Merge branch 'bech32' of https://github.com/matheusd/dcrd into matheu…

…sd-bech32

bech32/README.md

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+bech32
+==========
+
+[![Build Status](http://img.shields.io/travis/decred/dcrd/bech32.svg)](https://travis-ci.org/decred/dcrd/bech32)
+[![ISC License](http://img.shields.io/badge/license-ISC-blue.svg)](http://copyfree.org)
+[![GoDoc](http://img.shields.io/badge/godoc-reference-blue.svg)](http://godoc.org/github.com/decred/dcrd/bech32)
+
+Package bech32 provides a Go implementation of the bech32 format specified in
+[BIP 173](https://github.com/bitcoin/bips/blob/master/bip-0173.mediawiki).
+
+Test vectors from BIP 173 are added to ensure compatibility with the BIP.
+
+## Installation and Updating
+
+```bash
+$ go get -u github.com/decred/dcrd/bech32
+```
+
+## Examples
+
+* [Bech32 decode Example](http://godoc.org/github.com/decred/dcrd/bech32#example-Bech32Decode)
+  Demonstrates how to decode a bech32 encoded string.
+* [Bech32 encode Example](http://godoc.org/github.com/decred/dcrd/bech32#example-BechEncode)
+  Demonstrates how to encode data into a bech32 string.
+
+## License
+
+Package bech32 is licensed under the [copyfree](http://copyfree.org) ISC
+License.

