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Merge pull request #2630 from canokeys/fix_ecdh_kek_error

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Fix ECDH decryption error using NIST curves
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Dominik Schürmann 2021-03-16 15:13:23 +01:00 • committed by GitHub
commit 7e5738bd5c
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GPG key ID: 4AEE18F83AFDEB23
1 changed files with 11 additions and 1 deletions
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12
OpenKeychain/src/main/java/org/sufficientlysecure/keychain/securitytoken/operations/PsoDecryptTokenOp.java
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@ -164,6 +164,16 @@ public class PsoDecryptTokenOp {
*/
byte[] keyEncryptionKey = response.getData();
int xLen;
boolean isCurve25519 = CryptlibObjectIdentifiers.curvey25519.equals(eckf.getCurveOID());
if (isCurve25519) {
xLen = keyEncryptionKey.length;
} else {
xLen = (keyEncryptionKey.length - 1) / 2;
}
final byte[] kekX = new byte[xLen];
System.arraycopy(keyEncryptionKey, isCurve25519 ? 0 : 1, kekX, 0, xLen);
final byte[] keyEnc = new byte[encryptedSessionKeyMpi[mpiLength + 2]];
System.arraycopy(encryptedSessionKeyMpi, 2 + mpiLength + 1, keyEnc, 0, keyEnc.length);
@ -172,7 +182,7 @@ public class PsoDecryptTokenOp {
final MessageDigest kdf = MessageDigest.getInstance(MessageDigestUtils.getDigestName(publicKey.getSecurityTokenHashAlgorithm()));
kdf.update(new byte[]{(byte) 0, (byte) 0, (byte) 0, (byte) 1});
kdf.update(keyEncryptionKey);
kdf.update(kekX);
kdf.update(publicKey.createUserKeyingMaterial(fingerprintCalculator));
byte[] kek = kdf.digest();