1package eu.siacs.conversations.crypto;
2
3import android.util.Log;
4import android.util.Pair;
5import com.google.common.base.MoreObjects;
6import com.google.common.collect.ImmutableList;
7import java.io.IOException;
8import java.net.IDN;
9import java.security.cert.Certificate;
10import java.security.cert.CertificateEncodingException;
11import java.security.cert.CertificateParsingException;
12import java.security.cert.X509Certificate;
13import java.util.ArrayList;
14import java.util.Collection;
15import java.util.List;
16import java.util.Locale;
17import javax.net.ssl.SSLPeerUnverifiedException;
18import javax.net.ssl.SSLSession;
19import org.bouncycastle.asn1.ASN1Object;
20import org.bouncycastle.asn1.ASN1Primitive;
21import org.bouncycastle.asn1.ASN1TaggedObject;
22import org.bouncycastle.asn1.DERIA5String;
23import org.bouncycastle.asn1.DERUTF8String;
24import org.bouncycastle.asn1.DLSequence;
25import org.bouncycastle.asn1.x500.RDN;
26import org.bouncycastle.asn1.x500.X500Name;
27import org.bouncycastle.asn1.x500.style.BCStyle;
28import org.bouncycastle.asn1.x500.style.IETFUtils;
29import org.bouncycastle.cert.jcajce.JcaX509CertificateHolder;
30
31public class XmppDomainVerifier {
32
33 private static final String LOGTAG = "XmppDomainVerifier";
34
35 private static final String SRV_NAME = "1.3.6.1.5.5.7.8.7";
36 private static final String XMPP_ADDR = "1.3.6.1.5.5.7.8.5";
37
38 private static List<String> getCommonNames(final X509Certificate certificate) {
39 List<String> domains = new ArrayList<>();
40 try {
41 X500Name x500name = new JcaX509CertificateHolder(certificate).getSubject();
42 RDN[] rdns = x500name.getRDNs(BCStyle.CN);
43 for (int i = 0; i < rdns.length; ++i) {
44 domains.add(
45 IETFUtils.valueToString(
46 x500name.getRDNs(BCStyle.CN)[i].getFirst().getValue()));
47 }
48 return domains;
49 } catch (CertificateEncodingException e) {
50 return domains;
51 }
52 }
53
54 private static Pair<String, String> parseOtherName(final byte[] otherName) {
55 try {
56 ASN1Primitive asn1Primitive = ASN1Primitive.fromByteArray(otherName);
57 if (asn1Primitive instanceof ASN1TaggedObject taggedObject) {
58 final ASN1Object inner = taggedObject.getBaseObject();
59 if (inner instanceof DLSequence sequence) {
60 if (sequence.size() >= 2
61 && sequence.getObjectAt(1) instanceof ASN1TaggedObject evenInner) {
62 final String oid = sequence.getObjectAt(0).toString();
63 final ASN1Object value = evenInner.getBaseObject();
64 if (value instanceof DERUTF8String derutf8String) {
65 return new Pair<>(oid, derutf8String.getString());
66 } else if (value instanceof DERIA5String deria5String) {
67 return new Pair<>(oid, deria5String.getString());
68 }
69 }
70 }
71 }
72 return null;
73 } catch (final IOException e) {
74 return null;
75 }
76 }
77
78 public static boolean matchDomain(final String needle, final List<String> haystack) {
79 for (final String entry : haystack) {
80 if (entry.startsWith("*.")) {
81 // https://www.rfc-editor.org/rfc/rfc6125#section-6.4.3
82 // wild cards can only be in the left most label and don’t match '.'
