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FairEmail
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Check server certificate fingerprint - proof of concept

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pull/169/head
M66B 5 years ago
parent 326788a711
commit 0bf59f64a9
2 changed files with 106 additions and 4 deletions
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10
app/src/main/java/eu/faircode/email/Helper.java
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@ -628,8 +628,16 @@ public class Helper {
return sha256(data.getBytes());
}
static String sha1(byte[] data) throws NoSuchAlgorithmException {
return sha("SHA-1", data);
}
static String sha256(byte[] data) throws NoSuchAlgorithmException {
byte[] bytes = MessageDigest.getInstance("SHA-256").digest(data);
return sha("SHA-256", data);
}
static String sha(String digest, byte[] data) throws NoSuchAlgorithmException {
byte[] bytes = MessageDigest.getInstance(digest).digest(data);
StringBuilder sb = new StringBuilder();
for (byte b : bytes)
sb.append(String.format("%02x", b));

100
app/src/main/java/eu/faircode/email/MailService.java
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@ -12,13 +12,22 @@ import com.sun.mail.imap.IMAPFolder;
import com.sun.mail.imap.IMAPStore;
import com.sun.mail.smtp.SMTPTransport;
import com.sun.mail.util.MailConnectException;
import com.sun.mail.util.MailSSLSocketFactory;
import org.bouncycastle.asn1.x509.GeneralName;
import java.net.Inet4Address;
import java.net.Inet6Address;
import java.net.InetAddress;
import java.net.UnknownHostException;
import java.security.GeneralSecurityException;
import java.security.NoSuchAlgorithmException;
import java.security.cert.Certificate;
import java.security.cert.CertificateEncodingException;
import java.security.cert.X509Certificate;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collection;
import java.util.Collections;
import java.util.HashMap;
import java.util.LinkedHashMap;
@ -35,6 +44,8 @@ import javax.mail.Service;
import javax.mail.Session;
import javax.mail.Store;
import javax.mail.event.StoreListener;
import javax.net.ssl.SSLPeerUnverifiedException;
import javax.net.ssl.SSLSocket;
public class MailService implements AutoCloseable {
private Context context;
@ -44,6 +55,10 @@ public class MailService implements AutoCloseable {
private Properties properties;
private Session isession;
private Service iservice;
private boolean configuring;
private String fingerprint;
private X509Certificate certificate;
private boolean trusted;
private StoreListener listener;
private ExecutorService executor = Helper.getBackgroundExecutor(0, "mail");
@ -75,6 +90,66 @@ public class MailService implements AutoCloseable {
boolean socks_enabled = prefs.getBoolean("socks_enabled", false);
String socks_proxy = prefs.getString("socks_proxy", "localhost:9050");
if (BuildConfig.DEBUG)
try {
// openssl s_client -connect host:port < /dev/null 2>/dev/null | openssl x509 -fingerprint -noout -in /dev/stdin
MailSSLSocketFactory sf = new MailSSLSocketFactory() {
@Override
public synchronized boolean isServerTrusted(String server, SSLSocket sslSocket) {
try {
Certificate[] certificates = sslSocket.getSession().getPeerCertificates();
if (certificates == null || certificates.length == 0 ||
!(certificates[0] instanceof X509Certificate))
return false;
certificate = (X509Certificate) certificates[0];
Collection<List<?>> altNames = certificate.getSubjectAlternativeNames();
if (altNames != null)
for (List altName : altNames)
if (altName.get(0).equals(GeneralName.dNSName)) {
String name = (String) altName.get(1);
Log.i("Trusted name=" + name);
if (name.startsWith("*.")) {
// Wildcard certificate
String domain = name.substring(2);
if (TextUtils.isEmpty(domain))
continue;
int dot = server.indexOf(".");
if (dot < 0)
continue;
String cdomain = server.substring(dot + 1);
if (TextUtils.isEmpty(cdomain))
continue;
Log.i("Trust " + domain + " =? " + cdomain);
if (domain.equalsIgnoreCase(cdomain))
trusted = true;
} else {
Log.i("Trust " + server + " =? " + name);
if (server.equalsIgnoreCase(name))
trusted = true;
}
}
if (fingerprint != null && fingerprint.equals(getFingerPrint()))
trusted = true;
Log.i("Is trusted? server=" + server + " trusted=" + trusted);
return (configuring || trusted);
} catch (Throwable ex) {
Log.e(ex);
return false;
}
}
};
properties.put("mail." + protocol + ".ssl.socketFactory", sf);
properties.put("mail." + protocol + ".socketFactory.fallback", "false");
} catch (GeneralSecurityException ex) {
Log.e(ex);
}
// SOCKS proxy
if (socks_enabled) {
String[] address = socks_proxy.split(":");
@ -108,7 +183,8 @@ public class MailService implements AutoCloseable {
// https://javaee.github.io/javamail/docs/api/com/sun/mail/pop3/package-summary.html#properties
properties.put("mail." + protocol + ".ssl.checkserveridentity", Boolean.toString(!insecure));
properties.put("mail." + protocol + ".ssl.trust", "*");
if (!BuildConfig.DEBUG)
properties.put("mail." + protocol + ".ssl.trust", "*");
properties.put("mail.pop3s.starttls.enable", "false");
@ -118,7 +194,8 @@ public class MailService implements AutoCloseable {
} else if ("imap".equals(protocol) || "imaps".equals(protocol)) {
// https://javaee.github.io/javamail/docs/api/com/sun/mail/imap/package-summary.html#properties
properties.put("mail." + protocol + ".ssl.checkserveridentity", Boolean.toString(!insecure));
properties.put("mail." + protocol + ".ssl.trust", "*");
if (!BuildConfig.DEBUG)
properties.put("mail." + protocol + ".ssl.trust", "*");
properties.put("mail.imaps.starttls.enable", "false");
@ -147,7 +224,8 @@ public class MailService implements AutoCloseable {
} else if ("smtp".equals(protocol) || "smtps".equals(protocol)) {
// https://javaee.github.io/javamail/docs/api/com/sun/mail/smtp/package-summary.html#properties
properties.put("mail." + protocol + ".ssl.checkserveridentity", Boolean.toString(!insecure));
properties.put("mail." + protocol + ".ssl.trust", "*");
if (!BuildConfig.DEBUG)
properties.put("mail." + protocol + ".ssl.trust", "*");
properties.put("mail.smtps.starttls.enable", "false");
@ -180,6 +258,22 @@ public class MailService implements AutoCloseable {
this.listener = listener;
}
void setConfiguring() {
configuring = true;
}
void setFingerPrint(String value) {
fingerprint = value;
}
String getFingerPrint() throws CertificateEncodingException, NoSuchAlgorithmException {
return Helper.sha1(certificate.getEncoded());
}
boolean getTrusted() {
return trusted;
}
public void connect(EntityAccount account) throws MessagingException {
String password = connect(account.host, account.port, account.auth_type, account.user, account.password);
if (password != null) {

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