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Java library for Javascript Object Signing and Encryption (JOSE) and
JSON Web Tokens (JWT)
/*
* nimbus-jose-jwt
*
* Copyright 2012-2016, Connect2id Ltd.
*
* Licensed under the Apache License, Version 2.0 (the "License"); you may not use
* this file except in compliance with the License. You may obtain a copy of the
* License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software distributed
* under the License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR
* CONDITIONS OF ANY KIND, either express or implied. See the License for the
* specific language governing permissions and limitations under the License.
*/
package com.nimbusds.jose.util;
import java.util.Arrays;
final class Base64Codec {
/**
* The base 64 characters.
*/
private static final char[] CA = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/".toCharArray();
/**
* The base 64 URL-safe characters.
*/
private static final char[] CA_URL_SAFE = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789-_".toCharArray();
/**
* Maps base 64 characters to their respective byte values.
*/
private static final int[] IA = new int[256];
/**
* Maps base 64 URL-safe characters to their respective byte values.
*/
private static final int[] IA_URL_SAFE = new int[256];
static {
// Regular map
Arrays.fill(IA, -1);
for (int i = 0, iS = CA.length; i < iS; i++) {
IA[CA[i]] = i;
}
IA['='] = 0;
// URL-safe map
Arrays.fill(IA_URL_SAFE, -1);
for (int i = 0, iS = CA_URL_SAFE.length; i < iS; i++) {
IA_URL_SAFE[CA_URL_SAFE[i]] = i;
}
IA_URL_SAFE['='] = 0;
}
/**
* Computes the base 64 encoded character length for the specified
* input byte length.
*
* @param inputLength The input byte length.
* @param urlSafe {@code true} for URL-safe encoding.
*
* @return The base 64 encoded character length.
*/
public static int computeEncodedLength(final int inputLength, final boolean urlSafe) {
if (inputLength == 0) {
return 0;
}
if (urlSafe) {
// Compute the number of complete quads (4-char blocks)
int fullQuadLength = (inputLength / 3) << 2;
// Compute the remaining bytes at the end
int remainder = inputLength % 3;
// Compute the total
return remainder == 0 ? fullQuadLength : fullQuadLength + remainder + 1;
} else {
// Original Mig code
return ((inputLength - 1) / 3 + 1) << 2;
}
}
/**
* Normalises a base 64 encoded string by ensuring any URL-safe
* characters are replaced with their regular base64 representation and
* any truncated '=' padding is restored.
*
* @param b64String The base 64 or base 64 URL-safe encoded string.
* Must not be {@code null}.
*
* @return The normalised base 64 encoded string.
*/
public static String normalizeEncodedString(final String b64String) {
final int inputLen = b64String.length();
// Compute missing padding, taking illegal chars into account
final int legalLen = inputLen - countIllegalChars(b64String);
final int padLength = legalLen % 4 == 0 ? 0 : 4 - (legalLen % 4);
// Create output array
char[] chars = new char[inputLen + padLength];
// Copy chars into output array
b64String.getChars(0, inputLen, chars, 0);
// Append padding chars if required
for (int i = 0; i < padLength; i++) {
chars[inputLen + i] = '=';
}
// Replace URL-safe chars
for (int i = 0; i < inputLen; i++) {
if (chars[i] == '_') {
chars[i] = '/';
} else if (chars[i] == '-') {
chars[i] = '+';
}
}
return new String(chars);
}
/**
* Counts the illegal / separator characters in the specified base 64
* or base 64 URL-safe encoded string.
*
* @param b64String The base 64 or base 64 URL-safe encoded string.
* Must not be {@code null}.
*
* @return The illegal character count, zero if none.
*/
public static int countIllegalChars(final String b64String) {
// Number of separator and illegal characters
int illegalCharCount = 0;
for (int i = 0; i < b64String.length(); i++) {
final char c = b64String.charAt(i);
if (IA[c] == -1 && IA_URL_SAFE[c] == -1) {
illegalCharCount++;
}
}
return illegalCharCount;
}
/**
* Encodes a byte array into a base 64 encoded character array.
*
* @param byteArray The bytes to convert. If {@code null} or length 0
* an empty array will be returned.
* @param urlSafe If {@code true} to apply URL-safe encoding (padding
* still included and not to spec).
*
* @return The base 64 encoded character array. Never {@code null}.
