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Diffstat (limited to 'taler-kotlin-android/src/main/java/net/taler/common/Bech32.kt')
| -rw-r--r-- | taler-kotlin-android/src/main/java/net/taler/common/Bech32.kt | 282 |
1 files changed, 282 insertions, 0 deletions
diff --git a/taler-kotlin-android/src/main/java/net/taler/common/Bech32.kt b/taler-kotlin-android/src/main/java/net/taler/common/Bech32.kt new file mode 100644 index 0000000..4b77f85 --- /dev/null +++ b/taler-kotlin-android/src/main/java/net/taler/common/Bech32.kt @@ -0,0 +1,282 @@ +/* + * This file is part of GNU Taler + * (C) 2020 Taler Systems S.A. + * + * GNU Taler is free software; you can redistribute it and/or modify it under the + * terms of the GNU General Public License as published by the Free Software + * Foundation; either version 3, or (at your option) any later version. + * + * GNU Taler 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 General Public License for more details. + * + * You should have received a copy of the GNU General Public License along with + * GNU Taler; see the file COPYING. If not, see <http://www.gnu.org/licenses/> + */ + +// Copyright (c) 2020 Figure Technologies Inc. +// The contents of this file were derived from an implementation +// by the btcsuite developers https://github.com/btcsuite/btcutil. + +// Copyright (c) 2017 The btcsuite developers +// Use of this source code is governed by an ISC +// license that can be found in the LICENSE file. + +// modified version of https://gist.github.com/iramiller/4ebfcdfbc332a9722c4a4abeb4e16454 + +package net.taler.common + +import java.util.Locale.ROOT +import kotlin.experimental.and +import kotlin.experimental.or + +infix fun Int.min(b: Int): Int = b.takeIf { this > b } ?: this +infix fun UByte.shl(bitCount: Int) = ((this.toInt() shl bitCount) and 0xff).toUByte() +infix fun UByte.shr(bitCount: Int) = (this.toInt() shr bitCount).toUByte() + +/** + * Bech32 Data encoding instance containing data for encoding as well as a human readable prefix + */ +data class Bech32Data(val hrp: String, val fiveBitData: ByteArray) { + + /** + * The encapsulated data as typical 8bit bytes. + */ + val data = Bech32.convertBits(fiveBitData, 5, 8, false) + + /** + * Address is the Bech32 encoded value of the data prefixed with the human readable portion and + * protected by an appended checksum. + */ + val address = Bech32.encode(hrp, fiveBitData) + + /** + * Checksum for encapsulated data + hrp + */ + val checksum = Bech32.checksum(this.hrp, this.fiveBitData.toTypedArray()) + + /** + * The Bech32 Address toString prints state information for debugging purposes. + * @see address() for the bech32 encoded address string output. + */ + override fun toString(): String { + return "bech32 : ${this.address}\nhuman: ${this.hrp} \nbytes" + } + + override fun equals(other: Any?): Boolean { + if (this === other) return true + if (javaClass != other?.javaClass) return false + + other as Bech32Data + + if (hrp != other.hrp) return false + if (!fiveBitData.contentEquals(other.fiveBitData)) return false + if (!data.contentEquals(other.data)) return false + if (address != other.address) return false + if (!checksum.contentEquals(other.checksum)) return false + + return true + } + + override fun hashCode(): Int { + var result = hrp.hashCode() + result = 31 * result + fiveBitData.contentHashCode() + result = 31 * result + data.contentHashCode() + result = 31 * result + address.hashCode() + result = 31 * result + checksum.contentHashCode() + return result + } +} + +/** + * BIP173 compliant processing functions for handling Bech32 encoding for addresses + */ +class Bech32 { + + companion object { + const val CHECKSUM_SIZE = 6 + private const val MIN_VALID_LENGTH = 8 + private const val MAX_VALID_LENGTH = 90 + const val MIN_VALID_CODEPOINT = 33 + private const val MAX_VALID_CODEPOINT = 126 + + const val charset = "qpzry9x8gf2tvdw0s3jn54khce6mua7l" + private val gen = intArrayOf(0x3b6a57b2, 0x26508e6d, 0x1ea119fa, 0x3d4233dd, 0x2a1462b3) + + fun generateFakeSegwitAddress(reservePub: String?, addr: String): List<String> { + if (reservePub == null || reservePub.isEmpty()) return listOf() + val pub = CyptoUtils.decodeCrock(reservePub) + if (pub.size != 32) return listOf() + + val firstRnd = pub.copyOfRange(0, 4) + val secondRnd = pub.copyOfRange(0, 4) + + firstRnd[0] = firstRnd[0].and(0b0111_1111) + secondRnd[0] = secondRnd[0].or(0b1000_0000.toByte()) + + val firstPart = ByteArray(20) + firstRnd.copyInto(firstPart, 0, 0, 4) + pub.copyInto(firstPart, 4, 0, 16) + + val secondPart = ByteArray(20) + secondRnd.copyInto(secondPart, 0, 0, 4) + pub.copyInto(secondPart, 4, 16, 32) + + val zero = ByteArray(1) + zero[0] = 0 + val hrp = when { + addr[0] == 'b' && addr[1] == 'c' && addr[2] == 'r' && addr[3] == 't' -> "bcrt" + addr[0] == 't' && addr[1] == 'b' -> "tb" + addr[0] == 