HADOOP-17817. Throw an exception if S3 client-side encryption is enabled on S3Guard enabled bucket

Author: Mehakmeet Singh

hadoop-tools/hadoop-aws/src/main/java/org/apache/hadoop/fs/s3a/S3AFileSystem.java

@@ -539,6 +539,9 @@ public void initialize(URI name, Configuration originalConf)
       if (hasMetadataStore()) {
         LOG.debug("Using metadata store {}, authoritative store={}, authoritative path={}",
             getMetadataStore(), allowAuthoritativeMetadataStore, allowAuthoritativePaths);
+        if (isCSEEnabled) {
+          throw new RuntimeException("Disable S3-CSE if S3Guard is enabled.");
+        }
       }
 
       // LOG if S3Guard is disabled on the warn level set in config

hadoop-tools/hadoop-aws/src/site/markdown/tools/hadoop-aws/encryption.md

@@ -601,6 +601,7 @@ clients where S3-CSE has not been enabled.
 
 ### Limitations
 
+- S3Guard is not supported with S3-CSE.
 - Performance will be reduced. All encrypt/decrypt is now being done on the
  client.
 - Writing files may be slower, as only a single block can be encrypted and

hadoop-tools/hadoop-aws/src/site/markdown/tools/hadoop-aws/troubleshooting_s3a.md

@@ -1435,6 +1435,31 @@ The user trying to use the KMS Key ID should have the right permissions to acces
 If not, then add permission(or IAM role) in "Key users" section by selecting the
 AWS-KMS CMK Key on AWS console.
 
+### Disable S3-CSE if S3Guard is enabled
+
+S3-CSE not supported for S3Guard enabled buckets.
+```
+java.lang.RuntimeException: Disable S3-CSE if S3Guard is enabled.
+    at org.apache.hadoop.fs.s3a.S3AFileSystem.initialize(S3AFileSystem.java:543)
+    at org.apache.hadoop.fs.FileSystem.createFileSystem(FileSystem.java:3460)
+    at org.apache.hadoop.fs.FileSystem.access$300(FileSystem.java:172)
+    at org.apache.hadoop.fs.FileSystem$Cache.getInternal(FileSystem.java:3565)
+    at org.apache.hadoop.fs.FileSystem$Cache.get(FileSystem.java:3512)
+    at org.apache.hadoop.fs.FileSystem.get(FileSystem.java:539)
+    at org.apache.hadoop.fs.Path.getFileSystem(Path.java:366)
+    at org.apache.hadoop.fs.shell.PathData.expandAsGlob(PathData.java:342)
+    at org.apache.hadoop.fs.shell.Command.expandArgument(Command.java:252)
+    at org.apache.hadoop.fs.shell.Command.expandArguments(Command.java:235)
+    at org.apache.hadoop.fs.shell.FsCommand.processRawArguments(FsCommand.java:105)
+    at org.apache.hadoop.fs.shell.Command.run(Command.java:179)
+    at org.apache.hadoop.fs.FsShell.run(FsShell.java:327)
+    at org.apache.hadoop.util.ToolRunner.run(ToolRunner.java:81)
+    at org.apache.hadoop.util.ToolRunner.run(ToolRunner.java:95)
+    at org.apache.hadoop.fs.FsShell.main(FsShell.java:390)
+```
+If you want to use S3Guard then disable S3-CSE or disable S3Guard if you want
+to use S3-CSE.
+
 ### <a name="not_all_bytes_were_read"></a> Message appears in logs "Not all bytes were read from the S3ObjectInputStream"