feat: refund multi sig (#860)

crates/cashu/src/nuts/nut11/mod.rs

@@ -178,15 +178,24 @@ impl Proof {
             spending_conditions.locktime,
             spending_conditions.refund_keys,
         ) {
+            let needed_refund_sigs = spending_conditions.num_sigs_refund.unwrap_or(1) as usize;
+
+            let mut valid_pubkeys = HashSet::new();
+
             // If lock time has passed check if refund witness signature is valid
             if locktime.lt(&unix_time()) {
                 for s in witness_signatures.iter() {
                     for v in &refund_keys {
                         let sig = Signature::from_str(s).map_err(|_| Error::InvalidSignature)?;
 
-                        // As long as there is one valid refund signature it can be spent
                         if v.verify(msg, &sig).is_ok() {
-                            return Ok(());
+                            if !valid_pubkeys.insert(v) {
+                                return Err(Error::DuplicateSignature);
+                            }
+
+                            if valid_pubkeys.len() >= needed_refund_sigs {
+                                return Ok(());
+                            }
                         }
                     }
                 }
@@ -443,7 +452,7 @@ pub struct Conditions {
     /// Refund keys
     #[serde(skip_serializing_if = "Option::is_none")]
     pub refund_keys: Option<Vec<PublicKey>>,
-    /// Numbedr of signatures required
+    /// Number of signatures required
     ///
     /// Default is 1
     #[serde(skip_serializing_if = "Option::is_none")]
@@ -452,6 +461,11 @@ pub struct Conditions {
     ///
     /// Default [`SigFlag::SigInputs`]
     pub sig_flag: SigFlag,
+    /// Number of refund signatures required
+    ///
+    /// Default is 1
+    #[serde(skip_serializing_if = "Option::is_none")]
+    pub num_sigs_refund: Option<u64>,
 }
 
 impl Conditions {
@@ -462,6 +476,7 @@ impl Conditions {
         refund_keys: Option<Vec<PublicKey>>,
         num_sigs: Option<u64>,
         sig_flag: Option<SigFlag>,
+        num_sigs_refund: Option<u64>,
     ) -> Result<Self, Error> {
         if let Some(locktime) = locktime {
             ensure_cdk!(locktime.ge(&unix_time()), Error::LocktimeInPast);
@@ -473,6 +488,7 @@ impl Conditions {
             refund_keys,
             num_sigs,
             sig_flag: sig_flag.unwrap_or_default(),
+            num_sigs_refund,
         })
     }
 }
@@ -484,6 +500,7 @@ impl From<Conditions> for Vec<Vec<String>> {
             refund_keys,
             num_sigs,
             sig_flag,
+            num_sigs_refund: _,
         } = conditions;
 
         let mut tags = Vec::new();
@@ -564,6 +581,7 @@ impl TryFrom<Vec<Vec<String>>> for Conditions {
             refund_keys,
             num_sigs,
             sig_flag,
+            num_sigs_refund: None,
         })
     }
 }
@@ -583,6 +601,9 @@ pub enum TagKind {
     Refund,
     /// Pubkey
     Pubkeys,
+    /// Number signatures required
+    #[serde(rename = "n_sigs_refund")]
+    NSigsRefund,
     /// Custom tag kind
     Custom(String),
 }
@@ -595,6 +616,7 @@ impl fmt::Display for TagKind {
             Self::Locktime => write!(f, "locktime"),
             Self::Refund => write!(f, "refund"),
             Self::Pubkeys => write!(f, "pubkeys"),
+            Self::NSigsRefund => write!(f, "n_sigs_refund"),
             Self::Custom(kind) => write!(f, "{kind}"),
         }
     }
@@ -857,6 +879,7 @@ mod tests {
             .unwrap()]),
             num_sigs: Some(2),
             sig_flag: SigFlag::SigAll,
+            num_sigs_refund: None,
         };
 
         let secret: Nut10Secret = Nut10Secret::new(Kind::P2PK, data.to_string(), Some(conditions));
@@ -891,6 +914,7 @@ mod tests {
             refund_keys: Some(vec![v_key]),
             num_sigs: Some(2),
             sig_flag: SigFlag::SigInputs,
+            num_sigs_refund: None,
         };
 
         let secret: Secret = Nut10Secret::new(Kind::P2PK, v_key.to_string(), Some(conditions))

crates/cdk-cli/src/sub_commands/create_request.rs

@@ -161,6 +161,7 @@ pub async fn create_request(
                     refund_keys: None,
                     num_sigs: Some(num_sigs),
                     sig_flag: SigFlag::SigInputs,
+                    num_sigs_refund: None,
                 };
 
                 // Try to parse the hash
@@ -186,6 +187,7 @@ pub async fn create_request(
                     refund_keys: None,
                     num_sigs: Some(num_sigs),
                     sig_flag: SigFlag::SigInputs,
+                    num_sigs_refund: None,
                 };
 
                 // Create HTLC conditions with the hash and pubkeys in conditions
@@ -203,6 +205,7 @@ pub async fn create_request(
                         refund_keys: None,
                         num_sigs: Some(num_sigs),
                         sig_flag: SigFlag::SigInputs,
+                        num_sigs_refund: None,
                     }),
                 ))
             }

crates/cdk-cli/src/sub_commands/send.rs

@@ -118,6 +118,7 @@ pub async fn send(
                 refund_keys,
                 sub_command_args.required_sigs,
                 None,
+                None,
             )
             .unwrap();
 
@@ -155,8 +156,8 @@ pub async fn send(
                 refund_keys,
                 sub_command_args.required_sigs,
                 None,
-            )
-            .unwrap();
+                None,
+            )?;
 
             Some(SpendingConditions::new_htlc_hash(hash, Some(conditions))?)
         }
@@ -187,8 +188,8 @@ pub async fn send(
                     refund_keys,
                     sub_command_args.required_sigs,
                     None,
-                )
-                .unwrap();
+                    None,
+                )?;
 
                 Some(SpendingConditions::P2PKConditions {
                     data: data_pubkey,