'b' && addr[1] == 'c' -> "bc" + else -> throw Error("unknown bitcoin net") + } + + return listOf( + Bech32Data(hrp, zero + convertBits(firstPart, 8, 5, true)).address, + Bech32Data(hrp, zero + convertBits(secondPart, 8, 5, true)).address, + ) + } + + /** + * Decodes a Bech32 String + */ + fun decode(bech32: String): Bech32Data { + require(bech32.length in MIN_VALID_LENGTH..MAX_VALID_LENGTH) { "invalid bech32 string length" } + require(bech32.toCharArray() + .none { c -> c.code < MIN_VALID_CODEPOINT || c.code > MAX_VALID_CODEPOINT }) + { + "invalid character in bech32: ${ + bech32.toCharArray().map { c -> c.code } + .filter { c -> c < MIN_VALID_CODEPOINT || c > MAX_VALID_CODEPOINT } + }" + } + + require(bech32 == bech32.lowercase(ROOT) || bech32 == bech32.uppercase(ROOT)) + { "bech32 must be either all upper or lower case" } + require(bech32.substring(1).dropLast(CHECKSUM_SIZE) + .contains('1')) { "invalid index of '1'" } + + val hrp = bech32.substringBeforeLast('1').lowercase(ROOT) + val dataString = bech32.substringAfterLast('1').lowercase(ROOT) + + require(dataString.toCharArray() + .all { c -> charset.contains(c) }) { "invalid data encoding character in bech32" } + + val dataBytes = dataString.map { c -> charset.indexOf(c).toByte() }.toByteArray() + val checkBytes = + dataString.takeLast(CHECKSUM_SIZE).map { c -> charset.indexOf(c).toByte() } + .toByteArray() + + val actualSum = checksum(hrp, dataBytes.dropLast(CHECKSUM_SIZE).toTypedArray()) + require(1 == polymod(expandHrp(hrp).plus(dataBytes.map { d -> d.toInt() }))) { "checksum failed: $checkBytes != $actualSum" } + + return Bech32Data(hrp, dataBytes.dropLast(CHECKSUM_SIZE).toByteArray()) + } + + /** + * ConvertBits regroups bytes with toBits set based on reading groups of bits as a continuous stream group by fromBits. + * This process is used to convert from base64 (from 8) to base32 (to 5) or the inverse. + */ + fun convertBits(data: ByteArray, fromBits: Int, toBits: Int, pad: Boolean): ByteArray { + require(fromBits in 1..8 && toBits in 1..8) { "only bit groups between 1 and 8 are supported" } + + // resulting bytes with each containing the toBits bits from the input set. + val regrouped = arrayListOf<Byte>() + + var nextByte = 0.toUByte() + var filledBits = 0 + + data.forEach { d -> + // discard unused bits. + var b = (d.toUByte() shl (8 - fromBits)) + + // How many bits remain to extract from input data. + var remainFromBits = fromBits + + while (remainFromBits > 0) { + // How many bits remain to be copied in + val remainToBits = toBits - filledBits + + // we extract the remaining bits unless that is more than we need. + val toExtract = + remainFromBits.takeUnless { remainToBits < remainFromBits } ?: remainToBits + check(toExtract >= 0) { "extract should be positive" } + + // move existing bits to the left to make room for bits toExtract, copy in bits to extract + nextByte = (nextByte shl toExtract) or (b shr (8 - toExtract)) + + // discard extracted bits and update position counters + b = b shl toExtract + remainFromBits -= toExtract + filledBits += toExtract + + // if we have a complete group then reset. + if (filledBits == toBits) { + regrouped.add(nextByte.toByte()) + filledBits = 0 + nextByte = 0.toUByte() + } + } + } + + // pad any unfinished groups as required + if (pad && filledBits > 0) { + nextByte = nextByte shl (toBits - filledBits) + regrouped.add(nextByte.toByte()) + filledBits = 0 + nextByte = 0.toUByte() + } + + return regrouped.toByteArray() + } + + /** + * Encodes data 5-bit bytes (data) with a given human readable portion (hrp) into a bech32 string. + * @see convertBits for conversion or ideally use the Bech32Data extension functions + */ + fun encode(hrp: String, fiveBitData: ByteArray): String { + return (fiveBitData.plus(checksum(hrp, fiveBitData.toTypedArray())) + .map { b -> charset[b.toInt()] }).joinToString("", hrp + "1") + } + + /** + * Calculates a bech32 checksum based on BIP 173 specification + */ + fun checksum(hrp: String, data: Array<Byte>): ByteArray { + val values = expandHrp(hrp) + .plus(data.map { d -> d.toInt() }) + .plus(Array(6) { 0 }.toIntArray()) + + val poly = polymod(values) xor 1 + + return (0..5).map { + ((poly shr (5 * (5 - it))) and 31).toByte() + }.toByteArray() + } + + /** + * Expands the human readable prefix per BIP173 for Checksum encoding + */ + private fun expandHrp(hrp: String) = + hrp.map { c -> c.code shr 5 } + .plus(0) + .plus(hrp.map { c -> c.code and 31 }) + .toIntArray() + + /** + * Polynomial division function for checksum calculation. For details see BIP173 + */ + fun polymod(values: IntArray): Int { + var chk = 1 + return values.map { num -> + val b = chk shr 25 + chk = ((chk and 0x1ffffff) shl 5) xor num + (0..4).map { + if (((b shr it) and 1) == 1) { + chk = chk xor gen[it] + } + } + }.let { chk } + } + } +}
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