polyc_runtime/

ghcr.rs

//! Shared OCI-registry helpers: the published-component roster plus immutable
//! manifest-digest resolution, registry-agnostic.
//!
//! The cluster-upgrade path lives in two binaries — the operator CLI's
//! executor (`polychrome upgrade --cluster`) rolls the images, and the control
//! plane's mailbox originator captures the digests when it opens the approval
//! ask. Both must agree on *which* images are published, *where* they live, and
//! *how* a version's tag resolves to an immutable `sha256:…` content address, so
//! that logic lives here once rather than duplicated per binary.
//!
//! Where the images live is configuration, not a constant. The open-source
//! default is the public GHCR repositories; a private deployment overrides each
//! component's full image reference (registry host + repository) through the
//! `POLYCHROME_UPGRADE_IMAGE_*` environment variables — for example a Google
//! Artifact Registry path like
//! `us-east4-docker.pkg.dev/<project>/docker/polychrome-control-plane`. The
//! reference carries no tag; the tag is derived from the target version.
//!
//! Resolution follows the OCI distribution flow: obtain a bearer token for the
//! registry, `GET` the manifest, and read the registry-computed
//! `Docker-Content-Digest` header — the canonical content address pinned onto
//! the cluster. We never float a tag onto a running cluster. Which credential
//! the token comes from depends on the registry host: a public GHCR repository
//! uses the anonymous pull-token endpoint, while Google Artifact Registry / GCR
//! uses a GCP OAuth access token.

use std::time::Duration;

/// Registry host assumed when a configured image reference names no host (the
/// standard Docker heuristic: a leading path segment without a `.` or `:` is a
/// repository namespace, not a registry).
const DEFAULT_REGISTRY: &str = "ghcr.io";

/// Bounds the registry TCP connect so a dead host fails fast.
const CONNECT_TIMEOUT: Duration = Duration::from_secs(5);

/// Overall per-request budget for a registry round-trip.
const REQUEST_TIMEOUT: Duration = Duration::from_secs(30);

/// A digest-resolution failure.
///
/// A library error (`thiserror`) so callers on `anyhow` can add context and
/// callers on `thiserror` can wrap it.
#[derive(Debug, thiserror::Error)]
pub enum GhcrError {
    /// The target version did not parse as semver (so it can't map to a
    /// published image tag).
    #[error("target version `{0}` is not valid semver")]
    Version(String),
    /// The HTTP client could not be built or a request failed in transport.
    #[error("registry request failed: {0}")]
    Http(#[from] reqwest::Error),
    /// The registry accepted the request but returned no usable body/header
    /// (no token, or no digest header on the manifest response).
    #[error("registry response for {repo} had no {what}")]
    Malformed {
        /// The image repository the request was for.
        repo: String,
        /// What was missing (`pull token` / `digest header`).
        what: &'static str,
    },
    /// A GCP access token could not be obtained for a `*.pkg.dev` / `*.gcr.io`
    /// registry, so the digest cannot be resolved. Fail closed rather than fall
    /// back to an anonymous request that would 401.
    #[error("could not obtain a GCP access token for registry `{registry}`: {reason}")]
    GcpToken {
        /// The registry host the token was needed for.
        registry: String,
        /// Why the token could not be obtained.
        reason: String,
    },
}

/// One published component the cluster upgrade rolls.
///
/// Carries a short stable `name` (also the key an operator decision's signed
/// digest set is keyed on and the `--digest <name>=…` CLI arg uses), the
/// `Deployment` resource name, the `container` name inside the pod spec, the
/// environment variable that overrides its image reference, and the GHCR
/// default reference used when that variable is unset.
#[derive(Debug, Clone, Copy, PartialEq, Eq)]
pub struct Component {
    /// Short stable identifier (`control-plane` / `slack` / `telegram`). The key
    /// in a signed decision's digest set and the `--digest` CLI arg.
    pub name: &'static str,
    /// `metadata.name` of the `Deployment`.
    pub deployment: &'static str,
    /// `spec.template.spec.containers[].name` the image lives on.
    pub container: &'static str,
    /// Environment variable that, when set, overrides this component's full
    /// image reference (registry host + repository, no tag).
    pub image_env: &'static str,
    /// Default image reference (public GHCR) used when [`Component::image_env`]
    /// is unset. May name a host or be a bare `owner/repo` (defaults to
    /// `ghcr.io`).
    pub default_image: &'static str,
}

