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

Jump to bottom

const-oid: fix large arc handling in encoder #1522

Merged
merged 2 commits into from
Sep 18, 2024
Merged

const-oid: fix large arc handling in encoder #1522

Show file tree
Hide file tree
Changes from all commits
Commits
Show all changes
2 commits
Select commit Hold shift + click to select a range
30d3852
const-oid: fix large arc handling in encoder
tarcieri Sep 18, 2024
7dcedc8
clippy
tarcieri Sep 18, 2024
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
73 changes: 37 additions & 36 deletions const-oid/src/encoder.rs
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -73,27 +73,9 @@ impl<const MAX_SIZE: usize> Encoder<MAX_SIZE> {
self.cursor = 1;
Ok(self)
}
// TODO(tarcieri): finer-grained overflow safety / checked arithmetic
#[allow(clippy::arithmetic_side_effects)]
State::Body => {
// Total number of bytes in encoded arc - 1
let nbytes = base128_len(arc);

// Shouldn't overflow on any 16-bit+ architectures
if self.cursor + nbytes + 1 > MAX_SIZE {
return Err(Error::Length);
}

let new_cursor = self.cursor + nbytes + 1;

// TODO(tarcieri): use `?` when stable in `const fn`
match self.encode_base128_byte(arc, nbytes, false) {
Ok(mut encoder) => {
encoder.cursor = new_cursor;
Ok(encoder)
}
Err(err) => Err(err),
}
self.encode_base128(arc, nbytes)
}
}
}
Expand All @@ -113,23 +95,19 @@ impl<const MAX_SIZE: usize> Encoder<MAX_SIZE> {
}

/// Encode a single byte of a Base 128 value.
const fn encode_base128_byte(mut self, mut n: u32, i: usize, continued: bool) -> Result<Self> {
let mask = if continued { 0b10000000 } else { 0 };

// Underflow checked by branch
#[allow(clippy::arithmetic_side_effects)]
if n > 0x80 {
self.bytes[checked_add!(self.cursor, i)] = (n & 0b1111111) as u8 | mask;
n >>= 7;

if i > 0 {
self.encode_base128_byte(n, i.saturating_sub(1), true)
} else {
Err(Error::Base128)
}
} else {
self.bytes[self.cursor] = n as u8 | mask;
Ok(self)
const fn encode_base128(mut self, n: u32, remaining_len: usize) -> Result<Self> {
if self.cursor >= MAX_SIZE {
return Err(Error::Length);
}

let mask = if remaining_len > 0 { 0b10000000 } else { 0 };
let (hi, lo) = split_high_bits(n);
self.bytes[self.cursor] = hi | mask;
self.cursor = checked_add!(self.cursor, 1);

match remaining_len.checked_sub(1) {
Some(len) => self.encode_base128(lo, len),
None => Ok(self),
}
}
}
Expand All @@ -145,6 +123,29 @@ const fn base128_len(arc: Arc) -> usize {
}
}

/// Split the highest 7-bits of an [`Arc`] from the rest of an arc.
///
/// Returns: `(hi, lo)`
// TODO(tarcieri): always use checked arithmetic
#[allow(clippy::arithmetic_side_effects)]
const fn split_high_bits(arc: Arc) -> (u8, Arc) {
if arc < 0x80 {
return (arc as u8, 0);
}

let hi_bit = 32 - arc.leading_zeros();
let hi_bit_mod7 = hi_bit % 7;
let upper_bit_pos = hi_bit
- if hi_bit > 0 && hi_bit_mod7 == 0 {
7
} else {
hi_bit_mod7
};
let upper_bits = arc >> upper_bit_pos;
let lower_bits = arc ^ (upper_bits << upper_bit_pos);
(upper_bits as u8, lower_bits)
}

