Merge pull request 'harden(provisioner): denylist SCM-write tokens from tenant workspace env (forensic #145)' (#1277) from harden/provisioner-scm-token-denylist into staging

workspace-server/internal/provisioner/cp_provisioner.go

@@ -178,12 +178,21 @@ func (p *CPProvisioner) Start(ctx context.Context, cfg WorkspaceConfig) (string,
 	// /admin/liveness and other admin-gated platform endpoints (core#831).
 	// p.adminToken is read from os.Getenv("ADMIN_TOKEN") at provisioner creation;
 	// it is also used for CP→platform HTTP auth but those are separate concerns.
-	env := cfg.EnvVars
-	if p.adminToken != "" {
-		env = make(map[string]string, len(cfg.EnvVars)+1)
-		for k, v := range cfg.EnvVars {
-			env[k] = v
+	//
+	// Forensic #145 hardening: tenant workspaces run on EC2 via this path, so
+	// the SCM-write-token denylist (see buildContainerEnv) is enforced here
+	// too. Always build a filtered copy — never pass cfg.EnvVars through
+	// verbatim — so a latent persona-merged GITEA_TOKEN can't reach the
+	// tenant container regardless of whether ADMIN_TOKEN is set.
+	env := make(map[string]string, len(cfg.EnvVars)+1)
+	for k, v := range cfg.EnvVars {
+		if isSCMWriteTokenKey(k) {
+			log.Printf("CPProvisioner.Start: dropped SCM-write credential %q from tenant workspace env (forensic #145 guard)", k)
+			continue
 		}
+		env[k] = v
+	}
+	if p.adminToken != "" {
 		env["ADMIN_TOKEN"] = p.adminToken
 	}
 	// Collect template files and generated configs, with OFFSEC-010 guards:
@@ -343,6 +352,7 @@ func collectCPConfigFiles(cfg WorkspaceConfig) (map[string]string, error) {
 	}
 	return files, nil
 }
+
 // Stop terminates the workspace's EC2 instance via the control plane.
 //
 // Looks up the actual EC2 instance_id from the workspaces table before
@@ -497,7 +507,9 @@ func (p *CPProvisioner) IsRunning(ctx context.Context, workspaceID string) (bool
 		// Don't leak the body — upstream errors may echo headers.
 		return true, fmt.Errorf("cp provisioner: status: unexpected %d", resp.StatusCode)
 	}
-	var result struct{ State string `json:"state"` }
+	var result struct {
+		State string `json:"state"`
+	}
 	// Cap body read at 64 KiB for parity with Start — a misconfigured
 	// or compromised CP streaming a huge body could otherwise exhaust
 	// memory in this hot path (called reactively per-request from

workspace-server/internal/provisioner/provisioner.go

@@ -591,6 +591,28 @@ func ValidateWorkspaceAccess(access, workspacePath string) error {
 	}
 }
 
+// scmWriteTokenKeys is the explicit denylist of environment variable names
+// that carry a Git SCM *write* credential (push / merge / approve). These
+// must never reach a tenant workspace container — see the forensic #145
+// rationale in buildContainerEnv. Kept as an exact-match set rather than a
+// substring/prefix heuristic so the guard is auditable and can't silently
+// over-strip a legitimately-named var.
+var scmWriteTokenKeys = map[string]struct{}{
+	"GITEA_TOKEN":     {},
+	"GITHUB_TOKEN":    {},
+	"GH_TOKEN":        {}, // gh CLI honours GH_TOKEN as a GITHUB_TOKEN alias
+	"GITLAB_TOKEN":    {},
+	"GL_TOKEN":        {}, // glab CLI alias
+	"BITBUCKET_TOKEN": {},
+}
+
+// isSCMWriteTokenKey reports whether an env var name is a known Git SCM
+// write credential that must be stripped from tenant workspace env.
+func isSCMWriteTokenKey(key string) bool {
+	_, ok := scmWriteTokenKeys[key]
+	return ok
+}
+
 // buildContainerEnv assembles the initial environment variables injected
 // into every workspace container.
 //
@@ -627,6 +649,21 @@ func buildContainerEnv(cfg WorkspaceConfig) []string {
 		env = append(env, fmt.Sprintf("AWARENESS_URL=%s", cfg.AwarenessURL))
 	}
 	for k, v := range cfg.EnvVars {
+		// Forensic #145 hardening: tenant workspace containers run
+		// agent-controlled code and must NEVER receive a Git SCM *write*
+		// credential. Without merge/approve creds in-container the
+		// two-eyes review gate is structurally self-bypass-proof — an
+		// agent that forges an approval has no token to act on it. A
+		// latent path exists (loadPersonaEnvFile merges a per-role
+		// persona `GITEA_TOKEN` into cfg.EnvVars when MOLECULE_PERSONA_ROOT
+		// is set on a tenant host); it is inert today (persona dirs are
+		// operator-host-only) but unguarded. Strip SCM-write tokens here
+		// by construction so the invariant holds regardless of whether
+		// that path ever becomes reachable.
+		if isSCMWriteTokenKey(k) {
+			log.Printf("buildContainerEnv: dropped SCM-write credential %q from workspace env (forensic #145 guard)", k)
+			continue
+		}
 		env = append(env, fmt.Sprintf("%s=%s", k, v))
 	}
 	// Inject ADMIN_TOKEN from the platform server's environment so workspace

