RA/CA: Make MaxNames field consistent and supply default

cmd/boulder-ca/main.go

@@ -49,8 +49,12 @@ type Config struct {
 		// What digits we should prepend to serials after randomly generating them.
 		SerialPrefix int `validate:"required,min=1,max=127"`
 
-		// The maximum number of subjectAltNames in a single certificate
-		MaxNames int `validate:"required,min=1,max=100"`
+		// MaxNames is the maximum number of subjectAltNames in a single cert.
+		// The value supplied SHOULD be greater than 0 and no more than 100,
+		// defaults to 100. These limits are per section 7.1 of our combined
+		// CP/CPS, under "DV-SSL Subscriber Certificate". The value must match
+		// the RA and WFE configurations.
+		MaxNames int `validate:"min=0,max=100"`
 
 		// LifespanOCSP is how long OCSP responses are valid for. Per the BRs,
 		// Section 4.9.10, it MUST NOT be more than 10 days. Default 96h.
@@ -162,8 +166,10 @@ func main() {
 		c.CA.DebugAddr = *debugAddr
 	}
 
-	if c.CA.MaxNames == 0 {
-		cmd.Fail("Error in CA config: MaxNames must not be 0")
+	maxNames := c.CA.MaxNames
+	if maxNames == 0 {
+		// Use default.
+		maxNames = 100
 	}
 
 	if c.CA.LifespanOCSP.Duration == 0 {
@@ -276,7 +282,7 @@ func main() {
 			c.CA.Expiry.Duration,
 			c.CA.Backdate.Duration,
 			c.CA.SerialPrefix,
-			c.CA.MaxNames,
+			maxNames,
 			kp,
 			logger,
 			scope,

cmd/boulder-ra/main.go

@@ -42,7 +42,12 @@ type Config struct {
 		PublisherService    *cmd.GRPCClientConfig
 		AkamaiPurgerService *cmd.GRPCClientConfig
 
-		MaxNames int `validate:"required,min=1"`
+		// MaxNames is the maximum number of subjectAltNames in a single cert.
+		// The value supplied SHOULD be greater than 0 and no more than 100,
+		// defaults to 100. These limits are per section 7.1 of our combined
+		// CP/CPS, under "DV-SSL Subscriber Certificate". The value must match
+		// the CA and WFE configurations.
+		MaxNames int `validate:"min=0,max=100"`
 
 		// AuthorizationLifetimeDays defines how long authorizations will be
 		// considered valid for. Given a value of 300 days when used with a 90-day
@@ -223,8 +228,10 @@ func main() {
 	kp, err := sagoodkey.NewKeyPolicy(&c.RA.GoodKey, sac.KeyBlocked)
 	cmd.FailOnError(err, "Unable to create key policy")
 
-	if c.RA.MaxNames == 0 {
-		cmd.Fail("Error in RA config: MaxNames must not be 0")
+	maxNames := c.RA.MaxNames
+	if maxNames == 0 {
+		// Use default.
+		maxNames = 100
 	}
 
 	rai := ra.NewRegistrationAuthorityImpl(
@@ -233,7 +240,7 @@ func main() {
 		scope,
 		c.RA.MaxContactsPerRegistration,
 		kp,
-		c.RA.MaxNames,
+		maxNames,
 		authorizationLifetime,
 		pendingAuthorizationLifetime,
 		pubc,