1 files changed, 133 insertions, 0 deletions
diff --git a/services/httpservice/client.go b/services/httpservice/client.go
new file mode 100644
index 000000000..268f63b24
--- /dev/null
+++ b/services/httpservice/client.go
@@ -0,0 +1,133 @@
+// Copyright (c) 2017-present Mattermost, Inc. All Rights Reserved.
+// See License.txt for license information.
+
+package httpservice
+
+import (
+	"context"
+	"crypto/tls"
+	"errors"
+	"net"
+	"net/http"
+	"time"
+)
+
+const (
+	connectTimeout = 3 * time.Second
+	requestTimeout = 30 * time.Second
+)
+
+var reservedIPRanges []*net.IPNet
+
+func IsReservedIP(ip net.IP) bool {
+	for _, ipRange := range reservedIPRanges {
+		if ipRange.Contains(ip) {
+			return true
+		}
+	}
+	return false
+}
+
+func init() {
+	for _, cidr := range []string{
+		// See https://tools.ietf.org/html/rfc6890
+		"0.0.0.0/8",      // This host on this network
+		"10.0.0.0/8",     // Private-Use
+		"127.0.0.0/8",    // Loopback
+		"169.254.0.0/16", // Link Local
+		"172.16.0.0/12",  // Private-Use Networks
+		"192.168.0.0/16", // Private-Use Networks
+		"::/128",         // Unspecified Address
+		"::1/128",        // Loopback Address
+		"fc00::/7",       // Unique-Local
+		"fe80::/10",      // Linked-Scoped Unicast
+	} {
+		_, parsed, err := net.ParseCIDR(cidr)
+		if err != nil {
+			panic(err)
+		}
+		reservedIPRanges = append(reservedIPRanges, parsed)
+	}
+}
+
+type DialContextFunction func(ctx context.Context, network, addr string) (net.Conn, error)
+
+var AddressForbidden error = errors.New("address forbidden, you may need to set AllowedUntrustedInternalConnections to allow an integration access to your internal network")
+
+func dialContextFilter(dial DialContextFunction, allowHost func(host string) bool, allowIP func(ip net.IP) bool) DialContextFunction {
+	return func(ctx context.Context, network, addr string) (net.Conn, error) {
+		host, port, err := net.SplitHostPort(addr)
+		if err != nil {
+			return nil, err
+		}
+
+		if allowHost != nil && allowHost(host) {
+			return dial(ctx, network, addr)
+		}
+
+		ips, err := net.LookupIP(host)
+		if err != nil {
+			return nil, err
+		}
+
+		var firstErr error
+		for _, ip := range ips {
+			select {
+			case <-ctx.Done():
+				return nil, ctx.Err()
+			default:
+			}
+
+			if allowIP == nil || !allowIP(ip) {
+				continue
+			}
+
+			conn, err := dial(ctx, network, net.JoinHostPort(ip.String(), port))
+			if err == nil {
+				return conn, nil
+			}
+			if firstErr == nil {
+				firstErr = err
+			}
+		}
+		if firstErr == nil {
+			return nil, AddressForbidden
+		}
+		return nil, firstErr
+	}
+}
+
+// NewHTTPClient returns a variation the default implementation of Client.
+// It uses a Transport with the same settings as the default Transport
+// but with the following modifications:
+// - shorter timeout for dial and TLS handshake (defined as constant
+//   "connectTimeout")
+// - timeout for the end-to-end request (defined as constant
+//   "requestTimeout")
+func NewHTTPClient(enableInsecureConnections bool, allowHost func(host string) bool, allowIP func(ip net.IP) bool) *http.Client {
+	dialContext := (&net.Dialer{
+		Timeout:   connectTimeout,
+		KeepAlive: 30 * time.Second,
+	}).DialContext
+
+	if allowHost != nil || allowIP != nil {
+		dialContext = dialContextFilter(dialContext, allowHost, allowIP)
+	}
+
+	client := &http.Client{
+		Transport: &http.Transport{
+			Proxy:                 http.ProxyFromEnvironment,
+			DialContext:           dialContext,
+			MaxIdleConns:          100,
+			IdleConnTimeout:       90 * time.Second,
+			TLSHandshakeTimeout:   connectTimeout,
+			ExpectContinueTimeout: 1 * time.Second,
+			TLSClientConfig: &tls.Config{
+				InsecureSkipVerify: enableInsecureConnections,
+			},
+		},
+		Timeout: requestTimeout,
+	}
+
+	return client
+}