/// The three Deployments an upgrade rolls. Names/containers verified against
/// `manifests/base/*-deployment.yaml`; default images against `publish.yml`.
pub const COMPONENTS: [Component; 3] = [
    Component {
        name: "control-plane",
        deployment: "polychrome-control-plane",
        container: "polychrome",
        image_env: "POLYCHROME_UPGRADE_IMAGE_CONTROL_PLANE",
        default_image: "ghcr.io/officialunofficial/polychrome",
    },
    Component {
        name: "slack",
        deployment: "polychrome-slack",
        container: "polychrome-slack",
        image_env: "POLYCHROME_UPGRADE_IMAGE_SLACK",
        default_image: "ghcr.io/officialunofficial/polychrome-slack",
    },
    Component {
        name: "telegram",
        deployment: "polychrome-telegram",
        container: "polychrome-telegram",
        image_env: "POLYCHROME_UPGRADE_IMAGE_TELEGRAM",
        default_image: "ghcr.io/officialunofficial/polychrome-telegram",
    },
];

/// A resolved image reference — a registry host plus a repository, carrying no
/// tag. The tag is derived per upgrade from the target version.
#[derive(Debug, Clone, PartialEq, Eq)]
pub struct ImageRef {
    /// Registry host (e.g. `ghcr.io` or `us-east4-docker.pkg.dev`).
    pub registry: String,
    /// Repository path within the registry (e.g.
    /// `officialunofficial/polychrome` or
    /// `official-unofficial/docker/polychrome-control-plane`).
    pub repository: String,
}

/// Split a full image reference string into its registry host and repository.
///
/// Applies the standard Docker heuristic: the segment before the first `/` is
/// the registry host **iff** it contains a `.` or a `:` (a hostname or
/// `host:port`); otherwise there is no host and the whole string is a
/// repository under the default registry (`ghcr.io`).
///
/// # Examples
/// - `us-east4-docker.pkg.dev/official-unofficial/docker/polychrome-control-plane`
///   → registry `us-east4-docker.pkg.dev`, repo
///   `official-unofficial/docker/polychrome-control-plane`.
/// - `officialunofficial/polychrome` → registry `ghcr.io`, repo
///   `officialunofficial/polychrome`.
#[must_use]
pub fn parse_image_ref(full: &str) -> ImageRef {
    match full.split_once('/') {
        Some((host, rest)) if host.contains('.') || host.contains(':') => ImageRef {
            registry: host.to_owned(),
            repository: rest.to_owned(),
        },
        _ => ImageRef {
            registry: DEFAULT_REGISTRY.to_owned(),
            repository: full.to_owned(),
        },
    }
}

/// Resolve a component's image reference from the environment, falling back to
/// its public GHCR default.
///
/// The environment lookup is injected (rather than read from the process) so
/// this stays a pure function — unit-testable without touching global state.
/// Production callers pass `|k| std::env::var(k).ok()`.
#[must_use]
pub fn image_ref<F>(component: &Component, env_lookup: F) -> ImageRef
where
    F: Fn(&str) -> Option<String>,
{
    let raw = env_lookup(component.image_env).unwrap_or_else(|| component.default_image.to_owned());
    parse_image_ref(&raw)
}

/// Normalize a `--version` / release tag into the image tag published.
///
/// `publish.yml` tags release manifests `{{version}}` (no leading `v`), so a
/// release `v0.4.0` (or `--version v0.4.0`) maps to the image tag `0.4.0`. The
/// tag is validated as semver so a typo can't pin the cluster to a
/// non-existent / floating tag.
///
/// # Errors
/// Returns [`GhcrError::Version`] if the stripped tag is not valid semver.
pub fn image_tag_for_version(version: &str) -> Result<String, GhcrError> {
    let tag = version.trim().trim_start_matches('v');
    semver::Version::parse(tag).map_err(|_| GhcrError::Version(version.to_owned()))?;
    Ok(tag.to_owned())
}

/// Build the digest-pinned image reference from a resolved [`ImageRef`] and a
/// content digest (`{registry}/{repository}@{digest}`).
#[must_use]
pub fn pinned_reference(image: &ImageRef, digest: &str) -> String {
    format!("{}/{}@{}", image.registry, image.repository, digest)
}

/// How to authenticate a digest-resolution request against a registry host.
///
/// Selected purely from the host by [`auth_for`]; the effectful token fetch is
/// isolated behind each variant in [`resolve_digest`].
#[derive(Debug, Clone, Copy, PartialEq, Eq)]
pub enum RegistryAuth {
    /// The OCI anonymous pull-token flow (public GHCR): `GET /token?scope=…`.
    AnonymousToken,
    /// A GCP OAuth access token, for Google Artifact Registry (`*.pkg.dev`) and
    /// Container Registry (`*.gcr.io`).
    GcpMetadata,
}

/// Pick the registry-auth strategy for a host.
///
/// Google Artifact Registry (`*.pkg.dev`) and Container Registry (`gcr.io` /
/// `*.gcr.io`) require a GCP OAuth token; every other host (notably public
/// GHCR) uses the anonymous pull-token flow.
#[must_use]
pub fn auth_for(registry: &str) -> RegistryAuth {
    if registry.ends_with(".pkg.dev") || registry == "gcr.io" || registry.ends_with(".gcr.io") {
        RegistryAuth::GcpMetadata
    } else {
        RegistryAuth::AnonymousToken
    }
}

