enclave_build: define and implement image manager trait

For future generalization of both Docker and OCI methods of build, the
`ImageManager` trait will be used to extract useful information from the
container image details.

Currently added the OCI implementation of the trait and it can be used
to pull, inspect and extract expressions from  an image just like the Docker
case. The same implementation will be added for Docker images.

enclave_build: add unit test for image manager

Added unit tests for image manager operations.

Signed-off-by: Calin-Alexandru Coman <[email protected]>
Signed-off-by: Raul-Ovidiu Moldovan <[email protected]>

enclave_build/src/docker.rs

@@ -1,8 +1,8 @@
 // Copyright 2019-2022 Amazon.com, Inc. or its affiliates. All Rights Reserved.
 // SPDX-License-Identifier: Apache-2.0
 
-use base64::{engine::general_purpose, Engine as _};
 use crate::{EnclaveBuildError, Result};
+use base64::{engine::general_purpose, Engine as _};
 use futures::stream::StreamExt;
 use log::{debug, info};
 use serde_json::{json, Value};

enclave_build/src/image.rs

@@ -4,6 +4,7 @@
 use crate::{EnclaveBuildError, Result};
 use serde::{de::DeserializeOwned, Deserialize, Serialize};
 use std::io::Read;
+use tempfile::NamedTempFile;
 
 use sha2::Digest;
 
@@ -53,6 +54,40 @@ impl ImageDetails {
     pub fn config(&self) -> &ImageConfiguration {
         &self.config
     }
+
+    /// Extracts from the image and returns the CMD and ENV expressions (in this order).
+    ///
+    /// If there are no CMD expressions found, it tries to locate the ENTRYPOINT command.
+    /// The returned result will contain the files needed for the YAML generator.
+    pub fn extract_expressions(&self) -> Result<(NamedTempFile, NamedTempFile)> {
+        // Get the expressions from the image
+        let config_section = self
+            .config
+            .config()
+            .as_ref()
+            .ok_or(EnclaveBuildError::ConfigError)?;
+
+        let cmd = config_section.cmd();
+        let env = config_section.env();
+        let entrypoint = config_section.entrypoint();
+
+        // If no CMD instructions are found, try to locate an ENTRYPOINT command
+        let (cmd, env) = match (cmd, env, entrypoint) {
+            (Some(cmd), Some(env), _) => Ok((cmd.to_vec(), env.to_vec())),
+            (_, Some(env), Some(entrypoint)) => Ok((entrypoint.to_vec(), env.to_vec())),
+            (_, _, Some(entrypoint)) => Ok((entrypoint.to_vec(), Vec::new())),
+            (_, _, _) => Err(EnclaveBuildError::ExtractError(
+                "Failed to locate ENTRYPOINT".to_string(),
+            )),
+        }?;
+
+        let cmd_file = crate::docker::write_config(cmd)
+            .map_err(|err| EnclaveBuildError::ExtractError(format!("{:?}", err)))?;
+        let env_file = crate::docker::write_config(env)
+            .map_err(|err| EnclaveBuildError::ExtractError(format!("{:?}", err)))?;
+
+        Ok((cmd_file, env_file))
+    }
 }
 
 /// URIs that are missing a domain will be converted to a reference using the Docker defaults.

enclave_build/src/image_manager.rs

@@ -4,12 +4,25 @@
 
 use std::convert::TryFrom;
 
+use log::warn;
 use oci_distribution::Reference;
+use tempfile::NamedTempFile;
 
 use crate::image::ImageDetails;
 use crate::storage::OciStorage;
 use crate::{EnclaveBuildError, Result};
 
+/// Trait which provides an interface for handling an image (OCI or Docker)
+pub trait ImageManager {
+    fn image_name(&self) -> &str;
+    /// Inspects the image and returns its metadata in the form of a JSON Value
+    fn inspect_image(&self) -> Result<serde_json::Value>;
+    /// Returns the architecture of the image
+    fn architecture(&self) -> Result<String>;
+    /// Returns two temp files containing the CMD and ENV expressions extracted from the image
+    fn extract_expressions(&self) -> Result<(NamedTempFile, NamedTempFile)>;
+}
+
 pub struct OciImageManager {
     /// Name of the container image.
     image_name: String,
@@ -25,16 +38,15 @@ impl OciImageManager {
         let image_name = normalize_tag(image_name)?;
 
