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[CBOR] - Implement RFC compliant BigInteger bytes encoding & decoding #578

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Merged
merged 11 commits into from
Apr 30, 2025
Merged

[CBOR] - Implement RFC compliant BigInteger bytes encoding & decoding #578

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85a5c56
[CBOR] - Implement RFC compliant binary BigInteger encoding & decoding
iifawzi Apr 26, 2025
2d42c5a
unify documentation
iifawzi Apr 26, 2025
4cff9c4
update version comment
iifawzi Apr 27, 2025
76373fb
simplify conditions and limit it to negative big integers
iifawzi Apr 27, 2025
b07c95a
update referenced decoder to use the variant of leading zero
iifawzi Apr 27, 2025
6d0767a
testing we're able to decode with/without leading zeros
iifawzi Apr 27, 2025
c69c23c
reference cbor.me in tests for clarity
iifawzi Apr 27, 2025
71f8cdc
rename variable
iifawzi Apr 27, 2025
138c1cf
Merge branch '2.x' into fix-cbor-negative-bigInteger
cowtowncoder Apr 30, 2025
8220346
Add release notes, minor renaming, refactoring
cowtowncoder Apr 30, 2025
4727239
Make tests more 3.0-proof (wrt configuration)
cowtowncoder Apr 30, 2025
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23 changes: 22 additions & 1 deletion cbor/src/main/java/com/fasterxml/jackson/dataformat/cbor/CBORGenerator.java
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Original file line number Diff line number Diff line change
Expand Up @@ -115,6 +115,23 @@ public enum Feature implements FormatFeature {
* @since 2.15
*/
WRITE_MINIMAL_DOUBLES(false),

/**
* Feature that determines how binary tagged negative BigInteger values are
* encoded.
*
* When enabled, Ensures proper encoding of negative values
* (e.g., -1 is encoded [0xC3, 0x41, 0x00])
*
* When disabled, Maintains backwards compatibility with existing implementations
* (e.g., -1 is encoded [0xC3, 0x41, 0x01])
*
* The default value is false for backwards compatibility.
*
* @since 2.20.0
*/

CORRECT_CBOR_NEGATIVE_BIGINT_ENCODING(false)
;

protected final boolean _defaultState;
Expand Down Expand Up @@ -1217,7 +1234,11 @@ protected void _write(BigInteger v) throws IOException {
*/
if (v.signum() < 0) {
_writeByte(BYTE_TAG_BIGNUM_NEG);
v = v.negate();
if (isEnabled(CBORGenerator.Feature.CORRECT_CBOR_NEGATIVE_BIGINT_ENCODING)) {
v = BigInteger.ONE.negate().subtract(v);
} else {
v = v.negate();
}
} else {
_writeByte(BYTE_TAG_BIGNUM_POS);
}
Expand Down
50 changes: 41 additions & 9 deletions cbor/src/main/java/com/fasterxml/jackson/dataformat/cbor/CBORParser.java
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Expand Up @@ -29,6 +29,22 @@ public class CBORParser extends ParserMinimalBase
public enum Feature implements FormatFeature
{
// BOGUS(false)

/**
* Feature that determines how binary tagged negative BigInteger values are
* decoded.
*
* When enabled, Ensures proper encoding of negative values
* (e.g., [0xC3, 0x41, 0x00] is decoded -1)
*
* When disabled, Maintains backwards compatibility with existing implementations
* (e.g., [0xC3, 0x41, 0x00] is decoded 0)
*
* The default value is false for backwards compatibility.
*
* @since 2.20.0
*/
CORRECT_CBOR_NEGATIVE_BIGINT_DECODING(false)
;

final boolean _defaultState;
Expand Down Expand Up @@ -515,6 +531,7 @@ public CBORParser(IOContext ctxt, int parserFeatures, int cborFeatures,
boolean bufferRecyclable)
{
super(parserFeatures, ctxt.streamReadConstraints());
_formatFeatures = cborFeatures;
_ioContext = ctxt;
_objectCodec = codec;
_symbols = sym;
Expand Down Expand Up @@ -561,12 +578,22 @@ public Version version() {
/**********************************************************
*/