83 final int i = needle.indexOf('.');
84 if (i != -1 && needle.substring(i).equalsIgnoreCase(entry.substring(1))) {
85 return true;
86 }
87 } else {
88 if (entry.equalsIgnoreCase(needle)) {
89 return true;
90 }
91 }
92 }
93 return false;
94 }
95
96 public boolean verify(
97 final String unicodeDomain, final String unicodeHostname, SSLSession sslSession)
98 throws SSLPeerUnverifiedException {
99 final String domain = IDN.toASCII(unicodeDomain);
100 final String hostname = unicodeHostname == null ? null : IDN.toASCII(unicodeHostname);
101 final Certificate[] chain = sslSession.getPeerCertificates();
102 if (chain.length == 0 || !(chain[0] instanceof X509Certificate certificate)) {
103 return false;
104 }
105 final List<String> commonNames = getCommonNames(certificate);
106 if (isSelfSigned(certificate)) {
107 if (commonNames.size() == 1 && matchDomain(domain, commonNames)) {
108 Log.d(LOGTAG, "accepted CN in self signed cert as work around for " + domain);
109 return true;
110 }
111 }
112 try {
113 final ValidDomains validDomains = parseValidDomains(certificate);
114 Log.d(LOGTAG, "searching for " + domain + " in " + validDomains);
115 if (hostname != null) {
116 Log.d(LOGTAG, "also trying to verify hostname " + hostname);
117 }
118 return validDomains.xmppAddresses.contains(domain)
119 || validDomains.srvNames.contains("_xmpp-client." + domain)
120 || matchDomain(domain, validDomains.domains)
121 || (hostname != null && matchDomain(hostname, validDomains.domains));
122 } catch (final Exception e) {
123 return false;
124 }
125 }
126
127 public static ValidDomains parseValidDomains(final X509Certificate certificate)
128 throws CertificateParsingException {
129 final List<String> commonNames = getCommonNames(certificate);
130 final Collection<List<?>> alternativeNames = certificate.getSubjectAlternativeNames();
131 final List<String> xmppAddrs = new ArrayList<>();
132 final List<String> srvNames = new ArrayList<>();
133 final List<String> domains = new ArrayList<>();
134 if (alternativeNames != null) {
135 for (List<?> san : alternativeNames) {
136 final Integer type = (Integer) san.get(0);
137 if (type == 0) {
138 final Pair<String, String> otherName = parseOtherName((byte[]) san.get(1));
139 if (otherName != null && otherName.first != null && otherName.second != null) {
140 switch (otherName.first) {
141 case SRV_NAME:
142 srvNames.add(otherName.second.toLowerCase(Locale.US));
143 break;
144 case XMPP_ADDR:
145 xmppAddrs.add(otherName.second.toLowerCase(Locale.US));
146 break;
147 default:
148 Log.d(
149 LOGTAG,
150 "oid: " + otherName.first + " value: " + otherName.second);
151 }
152 }
153 } else if (type == 2) {
154 final Object value = san.get(1);
155 if (value instanceof String) {
156 domains.add(((String) value).toLowerCase(Locale.US));
157 }
158 }
159 }
160 }
161 if (srvNames.isEmpty() && xmppAddrs.isEmpty() && domains.isEmpty()) {
162 domains.addAll(commonNames);
163 }
164 return new ValidDomains(xmppAddrs, srvNames, domains);
165 }
166
167 public static final class ValidDomains {
168 final List<String> xmppAddresses;
169 final List<String> srvNames;
170 final List<String> domains;
171
172 private ValidDomains(
173 List<String> xmppAddresses, List<String> srvNames, List<String> domains) {
174 this.xmppAddresses = xmppAddresses;
175 this.srvNames = srvNames;
176 this.domains = domains;
177 }
178
179 public List<String> all() {
180 ImmutableList.Builder<String> all = new ImmutableList.Builder<>();
181 all.addAll(xmppAddresses);
182 all.addAll(srvNames);
183 all.addAll(domains);
184 return all.build();
185 }
186
187 @Override
188 public String toString() {
189 return MoreObjects.toStringHelper(this)
190 .add("xmppAddresses", xmppAddresses)
191 .add("srvNames", srvNames)
192 .add("domains", domains)
193 .toString();
194 }
195 }
196
197 private boolean isSelfSigned(X509Certificate certificate) {
198 try {
199 certificate.verify(certificate.getPublicKey());
200 return true;
201 } catch (Exception e) {
202 return false;
203 }
204 }
205}