@@ -56,7 +56,7 @@ func (config *Config) InstallFlags() {

 	flag.StringVar(&config.BridgeIP, []string{"#bip", "-bip"}, "", "Use this CIDR notation address for the network bridge's IP, not compatible with -b")

 	flag.StringVar(&config.BridgeIface, []string{"b", "-bridge"}, "", "Attach containers to a pre-existing network bridge\nuse 'none' to disable container networking")

 	flag.StringVar(&config.FixedCIDR, []string{"-fixed-cidr"}, "", "IPv4 subnet for fixed IPs (ex: 10.20.0.0/16)\nthis subnet must be nested in the bridge subnet (which is defined by -b or --bip)")

-	opts.ListVar(&config.InsecureRegistries, []string{"-insecure-registry"}, "Enable insecure communication with specified registries (no certificate verification for HTTPS and enable HTTP fallback)")

+	opts.ListVar(&config.InsecureRegistries, []string{"-insecure-registry"}, "Enable insecure communication with specified registries (no certificate verification for HTTPS and enable HTTP fallback) (e.g., localhost:5000 or 10.20.0.0/16)")

 	flag.BoolVar(&config.InterContainerCommunication, []string{"#icc", "-icc"}, true, "Enable inter-container communication")

 	flag.StringVar(&config.GraphDriver, []string{"s", "-storage-driver"}, "", "Force the Docker runtime to use a specific storage driver")

 	flag.StringVar(&config.ExecDriver, []string{"e", "-exec-driver"}, "native", "Force the Docker runtime to use a specific exec driver")

@@ -68,6 +68,14 @@ func (config *Config) InstallFlags() {

 	opts.IPListVar(&config.Dns, []string{"#dns", "-dns"}, "Force Docker to use specific DNS servers")

 	opts.DnsSearchListVar(&config.DnsSearch, []string{"-dns-search"}, "Force Docker to use specific DNS search domains")

 	opts.MirrorListVar(&config.Mirrors, []string{"-registry-mirror"}, "Specify a preferred Docker registry mirror")

+

+	// Localhost is by default considered as an insecure registry

+	// This is a stop-gap for people who are running a private registry on localhost (especially on Boot2docker).

+	//

+	// TODO: should we deprecate this once it is easier for people to set up a TLS registry or change

+	// daemon flags on boot2docker?

+	// If so, do not forget to check the TODO in TestIsSecure

+	config.InsecureRegistries = append(config.InsecureRegistries, "127.0.0.0/8")

 }

 func getDefaultNetworkMtu() int {

@@ -70,7 +70,7 @@ expect an integer, and they can only be specified once.

       -g, --graph="/var/lib/docker"              Path to use as the root of the Docker runtime

       -H, --host=[]                              The socket(s) to bind to in daemon mode or connect to in client mode, specified using one or more tcp://host:port, unix:///path/to/socket, fd://* or fd://socketfd.

       --icc=true                                 Enable inter-container communication

-      --insecure-registry=[]                     Enable insecure communication with specified registries (no certificate verification for HTTPS and enable HTTP fallback)

+      --insecure-registry=[]                     Enable insecure communication with specified registries (no certificate verification for HTTPS and enable HTTP fallback) (ex: localhost:5000 or 10.20.0.0/16)

       --ip=0.0.0.0                               Default IP address to use when binding container ports

       --ip-forward=true                          Enable net.ipv4.ip_forward

       --ip-masq=true                             Enable IP masquerading for bridge's IP range

@@ -12,6 +12,9 @@ import (

 	log "github.com/Sirupsen/logrus"

 )

+// for mocking in unit tests

+var lookupIP = net.LookupIP

+

 // scans string for api version in the URL path. returns the trimmed hostname, if version found, string and API version.

 func scanForAPIVersion(hostname string) (string, APIVersion) {

 	var (

@@ -79,7 +82,10 @@ func newEndpoint(hostname string, insecureRegistries []string) (*Endpoint, error

 	if err != nil {

 		return nil, err

 	}

-	endpoint.secure = isSecure(endpoint.URL.Host, insecureRegistries)

+	endpoint.secure, err = isSecure(endpoint.URL.Host, insecureRegistries)

+	if err != nil {

+		return nil, err

+	}

 	return &endpoint, nil

 }

@@ -152,30 +158,56 @@ func (e Endpoint) Ping() (RegistryInfo, error) {

 // isSecure returns false if the provided hostname is part of the list of insecure registries.

 // Insecure registries accept HTTP and/or accept HTTPS with certificates from unknown CAs.

-func isSecure(hostname string, insecureRegistries []string) bool {

+//

+// The list of insecure registries can contain an element with CIDR notation to specify a whole subnet.

+// If the subnet contains one of the IPs of the registry specified by hostname, the latter is considered

+// insecure.

