Basic check of user data structure for errors

virtweb_backend/src/libvirt_rest_structures/mod.rs

@@ -13,4 +13,6 @@ enum LibVirtStructError {
     ParseFilteringChain(String),
     #[error("NetworkFilterExtractionError: {0}")]
     NetworkFilterExtraction(String),
+    #[error("CloudInitConfigurationError: {0}")]
+    CloudInitConfiguration(String),
 }

virtweb_backend/src/libvirt_rest_structures/vm.rs

@@ -3,7 +3,9 @@ use crate::constants;
 use crate::libvirt_lib_structures::XMLUuid;
 use crate::libvirt_lib_structures::domain::*;
 use crate::libvirt_rest_structures::LibVirtStructError;
-use crate::libvirt_rest_structures::LibVirtStructError::StructureExtraction;
+use crate::libvirt_rest_structures::LibVirtStructError::{
+    CloudInitConfiguration, StructureExtraction,
+};
 use crate::utils::cloud_init_utils::CloudInitConfig;
 use crate::utils::file_size_utils::FileSize;
 use crate::utils::files_utils;
@@ -142,6 +144,10 @@ impl VMInfo {
             return Err(StructureExtraction("Invalid number of vCPU specified!").into());
         }
 
+        if let Some(e) = self.cloud_init.check_error() {
+            return Err(CloudInitConfiguration(e).into());
+        }
+
         let mut iso_absolute_files = vec![];
 
         // Process cloud init image

virtweb_backend/src/utils/cloud_init_utils.rs

@@ -35,6 +35,27 @@ pub struct CloudInitConfig {
 }
 
 impl CloudInitConfig {
+    /// Check cloud init configuration
+    pub fn check_error(&self) -> Option<String> {
+        if !self.user_data.is_empty() {
+            // Check YAML content
+            if let Err(e) = serde_yml::from_str::<serde_json::Value>(&self.user_data) {
+                return Some(format!(
+                    "user data is an invalid YAML file! Deserialization error: {e}"
+                ));
+            }
+
+            // Check first line
+            if !self.user_data.starts_with("#cloud-config\n") {
+                return Some(
+                    "user data file MUST start with '#cloud-config' as first line!".to_string(),
+                );
+            }
+        }
+
+        None
+    }
+
     /// Generate disk image for nocloud usage
     pub fn generate_nocloud_disk(&self) -> anyhow::Result<Vec<u8>> {
         let temp_path = tempfile::tempdir_in(&AppConfig::get().temp_dir)?;