feat: fail build if it produces an artifact that's too large

Sponsored-by: author

4 files changed, 55 insertions, 2 deletions

diff --git a/ambient-run.md b/ambient-run.md
index 7d3ab68..82eccab 100644
--- a/ambient-run.md
+++ b/ambient-run.md
@@ -166,6 +166,7 @@ shell: |
   cargo test
 image: /my/image.qcow2
 artifact: null
+artifact_max_size: null
 ~~~
 
 ### Show per-build configuration
@@ -285,6 +286,36 @@ shell: |
 image: image.qcow2
 ~~~
 
+### Fail build that tries to produce an oversize artifact
+
+_Requirement:_ If a build produces an artifact that is too large, the
+build should fail.
+
+_Justification:_ Without a limit, a malicious build could fill all
+available storage space, which is a denial-of-service attack.
+
+_Stakeholder:_ Lars.
+
+~~~scenario
+given an installed ambient-run
+given file small-artifact-project.yaml
+given file foo/README.md from foo-project.yaml
+given image file image.qcow2 specified for test suite
+when I run ambient-run build small-artifact-project.yaml --log foo.log
+then file foo.log contains "EXIT CODE: 2"
+~~~
+
+
+~~~{#small-artifact-project.yaml .file .yaml}
+source: foo
+shell: |
+  #!/bin/bash
+  tar -cf /dev/vdc .
+image: image.qcow2
+artifact: foo.tar
+artifact_max_size: 1
+~~~
+
 ### Build is given dependencies
 ### Cache is persistent between builds
 ### Build gets the resources is demands
diff --git a/src/bin/ambient-run.rs b/src/bin/ambient-run.rs
index 3dc778e..37054c2 100644
--- a/src/bin/ambient-run.rs
+++ b/src/bin/ambient-run.rs
@@ -216,7 +216,8 @@ impl BuildCommand {
         let mut qemu = Qemu::new(&project.image())
             .with_shell(project.shell())
             .with_source(&project.source())
-            .with_artifact(project.artifact());
+            .with_artifact(project.artifact())
+            .with_artifact_max_size(project.artifact_max_size());
         if let Some(log) = &self.log {
             qemu = qemu.with_log(log);
         }
diff --git a/src/project.rs b/src/project.rs
index b381734..76f42dc 100644
--- a/src/project.rs
+++ b/src/project.rs
@@ -13,6 +13,7 @@ pub struct Project {
     shell: String,
     image: PathBuf,
     artifact: Option<PathBuf>,
+    artifact_max_size: Option<u64>,
 }
 
 impl Project {
@@ -45,6 +46,7 @@ impl Project {
             shell: "".into(),
             image,
             artifact: None,
+            artifact_max_size: None,
         };
         project.add_from(filename)?;
         if project.shell.is_empty() {
@@ -71,6 +73,7 @@ impl Project {
             self.image = x;
         }
         self.artifact = snippet.artifact;
+        self.artifact_max_size = snippet.artifact_max_size;
         Ok(())
     }
 
@@ -98,6 +101,11 @@ impl Project {
     pub fn artifact(&self) -> &Option<PathBuf> {
         &self.artifact
     }
+
+    /// Artifact file max size.
+    pub fn artifact_max_size(&self) -> Option<u64> {
+        self.artifact_max_size.clone()
+    }
 }
 
 #[derive(Debug, Deserialize)]
@@ -107,6 +115,7 @@ struct ProjectSnippet {
     shell: Option<String>,
     image: Option<PathBuf>,
     artifact: Option<PathBuf>,
+    artifact_max_size: Option<u64>,
 }
 
 /// Possible errors from configuration file handling.
diff --git a/src/qemu.rs b/src/qemu.rs
index 3450101..4c6efff 100644
--- a/src/qemu.rs
+++ b/src/qemu.rs
@@ -19,6 +19,7 @@ pub struct Qemu {
     source: PathBuf,
     shell: Option<String>,
     artifact: Option<PathBuf>,
+    artifact_max_xize: u64,
 }
 
 impl Qemu {
@@ -27,6 +28,7 @@ impl Qemu {
         Self {
             image: image.into(),
             source: PathBuf::from("."),
+            artifact_max_xize: MAX_OUTPUT_SIZE,
             ..Default::default()
         }
     }
@@ -55,6 +57,12 @@ impl Qemu {
         self
     }
 
+    /// Set maximum length of output artifact.
+    pub fn with_artifact_max_size(mut self, size: Option<u64>) -> Self {
+        self.artifact_max_xize = size.unwrap_or(MAX_OUTPUT_SIZE);
+        self
+    }
+
     /// Run QEMU in the specified way.
     pub fn run(&self) -> Result<(), QemuError> {
         eprintln!("qemu run");
@@ -71,7 +79,11 @@ impl Qemu {
         eprintln!("output drive");
         let output_drive = if let Some(filename) = &self.artifact {
             eprintln!("output to {}", filename.display());
-            Self::create_tar_with_size(filename.to_path_buf(), empty.path(), MAX_OUTPUT_SIZE)?
+            Self::create_tar_with_size(
+                filename.to_path_buf(),
+                empty.path(),
+                self.artifact_max_xize,
+            )?
         } else {
             eprintln!("empty output drive");
             Self::create_tar_with_size(tmp.path().join("output"), empty.path(), 0)?