From 67f8ed44bd7241556a7cb1eb2aee2dda4cbbbf4e Mon Sep 17 00:00:00 2001 From: Boris Wachtmeister Date: Sat, 7 Mar 2015 15:36:31 +0100 Subject: [PATCH] disable all really weak cipher suites With #959 all ciphers of the platform were enabled, but this also includes several suites that are considered as very weak, even down to NULL- and anon-ciphers which disable completely disable encryption and/or authentication. Especially the anon-ciphers could be easily used for a mitm-attack. To remove all weak ciphers a blacklist with patterns of cipher-names was added to Config.java. The blacklist is based on the "mandatory discards" that Mozilla suggests to not use for TLS-servers because they are weak or known to be broken. https://wiki.mozilla.org/Security/Server_Side_TLS#Mandatory_discards --- src/main/java/eu/siacs/conversations/Config.java | 9 +++++++++ .../siacs/conversations/utils/CryptoHelper.java | 16 ++++++++++++++++ 2 files changed, 25 insertions(+) diff --git a/src/main/java/eu/siacs/conversations/Config.java b/src/main/java/eu/siacs/conversations/Config.java index 2b9cee9fd..f38bcbfc5 100644 --- a/src/main/java/eu/siacs/conversations/Config.java +++ b/src/main/java/eu/siacs/conversations/Config.java @@ -64,6 +64,15 @@ public final class Config { "TLS_RSA_WITH_AES_256_CBC_SHA", }; + public static final String WEAK_CIPHER_PATTERNS[] = { + "_NULL_", + "_EXPORT_", + "_anon_", + "_RC4_", + "_DES_", + "_MD5", + }; + private Config() { } diff --git a/src/main/java/eu/siacs/conversations/utils/CryptoHelper.java b/src/main/java/eu/siacs/conversations/utils/CryptoHelper.java index 31fe2c116..eb7e2c3c6 100644 --- a/src/main/java/eu/siacs/conversations/utils/CryptoHelper.java +++ b/src/main/java/eu/siacs/conversations/utils/CryptoHelper.java @@ -4,6 +4,7 @@ import java.security.SecureRandom; import java.text.Normalizer; import java.util.Arrays; import java.util.Collection; +import java.util.Iterator; import java.util.LinkedHashSet; import java.util.List; @@ -103,6 +104,21 @@ public final class CryptoHelper { final List platformCiphers = Arrays.asList(platformSupportedCipherSuites); cipherSuites.retainAll(platformCiphers); cipherSuites.addAll(platformCiphers); + filterWeakCipherSuites(cipherSuites); return cipherSuites.toArray(new String[cipherSuites.size()]); } + + private static void filterWeakCipherSuites(final Collection cipherSuites) { + final Iterator it = cipherSuites.iterator(); + while (it.hasNext()) { + String cipherName = it.next(); + // remove all ciphers with no or very weak encryption or no authentication + for (String weakCipherPattern : Config.WEAK_CIPHER_PATTERNS) { + if (cipherName.contains(weakCipherPattern)) { + it.remove(); + break; + } + } + } + } }