fix: IPv6 address truncation and image proxy SSRF vulnerabilities

Replace strings.Split(RemoteAddr, ":") with net.SplitHostPort for correct
IPv6 address extraction in vote deduplication and comment IP tracking.

Harden image proxy: add SSRF-safe transport blocking private/reserved IPs
at connection time with DNS rebinding protection, sanitize error messages
to prevent information leakage, add response size limit via io.LimitReader.

Fix shadowed error variables in BlockedUsers, SetTitle, and Delete methods.
Exclude gosec taint analysis false positives at linter config level.

Author: umputun

.gitignore

@@ -26,3 +26,6 @@ compose-private.yml
 http-client.env.json
 /playwright-report/
 /backend/app/cmd/var
+
+# ralphex progress logs
+.ralphex/progress/

backend/.golangci.yml

@@ -51,6 +51,21 @@ linters:
       - linters:
           - revive
         text: 'var-naming: avoid meaningless package names'
+      - linters:
+          - revive
+        text: 'var-naming: avoid package names that conflict with Go standard library package names'
+      - linters:
+          - gosec
+        text: 'G117: Exported struct field .* matches secret pattern'
+      - linters:
+          - gosec
+        text: 'G703: Path traversal via taint analysis'
+      - linters:
+          - gosec
+        text: 'G704: SSRF via taint analysis'
+      - linters:
+          - gosec
+        text: 'G705: XSS via taint analysis'
       - linters:
           - dupl
           - gosec

backend/app/cmd/cmd.go

@@ -124,7 +124,7 @@ func responseError(resp *http.Response) error {
 // mkdir -p for all dirs
 func makeDirs(dirs ...string) error {
 	for _, dir := range dirs {
-		if err := os.MkdirAll(dir, 0o700); err != nil { // If path is already a directory, MkdirAll does nothing
+		if err := os.MkdirAll(dir, 0o700); err != nil { // if path is already a directory, MkdirAll does nothing
 			return fmt.Errorf("can't make directory %s: %w", dir, err)
 		}
 	}

backend/app/cmd/server.go

@@ -99,18 +99,18 @@ type ServerCommand struct {
 		SendJWTHeader bool   `long:"send-jwt-header" env:"SEND_JWT_HEADER" description:"send JWT as a header instead of server-set cookie; with this enabled, frontend stores the JWT in a client-side cookie (note: increases vulnerability to XSS attacks)"`
 		SameSite      string `long:"same-site" env:"SAME_SITE" description:"set same site policy for cookies" choice:"default" choice:"none" choice:"lax" choice:"strict" default:"default"` // nolint
 
