Log message "Server url is invalid: %.*s" causes segmentation fault when connecting to empty URL

[pettineh]

Description

Calling _UA_Clientconnect function with completely empty address seems to cause a segmentation fault in the logging implementation. When the logger gets a message with content: "Server url is invalid: %.*s", the segmentation fault occurs when the va_list variables are being accessed. My guess is that the char pointer pointing to the message url is invalid when it is passed to the logger.

Background Information / Reproduction Steps

Now all this happens when the address given to _UA_Clientconnect function is completely empty null-terminated char array. Adding even a single whitespace character to the array fixes the issue.

To reproduce the issue, these are the lines of code I execute inside my OPC UA client implementing class: UA_Client client = UA_Client_new(); UA_ClientConfig config = UA_Client_getConfig(client); UA_ClientConfig_setDefault(config); config->logger.log = &myLogHandler; config->logger.context = this; char url[] = ""; UA_Client_connect(client, url); // Causes error log message: "Server url is invalid: %.*s"

Inside myLogHandler callback I call the strlen for the first variable returned by the va_list object holding the string arguments. This causes segfault when the log message is the one mentioned above.

Checklist

Please provide the following information:

• [x] open62541 Version (release number or git tag): 1.2
• [x] Other OPC UA SDKs used (client or server): client
• [x] Operating system: Ubuntu 18.04
• [ ] Logs (with UA_LOGLEVEL set as low as necessary) attached
• [ ] Wireshark network dump attached
• [x] Self-contained code example attached
• [x] Critical issue

[kimim]

compilation warning on my machine, maybe you need to pass url other than &url here.

tutorial_client_firststeps.c: In function 'main':
tutorial_client_firststeps.c:19:54: warning: passing argument 2 of 'UA_Client_connect' from incompatible pointer type [-Wincompatible-pointer-types]
   19 |     UA_StatusCode retval = UA_Client_connect(client, &url);
      |                                                      ^~~~
      |                                                      |
      |                                                      char (*)[1]
In file included from tutorial_client_firststeps.c:11:
open62541.h:28385:50: note: expected 'const char *' but argument is of type 'char (*)[1]'
28385 | UA_Client_connect(UA_Client *client, const char *endpointUrl);
      |                                      ~~~~~~~~~~~~^~~~~~~~~~~

[pettineh]

compilation warning on my machine, maybe you need to pass url other than &url here.

tutorial_client_firststeps.c: In function 'main':
tutorial_client_firststeps.c:19:54: warning: passing argument 2 of 'UA_Client_connect' from incompatible pointer type [-Wincompatible-pointer-types]
   19 |     UA_StatusCode retval = UA_Client_connect(client, &url);
      |                                                      ^~~~
      |                                                      |
      |                                                      char (*)[1]
In file included from tutorial_client_firststeps.c:11:
open62541.h:28385:50: note: expected 'const char *' but argument is of type 'char (*)[1]'
28385 | UA_Client_connect(UA_Client *client, const char *endpointUrl);
      |                                      ~~~~~~~~~~~~^~~~~~~~~~~

My bad. For the code example I simplified the code a bit. I originally passed the char * to the function. I will edit the code example in the original post.

[kimim]

If everything is fine, could you close this issue?

[pettineh]

@kimim Now you misunderstood, the issue still exists. The code example I gave was just bad.