Soft Disable AES-CBC

1. By default, soft disable AES-CBC. It isn't offered as a default
   encrypt algorithm, but may be set at runtime.
2. Add guard where AES-CBC can be added back as a default.
3. Add option to example client to run it with a custom encrypt
   algorithm list.

Author: ejohnstown

examples/client/client.c

@@ -651,6 +651,7 @@ THREAD_RETURN WOLFSSH_THREAD client_test(void* args)
     const char* cmd      = NULL;
     const char* privKeyName = NULL;
     const char* keyList = NULL;
+    const char* cipherList = NULL;
     byte imExit = 0;
     byte listAlgos = 0;
     byte nonBlock = 0;
@@ -669,7 +670,7 @@ THREAD_RETURN WOLFSSH_THREAD client_test(void* args)
 
     (void)keepOpen;
 
-    while ((ch = mygetopt(argc, argv, "?ac:h:i:j:p:tu:xzNP:RJ:A:XeEk:qK:")) != -1) {
+    while ((ch = mygetopt(argc, argv, "?ac:C:h:i:j:p:tu:xzNP:RJ:A:XeEk:qK:")) != -1) {
         switch (ch) {
             case 'h':
                 host = myoptarg;
@@ -750,6 +751,10 @@ THREAD_RETURN WOLFSSH_THREAD client_test(void* args)
                 keyList = myoptarg;
                 break;
 
+            case 'C':
+                cipherList = myoptarg;
+                break;
+
         #if !defined(SINGLE_THREADED) && !defined(WOLFSSL_NUCLEUS)
             case 'c':
                 cmd = myoptarg;
@@ -841,6 +846,11 @@ THREAD_RETURN WOLFSSH_THREAD client_test(void* args)
             err_sys("Error setting key list.\n");
         }
     }
+    if (cipherList) {
+        if (wolfSSH_CTX_SetAlgoListCipher(ctx, cipherList) != WS_SUCCESS) {
+            err_sys("Error setting cipher list.\n");
+        }
+    }
 
     if (((func_args*)args)->user_auth == NULL)
         wolfSSH_SetUserAuth(ctx, ClientUserAuth);

src/internal.c

@@ -147,6 +147,11 @@
   WOLFSSH_NO_NISTP256_MLKEM768_SHA256
     Set when ML-KEM is disabled in wolfssl. Set to disable use of ECDHE with
     prime NISTP256 hybridized with post-quantum ML-KEM 768.
+  WOLFSSH_NO_AES_CBC_SOFT_DISABLE
+    AES-CBC is normally soft-disabled. The default configuration will not
+    advertise the availability of AES-CBC algorithms during KEX. AES-CBC
+    algorithms still work. Setting this flag will advertise AES-CBC
+    algorithms during KEX by default.
   WOLFSSH_NO_AES_CBC
     Set when AES or AES-CBC are disabled. Set to disable use of AES-CBC
     encryption.
@@ -804,10 +809,12 @@ static const char cannedEncAlgoNames[] =
     "aes128-ctr,"
 #endif
 #if !defined(WOLFSSH_NO_AES_CBC)
-    "aes256-cbc,"
-    "aes192-cbc,"
-    "aes128-cbc,"
-#endif
+    #if defined(WOLFSSH_NO_AES_CBC_SOFT_DISABLE)
+        "aes256-cbc,"
+        "aes192-cbc,"
+        "aes128-cbc,"
+    #endif
+#endif /* WOLFSSH_NO_AES_CBC */
     "";
 
 static const char cannedMacAlgoNames[] =

tests/kex.c

@@ -175,7 +175,8 @@ static int wolfSSH_wolfSSH_Group16_512(void)
           sA[10], sA[11] };
     char cA[NUMARGS][ARGLEN];
     char *clientArgv[NUMARGS] =
-        { cA[0], cA[1], cA[2], cA[3], cA[4] };
+        { cA[0], cA[1], cA[2], cA[3], cA[4], cA[5], cA[6], cA[7], cA[8], cA[9],
+          cA[10], cA[11] };
     int serverArgc = 0;
     int clientArgc = 0;
 
@@ -227,6 +228,8 @@ static int wolfSSH_wolfSSH_Group16_512(void)
     WSTRNCPY(cA[clientArgc++], "client", ARGLEN);
     WSTRNCPY(cA[clientArgc++], "-u", ARGLEN);
     WSTRNCPY(cA[clientArgc++], "jill", ARGLEN);
+    WSTRNCPY(cA[clientArgc++], "-C", ARGLEN);
+    WSTRNCPY(cA[clientArgc++], "aes256-cbc", ARGLEN);
     #if !defined(USE_WINDOWS_API) && !defined(WOLFSSH_ZEPHYR)
         WSTRNCPY(cA[clientArgc++], "-p", ARGLEN);
         WSNPRINTF(cA[clientArgc++], ARGLEN, "%d", ready.port);