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| 1 | +// Copyright (c) 2017 Takatoshi Nakagawa |
| 2 | +// Copyright (c) 2019 Google LLC |
| 3 | +// |
| 4 | +// Permission is hereby granted, free of charge, to any person obtaining a copy |
| 5 | +// of this software and associated documentation files (the "Software"), to deal |
| 6 | +// in the Software without restriction, including without limitation the rights |
| 7 | +// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell |
| 8 | +// copies of the Software, and to permit persons to whom the Software is |
| 9 | +// furnished to do so, subject to the following conditions: |
| 10 | +// |
| 11 | +// The above copyright notice and this permission notice shall be included in |
| 12 | +// all copies or substantial portions of the Software. |
| 13 | +// |
| 14 | +// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR |
| 15 | +// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, |
| 16 | +// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE |
| 17 | +// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER |
| 18 | +// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, |
| 19 | +// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN |
| 20 | +// THE SOFTWARE. |
| 21 | + |
| 22 | +// Package bech32 is a modified version of the reference implementation of BIP173. |
| 23 | +package bech32 |
| 24 | + |
| 25 | +import ( |
| 26 | + "fmt" |
| 27 | + "strings" |
| 28 | +) |
| 29 | + |
| 30 | +var charset = "qpzry9x8gf2tvdw0s3jn54khce6mua7l" |
| 31 | + |
| 32 | +var generator = []uint32{0x3b6a57b2, 0x26508e6d, 0x1ea119fa, 0x3d4233dd, 0x2a1462b3} |
| 33 | + |
| 34 | +func polymod(values []byte) uint32 { |
| 35 | + chk := uint32(1) |
| 36 | + for _, v := range values { |
| 37 | + top := chk >> 25 |
| 38 | + chk = (chk & 0x1ffffff) << 5 |
| 39 | + chk = chk ^ uint32(v) |
| 40 | + for i := 0; i < 5; i++ { |
| 41 | + bit := top >> i & 1 |
| 42 | + if bit == 1 { |
| 43 | + chk ^= generator[i] |
| 44 | + } |
| 45 | + } |
| 46 | + } |
| 47 | + return chk |
| 48 | +} |
| 49 | + |
| 50 | +func hrpExpand(hrp string) []byte { |
| 51 | + h := []byte(strings.ToLower(hrp)) |
| 52 | + var ret []byte |
| 53 | + for _, c := range h { |
| 54 | + ret = append(ret, c>>5) |
| 55 | + } |
| 56 | + ret = append(ret, 0) |
| 57 | + for _, c := range h { |
| 58 | + ret = append(ret, c&31) |
| 59 | + } |
| 60 | + return ret |
| 61 | +} |
| 62 | + |
| 63 | +func verifyChecksum(hrp string, data []byte) bool { |
| 64 | + return polymod(append(hrpExpand(hrp), data...)) == 1 |
| 65 | +} |
| 66 | + |
| 67 | +func createChecksum(hrp string, data []byte) []byte { |
| 68 | + values := append(hrpExpand(hrp), data...) |
| 69 | + values = append(values, []byte{0, 0, 0, 0, 0, 0}...) |
| 70 | + mod := polymod(values) ^ 1 |
| 71 | + ret := make([]byte, 6) |
| 72 | + for p := range ret { |
| 73 | + shift := 5 * (5 - p) |
| 74 | + ret[p] = byte(mod>>shift) & 31 |
| 75 | + } |
| 76 | + return ret |
| 77 | +} |
| 78 | + |
| 79 | +func convertBits(data []byte, frombits, tobits byte, pad bool) ([]byte, error) { |
| 80 | + var ret []byte |
| 81 | + acc := uint32(0) |
| 82 | + bits := byte(0) |
| 83 | + maxv := byte(1<<tobits - 1) |
| 84 | + for idx, value := range data { |
| 85 | + if value>>frombits != 0 { |
| 86 | + return nil, fmt.Errorf("invalid data range: data[%d]=%d (frombits=%d)", idx, value, frombits) |
| 87 | + } |
| 88 | + acc = acc<<frombits | uint32(value) |
| 89 | + bits += frombits |
