1package eu.siacs.conversations.crypto;
2
3import android.util.Log;
4import android.util.Pair;
5import androidx.annotation.NonNull;
6import com.google.common.base.CharMatcher;
7import com.google.common.base.MoreObjects;
8import com.google.common.collect.ImmutableList;
9import java.io.IOException;
10import java.net.IDN;
11import java.security.cert.Certificate;
12import java.security.cert.CertificateEncodingException;
13import java.security.cert.CertificateParsingException;
14import java.security.cert.X509Certificate;
15import java.util.ArrayList;
16import java.util.Collection;
17import java.util.Collections;
18import java.util.List;
19import java.util.Locale;
20import javax.net.ssl.SSLPeerUnverifiedException;
21import javax.net.ssl.SSLSession;
22import org.bouncycastle.asn1.ASN1Object;
23import org.bouncycastle.asn1.ASN1Primitive;
24import org.bouncycastle.asn1.ASN1TaggedObject;
25import org.bouncycastle.asn1.DERIA5String;
26import org.bouncycastle.asn1.DERUTF8String;
27import org.bouncycastle.asn1.DLSequence;
28import org.bouncycastle.asn1.x500.RDN;
29import org.bouncycastle.asn1.x500.style.BCStyle;
30import org.bouncycastle.asn1.x500.style.IETFUtils;
31import org.bouncycastle.cert.jcajce.JcaX509CertificateHolder;
32
33public class XmppDomainVerifier {
34
35 private static final String LOGTAG = "XmppDomainVerifier";
36
37 private static final String SRV_NAME = "1.3.6.1.5.5.7.8.7";
38 private static final String XMPP_ADDR = "1.3.6.1.5.5.7.8.5";
39
40 private static List<String> getCommonNames(final X509Certificate certificate) {
41 final var domains = new ImmutableList.Builder<String>();
42 try {
43 final var x500name = new JcaX509CertificateHolder(certificate).getSubject();
44 final RDN[] nameRDNs = x500name.getRDNs(BCStyle.CN);
45 for (int i = 0; i < nameRDNs.length; ++i) {
46 domains.add(
47 IETFUtils.valueToString(
48 x500name.getRDNs(BCStyle.CN)[i].getFirst().getValue()));
49 }
50 return domains.build();
51 } catch (final CertificateEncodingException e) {
52 return Collections.emptyList();
53 }
54 }
55
56 private static Pair<String, String> parseOtherName(final byte[] otherName) {
57 try {
58 ASN1Primitive asn1Primitive = ASN1Primitive.fromByteArray(otherName);
59 if (asn1Primitive instanceof ASN1TaggedObject taggedObject) {
60 final ASN1Object inner = taggedObject.getBaseObject();
61 if (inner instanceof DLSequence sequence) {
62 if (sequence.size() >= 2
63 && sequence.getObjectAt(1) instanceof ASN1TaggedObject evenInner) {
64 final String oid = sequence.getObjectAt(0).toString();
65 final ASN1Object value = evenInner.getBaseObject();
66 if (value instanceof DERUTF8String derutf8String) {
67 return new Pair<>(oid, derutf8String.getString());
68 } else if (value instanceof DERIA5String deria5String) {
69 return new Pair<>(oid, deria5String.getString());
70 }
71 }
72 }
73 }
74 return null;
75 } catch (final IOException e) {
76 return null;
77 }
78 }
79
80 public static boolean matchDomain(final String domain, final List<String> certificateDomains) {
81 for (final String certificateDomain : certificateDomains) {
82 if (certificateDomain.startsWith("*.")) {
83 // https://www.rfc-editor.org/rfc/rfc6125#section-6.4.3
84 // wild cards can only be in the left most label and don’t match '.'
