Add ProofReader and auth/lock and overflow edge case checks (#6651)

include/xrpl/protocol/ConfidentialTransfer.h

@@ -490,4 +490,59 @@ computeSendRemainder(Slice const& balanceCommitment, Slice const& amountCommitme
  */
 std::optional<Buffer>
 computeConvertBackRemainder(Slice const& commitment, uint64_t amount);
+
+/**
+ * @brief Sequential reader for extracting proof components from a ZKProof blob.
+ *
+ * Encapsulates the offset-based arithmetic for slicing a concatenated proof
+ * blob into its individual components (equality proofs, Pedersen linkage
+ * proofs, bulletproofs, etc.).  Performs bounds checking on every read and
+ * tracks whether the entire blob has been consumed.
+ *
+ * Usage:
+ * @code
+ *   ProofReader reader(tx[sfZKProof]);
+ *   auto equalityProof = reader.read(sizeEquality);
+ *   auto pedersenProof = reader.read(ecPedersenProofLength);
+ *   if (!equalityProof || !pedersenProof || !reader.done())
+ *       return tecINTERNAL;
+ * @endcode
+ */
+class ProofReader
+{
+    Slice data_;
+    std::size_t offset_ = 0;
+
+public:
+    explicit ProofReader(Slice data) : data_(data)
+    {
+    }
+
+    /**
+     * @brief Read the next @p length bytes from the proof blob.
+     *
+     * @param length Number of bytes to read.
+     * @return A Slice of the requested bytes, or std::nullopt if there are
+     *         not enough remaining bytes.
+     */
+    [[nodiscard]] std::optional<Slice>
+    read(std::size_t length)
+    {
+        if (offset_ + length > data_.size())
+            return std::nullopt;
+        auto result = data_.substr(offset_, length);
+        offset_ += length;
+        return result;
+    }
+
+    /**
+     * @brief Returns true when every byte has been consumed.
+     */
+    [[nodiscard]] bool
+    done() const
+    {
+        return offset_ == data_.size();
+    }
+};
+
 }  // namespace xrpl

include/xrpl/protocol/Protocol.h

@@ -307,7 +307,7 @@ std::size_t constexpr permissionMaxSize = 10;
 /** The maximum number of transactions that can be in a batch. */
 std::size_t constexpr maxBatchTxCount = 8;
 
-/** EC ElGamal ciphertext length 33-byte */
+/** Length of one component of EC ElGamal ciphertext */
 std::size_t constexpr ecGamalEncryptedLength = 33;
 
 /** EC ElGamal ciphertext length: two 33-byte components concatenated */
@@ -331,9 +331,6 @@ std::size_t constexpr ecBlindingFactorLength = 32;
 /** Length of Schnorr ZKProof for public key registration in bytes */
 std::size_t constexpr ecSchnorrProofLength = 65;
 
-/** Length of ElGamal ciphertext equality proof in bytes */
-std::size_t constexpr ecCiphertextEqualityProofLength = 261;
-
 /** Length of ElGamal Pedersen linkage proof in bytes */
 std::size_t constexpr ecPedersenProofLength = 195;
 
@@ -347,9 +344,9 @@ std::size_t constexpr ecSingleBulletproofLength = 688;
 std::size_t constexpr ecDoubleBulletproofLength = 754;
 
 /** Compressed EC point prefix for even y-coordinate */
-static constexpr std::uint8_t ecCompressedPrefixEvenY = 0x02;
+std::uint8_t constexpr ecCompressedPrefixEvenY = 0x02;
 
 /** Compressed EC point prefix for odd y-coordinate */
-static constexpr std::uint8_t ecCompressedPrefixOddY = 0x03;
+std::uint8_t constexpr ecCompressedPrefixOddY = 0x03;
 
 }  // namespace xrpl