Release Note: Disabled SHA-1 Signed JARs

JARs signed with SHA-1 algorithms are now restricted by default and treated as if they were unsigned. This applies to the algorithms used to digest, sign, and optionally timestamp the JAR. It also applies to the signature and digest algorithms of the certificates in the certificate chain of the code signer and the Timestamp Authority, and any CRLs or OCSP responses that are used to verify if those certificates have been revoked.

To reduce the compatibility risk for applications that have been previously timestamped, there is one exception to this policy:

- Any JAR signed with SHA-1 algorithms and timestamped prior to January 01, 2019 will not be restricted.

This exception might be removed in a future JDK release.

JARs affected by these new restrictions should be replaced or re-signed with stronger algorithms.

To find out if your signed JARs may be affected by this change, run `jarsigner -verify -verbose -certs` on the signed JAR, and look for instances of "SHA1" or "SHA-1" in the output.

For example:

  ```
  Signed by "CN="ee""
     Digest algorithm: SHA-1 (disabled)
     Signature algorithm: SHA1withRSA (disabled), 2048-bit key
  ```

If your JAR is timestamped, check the output for the date it was timestamped on and check if it is on or after January 01, 2019. For example:

  ```
  Timestamped by "CN="tsa"" on Tue Jun 16 03:20:48 UTC 2020
  ```

Users can, at their own risk, remove these restrictions by modifying the `java.security` configuration file (or override it by using the `java.security.properties` system property) and removing "SHA1 usage SignedJAR & denyAfter 2019-01-01" from the `jdk.certpath.disabledAlgorithms` security property and "SHA1 denyAfter 2019-01-01" from the `jdk.jar.disabledAlgorithms` security property.