Improve browser caching with signed JWT photo URLs

* JWT tokens will now expire on the 10th of the next month, to produce
  consistent values for a period of time and aid with browser caching.

pkg/controller/chat/chat.go

@@ -131,7 +131,7 @@ func Landing() http.HandlerFunc {
 				Gender:           Gender(currentUser),
 				VIP:              isShy, // "shy accounts" use the "VIP" status for special icon in chat
 				Rules:            rules,
-				RegisteredClaims: encryption.StandardClaims(currentUser.ID, currentUser.Username, 5*time.Minute),
+				RegisteredClaims: encryption.StandardClaims(currentUser.ID, currentUser.Username, time.Now().Add(5*time.Minute)),
 			}
 			token, err := encryption.SignClaims(claims, []byte(config.Current.BareRTC.JWTSecret))
 			if err != nil {

pkg/encryption/jwt.go

@@ -14,11 +14,11 @@ import (
 // It will include values for Subject (username), Issuer (site title), ExpiresAt, IssuedAt, NotBefore.
 //
 // If the userID is >0, the ID field is included.
-func StandardClaims(userID uint64, username string, expires time.Duration) jwt.RegisteredClaims {
+func StandardClaims(userID uint64, username string, expiresAt time.Time) jwt.RegisteredClaims {
 	claim := jwt.RegisteredClaims{
 		Subject:   username,
 		Issuer:    config.Title,
-		ExpiresAt: jwt.NewNumericDate(time.Now().Add(expires)),
+		ExpiresAt: jwt.NewNumericDate(expiresAt),
 		IssuedAt:  jwt.NewNumericDate(time.Now()),
 		NotBefore: jwt.NewNumericDate(time.Now()),
 	}

pkg/photo/photosign.go

@@ -7,6 +7,7 @@ import (
 	"code.nonshy.com/nonshy/website/pkg/encryption"
 	"code.nonshy.com/nonshy/website/pkg/log"
 	"code.nonshy.com/nonshy/website/pkg/models"
+	"code.nonshy.com/nonshy/website/pkg/utility"
 	"github.com/golang-jwt/jwt/v4"
 )
 
@@ -29,7 +30,7 @@ func VisibleAvatarURL(user, currentUser *models.User) string {
 
 // SignedPhotoURL returns a URL path to a photo's filename, signed for the current user only.
 func SignedPhotoURL(user *models.User, filename string) string {
-	return createSignedPhotoURL(user.ID, user.Username, filename, config.SignedPhotoJWTExpires, false)
+	return createSignedPhotoURL(user.ID, user.Username, filename, false)
 }
 
 // SignedPublicAvatarURL returns a signed URL for a user's public square avatar image, which has
@@ -38,7 +39,7 @@ func SignedPhotoURL(user *models.User, filename string) string {
 // The primary use case is for the chat room: users are sent into chat with their avatar URL,
 // and it must be viewable to all users for a long time.
 func SignedPublicAvatarURL(filename string) string {
-	return createSignedPhotoURL(0, "@", filename, config.SignedPublicAvatarJWTExpires, true)
+	return createSignedPhotoURL(0, "@", filename, true)
 }
 
 // SignedPhotoClaims are a JWT claims object used to sign and authenticate image (direct .jpg) links.
@@ -60,13 +61,21 @@ func FilenameHash(filename string) string {
 }
 
 // Common function to create a signed photo URL with an expiration.
-func createSignedPhotoURL(userID uint64, username string, filename string, expires time.Duration, anyone bool) string {
+func createSignedPhotoURL(userID uint64, username string, filename string, anyone bool) string {
 
-	claims := SignedPhotoClaims{
-		FilenameHash:     FilenameHash(filename),
-		Anyone:           anyone,
-		RegisteredClaims: encryption.StandardClaims(userID, username, expires),
-	}
+	// Claims expire on the 10th of next month.
+	var (
+		expiresAt = utility.NextMonth(time.Now(), 10)
+		claims    = SignedPhotoClaims{
+			FilenameHash:     FilenameHash(filename),
+			Anyone:           anyone,
+			RegisteredClaims: encryption.StandardClaims(userID, username, expiresAt),
+		}
+	)
+
+	// Lock the date stamps for a consistent JWT value for caching.
+	claims.IssuedAt = nil
+	claims.NotBefore = nil
 
 	log.Debug("createSignedPhotoURL(%s): %+v", filename, claims)
 

pkg/utility/time.go

@@ -7,6 +7,22 @@ import (
 	"time"
 )
 
+// NextMonth takes an input time (usually time.Now) and will return the next month on the given day.
+//
+// Example, NextMonth from any time in April should return e.g. May 10th.
+func NextMonth(now time.Time, day int) time.Time {
+	var (
+		year, month, _ = now.Date()
+		nextMonth      = month + 1
+	)
+	if nextMonth > 12 {
+		nextMonth = 1
+		year++
+	}
+
+	return time.Date(year, nextMonth, day, 0, 0, 0, 0, now.Location())
+}
+
 // FormatDurationCoarse returns a pretty printed duration with coarse granularity.
 func FormatDurationCoarse(duration time.Duration) string {
 	// Negative durations (e.g. future dates) should work too.

pkg/utility/time_test.go

@@ -7,6 +7,53 @@ import (
 	"code.nonshy.com/nonshy/website/pkg/utility"
 )
 
+func TestNextMonth(t *testing.T) {
+	var tests = []struct {
+		Now    string
+		Day    int
+		Expect string
+	}{
+		{
+			Now:    "1995-08-01",
+			Day:    15,
+			Expect: "1995-09-15",
+		},
+		{
+			Now:    "2006-12-15",
+			Day:    11,
+			Expect: "2007-01-11",
+		},
+		{
+			Now:    "2006-12-01",
+			Day:    15,
+			Expect: "2007-01-15",
+		},
+		{
+			Now:    "2007-01-15",
+			Day:    29, // no leap day
+			Expect: "2007-03-01",
+		},
+		{
+			Now:    "2004-01-08",
+			Day:    29, // leap day
+			Expect: "2004-02-29",
+		},
+	}
+
+	for i, test := range tests {
+		now, err := time.Parse(time.DateOnly, test.Now)
+		if err != nil {
+			t.Errorf("Test #%d: parse error: %s", i, err)
+			continue
+		}
+
+		actual := utility.NextMonth(now, test.Day).Format("2006-01-02")
+		if actual != test.Expect {
+			t.Errorf("Test #%d: expected %s but got %s", i, test.Expect, actual)
+		}
+	}
+}
+
 func TestFormatDurationCoarse(t *testing.T) {
 	var tests = []struct {
 		In     time.Duration