+//

+// hostname should be a URL.Host (`host:port` or `host`)

+func isSecure(hostname string, insecureRegistries []string) (bool, error) {

 	if hostname == IndexServerURL.Host {

-		return true

+		return true, nil

 	}

 	host, _, err := net.SplitHostPort(hostname)

-

 	if err != nil {

+		// assume hostname is of the form `host` without the port and go on.

 		host = hostname

 	}

-

-	if host == "127.0.0.1" || host == "localhost" {

-		return false

-	}

-

-	if len(insecureRegistries) == 0 {

-		return true

-	}

-

-	for _, h := range insecureRegistries {

-		if hostname == h {

-			return false

+	addrs, err := lookupIP(host)

+	if err != nil {

+		ip := net.ParseIP(host)

+		if ip == nil {

+			// if resolving `host` fails, error out, since host is to be net.Dial-ed anyway

+			return true, fmt.Errorf("issecure: could not resolve %q: %v", host, err)

+		}

+		addrs = []net.IP{ip}

+	}

+	if len(addrs) == 0 {

+		return true, fmt.Errorf("issecure: could not resolve %q", host)

+	}

+

+	for _, addr := range addrs {

+		for _, r := range insecureRegistries {

+			// hostname matches insecure registry

+			if hostname == r {

+				return false, nil

+			}

+

+			// now assume a CIDR was passed to --insecure-registry

+			_, ipnet, err := net.ParseCIDR(r)

+			if err != nil {

+				// if could not parse it as a CIDR, even after removing

+				// assume it's not a CIDR and go on with the next candidate

+				continue

+			}

+

+			// check if the addr falls in the subnet

+			if ipnet.Contains(addr) {

+				return false, nil

+			}

 		}

 	}

-	return true

+	return true, nil

 }

@@ -2,9 +2,11 @@ package registry

 import (

 	"encoding/json"

+	"errors"

 	"fmt"

 	"io"

 	"io/ioutil"

+	"net"

 	"net/http"

 	"net/http/httptest"

 	"net/url"

@@ -80,6 +82,11 @@ var (

 			"latest": "42d718c941f5c532ac049bf0b0ab53f0062f09a03afd4aa4a02c098e46032b9d",

 		},

 	}

+	mockHosts = map[string][]net.IP{

+		"":            {net.ParseIP("0.0.0.0")},

+		"localhost":   {net.ParseIP("127.0.0.1"), net.ParseIP("::1")},

+		"example.com": {net.ParseIP("42.42.42.42")},

+	}

 )

 func init() {

@@ -106,6 +113,25 @@ func init() {

 		panic(err)

 	}

 	insecureRegistries = []string{URL.Host}

+

+	// override net.LookupIP

+	lookupIP = func(host string) ([]net.IP, error) {

+		if host == "127.0.0.1" {

+			// I believe in future Go versions this will fail, so let's fix it later

+			return net.LookupIP(host)

+		}

+		for h, addrs := range mockHosts {

+			if host == h {

+				return addrs, nil

+			}

+			for _, addr := range addrs {

+				if addr.String() == host {

+					return []net.IP{addr}, nil

+				}

+			}

+		}

+		return nil, errors.New("lookup: no such host")

+	}

 }

 func handlerAccessLog(handler http.Handler) http.Handler {

@@ -333,19 +333,26 @@ func TestIsSecure(t *testing.T) {

 		{"localhost:5000", []string{"localhost:5000"}, false},

 		{"localhost", []string{"example.com"}, false},

 		{"127.0.0.1:5000", []string{"127.0.0.1:5000"}, false},

-		{"localhost", []string{}, false},

-		{"localhost:5000", []string{}, false},

-		{"127.0.0.1", []string{}, false},

+		{"localhost", nil, false},

+		{"localhost:5000", nil, false},

+		{"127.0.0.1", nil, false},

 		{"localhost", []string{"example.com"}, false},

 		{"127.0.0.1", []string{"example.com"}, false},

-		{"example.com", []string{}, true},

+		{"example.com", nil, true},

 		{"example.com", []string{"example.com"}, false},

 		{"127.0.0.1", []string{"example.com"}, false},

 		{"127.0.0.1:5000", []string{"example.com"}, false},

+		{"example.com:5000", []string{"42.42.0.0/16"}, false},

+		{"example.com", []string{"42.42.0.0/16"}, false},

+		{"example.com:5000", []string{"42.42.42.42/8"}, false},

+		{"127.0.0.1:5000", []string{"127.0.0.0/8"}, false},

+		{"42.42.42.42:5000", []string{"42.1.1.1/8"}, false},

 	}

 	for _, tt := range tests {

-		if sec := isSecure(tt.addr, tt.insecureRegistries); sec != tt.expected {

-			t.Errorf("isSecure failed for %q %v, expected %v got %v", tt.addr, tt.insecureRegistries, tt.expected, sec)

+		// TODO: remove this once we remove localhost insecure by default

+		insecureRegistries := append(tt.insecureRegistries, "127.0.0.0/8")

+		if sec, err := isSecure(tt.addr, insecureRegistries); err != nil || sec != tt.expected {

+			t.Fatalf("isSecure failed for %q %v, expected %v got %v. Error: %v", tt.addr, insecureRegistries, tt.expected, sec, err)

 		}

 	}

 }