Cannot connect to ceph object stroage

[cffan]

We use ceph as our internal s3 storage. When using this plugin, this error occurs:

Caused: com.amazonaws.SdkClientException: Unable to execute HTTP request: The target server failed to respond
	at com.amazonaws.http.AmazonHttpClient$RequestExecutor.handleRetryableException(AmazonHttpClient.java:1116)
	at com.amazonaws.http.AmazonHttpClient$RequestExecutor.executeHelper(AmazonHttpClient.java:1066)
	at com.amazonaws.http.AmazonHttpClient$RequestExecutor.doExecute(AmazonHttpClient.java:743)
	at com.amazonaws.http.AmazonHttpClient$RequestExecutor.executeWithTimer(AmazonHttpClient.java:717)
	at com.amazonaws.http.AmazonHttpClient$RequestExecutor.execute(AmazonHttpClient.java:699)
	at com.amazonaws.http.AmazonHttpClient$RequestExecutor.access$500(AmazonHttpClient.java:667)
	at com.amazonaws.http.AmazonHttpClient$RequestExecutionBuilderImpl.execute(AmazonHttpClient.java:649)
	at com.amazonaws.http.AmazonHttpClient.execute(AmazonHttpClient.java:513)
	at com.amazonaws.services.s3.AmazonS3Client.invoke(AmazonS3Client.java:4365)
	at com.amazonaws.services.s3.AmazonS3Client.invoke(AmazonS3Client.java:4312)
	at com.amazonaws.services.s3.AmazonS3Client.invoke(AmazonS3Client.java:4306)
	at com.amazonaws.services.s3.AmazonS3Client.listObjects(AmazonS3Client.java:840)
	at de.taimos.pipeline.aws.S3FindFilesStep$Execution.run(S3FindFilesStep.java:216)
	at de.taimos.pipeline.aws.S3FindFilesStep$Execution.run(S3FindFilesStep.java:148)
	at org.jenkinsci.plugins.workflow.steps.SynchronousNonBlockingStepExecution$1$1.call(SynchronousNonBlockingStepExecution.java:49)
	at hudson.security.ACL.impersonate(ACL.java:260)
	at org.jenkinsci.plugins.workflow.steps.SynchronousNonBlockingStepExecution$1.run(SynchronousNonBlockingStepExecution.java:46)
	at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:511)
	at java.util.concurrent.FutureTask.run(FutureTask.java:266)
	at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)
	at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
	at java.lang.Thread.run(Thread.java:748)

After some searching, this seems to be the most likely cause. Is it possible to add signer type argument to withAWS?