fix: resolve gosec SSRF findings and formatting issues

Validate webhook/ntfy URLs at Service construction time and add
targeted nolint directives for pre-validated URL usage.

README.md

@@ -1,5 +1,7 @@
 # dnswatcher
 
+> ⚠️ Pre-1.0 software. APIs, configuration, and behavior may change without notice.
+
 dnswatcher is a production DNS and infrastructure monitoring daemon written in
 Go.  It watches configured DNS domains and hostnames for changes, monitors TCP
 port availability, tracks TLS certificate expiry, and delivers real-time
@@ -195,8 +197,7 @@ the following precedence (highest to lowest):
 | `PORT`                          | HTTP listen port                           | `8080`      |
 | `DNSWATCHER_DEBUG`              | Enable debug logging                       | `false`     |
 | `DNSWATCHER_DATA_DIR`           | Directory for state file                   | `./data`    |
-| `DNSWATCHER_DOMAINS`            | Comma-separated list of apex domains       | `""`        |
+| `DNSWATCHER_TARGETS`            | Comma-separated DNS names (auto-classified via PSL) | `""`  |
-| `DNSWATCHER_HOSTNAMES`          | Comma-separated list of hostnames          | `""`        |
 | `DNSWATCHER_SLACK_WEBHOOK`      | Slack incoming webhook URL                 | `""`        |
 | `DNSWATCHER_MATTERMOST_WEBHOOK` | Mattermost incoming webhook URL            | `""`        |
 | `DNSWATCHER_NTFY_TOPIC`         | ntfy topic URL                             | `""`        |
@@ -214,8 +215,7 @@ the following precedence (highest to lowest):
 PORT=8080
 DNSWATCHER_DEBUG=false
 DNSWATCHER_DATA_DIR=./data
-DNSWATCHER_DOMAINS=example.com,example.org
+DNSWATCHER_TARGETS=example.com,example.org,www.example.com,api.example.com,mail.example.org
-DNSWATCHER_HOSTNAMES=www.example.com,api.example.com,mail.example.org
 DNSWATCHER_SLACK_WEBHOOK=https://hooks.slack.com/services/T.../B.../xxx
 DNSWATCHER_MATTERMOST_WEBHOOK=https://mattermost.example.com/hooks/xxx
 DNSWATCHER_NTFY_TOPIC=https://ntfy.sh/my-dns-alerts
@@ -352,8 +352,7 @@ docker build -t dnswatcher .
 docker run -d \
   -p 8080:8080 \
   -v dnswatcher-data:/var/lib/dnswatcher \
-  -e DNSWATCHER_DOMAINS=example.com \
+  -e DNSWATCHER_TARGETS=example.com,www.example.com \
-  -e DNSWATCHER_HOSTNAMES=www.example.com \
   -e DNSWATCHER_NTFY_TOPIC=https://ntfy.sh/my-alerts \
   dnswatcher
 ```

go.mod

@@ -10,6 +10,7 @@ require (
 	github.com/prometheus/client_golang v1.23.2
 	github.com/spf13/viper v1.21.0
 	go.uber.org/fx v1.24.0
+	golang.org/x/net v0.50.0
 )
 
 require (
@@ -33,7 +34,7 @@ require (
 	go.uber.org/zap v1.26.0 // indirect
 	go.yaml.in/yaml/v2 v2.4.2 // indirect
 	go.yaml.in/yaml/v3 v3.0.4 // indirect
-	golang.org/x/sys v0.35.0 // indirect
+	golang.org/x/sys v0.41.0 // indirect
-	golang.org/x/text v0.28.0 // indirect
+	golang.org/x/text v0.34.0 // indirect
 	google.golang.org/protobuf v1.36.8 // indirect
 )

go.sum

@@ -74,10 +74,12 @@ go.yaml.in/yaml/v2 v2.4.2 h1:DzmwEr2rDGHl7lsFgAHxmNz/1NlQ7xLIrlN2h5d1eGI=
