pixa/internal/signature/golden_test.go

package signature

import (
	"testing"
	"time"
)

// goldenExpiresUnix is the fixed expiration timestamp used by all golden
// vectors: 2024-01-01T00:00:00Z.
const goldenExpiresUnix int64 = 1704067200

// goldenSigningKey is the fixed signing key used by all golden vectors.
const goldenSigningKey = "golden-test-key"

// TestSigner_GoldenVectors pins the exact HMAC-SHA256 signature output and
// the exact generated signed URL path for fully-specified requests with a
// hardcoded signing key. The expected values were computed once and are
// hardcoded here as known answers.
//
// If any of these assertions fail, the signed byte format
// ("host:path:query:width:height:format:expiration"), the base64url
// encoding, or the signed URL layout has changed. Such a change breaks
// every signature already issued to clients, so it must be made
// deliberately: update these constants only as part of an intentional,
// documented signature format migration.
func TestSigner_GoldenVectors(t *testing.T) {
	signer := New(goldenSigningKey)

	vectors := []struct {
		name string
		req  Request
		// wantSignature is the exact base64url (RFC 4648 URL-safe,
		// padded) HMAC-SHA256 signature for the request with Expires
		// set to goldenExpiresUnix.
		wantSignature string
		// wantSignedPath is the exact path returned by
		// GenerateSignedURL for the request. The signature and
		// expiration are returned separately by GenerateSignedURL and
		// are not embedded in the path.
		wantSignedPath string
	}{
		{
			name: "resized without query",
			req: Request{
				SourceHost:  "cdn.example.com",
				SourcePath:  "/photos/cat.jpg",
				SourceQuery: "",
				Width:       800,
				Height:      600,
				Format:      "webp",
			},
			// Signed data: "cdn.example.com:/photos/cat.jpg::800:600:webp:1704067200"
			wantSignature:  "x5PfPp8QSDo0cJT96od-AEgrQyOVLfqifH5sst61_-w=",
			wantSignedPath: "/v1/image/cdn.example.com/photos/cat.jpg/800x600.webp",
		},
		{
			name: "resized with query string",
			req: Request{
				SourceHost:  "cdn.example.com",
				SourcePath:  "/photos/cat.jpg",
				SourceQuery: "token=abc&v=2",
				Width:       800,
				Height:      600,
				Format:      "webp",
			},
			// Signed data: "cdn.example.com:/photos/cat.jpg:token=abc&v=2:800:600:webp:1704067200"
			wantSignature:  "394_Vf9TdQFkpQ3XKFDQSyxgqKq8N7mApf2S4QaHqyo=",
			wantSignedPath: "/v1/image/cdn.example.com/photos/cat.jpg%3Ftoken=abc&v=2/800x600.webp",
		},
		{
			name: "original size without query",
			req: Request{
				SourceHost:  "cdn.example.com",
				SourcePath:  "/photos/cat.jpg",
				SourceQuery: "",
				Width:       0,
				Height:      0,
				Format:      "png",
			},
			// Signed data: "cdn.example.com:/photos/cat.jpg::0:0:png:1704067200"
			wantSignature:  "7Be7oteeQwvnSPU4bchyQ4ZGYGsAGBKpeEtuQ02ox60=",
			wantSignedPath: "/v1/image/cdn.example.com/photos/cat.jpg/orig.png",
		},
	}

	for _, tt := range vectors {
		t.Run(tt.name, func(t *testing.T) {
			signReq := tt.req
			signReq.Expires = time.Unix(goldenExpiresUnix, 0)

			gotSignature := signer.Sign(&signReq)
			if gotSignature != tt.wantSignature {
				t.Errorf("Sign() = %q, want %q (signed byte format changed?)",
					gotSignature, tt.wantSignature)
			}

			urlReq := tt.req
			gotPath, _, _ := signer.GenerateSignedURL(&urlReq, time.Hour)
			if gotPath != tt.wantSignedPath {
				t.Errorf("GenerateSignedURL() path = %q, want %q (signed URL layout changed?)",
					gotPath, tt.wantSignedPath)
			}
		})
	}
}