diff options
Diffstat (limited to 'contracts/ens/cid.go')
-rw-r--r-- | contracts/ens/cid.go | 121 |
1 files changed, 121 insertions, 0 deletions
diff --git a/contracts/ens/cid.go b/contracts/ens/cid.go new file mode 100644 index 000000000..fae9bfd0a --- /dev/null +++ b/contracts/ens/cid.go @@ -0,0 +1,121 @@ +// Copyright 2016 The go-ethereum Authors +// This file is part of the go-ethereum library. +// +// The go-ethereum library is free software: you can redistribute it and/or modify +// it under the terms of the GNU Lesser General Public License as published by +// the Free Software Foundation, either version 3 of the License, or +// (at your option) any later version. +// +// The go-ethereum library is distributed in the hope that it will be useful, +// but WITHOUT ANY WARRANTY; without even the implied warranty of +// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the +// GNU Lesser General Public License for more details. +// +// You should have received a copy of the GNU Lesser General Public License +// along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>. + +package ens + +import ( + "encoding/binary" + "errors" + "fmt" + + "github.com/ethereum/go-ethereum/common" +) + +const ( + cidv1 = 0x1 + + nsIpfs = 0xe3 + nsSwarm = 0xe4 + + swarmTypecode = 0xfa //swarm manifest, see https://github.com/multiformats/multicodec/blob/master/table.csv + swarmHashtype = 0xd6 // BMT, see https://github.com/multiformats/multicodec/blob/master/table.csv + + hashLength = 32 +) + +// deocodeEIP1577ContentHash decodes a chain-stored content hash from an ENS record according to EIP-1577 +// a successful decode will result the different parts of the content hash in accordance to the CID spec +// Note: only CIDv1 is supported +func decodeEIP1577ContentHash(buf []byte) (storageNs, contentType, hashType, hashLength uint64, hash []byte, err error) { + if len(buf) < 10 { + return 0, 0, 0, 0, nil, errors.New("buffer too short") + } + + storageNs, n := binary.Uvarint(buf) + + buf = buf[n:] + vers, n := binary.Uvarint(buf) + + if vers != 1 { + return 0, 0, 0, 0, nil, fmt.Errorf("expected cid v1, got: %d", vers) + } + buf = buf[n:] + contentType, n = binary.Uvarint(buf) + + buf = buf[n:] + hashType, n = binary.Uvarint(buf) + + buf = buf[n:] + hashLength, n = binary.Uvarint(buf) + + hash = buf[n:] + + if len(hash) != int(hashLength) { + return 0, 0, 0, 0, nil, errors.New("hash length mismatch") + } + return storageNs, contentType, hashType, hashLength, hash, nil +} + +func extractContentHash(buf []byte) (common.Hash, error) { + storageNs, _ /*contentType*/, _ /* hashType*/, decodedHashLength, hashBytes, err := decodeEIP1577ContentHash(buf) + + if err != nil { + return common.Hash{}, err + } + + if storageNs != nsSwarm { + return common.Hash{}, errors.New("unknown storage system") + } + + //todo: for the time being we implement loose enforcement for the EIP rules until ENS manager is updated + /*if contentType != swarmTypecode { + return common.Hash{}, errors.New("unknown content type") + } + + if hashType != swarmHashtype { + return common.Hash{}, errors.New("unknown multihash type") + }*/ + + if decodedHashLength != hashLength { + return common.Hash{}, errors.New("odd hash length, swarm expects 32 bytes") + } + + if len(hashBytes) != int(hashLength) { + return common.Hash{}, errors.New("hash length mismatch") + } + + return common.BytesToHash(buf), nil +} + +func EncodeSwarmHash(hash common.Hash) ([]byte, error) { + var cidBytes []byte + var headerBytes = []byte{ + nsSwarm, //swarm namespace + cidv1, // CIDv1 + swarmTypecode, // swarm hash + swarmHashtype, // swarm bmt hash + hashLength, //hash length. 32 bytes + } + + varintbuf := make([]byte, binary.MaxVarintLen64) + for _, v := range headerBytes { + n := binary.PutUvarint(varintbuf, uint64(v)) + cidBytes = append(cidBytes, varintbuf[:n]...) + } + + cidBytes = append(cidBytes, hash[:]...) + return cidBytes, nil +} |