+ * When encoding the line length and line separator are given in the constructor, and the encoding table is + * STANDARD_ENCODE_TABLE. + *
+ *+ * Line lengths that aren't multiples of 4 will still essentially end up being multiples of 4 in the encoded data. + *
+ *+ * When decoding all variants are supported. + *
+ * + * @param lineLength + * Each line of encoded data will be at most of the given length (rounded down to the nearest multiple of + * 4). If lineLength <= 0, then the output will not be divided into lines (chunks). Ignored when + * decoding. + * @param lineSeparator + * Each line of encoded data will end with this sequence of bytes. + * @param encodeTable + * The manual encodeTable - a byte array of 64 chars. + * @param decodingPolicy The decoding policy. + * @throws IllegalArgumentException + * Thrown when the {@code lineSeparator} contains Base64 characters. + * @since 1.17.0 + */ + public Base64(final int lineLength, final byte[] lineSeparator, final byte[] encodeTable, final CodecPolicy decodingPolicy) { super(BYTES_PER_UNENCODED_BLOCK, BYTES_PER_ENCODED_BLOCK, lineLength, lineSeparator == null ? 0 : lineSeparator.length, PAD_DEFAULT, decodingPolicy); + this.encodeTable = encodeTable; + + if (encodeTable == STANDARD_ENCODE_TABLE || encodeTable == URL_SAFE_ENCODE_TABLE) { + decodeTable = DECODE_TABLE; + } else { + if (encodeTable.length != ALPHABET_LENGTH) { + throw new IllegalArgumentException("encodeTable must be exactly 64 bytes long"); + } + decodeTable = calculateDecodeTable(encodeTable); + } // TODO could be simplified if there is no requirement to reject invalid line sep when length <=0 // @see test case Base64Test.testConstructors() if (lineSeparator != null) { @@ -607,7 +666,6 @@ public Base64(final int lineLength, final byte[] lineSeparator, final boolean ur this.lineSeparator = null; } this.decodeSize = this.encodeSize - 1; - this.encodeTable = urlSafe ? URL_SAFE_ENCODE_TABLE : STANDARD_ENCODE_TABLE; } // Implementation of the Encoder Interface @@ -653,8 +711,8 @@ void decode(final byte[] input, int inPos, final int inAvail, final Context cont context.eof = true; break; } - if (b >= 0 && b < DECODE_TABLE.length) { - final int result = DECODE_TABLE[b]; + if (b >= 0 && b < decodeTable.length) { + final int result = decodeTable[b]; if (result >= 0) { context.modulus = (context.modulus + 1) % BYTES_PER_ENCODED_BLOCK; context.ibitWorkArea = (context.ibitWorkArea << BITS_PER_ENCODED_BYTE) + result; @@ -802,6 +860,21 @@ protected boolean isInAlphabet(final byte octet) { return octet >= 0 && octet < decodeTable.length && decodeTable[octet] != -1; } + /** + * Calculates a decode table for a given encode table. + * + * @param encodeTable that is used to determine decode lookup table + * @return decodeTable + */ + private byte[] calculateDecodeTable(byte[] encodeTable) { + byte[] decodeTable = new byte[DECODING_TABLE_LENGTH]; + Arrays.fill(decodeTable, (byte) -1); + for (int i = 0; i < encodeTable.length; i++) { + decodeTable[encodeTable[i]] = (byte) i; + } + return decodeTable; + } + /** * Returns our current encode mode. True if we're URL-SAFE, false otherwise. * diff --git a/src/test/java/org/apache/commons/codec/binary/Base64Test.java b/src/test/java/org/apache/commons/codec/binary/Base64Test.java index 7919ea8859..6626a9188d 100644 --- a/src/test/java/org/apache/commons/codec/binary/Base64Test.java +++ b/src/test/java/org/apache/commons/codec/binary/Base64Test.java @@ -167,6 +167,56 @@ public void testBase64() { assertEquals("Hello World", decodeString, "decode hello world"); } + @Test + public void testCustomEncodingAlphabet_illegal() { + byte[] encodeTable = { + '.', '-', 'C', 'D', 'E', 'F', 'G', 'H', 'I', 'J', 'K', 'L', 'M' + }; + assertThrows(IllegalArgumentException.class, () -> new Base64(encodeTable)); + } + + @Test + public void testCustomEncodingAlphabet() { + // created a duplicate of STANDARD_ENCODE_TABLE and replaced two chars with + // custom values not already present in table + // A => . B => - + byte[] encodeTable = { + '.', '-', 'C', 'D', 'E', 'F', 'G', 'H', 'I', 'J', 'K', 'L', 'M', + 'N', 'O', 'P', 'Q', 'R', 'S', 'T', 'U', 'V', 'W', 'X', 'Y', 'Z', + 'a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i', 'j', 'k', 'l', 'm', + 'n', 'o', 'p', 'q', 'r', 's', 't', 'u', 'v', 'w', 'x', 'y', 'z', + '0', '1', '2', '3', '4', '5', '6', '7', '8', '9', '+', '/' + }; + + // two instances: one with default table and one with adjusted encoding table + Base64 b64 = new Base64(); + Base64 b64customEncoding = new Base64(encodeTable); + + final String content = "! Hello World - this ยง$%"; + + byte[] encodedBytes = b64.encode(StringUtils.getBytesUtf8(content)); + String encodedContent = StringUtils.newStringUtf8(encodedBytes); + + byte[] encodedBytesCustom = b64customEncoding.encode(StringUtils.getBytesUtf8(content)); + String encodedContentCustom = StringUtils.newStringUtf8(encodedBytesCustom); + + assertTrue( + encodedContent.contains("A") && encodedContent.contains("B"), "testing precondition not met - ecodedContent should contain parts of modified table"); + + assertEquals( + encodedContent + .replaceAll("A", ".").replaceAll("B", "-") // replace alphabet adjustments + .replaceAll("=", "") // remove padding (not default alphabet) + , encodedContentCustom); + + + // try decode encoded content + final byte[] decode = b64customEncoding.decode(encodedBytesCustom); + final String decodeString = StringUtils.newStringUtf8(decode); + + assertEquals(content, decodeString); + } + @Test public void testBase64AtBufferEnd() { testBase64InBuffer(100, 0);