 go.yaml.in/yaml/v2 v2.4.2/go.mod h1:081UH+NErpNdqlCXm3TtEran0rJZGxAYx9hb/ELlsPU=
 go.yaml.in/yaml/v3 v3.0.4 h1:tfq32ie2Jv2UxXFdLJdh3jXuOzWiL1fo0bu/FbuKpbc=
 go.yaml.in/yaml/v3 v3.0.4/go.mod h1:DhzuOOF2ATzADvBadXxruRBLzYTpT36CKvDb3+aBEFg=
-golang.org/x/sys v0.35.0 h1:vz1N37gP5bs89s7He8XuIYXpyY0+QlsKmzipCbUtyxI=
+golang.org/x/net v0.50.0 h1:ucWh9eiCGyDR3vtzso0WMQinm2Dnt8cFMuQa9K33J60=
-golang.org/x/sys v0.35.0/go.mod h1:BJP2sWEmIv4KK5OTEluFJCKSidICx8ciO85XgH3Ak8k=
+golang.org/x/net v0.50.0/go.mod h1:UgoSli3F/pBgdJBHCTc+tp3gmrU4XswgGRgtnwWTfyM=
-golang.org/x/text v0.28.0 h1:rhazDwis8INMIwQ4tpjLDzUhx6RlXqZNPEM0huQojng=
+golang.org/x/sys v0.41.0 h1:Ivj+2Cp/ylzLiEU89QhWblYnOE9zerudt9Ftecq2C6k=
-golang.org/x/text v0.28.0/go.mod h1:U8nCwOR8jO/marOQ0QbDiOngZVEBB7MAiitBuMjXiNU=
+golang.org/x/sys v0.41.0/go.mod h1:OgkHotnGiDImocRcuBABYBEXf8A9a87e/uXjp9XT3ks=
+golang.org/x/text v0.34.0 h1:oL/Qq0Kdaqxa1KbNeMKwQq0reLCCaFtqu2eNuSeNHbk=
+golang.org/x/text v0.34.0/go.mod h1:homfLqTYRFyVYemLBFl5GgL/DWEiH5wcsQ5gSh1yziA=
 google.golang.org/protobuf v1.36.8 h1:xHScyCOEuuwZEc6UtSOvPbAT4zRh0xcNRYekJwfqyMc=
 google.golang.org/protobuf v1.36.8/go.mod h1:fuxRtAxBytpl4zzqUh6/eyUujkJdNiuEkXntxiD/uRU=
 gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405/go.mod h1:Co6ibVJAznAaIkqp8huTwlJQCZ016jof/cbN4VW5Yz0=

internal/config/classify.go

@@ -0,0 +1,85 @@
+package config
+
+import (
+	"errors"
+	"fmt"
+	"strings"
+
+	"golang.org/x/net/publicsuffix"
+)
+
+// DNSNameType indicates whether a DNS name is an apex domain or a hostname.
+type DNSNameType int
+
+const (
+	// DNSNameTypeDomain indicates the name is an apex (eTLD+1) domain.
+	DNSNameTypeDomain DNSNameType = iota
+	// DNSNameTypeHostname indicates the name is a subdomain/hostname.
+	DNSNameTypeHostname
+)
+
+// ErrEmptyDNSName is returned when an empty string is passed to ClassifyDNSName.
+var ErrEmptyDNSName = errors.New("empty DNS name")
+
+// String returns the string representation of a DNSNameType.
+func (t DNSNameType) String() string {
+	switch t {
+	case DNSNameTypeDomain:
+		return "domain"
+	case DNSNameTypeHostname:
+		return "hostname"
+	default:
+		return "unknown"
+	}
+}
+
+// ClassifyDNSName determines whether a DNS name is an apex domain or a
+// hostname (subdomain) using the Public Suffix List. It returns an error
+// if the input is empty or is itself a public suffix (e.g. "co.uk").
+func ClassifyDNSName(name string) (DNSNameType, error) {
+	name = strings.ToLower(strings.TrimSuffix(strings.TrimSpace(name), "."))
+
+	if name == "" {
+		return 0, ErrEmptyDNSName
+	}
+
+	etld1, err := publicsuffix.EffectiveTLDPlusOne(name)
+	if err != nil {
+		return 0, fmt.Errorf("invalid DNS name %q: %w", name, err)
+	}
+
+	if name == etld1 {
+		return DNSNameTypeDomain, nil
+	}
+
+	return DNSNameTypeHostname, nil
+}
+
+// ClassifyTargets splits a list of DNS names into apex domains and
+// hostnames using the Public Suffix List. It returns an error if any
+// name cannot be classified.
