feat: add ValidateEndpointURI

Adds ValidateEndpointURI, which ensures that endpoint URIs are valid
`url.URL`s and that they meet further usage qualifications, such as
square-bracket-closed IPv6 addresses and ports within a valid range.

Signed-off-by: Seán C McCord <ulexus@gmail.com>

net.go

@@ -10,10 +10,16 @@ import (
 	"fmt"
 	"io/ioutil"
 	"net"
+	"net/url"
 	"os"
+	"strconv"
 	"strings"
 )
 
+const minPortRange = 1
+
+const maxPortRange = 65535
+
 // IPAddrs finds and returns a list of non-loopback IP addresses of the
 // current machine.
 func IPAddrs() (ips []net.IP, err error) {
@@ -169,3 +175,43 @@ func IsIPv6(addrs ...net.IP) bool {
 
 	return false
 }
+
+// ValidateEndpointURI checks that an endpoint is valid.
+// This is a more strict check that merely `url.Parse`, in that it requires such things as properly-ranged numeric ports and bracket-enclosed IPv6 addresses.
+func ValidateEndpointURI(ep string) error {
+	u, err := url.Parse(ep)
+	if err != nil {
+		return err
+	}
+
+	if strings.Count(u.Host, ":") > 2 {
+		// More than two colon indicates that we must have an IPv6 address.
+		// If we have an IPv6 address, it *must* be enclosed by brackets.
+		if strings.Count(u.Host, "[") < 1 || strings.Count(u.Host, "]") < 1 {
+			return fmt.Errorf("IPv6 addresses MUST be enclosed by square brackets")
+		}
+	}
+
+	if u.Hostname() == "" {
+		return fmt.Errorf("hostname must not be blank")
+	}
+
+	if u.Port() != "" {
+		return validatePortNumber(u.Port())
+	}
+
+	return nil
+}
+
+func validatePortNumber(p string) error {
+	portInt, err := strconv.Atoi(p)
+	if err != nil {
+		return fmt.Errorf("port number must be numeric")
+	}
+
+	if portInt < minPortRange || portInt > maxPortRange {
+		return fmt.Errorf("port number must be between %d and %d", minPortRange, maxPortRange)
+	}
+
+	return nil
+}

net_test.go

@@ -113,3 +113,35 @@ func TestNthIPInNetwork(t *testing.T) {
 		})
 	}
 }
+
+func TestValidateEndpointURI(t *testing.T) {
+	goodTests := []string{
+		"http://216.22.102.222",
+		"https://[2001:db8:abef::ffff]:65000",
+		"https://[2001:db8::ffff]",
+		"http://goethe.de",
+	}
+
+	for _, testEP := range goodTests {
+		assert.Nil(t, talosnet.ValidateEndpointURI(testEP), "URI should be valid")
+	}
+
+	badTests := []string{
+		"12.34.56.89:1234",                 // ipv4:port, no protocol
+		"[2001:db8::1]:5040",               // ipv6:port, no protocol
+		"hostA:65301",                      // host:port, no protocol
+		"my.long.domain.name:10101",        // dns:port, no protocol
+		"192.168.2.1",                      // IP without port
+		"[2001:db8::1]",                    // IPv6 without port
+		"kubernetes.io",                    // hostname without port
+		"2001:db8:123:445:204",             // IPv6 without brackets
+		"http://2001:db8:101:101::1:50000", // IPv6 URL without brackets
+		"http://192.168.1.1:1020304",       // Port out of range
+		"http://192.168.1.1:0",             // 0 Port
+		"http://192.168.1.1:-1000",         // Negative Port
+	}
+
+	for _, testEP := range badTests {
+		assert.NotNil(t, talosnet.ValidateEndpointURI(testEP), "URI should be invalid")
+	}
+}