Backup: exit non-zero if new tags are found

2 files changed, 11 insertions, 2 deletions

diff --git a/src/cmd/backup.rs b/src/cmd/backup.rs
index 496477e..04dfb05 100644
--- a/src/cmd/backup.rs
+++ b/src/cmd/backup.rs
@@ -49,7 +49,7 @@ impl Backup {
 
         if is_incremental && !outcome.new_cachedir_tags.is_empty() {
             println!("New CACHEDIR.TAG files since the last backup:");
-            for t in outcome.new_cachedir_tags {
+            for t in &outcome.new_cachedir_tags {
                 println!("- {:?}", t);
             }
             println!("You can configure Obnam to ignore all such files by setting `exclude_cache_tag_directories` to `false`.");
@@ -62,7 +62,11 @@ impl Backup {
             outcome.warnings.len(),
         )?;
 
-        Ok(())
+        if is_incremental && !outcome.new_cachedir_tags.is_empty() {
+            Err(ObnamError::NewCachedirTagsFound)
+        } else {
+            Ok(())
+        }
     }
 }
 
diff --git a/src/error.rs b/src/error.rs
index e4d77d3..30571ec 100644
--- a/src/error.rs
+++ b/src/error.rs
@@ -52,4 +52,9 @@ pub enum ObnamError {
 
     #[error(transparent)]
     SerdeJsonError(#[from] serde_json::Error),
+
+    #[error(
+        "found CACHEDIR.TAG files that aren't present in the previous backup, might be an attack"
+    )]
+    NewCachedirTagsFound,
 }