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DNS malware (#36)
Task/Issue URL: https://app.asana.com/0/1198194956794324/1208368538104397/f ### Description Add detection for when the DNS blocks requests to domains that serve malware. The library also calls back into JVM with the blocked domain, if the JVM callback is present ### Steps to test this PR _Test_ - [x] checkout this branch and `cd` into the `android` folder - [x] run `./gradlew assemble publishToMavenLocal` - [x] go to the Android app repo, `develop` branch and apply the following patch ```diff commit 40e3568897a31e8c603490f5f49a519773aff8c9 Author: Aitor Viana <[email protected]> Date: Sun Jun 4 20:49:52 2023 -0400 Maven local use diff --git a/build.gradle b/build.gradle index de22b7abb..aee98799a 100644 --- a/build.gradle +++ b/build.gradle @@ -42,6 +42,7 @@ allprojects { google() mavenCentral() maven { url 'https://jitpack.io' } + mavenLocal() } configurations.all { resolutionStrategy.force 'org.objenesis:objenesis:2.6' diff --git a/versions.properties b/versions.properties index d092a0163..5f58ba46a 100644 --- a/versions.properties +++ b/versions.properties @@ -77,7 +77,7 @@ version.com.airbnb.android..lottie=5.2.0 version.com.android.installreferrer..installreferrer=2.2 -version.com.duckduckgo.netguard..netguard-android=1.6.12 +version.com.duckduckgo.netguard..netguard-android=1.7.0-SNAPSHOT version.com.duckduckgo.synccrypto..sync-crypto-android=0.3.0 ``` - [x] build Android app, `./gradlew assembleID`, install and run the app - [x] enable the VPN - [x] filter the logcat with `MID_RECORD_MALWARE_BLOCK` and another logcat with `tag:WireGuard/GoBackend/Write` - [x] with VPN enabled, go to "vpn-malware.goduckgo.com" - [x] verify `DNS malware was blocked for domain: vpn-malware.goduckgo.com. due to 'blocked:m' TXT record` log appears - [x] verify `MID_RECORD_MALWARE_BLOCK method not found` error log appears - [x] smoke test VPN and browsing
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‎src/wireguard/dns-malware.go

+86
Original file line numberDiff line numberDiff line change
@@ -0,0 +1,86 @@
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/*
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* Copyright (c) 2022 DuckDuckGo
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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package main
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// #include <android/log.h>
20+
import "C"
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import (
23+
"fmt"
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"strings"
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"github.com/miekg/dns"
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)
28+
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30+
// parseDNSResponse parses the raw DNS response from a byte slice.
31+
func parseDNSResponse(data []byte) *dns.Msg {
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tag := cstring("WireGuard/GoBackend/parseDNSResponse")
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// Create a new DNS message structure
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dnsMsg := new(dns.Msg)
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// Unpack the DNS message from the raw data
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err := dnsMsg.Unpack(data)
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if err != nil {
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C.__android_log_write(C.ANDROID_LOG_DEBUG, tag, cstring(fmt.Sprintf("Failed to unpack DNS message: %v", err)))
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return nil
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}
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// Check if this is a DNS response (QR bit set)
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if dnsMsg.Response {
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return dnsMsg
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}
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// If not a response, return nil
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return nil
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}
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/*
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* WasDNSMalwareBlocked checks if the DNS packet contains a "blocked:m" TXT
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* record under the "explanation.invalid" domain. If such a record is found,
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* it returns true along with the domain being blocked.
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* That record is found when our the DDG (malware) DNS server blocks domains that
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* serve malware
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*/
60+
func WasDNSMalwareBlocked(dnsData []byte) (bool, string) {
61+
dnsResponse := parseDNSResponse(dnsData)
62+
if dnsResponse == nil {
63+
return false, ""
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}
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// Look for "explanation.invalid" in the additional section
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for _, rr := range dnsResponse.Extra {
68+
if txtRecord, ok := rr.(*dns.TXT); ok {
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if txtRecord.Hdr.Name == "explanation.invalid." {
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for _, txt := range txtRecord.Txt {
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if txt == "blocked:m" {
72+
// If there is a matching TXT record, return the blocked domain
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if len(dnsResponse.Question) > 0 {
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blockedDomain := dnsResponse.Question[0].Name
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// remove the trailing dot (FQDN) if present
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blockedDomain = strings.TrimSuffix(blockedDomain, ".")
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return true, blockedDomain
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}
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}
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}
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}
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}
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}
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return false, ""
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}

