content byte, however, lives outside of the parent's module code
// section.
assert_eq!(
sub.parse(&[1, 1, 0], false).unwrap_err().message(),
"section too large",
);
}
}