| 90 | + for bits >= tobits { |
| 91 | + bits -= tobits |
| 92 | + ret = append(ret, byte(acc>>bits)&maxv) |
| 93 | + } |
| 94 | + } |
| 95 | + if pad { |
| 96 | + if bits > 0 { |
| 97 | + ret = append(ret, byte(acc<<(tobits-bits))&maxv) |
| 98 | + } |
| 99 | + } else if bits >= frombits { |
| 100 | + return nil, fmt.Errorf("illegal zero padding") |
| 101 | + } else if byte(acc<<(tobits-bits))&maxv != 0 { |
| 102 | + return nil, fmt.Errorf("non-zero padding") |
| 103 | + } |
| 104 | + return ret, nil |
| 105 | +} |
| 106 | + |
| 107 | +// Encode encodes the HRP and a bytes slice to Bech32. If the HRP is uppercase, |
| 108 | +// the output will be uppercase. |
| 109 | +func Encode(hrp string, data []byte) (string, error) { |
| 110 | + values, err := convertBits(data, 8, 5, true) |
| 111 | + if err != nil { |
| 112 | + return "", err |
| 113 | + } |
| 114 | + if len(hrp)+len(values)+7 > 90 { |
| 115 | + return "", fmt.Errorf("too long: hrp length=%d, data length=%d", len(hrp), len(values)) |
| 116 | + } |
| 117 | + if len(hrp) < 1 { |
| 118 | + return "", fmt.Errorf("invalid HRP: %q", hrp) |
| 119 | + } |
| 120 | + for p, c := range hrp { |
| 121 | + if c < 33 || c > 126 { |
| 122 | + return "", fmt.Errorf("invalid HRP character: hrp[%d]=%d", p, c) |
| 123 | + } |
| 124 | + } |
| 125 | + if strings.ToUpper(hrp) != hrp && strings.ToLower(hrp) != hrp { |
| 126 | + return "", fmt.Errorf("mixed case HRP: %q", hrp) |
| 127 | + } |
| 128 | + lower := strings.ToLower(hrp) == hrp |
| 129 | + hrp = strings.ToLower(hrp) |
| 130 | + var ret strings.Builder |
| 131 | + ret.WriteString(hrp) |
| 132 | + ret.WriteString("1") |
| 133 | + for _, p := range values { |
| 134 | + ret.WriteByte(charset[p]) |
| 135 | + } |
| 136 | + for _, p := range createChecksum(hrp, values) { |
| 137 | + ret.WriteByte(charset[p]) |
| 138 | + } |
| 139 | + if lower { |
| 140 | + return ret.String(), nil |
| 141 | + } |
| 142 | + return strings.ToUpper(ret.String()), nil |
| 143 | +} |
| 144 | + |
| 145 | +// Decode decodes a Bech32 string. If the string is uppercase, the HRP will be uppercase. |
| 146 | +func Decode(s string) (hrp string, data []byte, err error) { |
| 147 | + if len(s) > 90 { |
| 148 | + return "", nil, fmt.Errorf("too long: len=%d", len(s)) |
| 149 | + } |
| 150 | + if strings.ToLower(s) != s && strings.ToUpper(s) != s { |
| 151 | + return "", nil, fmt.Errorf("mixed case") |
| 152 | + } |
| 153 | + pos := strings.LastIndex(s, "1") |
| 154 | + if pos < 1 || pos+7 > len(s) { |
| 155 | + return "", nil, fmt.Errorf("separator '1' at invalid position: pos=%d, len=%d", pos, len(s)) |
| 156 | + } |
| 157 | + hrp = s[:pos] |
| 158 | + for p, c := range hrp { |
| 159 | + if c < 33 || c > 126 { |
| 160 | + return "", nil, fmt.Errorf("invalid character human-readable part: s[%d]=%d", p, c) |
| 161 | + } |
| 162 | + } |
| 163 | + s = strings.ToLower(s) |
| 164 | + for p, c := range s[pos+1:] { |
| 165 | + d := strings.IndexRune(charset, c) |
| 166 | + if d == -1 { |
| 167 | + return "", nil, fmt.Errorf("invalid character data part: s[%d]=%v", p, c) |
| 168 | + } |
| 169 | + data = append(data, byte(d)) |
| 170 | + } |
| 171 | + if !verifyChecksum(hrp, data) { |
| 172 | + return "", nil, fmt.Errorf("invalid checksum") |
| 173 | + } |
| 174 | + data, err = convertBits(data[:len(data)-6], 5, 8, false) |
| 175 | + if err != nil { |
| 176 | + return "", nil, err |
| 177 | + } |
| 178 | + return hrp, data, nil |
| 179 | +} |
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