// Kernel security contexts. Contexts are immutable authority sets carried by processes and delegated only by attenuation.

#include <string.h>
#include <kernel/se_security.h>
#include <kernel/ke_id.h>
#include <kernel/ke_process.h>
#include <kernel/ob_object.h>

static KE_ID_ALLOCATOR gSecurityIds = KE_ID_ALLOCATOR_INIT(1u);
static SECURITY_CONTEXT* gRootSecurityContext;

// Destroys one non-root security context after its last object reference disappears.
static void KiSecurityContextDestroy(OBJECT* object) {
    (void)object;
}

// Allocates and initializes one immutable security context object.
static KSTATUS KiCreateSecurityContext(SYS_PRIVILEGES effectivePrivileges,
                                       SYS_PRIVILEGES delegablePrivileges,
                                       SECURITY_CONTEXT** contextOut) {
    if (!contextOut)
        return NTLSTATUS_INVALID_PARAMETER;
    *contextOut = (SECURITY_CONTEXT*)0;

    if ((effectivePrivileges & ~SYS_PRIV_ALL) != 0 ||
        (delegablePrivileges & ~SYS_PRIV_ALL) != 0)
        return NTLSTATUS_INVALID_PARAMETER;
    if ((delegablePrivileges & ~effectivePrivileges) != 0)
        return NTLSTATUS_ACCESS_DENIED;

    SECURITY_CONTEXT* context = (SECURITY_CONTEXT*)ObAllocateObject(ObjectTypeSecurityContext,
                                                                     sizeof(SECURITY_CONTEXT));
    if (!context)
        return NTLSTATUS_NO_MEMORY;
    context->Header.Destroy = KiSecurityContextDestroy;

    KSTATUS status = KeAllocateId32(&gSecurityIds, &context->SecurityId);
    if (!KSUCCESS(status)) {
        ObDereferenceObject(&context->Header);
        return status;
    }

    context->EffectivePrivileges = effectivePrivileges;
    context->DelegablePrivileges = delegablePrivileges;
    context->Flags = SYS_SECURITY_CONTEXT_FLAG_NONE;
    *contextOut = context;
    return NTLSTATUS_SUCCESS;
}

// Initializes the root context exactly once before any process is created.
KSTATUS SeInitializeSecurity(void) {
    if (gRootSecurityContext)
        return NTLSTATUS_SUCCESS;

    SECURITY_CONTEXT* context = (SECURITY_CONTEXT*)0;
    KSTATUS status = KiCreateSecurityContext(SYS_PRIV_ALL,
                                              SYS_PRIV_ALL,
                                              &context);
    if (!KSUCCESS(status))
        return status;

    gRootSecurityContext = context;
    return NTLSTATUS_SUCCESS;
}

// Returns the permanently referenced bootstrap root context.
SECURITY_CONTEXT* SeGetRootSecurityContext(void) {
    return gRootSecurityContext;
}

// Derives one child context whose effective and delegable authority are subsets of the source delegable sets.
KSTATUS SeDeriveSecurityContext(SECURITY_CONTEXT* source,
                                SYS_PRIVILEGES effectivePrivileges,
                                SYS_PRIVILEGES delegablePrivileges,
                                SECURITY_CONTEXT** contextOut) {
    if (!source || !contextOut)
        return NTLSTATUS_INVALID_PARAMETER;

    if ((effectivePrivileges & ~source->DelegablePrivileges) != 0 ||
        (delegablePrivileges & ~source->DelegablePrivileges) != 0)
        return NTLSTATUS_ACCESS_DENIED;

    return KiCreateSecurityContext(effectivePrivileges,
                                   delegablePrivileges,
                                   contextOut);
}

// Tests one process's immutable effective privilege mask.
bool SeProcessHasPrivilege(const struct PROCESS* process, SYS_PRIVILEGES privileges) {
    if (!process || !process->SecurityContext)
        return false;
    return (process->SecurityContext->EffectivePrivileges & privileges) == privileges;
}

// Exports immutable context metadata to one public structure.
void SeQuerySecurityContext(const SECURITY_CONTEXT* context, SYS_SECURITY_CONTEXT_INFO* infoOut) {
    if (!context || !infoOut)
        return;

    memset(infoOut, 0, sizeof(*infoOut));
    infoOut->Size = sizeof(*infoOut);
    infoOut->SecurityId = context->SecurityId;
    infoOut->EffectivePrivileges = context->EffectivePrivileges;
    infoOut->DelegablePrivileges = context->DelegablePrivileges;
    infoOut->Flags = context->Flags;
}