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use crate::{
audit::AuditError,
finding::{
Confidence, Finding, Persona, Severity,
location::{Locatable as _, SymbolicLocation},
},
models::{AsDocument, action::DockerAction, workflow::matrix::Matrix},
state::AuditState,
};
use github_actions_expressions::{Expr, SpannedExpr, literal::Literal};
use github_actions_models::workflow::job::Container;
use github_actions_models::{
action::DockerActionUses,
common::{DockerUses, expr::LoE},
};
use subfeature::Subfeature;
use super::{Audit, AuditLoadError, audit_meta};
pub(crate) struct UnpinnedImages;
/// A single candidate image reference, collected from a job or action and
/// expanded through matrix references where possible.
struct ImageCandidate<'doc> {
annotation: &'static str,
confidence: Confidence,
persona: Persona,
location: SymbolicLocation<'doc>,
related: Vec<SymbolicLocation<'doc>>,
}
impl<'doc> ImageCandidate<'doc> {
/// A candidate for a concrete image reference that we can analyze precisely.
///
/// Returns `None` if the image is empty (i.e. no container) or is
/// acceptably pinned by a SHA256 hash.
fn concrete(
image: &DockerUses,
location: SymbolicLocation<'doc>,
related: Vec<SymbolicLocation<'doc>>,
) -> Option<Self> {
if image.image().is_empty() {
return None;
}
let (annotation, persona) = match (image.tag(), image.hash()) {
// Pinned by hash: nothing to report.
(_, Some(_)) => return None,
(Some("latest"), None) => ("container image is pinned to latest", Persona::Regular),
(Some(_), None) => (
"container image is not pinned to a SHA256 hash",
Persona::Pedantic,
),
(None, None) => ("container image is unpinned", Persona::Regular),
};
Some(Self {
annotation,
confidence: Confidence::High,
persona,
location,
related,
})
}
/// A candidate for an image reference that we can't analyze statically,
/// e.g. one derived from a non-`matrix` context or a dynamic matrix
/// expansion.
fn opaque(location: SymbolicLocation<'doc>, related: Vec<SymbolicLocation<'doc>>) -> Self {
Self {
annotation: "container image may be unpinned",
confidence: Confidence::Low,
persona: Persona::Regular,
location,
related,
}
}
}
/// Collect all candidate image references from a single image expression,
/// expanding through the matrix where possible.
fn collect_candidates<'doc>(
image: &'doc LoE<DockerUses>,
location: &SymbolicLocation<'doc>,
matrix: Option<&Matrix<'doc>>,
) -> Vec<ImageCandidate<'doc>> {
match image {
// A literal image reference, e.g. `image: foo:1.2.3`.
LoE::Literal(image) => ImageCandidate::concrete(image, location.clone(), vec![])
.into_iter()
.collect(),
// An expression, e.g. `image: ${{ matrix.image }}`. We expand it into
// its possible leaf values and analyze each.
LoE::Expr(expr) => {
let Ok(parsed) = Expr::parse(expr.as_bare()) else {
// We can't even parse the expression, so we can't say anything
// precise about it.
return vec![ImageCandidate::opaque(location.clone(), vec![])];
};
let leaves = parsed.leaf_expressions();
// When the entire expression is a single leaf (e.g. `${{ matrix.image }}`),
// it spans the whole feature and we annotate it directly. Otherwise
// each leaf gets its own subfeature location within the expression.
let single_leaf = leaves.len() == 1;
leaves
.into_iter()
.flat_map(|leaf| {
let leaf_location = if single_leaf {
location.clone()
} else {
location
.clone()
.subfeature(Subfeature::new(0, subfeature::Fragment::from(leaf)))
};
candidates_for_leaf(leaf, leaf_location, matrix)
})
.collect()
}
}
}
/// Collect candidate image references from a single leaf expression.
fn candidates_for_leaf<'doc>(
leaf: &SpannedExpr<'_>,
location: SymbolicLocation<'doc>,
matrix: Option<&Matrix<'doc>>,
) -> Vec<ImageCandidate<'doc>> {
match &leaf.inner {
// A string literal can be analyzed precisely as an image reference.