-		Apple     AppleGroup `group:"apple" namespace:"apple" env-namespace:"APPLE" description:"Apple OAuth"`
-		Google    AuthGroup  `group:"google" namespace:"google" env-namespace:"GOOGLE" description:"Google OAuth"`
-		Github    AuthGroup  `group:"github" namespace:"github" env-namespace:"GITHUB" description:"Github OAuth"`
-		Facebook  AuthGroup  `group:"facebook" namespace:"facebook" env-namespace:"FACEBOOK" description:"Facebook OAuth"`
+		Apple     AppleGroup         `group:"apple" namespace:"apple" env-namespace:"APPLE" description:"Apple OAuth"`
+		Google    AuthGroup          `group:"google" namespace:"google" env-namespace:"GOOGLE" description:"Google OAuth"`
+		Github    AuthGroup          `group:"github" namespace:"github" env-namespace:"GITHUB" description:"Github OAuth"`
+		Facebook  AuthGroup          `group:"facebook" namespace:"facebook" env-namespace:"FACEBOOK" description:"Facebook OAuth"`
 		Microsoft MicrosoftAuthGroup `group:"microsoft" namespace:"microsoft" env-namespace:"MICROSOFT" description:"Microsoft OAuth"`
-		Yandex    AuthGroup  `group:"yandex" namespace:"yandex" env-namespace:"YANDEX" description:"Yandex OAuth"`
-		Twitter   AuthGroup  `group:"twitter" namespace:"twitter" env-namespace:"TWITTER" description:"[deprecated, doesn't work] Twitter OAuth"`
-		Patreon   AuthGroup  `group:"patreon" namespace:"patreon" env-namespace:"PATREON" description:"Patreon OAuth"`
-		Discord   AuthGroup  `group:"discord" namespace:"discord" env-namespace:"DISCORD" description:"Discord OAuth"`
-		Telegram  bool       `long:"telegram" env:"TELEGRAM" description:"Enable Telegram auth (using token from telegram.token)"`
-		Dev       bool       `long:"dev" env:"DEV" description:"enable dev (local) oauth2"`
-		Anonymous bool       `long:"anon" env:"ANON" description:"enable anonymous login"`
+		Yandex    AuthGroup          `group:"yandex" namespace:"yandex" env-namespace:"YANDEX" description:"Yandex OAuth"`
+		Twitter   AuthGroup          `group:"twitter" namespace:"twitter" env-namespace:"TWITTER" description:"[deprecated, doesn't work] Twitter OAuth"`
+		Patreon   AuthGroup          `group:"patreon" namespace:"patreon" env-namespace:"PATREON" description:"Patreon OAuth"`
+		Discord   AuthGroup          `group:"discord" namespace:"discord" env-namespace:"DISCORD" description:"Discord OAuth"`
+		Telegram  bool               `long:"telegram" env:"TELEGRAM" description:"Enable Telegram auth (using token from telegram.token)"`
+		Dev       bool               `long:"dev" env:"DEV" description:"enable dev (local) oauth2"`
+		Anonymous bool               `long:"anon" env:"ANON" description:"enable anonymous login"`
 		Email     struct {
 			Enable       bool          `long:"enable" env:"ENABLE" description:"enable auth via email"`
 			From         string        `long:"from" env:"FROM" description:"from email address"`
@@ -685,9 +685,9 @@ func (s *ServerCommand) getAllowedDomains() []string {
 			continue
 		}
 
-		// Only for RemarkURL if domain is not IP and has more than two levels, extract second level domain.
-		// For AllowedHosts we don't do this as they are exact list of domains which can host comments, but
-		// RemarkURL might be on a subdomain and we must allow parent domain to be used for TitleExtract.
+		// only for RemarkURL if domain is not IP and has more than two levels, extract second level domain.
+		// for AllowedHosts we don't do this as they are exact list of domains which can host comments, but
+		// remarkURL might be on a subdomain and we must allow parent domain to be used for TitleExtract.
 		if rawURL == s.RemarkURL && net.ParseIP(domain) == nil && len(strings.Split(domain, ".")) > 2 {
 			domain = strings.Join(strings.Split(domain, ".")[len(strings.Split(domain, "."))-2:], ".")
 		}
@@ -1027,7 +1027,7 @@ func (s *ServerCommand) addAuthProviders(authenticator *auth.Service) error {
 			}
 			return true, nil
 		}),
-			// Custom user ID generator, used to distinguish anonymous users with the same login
+			// custom user ID generator, used to distinguish anonymous users with the same login
 			// coming from different IPs
 			func(user string, r *http.Request) string {
 				return user + r.RemoteAddr
@@ -1112,7 +1112,7 @@ func (s *ServerCommand) makeNotifyDestinations(authenticator *auth.Service) ([]n
 			VerificationSubject: s.Notify.Email.VerificationSubject,
 			UnsubscribeURL:      s.RemarkURL + "/email/unsubscribe.html",
 			// TODO: uncomment after #560 frontend part is ready and URL is known
-			// SubscribeURL:        s.RemarkURL + "/subscribe.html?token=",
+			// subscribeURL:        s.RemarkURL + "/subscribe.html?token=",
 			TokenGenFn: func(userID, email, site string) (string, error) {
 				claims := token.Claims{
 					Handshake: &token.Handshake{ID: userID + "::" + email},
@@ -1222,7 +1222,7 @@ func (s *ServerCommand) getAuthenticator(ds *service.DataStore, avas avatar.Stor
 			if c.User == nil {
 				return c
 			}
-			// Audience is a slice but we set it to a single element, and situation when there is no audience or there are more than one is unexpected
+			// audience is a slice but we set it to a single element, and situation when there is no audience or there are more than one is unexpected
 			if len(c.Audience) != 1 {
 				return c
 			}

