don't make RocksDB startup fail with 0-byte log files (#9208)

3rdParty/rocksdb/6.2/env/env_encryption.cc

@@ -895,11 +895,16 @@ Status CTREncryptionProvider::CreateCipherStream(
 
   // If the prefix is smaller than twice the block size, we would below read a
   // very large chunk of the file (and very likely read over the bounds)
-  assert(prefix.size() >= 2 * blockSize);
   if (prefix.size() < 2 * blockSize) {
+    if (prefix.size() == 0) {
+      return CreateCipherStreamFromPrefix(fname, options, 0, rocksdb::Slice(), prefix, result);
+    }
+
     return Status::Corruption("Unable to read from file " + fname +
                               ": read attempt would read beyond file bounds");
   }
+  
+  assert(prefix.size() >= 2 * blockSize);
 
   // Decrypt the encrypted part of the prefix, starting from block 2 (block 0, 1 with initial counter & IV are unencrypted)
   CTRCipherStream cipherStream(cipher_, iv.data(), initialCounter);

js/client/modules/@arangodb/testsuites/recovery.js

@@ -51,6 +51,15 @@ const testPaths = {
 // //////////////////////////////////////////////////////////////////////////////
 
 function runArangodRecovery (params) {
+  let useEncryption = false;
+
+  if (params && params.options.storageEngine === 'rocksdb' && global.ARANGODB_CLIENT_VERSION) {
+    let version = global.ARANGODB_CLIENT_VERSION(true);
+    if (version.hasOwnProperty('enterprise-version')) {
+      useEncryption = true;
+    }
+  }
+
   let argv = [];
 
   let binary = pu.ARANGOD_BIN;
@@ -81,6 +90,11 @@ function runArangodRecovery (params) {
       'replication.auto-start': 'true',
       'javascript.script': params.script
     });
+
+    if (useEncryption) {
+      args['rocksdb.encryption-keyfile'] = tu.pathForTesting('server/recovery/encryption-keyfile');
+    }
+
     params.args = args;
 
     argv = toArgv(

tests/js/server/recovery/encryption-keyfile

@@ -0,0 +1 @@
+01234567890123456789012345678901