Tidy up monero-serai as a meta crate

coins/monero/src/ringct.rs

@@ -0,0 +1,414 @@
+use core::ops::Deref;
+use std_shims::{
+  vec::Vec,
+  io::{self, Read, Write},
+};
+
+use zeroize::{Zeroize, Zeroizing};
+
+use curve25519_dalek::{constants::ED25519_BASEPOINT_TABLE, scalar::Scalar, edwards::EdwardsPoint};
+
+pub use monero_mlsag as mlsag;
+pub use monero_clsag as clsag;
+pub use monero_borromean as borromean;
+pub use monero_bulletproofs as bulletproofs;
+
+use crate::{
+  io::*,
+  generators::hash_to_point,
+  ringct::{mlsag::Mlsag, clsag::Clsag, borromean::BorromeanRange, bulletproofs::Bulletproof},
+  Protocol,
+};
+
+/// Generate a key image for a given key. Defined as `x * hash_to_point(xG)`.
+pub fn generate_key_image(secret: &Zeroizing<Scalar>) -> EdwardsPoint {
+  hash_to_point((ED25519_BASEPOINT_TABLE * secret.deref()).compress().to_bytes()) * secret.deref()
+}
+
+/// An encrypted amount.
+#[derive(Clone, PartialEq, Eq, Debug)]
+pub enum EncryptedAmount {
+  Original { mask: [u8; 32], amount: [u8; 32] },
+  Compact { amount: [u8; 8] },
+}
+
+impl EncryptedAmount {
+  /// Read an EncryptedAmount from a reader.
+  pub fn read<R: Read>(compact: bool, r: &mut R) -> io::Result<EncryptedAmount> {
+    Ok(if !compact {
+      EncryptedAmount::Original { mask: read_bytes(r)?, amount: read_bytes(r)? }
+    } else {
+      EncryptedAmount::Compact { amount: read_bytes(r)? }
+    })
+  }
+
+  /// Write the EncryptedAmount to a writer.
+  pub fn write<W: Write>(&self, w: &mut W) -> io::Result<()> {
+    match self {
+      EncryptedAmount::Original { mask, amount } => {
+        w.write_all(mask)?;
+        w.write_all(amount)
+      }
+      EncryptedAmount::Compact { amount } => w.write_all(amount),
+    }
+  }
+}
+
+/// The type of the RingCT data.
+#[derive(Clone, Copy, PartialEq, Eq, Debug, Zeroize)]
+pub enum RctType {
+  /// No RCT proofs.
+  Null,
+  /// One MLSAG for multiple inputs and Borromean range proofs (RCTTypeFull).
+  MlsagAggregate,
+  // One MLSAG for each input and a Borromean range proof (RCTTypeSimple).
+  MlsagIndividual,
+  // One MLSAG for each input and a Bulletproof (RCTTypeBulletproof).
+  Bulletproofs,
+  /// One MLSAG for each input and a Bulletproof, yet starting to use EncryptedAmount::Compact
+  /// (RCTTypeBulletproof2).
+  BulletproofsCompactAmount,
+  /// One CLSAG for each input and a Bulletproof (RCTTypeCLSAG).
+  Clsag,
+  /// One CLSAG for each input and a Bulletproof+ (RCTTypeBulletproofPlus).
+  BulletproofsPlus,
+}
+
+impl RctType {
+  /// Convert the RctType to its byte representation.
+  pub fn to_byte(self) -> u8 {
+    match self {
+      RctType::Null => 0,
+      RctType::MlsagAggregate => 1,
+      RctType::MlsagIndividual => 2,
+      RctType::Bulletproofs => 3,
+      RctType::BulletproofsCompactAmount => 4,
+      RctType::Clsag => 5,
+      RctType::BulletproofsPlus => 6,
+    }
+  }
+
+  /// Convert the RctType from its byte representation.
+  pub fn from_byte(byte: u8) -> Option<Self> {
+    Some(match byte {
+      0 => RctType::Null,
+      1 => RctType::MlsagAggregate,
+      2 => RctType::MlsagIndividual,
+      3 => RctType::Bulletproofs,
+      4 => RctType::BulletproofsCompactAmount,
+      5 => RctType::Clsag,
+      6 => RctType::BulletproofsPlus,
+      _ => None?,
+    })
+  }
+
+  /// Returns true if this RctType uses compact encrypted amounts, false otherwise.
