CVE-2020-24710 (Go, published 2020-10-28T20:15Z)
Description: value: Gophish before 0.11.0 allows SSRF attacks.
Severity: MEDIUM (CVSS v3 base score: 5.3)
Weakness: CWE-918 \u2014 Server-Side Request Forgery (SSRF)
The web server receives a URL or similar request from an upstream component and retrieves the contents of this URL, but it does not sufficiently ensure that the request is being sent to the expected destination.
Repository: https://github.com/gophish/gophish
Files changed:
config/config.go
controllers/api/import.go
controllers/api/import_test.go
dialer/dialer.go
dialer/dialer_test.go
go.mod
go.sum
gophish.go
imap/imap.go
models/smtp.go
models/smtp_test.go
webhook/webhook.go
Commit message: Implement SSRF Mitigations (#1940)

Initial commit of SSRF mitigations.

This fixes #1908 by creating a *net.Dialer which restricts outbound connections to only allowed IP ranges. This implementation is based on the blog post at https://www.agwa.name/blog/post/preventing_server_side_request_forgery_in_golang

To keep things backwards compatible, by default we'll only block connections to 169.254.169.254, the link-local IP address commonly used in cloud environments to retrieve metadata about the running instance. For other internal addresses (e.g. localhost or RFC 1918 addresses), it's assumed that those are available to Gophish.

To support more secure environments, we introduce the `allowed_internal_hosts` configuration option where an admin can set one or more IP ranges in CIDR format. If addresses are specified here, then all internal connections will be blocked except to these hosts.

There are various bits about this approach I don't really like. For example, since various packages all need this functionality, I had to make the RestrictedDialer a global singleton rather than a dependency off of, say, the admin server. Additionally, since webhooks are implemented via a singleton, I had to introduce a new function, `SetTransport`.

Finally, I had to make an update in the gomail package to support a custom net.Dialer.

Vulnerable code:
	ListenURL string `json:"listen_url"`
	UseTLS    bool   `json:"use_tls"`
	CertPath  string `json:"cert_path"`
	KeyPath   string `json:"key_path"`
	CSRFKey   string `json:"csrf_key"`
	github.com/gophish/gomail v0.0.0-20180314010319-cf7e1a5479be
	gopkg.in/alexcesaro/quotedprintable.v3 v3.0.0-20150716171945-2caba252f4dc // indirect
	gopkg.in/gomail.v2 v2.0.0-20160411212932-81ebce5c23df // indirect
github.com/gophish/gomail v0.0.0-20180314010319-cf7e1a5479be h1:VTe1cdyqSi/wLowKNz/shz6E0G+9/XzldZbyAmt+0Yw=
github.com/gophish/gomail v0.0.0-20180314010319-cf7e1a5479be/go.mod h1:MpSuP7kw+gRy2z+4gIFZeF3DwhhdQhEXwRmPVQYD9ig=
gopkg.in/gomail.v2 v2.0.0-20160411212932-81ebce5c23df h1:n7WqCuqOuCbNr617RXOY0AWRXxgwEyPp2z+p0+hgMuE=
gopkg.in/gomail.v2 v2.0.0-20160411212932-81ebce5c23df/go.mod h1:LRQQ+SO6ZHR7tOkpBDuZnXENFzX8qRjMDMyPD6BRkCw=
		imapClient, err = client.DialTLS(mbox.Host, config)
		imapClient, err = client.Dial(mbox.Host)
	d := gomail.NewDialer(host, port, s.Username, s.Password)

Fixed code:
	ListenURL            string   `json:"listen_url"`
	UseTLS               bool     `json:"use_tls"`
	CertPath             string   `json:"cert_path"`
	KeyPath              string   `json:"key_path"`
	CSRFKey              string   `json:"csrf_key"`
	AllowedInternalHosts []string `json:"allowed_internal_hosts"`
	"github.com/gophish/gophish/dialer"
	restrictedDialer := dialer.Dialer()
		DialContext: restrictedDialer.DialContext,
package api

import (
	"bytes"
	"encoding/json"
	"fmt"
	"net/http"
	"net/http/httptest"
	"strings"
	"testing"

