WIP: SecpPrivKeySegment impl for FFM #482
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| Original file line number | Diff line number | Diff line change |
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| @@ -0,0 +1,99 @@ | ||
| /* | ||
| * Copyright 2023-2026 secp256k1-jdk Developers. | ||
| * | ||
| * 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 org.bitcoinj.secp.ffm; | ||
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| import org.bitcoinj.secp.SecpPrivKey; | ||
| import org.bitcoinj.secp.internal.ByteArray; | ||
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| import java.io.IOException; | ||
| import java.io.NotSerializableException; | ||
| import java.io.ObjectInputStream; | ||
| import java.io.ObjectOutputStream; | ||
| import java.io.Serial; | ||
| import java.lang.foreign.Arena; | ||
| import java.lang.foreign.MemorySegment; | ||
| import java.math.BigInteger; | ||
| import java.util.Arrays; | ||
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| import static java.lang.foreign.ValueLayout.JAVA_BYTE; | ||
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| /// Native implementation of SecpPrivKey | ||
| class SecpPrivKeySegment implements SecpPrivKey { | ||
| private static final int KEY_LENGTH = 32; | ||
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| private volatile boolean destroyed = false; | ||
| private final MemorySegment segment; | ||
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| SecpPrivKeySegment(MemorySegment privKeySeg) { | ||
| var segment = Arena.ofAuto().allocate(KEY_LENGTH); | ||
| MemorySegment.copy(privKeySeg, 0, segment, 0, KEY_LENGTH); | ||
| this.segment = segment; | ||
| } | ||
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| SecpPrivKeySegment(byte[] privKeyBytes) { | ||
| this(MemorySegment.ofArray(privKeyBytes)); | ||
| } | ||
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| @Override | ||
| public byte[] getEncoded() { | ||
| if (destroyed) throwKeyDestroyed(); | ||
| return segment.toArray(JAVA_BYTE); | ||
| } | ||
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| @Override | ||
| public BigInteger getS() { | ||
| if (destroyed) throwKeyDestroyed(); | ||
| byte[] bytes = getEncoded(); | ||
| try { | ||
| return ByteArray.toInteger(bytes); | ||
| } finally { | ||
| Arrays.fill(bytes, (byte) 0); | ||
| } | ||
| } | ||
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| @Override | ||
| public void destroy() { | ||
| // TODO: Make sure the zeroing is not optimized out by the compiler or JIT | ||
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Member
There was a problem hiding this comment. Here is the C equivalent. I believe this may work: private static final VarHandle BYTE_VH = ValueLayout.JAVA_BYTE.varHandle();
public void destroy() {
if (destroyed) return;
for (long i = 0, n = segment.byteSize(); i < n; i++) {
BYTE_VH.setVolatile(segment, i, (byte) 0);
}
destroyed = true;
}This basically allows for volatile writes to off-heap memory, which shouldn't be optimized away.
Member
Author
There was a problem hiding this comment. That's in interesting idea. I think we should find out whether the JDK/FFM can optimize out a call to |
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| if (!destroyed) { | ||
| segment.fill((byte) 0); | ||
| destroyed = true; | ||
| } | ||
| } | ||
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| @Override | ||
| public boolean isDestroyed() { | ||
| return destroyed; | ||
| } | ||
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| MemorySegment segment() { | ||
| if (destroyed) throwKeyDestroyed(); | ||
| return segment.asReadOnly(); | ||
| } | ||
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| private void throwKeyDestroyed() { | ||
| throw new IllegalStateException("Private Key has been destroyed"); | ||
| } | ||
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| @Serial | ||
| private void writeObject(ObjectOutputStream out) throws IOException { | ||
| throw new NotSerializableException("Serialization of private keys is prohibited."); | ||
| } | ||
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| @Serial | ||
| private void readObject(ObjectInputStream in) throws IOException, ClassNotFoundException { | ||
| throw new NotSerializableException("Deserialization of private keys is prohibited."); | ||
| } | ||
| } | ||
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,77 @@ | ||
| /* | ||
| * Copyright 2023-2026 secp256k1-jdk Developers. | ||
| * | ||
| * 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 org.bitcoinj.secp.ffm; | ||
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| import org.bitcoinj.secp.SecpFieldElement; | ||
| import org.bitcoinj.secp.SecpPubKey; | ||
| import org.bitcoinj.secp.ffm.jextract.secp256k1_pubkey; | ||
| import org.bitcoinj.secp.internal.SecpECPoint; | ||
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| import java.lang.foreign.Arena; | ||
| import java.lang.foreign.MemorySegment; | ||
| import java.lang.foreign.SegmentAllocator; | ||
| import java.security.spec.ECPoint; | ||
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| import static org.bitcoinj.secp.ffm.jextract.secp256k1_h.SECP256K1_EC_UNCOMPRESSED; | ||
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| /// | ||
| public class SecpPubKeySegment implements SecpPubKey { | ||
| private static final long SIZE = secp256k1_pubkey.sizeof(); | ||
| private final MemorySegment segment; | ||
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| public SecpPubKeySegment(MemorySegment pubKeySegment) { | ||
| var segment = Arena.ofAuto().allocate(SIZE); | ||
| MemorySegment.copy(pubKeySegment, 0, segment, 0, SIZE); | ||
| this.segment = segment.asReadOnly(); | ||
| } | ||
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| MemorySegment segment() { | ||
| return segment; | ||
| } | ||
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| @Override | ||
| public ECPoint getW() { | ||
| Uncompressed point = point(); | ||
| return new SecpECPoint(point.x(), point.y()); | ||
| } | ||
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| @Override | ||
| public Uncompressed point() { | ||
| SegmentAllocator alloc = Arena.ofAuto(); | ||
| MemorySegment serializedPubKeySeg = Secp256k1Foreign.pubKeySerializeSegment(alloc, segment, SECP256K1_EC_UNCOMPRESSED()); | ||
| return Secp256k1Foreign.serializedPubKeyToPoint(serializedPubKeySeg); | ||
| } | ||
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| @Override | ||
| public SecpFieldElement x() { | ||
| return point().x(); | ||
| } | ||
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| @Override | ||
| public SecpFieldElement y() { | ||
| return point().y(); | ||
| } | ||
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| @Override | ||
| public Compressed compress() { | ||
| return point().compress(); | ||
| } | ||
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| @Override | ||
| public boolean isOdd() { | ||
| return point().isOdd(); | ||
| } | ||
| } |
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I think this comment can be a little more clear. Perhaps it should be stated that generally non-temporary segments are from the Secp*Segment objects and temporary segments are all others.
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Maybe the method should be named
zeroIfWritable? It's a low-level helper method and it doesn't really know what is temporary or not -- it just zerosMemorySegmentsthat are writable. We could then document how it used elsewhere.