+  pub fn compact_encrypted_amounts(&self) -> bool {
+    match self {
+      RctType::Null |
+      RctType::MlsagAggregate |
+      RctType::MlsagIndividual |
+      RctType::Bulletproofs => false,
+      RctType::BulletproofsCompactAmount | RctType::Clsag | RctType::BulletproofsPlus => true,
+    }
+  }
+}
+
+/// The base of the RingCT data.
+///
+/// This excludes all proofs (which once initially verified do not need to be kept around) and
+/// solely keeps data which either impacts the effects of the transactions or is needed to scan it.
+///
+/// The one exception for this is `pseudo_outs`, which was originally present here yet moved to
+/// RctPrunable in a later hard fork (causing it to be present in both).
+#[derive(Clone, PartialEq, Eq, Debug)]
+pub struct RctBase {
+  /// The fee used by this transaction.
+  pub fee: u64,
+  /// The re-randomized amount commitments used within inputs.
+  pub pseudo_outs: Vec<EdwardsPoint>,
+  /// The encrypted amounts for the recipient to decrypt.
+  pub encrypted_amounts: Vec<EncryptedAmount>,
+  /// The output commitments.
+  pub commitments: Vec<EdwardsPoint>,
+}
+
+impl RctBase {
+  pub(crate) fn fee_weight(outputs: usize, fee: u64) -> usize {
+    // 1 byte for the RCT signature type
+    1 + (outputs * (8 + 32)) + varint_len(fee)
+  }
+
+  /// Write the RctBase to a writer.
+  pub fn write<W: Write>(&self, w: &mut W, rct_type: RctType) -> io::Result<()> {
+    w.write_all(&[rct_type.to_byte()])?;
+    match rct_type {
+      RctType::Null => Ok(()),
+      _ => {
+        write_varint(&self.fee, w)?;
+        if rct_type == RctType::MlsagIndividual {
+          write_raw_vec(write_point, &self.pseudo_outs, w)?;
+        }
+        for encrypted_amount in &self.encrypted_amounts {
+          encrypted_amount.write(w)?;
+        }
+        write_raw_vec(write_point, &self.commitments, w)
+      }
+    }
+  }
+
+  /// Read a RctBase from a writer.
+  pub fn read<R: Read>(inputs: usize, outputs: usize, r: &mut R) -> io::Result<(RctBase, RctType)> {
+    let rct_type =
+      RctType::from_byte(read_byte(r)?).ok_or_else(|| io::Error::other("invalid RCT type"))?;
+
+    match rct_type {
+      RctType::Null | RctType::MlsagAggregate | RctType::MlsagIndividual => {}
+      RctType::Bulletproofs |
+      RctType::BulletproofsCompactAmount |
+      RctType::Clsag |
+      RctType::BulletproofsPlus => {
+        if outputs == 0 {
+          // Because the Bulletproofs(+) layout must be canonical, there must be 1 Bulletproof if
+          // Bulletproofs are in use
+          // If there are Bulletproofs, there must be a matching amount of outputs, implicitly
+          // banning 0 outputs
+          // Since HF 12 (CLSAG being 13), a 2-output minimum has also been enforced
+          Err(io::Error::other("RCT with Bulletproofs(+) had 0 outputs"))?;
+        }
+      }
+    }
+
+    Ok((
+      if rct_type == RctType::Null {
+        RctBase { fee: 0, pseudo_outs: vec![], encrypted_amounts: vec![], commitments: vec![] }
+      } else {
+        RctBase {
+          fee: read_varint(r)?,
+          // Only read pseudo_outs if they have yet to be moved to RctPrunable
+          // TODO: Shouldn't this be any Mlsag*?
+          pseudo_outs: if rct_type == RctType::MlsagIndividual {
+            read_raw_vec(read_point, inputs, r)?