/// Build the shared HTTP client used for registry round-trips (bounded connect
/// and request timeouts, a `polychrome/<version>` user agent).
///
/// # Errors
/// Returns [`GhcrError::Http`] if the client can't be constructed.
pub fn http_client() -> Result<reqwest::Client, GhcrError> {
    Ok(reqwest::Client::builder()
        .timeout(REQUEST_TIMEOUT)
        .connect_timeout(CONNECT_TIMEOUT)
        .user_agent(concat!("polychrome/", env!("CARGO_PKG_VERSION")))
        .build()?)
}

/// Resolve the immutable manifest digest for `repository:tag` against `registry`.
///
/// The auth strategy is chosen from the host by [`auth_for`]: a public GHCR
/// repository authenticates with an anonymous bearer token from the registry
/// `token` endpoint, while a Google Artifact Registry / GCR host authenticates
/// with a GCP OAuth access token.
///
/// The `GET` reads the `Docker-Content-Digest` response header — the registry
/// computes it over the manifest bytes, so it is the canonical content address.
///
/// # Errors
/// Returns [`GhcrError`] if the bearer token can't be obtained, the manifest
/// request fails, or the response carries no digest header.
pub async fn resolve_digest(
    client: &reqwest::Client,
    registry: &str,
    repository: &str,
    tag: &str,
) -> Result<String, GhcrError> {
    let token = match auth_for(registry) {
        RegistryAuth::AnonymousToken => anonymous_pull_token(client, registry, repository).await?,
        RegistryAuth::GcpMetadata => gcp_access_token(client, registry).await?,
    };
    let url = format!("https://{registry}/v2/{repository}/manifests/{tag}");
    let resp = client
        .get(&url)
        .bearer_auth(&token)
        // Accept both the OCI image index and the Docker manifest-list media
        // types so multi-arch published images resolve to their index digest.
        .header(
            reqwest::header::ACCEPT,
            "application/vnd.oci.image.index.v1+json, \
             application/vnd.docker.distribution.manifest.list.v2+json, \
             application/vnd.oci.image.manifest.v1+json, \
             application/vnd.docker.distribution.manifest.v2+json",
        )
        .send()
        .await?
        .error_for_status()?;
    let digest = resp
        .headers()
        .get("docker-content-digest")
        .and_then(|v| v.to_str().ok())
        .ok_or_else(|| GhcrError::Malformed {
            repo: repository.to_owned(),
            what: "digest header",
        })?
        .to_owned();
    Ok(digest)
}

/// Fetch an anonymous pull token for a public repository (the OCI distribution
/// flow — GHCR).
async fn anonymous_pull_token(
    client: &reqwest::Client,
    registry: &str,
    repository: &str,
) -> Result<String, GhcrError> {
    let url =
        format!("https://{registry}/token?service={registry}&scope=repository:{repository}:pull");
    let body: serde_json::Value = client
        .get(&url)
        .send()
        .await?
        .error_for_status()?
        .json()
        .await?;
    // GHCR returns the bearer under `token`; some registries use `access_token`.
    body["token"]
        .as_str()
        .or_else(|| body["access_token"].as_str())
        .map(str::to_owned)
        .ok_or_else(|| GhcrError::Malformed {
            repo: repository.to_owned(),
            what: "pull token",
        })
}

/// Fetch a GCP OAuth access token for an Artifact Registry / GCR host.
///
/// In-cluster (with Workload Identity) this reads the token off the GCE
/// metadata server. For local use, point at Application Default Credentials
/// instead — export a token from `gcloud auth print-access-token` into the
/// environment ahead of the process, or run against a metadata proxy; the
/// resolver only needs a valid bearer for the registry host.
async fn gcp_access_token(client: &reqwest::Client, registry: &str) -> Result<String, GhcrError> {
    const METADATA_TOKEN_URL: &str = "http://metadata.google.internal/computeMetadata/v1/instance/service-accounts/default/token";
    let body: serde_json::Value = client
        .get(METADATA_TOKEN_URL)
        .header("Metadata-Flavor", "Google")
        .send()
        .await
        .map_err(|e| GhcrError::GcpToken {
            registry: registry.to_owned(),
            reason: format!("metadata request failed: {e}"),
        })?
        .error_for_status()
        .map_err(|e| GhcrError::GcpToken {
            registry: registry.to_owned(),
            reason: format!("metadata server returned an error: {e}"),
        })?
        .json()
        .await
        .map_err(|e| GhcrError::GcpToken {
            registry: registry.to_owned(),
            reason: format!("metadata response was not JSON: {e}"),
        })?;
    body["access_token"]
        .as_str()
        .map(str::to_owned)
        .ok_or_else(|| GhcrError::GcpToken {
            registry: registry.to_owned(),
            reason: "metadata response carried no `access_token`".to_owned(),
        })
}

