accept base43-encoded tx in Qt "Load transaction"

When encoding transactions as QR codes, we encode the tx bytes as base43
first. This makes it easier to load a transaction if the user manually
decodes the QR code.

electrum/tests/test_transaction.py

@@ -1,5 +1,5 @@
 from electrum import transaction
-from electrum.transaction import TxOutputForUI
+from electrum.transaction import TxOutputForUI, tx_from_str
 from electrum.bitcoin import TYPE_ADDRESS
 from electrum.keystore import xpubkey_to_address
 from electrum.util import bh2u, bfh
@@ -171,6 +171,23 @@ class TestTransaction(SequentialTestCase):
         tx = transaction.Transaction(v2_blob)
         self.assertEqual(tx.txid(), "b97f9180173ab141b61b9f944d841e60feec691d6daab4d4d932b24dd36606fe")
 
+    def test_tx_from_str(self):
+        # json dict
+        self.assertEqual('020000000001012005273af813ba23b0c205e4b145e525c280dd876e061f35bff7db9b2e0043640100000000fdffffff02d885010000000000160014e73f444b8767c84afb46ef4125d8b81d2542a53d00e1f5050000000017a914052ed032f5c74a636ed5059611bb90012d40316c870247304402200c628917673d75f05db893cc377b0a69127f75e10949b35da52aa1b77a14c350022055187adf9a668fdf45fc09002726ba7160e713ed79dddcd20171308273f1a2f1012103cb3e00561c3439ccbacc033a72e0513bcfabff8826de0bc651d661991ade6171049e1600',
+                         tx_from_str("""{
+                                        "complete": true,
+                                        "final": false,
+                                        "hex": "020000000001012005273af813ba23b0c205e4b145e525c280dd876e061f35bff7db9b2e0043640100000000fdffffff02d885010000000000160014e73f444b8767c84afb46ef4125d8b81d2542a53d00e1f5050000000017a914052ed032f5c74a636ed5059611bb90012d40316c870247304402200c628917673d75f05db893cc377b0a69127f75e10949b35da52aa1b77a14c350022055187adf9a668fdf45fc09002726ba7160e713ed79dddcd20171308273f1a2f1012103cb3e00561c3439ccbacc033a72e0513bcfabff8826de0bc651d661991ade6171049e1600"
+                                    }
+                                    """)
+        )
+        # raw hex
+        self.assertEqual('020000000001012005273af813ba23b0c205e4b145e525c280dd876e061f35bff7db9b2e0043640100000000fdffffff02d885010000000000160014e73f444b8767c84afb46ef4125d8b81d2542a53d00e1f5050000000017a914052ed032f5c74a636ed5059611bb90012d40316c870247304402200c628917673d75f05db893cc377b0a69127f75e10949b35da52aa1b77a14c350022055187adf9a668fdf45fc09002726ba7160e713ed79dddcd20171308273f1a2f1012103cb3e00561c3439ccbacc033a72e0513bcfabff8826de0bc651d661991ade6171049e1600',
+                         tx_from_str('020000000001012005273af813ba23b0c205e4b145e525c280dd876e061f35bff7db9b2e0043640100000000fdffffff02d885010000000000160014e73f444b8767c84afb46ef4125d8b81d2542a53d00e1f5050000000017a914052ed032f5c74a636ed5059611bb90012d40316c870247304402200c628917673d75f05db893cc377b0a69127f75e10949b35da52aa1b77a14c350022055187adf9a668fdf45fc09002726ba7160e713ed79dddcd20171308273f1a2f1012103cb3e00561c3439ccbacc033a72e0513bcfabff8826de0bc651d661991ade6171049e1600'))
+        # base43
+        self.assertEqual('020000000001012005273af813ba23b0c205e4b145e525c280dd876e061f35bff7db9b2e0043640100000000fdffffff02d885010000000000160014e73f444b8767c84afb46ef4125d8b81d2542a53d00e1f5050000000017a914052ed032f5c74a636ed5059611bb90012d40316c870247304402200c628917673d75f05db893cc377b0a69127f75e10949b35da52aa1b77a14c350022055187adf9a668fdf45fc09002726ba7160e713ed79dddcd20171308273f1a2f1012103cb3e00561c3439ccbacc033a72e0513bcfabff8826de0bc651d661991ade6171049e1600',
+                         tx_from_str('64XF-8+PM6*4IYN-QWW$B2QLNW+:C8-$I$-+T:L.6DKXTSWSFFONDP1J/MOS3SPK0-SYVW38U9.3+A1/*2HTHQTJGP79LVEK-IITQJ1H.C/X$NSOV$8DWR6JAFWXD*LX4-EN0.BDOF+PPYPH16$NM1H.-MAA$V1SCP0Q.6Y5FR822S6K-.5K5F.Z4Q:0SDRG-4GEBLAO4W9Z*H-$1-KDYAFOGF675W0:CK5M1LT92IG:3X60P3GKPM:X2$SP5A7*LT9$-TTEG0/DRZYV$7B4ADL9CVS5O7YG.J64HLZ24MVKO/-GV:V.T/L$D3VQ:MR8--44HK8W'))
+
     def test_get_address_from_output_script(self):
         # the inverse of this test is in test_bitcoin: test_address_to_script
         addr_from_script = lambda script: transaction.get_address_from_output_script(bfh(script))

electrum/transaction.py

@@ -39,7 +39,7 @@ from .bitcoin import (TYPE_ADDRESS, TYPE_PUBKEY, TYPE_SCRIPT, hash_160,
                       hash160_to_p2sh, hash160_to_p2pkh, hash_to_segwit_addr,
                       hash_encode, var_int, TOTAL_COIN_SUPPLY_LIMIT_IN_BTC, COIN,
                       push_script, int_to_hex, push_script, b58_address_to_hash160,
-                      opcodes, add_number_to_script)
+                      opcodes, add_number_to_script, base_decode)
 from .crypto import sha256d
 from .keystore import xpubkey_to_address, xpubkey_to_pubkey
 
@@ -1185,19 +1185,26 @@ class Transaction:
         return out
 
 
-def tx_from_str(txt):
-    "json or raw hexadecimal"
-    import json
+def tx_from_str(txt: str) -> str:
+    """Sanitizes tx-describing input (json or raw hex or base43) into
+    raw hex transaction."""
+    assert isinstance(txt, str), f"txt must be str, not {type(txt)}"
     txt = txt.strip()
     if not txt:
         raise ValueError("empty string")
+    # try hex
     try:
         bfh(txt)
-        is_hex = True
-    except:
-        is_hex = False
-    if is_hex:
         return txt
+    except:
+        pass
+    # try base43
+    try:
+        return base_decode(txt, length=None, base=43).hex()
+    except:
+        pass
+    # try json
+    import json
     tx_dict = json.loads(str(txt))
     assert "hex" in tx_dict.keys()
     return tx_dict["hex"]