‎src/wireguard/go.mod

+7-3
Original file line numberDiff line numberDiff line change
@@ -3,12 +3,16 @@ module golang.zx2c4.com/wireguard/android
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go 1.18
44

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require (
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golang.org/x/net v0.10.0
7-
golang.org/x/sys v0.8.0
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golang.org/x/net v0.27.0
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golang.org/x/sys v0.22.0
88
golang.zx2c4.com/wireguard v0.0.0-20230325221338-052af4a8072b
99
)
1010

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require (
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golang.org/x/crypto v0.9.0 // indirect
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github.com/miekg/dns v1.1.62 // indirect
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golang.org/x/crypto v0.25.0 // indirect
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golang.org/x/mod v0.18.0 // indirect
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golang.org/x/sync v0.7.0 // indirect
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golang.org/x/tools v0.22.0 // indirect
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golang.zx2c4.com/wintun v0.0.0-20230126152724-0fa3db229ce2 // indirect
1418
)

‎src/wireguard/go.sum

+14
Original file line numberDiff line numberDiff line change
@@ -1,11 +1,25 @@
11
github.com/google/btree v1.0.1 h1:gK4Kx5IaGY9CD5sPJ36FHiBJ6ZXl0kilRiiCj+jdYp4=
2+
github.com/miekg/dns v1.1.62 h1:cN8OuEF1/x5Rq6Np+h1epln8OiyPWV+lROx9LxcGgIQ=
3+
github.com/miekg/dns v1.1.62/go.mod h1:mvDlcItzm+br7MToIKqkglaGhlFMHJ9DTNNWONWXbNQ=
24
golang.org/x/crypto v0.9.0 h1:LF6fAI+IutBocDJ2OT0Q1g8plpYljMZ4+lty+dsqw3g=
35
golang.org/x/crypto v0.9.0/go.mod h1:yrmDGqONDYtNj3tH8X9dzUun2m2lzPa9ngI6/RUPGR0=
6+
golang.org/x/crypto v0.25.0 h1:ypSNr+bnYL2YhwoMt2zPxHFmbAN1KZs/njMG3hxUp30=
7+
golang.org/x/crypto v0.25.0/go.mod h1:T+wALwcMOSE0kXgUAnPAHqTLW+XHgcELELW8VaDgm/M=
8+
golang.org/x/mod v0.18.0 h1:5+9lSbEzPSdWkH32vYPBwEpX8KwDbM52Ud9xBUvNlb0=
9+
golang.org/x/mod v0.18.0/go.mod h1:hTbmBsO62+eylJbnUtE2MGJUyE7QWk4xUqPFrRgJ+7c=
410
golang.org/x/net v0.10.0 h1:X2//UzNDwYmtCLn7To6G58Wr6f5ahEAQgKNzv9Y951M=
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golang.org/x/net v0.10.0/go.mod h1:0qNGK6F8kojg2nk9dLZ2mShWaEBan6FAoqfSigmmuDg=
12+
golang.org/x/net v0.27.0 h1:5K3Njcw06/l2y9vpGCSdcxWOYHOUk3dVNGDXN+FvAys=
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golang.org/x/net v0.27.0/go.mod h1:dDi0PyhWNoiUOrAS8uXv/vnScO4wnHQO4mj9fn/RytE=
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golang.org/x/sync v0.7.0 h1:YsImfSBoP9QPYL0xyKJPq0gcaJdG3rInoqxTWbfQu9M=
15+
golang.org/x/sync v0.7.0/go.mod h1:Czt+wKu1gCyEFDUtn0jG5QVvpJ6rzVqr5aXyt9drQfk=
616
golang.org/x/sys v0.8.0 h1:EBmGv8NaZBZTWvrbjNoL6HVt+IVy3QDQpJs7VRIw3tU=
717
golang.org/x/sys v0.8.0/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
18+
golang.org/x/sys v0.22.0 h1:RI27ohtqKCnwULzJLqkv897zojh5/DwS/ENaMzUOaWI=
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golang.org/x/sys v0.22.0/go.mod h1:/VUhepiaJMQUp4+oa/7Zr1D23ma6VTLIYjOOTFZPUcA=
820
golang.org/x/time v0.0.0-20191024005414-555d28b269f0 h1:/5xXl8Y5W96D+TtHSlonuFqGHIWVuyCkGJLwGh9JJFs=
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golang.org/x/tools v0.22.0 h1:gqSGLZqv+AI9lIQzniJ0nZDRG5GBPsSi+DRNHWNz6yA=
22+
golang.org/x/tools v0.22.0/go.mod h1:aCwcsjqvq7Yqt6TNyX7QMU2enbQ/Gt0bo6krSeEri+c=
923
golang.zx2c4.com/wintun v0.0.0-20230126152724-0fa3db229ce2 h1:B82qJJgjvYKsXS9jeunTOisW56dUokqW/FOteYJJ/yg=
1024
golang.zx2c4.com/wintun v0.0.0-20230126152724-0fa3db229ce2/go.mod h1:deeaetjYA+DHMHg+sMSMI58GrEteJUUzzw7en6TJQcI=
1125
golang.zx2c4.com/wireguard v0.0.0-20230325221338-052af4a8072b h1:J1CaxgLerRR5lgx3wnr6L04cJFbWoceSK9JWBdglINo=

