chacha: fix build for mbedTLS

Fix the build for mbedTLS:
 * set HAVE_CHACHA for non-mbedTLS builds
 * only compile chachapoly.c when HAVE_CHACHA
 * use empty CHACHA20 in src/kex.c unless HAVE_CHACHA

Signed-off-by: Jon Simons <jon@jonsimons.org>
Reviewed-by: Andreas Schneider <asn@cryptomilk.org>

src/CMakeLists.txt

@@ -122,7 +122,6 @@ set(libssh_SRCS
   bignum.c
   buffer.c
   callbacks.c
-  chachapoly.c
   channels.c
   client.c
   config.c
@@ -167,6 +166,13 @@ set(libssh_SRCS
   external/sc25519.c
 )
 
+if (NOT WITH_MBEDTLS)
+    set(libssh_SRCS
+        ${libssh_SRCS}
+        chachapoly.c
+       )
+endif (NOT WITH_MBEDTLS)
+
 if (WITH_GCRYPT)
     set(libssh_SRCS
         ${libssh_SRCS}

src/kex.c

@@ -95,7 +95,11 @@
 #define ECDH ""
 #endif
 
+#ifdef    HAVE_CHACHA
 #define CHACHA20 "chacha20-poly1305@openssh.com,"
+#else  /* HAVE_CHACHA */
+#define CHACHA20
+#endif /* HAVE_CHACHA */
 
 #define KEY_EXCHANGE CURVE25519 ECDH "diffie-hellman-group14-sha1,diffie-hellman-group1-sha1"
 #define KEX_METHODS_SIZE 10