Add github.event as a source

ql/lib/codeql/actions/dataflow/FlowSources.qll

@@ -22,6 +22,13 @@ abstract class RemoteFlowSource extends SourceNode {
   override string getThreatModel() { result = "remote" }
 }
 
+bindingset[context]
+private predicate isExternalUserControlled(string context) {
+  exists(string reg | reg = "github\\.event" |
+    Utils::normalizeExpr(context).regexpMatch(Utils::wrapRegexp(reg))
+  )
+}
+
 bindingset[context]
 private predicate isExternalUserControlledIssue(string context) {
   exists(string reg | reg = ["github\\.event\\.issue\\.title", "github\\.event\\.issue\\.body"] |
@@ -123,6 +130,7 @@ private predicate isExternalUserControlledWorkflowRun(string context) {
 private class EventSource extends RemoteFlowSource {
   EventSource() {
     exists(Expression e, string context | this.asExpr() = e and context = e.getExpression() |
+      isExternalUserControlled(context) or
       isExternalUserControlledIssue(context) or
       isExternalUserControlledPullRequest(context) or
       isExternalUserControlledReview(context) or

ql/test/query-tests/Security/CWE-094/.github/workflows/simple3.yml

@@ -0,0 +1,23 @@
+on:
+  workflow_run:
+    workflows:
+      - 'prev'
+    types:
+      - completed
+
+permissions:
+  actions: read
+  checks: read
+  contents: read
+
+jobs:
+  echo_trigger:
+    name: Report changes
+    runs-on: ubuntu-latest
+    steps:
+      - name: Echo trigger
+        run: |
+          echo "head branch: ${{ github.event.workflow_run.head_branch }}"
+          cat << EOF
+          ${{ toJSON(github.event) }}
+          EOF

ql/test/query-tests/Security/CWE-094/CodeInjection.expected

@@ -200,6 +200,8 @@ nodes
 | .github/workflows/simple2.yml:18:9:26:6 | Uses Step: step [value] | semmle.label | Uses Step: step [value] |
 | .github/workflows/simple2.yml:22:20:22:64 | steps.source.outputs.all_changed_files | semmle.label | steps.source.outputs.all_changed_files |
 | .github/workflows/simple2.yml:29:24:29:54 | steps.step.outputs.value | semmle.label | steps.step.outputs.value |
+| .github/workflows/simple3.yml:23:31:23:74 | github.event.workflow_run.head_branch | semmle.label | github.event.workflow_run.head_branch |
+| .github/workflows/simple3.yml:25:11:25:37 | toJSON(github.event) | semmle.label | toJSON(github.event) |
 | .github/workflows/test1.yml:22:38:22:75 | github.event.pull_request.title | semmle.label | github.event.pull_request.title |
 | .github/workflows/test1.yml:22:38:22:75 | github.event.pull_request.title | semmle.label | github.event.pull_request.title |
 | .github/workflows/test1.yml:25:20:25:39 | env.ISSUE_KEY | semmle.label | env.ISSUE_KEY |

