Programming Tutorials

Verifying a Signed JAR File example

By: Grenfel in Java Tutorials on 2007-10-14  

To verify a signed JAR file, that is, to verify that the signature is valid and the JAR file has not been tampered with, use a command such as the following:

    jarsigner -verify sbundle.jar 

If the verification is successful,

    jar verified.

is displayed. Otherwise, an error message appears.

You can get more information if you use the -verbose option. A sample use of jarsigner with the -verbose option is shown below, along with sample output:

    jarsigner -verify -verbose sbundle.jar

           198 Fri Sep 26 16:14:06 PDT 1997 META-INF/MANIFEST.MF
           199 Fri Sep 26 16:22:10 PDT 1997 META-INF/JANE.SF
          1013 Fri Sep 26 16:22:10 PDT 1997 META-INF/JANE.DSA
    smk   2752 Fri Sep 26 16:12:30 PDT 1997 AclEx.class
    smk    849 Fri Sep 26 16:12:46 PDT 1997 test.class

      s = signature was verified
      m = entry is listed in manifest
      k = at least one certificate was found in keystore

    jar verified.

Verification with Certificate Information

If you specify the -certs option when verifying, along with the -verify and -verbose options, the output includes certificate information for each signer of the JAR file, including the certificate type, the signer distinguished name information (iff it's an X.509 certificate), and, in parentheses, the keystore alias for the signer if the public key certificate in the JAR file matches that in a keystore entry. For example,

    jarsigner -keystore /working/mystore -verify -verbose -certs myTest.jar

           198 Fri Sep 26 16:14:06 PDT 1997 META-INF/MANIFEST.MF
           199 Fri Sep 26 16:22:10 PDT 1997 META-INF/JANE.SF
          1013 Fri Sep 26 16:22:10 PDT 1997 META-INF/JANE.DSA
           208 Fri Sep 26 16:23:30 PDT 1997 META-INF/JAVATEST.SF
          1087 Fri Sep 26 16:23:30 PDT 1997 META-INF/JAVATEST.DSA
    smk   2752 Fri Sep 26 16:12:30 PDT 1997 Tst.class

      X.509, CN=Test Group, OU=Java Software, O=Sun Microsystems, L=CUP, S=CA, C=US (javatest)
      X.509, CN=Jane Smith, OU=Java Software, O=Sun, L=cup, S=ca, C=us (jane)

      s = signature was verified
      m = entry is listed in manifest
      k = at least one certificate was found in keystore

    jar verified.

If the certificate for a signer is not an X.509 certificate, there is no distinguished name information. In that case, just the certificate type and the alias are shown. For example, if the certificate is a PGP certificate, and the alias is "bob", you'd get

      PGP, (bob)

Verification of a JAR File that Includes Identity Database Signers

If a JAR file has been signed using the JDK 1.1 javakey tool, and thus the signer is an alias in an identity database, the verification output includes an "i" symbol. If the JAR file has been signed by both an alias in an identity database and an alias in a keystore, both "k" and "i" appear.

When the -certs option is used, any identity database aliases are shown in square brackets rather than the parentheses used for keystore aliases. For example:

    jarsigner -keystore /working/mystore -verify -verbose -certs writeFile.jar

           198 Fri Sep 26 16:14:06 PDT 1997 META-INF/MANIFEST.MF
           199 Fri Sep 26 16:22:10 PDT 1997 META-INF/JANE.SF
          1013 Fri Sep 26 16:22:10 PDT 1997 META-INF/JANE.DSA
           199 Fri Sep 27 12:22:30 PDT 1997 META-INF/DUKE.SF
          1013 Fri Sep 27 12:22:30 PDT 1997 META-INF/DUKE.DSA
   smki   2752 Fri Sep 26 16:12:30 PDT 1997 writeFile.html

      X.509, CN=Jane Smith, OU=Java Software, O=Sun, L=cup, S=ca, C=us (jane)
      X.509, CN=Duke, OU=Java Software, O=Sun, L=cup, S=ca, C=us [duke]

      s = signature was verified
      m = entry is listed in manifest
      k = at least one certificate was found in keystore
      i = at least one certificate was found in identity scope

    jar verified.

Note that the alias "duke" is in brackets to denote that it is an identity database alias, not a keystore alias.