miniscript: take pubkey size into account in multi() type extdata

As in the previous commit, we were previously assuming that all pubkeys
were compressed. This isn't so. We have the keys, we can query them for
whether they are uncompressed or not.

Author: apoelstra

src/miniscript/mod.rs

@@ -275,7 +275,7 @@ mod private {
         pub fn multi(thresh: crate::Threshold<Pk, MAX_PUBKEYS_PER_MULTISIG>) -> Self {
             Self {
                 ty: types::Type::multi(),
-                ext: types::extra_props::ExtData::multi(thresh.k(), thresh.n()),
+                ext: types::extra_props::ExtData::multi(&thresh),
                 node: Terminal::Multi(thresh),
                 phantom: PhantomData,
             }

src/miniscript/types/extra_props.rs

@@ -7,6 +7,7 @@ use core::cmp;
 use core::iter::once;
 
 use super::ScriptContext;
+use crate::miniscript::limits::MAX_PUBKEYS_PER_MULTISIG;
 use crate::prelude::*;
 use crate::{script_num_size, AbsLockTime, MiniscriptKey, RelLockTime, Terminal};
 
@@ -242,15 +243,23 @@ impl ExtData {
     }
 
     /// Extra properties for the `multi` fragment.
-    pub fn multi(k: usize, n: usize) -> Self {
+    pub fn multi<Pk: MiniscriptKey>(
+        thresh: &crate::Threshold<Pk, MAX_PUBKEYS_PER_MULTISIG>,
+    ) -> Self {
+        let (n, k) = (thresh.n(), thresh.k());
         let num_cost = match (k > 16, n > 16) {
             (true, true) => 4,
             (false, true) => 3,
             (true, false) => 3,
             (false, false) => 2,
         };
         ExtData {
-            pk_cost: num_cost + 34 * n + 1,
+            pk_cost: num_cost
+                + thresh
+                    .iter()
+                    .map(|k| if k.is_uncompressed() { 65 } else { 34 })
+                    .sum::<usize>()
+                + 1,
             has_free_verify: true,
             // Multi is the only case because of which we need to count additional
             // executed opcodes.
@@ -940,7 +949,7 @@ impl ExtData {
             Terminal::PkK(ref k) => Self::pk_k::<_, Ctx>(k),
             Terminal::PkH(ref k) => Self::pk_h::<_, Ctx>(Some(k)),
             Terminal::RawPkH(..) => Self::pk_h::<Pk, Ctx>(None),
-            Terminal::Multi(ref thresh) => Self::multi(thresh.k(), thresh.n()),
+            Terminal::Multi(ref thresh) => Self::multi(thresh),
             Terminal::MultiA(ref thresh) => Self::multi_a(thresh.k(), thresh.n()),
             Terminal::After(t) => Self::after(t),
             Terminal::Older(t) => Self::older(t),