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server/asset/btc: require zpub, but offer xpub conversion
For a server operator to accept BTC for the registration fee, it is currently necessary to provide an extended public key with the "xpub" prefix. This is because the btcutil/hdkeychain package only recognizes such xpub strings as being from a given network, otherwise the net/version bytes are unknown. However, the derived fee addresses are P2WPKH. The potential trouble is that wallets that generate native segwit addresses tend to return "zpub"-prefixed extended public key encodings in following BIP-84 (vpub for testnet and regnet). I have verified that Electrum does this if the wallet was created as native segwit, and Exodus actually exports both an xpub and zpub that do not seem to correspond to the same extended key (two separate derivation paths) making it potentially ill-advised to use the xpub for segwit addresses! Prior to this PR, an operator with a wallet that provides a zpub would have to convert to an xpub. This is not hard (see here), but it is confusing and unnecessary since the dex software can do it. Further, if they got an xpub from a non-segwit wallet or non-segwit path, it's possibly they will have to go to some trouble to claim funds sent to segwit addresses derived from this extended key. To address this, this PR now requires the key to be with a "zpub" prefix. Also, if an "xpub" is provided, it will convert it to "zpub" and return an error with this string so the operator is aware that segwit addresses will be generated if they decide to use that zpub.
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,138 @@ | ||
| // This code is available on the terms of the project LICENSE.md file, | ||
| // also available online at https://blueoakcouncil.org/license/1.0.0. | ||
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| package btc | ||
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| import ( | ||
| "bytes" | ||
| "encoding/binary" | ||
| "strings" | ||
| "testing" | ||
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| "decred.org/dcrdex/server/asset" | ||
| "github.com/btcsuite/btcd/chaincfg" | ||
| "github.com/btcsuite/btcd/wire" | ||
| "github.com/btcsuite/btcutil/hdkeychain" | ||
| ) | ||
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| // Dummy keyIndexer since there is no DB or need to coordinate withother | ||
| // goroutines. | ||
| type keyIndexer struct { | ||
| idx map[string]uint32 | ||
| } | ||
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| func newKeyIndexer() *keyIndexer { | ||
| return &keyIndexer{make(map[string]uint32)} | ||
| } | ||
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| func (ki *keyIndexer) KeyIndex(xpub string) (uint32, error) { | ||
| return ki.idx[xpub], nil | ||
| } | ||
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| func (ki *keyIndexer) SetKeyIndex(idx uint32, xpub string) error { | ||
| ki.idx[xpub] = idx | ||
| return nil | ||
| } | ||
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| var _ asset.KeyIndexer = (*keyIndexer)(nil) | ||
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| func TestAddressDeriver(t *testing.T) { | ||
| var x uint32 = 0x0488b21e | ||
| x2 := binary.BigEndian.Uint32([]byte{0x04, 0x88, 0xb2, 0x1e}) | ||
| if x != x2 { | ||
| t.Fatalf("%d != %d", x, x2) | ||
| } | ||
|
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| params := &chaincfg.MainNetParams | ||
| // zpub := "zpub6nKbQwE3qUJUhehpUf2sETXY1v2mm1VM5ou4xdM3PPMudQfuo8XC3DPM3esiGCRhT1JBubsydS2UFM2eX8Uh2tSx6FhDY3GKQGESmbARSmR" | ||
| // xpubWant := "xpub68f4obtDY7DX14KaowTcpHLXfyjssmWMFardPqZGdNc9XD3THpC4o6551ExYGP7rdj4aQegri7KNUmoX5jefSR5kMaJNNDdLrp79zQBSGaK" | ||
