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Add canonical signature/pubkey methods to ECKey and tests therefor.

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This commit is contained in:
Matt Corallo 2013-06-16 17:26:00 +02:00 committed by Mike Hearn
parent ec3708d159
commit d6fec93be3
4 changed files with 156 additions and 0 deletions
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59
core/src/main/java/com/google/bitcoin/core/ECKey.java
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@ -473,6 +473,65 @@ public class ECKey implements Serializable {
return ECKey.verify(sigHash.getBytes(), signature, getPubKey());
}
/**
* Returns true if the given signature is in canonical form (ie will be accepted as standard by the reference client)
*/
public static boolean isSignatureCanonical(byte[] signature) {
// See reference client's IsCanonicalSignature, https://bitcointalk.org/index.php?topic=8392.msg127623#msg127623
// A canonical signature exists of: <30> <total len> <02> <len R> <R> <02> <len S> <S> <hashtype>
// Where R and S are not negative (their first byte has its highest bit not set), and not
// excessively padded (do not start with a 0 byte, unless an otherwise negative number follows,
// in which case a single 0 byte is necessary and even required).
if (signature.length < 9 || signature.length > 73)
return false;
int hashType = signature[signature.length-1] & ((int)(~Transaction.SIGHASH_ANYONECANPAY_VALUE));
if (hashType < (Transaction.SigHash.ALL.ordinal() + 1) || hashType > (Transaction.SigHash.SINGLE.ordinal() + 1))
return false;
// "wrong type" "wrong length marker"
if ((signature[0] & 0xff) != 0x30 || (signature[1] & 0xff) != signature.length-3)
return false;
int lenR = signature[3] & 0xff;
if (5 + lenR >= signature.length || lenR == 0)
return false;
int lenS = signature[5+lenR] & 0xff;
if (lenR + lenS + 7 != signature.length || lenS == 0)
return false;
// R value type mismatch R value negative
if (signature[4-2] != 0x02 || (signature[4] & 0x80) == 0x80)
return false;
if (lenR > 1 && signature[4] == 0x00 && (signature[4+1] & 0x80) != 0x80)
return false; // R value excessively padded
// S value type mismatch S value negative
if (signature[6 + lenR - 2] != 0x02 || (signature[6 + lenR] & 0x80) == 0x80)
return false;
if (lenS > 1 && signature[6 + lenR] == 0x00 && (signature[6 + lenR + 1] & 0x80) != 0x80)
return false; // S value excessively padded
return true;
}
/**
* Returns true if the given pubkey is canonical (ie the correct length for its declared type)
*/
public static boolean isPubKeyCanonical(byte[] pubkey) {
if (pubkey.length < 33)
return false;
if (pubkey[0] == 0x04) { // Uncompressed pubkey
if (pubkey.length != 65)
return false;
} else if (pubkey[0] == 0x02 || pubkey[0] == 0x03) { // Compressed pubkey
if (pubkey.length != 33)
return false;
} else
return false;
return true;
}
private static BigInteger extractPrivateKeyFromASN1(byte[] asn1privkey) {
// To understand this code, see the definition of the ASN.1 format for EC private keys in the OpenSSL source
// code in ec_asn1.c:

68
core/src/test/java/com/google/bitcoin/core/ECKeyTest.java
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@ -37,6 +37,8 @@ import java.math.BigInteger;
import java.security.SecureRandom;
import java.security.SignatureException;
import java.util.Arrays;
import java.util.Random;
import java.io.InputStream;
import static com.google.bitcoin.core.Utils.reverseBytes;
import static org.junit.Assert.*;
@ -353,6 +355,7 @@ public class ECKeyTest {
assertTrue(found);
}
@Test
public void roundTripDumpedPrivKey() throws Exception {
ECKey key = new ECKey();
assertTrue(key.isCompressed());
@ -385,6 +388,71 @@ public class ECKeyTest {
checkAllBytesAreZero(encryptedKey.getEncryptedPrivateKey().getInitialisationVector());
}
@Test
public void testCanonicalSigs() throws Exception {
// Tests the canonical sigs from the reference client unit tests
InputStream in = getClass().getResourceAsStream("sig_canonical.json");
// Poor man's JSON parser (because pulling in a lib for this is overkill)
while (in.available() > 0) {
while (in.available() > 0 && in.read() != '"') ;
if (in.available() < 1)
break;
StringBuilder sig = new StringBuilder();
int c;
while (in.available() > 0 && (c = in.read()) != '"')
sig.append((char)c);
assertTrue(ECKey.isSignatureCanonical(Hex.decode(sig.toString())));
}
in.close();
}
@Test
public void testNonCanonicalSigs() throws Exception {
// Tests the noncanonical sigs from the reference client unit tests
InputStream in = getClass().getResourceAsStream("sig_noncanonical.json");
// Poor man's JSON parser (because pulling in a lib for this is overkill)
while (in.available() > 0) {
while (in.available() > 0 && in.read() != '"') ;
if (in.available() < 1)
break;
StringBuilder sig = new StringBuilder();
int c;
while (in.available() > 0 && (c = in.read()) != '"')
sig.append((char)c);
try {
assertFalse(ECKey.isSignatureCanonical(Hex.decode(sig.toString())));
} catch (StringIndexOutOfBoundsException e) { } // Expected for non-hex strings in the JSON that we should ignore
}
in.close();
}
@Test
public void testCreatedSigAndPubkeyAreCanonical() throws Exception {
// Tests that we will not generate non-canonical pubkeys or signatures
// We dump failed data to error log because this test is not expected to be deterministic
ECKey key = new ECKey();
if (!ECKey.isPubKeyCanonical(key.getPubKey())) {
log.error(Utils.bytesToHexString(key.getPubKey()));
fail();
}
byte[] hash = new byte[32];
new Random().nextBytes(hash);
byte[] sigBytes = key.sign(new Sha256Hash(hash)).encodeToDER();
byte[] encodedSig = Arrays.copyOf(sigBytes, sigBytes.length + 1);
encodedSig[sigBytes.length] = (byte) (Transaction.SigHash.ALL.ordinal() + 1);
if (!ECKey.isSignatureCanonical(encodedSig)) {
log.error(Utils.bytesToHexString(sigBytes));
fail();
}
}
private boolean checkSomeBytesAreNonZero(byte[] bytes) {
if (bytes == null) {
return false;

