JAMES jDKIM library

Library dealing with parsing and crytography to sign and verify DKIM signatures.

The mailet has been moved to James project: https://github.com/apache/james-project/tree/master/server/mailet/dkim

Usage

A full example is available in DKIMTest

Signing

Signing a mime message can be achieved using the following snippet

import java.io.InputStream;
import java.security.PrivateKey;

String signatureTemplate = "v=1; a=rsa-sha256; c=simple; d=messiah.edu; h=date:from:subject; q=dns/txt; s=selector2;";

PrivateKey privateKey = null;
DKIMSigner dkimSigner = new DKIMSigner(signatureTemplate, privateKey);
// You need to provide the input stream of the mime message, it will be parsed
// by mime4j
InputStream stream = null;
String signature = dkimSigner.sign(inputStream);
// `signature` contains the full header
// DKIM-Signature: a=rsa-sha256; q=dns/txt; b=Axa8s/g...U1SIw==; c=simple; s=selector2; d=messiah.edu; v=1; bh=6pQ...6g=; h=date:from:subject;

More advanced usage such as including multiple signatures can be found in DKIMTest

Verifying

Verifying a mime message DKIM signatures can be achieved using the following snippet. The verifier always verifies all the signatures.

import java.io.InputStream;
// You can override the resolver in the constructor, use your own
// implementation of a retriever or use multiple implementations using a
// `MultiplexingPublicKeyRecordRetriever`
PublicKeyRecordRetriever keyRecordRetriever = new DNSPublicKeyRecordRetriever();
DKIMVerifier verifier = new DKIMVerifier(keyRecordRetriever);
InputStream stream = null; // you need to provide the input stream of the mime message
List<SignatureRecord> verifiedSignatures = verifier.verify(stream);
// `verifiedSignatures` contains only the signatures that have successfully
// passed the validation.
// If you want to query all the results including all the failures, you can
// retrieve them from the verifier
List<Result> results = verifier.getResults();

Cryptography Notice

   This distribution includes cryptographic software.  The country in
   which you currently reside may have restrictions on the import,
   possession, use, and/or re-export to another country, of
   encryption software.  BEFORE using any encryption software, please
   check your country's laws, regulations and policies concerning the
   import, possession, or use, and re-export of encryption software, to
   see if this is permitted.  See http://www.wassenaar.org for more
   information.

   The U.S. Government Department of Commerce, Bureau of Industry and
   Security (BIS), has classified this software as Export Commodity
   Control Number (ECCN) 5D002.C.1, which includes information security
   software using or performing cryptographic functions with asymmetric
   algorithms.  The form and manner of this Apache Software Foundation
   distribution makes it eligible for export under the License Exception
   ENC Technology Software Unrestricted (TSU) exception (see the BIS
   Export Administration Regulations, Section 740.13) for both object
   code and source code.

   The following provides more details on the included cryptographic
   software:

    - jDKIM includes code designed to work with Java SE Security

    Export classifications and source links can be found
    at http://www.apache.org/licenses/exports/.