| zpub := "zpub6r6v49qBjybMzg17LsqFDYDG3oYssB5GkQ4BdQtjCDkSeBPAgXxHBYXgNGy3LxfHwf5JwvkJTBqHHjkXKdwheZdtLKdcXCU1SMkzryt1evp" | ||
| xpubWant := "xpub6CSPSpVMScWQJ5csgAFzoN2FhsFyyw6GvB1k4d6xSCzgXykiBDd9wRDQKs3sM9MT8NqhSyZBXs8BXAXPtF7g46GgbeEmMNq2tudi5k68MjJ" | ||
| // params := &chaincfg.TestNet3Params | ||
| // zpub := "vpub5UpDTWU6Nuj9uuU5TZnxjS97SAjKwY4UiLvvnYNRC6vmvbDa5toZRG1BkqCnLSRmNYuLuqLDPtdDq6YvELoMUSPjVSFTsX1H42kabkJDwWD" | ||
| // xpubWant := "tpubD8rNb5dcPYmZtJ3AaUMJMXfV7E7spAYY6CZfhtDLJ2SRn5WjfRymopzJ3HCjrkgqyjfs2N3CrKANHrGf4bUcxMDEHiPcisJVBSUH8wNhdoA" | ||
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| net := params.Net | ||
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| // P2PWKH extended key prefix is: zpub on mainnet, vpub on regnet/testnet3 | ||
| var xpubPrefix, zpubPrefix string | ||
| switch net { | ||
| case wire.MainNet: | ||
| xpubPrefix = "xpub" | ||
| zpubPrefix = "zpub" | ||
| case wire.TestNet, wire.TestNet3: | ||
| xpubPrefix = "tpub" | ||
| zpubPrefix = "vpub" | ||
| } | ||
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| key, err := hdkeychain.NewKeyFromString(zpub) | ||
| if err != nil { | ||
| t.Fatalf("error parsing master pubkey: %v", err) | ||
| } | ||
| if key.IsPrivate() { | ||
| t.Fatal("that's a private key") | ||
| } | ||
| if key.IsForNet(params) { | ||
| t.Fatal("btcsuite's hdkeychain recognized our zpub!") | ||
| } | ||
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| vers := key.Version() | ||
| prefix := pubVerPrefix(vers, net) | ||
| if prefix == "" { | ||
| t.Fatalf("invalid prefix for version bytes %x", vers) | ||
| } | ||
| if prefix != zpubPrefix { | ||
| t.Fatalf("unexpected prefix %q for version bytes %x", prefix, vers) | ||
| } | ||
| if v := pubPrefixVer(prefix, net); !bytes.Equal(v, vers) { | ||
| t.Fatal("inconsistent version") | ||
| } | ||
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| key.SetNet(params) // params uses xpub version bytes | ||
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| vers = key.Version() | ||
| prefix = pubVerPrefix(vers, net) | ||
| if prefix == "" { | ||
| t.Fatalf("bad prefix for version bytes %x", vers) | ||
| } | ||
| if prefix != xpubPrefix { | ||
| t.Fatalf("unexpected prefix %q for version bytes %x", prefix, vers) | ||
| } | ||
| if v := pubPrefixVer(prefix, net); !bytes.Equal(v, vers) { | ||
| t.Fatal("inconsistent version") | ||
| } | ||
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| xpub := key.String() | ||
| if xpub != xpubWant { | ||
| t.Fatal(xpub, " != ", xpubWant) | ||
| } | ||
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| ki := newKeyIndexer() | ||
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| // NewAddressDeriver should not like the xpub, and suggest the zpub. | ||
| _, _, err = NewAddressDeriver(xpub, ki, params) | ||
| if err == nil { | ||
| t.Fatal("no error from NewAddressDeriver for an xpub prefixed key") | ||
| } | ||
| if !strings.Contains(err.Error(), zpub) { | ||
| t.Fatalf("NewAddressDeriver should have suggested the corresponding zpub, said: %q", err.Error()) | ||
| } | ||
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| // Should work with the zpub. | ||
| ad, _, err := NewAddressDeriver(zpub, ki, params) | ||
| if err != nil { | ||
| t.Fatal(err) | ||
| } | ||
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| for i := 0; i < 10; i++ { | ||
| addr, err := ad.NextAddress() | ||
| if err != nil { | ||
| t.Fatal(err) | ||
| } | ||
| t.Log(addr) | ||
| } | ||
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| if ad.next != 10 { | ||
| t.Fatal(ad.next) | ||
| } | ||
| } |