7
core/src/test/resources/com/google/bitcoin/core/sig_canonical.json Normal file
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@ -0,0 +1,7 @@
[
"300602010002010001",
"3008020200ff020200ff01",
"304402203932c892e2e550f3af8ee4ce9c215a87f9bb831dcac87b2838e2c2eaa891df0c022030b61dd36543125d56b9f9f3a1f9353189e5af33cdda8d77a5209aec03978fa001",
"30450220076045be6f9eca28ff1ec606b833d0b87e70b2a630f5e3a496b110967a40f90a0221008fffd599910eefe00bc803c688c2eca1d2ba7f6b180620eaa03488e6585db6ba01",
"3046022100876045be6f9eca28ff1ec606b833d0b87e70b2a630f5e3a496b110967a40f90a0221008fffd599910eefe00bc803c688c2eca1d2ba7f6b180620eaa03488e6585db6ba01"
]

22
core/src/test/resources/com/google/bitcoin/core/sig_noncanonical.json Normal file
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@ -0,0 +1,22 @@
[
"non-hex strings are ignored",
"too short:", "30050201FF020001",
"too long:", "30470221005990e0584b2b238e1dfaad8d6ed69ecc1a4a13ac85fc0b31d0df395eb1ba6105022200002d5876262c288beb511d061691bf26777344b702b00f8fe28621fe4e566695ed01",
"hashtype:", "304402205990e0584b2b238e1dfaad8d6ed69ecc1a4a13ac85fc0b31d0df395eb1ba610502202d5876262c288beb511d061691bf26777344b702b00f8fe28621fe4e566695ed11",
"type:", "314402205990e0584b2b238e1dfaad8d6ed69ecc1a4a13ac85fc0b31d0df395eb1ba610502202d5876262c288beb511d061691bf26777344b702b00f8fe28621fe4e566695ed01",
"total length:", "304502205990e0584b2b238e1dfaad8d6ed69ecc1a4a13ac85fc0b31d0df395eb1ba610502202d5876262c288beb511d061691bf26777344b702b00f8fe28621fe4e566695ed01",
"S len oob:", "301F01205990e0584b2b238e1dfaad8d6ed69ecc1a4a13ac85fc0b31d0df395eb101",
"R+S:", "304502205990e0584b2b238e1dfaad8d6ed69ecc1a4a13ac85fc0b31d0df395eb1ba610502202d5876262c288beb511d061691bf26777344b702b00f8fe28621fe4e566695ed0001",
"R type:", "304401205990e0584b2b238e1dfaad8d6ed69ecc1a4a13ac85fc0b31d0df395eb1ba610502202d5876262c288beb511d061691bf26777344b702b00f8fe28621fe4e566695ed01",
"R len = 0:", "3024020002202d5876262c288beb511d061691bf26777344b702b00f8fe28621fe4e566695ed01",
"R<0:", "304402208990e0584b2b238e1dfaad8d6ed69ecc1a4a13ac85fc0b31d0df395eb1ba610502202d5876262c288beb511d061691bf26777344b702b00f8fe28621fe4e566695ed01",
"R padded:", "30450221005990e0584b2b238e1dfaad8d6ed69ecc1a4a13ac85fc0b31d0df395eb1ba610502202d5876262c288beb511d061691bf26777344b702b00f8fe28621fe4e566695ed01",
"S type:", "304402205990e0584b2b238e1dfaad8d6ed69ecc1a4a13ac85fc0b31d0df395eb1ba610501202d5876262c288beb511d061691bf26777344b702b00f8fe28621fe4e566695ed01",
"S len = 0:", "302402205990e0584b2b238e1dfaad8d6ed69ecc1a4a13ac85fc0b31d0df395eb1ba6105020001",
"S<0:", "304402205990e0584b2b238e1dfaad8d6ed69ecc1a4a13ac85fc0b31d0df395eb1ba61050220fd5876262c288beb511d061691bf26777344b702b00f8fe28621fe4e566695ed01",
"S padded:", "304502205990e0584b2b238e1dfaad8d6ed69ecc1a4a13ac85fc0b31d0df395eb1ba61050221002d5876262c288beb511d061691bf26777344b702b00f8fe28621fe4e566695ed01"
]