Fix issues in the hidsim-plugin, which were identified by static code analysis

[jgru]

Dear Tamas,

this PR addresses the following issues, which were identified by Coverity, and tries to solve those:

• CID 350859: Fix usage of strdup(...) with unterminated string
• CID 350856: Fix resource leaks in get_display_dimensions(...)
• CID 350857: Fix resource leaks in get_display_dimensions(...)
• CID 350854: Fix unterminated strings in qmp_init_conn()
• CID 350852: Fix potential buffer overflow in get_display_dimensions(...)
• CID 350851: Fix submission of tainted data to usleep(...)
• CID 350855: Fix calculations with tainted scalar get_display_dimensions(...)
• CID 350860: Replace rand() with std::mt19937 to fix WEAK_CRYPTO-warning
• CID 350853: Replace rand() with std::mt19937 to fix WEAK_CRYPTO-warning
• CID 350858: Replace rand() with std::mt19937 to fix WEAK_CRYPTO-warning

Besides that, a few minor clean-ups have been performed.
Thank you already in advance for considering this PR.
I hope, that this patch will solve the problems introduced by #1245.

Best regards
Jan

[drakvuf-jenkins]

Can one of the admins verify this patch?

[tklengyel]

@drakvuf-jenkins This is OK to test

[tklengyel]

New defect(s) Reported-by: Coverity Scan
Showing 1 of 1 defect(s)


** CID 350879:    (USE_AFTER_FREE)
/src/plugins/hidsim/hid_injection.cpp: 228 in get_display_dimensions(qmp_connection *, dimensions *)()
/src/plugins/hidsim/hid_injection.cpp: 242 in get_display_dimensions(qmp_connection *, dimensions *)()


________________________________________________________________________________________________________
*** CID 350879:    (USE_AFTER_FREE)
/src/plugins/hidsim/hid_injection.cpp: 228 in get_display_dimensions(qmp_connection *, dimensions *)()
222             fclose(fr);
223             ret = -1;
224         }
225     
226         /* Retrieves screen dimensions by reading screen dump  */
227         uint32_t width = 0, height = 0;
>>>     CID 350879:    (USE_AFTER_FREE)
>>>     Calling "fscanf" uses file handle "fr" after closing it.
228         matches = fscanf(fr, "%" SCNd32 "%" SCNd32, &width, &height);
229     
230         if (matches != 2 )
231         {
232             fprintf(stderr, "[HIDSIM]: Error reading .ppm-files metadata\n");
233             fclose(fr);
/src/plugins/hidsim/hid_injection.cpp: 242 in get_display_dimensions(qmp_connection *, dimensions *)()
236     
237         /* Sanitizes read values; no need for a screen size larger than 65k */
238         dims->width = (uint16_t)(width > UINT16_MAX ? UINT16_MAX : width);
239         dims->height = (uint16_t)(height > UINT16_MAX ? UINT16_MAX : height);
240     
241         /* Clean up */
>>>     CID 350879:    (USE_AFTER_FREE)
>>>     Calling "fclose" uses file handle "fr" after closing it.
242         fclose(fr);
243     
244         /* Removes temp file generated by the screendump-command */
245         if (remove(tmp_path) != 0)
246             fprintf(stderr, "[HIDSIM]: Error deleting screen dump %s\n", tmp_path);
247     

[jgru]

New defect(s) Reported-by: Coverity Scan
Showing 1 of 1 defect(s)
[...]  

Addressed in PR #1256