+          } else {
+            vec![]
+          },
+          encrypted_amounts: (0 .. outputs)
+            .map(|_| EncryptedAmount::read(rct_type.compact_encrypted_amounts(), r))
+            .collect::<Result<_, _>>()?,
+          commitments: read_raw_vec(read_point, outputs, r)?,
+        }
+      },
+      rct_type,
+    ))
+  }
+}
+
+#[derive(Clone, PartialEq, Eq, Debug)]
+pub enum RctPrunable {
+  Null,
+  AggregateMlsagBorromean {
+    borromean: Vec<BorromeanRange>,
+    mlsag: Mlsag,
+  },
+  MlsagBorromean {
+    borromean: Vec<BorromeanRange>,
+    mlsags: Vec<Mlsag>,
+  },
+  MlsagBulletproofs {
+    bulletproofs: Bulletproof,
+    mlsags: Vec<Mlsag>,
+    pseudo_outs: Vec<EdwardsPoint>,
+  },
+  Clsag {
+    bulletproofs: Bulletproof,
+    clsags: Vec<Clsag>,
+    pseudo_outs: Vec<EdwardsPoint>,
+  },
+}
+
+impl RctPrunable {
+  pub(crate) fn fee_weight(protocol: Protocol, inputs: usize, outputs: usize) -> usize {
+    // 1 byte for number of BPs (technically a VarInt, yet there's always just zero or one)
+    1 + Bulletproof::fee_weight(protocol.bp_plus(), outputs) +
+      (inputs * (Clsag::fee_weight(protocol.ring_len()) + 32))
+  }
+
+  pub fn write<W: Write>(&self, w: &mut W, rct_type: RctType) -> io::Result<()> {
+    match self {
+      RctPrunable::Null => Ok(()),
+      RctPrunable::AggregateMlsagBorromean { borromean, mlsag } => {
+        write_raw_vec(BorromeanRange::write, borromean, w)?;
+        mlsag.write(w)
+      }
+      RctPrunable::MlsagBorromean { borromean, mlsags } => {
+        write_raw_vec(BorromeanRange::write, borromean, w)?;
+        write_raw_vec(Mlsag::write, mlsags, w)
+      }
+      RctPrunable::MlsagBulletproofs { bulletproofs, mlsags, pseudo_outs } => {
+        if rct_type == RctType::Bulletproofs {
+          w.write_all(&1u32.to_le_bytes())?;
+        } else {
+          w.write_all(&[1])?;
+        }
+        bulletproofs.write(w)?;
+
+        write_raw_vec(Mlsag::write, mlsags, w)?;
+        write_raw_vec(write_point, pseudo_outs, w)
+      }
+      RctPrunable::Clsag { bulletproofs, clsags, pseudo_outs } => {
+        w.write_all(&[1])?;
+        bulletproofs.write(w)?;
+
+        write_raw_vec(Clsag::write, clsags, w)?;
+        write_raw_vec(write_point, pseudo_outs, w)
+      }
+    }
+  }
+
+  pub fn serialize(&self, rct_type: RctType) -> Vec<u8> {
+    let mut serialized = vec![];
+    self.write(&mut serialized, rct_type).unwrap();
+    serialized
+  }
+
+  pub fn read<R: Read>(
+    rct_type: RctType,
+    ring_length: usize,
+    inputs: usize,
+    outputs: usize,
+    r: &mut R,
+  ) -> io::Result<RctPrunable> {
+    // While we generally don't bother with misc consensus checks, this affects the safety of
+    // the below defined rct_type function
+    // The exact line preventing zero-input transactions is:
+    // https://github.com/monero-project/monero/blob/00fd416a99686f0956361d1cd0337fe56e58d4a7/
+    //   src/ringct/rctSigs.cpp#L609
+    // And then for RctNull, that's only allowed for miner TXs which require one input of
+    // Input::Gen
+    if inputs == 0 {
+      Err(io::Error::other("transaction had no inputs"))?;
+    }
+
+    Ok(match rct_type {
+      RctType::Null => RctPrunable::Null,
+      RctType::MlsagAggregate => RctPrunable::AggregateMlsagBorromean {
+        borromean: read_raw_vec(BorromeanRange::read, outputs, r)?,
+        mlsag: Mlsag::read(ring_length, inputs + 1, r)?,
+      },
+      RctType::MlsagIndividual => RctPrunable::MlsagBorromean {
+        borromean: read_raw_vec(BorromeanRange::read, outputs, r)?,
+        mlsags: (0 .. inputs).map(|_| Mlsag::read(ring_length, 2, r)).collect::<Result<_, _>>()?,
+      },
+      RctType::Bulletproofs | RctType::BulletproofsCompactAmount => {
+        RctPrunable::MlsagBulletproofs {
+          bulletproofs: {
+            if (if rct_type == RctType::Bulletproofs {
+              u64::from(read_u32(r)?)
