Track miniscript tree depth explicitly

Author: sanket1729

src/lib.rs

@@ -898,6 +898,7 @@ mod tests {
     }
 }
 
+#[allow(unused_imports)] // this is an internal prelude module; not all imports are used with every feature combination
 mod prelude {
     // Mutex implementation from LDK
     // https://github.com/lightningdevkit/rust-lightning/blob/9bdce47f0e0516e37c89c09f1975dfc06b5870b1/lightning-invoice/src/sync.rs

src/miniscript/mod.rs

@@ -21,7 +21,7 @@ use bitcoin::taproot::{LeafVersion, TapLeafHash};
 
 use self::analyzable::ExtParams;
 pub use self::context::{BareCtx, Legacy, Segwitv0, Tap};
-use crate::prelude::*;
+use crate::{prelude::*, MAX_RECURSION_DEPTH};
 use crate::TranslateErr;
 
 pub mod analyzable;
@@ -116,6 +116,13 @@ impl<Pk: MiniscriptKey, Ctx: ScriptContext> Miniscript<Pk, Ctx> {
             node: t,
             phantom: PhantomData,
         };
+        // TODO: This recursion depth is based on segwitv0.
+        // We can relax this in tapscript, but this should be good for almost
+        // all practical cases and we can revisit this if needed.
+        // casting to u32 is safe because tree_height will never go more than u32::MAX
+        if (res.ext.tree_height as u32) > MAX_RECURSION_DEPTH {
+            return Err(Error::MaxRecursiveDepthExceeded);
+        }
         Ctx::check_global_consensus_validity(&res)?;
         Ok(res)
     }

src/miniscript/types/extra_props.rs

@@ -139,6 +139,9 @@ pub struct ExtData {
     /// This does **not** include initial witness elements. This element only captures
     /// the additional elements that are pushed during execution.
     pub exec_stack_elem_count_dissat: Option<usize>,
+    /// The miniscript tree depth/height of this node.
+    /// Used for checking the max depth of the miniscript tree to prevent stack overflow.
+    pub tree_height: usize,
 }
 
 impl Property for ExtData {
@@ -165,6 +168,7 @@ impl Property for ExtData {
             timelock_info: TimelockInfo::default(),
             exec_stack_elem_count_sat: Some(1),
             exec_stack_elem_count_dissat: None,
+            tree_height : 0,
         }
     }
 
@@ -180,6 +184,7 @@ impl Property for ExtData {
             timelock_info: TimelockInfo::default(),
             exec_stack_elem_count_sat: None,
             exec_stack_elem_count_dissat: Some(1),
+            tree_height : 0,
         }
     }
 
@@ -201,6 +206,7 @@ impl Property for ExtData {
             timelock_info: TimelockInfo::default(),
             exec_stack_elem_count_sat: Some(1), // pushes the pk
             exec_stack_elem_count_dissat: Some(1),
+            tree_height: 0,
         }
     }
 
@@ -222,6 +228,7 @@ impl Property for ExtData {
             timelock_info: TimelockInfo::default(),
             exec_stack_elem_count_sat: Some(2), // dup and hash push
             exec_stack_elem_count_dissat: Some(2),
+            tree_height: 0,
         }
     }
 
@@ -245,6 +252,7 @@ impl Property for ExtData {
             timelock_info: TimelockInfo::default(),
             exec_stack_elem_count_sat: Some(n), // n pks
             exec_stack_elem_count_dissat: Some(n),
+            tree_height: 0,
         }
     }
 
@@ -267,6 +275,7 @@ impl Property for ExtData {
             timelock_info: TimelockInfo::default(),
             exec_stack_elem_count_sat: Some(2), // the two nums before num equal verify
             exec_stack_elem_count_dissat: Some(2),
+            tree_height: 0,
         }
     }
 
@@ -287,6 +296,7 @@ impl Property for ExtData {
             timelock_info: TimelockInfo::default(),
             exec_stack_elem_count_sat: Some(2), // either size <32> or <hash256> <32 byte>
             exec_stack_elem_count_dissat: Some(2),
+            tree_height: 0,
         }
     }
 
@@ -302,6 +312,7 @@ impl Property for ExtData {
             timelock_info: TimelockInfo::default(),
             exec_stack_elem_count_sat: Some(2), // either size <32> or <hash256> <32 byte>
             exec_stack_elem_count_dissat: Some(2),
+            tree_height: 0,
         }
     }
 
@@ -317,6 +328,7 @@ impl Property for ExtData {
             timelock_info: TimelockInfo::default(),
             exec_stack_elem_count_sat: Some(2), // either size <32> or <hash256> <20 byte>
             exec_stack_elem_count_dissat: Some(2),
+            tree_height: 0,
         }
     }
 
@@ -332,6 +344,7 @@ impl Property for ExtData {
             timelock_info: TimelockInfo::default(),
             exec_stack_elem_count_sat: Some(2), // either size <32> or <hash256> <20 byte>
             exec_stack_elem_count_dissat: Some(2),
+            tree_height: 0,
         }
     }
 
@@ -357,6 +370,7 @@ impl Property for ExtData {
             },
             exec_stack_elem_count_sat: Some(1), // <t>
             exec_stack_elem_count_dissat: None,
+            tree_height: 0,
         }
     }
 
@@ -378,6 +392,7 @@ impl Property for ExtData {
             },
             exec_stack_elem_count_sat: Some(1), // <t>
             exec_stack_elem_count_dissat: None,
+            tree_height: 0,
         }
     }
 
