MDEV-25343 Error log message not helpful when filekey is too long

Add a test related to the Encrypted Key File by following instructions in kb example
https://mariadb.com/kb/en/file-key-management-encryption-plugin/#creating-the-key-file

Reviewed by Daniel Black (with minor formatting and re-org of duplicate
close(f) calls).

1 files changed, 12 insertions, 3 deletions

diff --git a/plugin/file_key_management/parser.cc b/plugin/file_key_management/parser.cc
index 5a9e5e55d63..ec1b528da24 100644
--- a/plugin/file_key_management/parser.cc
+++ b/plugin/file_key_management/parser.cc
@@ -170,19 +170,28 @@ bool Parser::read_filekey(const char *filekey, char *secret)
   int f= open(filekey, O_RDONLY|O_BINARY);
   if (f == -1)
   {
-    my_error(EE_FILENOTFOUND,ME_ERROR_LOG, filekey, errno);
+    my_error(EE_FILENOTFOUND, ME_ERROR_LOG, filekey, errno);
     return 1;
   }
 
-  int len= read(f, secret, MAX_SECRET_SIZE);
+  int len= read(f, secret, MAX_SECRET_SIZE + 1);
   if (len <= 0)
   {
-    my_error(EE_READ,ME_ERROR_LOG, filekey, errno);
+    my_error(EE_READ, ME_ERROR_LOG, filekey, errno);
     close(f);
     return 1;
   }
   close(f);
+
   while (secret[len - 1] == '\r' || secret[len - 1] == '\n') len--;
+  if (len > MAX_SECRET_SIZE)
+  {
+    my_printf_error(EE_READ,
+                    "Cannot read %s, the filekey is too long, "
+                    "max secret size is %dB ",
+                    ME_ERROR_LOG, filekey, MAX_SECRET_SIZE);
+    return 1;
+  }
   secret[len]= '\0';
   return 0;
 }