flock/pkg/routing/bird/config_fuzz_test.go

package bird

import (
	"strings"
	"testing"
)

// FuzzRender drives the bird template with a wide range of inputs and
// confirms two safety properties:
//
//  1. Render never panics.
//  2. On nil-error return, the output is deterministic (calling Render
//     twice with the same input yields byte-identical output) and contains
//     no unbalanced braces (a smoke test for malformed template branches).
func FuzzRender(f *testing.F) {
	type seed struct {
		routerID string
		asn      uint32
		peerAddr string
		peerASN  uint32
		cidr6    string
		cidr4    string
		anycast6 string
		anycast4 string
		localV6  string
		localV4  string
		subnet6  string
		subnet4  string
	}
	seeds := []seed{
		{routerID: "10.0.0.1", asn: 65101, peerAddr: "2001:db8::1", peerASN: 65000, cidr6: "2001:db8:f001::/64"},
		{routerID: "172.25.25.101", asn: 65101, peerAddr: "172.25.25.1", peerASN: 65000, cidr4: "172.25.210.0/24"},
		{routerID: "10.0.0.1", asn: 65101, peerAddr: "2001:db8::1", peerASN: 65000, cidr6: "2001:db8:f001::/64", anycast6: "2001:db8:a::1"},
		{routerID: "10.0.0.1", asn: 65101, peerAddr: "10.0.0.2", peerASN: 65000, cidr4: "10.0.0.0/24", anycast4: "10.255.0.1"},
		{routerID: "10.0.0.1", asn: 65101},                          // no peer, no cidrs
		{routerID: "", asn: 65101, peerAddr: "10.0.0.2", peerASN: 1}, // empty routerID → expect error
		{routerID: "10.0.0.1", asn: 0, peerAddr: "10.0.0.2", peerASN: 1}, // zero ASN → expect error
		// Backtick-bearing inputs to defend the template against accidental
		// closure of the raw-string literal.
		{routerID: "10.0.0.1`", asn: 65101},
		// Newlines and template-meta in user-supplied addresses
		{routerID: "10.0.0.1", asn: 65101, peerAddr: "2001:db8::1\n{{kaboom}}", peerASN: 65000, cidr6: "2001:db8:f001::/64"},
		// LocalSubnet filters set.
		{routerID: "172.25.25.104", asn: 65104, peerAddr: "2602:817:3000:a25::1", peerASN: 65000, subnet6: "2602:817:3000:a25::/64", subnet4: "172.25.25.0/24"},
		// Malformed subnet should be rejected by validation, not crash.
		{routerID: "10.0.0.1", asn: 65101, subnet6: "not-a-cidr"},
	}
	for _, s := range seeds {
		f.Add(s.routerID, s.asn, s.peerAddr, s.peerASN, s.cidr6, s.cidr4, s.anycast6, s.anycast4, s.localV6, s.localV4, s.subnet6, s.subnet4)
	}

	f.Fuzz(func(t *testing.T, routerID string, asn uint32, peerAddr string, peerASN uint32, cidr6, cidr4, anycast6, anycast4, localV6, localV4, subnet6, subnet4 string) {
		in := NodeBGP{
			RouterID:      routerID,
			LocalASN:      asn,
			LocalV6:       localV6,
			LocalV4:       localV4,
			LocalSubnetV6: subnet6,
			LocalSubnetV4: subnet4,
		}
		// Add the peer in whichever family it belongs to, if any. FamilyOf
		// returns "" for non-IPs; that test exercises the "skip unknown
		// family" branch in the bird agent code path.
		if fam := FamilyOf(peerAddr); fam != "" {
			in.Peers = []Peer{{Family: fam, Address: peerAddr, ASN: peerASN}}
		}
		if cidr6 != "" {
			in.CIDR6 = []string{cidr6}
		}
		if cidr4 != "" {
			in.CIDR4 = []string{cidr4}
		}
		if anycast6 != "" {
			in.Anycast6 = []string{anycast6}
		}
		if anycast4 != "" {
			in.Anycast4 = []string{anycast4}
		}

		out, err := Render(in)
		if err != nil {
			return
		}

		// Determinism.
		out2, err := Render(in)
		if err != nil {
			t.Fatalf("Render became flaky: first ok, second %v", err)
		}
		if out != out2 {
			t.Fatalf("Render not deterministic on identical input")
		}

		// Smoke test for balanced braces. The template uses `{` and `}`
		// as BIRD's block delimiters; if our template engine ever
		// produced an unbalanced output we'd catch it here.
		if got := strings.Count(out, "{") - strings.Count(out, "}"); got != 0 {
			t.Fatalf("unbalanced braces: %d", got)
		}
	})
}