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Merge pull request #168 from chenxiaolong/fec

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fec: Ensure FEC data size and grid size won't overflow
This commit is contained in:
Andrew Gunnerson
2023-09-28 19:18:33 -04:00
committed by GitHub
parent 525e2a409e ecb2caf47d
commit 4885e978ee
1 changed files with 18 additions and 5 deletions
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avbroot/src/format/fec.rs
+18 -5
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@@ -29,6 +29,8 @@ const FEC_HEADER_SIZE: usize = 60;
const FEC_MAGIC: u32 = 0xFECFECFE;
const FEC_VERSION: u32 = 0;
const FEC_MAX_BLOCK_SIZE: u32 = 16384;
#[derive(Debug, Error)]
pub enum Error {
#[error("FEC with parity byte count of {0} is not supported")]
@@ -61,8 +63,8 @@ pub enum Error {
InvalidHeaderFecSize { value: usize, available: usize },
#[error("Expected FEC digest {expected}, but have {actual}")]
InvalidFecDigest { expected: String, actual: String },
#[error("{0:?} field exceeds integer bounds")]
IntegerTooLarge(&'static str),
#[error("{0:?} field is out of bounds")]
FieldOutOfBounds(&'static str),
#[error("I/O error")]
Io(#[from] io::Error),
}
@@ -158,6 +160,8 @@ impl Fec {
input: file_size,
block: block_size,
});
} else if block_size > FEC_MAX_BLOCK_SIZE {
return Err(Error::FieldOutOfBounds("block_size"));
}
let rs_k = 255 - parity;
@@ -168,6 +172,15 @@ impl Fec {
let blocks = div_ceil(file_size, u64::from(block_size));
let rounds = div_ceil(blocks, u64::from(rs_k));
// Check upfront so we don't need to do checked multiplication later.
rounds.checked_mul(u64::from(parity))
.and_then(|s| s.checked_mul(u64::from(block_size)))
.and_then(|s| s.to_usize())
.ok_or_else(|| Error::FieldOutOfBounds("fec_data_size"))?;
rounds.checked_mul(u64::from(rs_k))
.and_then(|s| s.checked_mul(u64::from(block_size)))
.ok_or_else(|| Error::FieldOutOfBounds("fec_grid_size"))?;
Ok(Self {
file_size,
block_size,
@@ -588,7 +601,7 @@ impl FecImage {
.fec
.len()
.to_u32()
.ok_or_else(|| Error::IntegerTooLarge("fec_size"))?;
.ok_or_else(|| Error::FieldOutOfBounds("fec_size"))?;
let mut writer = Cursor::new([0u8; FEC_HEADER_SIZE]);
@@ -649,12 +662,12 @@ impl<R: Read> FromReader<R> for FecImage {
let parity = header_reader
.read_u32::<LittleEndian>()?
.to_u8()
.ok_or_else(|| Error::IntegerTooLarge("parity"))?;
.ok_or_else(|| Error::FieldOutOfBounds("parity"))?;
let fec_size = header_reader
.read_u32::<LittleEndian>()?
.to_usize()
.ok_or_else(|| Error::IntegerTooLarge("fec_size"))?;
.ok_or_else(|| Error::FieldOutOfBounds("fec_size"))?;
let actual_fec_size = fec.len() - FEC_BLOCK_SIZE;
if fec_size != actual_fec_size {
return Err(Error::InvalidHeaderFecSize {