‎src/wireguard/jni.c

+27
Original file line numberDiff line numberDiff line change
@@ -18,6 +18,7 @@ extern char *wgVersion();
1818
static JavaVM *JVM = NULL;
1919
static jobject GO_BACKEND = NULL;
2020
static jmethodID MID_SHOULD_ALLOW = NULL;
21+
static jmethodID MID_RECORD_MALWARE_BLOCK = NULL;
2122
static jint SDK = 0;
2223

2324
JNIEXPORT jint JNICALL Java_com_wireguard_android_backend_GoBackend_wgTurnOn(JNIEnv *env, jobject goBackend, jstring ifname,
@@ -39,6 +40,7 @@ JNIEXPORT jint JNICALL Java_com_wireguard_android_backend_GoBackend_wgTurnOn(JNI
3940
jclass clsGoBackend = (*env)->GetObjectClass(env, goBackend);
4041
const char *shouldAllowSig = "(ILjava/lang/String;ILjava/lang/String;ILjava/lang/String;I)Z";
4142
MID_SHOULD_ALLOW = jniGetMethodID(env, clsGoBackend, "shouldAllow", shouldAllowSig);
43+
MID_RECORD_MALWARE_BLOCK = jniGetMethodID(env, clsGoBackend, "recordMalwareBlock", "(Ljava/lang/String;)V");
4244
(*env)->DeleteLocalRef(env, clsGoBackend);
4345

4446
// Call Go method
@@ -137,6 +139,31 @@ int is_pkt_allowed(const uint8_t *buffer, int length) {
137139
return 1;
138140
}
139141

142+
int record_malware_block(const char *domain) {
143+
if (MID_RECORD_MALWARE_BLOCK == NULL) {
144+
log_print(PLATFORM_LOG_PRIORITY_ERROR, "MID_RECORD_MALWARE_BLOCK method not found");
145+
return 1;
146+
}
147+
148+
JNIEnv *env;
149+
jint rs = (*JVM)->AttachCurrentThread(JVM, &env, NULL);
150+
if (rs != JNI_OK) {
151+
log_print(PLATFORM_LOG_PRIORITY_ERROR, "Could not attach to JVM thread");
152+
return 1;
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}
154+
155+
// Prep call to Kotlin
156+
jstring jdomain = (*env)->NewStringUTF(env, domain);
157+
(*env)->CallVoidMethod(env, GO_BACKEND, MID_RECORD_MALWARE_BLOCK, jdomain);
158+
jniCheckException(env);
159+
160+
// cleanup
161+
(*env)->DeleteLocalRef(env, jdomain);
162+
163+
return 0;
164+
165+
}
166+
140167
JNIEXPORT void JNICALL Java_com_wireguard_android_backend_GoBackend_wgTurnOff(JNIEnv *env, jclass c, jint handle)
141168
{
142169
wgTurnOff(handle);

