fix: Bounds-check read_from_file restores with snprintf

[VedantMadane]

Summary

Bounds-check read_from_file restores with snprintf

Changes

• file_system.cpp: replace strcpy with bounds-checked snprintf (4)

Fixes #34

[RomanAlexandroff]

Hi and welcome!

In secret_verification() and data_integrity_check(), snprintf and sizeof will work just fine.

However, in read_from_file(), sizeof will not work as you expect because here 'output' is a pointer to the char array, not the array itself. Calling sizeof(output) will return the size of the pointer which on a 32-bit system is just 4 bytes, causing snprintf to always copy at most 3 characters + a nul-terminator.

Instead, you've got to calculate the size to copy first and then pass it into read_from_file() e.g. like this:
read_from_file(const char* file_name, char* output, size_t output_size)

[VedantMadane]

Thank you for the review and explanation! I have updated
ead_from_file() to accept size_t output_size, updated the header declaration, and passed the explicit destination buffer sizes (sizeof(rtc_g.Secret) and sizeof(rtc_g.chat_id)) from
estore_data_value().