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process-events.md: Description of Process GUIDs is not right.

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Assessment

Difficulty
3/5
Estimated time
1-2 days
Newbie friendliness
42/100
Issue type
Documentation
Clarity
Mostly clear
Activity status
Stale
Tech stack
c
Domain
documentation

Research direction

Start with process-events.md and compare its Process GUID description with GenerateUniqueId in sysmonCommon/eventsCommon.h and set_ProcCreate_info in ebpfKern/sysmonProcCreate.c. Investigate the unresolved Windows behavior if possible, then update the documentation to accurately distinguish the machine ID, process start time, and process start key from the process ID.

Written by the indexing model from the issue text.

Description

Looking at the Sysmon/Linux sources, GUIDs are constructed by concatenating the "machine id", the start time of the process (UNIX-style, seconds since 1970-1-1), and a "process start key" which is not defined in the userspace component (function GenerateUniqueId in sysmonCommon/eventsCommon.h):

	*(DWORD*) pResult = machineId;
	pResult += sizeof(DWORD);
	*(DWORD*) pResult = seconds;
	pResult += sizeof(DWORD);
	*(DWORD64*) pResult = ProcessStartKey;

The "process key" is taken from m_EventBody.m_ProcessCreateEvent.m_ProcessKey which for Linux is created in the eBPF code (set_ProcCreate_info in ebpfKern/sysmonProcCreate.c):

    // get the process key - this is the end of the text segment currently as it should be
    // a) randomised for a PIE executable; and
    // b) dependent on the amount of code in the process
    event->m_ProcessKey = (uint64_t)derefPtr(task, config->offsets.mm_end_code);

I'm still in the process of looking at Sysmon/Windows with a disassembler, so I can't yet speak to what happens there. However, from the logs I have looked at, I don't recognize the process id as part of the process GUID.

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