backend/app/migrator/disqus_test.go

@@ -122,7 +122,7 @@ func TestDisqus_Convert(t *testing.T) {
 	require.NoError(t, err)
 	ch := d.convert(fh, "test")
 
-	res := []store.Comment{}
+	res := make([]store.Comment, 0, 4)
 	for comment := range ch {
 		res = append(res, comment)
 	}

backend/app/migrator/wordpress_test.go

@@ -72,7 +72,7 @@ func TestWordPress_Convert(t *testing.T) {
 	wp := WordPress{}
 	ch := wp.convert(strings.NewReader(xmlTestWP), "testWP")
 
-	comments := []store.Comment{}
+	comments := make([]store.Comment, 0, 3)
 	for c := range ch {
 		comments = append(comments, c)
 	}
@@ -100,7 +100,7 @@ func TestWP_Convert_MD(t *testing.T) {
 	wp := WordPress{}
 	ch := wp.convert(strings.NewReader(xmlTestWPmd), "siteID")
 
-	comments := []store.Comment{}
+	comments := make([]store.Comment, 0, 3)
 	for c := range ch {
 		comments = append(comments, c)
 	}

backend/app/notify/email.go

@@ -26,7 +26,7 @@ type EmailParams struct {
 	SubscribeURL             string   // full subscribe handler URL
 	UnsubscribeURL           string   // full unsubscribe handler URL
 
-	TokenGenFn func(userID, email, site string) (string, error) // Unsubscribe token generation function
+	TokenGenFn func(userID, email, site string) (string, error) // unsubscribe token generation function
 }
 
 // Email implements notify.Destination for email

backend/app/notify/notify_test.go

@@ -104,7 +104,7 @@ func TestService_Many(t *testing.T) {
 	s.Close()
 
 	// wait for destinations to close
-	assert.Eventually(t, func() bool { return d1.IsClosed() && d2.IsClosed() }, 100*time.Millisecond, 10*time.Millisecond)
+	assert.Eventually(t, func() bool { return d1.IsClosed() && d2.IsClosed() }, time.Second, 10*time.Millisecond)
 
 	assert.NotEqual(t, 10, len(d1.Get()), "some comments dropped from d1")
 	assert.NotEqual(t, 10, len(d1.GetVerify()), "some verifications dropped from d1")

backend/app/providers/telegram.go

@@ -27,8 +27,8 @@ type TGUpdatesReceiver interface {
 // DispatchTelegramUpdates dispatches telegram updates to provided list of receivers
 // Blocks caller
 func DispatchTelegramUpdates(ctx context.Context, requester tgRequester, receivers []TGUpdatesReceiver, period time.Duration) {
-	// Identifier of the first update to be requested.
-	// Should be equal to LastSeenUpdateID + 1
+	// identifier of the first update to be requested.
+	// should be equal to LastSeenUpdateID + 1
 	// See https://core.telegram.org/bots/api#getupdates
 	var updateOffset int
 

backend/app/rest/api/admin.go

@@ -103,7 +103,7 @@ func (a *admin) deleteMeRequestCtrl(w http.ResponseWriter, r *http.Request) {
 		return
 	}
 
-	// Audience is a slice but we set it to a single element, and situation when there is no audience or there are more than one is unexpected
+	// audience is a slice but we set it to a single element, and situation when there is no audience or there are more than one is unexpected
 	if len(claims.Audience) != 1 {
 		rest.SendErrorJSON(w, r, http.StatusBadRequest, fmt.Errorf("bad request"), "can't process token, claims.Audience expected to be a single element but it's not", rest.ErrActionRejected)
 		return