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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.
custom-events
Jordan Wright 11 months ago
committed by GitHub
parent
commit
e3352f481e
No known key found for this signature in database GPG Key ID: 4AEE18F83AFDEB23
12 changed files with 373 additions and 15 deletions
  1. +6
    -5
      config/config.go
  2. +3
    -0
      controllers/api/import.go
  3. +84
    -0
      controllers/api/import_test.go
  4. +158
    -0
      dialer/dialer.go
  5. +85
    -0
      dialer/dialer_test.go
  6. +1
    -3
      go.mod
  7. +2
    -4
      go.sum
  8. +10
    -0
      gophish.go
  9. +4
    -2
      imap/imap.go
  10. +3
    -1
      models/smtp.go
  11. +12
    -0
      models/smtp_test.go
  12. +5
    -0
      webhook/webhook.go

+ 6
- 5
config/config.go View File

@ -9,11 +9,12 @@ import (
// AdminServer represents the Admin server configuration details
type AdminServer struct {
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"`
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"`
}
// PhishServer represents the Phish server configuration details

+ 3
- 0
controllers/api/import.go View File

@ -10,6 +10,7 @@ import (
"strings"
"github.com/PuerkitoBio/goquery"
"github.com/gophish/gophish/dialer"
log "github.com/gophish/gophish/logger"
"github.com/gophish/gophish/models"
"github.com/gophish/gophish/util"
@ -113,7 +114,9 @@ func (as *Server) ImportSite(w http.ResponseWriter, r *http.Request) {
JSONResponse(w, models.Response{Success: false, Message: err.Error()}, http.StatusBadRequest)
return
}
restrictedDialer := dialer.Dialer()
tr := &http.Transport{
DialContext: restrictedDialer.DialContext,
TLSClientConfig: &tls.Config{
InsecureSkipVerify: true,
},

+ 84
- 0
controllers/api/import_test.go View File

@ -0,0 +1,84 @@
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)
}
}

+ 158
- 0
dialer/dialer.go View File

@ -0,0 +1,158 @@
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
}
}

+ 85
- 0
dialer/dialer_test.go View File

@ -0,0 +1,85 @@
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)
}

+ 1
- 3
go.mod View File

@ -11,7 +11,7 @@ require (
github.com/emersion/go-imap v1.0.4
github.com/emersion/go-message v0.12.0
github.com/go-sql-driver/mysql v1.5.0
github.com/gophish/gomail v0.0.0-20180314010319-cf7e1a5479be
github.com/gophish/gomail v0.0.0-20200818021916-1f6d0dfd512e
github.com/gorilla/context v1.1.1
github.com/gorilla/csrf v1.6.2
github.com/gorilla/handlers v1.4.2
@ -29,7 +29,5 @@ require (
golang.org/x/crypto v0.0.0-20200128174031-69ecbb4d6d5d
golang.org/x/time v0.0.0-20200416051211-89c76fbcd5d1
gopkg.in/alecthomas/kingpin.v2 v2.2.6
gopkg.in/alexcesaro/quotedprintable.v3 v3.0.0-20150716171945-2caba252f4dc // indirect
gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405
gopkg.in/gomail.v2 v2.0.0-20160411212932-81ebce5c23df // indirect
)

+ 2
- 4
go.sum View File

@ -32,8 +32,8 @@ github.com/go-sql-driver/mysql v1.5.0/go.mod h1:DCzpHaOWr8IXmIStZouvnhqoel9Qv2LB
github.com/golang-sql/civil v0.0.0-20190719163853-cb61b32ac6fe h1:lXe2qZdvpiX5WZkZR4hgp4KJVfY3nMkvmwbVkpv1rVY=
github.com/golang-sql/civil v0.0.0-20190719163853-cb61b32ac6fe/go.mod h1:8vg3r2VgvsThLBIFL93Qb5yWzgyZWhEmBwUJWevAkK0=
github.com/golang/protobuf v1.2.0/go.mod h1:6lQm79b+lXiMfvg/cZm0SGofjICqVBUtrP5yJMmIC1U=
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=
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=
github.com/gorilla/context v1.1.1 h1:AWwleXJkX/nhcU9bZSnZoi3h/qGYqQAGhq6zZe/aQW8=
github.com/gorilla/context v1.1.1/go.mod h1:kBGZzfjB9CEq2AlWe17Uuf7NDRt0dE0s8S51q0aT7Yg=
github.com/gorilla/csrf v1.6.2 h1:QqQ/OWwuFp4jMKgBFAzJVW3FMULdyUW7JoM4pEWuqKg=
@ -110,7 +110,5 @@ gopkg.in/alexcesaro/quotedprintable.v3 v3.0.0-20150716171945-2caba252f4dc h1:2gG
gopkg.in/alexcesaro/quotedprintable.v3 v3.0.0-20150716171945-2caba252f4dc/go.mod h1:m7x9LTH6d71AHyAX77c9yqWCCa3UKHcVEj9y7hAtKDk=
gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405 h1:yhCVgyC4o1eVCa2tZl7eS0r+SDo693bJlVdllGtEeKM=
gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405/go.mod h1:Co6ibVJAznAaIkqp8huTwlJQCZ016jof/cbN4VW5Yz0=
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=
gopkg.in/yaml.v2 v2.2.2 h1:ZCJp+EgiOT7lHqUV2J862kp8Qj64Jo6az82+3Td9dZw=
gopkg.in/yaml.v2 v2.2.2/go.mod h1:hI93XBmqTisBFMUTm0b8Fm+jr3Dg1NNxqwp+5A1VGuI=

