enhancement: Added the ability to configure a list of domains and only send mail to addresses in those domains

README.md

@@ -21,6 +21,18 @@ make docker
 make docker-run
 ```
 
+### Configuration
+A number of environment variables are available to configure the service at runtime:
+| Env var name | Functionality | Default |
+|--------------|---------------|---------|
+| SERVICE_PORT                      | The local port the application will bind to | 80 |
+| SENDGRID_API_KEY                  | The API Key for sendgrid | |
+| SLACK_API_KEY                     | The API Token for Slack | |
+| GRACEFUL_SHUTDOWN_TIMEOUT_SECONDS | The number of seconds the application will continue servicing in-flight requests before the application stops after it receives an interrupt signal | 10 |
+| STRUCTURED_LOGGING                | If enabled, logs will be in JSON format, and only above INFO level | false |
+| ALLOW_EMAIL_TO_DOMAINS            | A comma separated list of domains. Only addresses in this list can have email sent to them. If empty, disable this "sandboxing" functionality. | |
+
+
 ### Releasing a new version on GitHub and Brew
 
 We are using a tool called `goreleaser` which you can get from brew if you're on MacOS:

charts/zero-notifcation-service/Chart.yaml

@@ -15,9 +15,9 @@ type: application
 # This is the chart version. This version number should be incremented each time you make changes
 # to the chart and its templates, including the app version.
 # Versions are expected to follow Semantic Versioning (https://semver.org/)
-version: 0.0.5
+version: 0.0.6
 
 # This is the version number of the application being deployed. This version number should be
 # incremented each time you make changes to the application. Versions are not expected to
 # follow Semantic Versioning. They should reflect the version the application is using.
-appVersion: 0.0.5
+appVersion: 0.0.9

charts/zero-notifcation-service/templates/configmap.yaml

@@ -6,3 +6,4 @@ data:
     SERVICE_PORT: "{{ .Values.service.port }}"
     GRACEFUL_SHUTDOWN_TIMEOUT_SECONDS: "{{ .Values.application.gracefulShutdownTimeout }}"
     STRUCTURED_LOGGING: "{{ .Values.application.structuredLogging }}"
+    ALLOW_EMAIL_TO_DOMAINS: "{{ .Values.application.allowEmailToDomains }}"

charts/zero-notifcation-service/values.yaml

@@ -76,9 +76,11 @@ affinity: {}
 
 
 # Application Config
+# See project readme for more information about config options
 
 application:
   sendgridApiKey:
   slackApiKey:
   gracefulShutdownTimeout: 10
   structuredLogging: true
+  allowEmailToDomains:

internal/config/config.go

@@ -14,6 +14,7 @@ type Config struct {
 	GracefulShutdownTimeout time.Duration
 	StructuredLogging       bool
 	DebugDumpRequests       bool
+	AllowEmailToDomains     []string
 }
 
 var config *Config
@@ -26,6 +27,7 @@ const (
 	GracefulShutdownTimeout
 	StructuredLogging
 	DebugDumpRequests
+	AllowEmailToDomains
 )
 
 // GetConfig returns a pointer to the singleton Config object
@@ -55,13 +57,17 @@ func loadConfig() *Config {
 	viper.SetDefault(DebugDumpRequests, "false")
 	viper.BindEnv(DebugDumpRequests, "DEBUG_DUMP_REQUESTS")
 
+	viper.SetDefault(AllowEmailToDomains, []string{})
+	viper.BindEnv(AllowEmailToDomains, "ALLOW_EMAIL_TO_DOMAINS")
+
 	config := Config{
 		Port:                    viper.GetInt(Port),
 		SendgridAPIKey:          viper.GetString(SendgridAPIKey),
 		SlackAPIKey:             viper.GetString(SlackAPIKey),
 		GracefulShutdownTimeout: viper.GetDuration(GracefulShutdownTimeout),
 		StructuredLogging:       viper.GetBool(StructuredLogging),
 		DebugDumpRequests:       viper.GetBool(DebugDumpRequests),
+		AllowEmailToDomains:     viper.GetStringSlice(AllowEmailToDomains),
 	}
 
 	return &config

internal/mail/mail.go

@@ -1,6 +1,8 @@
 package mail
 
 import (
+	"fmt"
+	"strings"
 	"sync"
 
 	"github.com/commitdev/zero-notification-service/internal/server"
@@ -81,3 +83,24 @@ func convertAddresses(addresses []server.EmailRecipient) []*sendgridMail.Email {
 	}
 	return returnAddresses
 }
+
+// RemoveInvalidRecipients accepts a list of recipients and removes the ones with domains not in the allowed list
+func RemoveInvalidRecipients(recipients []server.EmailRecipient, allowedDomains []string) []server.EmailRecipient {
+	valid := []server.EmailRecipient{}
+	for _, recipient := range recipients {
+		if addressInAllowedDomain(recipient.Address, allowedDomains) {
+			valid = append(valid, recipient)
+		}
+	}
+	return valid
+}
+
+// addressInAllowedDomain checks if a single email address is in a list of domains
+func addressInAllowedDomain(address string, domains []string) bool {
+	for _, domain := range domains {
+		if strings.HasSuffix(address, fmt.Sprintf("@%s", domain)) {
+			return true
+		}
+	}
+	return false
+}

internal/mail/mail_test.go

@@ -25,16 +25,7 @@ func (cl *FakeClient) Send(email *sendgridMail.SGMailV3) (*rest.Response, error)