// public JsonParser overrideStdFeatures(int values, int mask)
/**
* Bit flag composed of bits that indicate which
* {@link CBORParser.Feature}s are enabled.
*<p>
*/
protected int _formatFeatures;

@Override
public final JsonParser overrideFormatFeatures(int values, int mask) {
_formatFeatures = (_formatFeatures & ~mask) | (values & mask);
return this;
}

@Override
public int getFormatFeatures() {
// No parser features, yet
return 0;
public final int getFormatFeatures() {
return _formatFeatures;
}

@Override // since 2.12
Expand Down Expand Up @@ -1123,11 +1150,16 @@ protected JsonToken _handleTaggedBinary(TagList tags) throws IOException
_numberBigInt = BigInteger.ZERO;
} else {
_streamReadConstraints.validateIntegerLength(_binaryValue.length);
BigInteger nr = new BigInteger(_binaryValue);
if (neg) {
nr = nr.negate();
}
_numberBigInt = nr;

BigInteger nr = new BigInteger(_binaryValue);
if (neg) {
if (Feature.CORRECT_CBOR_NEGATIVE_BIGINT_DECODING.enabledIn(_formatFeatures)) {
nr = BigInteger.ONE.negate().subtract(new BigInteger(1, _binaryValue));
} else {
nr = nr.negate();
}
}
_numberBigInt = nr;
}
_numTypesValid = NR_BIGINT;
_tagValues.clear();
Expand Down
34 changes: 34 additions & 0 deletions cbor/src/main/java/com/fasterxml/jackson/dataformat/cbor/databind/CBORMapper.java
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Original file line number Diff line number Diff line change
Expand Up @@ -36,6 +36,40 @@ public Builder(CBORMapper m) {
/******************************************************************
*/

/**
* @since 2.20.0
*/
public Builder enable(CBORParser.Feature... features) {
for (CBORParser.Feature f : features) {
_streamFactory.enable(f);
}
return this;
}

/**
* @since 2.20.0
*/
public Builder disable(CBORParser.Feature... features) {
for (CBORParser.Feature f : features) {
_streamFactory.disable(f);
}
return this;
}

/**
* @since 2.20.0
*/
public Builder configure(CBORParser.Feature f, boolean state)
{
if (state) {
_streamFactory.enable(f);
} else {
_streamFactory.disable(f);
}
return this;
}


/**
* @since 2.14
*/
Expand Down
131 changes: 131 additions & 0 deletions cbor/src/test/java/com/fasterxml/jackson/dataformat/cbor/gen/GeneratorSimpleTest.java
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Expand Up @@ -259,6 +259,137 @@ public void testBigDecimalValues() throws Exception
assertArrayEquals(spec, b);
}

// [dataformats-binary#431]
// [https://datatracker.ietf.org/doc/html/rfc8949#section-3.4.3]
@Test
public void testSimpleBigIntegerEncoding() throws Exception {
BigInteger minusOne = BigInteger.valueOf(-1);
byte[] expectedBytes = {
(byte) 0xC3, // tag 3 (negative bignum)
(byte) 0x41 // byte string, length 1
};

// Test correct encoding
ByteArrayOutputStream correctOut = new ByteArrayOutputStream();
CBORFactory factory = new CBORFactory();
CBORGenerator gen1 = factory.createGenerator(correctOut);
gen1.enable(CBORGenerator.Feature.CORRECT_CBOR_NEGATIVE_BIGINT_ENCODING);
gen1.writeNumber(minusOne);
gen1.close();

byte[] result1 = correctOut.toByteArray();
assertEquals(3, result1.length);
assertEquals(expectedBytes[0], result1[0]);
assertEquals(expectedBytes[1], result1[1]);
assertEquals(0x00, result1[2]);