+            } else {
+              read_varint(r)?
+            }) != 1
+            {
+              Err(io::Error::other("n bulletproofs instead of one"))?;
+            }
+            Bulletproof::read(r)?
+          },
+          mlsags: (0 .. inputs)
+            .map(|_| Mlsag::read(ring_length, 2, r))
+            .collect::<Result<_, _>>()?,
+          pseudo_outs: read_raw_vec(read_point, inputs, r)?,
+        }
+      }
+      RctType::Clsag | RctType::BulletproofsPlus => RctPrunable::Clsag {
+        bulletproofs: {
+          if read_varint::<_, u64>(r)? != 1 {
+            Err(io::Error::other("n bulletproofs instead of one"))?;
+          }
+          (if rct_type == RctType::Clsag { Bulletproof::read } else { Bulletproof::read_plus })(r)?
+        },
+        clsags: (0 .. inputs).map(|_| Clsag::read(ring_length, r)).collect::<Result<_, _>>()?,
+        pseudo_outs: read_raw_vec(read_point, inputs, r)?,
+      },
+    })
+  }
+
+  pub(crate) fn signature_write<W: Write>(&self, w: &mut W) -> io::Result<()> {
+    match self {
+      RctPrunable::Null => panic!("Serializing RctPrunable::Null for a signature"),
+      RctPrunable::AggregateMlsagBorromean { borromean, .. } |
+      RctPrunable::MlsagBorromean { borromean, .. } => {
+        borromean.iter().try_for_each(|rs| rs.write(w))
+      }
+      RctPrunable::MlsagBulletproofs { bulletproofs, .. } |
+      RctPrunable::Clsag { bulletproofs, .. } => bulletproofs.signature_write(w),
+    }
+  }
+}
+
+#[derive(Clone, PartialEq, Eq, Debug)]
+pub struct RctSignatures {
+  pub base: RctBase,
+  pub prunable: RctPrunable,
+}
+
+impl RctSignatures {
+  /// RctType for a given RctSignatures struct.
+  pub fn rct_type(&self) -> RctType {
+    match &self.prunable {
+      RctPrunable::Null => RctType::Null,
+      RctPrunable::AggregateMlsagBorromean { .. } => RctType::MlsagAggregate,
+      RctPrunable::MlsagBorromean { .. } => RctType::MlsagIndividual,
+      // RctBase ensures there's at least one output, making the following
+      // inferences guaranteed/expects impossible on any valid RctSignatures
+      RctPrunable::MlsagBulletproofs { .. } => {
+        if matches!(
+          self
+            .base
+            .encrypted_amounts
+            .first()
+            .expect("MLSAG with Bulletproofs didn't have any outputs"),
+          EncryptedAmount::Original { .. }
+        ) {
+          RctType::Bulletproofs
+        } else {
+          RctType::BulletproofsCompactAmount
+        }
+      }
+      RctPrunable::Clsag { bulletproofs, .. } => {
+        if matches!(bulletproofs, Bulletproof::Original { .. }) {
+          RctType::Clsag
+        } else {
+          RctType::BulletproofsPlus
+        }
+      }
+    }
+  }
+
+  pub(crate) fn fee_weight(protocol: Protocol, inputs: usize, outputs: usize, fee: u64) -> usize {
+    RctBase::fee_weight(outputs, fee) + RctPrunable::fee_weight(protocol, inputs, outputs)
+  }
+
+  pub fn write<W: Write>(&self, w: &mut W) -> io::Result<()> {
+    let rct_type = self.rct_type();
+    self.base.write(w, rct_type)?;
+    self.prunable.write(w, rct_type)
+  }
+
+  pub fn serialize(&self) -> Vec<u8> {
+    let mut serialized = vec![];
+    self.write(&mut serialized).unwrap();
+    serialized
+  }
+
+  pub fn read<R: Read>(
+    ring_length: usize,
+    inputs: usize,
+    outputs: usize,
+    r: &mut R,
+  ) -> io::Result<RctSignatures> {
+    let base = RctBase::read(inputs, outputs, r)?;
+    Ok(RctSignatures {
+      base: base.0,
+      prunable: RctPrunable::read(base.1, ring_length, inputs, outputs, r)?,
+    })
+  }
+}