maven-gpg-plugin failing with "Inappropriate ioctl for device" when running under Jenkins

When Jenkins triggers maven-gpg-plugin in a remote Linux shell it fails with gpg: signing failed: Inappropriate ioctl for device. This used to work until recently. I don't know what changed.

I found a lot of online references suggesting export GPG_TTY=$(tty) but this doesn't work for ssh connections as tty is null. Any ideas?

I found an excellent explanation over at https://myshittycode.com/2017/08/07/maven-gpg-plugin-prevent-signing-prompt-or-gpg-signing-failed-no-such-file-or-directory-error/

I will re-post the gist of the post in case the page goes down:

If you 1) initially had it working in the past, and 2) have tried all sorts of solutions from the web, and still couldn’t get it working, chances are you have unconsciously upgraded GPG version from 2.0 to 2.1.

Sounds about right...

To fix this, GPG 2.1 requires --pinentry-mode to be set to loopback in order to pick up gpg.passphrase value defined in Maven settings.xml.

So, update Maven GPG Plugin configuration in pom.xml to the following:

<plugin>
    <groupId>org.apache.maven.plugins</groupId>
    <artifactId>maven-gpg-plugin</artifactId>
    <version>1.6</version>
    <executions>
        <execution>
            <id>sign-artifacts</id>
            <phase>verify</phase>
            <goals>
                <goal>sign</goal>
            </goals>
            <configuration>
                <gpgArguments>
                    <arg>--pinentry-mode</arg>
                    <arg>loopback</arg>
                </gpgArguments>
            </configuration>
        </execution>
    </executions>
</plugin>