Implement SS58 encoding and decoding (#691)

* Implement SS58 encoding and decoding

* PR link

lib/src/identity.rs

@@ -85,5 +85,4 @@
 
 pub mod keystore;
 pub mod seed_phrase;
-
-// TODO: implement ss58
+pub mod ss58;

lib/src/identity/ss58.rs

@@ -0,0 +1,210 @@
+// Smoldot
+// Copyright (C) 2023  Pierre Krieger
+// SPDX-License-Identifier: GPL-3.0-or-later WITH Classpath-exception-2.0
+
+// This program is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+
+// This program is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+
+// You should have received a copy of the GNU General Public License
+// along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+use alloc::{string::String, vec::Vec};
+use core::fmt;
+
+/// Decoded version of an SS58 address.
+#[derive(Debug, Copy, Clone, PartialEq, Eq)]
+pub struct Decoded<P> {
+    /// Identifier indicating which chain is concerned.
+    ///
+    /// The mapping between chains and this prefix can be found in this central registry:
+    /// <https://github.com/paritytech/ss58-registry/blob/main/ss58-registry.json>.
+    pub chain_prefix: ChainPrefix,
+
+    /// Public key of the account.
+    pub public_key: P,
+}
+
+/// Identifier indicating which chain is concerned.
+///
+/// The mapping between chains and this prefix can be found in this central registry:
+/// <https://github.com/paritytech/ss58-registry/blob/main/ss58-registry.json>.
+///
+/// This prefix is a 14 bits unsigned integer.
+//
+// Implementation note: the `u16` is guaranteed to be only up to 14 bits long. The upper two bits
+// are always 0.
+#[derive(Copy, Clone, PartialEq, Eq)]
+pub struct ChainPrefix(u16);
+
+impl fmt::Debug for ChainPrefix {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        fmt::Debug::fmt(&self.0, f)
+    }
+}
+
+impl TryFrom<u16> for ChainPrefix {
+    type Error = PrefixTooLargeError;
+
+    fn try_from(prefix: u16) -> Result<Self, Self::Error> {
+        if (prefix >> 14) == 0 {
+            Ok(ChainPrefix(prefix))
+        } else {
+            Err(PrefixTooLargeError())
+        }
+    }
+}
+
+/// Integer is too large to be a valid prefix
+#[derive(Debug, Clone, derive_more::Display)]
+pub struct PrefixTooLargeError();
+
+impl From<u8> for ChainPrefix {
+    fn from(prefix: u8) -> ChainPrefix {
+        ChainPrefix(u16::from(prefix))
+    }
+}
+
+impl From<ChainPrefix> for u16 {
+    fn from(prefix: ChainPrefix) -> u16 {
+        prefix.0
+    }
+}
+
+/// Turns a decoded SS58 address into a string.
+pub fn encode(decoded: Decoded<impl AsRef<[u8]>>) -> String {
+    let prefix = decoded.chain_prefix.0;
+    let public_key = decoded.public_key.as_ref();
+
+    let mut bytes = Vec::with_capacity(2 + public_key.len() + 2);
+
+    if prefix < 64 {
+        bytes.push(prefix as u8);
+    } else {
+        // This encoding is plain weird.
+        bytes.push(((prefix & 0b0000_0000_1111_1100) as u8) >> 2 | 0b01000000);
+        bytes.push(((prefix >> 8) as u8) | ((prefix & 0b0000_0000_0000_0011) as u8) << 6);
+    }
+
+    bytes.extend_from_slice(public_key);
+
+    let checksum = calculate_checksum(&bytes);
+    bytes.extend_from_slice(&checksum);
+
+    bs58::encode(&bytes).into_string()
+}
+
+/// Decodes an SS58 address from a string.
+pub fn decode(encoded: &'_ str) -> Result<Decoded<impl AsRef<[u8]>>, DecodeError> {
+    let mut bytes = bs58::decode(encoded)
+        .into_vec()
+        .map_err(|err| DecodeError::InvalidBs58(Bs58DecodeError(err)))?;
+
+    if bytes.len() < 4 {
+        return Err(DecodeError::TooShort);
+    }
+
+    // Verify the checksum.
+    let expected_checksum = calculate_checksum(&bytes[..bytes.len() - 2]);
+    if expected_checksum[..] != bytes[bytes.len() - 2..] {
+        return Err(DecodeError::InvalidChecksum);
+    }
+    bytes.truncate(bytes.len() - 2);
+
+    // Grab and remove the prefix.
+    let (prefix_len, chain_prefix) = if bytes[0] < 64 {
+        (1, ChainPrefix(u16::from(bytes[0])))
+    } else if bytes[0] < 128 {
+        let prefix = u16::from_be_bytes([bytes[1] & 0b00111111, (bytes[0] << 2) | (bytes[1] >> 6)]);
+        (2, ChainPrefix(prefix))
+    } else {
+        return Err(DecodeError::InvalidPrefix);
+    };
+
+    // Rather than remove the prefix from the beginning of `bytes`, we adjust the `AsRef`
+    // implementation to skip the prefix.
+    let public_key = {
+        struct Adjust(Vec<u8>, usize);
+        impl AsRef<[u8]> for Adjust {
+            fn as_ref(&self) -> &[u8] {
+                &self.0[self.1..]
+            }
+        }
+        Adjust(bytes, prefix_len)
+    };
+
+    Ok(Decoded {
+        chain_prefix,
+        public_key,
+    })
+}
+
+/// Error while decoding an SS58 address.
+#[derive(Debug, Clone, derive_more::Display)]
+pub enum DecodeError {
+    /// SS58 is too short to possibly be valid.
+    TooShort,
+    /// Invalid SS58 prefix encoding.
+    InvalidPrefix,
+    /// Invalid BS58 format.
+    #[display(fmt = "{_0}")]
+    InvalidBs58(Bs58DecodeError),
+    /// Calculated checksum doesn't match the one provided.
+    InvalidChecksum,
+}
+
+/// Error when decoding Base58 encoding.
+#[derive(Debug, Clone, derive_more::Display, derive_more::From)]
+pub struct Bs58DecodeError(bs58::decode::Error);
+
+fn calculate_checksum(data: &[u8]) -> [u8; 2] {
+    let mut hasher = blake2_rfc::blake2b::Blake2b::new(64);
+    hasher.update(b"SS58PRE");
+    hasher.update(data);
+
+    let hash = hasher.finalize();
+    *<&[u8; 2]>::try_from(&hash.as_bytes()[..2]).unwrap_or_else(|_| unreachable!())
+}
+
+#[cfg(test)]
+mod tests {
+    #[test]
+    fn alice_polkadot() {
+        let encoded = "15oF4uVJwmo4TdGW7VfQxNLavjCXviqxT9S1MgbjMNHr6Sp5";
+
+        let decoded = super::decode(encoded).unwrap();
+        assert_eq!(u16::from(decoded.chain_prefix), 0);
+        assert_eq!(
+            decoded.public_key.as_ref(),
+            &[
+                212, 53, 147, 199, 21, 253, 211, 28, 97, 20, 26, 189, 4, 169, 159, 214, 130, 44,
+                133, 88, 133, 76, 205, 227, 154, 86, 132, 231, 165, 109, 162, 125
+            ][..]
+        );
+
+        assert_eq!(super::encode(decoded), encoded);
+    }
+
+    #[test]
+    fn sora_default_seed_phrase() {
+        let encoded = "cnT6GtrVo7AYsRc2LgfTgW8Gu4gpZpxhaaKMm7zH8Ry14pJ8b";
+
+        let decoded = super::decode(encoded).unwrap();
+        assert_eq!(u16::from(decoded.chain_prefix), 69);
+        assert_eq!(
+            decoded.public_key.as_ref(),
+            &[
+                70, 235, 221, 239, 140, 217, 187, 22, 125, 195, 8, 120, 215, 17, 59, 126, 22, 142,
+                111, 6, 70, 190, 255, 215, 125, 105, 211, 155, 173, 118, 180, 122
+            ][..]
+        );
+
+        assert_eq!(super::encode(decoded), encoded);
+    }
+}

