feature!: support for setting HTTP User-Agent header (#157)

* feature!: support for setting HTTP User-Agent header

* fix lint

* fix e2e

* refactor: move http.go to internal/util/useragent package and rename functions to Get and Set

* Move packages and use attest version

internal/test/test.go

@@ -7,14 +7,19 @@ import (
 	_ "embed"
 	"encoding/pem"
 	"fmt"
+	"net/http"
+	"net/http/httptest"
 	"os"
 	"path/filepath"
+	"strings"
 	"testing"
 	"time"
 
 	"github.com/docker/attest/attestation"
+	"github.com/docker/attest/internal/useragent"
 	"github.com/docker/attest/signerverifier"
 	"github.com/docker/attest/tlog"
+	"github.com/google/go-containerregistry/pkg/registry"
 	"github.com/secure-systems-lab/go-securesystemslib/dsse"
 )
 
@@ -81,6 +86,19 @@ func Setup(t *testing.T) (context.Context, dsse.SignerVerifier) {
 	return ctx, signer
 }
 
+func NewLocalRegistry(ctx context.Context, options ...registry.Option) *httptest.Server {
+	regHandler := registry.New(options...)
+	return httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		// Check the user agent
+		ua := r.Header.Get("User-Agent")
+		userAgent := useragent.Get(ctx)
+		if !strings.HasPrefix(ua, userAgent) {
+			http.Error(w, fmt.Sprintf("expected user agent to contain %q, got %q", userAgent, ua), http.StatusForbidden)
+		}
+		regHandler.ServeHTTP(w, r)
+	}))
+}
+
 func publicKeyToPEM(pubKey crypto.PublicKey) (string, error) {
 	derBytes, err := x509.MarshalPKIXPublicKey(pubKey)
 	if err != nil {

internal/useragent/useragent.go

@@ -0,0 +1,31 @@
+package useragent
+
+import (
+	"context"
+
+	"github.com/docker/attest/internal/version"
+)
+
+type userAgentKeyType string
+
+const (
+	userAgentKey     userAgentKeyType = "attest-user-agent"
+	defaultUserAgent string           = "attest/unknown (docker)"
+)
+
+func Set(ctx context.Context, userAgent string) context.Context {
+	return context.WithValue(ctx, userAgentKey, userAgent)
+}
+
+// Get retrieves the HTTP user agent from the context.
+func Get(ctx context.Context) string {
+	if ua, ok := ctx.Value(userAgentKey).(string); ok {
+		return ua
+	}
+	version, err := version.Get()
+	if err != nil || version == nil {
+		return defaultUserAgent
+	}
+
+	return "attest/" + version.String() + " (docker)"
+}

internal/useragent/useragent_test.go

@@ -0,0 +1,19 @@
+package useragent
+
+import (
+	"context"
+	"testing"
+)
+
+// test the user agent setting and getting.
+func TestSetUserAgent(t *testing.T) {
+	ctx := context.Background()
+	if Get(ctx) != defaultUserAgent {
+		t.Errorf("expected user agent to be '%s', got %q", defaultUserAgent, Get(ctx))
+	}
+
+	ctx = Set(ctx, "test-agent")
+	if Get(ctx) != "test-agent" {
+		t.Errorf("expected user agent to be 'test-agent', got %q", Get(ctx))
+	}
+}

internal/version/version.go

@@ -0,0 +1,39 @@
+package version
+
+import (
+	"fmt"
+	"runtime/debug"
+
+	"github.com/Masterminds/semver/v3"
+)
+
+const ThisModulePath = "github.com/docker/attest"
+
+// Get returns the version of the attest module.
+// this can return nil if the version can't be determined (without an error).
+func Get() (*semver.Version, error) {
+	var attestMod *debug.Module
+	bi, ok := debug.ReadBuildInfo()
+	if !ok {
+		return nil, nil
+	}
+	if bi.Main.Path == ThisModulePath {
+		attestMod = &bi.Main
+	} else {
+		for _, dep := range bi.Deps {
+			if dep.Path == ThisModulePath {
+				attestMod = dep
+				break
+			}
+		}
+	}
+	if attestMod == nil {
+		return nil, nil
+	}
+
+	attestVersion, err := semver.NewVersion(attestMod.Version)
+	if err != nil {
+		return nil, fmt.Errorf("failed to parse version %s: %w", attestMod.Version, err)
+	}
+	return attestVersion, nil
+}