// Test incorrect encoding for compatibility
ByteArrayOutputStream incorrectOut = new ByteArrayOutputStream();
CBORGenerator gen2 = cborGenerator(incorrectOut);
gen2.writeNumber(minusOne);
gen2.close();

byte[] result2 = incorrectOut.toByteArray();
assertEquals(3, result2.length);
assertEquals(expectedBytes[0], result2[0]);
assertEquals(expectedBytes[1], result2[1]);
assertEquals(0x01, result2[2]);
}

@Test
public void testZeroBigIntegerEncoding() throws Exception {
BigInteger zero = BigInteger.valueOf(0);
byte[] expectedBytes = {
(byte) 0xC2, // tag 2 (positive bignum)
(byte) 0x41, // byte string, 1 byte
(byte) 0x00, // 0
};

ByteArrayOutputStream correctOut = new ByteArrayOutputStream();
CBORFactory factory = new CBORFactory();
CBORGenerator gen1 = factory.createGenerator(correctOut);
gen1.enable(CBORGenerator.Feature.CORRECT_CBOR_NEGATIVE_BIGINT_ENCODING);
gen1.writeNumber(zero);
gen1.close();

byte[] result = correctOut.toByteArray();
assertEquals(3, result.length);
assertArrayEquals(expectedBytes, result);
}

// [dataformats-binary#431]
// [https://datatracker.ietf.org/doc/html/rfc8949#section-3.4.3]
@Test
public void testNgeativeBigIntegerEncoding() throws Exception {
BigInteger negativeBigInteger = new BigInteger("-340282366920938463463374607431768211456");
// correct encoding: https://cbor.me/?bytes=c35100ffffffffffffffffffffffffffffffff
byte[] expectedBytes = {
(byte) 0xC3,
(byte) 0x51,
(byte) 0x00,
(byte) 0xFF,
(byte) 0xFF,
(byte) 0xFF,
(byte) 0xFF,
(byte) 0xFF,
(byte) 0xFF,
(byte) 0xFF,
(byte) 0xFF,
(byte) 0xFF,
(byte) 0xFF,
(byte) 0xFF,
(byte) 0xFF,
(byte) 0xFF,
(byte) 0xFF,
(byte) 0xFF,
(byte) 0xFF
};

// Test correct encoding
ByteArrayOutputStream correctOut = new ByteArrayOutputStream();
CBORFactory factory = new CBORFactory();
CBORGenerator gen1 = factory.createGenerator(correctOut);
gen1.enable(CBORGenerator.Feature.CORRECT_CBOR_NEGATIVE_BIGINT_ENCODING);
gen1.writeNumber(negativeBigInteger);
gen1.close();

byte[] result1 = correctOut.toByteArray();
assertArrayEquals(expectedBytes, result1);


// Test incorrect encoding for compatibility
// incorrect encoding: https://cbor.me/?bytes=c3510100000000000000000000000000000000
byte[] legacyExpectedBytes = {
(byte) 0xC3,
(byte) 0x51,
(byte) 0x01,
(byte) 0x00,
(byte) 0x00,
(byte) 0x00,
(byte) 0x00,
(byte) 0x00,
(byte) 0x00,
(byte) 0x00,
(byte) 0x00,
(byte) 0x00,
(byte) 0x00,
(byte) 0x00,
(byte) 0x00,
(byte) 0x00,
(byte) 0x00,
(byte) 0x00,
(byte) 0x00,
};
ByteArrayOutputStream incorrectOut = new ByteArrayOutputStream();
CBORGenerator gen2 = cborGenerator(incorrectOut);
gen2.writeNumber(negativeBigInteger);
gen2.close();

byte[] result2 = incorrectOut.toByteArray();
assertEquals(19, result2.length);
assertArrayEquals(legacyExpectedBytes, result2);
}

@Test
public void testEmptyArray() throws Exception
{
Expand Down
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