workspace-server/internal/provisioner/provisioner_test.go

@@ -636,10 +636,15 @@ func TestBuildContainerEnv_AwarenessOnlyWhenBothSet(t *testing.T) {
 }
 
 func TestBuildContainerEnv_CustomEnvVarsAppended(t *testing.T) {
+	// NOTE: this test previously asserted GITHUB_TOKEN passed through
+	// verbatim. That assertion encoded the forensic #145 latent leak as
+	// expected behavior. Post-guard, ordinary custom env still flows but
+	// SCM-write credentials are stripped — see
+	// TestBuildContainerEnv_StripsSCMWriteTokens for the negative assertion.
 	cfg := WorkspaceConfig{
 		WorkspaceID: "ws-x",
 		PlatformURL: "http://localhost:8080",
-		EnvVars:     map[string]string{"CUSTOM": "value", "GITHUB_TOKEN": "fake-token-for-test"},
+		EnvVars:     map[string]string{"CUSTOM": "value", "ANTHROPIC_API_KEY": "sk-not-an-scm-token"},
 	}
 	env := buildContainerEnv(cfg)
 	seen := map[string]string{}
@@ -652,8 +657,8 @@ func TestBuildContainerEnv_CustomEnvVarsAppended(t *testing.T) {
 	if seen["CUSTOM"] != "value" {
 		t.Errorf("CUSTOM env missing, got env=%v", env)
 	}
-	if seen["GITHUB_TOKEN"] != "fake-token-for-test" {
-		t.Errorf("GITHUB_TOKEN env missing, got env=%v", env)
+	if seen["ANTHROPIC_API_KEY"] != "sk-not-an-scm-token" {
+		t.Errorf("non-SCM custom env must still pass through, got env=%v", env)
 	}
 	// Built-in defaults still present
 	if seen["MOLECULE_URL"] == "" {
@@ -661,6 +666,129 @@ func TestBuildContainerEnv_CustomEnvVarsAppended(t *testing.T) {
 	}
 }
 