‎src/wireguard/tun_android.go

+48-3
Original file line numberDiff line numberDiff line change
@@ -22,8 +22,10 @@ Implementation of the TUN device interface for Android (wraps linux one)
2222

2323

2424
// #include <android/log.h>
25+
// #include <stdlib.h> // For C.free and C string functions
2526
// extern int is_pkt_allowed(char *buffer, int length);
2627
// extern int wg_write_pcap(char *buffer, int length);
28+
// extern int record_malware_block(const char *domain);
2729
import "C"
2830

2931
import (
@@ -50,10 +52,53 @@ func (tunWrapper *NativeTunWrapper) Name() (string, error) {
5052
return tunWrapper.nativeTun.Name()
5153
}
5254

53-
func (tunWrapper *NativeTunWrapper) Write(buf [][]byte, offset int) (int, error) {
54-
pktLen, err := tunWrapper.nativeTun.Write(buf, offset)
55+
func (tunWrapper *NativeTunWrapper) Write(bufs [][]byte, offset int) (int, error) {
56+
tag := cstring("WireGuard/GoBackend/Write")
5557

56-
// tag := cstring("WireGuard/GoBackend/Write")
58+
for _, buf := range bufs {
59+
// Check if it's an IPv4 packet
60+
if len(buf) <= offset {
61+
C.__android_log_write(C.ANDROID_LOG_DEBUG, tag, cstring("Skipping invalid packet, too short"))
62+
continue
63+
}
64+
switch buf[offset] >> 4 {
65+
case ipv4.Version:
66+
if len(buf) < ipv4.HeaderLen {
67+
C.__android_log_write(C.ANDROID_LOG_DEBUG, tag, cstring("Skipping bad IPv4 packet"))
68+
continue
69+
}
70+
71+
// Check if it's a UDP packet
72+
protocol := buf[offset+9]
73+
if protocol == 0x11 { // UDP
74+
// Extract the ports (skip IP and check transport layer headers)
75+
srcPort := (uint16(buf[offset+ipv4.HeaderLen]) << 8) | uint16(buf[offset+ipv4.HeaderLen+1])
76+
dstPort := (uint16(buf[offset+ipv4.HeaderLen+2]) << 8) | uint16(buf[offset+ipv4.HeaderLen+3])
77+
78+
if srcPort == 53 || dstPort == 53 {
79+
// Extract the DNS data (skip IP and UDP headers)
80+
dnsData := buf[offset+ipv4.HeaderLen+8:]
81+
82+
// Call the helper function to check if the DNS packet should be blocked
83+
shouldBlock, blockedDomain := WasDNSMalwareBlocked(dnsData)
84+
if shouldBlock {
85+
logMessage := "DNS malware was blocked for domain: " + blockedDomain + " due to 'blocked:m' TXT record"
86+
C.__android_log_write(C.ANDROID_LOG_DEBUG, tag, cstring(logMessage))
87+
88+
// call back into JVM and let the packet flow normally
89+
cBlockedDomain := C.CString(blockedDomain)
90+
defer C.free(unsafe.Pointer(cBlockedDomain))
91+
C.record_malware_block(cBlockedDomain) // ignore return code
92+
}
93+
}
94+
}
95+
default:
96+
// Not an IPv4 packet
97+
C.__android_log_write(C.ANDROID_LOG_DEBUG, tag, cstring("Invalid IP"))
98+
}
99+
}
100+
101+
pktLen, err := tunWrapper.nativeTun.Write(bufs, offset)
57102

58103
// PCAP recording
59104
// pcap_res := int(C.wg_write_pcap((*C.char)(unsafe.Pointer(&buf[offset])), C.int(pktLen+offset)))

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