Merge rust-bitcoin#2949: OP_RETURN standardness check

15f6bac api: Run just check-api (Ryan Breen)
9684d49 Add is_standard_op_return (Ryan Breen)

Pull request description:

  This is the suggestion for rust-bitcoin#2292 to check OP_RETURN length

ACKs for top commit:
  apoelstra:
    ACK 15f6bac

Tree-SHA512: e346b5eff7cc40b98a08948c83cb5c064184541d819c37a977e432ec09df7f9e1a074f16a4df598142784bd875f1379e2b0848fe898923e4e12829f85b4c4520

Author: apoelstra

api/bitcoin/all-features.txt

@@ -8209,6 +8209,7 @@ pub fn bitcoin::blockdata::script::Script::is_p2wpkh(&self) -> bool
 pub fn bitcoin::blockdata::script::Script::is_p2wsh(&self) -> bool
 pub fn bitcoin::blockdata::script::Script::is_provably_unspendable(&self) -> bool
 pub fn bitcoin::blockdata::script::Script::is_push_only(&self) -> bool
+pub fn bitcoin::blockdata::script::Script::is_standard_op_return(&self) -> bool
 pub fn bitcoin::blockdata::script::Script::is_witness_program(&self) -> bool
 pub fn bitcoin::blockdata::script::Script::len(&self) -> usize
 pub fn bitcoin::blockdata::script::Script::minimal_non_dust(&self) -> bitcoin_units::amount::Amount

api/bitcoin/default-features.txt

@@ -7831,6 +7831,7 @@ pub fn bitcoin::blockdata::script::Script::is_p2wpkh(&self) -> bool
 pub fn bitcoin::blockdata::script::Script::is_p2wsh(&self) -> bool
 pub fn bitcoin::blockdata::script::Script::is_provably_unspendable(&self) -> bool
 pub fn bitcoin::blockdata::script::Script::is_push_only(&self) -> bool
+pub fn bitcoin::blockdata::script::Script::is_standard_op_return(&self) -> bool
 pub fn bitcoin::blockdata::script::Script::is_witness_program(&self) -> bool
 pub fn bitcoin::blockdata::script::Script::len(&self) -> usize
 pub fn bitcoin::blockdata::script::Script::minimal_non_dust(&self) -> bitcoin_units::amount::Amount

api/bitcoin/no-features.txt

@@ -7182,6 +7182,7 @@ pub fn bitcoin::blockdata::script::Script::is_p2wpkh(&self) -> bool
 pub fn bitcoin::blockdata::script::Script::is_p2wsh(&self) -> bool
 pub fn bitcoin::blockdata::script::Script::is_provably_unspendable(&self) -> bool
 pub fn bitcoin::blockdata::script::Script::is_push_only(&self) -> bool
+pub fn bitcoin::blockdata::script::Script::is_standard_op_return(&self) -> bool
 pub fn bitcoin::blockdata::script::Script::is_witness_program(&self) -> bool
 pub fn bitcoin::blockdata::script::Script::len(&self) -> usize
 pub fn bitcoin::blockdata::script::Script::minimal_non_dust(&self) -> bitcoin_units::amount::Amount

bitcoin/src/blockdata/script/borrowed.rs

@@ -349,7 +349,10 @@ impl Script {
             && self.0[1] == OP_PUSHBYTES_32.to_u8()
     }
 
-    /// Check if this is an OP_RETURN output.
+    /// Check if this is a consensus-valid OP_RETURN output.
+    ///
+    /// To validate if the OP_RETURN obeys Bitcoin Core's current standardness policy, use
+    /// [`is_standard_op_return()`](Self::is_standard_op_return) instead.
     #[inline]
     pub fn is_op_return(&self) -> bool {
         match self.0.first() {
@@ -358,6 +361,15 @@ impl Script {
         }
     }
 
+    /// Check if this is an OP_RETURN that obeys Bitcoin Core standardness policy.
+    ///
+    /// What this function considers to be standard may change without warning pending Bitcoin Core
+    /// changes.
+    #[inline]
+    pub fn is_standard_op_return(&self) -> bool {
+        self.is_op_return() && self.0.len() <= 80
+    }
+
     /// Checks whether a script is trivially known to have no satisfying input.
     ///
     /// This method has potentially confusing semantics and an unclear purpose, so it's going to be

bitcoin/src/blockdata/script/tests.rs

@@ -406,6 +406,20 @@ fn op_return_test() {
     assert!(!ScriptBuf::from_hex("").unwrap().is_op_return());
 }
 
+#[test]
+fn standard_op_return_test() {
+    assert!(ScriptBuf::from_hex("6aa9149eb21980dc9d413d8eac27314938b9da920ee53e87")
+        .unwrap()
+        .is_standard_op_return());
+    assert!(ScriptBuf::from_hex("6a48656c6c6f2c2074686973206973206d7920666972737420636f6e747269627574696f6e20746f207275737420626974636f696e2e20506c6561736520617070726f7665206d79205052206672656e")
+        .unwrap()
+        .is_standard_op_return());
+
+    assert!(!ScriptBuf::from_hex("6a48656c6c6f2c2074686973206973206d7920666972737420636f6e747269627574696f6e20746f207275737420626974636f696e2e20506c6561736520617070726f7665206d79205052206672656e21")
+        .unwrap()
+        .is_standard_op_return());
+}
+
 #[test]
 fn multisig() {
     // First multisig? 1-of-2