+ 10
- 0
gophish.go View File

@ -28,6 +28,7 @@ THE SOFTWARE.
import (
"fmt"
"io/ioutil"
"net/http"
"os"
"os/signal"
@ -35,10 +36,12 @@ import (
"github.com/gophish/gophish/config"
"github.com/gophish/gophish/controllers"
"github.com/gophish/gophish/dialer"
"github.com/gophish/gophish/imap"
log "github.com/gophish/gophish/logger"
"github.com/gophish/gophish/middleware"
"github.com/gophish/gophish/models"
"github.com/gophish/gophish/webhook"
)
const (
@ -79,6 +82,13 @@ func main() {
}
config.Version = string(version)
// 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,
})
err = log.Setup(conf.Logging)
if err != nil {
log.Fatal(err)

+ 4
- 2
imap/imap.go View File

@ -11,6 +11,7 @@ import (
"github.com/emersion/go-imap"
"github.com/emersion/go-imap/client"
"github.com/emersion/go-message/charset"
"github.com/gophish/gophish/dialer"
log "github.com/gophish/gophish/logger"
"github.com/gophish/gophish/models"
@ -184,12 +185,13 @@ func (mbox *Mailbox) GetUnread(markAsRead, delete bool) ([]Email, error) {
func (mbox *Mailbox) newClient() (*client.Client, error) {
var imapClient *client.Client
var err error
restrictedDialer := dialer.Dialer()
if mbox.TLS {
config := new(tls.Config)
config.InsecureSkipVerify = mbox.IgnoreCertErrors
imapClient, err = client.DialTLS(mbox.Host, config)
imapClient, err = client.DialWithDialerTLS(restrictedDialer, mbox.Host, config)
} else {
imapClient, err = client.Dial(mbox.Host)
imapClient, err = client.DialWithDialer(restrictedDialer, mbox.Host)
}
if err != nil {
return imapClient, err

+ 3
- 1
models/smtp.go View File

@ -10,6 +10,7 @@ import (
"time"
"github.com/gophish/gomail"
"github.com/gophish/gophish/dialer"
log "github.com/gophish/gophish/logger"
"github.com/gophish/gophish/mailer"
"github.com/jinzhu/gorm"
@ -109,7 +110,8 @@ func (s *SMTP) GetDialer() (mailer.Dialer, error) {
log.Error(err)
return nil, err
}
d := gomail.NewDialer(host, port, s.Username, s.Password)
dialer := dialer.Dialer()
d := gomail.NewWithDialer(dialer, host, port, s.Username, s.Password)
d.TLSConfig = &tls.Config{
ServerName: host,
InsecureSkipVerify: s.IgnoreCertErrors,

+ 12
- 0
models/smtp_test.go View File

@ -81,3 +81,15 @@ func (s *ModelsSuite) TestGetInvalidSMTP(ch *check.C) {
_, err := GetSMTP(-1, 1)
ch.Assert(err, check.Equals, gorm.ErrRecordNotFound)
}
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.*")
}

+ 5
- 0
webhook/webhook.go View File

@ -51,6 +51,11 @@ var senderInstance = &defaultSender{
},
}
// SetTransport sets the underlying transport for the default webhook client.
func SetTransport(tr *http.Transport) {
senderInstance.client.Transport = tr
}
// EndPoint represents a URL to send the webhook to, as well as a secret used
// to sign the event
type EndPoint struct {

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