Fixup borked PSBT signing + finalize

src/psbt.c

@@ -2542,7 +2542,7 @@ int wally_sign_psbt(
         struct wally_tx_input *txin = &psbt->tx->inputs[i];
         unsigned char sighash[SHA256_LEN], *scriptcode, wpkh_sc[WALLY_SCRIPTPUBKEY_P2PKH_LEN];
         size_t scriptcode_len;
-        bool match = false, comp = false;
+        bool match = false, comp = false, already_signed = false;
         uint32_t sighash_type = WALLY_SIGHASH_ALL;
 
         if (!input->keypaths) {
@@ -2568,6 +2568,23 @@ int wally_sign_psbt(
             continue;
         }
 
+        /* Make sure we don't already have a sig for this input ?! */
+        if (input->partial_sigs) {
+            for (j = 0; j < input->partial_sigs->num_items; j++) {
+                struct wally_partial_sigs_item *item = &input->partial_sigs->items[j];
+                if (memcmp((char *)item->pubkey, (char *)uncomp_pubkey, EC_PUBLIC_KEY_UNCOMPRESSED_LEN) == 0
+                    || memcmp((char *)item->pubkey, (char *)pubkey, EC_PUBLIC_KEY_LEN) == 0) {
+                    already_signed = true;
+                    break;
+                }
+            }
+        }
+
+        /* We've already got a partial sig for this pubkey on this input */
+        if (already_signed) {
+            continue;
+        }
+
         /* Sighash type */
         if (input->sighash_type > 0) {
             sighash_type = input->sighash_type;
@@ -2697,7 +2714,9 @@ int wally_finalize_psbt(struct wally_psbt *psbt)
     for (i = 0; i < psbt->num_inputs; ++i) {
         struct wally_psbt_input *input = &psbt->inputs[i];
         struct wally_tx_input *txin = &psbt->tx->inputs[i];
-        unsigned char *out_script = NULL; /* Script that determines how we should finalize this input, typically output script */
+        /* Script for this input. originally set to the input's scriptPubKey, but in the case of a p2sh/p2wsh
+         * input, it will be eventually be set to the unhashed script, if known */
+        unsigned char *out_script = NULL;
         size_t out_script_len, type;
         bool witness = false, p2sh = false;;
 
@@ -2706,15 +2725,22 @@ int wally_finalize_psbt(struct wally_psbt *psbt)
             continue;
         }
 
-        if (input->redeem_script) {
-            out_script = input->redeem_script;
-            out_script_len = input->redeem_script_len;
-            p2sh = true;
+        /* Note that if we patch libwally to supply the non-witness utxo tx field (tx) for
+        * witness inputs also, we'll need a different way to signal p2sh-p2wpkh scripts */
+        if (input->witness_utxo && input->witness_utxo->script_len > 0) {
+            out_script = input->witness_utxo->script;
+            out_script_len = input->witness_utxo->script_len;
+            witness = true;
         } else if (input->non_witness_utxo && input->non_witness_utxo->num_outputs > txin->index) {
             struct wally_tx_output out = input->non_witness_utxo->outputs[txin->index];
             out_script = out.script;
             out_script_len = out.script_len;
         }
+        if (input->redeem_script) {
+            out_script = input->redeem_script;
+            out_script_len = input->redeem_script_len;
+            p2sh = true;
+        }
         if (input->witness_script) {
             out_script = input->witness_script;
             out_script_len = input->witness_script_len;
@@ -2735,7 +2761,7 @@ int wally_finalize_psbt(struct wally_psbt *psbt)
         case WALLY_SCRIPT_TYPE_P2WPKH: {
             struct wally_partial_sigs_item *partial_sig;
             unsigned char script_sig[WALLY_SCRIPTSIG_P2PKH_MAX_LEN];
-            size_t script_sig_len, pubkey_len = EC_PUBLIC_KEY_UNCOMPRESSED_LEN;
+            size_t written, script_sig_len, pubkey_len = EC_PUBLIC_KEY_UNCOMPRESSED_LEN;
 
             if (!input->partial_sigs || input->partial_sigs->num_items != 1) {
                 /* Must be single key, single sig */
@@ -2757,6 +2783,16 @@ int wally_finalize_psbt(struct wally_psbt *psbt)
                 if ((ret = wally_witness_p2wpkh_from_der(partial_sig->pubkey, pubkey_len, partial_sig->sig, partial_sig->sig_len, &input->final_witness)) != WALLY_OK) {
                     return ret;
                 }
+                if (input->redeem_script) {
+                    /* P2SH wrapped witness requires final scriptsig of pushing the redeemScript */
+                    script_sig_len = varint_get_length(input->redeem_script_len) + input->redeem_script_len;
+                    input->final_script_sig = wally_malloc(script_sig_len);
+                    if ((ret = wally_script_push_from_bytes(input->redeem_script, input->redeem_script_len, 0, input->final_script_sig, script_sig_len, &written)) != WALLY_OK) {
+                        wally_free(input->final_script_sig);
+                        return ret;
+                    }
+                    input->final_script_sig_len = written;
+                }
             }
             break;
         }