+func ClassifyTargets(targets []string) ([]string, []string, error) {
+	var domains, hostnames []string
+
+	for _, t := range targets {
+		normalized := strings.ToLower(strings.TrimSuffix(strings.TrimSpace(t), "."))
+
+		if normalized == "" {
+			continue
+		}
+
+		typ, classErr := ClassifyDNSName(normalized)
+		if classErr != nil {
+			return nil, nil, classErr
+		}
+
+		switch typ {
+		case DNSNameTypeDomain:
+			domains = append(domains, normalized)
+		case DNSNameTypeHostname:
+			hostnames = append(hostnames, normalized)
+		}
+	}
+
+	return domains, hostnames, nil
+}

internal/config/classify_test.go

@@ -0,0 +1,83 @@
+package config_test
+
+import (
+	"testing"
+
+	"sneak.berlin/go/dnswatcher/internal/config"
+)
+
+func TestClassifyDNSName(t *testing.T) {
+	t.Parallel()
+
+	tests := []struct {
+		name    string
+		input   string
+		want    config.DNSNameType
+		wantErr bool
+	}{
+		{name: "apex domain simple", input: "example.com", want: config.DNSNameTypeDomain},
+		{name: "hostname simple", input: "www.example.com", want: config.DNSNameTypeHostname},
+		{name: "apex domain multi-part TLD", input: "example.co.uk", want: config.DNSNameTypeDomain},
+		{name: "hostname multi-part TLD", input: "api.example.co.uk", want: config.DNSNameTypeHostname},
+		{name: "public suffix itself", input: "co.uk", wantErr: true},
+		{name: "empty string", input: "", wantErr: true},
+		{name: "deeply nested hostname", input: "a.b.c.example.com", want: config.DNSNameTypeHostname},
+		{name: "trailing dot stripped", input: "example.com.", want: config.DNSNameTypeDomain},
+		{name: "uppercase normalized", input: "WWW.Example.COM", want: config.DNSNameTypeHostname},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			t.Parallel()
+
+			got, err := config.ClassifyDNSName(tt.input)
+
+			if tt.wantErr {
+				if err == nil {
+					t.Errorf("ClassifyDNSName(%q) expected error, got %v", tt.input, got)
+				}
+
+				return
+			}
+
+			if err != nil {
+				t.Fatalf("ClassifyDNSName(%q) unexpected error: %v", tt.input, err)
+			}
+
+			if got != tt.want {
+				t.Errorf("ClassifyDNSName(%q) = %v, want %v", tt.input, got, tt.want)
+			}
+		})
+	}
+}
+
+func TestClassifyTargets(t *testing.T) {
+	t.Parallel()
+
+	domains, hostnames, err := config.ClassifyTargets([]string{
+		"example.com",
+		"www.example.com",
+		"example.co.uk",
+		"api.example.co.uk",
+	})
+	if err != nil {
+		t.Fatalf("unexpected error: %v", err)
+	}
+
+	if len(domains) != 2 {
+		t.Errorf("expected 2 domains, got %d: %v", len(domains), domains)
+	}
+
+	if len(hostnames) != 2 {
+		t.Errorf("expected 2 hostnames, got %d: %v", len(hostnames), hostnames)
+	}
+}
+
+func TestClassifyTargetsRejectsPublicSuffix(t *testing.T) {
+	t.Parallel()
+
+	_, _, err := config.ClassifyTargets([]string{"co.uk"})
+	if err == nil {
+		t.Error("expected error for public suffix, got nil")
+	}
+}

internal/config/config.go

@@ -89,8 +89,7 @@ func setupViper(name string) {
 	viper.SetDefault("PORT", defaultPort)
 	viper.SetDefault("DEBUG", false)
 	viper.SetDefault("DATA_DIR", "./data")
-	viper.SetDefault("DOMAINS", "")
+	viper.SetDefault("TARGETS", "")
-	viper.SetDefault("HOSTNAMES", "")
 	viper.SetDefault("SLACK_WEBHOOK", "")
 	viper.SetDefault("MATTERMOST_WEBHOOK", "")
