1package eu.siacs.conversations.crypto;
2
3import android.util.Log;
4import android.util.Pair;
5
6import com.google.common.base.MoreObjects;
7import com.google.common.collect.ImmutableList;
8
9import org.bouncycastle.asn1.ASN1Object;
10import org.bouncycastle.asn1.ASN1Primitive;
11import org.bouncycastle.asn1.ASN1TaggedObject;
12import org.bouncycastle.asn1.DERIA5String;
13import org.bouncycastle.asn1.DERUTF8String;
14import org.bouncycastle.asn1.DLSequence;
15import org.bouncycastle.asn1.x500.RDN;
16import org.bouncycastle.asn1.x500.X500Name;
17import org.bouncycastle.asn1.x500.style.BCStyle;
18import org.bouncycastle.asn1.x500.style.IETFUtils;
19import org.bouncycastle.cert.jcajce.JcaX509CertificateHolder;
20
21import java.io.IOException;
22import java.net.IDN;
23import java.security.cert.Certificate;
24import java.security.cert.CertificateEncodingException;
25import java.security.cert.CertificateParsingException;
26import java.security.cert.X509Certificate;
27import java.util.ArrayList;
28import java.util.Collection;
29import java.util.List;
30import java.util.Locale;
31
32import javax.net.ssl.SSLPeerUnverifiedException;
33import javax.net.ssl.SSLSession;
34
35public class XmppDomainVerifier {
36
37 private static final String LOGTAG = "XmppDomainVerifier";
38
39 private static final String SRV_NAME = "1.3.6.1.5.5.7.8.7";
40 private static final String XMPP_ADDR = "1.3.6.1.5.5.7.8.5";
41
42 private static List<String> getCommonNames(final X509Certificate certificate) {
43 List<String> domains = new ArrayList<>();
44 try {
45 X500Name x500name = new JcaX509CertificateHolder(certificate).getSubject();
46 RDN[] rdns = x500name.getRDNs(BCStyle.CN);
47 for (int i = 0; i < rdns.length; ++i) {
48 domains.add(
49 IETFUtils.valueToString(
50 x500name.getRDNs(BCStyle.CN)[i].getFirst().getValue()));
51 }
52 return domains;
53 } catch (CertificateEncodingException e) {
54 return domains;
55 }
56 }
57
58 private static Pair<String, String> parseOtherName(final byte[] otherName) {
59 try {
60 ASN1Primitive asn1Primitive = ASN1Primitive.fromByteArray(otherName);
61 if (asn1Primitive instanceof ASN1TaggedObject taggedObject) {
62 final ASN1Object inner = taggedObject.getBaseObject();
63 if (inner instanceof DLSequence sequence) {
64 if (sequence.size() >= 2
65 && sequence.getObjectAt(1) instanceof ASN1TaggedObject evenInner) {
66 final String oid = sequence.getObjectAt(0).toString();
67 final ASN1Object value = evenInner.getBaseObject();
68 if (value instanceof DERUTF8String derutf8String) {
69 return new Pair<>(oid, derutf8String.getString());
70 } else if (value instanceof DERIA5String deria5String) {
71 return new Pair<>(oid, deria5String.getString());
72 }
73 }
74 }
75 }
76 return null;
77 } catch (final IOException e) {
78 return null;
79 }
80 }
81
82 public static boolean matchDomain(final String needle, final List<String> haystack) {
83 for (final String entry : haystack) {
84 if (entry.startsWith("*.")) {
85 int offset = 0;
86 while (offset < needle.length()) {
87 int i = needle.indexOf('.', offset);
88 if (i < 0) {
89 break;
90 }
91 if (needle.substring(i).equalsIgnoreCase(entry.substring(1))) {
92 return true;
93 }
94 offset = i + 1;
95 }
96 } else {
97 if (entry.equalsIgnoreCase(needle)) {
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 @Override
197 public String toString() {
198 return MoreObjects.toStringHelper(this)
199 .add("xmppAddresses", xmppAddresses)
200 .add("srvNames", srvNames)
201 .add("domains", domains)
202 .toString();
203 }
204 }
205
206 private boolean isSelfSigned(X509Certificate certificate) {
207 try {
208 certificate.verify(certificate.getPublicKey());
209 return true;
210 } catch (Exception e) {
211 return false;
212 }
213 }
214}