@@ -393,6 +408,7 @@ impl Property for ExtData {
             timelock_info: self.timelock_info,
             exec_stack_elem_count_sat: self.exec_stack_elem_count_sat,
             exec_stack_elem_count_dissat: self.exec_stack_elem_count_dissat,
+            tree_height : self.tree_height + 1,
         })
     }
 
@@ -408,6 +424,7 @@ impl Property for ExtData {
             timelock_info: self.timelock_info,
             exec_stack_elem_count_sat: self.exec_stack_elem_count_sat,
             exec_stack_elem_count_dissat: self.exec_stack_elem_count_dissat,
+            tree_height : self.tree_height + 1,
         })
     }
 
@@ -423,6 +440,7 @@ impl Property for ExtData {
             timelock_info: self.timelock_info,
             exec_stack_elem_count_sat: self.exec_stack_elem_count_sat,
             exec_stack_elem_count_dissat: self.exec_stack_elem_count_dissat,
+            tree_height : self.tree_height + 1,
         })
     }
 
@@ -441,6 +459,7 @@ impl Property for ExtData {
             // Even all V types push something onto the stack and then remove them
             exec_stack_elem_count_sat: self.exec_stack_elem_count_sat,
             exec_stack_elem_count_dissat: Some(1),
+            tree_height : self.tree_height + 1,
         })
     }
 
@@ -457,6 +476,7 @@ impl Property for ExtData {
             timelock_info: self.timelock_info,
             exec_stack_elem_count_sat: self.exec_stack_elem_count_sat,
             exec_stack_elem_count_dissat: None,
+            tree_height : self.tree_height + 1,
         })
     }
 
@@ -472,6 +492,7 @@ impl Property for ExtData {
             timelock_info: self.timelock_info,
             exec_stack_elem_count_sat: self.exec_stack_elem_count_sat,
             exec_stack_elem_count_dissat: Some(1),
+            tree_height : self.tree_height + 1,
         })
     }
 
@@ -488,6 +509,7 @@ impl Property for ExtData {
             // Technically max(1, self.exec_stack_elem_count_sat), same rationale as cast_dupif
             exec_stack_elem_count_sat: self.exec_stack_elem_count_sat,
             exec_stack_elem_count_dissat: self.exec_stack_elem_count_dissat,
+            tree_height : self.tree_height + 1,
         })
     }
 
@@ -528,6 +550,7 @@ impl Property for ExtData {
                 l.exec_stack_elem_count_dissat,
                 r.exec_stack_elem_count_dissat.map(|x| x + 1),
             ),
+            tree_height : cmp::max(l.tree_height, r.tree_height) + 1,
         })
     }
 
@@ -555,6 +578,7 @@ impl Property for ExtData {
                 r.exec_stack_elem_count_sat,
             ),
             exec_stack_elem_count_dissat: None,
+            tree_height : cmp::max(l.tree_height, r.tree_height) + 1,
         })
     }
 
@@ -603,6 +627,7 @@ impl Property for ExtData {
                 l.exec_stack_elem_count_dissat,
                 r.exec_stack_elem_count_dissat.map(|x| x + 1),
             ),
+            tree_height : cmp::max(l.tree_height, r.tree_height) + 1,
         })
     }
 
@@ -640,6 +665,7 @@ impl Property for ExtData {
                 l.exec_stack_elem_count_dissat,
                 r.exec_stack_elem_count_dissat.map(|x| x + 1),
             ),
+            tree_height : cmp::max(l.tree_height, r.tree_height) + 1,
         };
         Ok(res)
     }
@@ -671,6 +697,7 @@ impl Property for ExtData {
                 opt_max(r.exec_stack_elem_count_sat, l.exec_stack_elem_count_dissat),
             ),
             exec_stack_elem_count_dissat: None,
+            tree_height : cmp::max(l.tree_height, r.tree_height) + 1,
         })
     }
 
@@ -717,6 +744,7 @@ impl Property for ExtData {
                 l.exec_stack_elem_count_dissat,
                 r.exec_stack_elem_count_dissat,
             ),
+            tree_height : cmp::max(l.tree_height, r.tree_height) + 1,
         })
     }
 
@@ -762,6 +790,7 @@ impl Property for ExtData {
                 a.exec_stack_elem_count_dissat,
                 c.exec_stack_elem_count_dissat,
             ),
+            tree_height : cmp::max(a.tree_height, cmp::max(b.tree_height, c.tree_height)) + 1,
         })
     }
 
@@ -781,6 +810,7 @@ impl Property for ExtData {
         // the max element count is same as max sat element count when satisfying one element + 1
         let mut exec_stack_elem_count_sat_vec = Vec::with_capacity(n);
         let mut exec_stack_elem_count_dissat = Some(0);
+        let mut max_child_height = 0;
 
         for i in 0..n {
             let sub = sub_ck(i)?;
@@ -814,6 +844,7 @@ impl Property for ExtData {
                 exec_stack_elem_count_dissat,
                 sub.exec_stack_elem_count_dissat,
             );
+            max_child_height = cmp::max(max_child_height, sub.tree_height) + 1;
         }
 
         stack_elem_count_sat_vec.sort_by(sat_minus_option_dissat);
@@ -885,6 +916,7 @@ impl Property for ExtData {
             timelock_info: TimelockInfo::combine_threshold(k, timelocks),
             exec_stack_elem_count_sat,
             exec_stack_elem_count_dissat,
+            tree_height : max_child_height + 1,
         })
     }