*/
public static char[] encodeToChar(final byte[] byteArray, final boolean urlSafe) {
// Check special case
int sLen = byteArray != null ? byteArray.length : 0;
if (sLen == 0) {
return new char[0];
}
int eLen = (sLen / 3) * 3; // Length of even 24-bits.
int dLen = computeEncodedLength(sLen, urlSafe); // Returned character count
char[] out = new char[dLen];
// Encode even 24-bits
for (int s = 0, d = 0; s < eLen; ) {
// Copy next three bytes into lower 24 bits of int, paying attention to sign
int i = (byteArray[s++] & 0xff) << 16 | (byteArray[s++] & 0xff) << 8 | (byteArray[s++] & 0xff);
// Encode the int into four chars
if (urlSafe) {
out[d++] = CA_URL_SAFE[(i >>> 18) & 0x3f];
out[d++] = CA_URL_SAFE[(i >>> 12) & 0x3f];
out[d++] = CA_URL_SAFE[(i >>> 6) & 0x3f];
out[d++] = CA_URL_SAFE[i & 0x3f];
} else {
out[d++] = CA[(i >>> 18) & 0x3f];
out[d++] = CA[(i >>> 12) & 0x3f];
out[d++] = CA[(i >>> 6) & 0x3f];
out[d++] = CA[i & 0x3f];
}
}
// Pad and encode last bits if source isn't even 24 bits
// according to URL-safe switch
int left = sLen - eLen; // 0 - 2.
if (left > 0) {
// Prepare the int
int i = ((byteArray[eLen] & 0xff) << 10) | (left == 2 ? ((byteArray[sLen - 1] & 0xff) << 2) : 0);
// Set last four chars
if (urlSafe) {
if (left == 2) {
out[dLen - 3] = CA_URL_SAFE[i >> 12];
out[dLen - 2] = CA_URL_SAFE[(i >>> 6) & 0x3f];
out[dLen - 1] = CA_URL_SAFE[i & 0x3f];
} else {
out[dLen - 2] = CA_URL_SAFE[i >> 12];
out[dLen - 1] = CA_URL_SAFE[(i >>> 6) & 0x3f];
}
} else {
// Original Mig code with padding
out[dLen - 4] = CA[i >> 12];
out[dLen - 3] = CA[(i >>> 6) & 0x3f];
out[dLen - 2] = left == 2 ? CA[i & 0x3f] : '=';
out[dLen - 1] = '=';
}
}
return out;
}
/**
* Encodes a byte array into a base 64 encoded string.
*
* @param byteArray The bytes to convert. If {@code null} or length 0
* an empty array will be returned.
* @param urlSafe If {@code true} to apply URL-safe encoding (padding
* still included and not to spec).
*
* @return The base 64 encoded string. Never {@code null}.
*/
public static String encodeToString(byte[] byteArray, final boolean urlSafe) {
// Reuse char[] since we can't create a String incrementally
// and StringBuffer/Builder would be slower
return new String(encodeToChar(byteArray, urlSafe));
}
/**
* Decodes a base 64 or base 64 URL-safe encoded string. May contain
* line separators. Any illegal characters are ignored.
*
* @param b64String The base 64 or base 64 URL-safe encoded string. May
* be empty or {@code null}.
*
* @return The decoded byte array, empty if the input base 64 encoded
* string is empty, {@code null} or corrupted.
*/
public static byte[] decode(final String b64String) {
// Check special case
if (b64String == null || b64String.isEmpty()) {
return new byte[0];
}
final String nStr = normalizeEncodedString(b64String);
final int sLen = nStr.length();
// Count illegal characters (including '\r', '\n') to determine
// the size of the byte array to return
final int sepCnt = countIllegalChars(nStr);
// Ensure the legal chars (including '=' padding) divide by 4 (RFC 2045)
if ((sLen - sepCnt) % 4 != 0) {
// The string is corrupted
return new byte[0];
}
// Count '=' at end
int pad = 0;
for (int i = sLen; i > 1 && IA[nStr.charAt(--i)] <= 0; ) {
if (nStr.charAt(i) == '=') {
pad++;
}
}
int len = ((sLen - sepCnt) * 6 >> 3) - pad;
// Preallocate byte[] of final length
byte[] dArr = new byte[len];
for (int s = 0, d = 0; d < len; ) {
// Assemble three bytes into an int from four base 64
// characters
int i = 0;
for (int j = 0; j < 4; j++) {
// j only increased if a valid char was found
int c = IA[nStr.charAt(s++)];
if (c >= 0) {
i |= c << (18 - j * 6);
} else {
j--;
}
}
// Add the bytes
dArr[d++] = (byte) (i >> 16);
if (d < len) {
dArr[d++] = (byte) (i >> 8);
if (d < len) {
dArr[d++] = (byte) i;
}
}
}
return dArr;
}
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