UI_construct_prompt: check for NULL when allocating prompt

Signed-off-by: NKurt Roeckx <kurt@openssl.org>
Reviewed-by: NDr. Stephen Henson <steve@openssl.org>

crypto/ui/ui_lib.c

@@ -431,6 +431,8 @@ char *UI_construct_prompt(UI *ui, const char *object_desc,
 		len += sizeof(prompt3) - 1;
 
 		prompt = (char *)OPENSSL_malloc(len + 1);
+		if (prompt == NULL)
+			return NULL;
 		BUF_strlcpy(prompt, prompt1, len + 1);
 		BUF_strlcat(prompt, object_desc, len + 1);
 		if (object_name)