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fix the compatibility of compressed and uncompressed format in ECDH

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dangfan 2021-04-21 09:25:59 +08:00
parent 38157242e1
commit 9ea9bd96bb
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1 changed files with 14 additions and 5 deletions
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19
OpenKeychain/src/main/java/org/sufficientlysecure/keychain/securitytoken/operations/PsoDecryptTokenOp.java
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@ -161,14 +161,23 @@ public class PsoDecryptTokenOp {
*/
byte[] keyEncryptionKey = response.getData();
int xLen;
if (eckf.isX25519()) {
xLen = keyEncryptionKey.length;
} else {
/* From rfc6637#section-7 :
The input of KDF should be the x portion of the point.
As the result of ECDH can be expressed in two formats: compressed and uncompressed,
we have to deal with each case.
*/
int xLen, startPos;
if (keyEncryptionKey[0] == 0x04 && keyEncryptionKey.length % 2 == 1) {
// uncompressed format
xLen = (keyEncryptionKey.length - 1) / 2;
startPos = 1;
} else {
// compressed format
xLen = keyEncryptionKey.length;
startPos = 0;
}
final byte[] kekX = new byte[xLen];
System.arraycopy(keyEncryptionKey, eckf.isX25519() ? 0 : 1, kekX, 0, xLen);
System.arraycopy(keyEncryptionKey, startPos, kekX, 0, xLen);
final byte[] keyEnc = new byte[encryptedSessionKeyMpi[mpiLength + 2]];