         // The docker daemon is not used, so a local storage needs to be created
-        let storage =
-            match OciStorage::get_default_root_path().map_err(|err| eprintln!("{:?}", err)) {
-                Ok(root_path) => {
-                    // Try to create/read the storage. If the storage could not be created, log the error
-                    OciStorage::new(&root_path)
-                        .map_err(|err| eprintln!("{:?}", err))
-                        .ok()
-                }
-                Err(_) => None,
-            };
+        let storage = match OciStorage::get_default_root_path().map_err(|err| warn!("{:?}", err)) {
+            Ok(root_path) => {
+                // Try to create/read the storage. If the storage could not be created, log the error
+                OciStorage::new(&root_path)
+                    .map_err(|err| warn!("{:?}", err))
+                    .ok()
+            }
+            Err(_) => None,
+        };
 
         let image_details = Self::fetch_image_details(&image_name, storage).await?;
 
@@ -60,11 +72,7 @@ impl OciImageManager {
 
         let image_details = if let Some(storage) = local_storage {
             // Try to fetch the image from the storage
-            storage.fetch_image_details(image_name).map_err(|err| {
-                // Log the fetching error
-                eprintln!("{:?}", err);
-                err
-            })
+            storage.fetch_image_details(image_name)
         } else {
             Err(EnclaveBuildError::OciStorageNotFound(
                 "Local storage missing".to_string(),
@@ -74,15 +82,16 @@ impl OciImageManager {
         // If the fetching failed, pull it from remote and store it
         match image_details {
             Ok(details) => Ok(details),
-            Err(_) => {
+            Err(err) => {
+                warn!("Fetching from storage failed: {}", err);
                 // The image is not stored, so try to pull and then store it
                 let image_data = crate::pull::pull_image_data(image_name).await?;
 
                 // If the store operation fails, discard error and proceed with getting the details
                 if let Some(local_storage) = storage.as_mut() {
                     local_storage
                         .store_image_data(image_name, &image_data)
-                        .map_err(|err| eprintln!("Failed to store image: {:?}", err))
+                        .map_err(|err| warn!("Failed to store image: {:?}", err))
                         .ok();
                 }
 
@@ -105,8 +114,35 @@ fn normalize_tag(image_name: &str) -> Result<String> {
     }
 }
 
+impl ImageManager for OciImageManager {
+    fn image_name(&self) -> &str {
+        &self.image_name
+    }
+
+    /// Inspect the image and return its description as a JSON String.
+    fn inspect_image(&self) -> Result<serde_json::Value> {
+        // Serialize to a serde_json::Value
+        serde_json::to_value(&self.image_details).map_err(EnclaveBuildError::SerdeError)
+    }
+
+    /// Extracts the CMD and ENV expressions from the image and returns them each in a
+    /// temporary file
+    fn extract_expressions(&self) -> Result<(NamedTempFile, NamedTempFile)> {
+        self.image_details.extract_expressions()
+    }
+
+    /// Returns architecture information of the image.
+    fn architecture(&self) -> Result<String> {
+        Ok(format!("{}", self.image_details.config().architecture()))
+    }
+}
+
 #[cfg(test)]
-pub mod tests {
+mod tests {
+    use super::*;
+    use std::fs::File;
+    use std::io::Read;
+
     use sha2::Digest;
 
     use super::{normalize_tag, OciImageManager};
@@ -177,4 +213,37 @@ pub mod tests {
 
         assert_eq!(&config_hash, IMAGE_HASH);
     }
+
+    /// Test extracted configuration is as expected
+    #[tokio::test]
+    async fn test_config() {
+        #[cfg(target_arch = "x86_64")]
+        let image_manager = OciImageManager::new(
+            "667861386598.dkr.ecr.us-east-1.amazonaws.com/enclaves-samples:vsock-sample-server-x86_64",
+        ).await.unwrap();
+        #[cfg(target_arch = "aarch64")]
+        let mut image_manager = OciImageManager::new(
+            "667861386598.dkr.ecr.us-east-1.amazonaws.com/enclaves-samples:vsock-sample-server-aarch64",
+        ).await.unwrap();
+
+        let (cmd_file, env_file) = image_manager.extract_expressions().unwrap();
+        let mut cmd_file = File::open(cmd_file.path()).unwrap();
+        let mut env_file = File::open(env_file.path()).unwrap();
+
+        let mut cmd = String::new();
+        cmd_file.read_to_string(&mut cmd).unwrap();
+        assert_eq!(
+            cmd,
+            "/bin/sh\n\
+             -c\n\
+             ./vsock-sample server --port 5005\n"
+        );
+
+        let mut env = String::new();
+        env_file.read_to_string(&mut env).unwrap();
+        assert_eq!(
+            env,
+            "PATH=/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin\n"
+        );
+    }
 }

enclave_build/src/storage.rs

@@ -277,7 +277,6 @@ impl OciStorage {
                     err
                 ))
             })?
-            .into_iter()
             // Get only the valid directory entries that are valid files and return (name, file) pair
             .filter_map(|entry| match entry {
                 Ok(dir_entry) => match File::open(dir_entry.path()) {