	"github.com/gophish/gophish/dialer"
	"github.com/gophish/gophish/models"
)

func makeImportRequest(ctx *testContext, allowedHosts []string, url string) *httptest.ResponseRecorder {
	orig := dialer.DefaultDialer.AllowedHosts()
	dialer.SetAllowedHosts(allowedHosts)
	req := httptest.NewRequest(http.MethodPost, "/api/import/site",
		bytes.NewBuffer([]byte(fmt.Sprintf(`
			{
				"url" : "%s"
			}
		`, url))))
	req.Header.Set("Content-Type", "application/json")
	response := httptest.NewRecorder()
	ctx.apiServer.ImportSite(response, req)
	dialer.SetAllowedHosts(orig)
	return response
}

func TestDefaultDeniedImport(t *testing.T) {
	ctx := setupTest(t)
	metadataURL := "http://169.254.169.254/latest/meta-data/"
	response := makeImportRequest(ctx, []string{}, metadataURL)
	expectedCode := http.StatusBadRequest
	if response.Code != expectedCode {
		t.Fatalf("incorrect status code received. expected %d got %d", expectedCode, response.Code)
	}
	got := &models.Response{}
	err := json.NewDecoder(response.Body).Decode(got)
	if err != nil {
		t.Fatalf("error decoding body: %v", err)
	}
	if !strings.Contains(got.Message, "upstream connection denied") {
		t.Fatalf("incorrect response error provided: %s", got.Message)
	}
}

func TestDefaultAllowedImport(t *testing.T) {
	ctx := setupTest(t)
	h := "<html><head></head><body><img src=\"/test.png\"/></body></html>"
	ts := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		fmt.Fprintln(w, h)
	}))
	defer ts.Close()
	response := makeImportRequest(ctx, []string{}, ts.URL)
	expectedCode := http.StatusOK
	if response.Code != expectedCode {
		t.Fatalf("incorrect status code received. expected %d got %d", expectedCode, response.Code)
	}
}

func TestCustomDeniedImport(t *testing.T) {
	ctx := setupTest(t)
	h := "<html><head></head><body><img src=\"/test.png\"/></body></html>"
	ts := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		fmt.Fprintln(w, h)
	}))
	defer ts.Close()
	response := makeImportRequest(ctx, []string{"192.168.1.1"}, ts.URL)
	expectedCode := http.StatusBadRequest
	if response.Code != expectedCode {
		t.Fatalf("incorrect status code received. expected %d got %d", expectedCode, response.Code)
	}
	got := &models.Response{}
	err := json.NewDecoder(response.Body).Decode(got)
	if err != nil {
		t.Fatalf("error decoding body: %v", err)
	}
	if !strings.Contains(got.Message, "upstream connection denied") {
		t.Fatalf("incorrect response error provided: %s", got.Message)
	}
}
package dialer

import (
	"fmt"
	"net"
	"syscall"
	"time"
)

// RestrictedDialer is used to create a net.Dialer which restricts outbound
// connections to only allowlisted IP ranges.
type RestrictedDialer struct {
	allowedHosts []*net.IPNet
}

// DefaultDialer is a global instance of a RestrictedDialer
var DefaultDialer = &RestrictedDialer{}

// SetAllowedHosts sets the list of allowed hosts or IP ranges for the default
// dialer.
func SetAllowedHosts(allowed []string) {
	DefaultDialer.SetAllowedHosts(allowed)
}

// AllowedHosts returns the configured hosts that are allowed for the dialer.
func (d *RestrictedDialer) AllowedHosts() []string {
	ranges := []string{}
	for _, ipRange := range d.allowedHosts {
		ranges = append(ranges, ipRange.String())
	}
	return ranges
}

// SetAllowedHosts sets the list of allowed hosts or IP ranges for the dialer.
func (d *RestrictedDialer) SetAllowedHosts(allowed []string) error {
	for _, ipRange := range allowed {
		// For flexibility, try to parse as an IP first since this will
		// undoubtedly cause issues. If it works, then just append the
		// appropriate subnet mask, then parse as CIDR
		if singleIP := net.ParseIP(ipRange); singleIP != nil {
			if singleIP.To4() != nil {
				ipRange += "/32"
			} else {
				ipRange += "/128"
			}
		}
		_, parsed, err := net.ParseCIDR(ipRange)
		if err != nil {
			return fmt.Errorf("provided ip range is not valid CIDR notation: %v", err)
		}
		d.allowedHosts = append(d.allowedHosts, parsed)
	}
	return nil
}

// Dialer returns a net.Dialer that restricts outbound connections to only the
// addresses allowed by the DefaultDialer.
func Dialer() *net.Dialer {
	return DefaultDialer.Dialer()
}

