pixa/internal/signature/golden_test.go

package signature_test

import (
	"testing"
	"time"

	"sneak.berlin/go/pixa/internal/signature"
)

// 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"

type goldenVector struct {
	name string
	req  signature.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
}

// goldenVectors returns the known-answer vectors. The expected values
// were computed once and are hardcoded here.
func goldenVectors() []goldenVector {
	return []goldenVector{
		{
			name: "resized without query",
			req: signature.Request{
				SourceHost:  testHost,
				SourcePath:  testPath,
				SourceQuery: "",
				Width:       800,
				Height:      600,
				Format:      testFormatWebP,
				Quality:     85,
				FitMode:     testFitCover,
			},
			// Signed data:
			// "cdn.example.com:/photos/cat.jpg::800:600:webp:1704067200:85:cover"
			wantSignature:  "kdqeGoW2SX7qnaYtoB970wEnLydn0UnIgQYQLfAnjXQ=",
			wantSignedPath: testSignedPath,
		},
		{
			name: "resized with query string",
			req: signature.Request{
				SourceHost:  testHost,
				SourcePath:  testPath,
				SourceQuery: "token=abc&v=2",
				Width:       800,
				Height:      600,
				Format:      testFormatWebP,
				Quality:     85,
				FitMode:     testFitCover,
			},
			// Signed data:
			// "cdn.example.com:/photos/cat.jpg:token=abc&v=2:800:600:webp:1704067200:85:cover"
			wantSignature: "pKgVBOTd_Q_EikI7MNQLC9Q8Hurdxzyv3EIYvVhqc2I=",
			wantSignedPath: "/v1/image/cdn.example.com/photos/cat.jpg" +
				"%3Ftoken=abc&v=2/800x600.webp",
		},
		{
			name: "original size without query",
			req: signature.Request{
				SourceHost:  testHost,
				SourcePath:  testPath,
				SourceQuery: "",
				Width:       0,
				Height:      0,
				Format:      testFormatPNG,
				Quality:     85,
				FitMode:     testFitCover,
			},
			// Signed data:
			// "cdn.example.com:/photos/cat.jpg::0:0:png:1704067200:85:cover"
			wantSignature:  "6_rZ0yyVbGZRs8kG7n7HLgLi5Jt8vjiWQljIEL1jbIs=",
			wantSignedPath: "/v1/image/cdn.example.com/photos/cat.jpg/orig.png",
		},
		{
			name: "non-default quality and fit",
			req: signature.Request{
				SourceHost:  testHost,
				SourcePath:  testPath,
				SourceQuery: "",
				Width:       800,
				Height:      600,
				Format:      testFormatWebP,
				Quality:     40,
				FitMode:     testFitContain,
			},
			// Signed data:
			// "cdn.example.com:/photos/cat.jpg::800:600:webp:1704067200:40:contain"
			wantSignature: "pGaXpPUbI3A7nMx-4T9bfq9bYWBNL0kY4bxlcv3g1F8=",
			// The path is the same as for the default quality and fit:
			// q=40&fit=contain go in the query string next to sig and
			// exp (imgcache.Service.GenerateSignedURL adds all four).
			wantSignedPath: testSignedPath,
		},
	}
}

// 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.
//
// If any of these assertions fail, the signed byte format
// ("host:path:query:width:height:format:expiration:quality:fit"), the
// base64url encoding, or the signed URL layout has changed. Update these
// constants only when that change is intended.
func TestSigner_GoldenVectors(t *testing.T) {
	t.Parallel()

	signer := signature.New(goldenSigningKey)

	for _, tt := range goldenVectors() {
		t.Run(tt.name, func(t *testing.T) {
			t.Parallel()

			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)
			}
		})
	}
}