check if the ciphers are supported by m2crypto before using them

.travis.yml

@@ -15,6 +15,7 @@ addons:
   apt_packages:
     # needed for M2Crypto
     - swig
+    - libssl-dev
     # needed for GMPY
     - libgmp-dev
 before_cache:
@@ -46,6 +47,8 @@ jobs:
       env: TACKPY=true
     - python: 3.4
       env: TACKPY=true
+    - python: 2.6
+      env: M2CRYPTO_OLD=true
     - python: 2.7
       env: M2CRYPTO=true
     - python: 3.5
@@ -135,6 +138,7 @@ install:
   - if [[ -e build-requirements-${TRAVIS_PYTHON_VERSION}.txt ]]; then travis_retry pip install -r build-requirements-${TRAVIS_PYTHON_VERSION}.txt; else travis_retry pip install -r build-requirements.txt; fi
   - if [[ $TACKPY == 'true' ]]; then travis_retry pip install tackpy; fi
   - if [[ $M2CRYPTO == 'true' ]]; then travis_retry pip install --pre m2crypto; fi
+  - if [[ $M2CRYPTO_OLD == 'true' ]]; then travis_retry pip install m2crypto==0.24.0; fi
   - if [[ $PYCRYPTO == 'true' ]]; then travis_retry pip install pycrypto; fi
   - if [[ $PYCRYPTODOME == 'true' ]]; then travis_retry pip install pycryptodome; fi
   - if [[ $GMPY == 'true' ]]; then travis_retry pip install gmpy; fi

tlslite/utils/cryptomath.py

@@ -27,9 +27,13 @@
 # **************************************************************************
 
 # Try to load M2Crypto/OpenSSL
+# pylint: disable=invalid-name
 try:
     from M2Crypto import m2
     m2cryptoLoaded = True
+    M2CRYPTO_AES_CTR = False
+    if hasattr(m2, 'aes_192_ctr'):
+        M2CRYPTO_AES_CTR = True
 
     try:
         with open('/proc/sys/crypto/fips_enabled', 'r') as fipsFile:
@@ -39,8 +43,13 @@
         # looks like we're running in container, likely not FIPS mode
         m2cryptoLoaded = True
 
+    # If AES-CBC is not available, don't use m2crypto
+    if not hasattr(m2, 'aes_192_cbc'):
+        m2cryptoLoaded = False
+
 except ImportError:
     m2cryptoLoaded = False
+# pylint: enable=invalid-name
 
 #Try to load GMPY
 try:

tlslite/utils/openssl_aes.py

@@ -5,16 +5,24 @@
 
 from .cryptomath import *
 from .aes import *
+from .python_aes import Python_AES_CTR
 
 if m2cryptoLoaded:
 
     def new(key, mode, IV):
         # IV argument name is a part of the interface
         # pylint: disable=invalid-name
+        """
+        Try using AES CTR from m2crpyto,
+        if it is not available fall back to the
+        python implementation.
+        """
         if mode == 2:
             return OpenSSL_AES(key, mode, IV)
         elif mode == 6:
-            return OpenSSL_CTR(key, mode, IV)
+            if M2CRYPTO_AES_CTR:
+                return OpenSSL_CTR(key, mode, IV)
+            return Python_AES_CTR(key, mode, IV)
         else:
             raise NotImplementedError()