+// ---------- forensic #145: SCM-write-token denylist guard ----------
+
+// TestBuildContainerEnv_StripsSCMWriteTokens is the core negative
+// assertion: a tenant workspace env constructed via buildContainerEnv MUST
+// NOT contain any Git SCM *write* credential, regardless of how it got into
+// cfg.EnvVars. This proves the two-eyes review gate stays structurally
+// self-bypass-proof — an agent in-container has no merge/approve token to
+// act on a forged approval. See forensic #145.
+//
+// This test FAILS on the pre-guard code (where buildContainerEnv passed
+// cfg.EnvVars through verbatim) and PASSES once the denylist filter is in
+// place — i.e. the guard is proven by construction, not by environment
+// accident.
+func TestBuildContainerEnv_StripsSCMWriteTokens(t *testing.T) {
+	scmTokens := []string{
+		"GITEA_TOKEN", "GITHUB_TOKEN", "GH_TOKEN",
+		"GITLAB_TOKEN", "GL_TOKEN", "BITBUCKET_TOKEN",
+	}
+
+	t.Run("normal path — SCM tokens explicitly set in EnvVars", func(t *testing.T) {
+		envVars := map[string]string{"CUSTOM": "ok", "ANTHROPIC_API_KEY": "sk-keep"}
+		for _, k := range scmTokens {
+			envVars[k] = "leaked-write-credential-" + k
+		}
+		cfg := WorkspaceConfig{
+			WorkspaceID: "ws-tenant",
+			PlatformURL: "http://localhost:8080",
+			Tier:        2,
+			EnvVars:     envVars,
+		}
+		assertNoSCMWriteToken(t, buildContainerEnv(cfg), scmTokens)
+
+		// Sanity: non-SCM custom env is NOT collateral-damaged by the filter.
+		if !envContains(buildContainerEnv(cfg), "CUSTOM=ok") {
+			t.Errorf("filter must not strip non-SCM custom env")
+		}
+		if !envContains(buildContainerEnv(cfg), "ANTHROPIC_API_KEY=sk-keep") {
+			t.Errorf("filter must not strip non-SCM API keys")
+		}
+	})
+
+	t.Run("persona-file path — simulates loadPersonaEnvFile merge", func(t *testing.T) {
+		// The latent path: handlers.loadPersonaEnvFile() merges a per-role
+		// persona env file (carrying GITEA_USER, GITEA_TOKEN, …) into the
+		// workspace env map when MOLECULE_PERSONA_ROOT is set on a tenant
+		// host. We can't invoke that cross-package helper here, but its
+		// observable effect is exactly "a GITEA_TOKEN appears in
+		// cfg.EnvVars". Constructing that condition directly proves the
+		// guard holds even if the latent path becomes reachable.
+		cfg := WorkspaceConfig{
+			WorkspaceID: "ws-tenant",
+			PlatformURL: "http://localhost:8080",
+			Tier:        2,
+			EnvVars: map[string]string{
+				// Persona identity fields that are SAFE to keep (read-only
+				// identity, not a write credential):
+				"GITEA_USER":       "backend-engineer",
+				"GITEA_USER_EMAIL": "backend-engineer@agents.moleculesai.app",
+				// The credential that must be stripped:
+				"GITEA_TOKEN":        "persona-merged-write-pat",
+				"GITEA_TOKEN_SCOPES": "write:repository",
+			},
+		}
+		got := buildContainerEnv(cfg)
+		assertNoSCMWriteToken(t, got, scmTokens)
+		// Non-credential persona identity may still flow through — only the
+		// write token is the denied surface.
+		if !envContains(got, "GITEA_USER=backend-engineer") {
+			t.Errorf("non-credential persona identity (GITEA_USER) should not be stripped")
+		}
+	})
+}
+
+// TestCPProvisionerEnv_StripsSCMWriteTokens covers the tenant-EC2 path:
+// CPProvisioner.Start builds the env map the control plane forwards to the
+// EC2 workspace container. The same forensic #145 denylist must hold there.
+func TestCPProvisionerEnv_StripsSCMWriteTokens(t *testing.T) {
+	// isSCMWriteTokenKey is the single source of truth shared by both
+	// buildContainerEnv (local Docker) and CPProvisioner.Start (tenant EC2).
+	// Assert it classifies every known SCM-write var as denied and leaves
+	// ordinary / read-only-identity vars alone.
+	for _, k := range []string{
+		"GITEA_TOKEN", "GITHUB_TOKEN", "GH_TOKEN",
+		"GITLAB_TOKEN", "GL_TOKEN", "BITBUCKET_TOKEN",
+	} {
+		if !isSCMWriteTokenKey(k) {
+			t.Errorf("isSCMWriteTokenKey(%q) = false, want true (SCM-write credential must be denied)", k)
+		}
+	}
+	for _, k := range []string{
+		"GITEA_USER", "GITEA_USER_EMAIL", "ANTHROPIC_API_KEY",
+		"CUSTOM", "PLATFORM_URL", "ADMIN_TOKEN", "",
+	} {
+		if isSCMWriteTokenKey(k) {
+			t.Errorf("isSCMWriteTokenKey(%q) = true, want false (must not over-strip non-SCM env)", k)
+		}
+	}
+}
+
+func assertNoSCMWriteToken(t *testing.T, env []string, scmTokens []string) {
+	t.Helper()
+	for _, e := range env {
+		key := e
+		if i := strings.IndexByte(e, '='); i >= 0 {
+			key = e[:i]
+		}
+		for _, banned := range scmTokens {
+			if key == banned {
+				t.Errorf("SCM-write credential %q leaked into workspace env (forensic #145 invariant violated): %q", banned, e)
+			}
+		}
+	}
+}
+
+func envContains(env []string, want string) bool {
+	for _, e := range env {
+		if e == want {
+			return true
+		}
+	}
+	return false
+}
+
 // ---------- buildWorkspaceMount — #65 workspace_access ----------
 
 func TestBuildWorkspaceMount_SelectionMatrix(t *testing.T) {