Security Experts:

Oracle Will Stop Trusting MD5-Signed JAR Files in April

Oracle has decided to give Java developers more time to ensure that their JAR files are not signed with the MD5 algorithm. Java Runtime Environment (JRE) will no longer trust these types of files starting with April 2017.

The company announced in October plans to stop trusting JAR files signed with the MD5 algorithm, which has been known to have collision vulnerabilities for more than a decade. Oracle stopped using MD5 as the default JAR signing option in 2006 and the company now wants to take things even further.

Starting with Java SE 8u131, scheduled for release with the April 2017 Critical Patch Update (CPU), JAR files signed with MD5 will be treated as unsigned files and will not be trusted. Oracle had initially planned to stop trusting MD5-signed files in January 2017, but some developers have requested additional time to prepare for this change.

Developers have been advised to check if their JAR files have been signed using MD5 and re-sign them with a stronger algorithm or key size. The following command can be used in the Zip utility to remove existing MD5 signatures:

zip -d test.jar 'META-INF/*.SF' 'META-INF/*.RSA' 'META-INF/*.DSA'

“If you are using JARS you did not sign or build yourself, you need to contact your vendor for more information,” explained Oracle’s Erik Costlow in October. “If it can no longer be established if a JAR you are using has been signed with MD5, the recommended practice is to re-sign affected JAR files using a more modern algorithm.”

Other cryptography-related changes planned by Oracle this year for JRE and JDK include disabling SHA-1 in certificate chains anchored by roots included by default in JDK, and increasing the minimum key length for SSL and TLS to 1024 bits.

Oracle’s latest CPU patches a total of 270 vulnerabilities across its products, including 158 weaknesses that can be exploited remotely by an unauthenticated attacker. A significant number of flaws have been found in Oracle’s E-Business Suite, which seems to have attracted the attention of researchers recently.

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Eduard Kovacs (@EduardKovacs) is a contributing editor at SecurityWeek. He worked as a high school IT teacher for two years before starting a career in journalism as Softpedia’s security news reporter. Eduard holds a bachelor’s degree in industrial informatics and a master’s degree in computer techniques applied in electrical engineering.