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Improvements in ECKey.extractKeyFromASN1

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- Check there's no extra data following the key
- Confirm the ASN.1 tag number is correct on the publicKey field
- Explicitly check the encoding is one we support
- Rework the sanity check to avoid redundant parsing/multiplies
This commit is contained in:
Peter Dettman 2015-06-12 19:59:38 +07:00 committed by Mike Hearn
parent 2b8fa07ae8
commit a2e0908436
1 changed files with 20 additions and 11 deletions
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31
core/src/main/java/org/bitcoinj/core/ECKey.java
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@ -784,22 +784,31 @@ public class ECKey implements EncryptableItem, Serializable {
try {
ASN1InputStream decoder = new ASN1InputStream(asn1privkey);
DLSequence seq = (DLSequence) decoder.readObject();
checkArgument(decoder.readObject() == null, "Input contains extra bytes");
decoder.close();
checkArgument(seq.size() == 4, "Input does not appear to be an ASN.1 OpenSSL EC private key");
checkArgument(((ASN1Integer) seq.getObjectAt(0)).getValue().equals(BigInteger.ONE),
"Input is of wrong version");
Object obj = seq.getObjectAt(1);
byte[] privbits = ((ASN1OctetString) obj).getOctets();
decoder.close();
byte[] privbits = ((ASN1OctetString) seq.getObjectAt(1)).getOctets();
BigInteger privkey = new BigInteger(1, privbits);
byte[] pubbits = ((DERBitString)((ASN1TaggedObject)seq.getObjectAt(3)).getObject()).getBytes();
ASN1TaggedObject pubkey = (ASN1TaggedObject) seq.getObjectAt(3);
checkArgument(pubkey.getTagNo() == 1, "Input has 'publicKey' with bad tag number");
byte[] pubbits = ((DERBitString)pubkey.getObject()).getBytes();
checkArgument(pubbits.length == 33 || pubbits.length == 65, "Input has 'publicKey' with invalid length");
int encoding = pubbits[0] & 0xFF;
// Only allow compressed(2,3) and uncompressed(4), not infinity(0) or hybrid(6,7)
checkArgument(encoding >= 2 && encoding <= 4, "Input has 'publicKey' with invalid encoding");
// Now sanity check to ensure the pubkey bytes match the privkey.
byte[] compressed = publicKeyFromPrivate(privkey, true);
if (Arrays.equals(pubbits, compressed))
return new ECKey(privkey, compressed);
byte[] uncompressed = publicKeyFromPrivate(privkey, false);
if (Arrays.equals(pubbits, uncompressed))
return new ECKey(privkey, uncompressed);
throw new IllegalArgumentException("Public key in ASN.1 structure does not match private key.");
boolean compressed = (pubbits.length == 33);
ECKey key = new ECKey(privkey, null, compressed);
if (!Arrays.equals(key.getPubKey(), pubbits))
throw new IllegalArgumentException("Public key in ASN.1 structure does not match private key.");
return key;
} catch (IOException e) {
throw new RuntimeException(e); // Cannot happen, reading from memory stream.
}