Fetch an image from the Docker Registry
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parent
9f33ac46b2
commit
c44452648d
17
src/main.rs
17
src/main.rs
@ -1,18 +1,24 @@
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use std::{self, ffi::CString, path};
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mod registry;
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// Usage: your_docker.sh run <image> <command> <arg1> <arg2> ...
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fn main() {
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let args: Vec<_> = std::env::args().collect();
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let image_name = &args[2];
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let command = &args[3];
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let command_args = &args[4..];
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let base = "/tmp/mydocker";
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let base_path = path::Path::new(base);
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let base_path = std::env::temp_dir().join("mydocker");
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// prevent cryptic "no such file or directory" error inside chroot
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std::fs::create_dir_all(base_path.join("dev")).unwrap();
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std::fs::File::create(base_path.join("dev/null")).unwrap();
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let image = registry::ImageIdentifier::from_string(image_name);
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let mut reg = registry::Registry::default();
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reg.pull(&image, base_path.to_str().unwrap());
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// copy over binary into chroot
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let command_path = path::Path::new(command).strip_prefix("/").unwrap();
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std::fs::create_dir_all(base_path.join(command_path.parent().unwrap()))
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@ -21,7 +27,7 @@ fn main() {
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.expect("Failed copying executed binary to chroot directory");
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// create and change into chroot
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let cbase_path = CString::new(base.to_owned()).unwrap();
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let cbase_path = CString::new(base_path.to_str().unwrap().to_owned()).unwrap();
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unsafe {
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libc::chroot(cbase_path.as_ptr());
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}
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@ -43,8 +49,5 @@ fn main() {
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let std_err = std::str::from_utf8(&output.stderr).unwrap();
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eprint!("{}", std_err);
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match output.status.code() {
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Some(code) => std::process::exit(code),
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None => std::process::exit(1),
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}
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std::process::exit(output.status.code().unwrap_or(1));
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}
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92
src/registry.rs
Normal file
92
src/registry.rs
Normal file
@ -0,0 +1,92 @@
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// TODO: Enable derive feature
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pub struct Registry {
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http_client: reqwest::blocking::Client,
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}
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impl Default for Registry {
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fn default() -> Self {
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return Registry {
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http_client: reqwest::blocking::Client::new(),
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};
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}
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}
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impl Registry {
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pub fn pull(&mut self, image: &ImageIdentifier, destination: &str) {
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// Perform the little auth dance
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let auth_url = format!("https://auth.docker.io/token?service=registry.docker.io&scope=repository%3A{}%2F{}%3Apull", image.author, image.name);
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let auth: serde_json::Value = self
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.http_client
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.get(&auth_url)
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.send()
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.unwrap()
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.json()
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.unwrap();
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let access_token = auth["token"].as_str().unwrap();
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// Download the image manifest
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let auth_header = format!("Bearer {}", access_token);
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let image_url = format!(
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"https://registry.hub.docker.com/v2/{}/{}/manifests/{}",
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image.author, image.name, image.tag
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);
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let image_manifest: serde_json::Value = self
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.http_client
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.get(&image_url)
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.header(reqwest::header::AUTHORIZATION, auth_header.to_owned())
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.send()
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.unwrap()
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.json()
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.unwrap();
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// Download the image layers and extracts them
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let temp_path = std::env::temp_dir();
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for layer in image_manifest["fsLayers"].as_array().unwrap() {
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let digest = layer["blobSum"].as_str().unwrap();
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let blob_url = format!(
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"https://registry.hub.docker.com/v2/{}/{}/blobs/{}",
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image.author, image.name, digest
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);
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let blob = self
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.http_client
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.get(&blob_url)
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.header(reqwest::header::AUTHORIZATION, auth_header.to_owned())
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.send()
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.unwrap()
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.bytes()
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.unwrap();
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let layer_path = temp_path.join(digest);
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std::fs::write(layer_path.to_owned(), blob).unwrap();
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// TODO: handle exit code of untar
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std::process::Command::new("tar")
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.args(["-xf", layer_path.to_str().unwrap(), "-C", destination])
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.output()
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.unwrap();
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std::fs::remove_file(layer_path).unwrap();
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}
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}
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}
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pub struct ImageIdentifier {
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author: String,
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name: String,
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tag: String,
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}
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impl ImageIdentifier {
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pub fn from_string(image: &String) -> Self {
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let mut iter = image.rsplitn(2, ':');
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let tag = iter.next().unwrap_or("latest").to_string();
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let mut loc_iter = iter.next().unwrap().split('/').rev();
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let name = loc_iter
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.next()
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.expect("No image name was supplied")
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.to_string();
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let author = loc_iter.next().unwrap_or("library").to_string();
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return ImageIdentifier { author, name, tag };
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}
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}
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