lib/src/json_rpc/methods.rs

@@ -18,7 +18,7 @@
 //! List of requests and how to answer them.
 
 use super::parse;
-use crate::header;
+use crate::{header, identity::ss58};
 
 use alloc::{
     borrow::Cow,
@@ -614,7 +614,7 @@ pub enum RemoveMetadataLengthPrefixError {
 ///
 /// The deserialization involves decoding an SS58 address into this public key.
 #[derive(Debug, Clone)]
-pub struct AccountId(pub [u8; 32]);
+pub struct AccountId(pub Vec<u8>);
 
 impl serde::Serialize for AccountId {
     fn serialize<S>(&self, _: S) -> Result<S::Ok, S::Error>
@@ -632,25 +632,14 @@ impl<'a> serde::Deserialize<'a> for AccountId {
         D: serde::Deserializer<'a>,
     {
         let string = <&str>::deserialize(deserializer)?;
-        let decoded = match bs58::decode(&string).into_vec() {
-            // TODO: don't use into_vec
+        let decoded = match ss58::decode(string) {
             Ok(d) => d,
-            Err(_) => return Err(serde::de::Error::custom("AccountId isn't in base58 format")),
+            Err(err) => return Err(serde::de::Error::custom(err.to_string())),
         };
 
-        // TODO: retrieve the actual prefix length of the current chain
-        if decoded.len() < 35 {
-            return Err(serde::de::Error::custom("unexpected length for AccountId"));
-        }
-
-        // TODO: finish implementing this properly ; must notably check checksum
-        // see https://github.com/paritytech/substrate/blob/74a50abd6cbaad1253daf3585d5cdaa4592e9184/primitives/core/src/crypto.rs#L228
-
-        // TODO: retrieve and use the actual prefix length of the current chain
-        let account_id =
-            <[u8; 32]>::try_from(&decoded[(decoded.len() - 34)..(decoded.len() - 2)]).unwrap();
+        // TODO: check the prefix against the one of the current chain?
 
-        Ok(AccountId(account_id))
+        Ok(AccountId(decoded.public_key.as_ref().to_vec()))
     }
 }
 

wasm-node/CHANGELOG.md

@@ -5,6 +5,7 @@
 ### Added
 
 - Add support for child tries, meaning that errors will no longer be returned when performing runtime calls on chains that use child tries. In practice, this typically concerns contracts chains. ([#680](https://github.com/smol-dot/smoldot/pull/680), [#684](https://github.com/smol-dot/smoldot/pull/684))
+- The checksum of the SS58 address passed to the `system_accountNextIndex` JSON-RPC function is now verified. Note that its prefix isn't compared against the one of the current chain, because there is no straight-forward way for smoldot to determine the SS58 prefix of the chain that it is running. ([#691](https://github.com/smol-dot/smoldot/pull/691))
 
 ### Fixed