ql/test/query-tests/Security/CWE-094/PrivilegedCodeInjection.expected

@@ -200,6 +200,8 @@ nodes
 | .github/workflows/simple2.yml:18:9:26:6 | Uses Step: step [value] | semmle.label | Uses Step: step [value] |
 | .github/workflows/simple2.yml:22:20:22:64 | steps.source.outputs.all_changed_files | semmle.label | steps.source.outputs.all_changed_files |
 | .github/workflows/simple2.yml:29:24:29:54 | steps.step.outputs.value | semmle.label | steps.step.outputs.value |
+| .github/workflows/simple3.yml:23:31:23:74 | github.event.workflow_run.head_branch | semmle.label | github.event.workflow_run.head_branch |
+| .github/workflows/simple3.yml:25:11:25:37 | toJSON(github.event) | semmle.label | toJSON(github.event) |
 | .github/workflows/test1.yml:22:38:22:75 | github.event.pull_request.title | semmle.label | github.event.pull_request.title |
 | .github/workflows/test1.yml:22:38:22:75 | github.event.pull_request.title | semmle.label | github.event.pull_request.title |
 | .github/workflows/test1.yml:25:20:25:39 | env.ISSUE_KEY | semmle.label | env.ISSUE_KEY |
@@ -307,6 +309,8 @@ subpaths
 | .github/workflows/self_needs.yml:20:15:20:51 | needs.test1.outputs.job_output | .github/workflows/self_needs.yml:16:20:16:64 | github.event['head_commit']['message'] | .github/workflows/self_needs.yml:20:15:20:51 | needs.test1.outputs.job_output | Potential privileged code injection in $@, which may be controlled by an external user. | .github/workflows/self_needs.yml:20:15:20:51 | needs.test1.outputs.job_output | ${{ needs.test1.outputs.job_output }} |
 | .github/workflows/simple1.yml:16:18:16:49 | steps.summary.outputs.value | .github/workflows/simple1.yml:11:20:11:58 | github.event.head_commit.message | .github/workflows/simple1.yml:16:18:16:49 | steps.summary.outputs.value | Potential privileged code injection in $@, which may be controlled by an external user. | .github/workflows/simple1.yml:16:18:16:49 | steps.summary.outputs.value | ${{steps.summary.outputs.value}} |
 | .github/workflows/simple2.yml:29:24:29:54 | steps.step.outputs.value | .github/workflows/simple2.yml:14:9:18:6 | Uses Step: source | .github/workflows/simple2.yml:29:24:29:54 | steps.step.outputs.value | Potential privileged code injection in $@, which may be controlled by an external user. | .github/workflows/simple2.yml:29:24:29:54 | steps.step.outputs.value | ${{ steps.step.outputs.value }} |
+| .github/workflows/simple3.yml:23:31:23:74 | github.event.workflow_run.head_branch | .github/workflows/simple3.yml:23:31:23:74 | github.event.workflow_run.head_branch | .github/workflows/simple3.yml:23:31:23:74 | github.event.workflow_run.head_branch | Potential privileged code injection in $@, which may be controlled by an external user. | .github/workflows/simple3.yml:23:31:23:74 | github.event.workflow_run.head_branch | ${{ github.event.workflow_run.head_branch }} |
+| .github/workflows/simple3.yml:25:11:25:37 | toJSON(github.event) | .github/workflows/simple3.yml:25:11:25:37 | toJSON(github.event) | .github/workflows/simple3.yml:25:11:25:37 | toJSON(github.event) | Potential privileged code injection in $@, which may be controlled by an external user. | .github/workflows/simple3.yml:25:11:25:37 | toJSON(github.event) | ${{ toJSON(github.event) }} |
 | .github/workflows/test1.yml:22:38:22:75 | github.event.pull_request.title | .github/workflows/test1.yml:22:38:22:75 | github.event.pull_request.title | .github/workflows/test1.yml:22:38:22:75 | github.event.pull_request.title | Potential privileged code injection in $@, which may be controlled by an external user. | .github/workflows/test1.yml:22:38:22:75 | github.event.pull_request.title | ${{ github.event.pull_request.title }} |
 | .github/workflows/test1.yml:25:20:25:39 | env.ISSUE_KEY | .github/workflows/test1.yml:22:38:22:75 | github.event.pull_request.title | .github/workflows/test1.yml:25:20:25:39 | env.ISSUE_KEY | Potential privileged code injection in $@, which may be controlled by an external user. | .github/workflows/test1.yml:25:20:25:39 | env.ISSUE_KEY | ${{ env.ISSUE_KEY }} |
 | .github/workflows/test.yml:49:20:49:56 | needs.job1.outputs['job_output'] | .github/workflows/test.yml:15:20:15:64 | github.event['head_commit']['message'] | .github/workflows/test.yml:49:20:49:56 | needs.job1.outputs['job_output'] | Potential privileged code injection in $@, which may be controlled by an external user. | .github/workflows/test.yml:49:20:49:56 | needs.job1.outputs['job_output'] | ${{needs.job1.outputs['job_output']}} |