// Dialer returns a net.Dialer that restricts outbound connections to only the
// allowed addresses over TCP.
//
// By default, since Gophish anticipates connections originating to hosts on
// the local network, we only deny access to the link-local addresses at
// 169.254.0.0/16.
//
// If hosts are provided, then Gophish blocks access to all local addresses
// except the ones provided.
//
// This implementation is based on the blog post by Andrew Ayer at
// https://www.agwa.name/blog/post/preventing_server_side_request_forgery_in_golang
func (d *RestrictedDialer) Dialer() *net.Dialer {
	return &net.Dialer{
		Timeout:   30 * time.Second,
		KeepAlive: 30 * time.Second,
		Control:   restrictedControl(d.allowedHosts),
	}
}

// defaultDeny represents the list of IP ranges that we want to block unless
// explicitly overriden.
var defaultDeny = []string{
	"169.254.0.0/16", // Link-local (used for VPS instance metadata)
}

// allInternal represents all internal hosts such that the only connections
// allowed are external ones.
var allInternal = []string{
	"0.0.0.0/8",
	"127.0.0.0/8",        // IPv4 loopback
	"10.0.0.0/8",         // RFC1918
	"100.64.0.0/10",      // CGNAT
	"172.16.0.0/12",      // RFC1918
	"169.254.0.0/16",     // RFC3927 link-local
	"192.88.99.0/24",     // IPv6 to IPv4 Relay
	"192.168.0.0/16",     // RFC1918
	"198.51.100.0/24",    // TEST-NET-2
	"203.0.113.0/24",     // TEST-NET-3
	"224.0.0.0/4",        // Multicast
	"240.0.0.0/4",        // Reserved
	"255.255.255.255/32", // Broadcast
	"::/0",               // Default route
	"::/128",             // Unspecified address
	"::1/128",            // IPv6 loopback
	"::ffff:0:0/96",      // IPv4 mapped addresses.
	"::ffff:0:0:0/96",    // IPv4 translated addresses.
	"fe80::/10",          // IPv6 link-local
	"fc00::/7",           // IPv6 unique local addr
}

type dialControl = func(network, address string, c syscall.RawConn) error

type restrictedDialer struct {
	*net.Dialer
	allowed []string
}

func restrictedControl(allowed []*net.IPNet) dialControl {
	return func(network string, address string, conn syscall.RawConn) error {
		if !(network == "tcp4" || network == "tcp6") {
			return fmt.Errorf("%s is not a safe network type", network)
		}

		host, _, err := net.SplitHostPort(address)
		if err != nil {
			return fmt.Errorf("%s is not a valid host/port pair: %s", address, err)
		}

		ip := net.ParseIP(host)
		if ip == nil {
			return fmt.Errorf("%s is not a valid IP address", host)
		}

		denyList := defaultDeny
		if len(allowed) > 0 {
			denyList = allInternal
		}

		for _, ipRange := range allowed {
			if ipRange.Contains(ip) {
				return nil
			}
		}

		for _, ipRange := range denyList {
			_, parsed, err := net.ParseCIDR(ipRange)
			if err != nil {
				return fmt.Errorf("error parsing denied range: %v", err)
			}
			if parsed.Contains(ip) {
				return fmt.Errorf("upstream connection denied to internal host")
			}
		}
		return nil
	}
}
package dialer

import (
	"fmt"
	"net"
	"strings"
	"syscall"
	"testing"
)

func TestDefaultDeny(t *testing.T) {
	control := restrictedControl([]*net.IPNet{})
	host := "169.254.169.254"
	expected := fmt.Errorf("upstream connection denied to internal host at %s", host)
	conn := new(syscall.RawConn)
	got := control("tcp4", fmt.Sprintf("%s:80", host), *conn)
	if !strings.Contains(got.Error(), "upstream connection denied") {
		t.Fatalf("unexpected error dialing denylisted host. expected %v got %v", expected, got)
	}
}

func TestDefaultAllow(t *testing.T) {
	control := restrictedControl([]*net.IPNet{})
	host := "1.1.1.1"
	conn := new(syscall.RawConn)
	got := control("tcp4", fmt.Sprintf("%s:80", host), *conn)
	if got != nil {
		t.Fatalf("error dialing allowed host. got %v", got)
	}
}