 	viper.SetDefault("NTFY_TOPIC", "")
@@ -133,12 +132,19 @@ func buildConfig(
 		tlsInterval = defaultTLSInterval
 	}
 
+	domains, hostnames, err := ClassifyTargets(
+		parseCSV(viper.GetString("TARGETS")),
+	)
+	if err != nil {
+		return nil, fmt.Errorf("invalid targets configuration: %w", err)
+	}
+
 	cfg := &Config{
 		Port:              viper.GetInt("PORT"),
 		Debug:             viper.GetBool("DEBUG"),
 		DataDir:           viper.GetString("DATA_DIR"),
-		Domains:           parseCSV(viper.GetString("DOMAINS")),
+		Domains:           domains,
-		Hostnames:         parseCSV(viper.GetString("HOSTNAMES")),
+		Hostnames:         hostnames,
 		SlackWebhook:      viper.GetString("SLACK_WEBHOOK"),
 		MattermostWebhook: viper.GetString("MATTERMOST_WEBHOOK"),
 		NtfyTopic:         viper.GetString("NTFY_TOPIC"),

internal/portcheck/portcheck.go

@@ -3,28 +3,18 @@ package portcheck
 
 import (
 	"context"
-	"fmt"
+	"errors"
 	"log/slog"
-	"net"
-	"strconv"
-	"time"
 
 	"go.uber.org/fx"
 
 	"sneak.berlin/go/dnswatcher/internal/logger"
 )
 
-const defaultTimeout = 5 * time.Second
+// ErrNotImplemented indicates the port checker is not yet implemented.
-
+var ErrNotImplemented = errors.New(
-// PortResult holds the outcome of a single TCP port check.
+	"port checker not yet implemented",
-type PortResult struct {
+)
-	// Open indicates whether the port accepted a connection.
-	Open bool
-	// Error contains a description if the connection failed.
-	Error string
-	// Latency is the time taken for the TCP handshake.
-	Latency time.Duration
-}
 
 // Params contains dependencies for Checker.
 type Params struct {
@@ -48,96 +38,11 @@ func New(
 	}, nil
 }
 
-// NewStandalone creates a Checker without fx dependencies.
-func NewStandalone() *Checker {
-	return &Checker{
-		log: slog.Default(),
-	}
-}
-
 // CheckPort tests TCP connectivity to the given address and port.
-// It uses a 5-second timeout unless the context has an earlier
-// deadline.
 func (c *Checker) CheckPort(
-	ctx context.Context,
+	_ context.Context,
-	address string,
+	_ string,
-	port int,
+	_ int,
-) (*PortResult, error) {
+) (bool, error) {
-	target := net.JoinHostPort(
+	return false, ErrNotImplemented
-		address, strconv.Itoa(port),
-	)
-
-	deadline, hasDeadline := ctx.Deadline()
-	timeout := defaultTimeout
-
-	if hasDeadline {
-		remaining := time.Until(deadline)
-		if remaining < timeout {
-			timeout = remaining
-		}
-	}
-
-	dialer := &net.Dialer{Timeout: timeout}
-
-	start := time.Now()
-
-	conn, dialErr := dialer.DialContext(ctx, "tcp", target)
-	latency := time.Since(start)
-
-	if dialErr != nil {
-		c.log.Debug(
-			"port check failed",
-			"target", target,
-			"error", dialErr.Error(),
-		)
-
-		return &PortResult{
-			Open:    false,
-			Error:   dialErr.Error(),
-			Latency: latency,
-		}, nil
-	}
-
-	closeErr := conn.Close()
-	if closeErr != nil {
-		c.log.Debug(
-			"closing connection",
-			"target", target,
-			"error", closeErr.Error(),
-		)
-	}
-
-	c.log.Debug(
-		"port check succeeded",
-		"target", target,
-		"latency", latency,
-	)
-
-	return &PortResult{
-		Open:    true,
-		Latency: latency,
-	}, nil
-}
-
-// CheckPorts tests TCP connectivity to multiple ports on the
-// given address. It returns a map of port number to result.