bech32/bech32.go

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+// Copyright (c) 2017 The btcsuite developers
+// Copyright (c) 2019 The Decred developers
+// Use of this source code is governed by an ISC
+// license that can be found in the LICENSE file.
+
+package bech32
+
+import (
+	"strings"
+)
+
+// charset is the set of characters used in the data section of bech32 strings.
+// Note that this is ordered, such that for a given charset[i], i is the binary
+// value of the character.
+const charset = "qpzry9x8gf2tvdw0s3jn54khce6mua7l"
+
+// gen encodes the generator polynomial for the bech32 BCH checksum.
+var gen = []int{0x3b6a57b2, 0x26508e6d, 0x1ea119fa, 0x3d4233dd, 0x2a1462b3}
+
+// toBytes converts each character in the string 'chars' to the value of the
+// index of the correspoding character in 'charset'.
+func toBytes(chars string) ([]byte, error) {
+	decoded := make([]byte, 0, len(chars))
+	for i := 0; i < len(chars); i++ {
+		index := strings.IndexByte(charset, chars[i])
+		if index < 0 {
+			return nil, ErrNonCharsetChar(chars[i])
+		}
+		decoded = append(decoded, byte(index))
+	}
+	return decoded, nil
+}
+
+// bech32Polymod calculates the BCH checksum for a given hrp, values and
+// checksum data. Checksum is optional, and if nil a 0 checksum is assumed.
+//
+// Values and checksum (if provided) MUST be encoded as 5 bits per element (base
+// 32), otherwise the results are undefined.
+//
+// For more details on the polymod calculation, please refer to BIP 173.
+func bech32Polymod(hrp string, values, checksum []byte) int {
+	chk := 1
+
+	// Account for the high bits of the HRP in the checksum.
+	for i := 0; i < len(hrp); i++ {
+		b := chk >> 25
+		hiBits := int(hrp[i]) >> 5
+		chk = (chk&0x1ffffff)<<5 ^ hiBits
+		for i := 0; i < 5; i++ {
+			if (b>>uint(i))&1 == 1 {
+				chk ^= gen[i]
+			}
+		}
+	}
+
+	// Account for the separator (0) between high and low bits of the HRP.
+	// x^0 == x, so we eliminate the redundant xor used in the other rounds.
+	b := chk >> 25
+	chk = (chk & 0x1ffffff) << 5
+	for i := 0; i < 5; i++ {
+		if (b>>uint(i))&1 == 1 {
+			chk ^= gen[i]
+		}
+	}
+
+	// Account for the low bits of the HRP.
+	for i := 0; i < len(hrp); i++ {
+		b := chk >> 25
+		loBits := int(hrp[i]) & 31
+		chk = (chk&0x1ffffff)<<5 ^ loBits
+		for i := 0; i < 5; i++ {
+			if (b>>uint(i))&1 == 1 {
+				chk ^= gen[i]
+			}
+		}
+	}
+
+	// Account for the values.
+	for _, v := range values {
+		b := chk >> 25
+		chk = (chk&0x1ffffff)<<5 ^ int(v)
+		for i := 0; i < 5; i++ {
+			if (b>>uint(i))&1 == 1 {
+				chk ^= gen[i]
+			}
+		}
+	}
+
+	if checksum == nil {
+		// A nil checksum is used during encoding, so assume all bytes are zero.
+		// x^0 == x, so we eliminate the redundant xor used in the other rounds.
+		for v := 0; v < 6; v++ {
+			b := chk >> 25
+			chk = (chk & 0x1ffffff) << 5
+			for i := 0; i < 5; i++ {
+				if (b>>uint(i))&1 == 1 {
+					chk ^= gen[i]
+				}
+			}
+		}
+	} else {
+		// Checksum is provided during decoding, so use it.
+		for _, v := range checksum {
+			b := chk >> 25
+			chk = (chk&0x1ffffff)<<5 ^ int(v)
+			for i := 0; i < 5; i++ {
+				if (b>>uint(i))&1 == 1 {
+					chk ^= gen[i]
+				}
+			}
+		}
+	}
+
+	return chk
+}
+
+// writeBech32Checksum calculates the checksum data expected for a string that
+// will have the given hrp and payload data and writes it to the provided string
+// builder.
+//
+// The payload data MUST be encoded as a base 32 (5 bits per element) byte slice
+// and the hrp MUST only use the allowed character set (ascii chars between 33
+// and 126), otherwise the results are undefined.
+//
+// For more details on the checksum calculation, please refer to BIP 173.
+func writeBech32Checksum(hrp string, data []byte, bldr *strings.Builder) {
+	polymod := bech32Polymod(hrp, data, nil) ^ 1
+	for i := 0; i < 6; i++ {
+		b := byte((polymod >> uint(5*(5-i))) & 31)
+
+		// This can't fail, given we explicitly cap the previous b byte by the
+		// first 31 bits.
+		c := charset[b]
+		bldr.WriteByte(c)
+	}
+}
+
+// bech32VerifyChecksum verifies whether the bech32 string specified by the
+// provided hrp and payload data (encoded as 5 bits per element byte slice) has
+// the correct checksum suffix.
+//
+// Data MUST have more than 6 elements, otherwise this function panics.
+//
+// For more details on the checksum verification, please refer to BIP 173.
+func bech32VerifyChecksum(hrp string, data []byte) bool {
+	checksum := data[len(data)-6:]
+	values := data[:len(data)-6]
+	polymod := bech32Polymod(hrp, values, checksum)
+	return polymod == 1
+}
+
+// DecodeNoLimit decodes a bech32 encoded string, returning the human-readable
+// part and the data part excluding the checksum. This function does NOT
+// validate against the BIP-173 maximum length allowed for bech32 strings and
+// is meant for use in custom applications (such as lightning network payment
+// requests), NOT on-chain addresses.
+//
+// Note that the returned data is 5-bit (base32) encoded.
+func DecodeNoLimit(bech string) (string, []byte, error) {
+	// The minimum allowed size of a bech32 string is 8 characters, since it
+	// needs a non-empty HRP, a separator, and a 6 character checksum.
+	if len(bech) < 8 {
+		return "", nil, ErrInvalidLength(len(bech))
+	}
+
+	// Only	ASCII characters between 33 and 126 are allowed.
+	var hasLower, hasUpper bool
+	for i := 0; i < len(bech); i++ {
+		if bech[i] < 33 || bech[i] > 126 {
+			return "", nil, ErrInvalidCharacter(bech[i])
+		}
+
