Potential fix for code scanning alert no. 7: Potentially unsafe call to strncat

[S-Parthiban-Selvaraj]

Potential fix for https://github.com/rdkcentral/wan-manager/security/code-scanning/7

To fix the problem, update all calls to strncat in wanmgr_telemetry_append_key_value so that the third argument is the amount of space left in MarkerArguments minus 1 (to ensure space for the null terminator). Specifically, for each append, calculate the remaining capacity as sizeof(MarkerArguments) - strlen(MarkerArguments) - 1, and pass this as the third argument to strncat.

Change only the calls in this function:

• Line 14: from strncat(MarkerArguments,WANMGR_T2_TELEMETRY_MARKER_ARG_DELIMITER,sizeof(MarkerArguments));
• Line 16: from strncat(MarkerArguments,key,sizeof(MarkerArguments));
• Line 17: from strncat(MarkerArguments,WANMGR_T2_TELEMETRY_MARKER_KEY_VALUE_DELIMITER,sizeof(MarkerArguments));
• Line 18: from strncat(MarkerArguments,value,sizeof(MarkerArguments));

Replace each with a calculation of remaining room, using a helper inline or local variable.

No new imports or methods are needed.

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Pull Request Overview

This PR addresses a security vulnerability related to unsafe strncat calls in the wanmgr_telemetry_append_key_value function. The fix ensures proper buffer size calculation by computing the remaining capacity before each string concatenation operation.

Key Changes:

• Introduced a remaining variable to track available buffer space
• Updated all four strncat calls to use calculated remaining capacity instead of total buffer size
• Each concatenation now properly accounts for space needed for the null terminator

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