Install libsodium from source

.ci/install.sh

@@ -12,11 +12,20 @@ if [ $TRAVIS_OS_NAME == linux ]; then
     export CXX=${CXX_VERSION}
     export CC=${CC_VERSION}
 
-    sudo add-apt-repository -y ppa:chris-lea/libsodium
     sudo apt-get update -qq
-    sudo apt-get install -qq -y libsodium-dev
     sudo apt-get remove -y cmake
 
+    # Build & install libsodium for source.
+    mkdir -p libsodium && pushd libsodium
+    curl -L \
+        https://download.libsodium.org/libsodium/releases/libsodium-${LIBSODIUM_VERSION}.tar.gz \
+        -o libsodium-${LIBSODIUM_VERSION}.tar.gz
+    tar xfz libsodium-${LIBSODIUM_VERSION}.tar.gz
+    pushd libsodium-${LIBSODIUM_VERSION}/
+    ./configure && make && make check && make install         
+    popd
+    popd
+
     wget https://cmake.org/files/v3.11/cmake-3.11.4-Linux-x86_64.sh
     sudo sh cmake-3.11.4-Linux-x86_64.sh  --skip-license  --prefix=/usr/local
     export PATH="/usr/local/bin:$PATH"

.travis.yml

@@ -27,6 +27,7 @@ matrix:
         - TESTS=ON
         - COVERAGE=ON
         - USE_BUNDLED_BOOST=ON
+        - LIBSODIUM_VERSION=1.0.16
       addons:
         apt:
           sources:
@@ -41,6 +42,7 @@ matrix:
         - CC_VERSION=clang-6.0
         - TESTS=ON
         - USE_BUNDLED_BOOST=ON
+        - LIBSODIUM_VERSION=1.0.16
       addons:
         apt:
           sources: