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Code Issues Releases Wiki Activity

DKIM check public key length

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M66B 2023-03-30 12:04:43 +02:00
parent 796ea88727
commit e8876f418f
1 changed files with 13 additions and 0 deletions
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13
app/src/main/java/eu/faircode/email/MessageHelper.java
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@ -98,6 +98,7 @@ import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;
import java.security.PublicKey;
import java.security.Signature;
import java.security.interfaces.RSAPublicKey;
import java.security.spec.X509EncodedKeySpec;
import java.text.Normalizer;
import java.text.ParsePosition;
@ -191,6 +192,7 @@ public class MessageHelper {
private static final int FORMAT_FLOWED_LINE_LENGTH = 72; // characters
private static final int MAX_DIAGNOSTIC = 250; // characters
private static final int DKIM_MIN_TEXT = 100; // characters
private static final int DKIM_MIN_KEY_LENGTH = 1024; // bits
private static final String DKIM_SIGNATURE = "DKIM-Signature";
private static final String ARC_SEAL = "ARC-Seal";
@ -2439,6 +2441,17 @@ public class MessageHelper {
PublicKey pubKey = keyFactory.generatePublic(pubKeySpec);
Signature sig = Signature.getInstance(salgo); // a=
// https://stackoverflow.com/a/43984402/1794097
if (pubKey instanceof RSAPublicKey)
try {
int keylen = ((RSAPublicKey) pubKey).getModulus().bitLength();
Log.i("DKIM RSA pubkey length=" + keylen);
if (keylen < DKIM_MIN_KEY_LENGTH)
throw new IllegalArgumentException("RSA pubkey length " + keylen + " < " + DKIM_MIN_KEY_LENGTH);
} catch (Throwable ex) {
Log.e(ex);
}
String hash = kv.get("b");
if (hash == null)
return null;