 }
 
 func TestSendBulkMail(t *testing.T) {
-	var toList []server.EmailRecipient
-	// Create a random number of mails
-	rand.Seed(time.Now().UnixNano())
-	sendCount := rand.Intn(5) + 2
-	for i := 0; i < sendCount; i++ {
-		toList = append(toList, server.EmailRecipient{
-			Name:    fmt.Sprintf("Test Recipient %d", i),
-			Address: fmt.Sprintf("address%d@domain.com", i),
-		})
-	}
+	toList := createRandomRecipients(2, 5)
 	cc := make([]server.EmailRecipient, 0)
 	bcc := make([]server.EmailRecipient, 0)
 	from := server.EmailSender{Name: "Test User", Address: "address@domain.com"}
@@ -52,8 +43,37 @@ func TestSendBulkMail(t *testing.T) {
 		returnedCount++
 	}
 
-	assert.Equal(t, sendCount, returnedCount, "Response count should match requests sent")
+	assert.Equal(t, len(toList), returnedCount, "Response count should match requests sent")
 
 	// Check that the send function was called
-	client.AssertNumberOfCalls(t, "Send", sendCount)
+	client.AssertNumberOfCalls(t, "Send", len(toList))
+}
+
+func TestRemoveInvalidRecipients(t *testing.T) {
+	toList := createRandomRecipients(2, 5)
+
+	originalSize := len(toList)
+
+	toList[0].Address = "address@commit.dev"
+
+	alteredList := mail.RemoveInvalidRecipients(toList, []string{"commit.dev", "domain.com"})
+	assert.Equal(t, len(alteredList), originalSize, "All addresses should remain in the list")
+
+	alteredList = mail.RemoveInvalidRecipients(toList, []string{"commit.dev"})
+	assert.Equal(t, len(alteredList), 1, "1 address should remain in the list")
+}
+
+// createRandomRecipients creates a random list of recipients
+func createRandomRecipients(min int, randCount int) []server.EmailRecipient {
+	var toList []server.EmailRecipient
+	// Create a random number of mails
+	rand.Seed(time.Now().UnixNano())
+	sendCount := rand.Intn(randCount) + min
+	for i := 0; i < sendCount; i++ {
+		toList = append(toList, server.EmailRecipient{
+			Name:    fmt.Sprintf("Test Recipient %d", i),
+			Address: fmt.Sprintf("address%d@domain.com", i),
+		})
+	}
+	return toList
 }

internal/service/api_email_service.go

@@ -26,6 +26,20 @@ func NewEmailApiService(c *config.Config) server.EmailApiServicer {
 
 // SendEmail - Send an email
 func (s *EmailApiService) SendEmail(ctx context.Context, sendMailRequest server.SendMailRequest) (server.ImplResponse, error) {
+
+	// Check if there are valid recipients who are not in the restriction list
+	if len(s.config.AllowEmailToDomains) > 0 {
+		originalAddresses := sendMailRequest.ToAddresses
+		sendMailRequest.ToAddresses = mail.RemoveInvalidRecipients(sendMailRequest.ToAddresses, s.config.AllowEmailToDomains)
+		// If there are none, return with a 200 but don't send anything
+		if len(sendMailRequest.ToAddresses) == 0 {
+			zap.S().Infow("No valid Recipients for send", zap.Any("original_addresses", originalAddresses))
+			return server.Response(http.StatusOK, server.SendMailResponse{TrackingId: "No valid recipients"}), nil
+		}
+	}
+	sendMailRequest.CcAddresses = mail.RemoveInvalidRecipients(sendMailRequest.CcAddresses, s.config.AllowEmailToDomains)
+	sendMailRequest.BccAddresses = mail.RemoveInvalidRecipients(sendMailRequest.BccAddresses, s.config.AllowEmailToDomains)
+
 	client := sendgrid.NewSendClient(s.config.SendgridAPIKey)
 	response, err := mail.SendIndividualMail(sendMailRequest.ToAddresses, sendMailRequest.FromAddress, sendMailRequest.CcAddresses, sendMailRequest.BccAddresses, sendMailRequest.Message, client)
 
@@ -45,6 +59,20 @@ func (s *EmailApiService) SendEmail(ctx context.Context, sendMailRequest server.
 
 // SendBulk - Send a batch of emails to many users with the same content. Note that it is possible for only a subset of these to fail.
 func (s *EmailApiService) SendBulk(ctx context.Context, sendBulkMailRequest server.SendBulkMailRequest) (server.ImplResponse, error) {
+	// Check if there are valid recipients who are not in the restriction list
+	if len(s.config.AllowEmailToDomains) > 0 {
+		originalAddresses := sendBulkMailRequest.ToAddresses
+		sendBulkMailRequest.ToAddresses = mail.RemoveInvalidRecipients(sendBulkMailRequest.ToAddresses, s.config.AllowEmailToDomains)
+
+		// If there are none, return with a 200 but don't send anything
+		if len(sendBulkMailRequest.ToAddresses) == 0 {
+			zap.S().Infow("No valid Recipients for bulk send", zap.Any("original_addresses", originalAddresses))
+			return server.Response(http.StatusOK, server.SendMailResponse{TrackingId: "No valid recipients"}), nil
+		}
+	}
+	sendBulkMailRequest.CcAddresses = mail.RemoveInvalidRecipients(sendBulkMailRequest.CcAddresses, s.config.AllowEmailToDomains)
+	sendBulkMailRequest.BccAddresses = mail.RemoveInvalidRecipients(sendBulkMailRequest.BccAddresses, s.config.AllowEmailToDomains)
+
 	client := sendgrid.NewSendClient(s.config.SendgridAPIKey)
 
 	responseChannel := make(chan mail.BulkSendAttempt)