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Change the way we harden SSL/TLS sockets 

Blacklist a couple of weak ciphers, bring known ones in a defined order and sort unknown
ciphers at the end. Also re-enable SSLv3 because it's still used a lot.
This commit is contained in:
cketti 2013-12-04 04:09:44 +01:00
parent 448a80e96a
commit 3fd7470d68
1 changed files with 69 additions and 32 deletions
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101
src/com/fsck/k9/net/ssl/TrustedSocketFactory.java
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@ -13,46 +13,67 @@ import java.util.*;
/**
* Filter and reorder list of cipher suites and TLS versions.
*
* <p>
* See: <a href="http://op-co.de/blog/posts/android_ssl_downgrade/">http://op-co.de/blog/posts/android_ssl_downgrade/</a>
* </p>
*/
public class TrustedSocketFactory {
protected static final String ENABLED_CIPHERS[];
protected static final String ENABLED_PROTOCOLS[];
static {
String preferredCiphers[] = {
"TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA",
"TLS_ECDHE_ECDSA_WITH_AES_128_CBC_SHA",
// Order taken from OpenSSL 1.0.1c
protected static final String ORDERED_KNOWN_CIPHERS[] = {
"TLS_ECDHE_RSA_WITH_AES_256_CBC_SHA",
"TLS_ECDHE_ECDSA_WITH_AES_256_CBC_SHA",
"TLS_DHE_RSA_WITH_AES_128_CBC_SHA",
"TLS_DHE_RSA_WITH_AES_256_CBC_SHA",
"TLS_DHE_DSS_WITH_AES_256_CBC_SHA",
"TLS_ECDH_RSA_WITH_AES_256_CBC_SHA",
"TLS_ECDH_ECDSA_WITH_AES_256_CBC_SHA",
"TLS_RSA_WITH_AES_256_CBC_SHA",
"TLS_ECDHE_RSA_WITH_3DES_EDE_CBC_SHA",
"TLS_ECDHE_ECDSA_WITH_3DES_EDE_CBC_SHA",
"TLS_ECDH_RSA_WITH_3DES_EDE_CBC_SHA",
"TLS_ECDH_ECDSA_WITH_3DES_EDE_CBC_SHA",
"SSL_RSA_WITH_3DES_EDE_CBC_SHA",
"TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA",
"TLS_ECDHE_ECDSA_WITH_AES_128_CBC_SHA",
"TLS_DHE_RSA_WITH_AES_128_CBC_SHA",
"TLS_DHE_DSS_WITH_AES_128_CBC_SHA",
"TLS_ECDH_RSA_WITH_AES_128_CBC_SHA",
"TLS_ECDH_ECDSA_WITH_AES_128_CBC_SHA",
"TLS_RSA_WITH_AES_128_CBC_SHA",
"TLS_ECDHE_RSA_WITH_RC4_128_SHA",
"TLS_ECDHE_ECDSA_WITH_RC4_128_SHA",
"TLS_RSA_WITH_AES_128_CBC_SHA",
"TLS_RSA_WITH_AES_256_CBC_SHA",
"SSL_RSA_WITH_3DES_EDE_CBC_SHA",
"TLS_ECDH_RSA_WITH_RC4_128_SHA",
"TLS_ECDH_ECDSA_WITH_RC4_128_SHA",
"SSL_DHE_RSA_WITH_3DES_EDE_CBC_SHA",
"SSL_DHE_DSS_WITH_3DES_EDE_CBC_SHA",
"SSL_RSA_WITH_RC4_128_SHA",
"SSL_RSA_WITH_RC4_128_MD5",
};
String preferredProtocols[] = {
"TLSv1.2", "TLSv1.1", "TLSv1"
};
};
String[] supportedCiphers = null;
String[] supportedProtocols = null;
protected static final String[] BLACKLISTED_CIPHERS = {
"SSL_RSA_WITH_DES_CBC_SHA",
"SSL_DHE_RSA_WITH_DES_CBC_SHA",
"SSL_DHE_DSS_WITH_DES_CBC_SHA",
"SSL_RSA_EXPORT_WITH_RC4_40_MD5",
"SSL_RSA_EXPORT_WITH_DES40_CBC_SHA",
"SSL_DHE_RSA_EXPORT_WITH_DES40_CBC_SHA",
"SSL_DHE_DSS_EXPORT_WITH_DES40_CBC_SHA",
};
protected static final String ORDERED_KNOWN_PROTOCOLS[] = {
"TLSv1.2", "TLSv1.1", "TLSv1", "SSLv3"
};
static {
String[] enabledCiphers = null;
String[] enabledProtocols = null;
try {
SSLContext sslContext = SSLContext.getInstance("TLS");
sslContext.init(null, null, new SecureRandom());
SSLSocketFactory sf = sslContext.getSocketFactory();
supportedCiphers = sf.getSupportedCipherSuites();
SSLSocket sock = (SSLSocket)sf.createSocket();
supportedProtocols = sock.getSupportedProtocols();
SSLSocket sock = (SSLSocket) sf.createSocket();
enabledCiphers = sock.getEnabledCipherSuites();
enabledProtocols = sock.getEnabledProtocols();
} catch (IOException ioe) {
ioe.printStackTrace();
} catch (KeyManagementException kme) {
@ -61,21 +82,37 @@ public class TrustedSocketFactory {
nsae.printStackTrace();
}
ENABLED_CIPHERS = supportedCiphers == null ? null :
filterBySupport(preferredCiphers, supportedCiphers);
ENABLED_PROTOCOLS = supportedProtocols == null ? null :
filterBySupport(preferredProtocols, supportedProtocols);
ENABLED_CIPHERS = (enabledCiphers == null) ? null :
reorder(enabledCiphers, ORDERED_KNOWN_CIPHERS, BLACKLISTED_CIPHERS);
ENABLED_PROTOCOLS = (enabledProtocols == null) ? null :
reorder(enabledProtocols, ORDERED_KNOWN_PROTOCOLS, null);
}
protected static String[] filterBySupport(String[] preferred, String[] supported) {
List<String> enabled = new ArrayList<String>();
Set<String> available = new HashSet<String>();
Collections.addAll(available, supported);
protected static String[] reorder(String[] enabled, String[] known, String[] blacklisted) {
List<String> unknown = new ArrayList<String>();
Collections.addAll(unknown, enabled);
for (String item : preferred) {
if (available.contains(item)) enabled.add(item);
// Remove blacklisted items
if (blacklisted != null) {
for (String item : blacklisted) {
unknown.remove(item);
}
}
return enabled.toArray(new String[enabled.size()]);
// Order known items
List<String> result = new ArrayList<String>();
for (String item : known) {
if (unknown.remove(item)) {
result.add(item);
}
}
// Add unknown items at the end. This way security won't get worse when unknown ciphers
// start showing up in the future.
result.addAll(unknown);
return result.toArray(new String[result.size()]);
}
public static Socket createSocket(SSLContext sslContext) throws IOException {