#[cfg(test)]
#[allow(clippy::unwrap_used)]
mod tests {
Expand Down
73 changes: 50 additions & 23 deletions const-oid/tests/oid.rs
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -23,10 +23,16 @@ const EXAMPLE_OID_2_BER: &[u8] = &hex!("60864801650304012A");
const EXAMPLE_OID_2: ObjectIdentifier = ObjectIdentifier::new_unwrap(EXAMPLE_OID_2_STR);

/// Example OID value with a large arc
const EXAMPLE_OID_LARGE_ARC_STR: &str = "0.9.2342.19200300.100.1.1";
const EXAMPLE_OID_LARGE_ARC_BER: &[u8] = &hex!("0992268993F22C640101");
const EXAMPLE_OID_LARGE_ARC: ObjectIdentifier =
ObjectIdentifier::new_unwrap("0.9.2342.19200300.100.1.1");
const EXAMPLE_OID_LARGE_ARC_0_STR: &str = "1.2.16384";
const EXAMPLE_OID_LARGE_ARC_0_BER: &[u8] = &hex!("2A818000");
const EXAMPLE_OID_LARGE_ARC_0: ObjectIdentifier =
ObjectIdentifier::new_unwrap(crate::EXAMPLE_OID_LARGE_ARC_0_STR);

/// Example OID value with a large arc
const EXAMPLE_OID_LARGE_ARC_1_STR: &str = "0.9.2342.19200300.100.1.1";
const EXAMPLE_OID_LARGE_ARC_1_BER: &[u8] = &hex!("0992268993F22C640101");
const EXAMPLE_OID_LARGE_ARC_1: ObjectIdentifier =
ObjectIdentifier::new_unwrap(EXAMPLE_OID_LARGE_ARC_1_STR);

/// Create an OID from a string.
pub fn oid(s: &str) -> ObjectIdentifier {
Expand All @@ -38,27 +44,37 @@ fn from_bytes() {
let oid0 = ObjectIdentifier::from_bytes(EXAMPLE_OID_0_BER).unwrap();
assert_eq!(oid0.arc(0).unwrap(), 0);
assert_eq!(oid0.arc(1).unwrap(), 9);
assert_eq!(oid0.arc(2).unwrap(), 2342);
assert_eq!(oid0, EXAMPLE_OID_0);

let oid1 = ObjectIdentifier::from_bytes(EXAMPLE_OID_1_BER).unwrap();
assert_eq!(oid1.arc(0).unwrap(), 1);
assert_eq!(oid1.arc(1).unwrap(), 2);
assert_eq!(oid1.arc(2).unwrap(), 840);
assert_eq!(oid1, EXAMPLE_OID_1);

let oid2 = ObjectIdentifier::from_bytes(EXAMPLE_OID_2_BER).unwrap();
assert_eq!(oid2.arc(0).unwrap(), 2);
assert_eq!(oid2.arc(1).unwrap(), 16);
assert_eq!(oid2.arc(2).unwrap(), 840);
assert_eq!(oid2, EXAMPLE_OID_2);

let oid3 = ObjectIdentifier::from_bytes(EXAMPLE_OID_LARGE_ARC_BER).unwrap();
assert_eq!(oid3.arc(0).unwrap(), 0);
assert_eq!(oid3.arc(1).unwrap(), 9);
assert_eq!(oid3.arc(2).unwrap(), 2342);
assert_eq!(oid3.arc(3).unwrap(), 19200300);
assert_eq!(oid3.arc(4).unwrap(), 100);
assert_eq!(oid3.arc(5).unwrap(), 1);
assert_eq!(oid3.arc(6).unwrap(), 1);
assert_eq!(oid3, EXAMPLE_OID_LARGE_ARC);
let oid_largearc0 = ObjectIdentifier::from_bytes(EXAMPLE_OID_LARGE_ARC_0_BER).unwrap();
assert_eq!(oid_largearc0.arc(0).unwrap(), 1);
assert_eq!(oid_largearc0.arc(1).unwrap(), 2);
assert_eq!(oid_largearc0.arc(2).unwrap(), 16384);
assert_eq!(oid_largearc0.arc(3), None);
assert_eq!(oid_largearc0, EXAMPLE_OID_LARGE_ARC_0);