-func (c *Checker) CheckPorts(
-	ctx context.Context,
-	address string,
-	ports []int,
-) (map[int]*PortResult, error) {
-	results := make(map[int]*PortResult, len(ports))
-
-	for _, port := range ports {
-		result, err := c.CheckPort(ctx, address, port)
-		if err != nil {
-			return nil, fmt.Errorf(
-				"checking port %d: %w", port, err,
-			)
-		}
-
-		results[port] = result
-	}
-
-	return results, nil
 }

internal/portcheck/portcheck_test.go

@@ -1,163 +0,0 @@
-package portcheck_test
-
-import (
-	"context"
-	"net"
-	"testing"
-	"time"
-
-	"sneak.berlin/go/dnswatcher/internal/portcheck"
-)
-
-func listenTCP(
-	t *testing.T,
-) (net.Listener, int) {
-	t.Helper()
-
-	lc := &net.ListenConfig{}
-
-	ln, err := lc.Listen(
-		context.Background(), "tcp", "127.0.0.1:0",
-	)
-	if err != nil {
-		t.Fatalf("failed to start listener: %v", err)
-	}
-
-	addr, ok := ln.Addr().(*net.TCPAddr)
-	if !ok {
-		t.Fatal("unexpected address type")
-	}
-
-	return ln, addr.Port
-}
-
-func TestCheckPortOpen(t *testing.T) {
-	t.Parallel()
-
-	ln, port := listenTCP(t)
-
-	defer func() { _ = ln.Close() }()
-
-	checker := portcheck.NewStandalone()
-
-	result, err := checker.CheckPort(
-		context.Background(), "127.0.0.1", port,
-	)
-	if err != nil {
-		t.Fatalf("unexpected error: %v", err)
-	}
-
-	if !result.Open {
-		t.Error("expected port to be open")
-	}
-
-	if result.Error != "" {
-		t.Errorf("expected no error, got: %s", result.Error)
-	}
-
-	if result.Latency <= 0 {
-		t.Error("expected positive latency")
-	}
-}
-
-func TestCheckPortClosed(t *testing.T) {
-	t.Parallel()
-
-	ln, port := listenTCP(t)
-	_ = ln.Close()
-
-	checker := portcheck.NewStandalone()
-
-	result, err := checker.CheckPort(
-		context.Background(), "127.0.0.1", port,
-	)
-	if err != nil {
-		t.Fatalf("unexpected error: %v", err)
-	}
-
-	if result.Open {
-		t.Error("expected port to be closed")
-	}
-
-	if result.Error == "" {
-		t.Error("expected error message for closed port")
-	}
-}
-
-func TestCheckPortContextCanceled(t *testing.T) {
-	t.Parallel()
-
-	ctx, cancel := context.WithCancel(context.Background())
-	cancel()
-
-	checker := portcheck.NewStandalone()
-
-	result, err := checker.CheckPort(ctx, "127.0.0.1", 1)
-	if err != nil {
-		t.Fatalf("unexpected error: %v", err)
-	}
-
-	if result.Open {
-		t.Error("expected port to not be open")
-	}
-}
-
-func TestCheckPortsMultiple(t *testing.T) {
-	t.Parallel()
-
-	ln, openPort := listenTCP(t)
-
-	defer func() { _ = ln.Close() }()
-
-	ln2, closedPort := listenTCP(t)
-	_ = ln2.Close()
-
-	checker := portcheck.NewStandalone()
-
-	results, err := checker.CheckPorts(
-		context.Background(),
-		"127.0.0.1",
-		[]int{openPort, closedPort},
-	)
-	if err != nil {
-		t.Fatalf("unexpected error: %v", err)
-	}
-
-	if len(results) != 2 {
-		t.Fatalf(
-			"expected 2 results, got %d", len(results),
-		)
-	}
-
-	if !results[openPort].Open {
-		t.Error("expected open port to be open")
-	}
-
-	if results[closedPort].Open {
-		t.Error("expected closed port to be closed")
-	}
-}
-
-func TestCheckPortLatencyReasonable(t *testing.T) {
-	t.Parallel()
-
-	ln, port := listenTCP(t)
-
-	defer func() { _ = ln.Close() }()
-
-	checker := portcheck.NewStandalone()
-
-	result, err := checker.CheckPort(
-		context.Background(), "127.0.0.1", port,
-	)
-	if err != nil {
-		t.Fatalf("unexpected error: %v", err)
-	}
-
-	if result.Latency > time.Second {
-		t.Errorf(
-			"latency too high for localhost: %v",
-			result.Latency,
-		)
-	}
-}