harden rpm virtual redirects, fail closed, keep data files resolvable

- reject absolute and dot-segment member paths, escape the target, keep the query
- return 502 when any member's repodata can't be fetched
- serve recently merged data files by hash for 5m after repomd changes
- fold xml:base under a member upstream into the virtual href

internal/virtual/engine_test.go

@@ -0,0 +1,89 @@
+package virtual
+
+import (
+	"context"
+	"errors"
+	"regexp"
+	"testing"
+
+	"git.unkin.net/unkin/artifactapi/pkg/models"
+)
+
+func fakeEngine(members map[string]*RPMMember) *Engine {
+	return &Engine{
+		getRemote: func(_ context.Context, name string) (*models.Remote, error) {
+			return &models.Remote{Name: name, RepoType: models.RepoTypeRemote}, nil
+		},
+		rpmMember: func(_ context.Context, name string) (*RPMMember, error) {
+			if m := members[name]; m != nil {
+				return m, nil
+			}
+			return nil, errors.New("upstream down")
+		},
+	}
+}
+
+func rpmVirt(members ...string) models.Virtual {
+	return models.Virtual{Name: "v", PackageType: models.PackageRPM, Members: members}
+}
+
+func TestFetchRPMFailsClosed(t *testing.T) {
+	e := fakeEngine(map[string]*RPMMember{
+		"a": {RemoteName: "a", Data: map[string][]byte{"primary": primaryXML(primaryPkgXML("foo", "1", "aaa", "foo.rpm"))}},
+	})
+	_, _, err := e.Fetch(context.Background(), rpmVirt("a", "b"), "repodata/repomd.xml", "")
+	if err == nil || errors.Is(err, ErrNotFound) {
+		t.Fatalf("want upstream error with a member down, got %v", err)
+	}
+}
+
+func TestFetchRPMDataSurvivesMemberChange(t *testing.T) {
+	m := &RPMMember{RemoteName: "a", Data: map[string][]byte{"primary": primaryXML(primaryPkgXML("foo", "1", "aaa", "foo.rpm"))}}
+	e := fakeEngine(map[string]*RPMMember{"a": m})
+	virt := rpmVirt("a")
+
+	repomd, _, err := e.Fetch(context.Background(), virt, "repodata/repomd.xml", "")
+	if err != nil {
+		t.Fatal(err)
+	}
+	m.Data = map[string][]byte{"primary": primaryXML(primaryPkgXML("foo", "2", "bbb", "foo2.rpm"))}
+
+	href := regexp.MustCompile(`repodata/[0-9a-f]+-primary\.xml\.gz`).Find(repomd)
+	body, _, err := e.Fetch(context.Background(), virt, string(href), "")
+	if err != nil {
+		t.Fatalf("data from previous repomd must stay resolvable: %v", err)
+	}
+	if got := string(gunzip(t, body)); !regexp.MustCompile(`ver="1"`).MatchString(got) {
+		t.Fatalf("served wrong primary:\n%s", got)
+	}
+
+	newMD, _, err := e.Fetch(context.Background(), virt, "repodata/repomd.xml", "")
+	if err != nil || string(newMD) == string(repomd) {
+		t.Fatalf("repomd should reflect the member change (err %v)", err)
+	}
+}
+
+func TestMemberRedirect(t *testing.T) {
+	e := fakeEngine(nil)
+	virt := rpmVirt("gh", "other")
+	for _, tc := range []struct {
+		path, query, want string
+		ok                bool
+		err               error
+	}{
+		{path: "gh/o/r/releases/download/v1/c++-1.rpm", query: "x=1", ok: true,
+			want: "http://h/api/v1/remote/gh/o/r/releases/download/v1/c++-1.rpm?x=1"},
+		{path: "gh/a%20b/c%3Fd.rpm", ok: true, want: "http://h/api/v1/remote/gh/a%20b/c%3Fd.rpm"},
+		{path: "gh/../../remote/other/x", err: ErrBadPath},
+		{path: "gh/%2e%2e/%2e%2e/remote/other/x", err: ErrBadPath},
+		{path: "gh/a/./b", err: ErrBadPath},
+		{path: "gh//etc/passwd", err: ErrBadPath},
+		{path: "repodata/repomd.xml"},
+		{path: "nope/x.rpm"},
+	} {
+		got, ok, err := e.MemberRedirect(context.Background(), virt, tc.path, tc.query, "http://h/")
+		if got != tc.want || ok != tc.ok || !errors.Is(err, tc.err) {
+			t.Errorf("%s: got (%q, %v, %v), want (%q, %v, %v)", tc.path, got, ok, err, tc.want, tc.ok, tc.err)
+		}
+	}
+}