func TestCustomAllow(t *testing.T) {
	host := "127.0.0.1"
	_, ipRange, _ := net.ParseCIDR(fmt.Sprintf("%s/32", host))
	allowed := []*net.IPNet{ipRange}
	control := restrictedControl(allowed)
	conn := new(syscall.RawConn)
	got := control("tcp4", fmt.Sprintf("%s:80", host), *conn)
	if got != nil {
		t.Fatalf("error dialing allowed host. got %v", got)
	}
}

func TestCustomDeny(t *testing.T) {
	host := "127.0.0.1"
	_, ipRange, _ := net.ParseCIDR(fmt.Sprintf("%s/32", host))
	allowed := []*net.IPNet{ipRange}
	control := restrictedControl(allowed)
	conn := new(syscall.RawConn)
	expected := fmt.Errorf("upstream connection denied to internal host at %s", host)
	got := control("tcp4", "192.168.1.2:80", *conn)
	if !strings.Contains(got.Error(), "upstream connection denied") {
		t.Fatalf("unexpected error dialing denylisted host. expected %v got %v", expected, got)
	}
}

func TestSingleIP(t *testing.T) {
	orig := DefaultDialer.AllowedHosts()
	host := "127.0.0.1"
	DefaultDialer.SetAllowedHosts([]string{host})
	control := DefaultDialer.Dialer().Control
	conn := new(syscall.RawConn)
	expected := fmt.Errorf("upstream connection denied to internal host at %s", host)
	got := control("tcp4", "192.168.1.2:80", *conn)
	if !strings.Contains(got.Error(), "upstream connection denied") {
		t.Fatalf("unexpected error dialing denylisted host. expected %v got %v", expected, got)
	}

	host = "::1"
	DefaultDialer.SetAllowedHosts([]string{host})
	control = DefaultDialer.Dialer().Control
	conn = new(syscall.RawConn)
	expected = fmt.Errorf("upstream connection denied to internal host at %s", host)
	got = control("tcp4", "192.168.1.2:80", *conn)
	if !strings.Contains(got.Error(), "upstream connection denied") {
		t.Fatalf("unexpected error dialing denylisted host. expected %v got %v", expected, got)
	}

	// Test an allowed connection
	got = control("tcp4", fmt.Sprintf("[%s]:80", host), *conn)
	if got != nil {
		t.Fatalf("error dialing allowed host. got %v", got)
	}
	DefaultDialer.SetAllowedHosts(orig)
}
	github.com/gophish/gomail v0.0.0-20200818021916-1f6d0dfd512e
github.com/gophish/gomail v0.0.0-20200818021916-1f6d0dfd512e h1:URNpXdOxXAfuZ8wsr/DY27KTffVenKDjtNVAEwcR2Oo=
github.com/gophish/gomail v0.0.0-20200818021916-1f6d0dfd512e/go.mod h1:JGlHttcLdDp3F4g8bPHqqQnUUDuB3poB4zLXozQ0xCY=
	"net/http"
	"github.com/gophish/gophish/dialer"
	"github.com/gophish/gophish/webhook"
	// Configure our various upstream clients to make sure that we restrict
	// outbound connections as needed.
	dialer.SetAllowedHosts(conf.AdminConf.AllowedInternalHosts)
	webhook.SetTransport(&http.Transport{
		DialContext: dialer.Dialer().DialContext,
	})

	"github.com/gophish/gophish/dialer"
	restrictedDialer := dialer.Dialer()
		imapClient, err = client.DialWithDialerTLS(restrictedDialer, mbox.Host, config)
		imapClient, err = client.DialWithDialer(restrictedDialer, mbox.Host)
	"github.com/gophish/gophish/dialer"
	dialer := dialer.Dialer()
	d := gomail.NewWithDialer(dialer, host, port, s.Username, s.Password)

func (s *ModelsSuite) TestDefaultDeniedDial(ch *check.C) {
	host := "169.254.169.254"
	port := 25
	smtp := SMTP{
		Host: fmt.Sprintf("%s:%d", host, port),
	}
	d, err := smtp.GetDialer()
	ch.Assert(err, check.Equals, nil)
	_, err = d.Dial()
	ch.Assert(err, check.ErrorMatches, ".*upstream connection denied.*")
}
// SetTransport sets the underlying transport for the default webhook client.
func SetTransport(tr *http.Transport) {
	senderInstance.client.Transport = tr
}