#[cfg(test)]
mod tests {
    #![allow(clippy::pedantic, clippy::nursery)]

    use super::*;

    fn component(name: &str) -> &'static Component {
        COMPONENTS.iter().find(|c| c.name == name).unwrap()
    }

    #[test]
    fn image_tag_strips_v_and_validates() {
        assert_eq!(image_tag_for_version("v0.4.0").unwrap(), "0.4.0");
        assert_eq!(image_tag_for_version("0.4.0").unwrap(), "0.4.0");
        assert_eq!(image_tag_for_version("  v1.2.3 ").unwrap(), "1.2.3");
    }

    #[test]
    fn image_tag_rejects_non_semver() {
        assert!(image_tag_for_version("latest").is_err());
        assert!(image_tag_for_version("1.2").is_err());
        assert!(image_tag_for_version("v").is_err());
    }

    #[test]
    fn parse_splits_gar_host_from_repository() {
        let r = parse_image_ref(
            "us-east4-docker.pkg.dev/official-unofficial/docker/polychrome-control-plane",
        );
        assert_eq!(r.registry, "us-east4-docker.pkg.dev");
        assert_eq!(
            r.repository,
            "official-unofficial/docker/polychrome-control-plane"
        );
    }

    #[test]
    fn parse_defaults_hostless_ref_to_ghcr() {
        let r = parse_image_ref("officialunofficial/polychrome");
        assert_eq!(r.registry, "ghcr.io");
        assert_eq!(r.repository, "officialunofficial/polychrome");
    }

    #[test]
    fn parse_treats_host_port_as_registry() {
        let r = parse_image_ref("localhost:5000/team/app");
        assert_eq!(r.registry, "localhost:5000");
        assert_eq!(r.repository, "team/app");
    }

    #[test]
    fn image_ref_defaults_to_ghcr_with_empty_env() {
        let cp = image_ref(component("control-plane"), |_| None);
        assert_eq!(cp.registry, "ghcr.io");
        assert_eq!(cp.repository, "officialunofficial/polychrome");

        let slack = image_ref(component("slack"), |_| None);
        assert_eq!(
            pinned_reference(&slack, "sha256:x"),
            "ghcr.io/officialunofficial/polychrome-slack@sha256:x"
        );
    }

    #[test]
    fn image_ref_honors_gar_override() {
        let env = |k: &str| match k {
            "POLYCHROME_UPGRADE_IMAGE_CONTROL_PLANE" => Some(
                "us-east4-docker.pkg.dev/official-unofficial/docker/polychrome-control-plane"
                    .to_owned(),
            ),
            _ => None,
        };
        let cp = image_ref(component("control-plane"), env);
        assert_eq!(cp.registry, "us-east4-docker.pkg.dev");
        assert_eq!(
            cp.repository,
            "official-unofficial/docker/polychrome-control-plane"
        );
        // An unset component still falls back to its GHCR default.
        let slack = image_ref(component("slack"), env);
        assert_eq!(slack.registry, "ghcr.io");
    }

    #[test]
    fn pinned_reference_format_for_ghcr_and_gar() {
        let ghcr = ImageRef {
            registry: "ghcr.io".to_owned(),
            repository: "officialunofficial/polychrome".to_owned(),
        };
        assert_eq!(
            pinned_reference(&ghcr, "sha256:abc"),
            "ghcr.io/officialunofficial/polychrome@sha256:abc"
        );
        let gar = ImageRef {
            registry: "us-east4-docker.pkg.dev".to_owned(),
            repository: "official-unofficial/docker/polychrome-control-plane".to_owned(),
        };
        assert_eq!(
            pinned_reference(&gar, "sha256:def"),
            "us-east4-docker.pkg.dev/official-unofficial/docker/polychrome-control-plane@sha256:def"
        );
    }

    #[test]
    fn auth_for_selects_by_host() {
        assert_eq!(auth_for("ghcr.io"), RegistryAuth::AnonymousToken);
        assert_eq!(
            auth_for("us-east4-docker.pkg.dev"),
            RegistryAuth::GcpMetadata
        );
        assert_eq!(auth_for("us.gcr.io"), RegistryAuth::GcpMetadata);
        assert_eq!(auth_for("gcr.io"), RegistryAuth::GcpMetadata);
        assert_eq!(auth_for("docker.io"), RegistryAuth::AnonymousToken);
    }

    #[test]
    fn components_carry_stable_names() {
        let names: Vec<&str> = COMPONENTS.iter().map(|c| c.name).collect();
        assert_eq!(names, vec!["control-plane", "slack", "telegram"]);
    }
}