let oid_largearc1 = ObjectIdentifier::from_bytes(EXAMPLE_OID_LARGE_ARC_1_BER).unwrap();
assert_eq!(oid_largearc1.arc(0).unwrap(), 0);
assert_eq!(oid_largearc1.arc(1).unwrap(), 9);
assert_eq!(oid_largearc1.arc(2).unwrap(), 2342);
assert_eq!(oid_largearc1.arc(3).unwrap(), 19200300);
assert_eq!(oid_largearc1.arc(4).unwrap(), 100);
assert_eq!(oid_largearc1.arc(5).unwrap(), 1);
assert_eq!(oid_largearc1.arc(6).unwrap(), 1);
assert_eq!(oid_largearc1, EXAMPLE_OID_LARGE_ARC_1);

// Empty
assert_eq!(ObjectIdentifier::from_bytes(&[]), Err(Error::Empty));
Expand All @@ -81,17 +97,25 @@ fn from_str() {
assert_eq!(oid2.arc(1).unwrap(), 16);
assert_eq!(oid2, EXAMPLE_OID_2);

let oid3 = EXAMPLE_OID_LARGE_ARC_STR
let oid_largearc0 = EXAMPLE_OID_LARGE_ARC_0_STR
.parse::<ObjectIdentifier>()
.unwrap();
assert_eq!(oid3.arc(0).unwrap(), 0);
assert_eq!(oid3.arc(1).unwrap(), 9);
assert_eq!(oid3.arc(2).unwrap(), 2342);
assert_eq!(oid3.arc(3).unwrap(), 19200300);
assert_eq!(oid3.arc(4).unwrap(), 100);
assert_eq!(oid3.arc(5).unwrap(), 1);
assert_eq!(oid3.arc(6).unwrap(), 1);
assert_eq!(oid3, EXAMPLE_OID_LARGE_ARC);
assert_eq!(oid_largearc0.arc(0).unwrap(), 1);
assert_eq!(oid_largearc0.arc(1).unwrap(), 2);
assert_eq!(oid_largearc0.arc(2).unwrap(), 16384);
assert_eq!(oid_largearc0, EXAMPLE_OID_LARGE_ARC_0);

let oid_largearc1 = EXAMPLE_OID_LARGE_ARC_1_STR
.parse::<ObjectIdentifier>()
.unwrap();
assert_eq!(oid_largearc1.arc(0).unwrap(), 0);
assert_eq!(oid_largearc1.arc(1).unwrap(), 9);
assert_eq!(oid_largearc1.arc(2).unwrap(), 2342);
assert_eq!(oid_largearc1.arc(3).unwrap(), 19200300);
assert_eq!(oid_largearc1.arc(4).unwrap(), 100);
assert_eq!(oid_largearc1.arc(5).unwrap(), 1);
assert_eq!(oid_largearc1.arc(6).unwrap(), 1);
assert_eq!(oid_largearc1, EXAMPLE_OID_LARGE_ARC_1);

// Truncated
assert_eq!(
Expand All @@ -117,7 +141,10 @@ fn display() {
assert_eq!(EXAMPLE_OID_0.to_string(), EXAMPLE_OID_0_STR);
assert_eq!(EXAMPLE_OID_1.to_string(), EXAMPLE_OID_1_STR);
assert_eq!(EXAMPLE_OID_2.to_string(), EXAMPLE_OID_2_STR);
assert_eq!(EXAMPLE_OID_LARGE_ARC.to_string(), EXAMPLE_OID_LARGE_ARC_STR);
assert_eq!(
EXAMPLE_OID_LARGE_ARC_1.to_string(),
EXAMPLE_OID_LARGE_ARC_1_STR
);
}

#[test]
Expand Down
Loading