Expr::Literal(Literal::String(image)) => {
if image.is_empty() {
// Empty string literals contribute no image reference.
vec![]
} else {
ImageCandidate::concrete(&DockerUses::parse(image.as_ref()), location, vec![])
.into_iter()
.collect()
}
}
// A `matrix` context expands into its concrete values; analyze each.
Expr::Context(context) if context.child_of("matrix") => {
let Some(matrix) = matrix else {
tracing::warn!(
"image references {raw} but job has no matrix",
raw = leaf.origin.raw
);
return vec![];
};
matrix
.expansions()
.iter()
.filter(|expansion| context.matches(expansion.path.as_str()))
.flat_map(|expansion| {
if expansion.is_static() {
ImageCandidate::concrete(
&DockerUses::parse(&expansion.value),
location.clone(),
vec![
matrix.location().key_only(),
expansion.location().annotated(format!(
"this expansion of {path}",
path = expansion.path
)),
],
)
.into_iter()
.collect()
} else {
// The expansion itself contains an expression, so we
// can't analyze it statically.
vec![ImageCandidate::opaque(
location.clone(),
vec![expansion.location()],
)]
}
})
.collect()
}
// Any other leaf (non-`matrix` context, function call, etc.) can't be
// analyzed statically.
_ => vec![ImageCandidate::opaque(location, vec![])],
}
}
impl UnpinnedImages {
/// Collect every candidate image reference from a list of image
/// expressions (expanding through the matrix where possible) and emit
/// findings for any that are unpinned.
fn classify_images<'a, 'doc>(
&self,
image_refs: Vec<(&'doc LoE<DockerUses>, SymbolicLocation<'doc>)>,
matrix: Option<Matrix<'doc>>,
document: &'a impl AsDocument<'a, 'doc>,
) -> Result<Vec<Finding<'doc>>, AuditError> {
let mut findings = vec![];
for (image, location) in image_refs {
for candidate in collect_candidates(image, &location, matrix.as_ref()) {
let mut finding = Self::finding()
.severity(Severity::High)
.confidence(candidate.confidence)
.persona(candidate.persona)
.add_location(candidate.location.annotated(candidate.annotation));
for related in candidate.related {
finding = finding.add_location(related);
}
findings.push(finding.build(document)?);
}
}
Ok(findings)
}
}
audit_meta!(
UnpinnedImages,
"unpinned-images",
"unpinned image references"
);
#[async_trait::async_trait]
impl Audit for UnpinnedImages {
fn new(_state: &AuditState) -> Result<Self, AuditLoadError> {
Ok(Self)
}
async fn audit_docker_action<'doc>(
&self,
docker: &DockerAction<'doc>,
_config: &crate::config::Config,
) -> anyhow::Result<Vec<Finding<'doc>>, AuditError> {
// Nothing to do if the action references its own intrinsic 'Dockerfile'
// rather than an external image.
let DockerActionUses::Image(image) = &docker.image else {
return Ok(vec![]);
};
self.classify_images(
vec![(image, docker.location().with_keys(["image".into()]))],
None,
docker,
)
}
async fn audit_normal_job<'doc>(
&self,
job: &super::NormalJob<'doc>,
_config: &crate::config::Config,
) -> anyhow::Result<Vec<Finding<'doc>>, AuditError> {
let mut image_refs: Vec<(&'doc LoE<DockerUses>, SymbolicLocation<'doc>)> = vec![];
match &job.container {
Some(Container::Name(image)) => {
image_refs.push((
image,
job.location().primary().with_keys(["container".into()]),
));
}
Some(Container::Container { image, .. }) => {
image_refs.push((
image,
job.location()
.primary()
.with_keys(["container".into(), "image".into()]),
));
}
None => {}
}
for (service, config) in job.services.iter() {
if let Container::Container { image, .. } = &config {
image_refs.push((
image,
job.location().primary().with_keys([
"services".into(),
service.as_str().into(),
"image".into(),
]),
));
}
}
self.classify_images(image_refs, job.matrix(), job)
}
}