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bdk_wallet: Don't reimplement descriptor checksum, use the one from rust-miniscript #1523

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Merged
evanlinjin merged 3 commits into from
Aug 5, 2024
Merged

bdk_wallet: Don't reimplement descriptor checksum, use the one from rust-miniscript #1523

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a11ace2
bdk_wallet: descriptor: remove unnecessary call to calc_checksum_bytes
darosior Jul 25, 2024
8245fb7
bdk_wallet: don't reimplement checksum algorithm, use rust-miniscript
darosior Jul 25, 2024
70c7d6b
bdk_wallet: remove unnecessary calls to calc_checksum
darosior Jul 25, 2024
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82 changes: 10 additions & 72 deletions crates/wallet/src/descriptor/checksum.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -17,82 +17,20 @@
use crate::descriptor::DescriptorError;
use alloc::string::String;

const INPUT_CHARSET: &[u8] = b"0123456789()[],'/*abcdefgh@:$%{}IJKLMNOPQRSTUVWXYZ&+-.;<=>?!^_|~ijklmnopqrstuvwxyzABCDEFGH`#\"\\ ";
const CHECKSUM_CHARSET: &[u8] = b"qpzry9x8gf2tvdw0s3jn54khce6mua7l";
use miniscript::descriptor::checksum::desc_checksum;

fn poly_mod(mut c: u64, val: u64) -> u64 {
let c0 = c >> 35;
c = ((c & 0x7ffffffff) << 5) ^ val;
if c0 & 1 > 0 {
c ^= 0xf5dee51989
};
if c0 & 2 > 0 {
c ^= 0xa9fdca3312
};
if c0 & 4 > 0 {
c ^= 0x1bab10e32d
};
if c0 & 8 > 0 {
c ^= 0x3706b1677a
};
if c0 & 16 > 0 {
c ^= 0x644d626ffd
};

c
}

/// Compute the checksum bytes of a descriptor, excludes any existing checksum in the descriptor string from the calculation
pub fn calc_checksum_bytes(mut desc: &str) -> Result<[u8; 8], DescriptorError> {
let mut c = 1;
let mut cls = 0;
let mut clscount = 0;

let mut original_checksum = None;
/// Compute the checksum of a descriptor, excludes any existing checksum in the descriptor string from the calculation
pub fn calc_checksum(desc: &str) -> Result<String, DescriptorError> {
if let Some(split) = desc.split_once('#') {
desc = split.0;
original_checksum = Some(split.1);
}

for ch in desc.as_bytes() {
let pos = INPUT_CHARSET
.iter()
.position(|b| b == ch)
.ok_or(DescriptorError::InvalidDescriptorCharacter(*ch))? as u64;
c = poly_mod(c, pos & 31);
cls = cls * 3 + (pos >> 5);
clscount += 1;
if clscount == 3 {
c = poly_mod(c, cls);
cls = 0;
clscount = 0;
}
}
if clscount > 0 {
c = poly_mod(c, cls);
}
(0..8).for_each(|_| c = poly_mod(c, 0));
c ^= 1;

let mut checksum = [0_u8; 8];
for j in 0..8 {
checksum[j] = CHECKSUM_CHARSET[((c >> (5 * (7 - j))) & 31) as usize];
}

// if input data already had a checksum, check calculated checksum against original checksum
if let Some(original_checksum) = original_checksum {
if original_checksum.as_bytes() != checksum {
let og_checksum = split.1;
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@evanlinjin evanlinjin Aug 5, 2024

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Who is the original gansta we are referring to here? 😆

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@darosior darosior Aug 5, 2024

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Haha, i meant "original" of course. :)

let checksum = desc_checksum(split.0)?;
if og_checksum != checksum {
return Err(DescriptorError::InvalidDescriptorChecksum);
}
Ok(checksum)
} else {
Ok(desc_checksum(desc)?)
}

Ok(checksum)
}

/// Compute the checksum of a descriptor, excludes any existing checksum in the descriptor string from the calculation
pub fn calc_checksum(desc: &str) -> Result<String, DescriptorError> {
// unsafe is okay here as the checksum only uses bytes in `CHECKSUM_CHARSET`
calc_checksum_bytes(desc).map(|b| unsafe { String::from_utf8_unchecked(b.to_vec()) })
}

#[cfg(test)]
Expand Down Expand Up @@ -141,7 +79,7 @@ mod test {

assert_matches!(
calc_checksum(&invalid_desc),
Err(DescriptorError::InvalidDescriptorCharacter(invalid_char)) if invalid_char == sparkle_heart.as_bytes()[0]
Err(DescriptorError::Miniscript(miniscript::Error::BadDescriptor(e))) if e == format!("Invalid character in checksum: '{}'", sparkle_heart)
);
}
}
5 changes: 2 additions & 3 deletions crates/wallet/src/descriptor/mod.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -42,7 +42,6 @@ pub mod policy;
pub mod template;

pub use self::checksum::calc_checksum;
use self::checksum::calc_checksum_bytes;
pub use self::error::Error as DescriptorError;
pub use self::policy::Policy;
use self::template::DescriptorTemplateOut;
Expand Down Expand Up @@ -88,8 +87,8 @@ impl IntoWalletDescriptor for &str {
) -> Result<(ExtendedDescriptor, KeyMap), DescriptorError> {
let descriptor = match self.split_once('#') {
Some((desc, original_checksum)) => {
let checksum = calc_checksum_bytes(desc)?;
if original_checksum.as_bytes() != checksum {
let checksum = calc_checksum(desc)?;
if original_checksum != checksum {
return Err(DescriptorError::InvalidDescriptorChecksum);
}
desc
Expand Down
8 changes: 3 additions & 5 deletions crates/wallet/src/wallet/mod.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -79,7 +79,7 @@ use utils::{check_nsequence_rbf, After, Older, SecpCtx};

use crate::descriptor::policy::BuildSatisfaction;
use crate::descriptor::{
self, calc_checksum, DerivedDescriptor, DescriptorMeta, ExtendedDescriptor, ExtractPolicy,
self, DerivedDescriptor, DescriptorMeta, ExtendedDescriptor, ExtractPolicy,
IntoWalletDescriptor, Policy, XKeyUtils,
};
use crate::psbt::PsbtUtils;
Expand Down Expand Up @@ -2360,15 +2360,13 @@ where
.into_wallet_descriptor(secp, network)?
.0
.to_string();
let mut wallet_name = calc_checksum(&descriptor[..descriptor.find('#').unwrap()])?;
let mut wallet_name = descriptor.split_once('#').unwrap().1.to_string();
if let Some(change_descriptor) = change_descriptor {
let change_descriptor = change_descriptor
.into_wallet_descriptor(secp, network)?
.0
.to_string();
wallet_name.push_str(
calc_checksum(&change_descriptor[..change_descriptor.find('#').unwrap()])?.as_str(),
);
wallet_name.push_str(change_descriptor.split_once('#').unwrap().1);
}

Ok(wallet_name)
Expand Down