85 final var wildcardEntry = certificateDomain.substring(1);
86 if (CharMatcher.is('.').countIn(wildcardEntry) < 2) {
87 Log.w(LOGTAG, "not enough labels in wildcard certificate");
88 break;
89 }
90 final int position = domain.indexOf('.');
91 if (position != -1 && domain.substring(position).equalsIgnoreCase(wildcardEntry)) {
92 Log.d(LOGTAG, "domain " + domain + " matched " + certificateDomain);
93 return true;
94 }
95 } else {
96 if (certificateDomain.equalsIgnoreCase(domain)) {
97 Log.d(LOGTAG, "domain " + domain + " matched " + certificateDomain);
98 return true;
99 }
100 }
101 }
102 return false;
103 }
104
105 public boolean verify(
106 final String unicodeDomain, final String unicodeHostname, SSLSession sslSession)
107 throws SSLPeerUnverifiedException {
108 final String domain = IDN.toASCII(unicodeDomain);
109 final String hostname = unicodeHostname == null ? null : IDN.toASCII(unicodeHostname);
110 final Certificate[] chain = sslSession.getPeerCertificates();
111 if (chain.length == 0 || !(chain[0] instanceof X509Certificate certificate)) {
112 return false;
113 }
114 final List<String> commonNames = getCommonNames(certificate);
115 if (isSelfSigned(certificate)) {
116 if (commonNames.size() == 1 && matchDomain(domain, commonNames)) {
117 Log.d(LOGTAG, "accepted CN in self signed cert as work around for " + domain);
118 return true;
119 }
120 }
121 try {
122 final ValidDomains validDomains = parseValidDomains(certificate);
123 Log.d(LOGTAG, "searching for " + domain + " in " + validDomains);
124 if (hostname != null) {
125 Log.d(LOGTAG, "also trying to verify hostname " + hostname);
126 }
127 return validDomains.xmppAddresses.contains(domain)
128 || validDomains.srvNames.contains("_xmpp-client." + domain)
129 || matchDomain(domain, validDomains.domains)
130 || (hostname != null && matchDomain(hostname, validDomains.domains));
131 } catch (final Exception e) {
132 return false;
133 }
134 }
135
136 public static ValidDomains parseValidDomains(final X509Certificate certificate)
137 throws CertificateParsingException {
138 final List<String> commonNames = getCommonNames(certificate);
139 final Collection<List<?>> alternativeNames = certificate.getSubjectAlternativeNames();
140 final List<String> xmppAddrs = new ArrayList<>();
141 final List<String> srvNames = new ArrayList<>();
142 final List<String> domains = new ArrayList<>();
143 if (alternativeNames != null) {
144 for (List<?> san : alternativeNames) {
145 final Integer type = (Integer) san.get(0);
146 if (type == 0) {
147 final Pair<String, String> otherName = parseOtherName((byte[]) san.get(1));
148 if (otherName != null && otherName.first != null && otherName.second != null) {
149 switch (otherName.first) {
150 case SRV_NAME:
151 srvNames.add(otherName.second.toLowerCase(Locale.US));
152 break;
153 case XMPP_ADDR:
154 xmppAddrs.add(otherName.second.toLowerCase(Locale.US));
155 break;
156 default:
157 Log.d(
158 LOGTAG,
159 "oid: " + otherName.first + " value: " + otherName.second);
160 }
161 }
162 } else if (type == 2) {
163 final Object value = san.get(1);
164 if (value instanceof String) {
165 domains.add(((String) value).toLowerCase(Locale.US));
166 }
167 }
168 }
169 }
170 if (srvNames.isEmpty() && xmppAddrs.isEmpty() && domains.isEmpty()) {
171 domains.addAll(commonNames);
172 }
173 return new ValidDomains(xmppAddrs, srvNames, domains);
174 }
175
176 public static final class ValidDomains {
177 final List<String> xmppAddresses;
178 final List<String> srvNames;
179 final List<String> domains;
180
181 private ValidDomains(
182 List<String> xmppAddresses, List<String> srvNames, List<String> domains) {
183 this.xmppAddresses = xmppAddresses;
184 this.srvNames = srvNames;
185 this.domains = domains;
186 }
187
188 public List<String> all() {
189 ImmutableList.Builder<String> all = new ImmutableList.Builder<>();
190 all.addAll(xmppAddresses);
191 all.addAll(srvNames);
192 all.addAll(domains);
193 return all.build();
194 }
195
196 @NonNull
197 @Override
198 public String toString() {
199 return MoreObjects.toStringHelper(this)
200 .add("xmppAddresses", xmppAddresses)
201 .add("srvNames", srvNames)
202 .add("domains", domains)
203 .toString();
204 }
205 }
206
207 private boolean isSelfSigned(X509Certificate certificate) {
208 try {
209 certificate.verify(certificate.getPublicKey());
210 return true;
211 } catch (Exception e) {
212 return false;
213 }
214 }
215}