+		// The characters must be either all lowercase or all uppercase. Testing
+		// directly with ascii codes is safe here, given the previous test.
+		hasLower = hasLower || (bech[i] >= 97 && bech[i] <= 122)
+		hasUpper = hasUpper || (bech[i] >= 65 && bech[i] <= 90)
+		if hasLower && hasUpper {
+			return "", nil, ErrMixedCase{}
+		}
+	}
+
+	// Bech32 standard uses only the lowercase for of strings for checksum
+	// calculation.
+	if hasUpper {
+		bech = strings.ToLower(bech)
+	}
+
+	// The string is invalid if the last '1' is non-existent, it is the
+	// first character of the string (no human-readable part) or one of the
+	// last 6 characters of the string (since checksum cannot contain '1').
+	one := strings.LastIndexByte(bech, '1')
+	if one < 1 || one+7 > len(bech) {
+		return "", nil, ErrInvalidSeparatorIndex(one)
+	}
+
+	// The human-readable part is everything before the last '1'.
+	hrp := bech[:one]
+	data := bech[one+1:]
+
+	// Each character corresponds to the byte with value of the index in
+	// 'charset'.
+	decoded, err := toBytes(data)
+	if err != nil {
+		return "", nil, err
+	}
+
+	// Verify if the checksum (stored inside decoded[:]) is valid, given the
+	// previously decoded hrp.
+	if !bech32VerifyChecksum(hrp, decoded) {
+		// Invalid checksum. Calculate what it should have been, so that the
+		// error contains this information.
+
+		// Extract the payload bytes and actual checksum in the string.
+		actual := bech[len(bech)-6:]
+		payload := decoded[:len(decoded)-6]
+
+		// Calculate the expected checksum, given the hrp and payload data.
+		var expectedBldr strings.Builder
+		expectedBldr.Grow(6)
+		writeBech32Checksum(hrp, payload, &expectedBldr)
+		expected := expectedBldr.String()
+
+		err = ErrInvalidChecksum{
+			Expected: expected,
+			Actual:   actual,
+		}
+		return "", nil, err
+	}
+
+	// We exclude the last 6 bytes, which is the checksum.
+	return hrp, decoded[:len(decoded)-6], nil
+}
+
+// Decode decodes a bech32 encoded string, returning the human-readable part and
+// the data part excluding the checksum.
+//
+// Note that the returned data is 5-bit (base32) encoded.
+func Decode(bech string) (string, []byte, error) {
+	// The maximum allowed length for a bech32 string is 90.
+	if len(bech) > 90 {
+		return "", nil, ErrInvalidLength(len(bech))
+	}
+
+	return DecodeNoLimit(bech)
+}
+
+// Encode encodes a byte slice into a bech32 string with the
+// human-readable part hrb. Note that the bytes must each encode 5 bits
+// (base32).
+func Encode(hrp string, data []byte) (string, error) {
+
+	// The resulting bech32 string is the concatenation of the hrp, the
+	// separator 1, data and the 6-byte checksum.
+	var bldr strings.Builder
+	bldr.Grow(len(hrp) + 1 + len(data) + 6)
+	bldr.WriteString(hrp)
+	bldr.WriteString("1")
+
+	// Write the data part, using the bech32 charset.
+	for _, b := range data {
+		if int(b) >= len(charset) {
+			return "", ErrInvalidDataByte(b)
+		}
+		bldr.WriteByte(charset[b])
+	}
+
+	// Calculate and write the checksum of the data.
+	writeBech32Checksum(hrp, data, &bldr)
+
+	return bldr.String(), nil
+}
+
+// ConvertBits converts a byte slice where each byte is encoding fromBits bits,
+// to a byte slice where each byte is encoding toBits bits.
+func ConvertBits(data []byte, fromBits, toBits uint8, pad bool) ([]byte, error) {
+	if fromBits < 1 || fromBits > 8 || toBits < 1 || toBits > 8 {
+		return nil, ErrInvalidBitGroups{}
+	}
+
+	// Determine the maximum size the resulting array can have after base
+	// conversion, so that we can size it a single time. This might be off
+	// by a byte depending on whether padding is used or not and if the input
+	// data is a multiple of both fromBits and toBits, but we ignore that and
+	// just size it to the maximum possible.
+	maxSize := len(data)*int(fromBits)/int(toBits) + 1
+
+	// The final bytes, each byte encoding toBits bits.
+	regrouped := make([]byte, 0, maxSize)
+
+	// Keep track of the next byte we create and how many bits we have
+	// added to it out of the toBits goal.
+	nextByte := byte(0)
+	filledBits := uint8(0)
+
+	for _, b := range data {
+
+		// Discard unused bits.
+		b = b << (8 - fromBits)
+
+		// How many bits remaining to extract from the input data.
+		remFromBits := fromBits
+		for remFromBits > 0 {
+			// How many bits remaining to be added to the next byte.
+			remToBits := toBits - filledBits
+
+			// The number of bytes to next extract is the minimum of
+			// remFromBits and remToBits.
+			toExtract := remFromBits
+			if remToBits < toExtract {
+				toExtract = remToBits
+			}
+
+			// Add the next bits to nextByte, shifting the already
+			// added bits to the left.
+			nextByte = (nextByte << toExtract) | (b >> (8 - toExtract))
+
+			// Discard the bits we just extracted and get ready for
+			// next iteration.
+			b = b << toExtract
+			remFromBits -= toExtract
+			filledBits += toExtract
+
+			// If the nextByte is completely filled, we add it to
+			// our regrouped bytes and start on the next byte.
+			if filledBits == toBits {
+				regrouped = append(regrouped, nextByte)
+				filledBits = 0
+				nextByte = 0
+			}
+		}
+	}
+
+	// We pad any unfinished group if specified.
+	if pad && filledBits > 0 {
+		nextByte = nextByte << (toBits - filledBits)
+		regrouped = append(regrouped, nextByte)
+		filledBits = 0
+		nextByte = 0
+	}
+
+	// Any incomplete group must be <= 4 bits, and all zeroes.
+	if filledBits > 0 && (filledBits > 4 || nextByte != 0) {
+		return nil, ErrInvalidIncompleteGroup{}
+	}
+
+	return regrouped, nil
+}