Date: Tue, 17 Mar 2020 17:05:55 -0700 From: John Baldwin <jhb@FreeBSD.org> To: Ian Lepore <ian@freebsd.org>, Conrad Meyer <cem@FreeBSD.org>, src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-head@freebsd.org Subject: Re: svn commit: r359053 - head/sys/kern Message-ID: <c1f41292-c83a-2f79-66e4-394ed94d448a@FreeBSD.org> In-Reply-To: <047c4edb4ff9fa6c40be6492c2f082e374f7a941.camel@freebsd.org> References: <202003172227.02HMRHLM086023@repo.freebsd.org> <047c4edb4ff9fa6c40be6492c2f082e374f7a941.camel@freebsd.org>
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On 3/17/20 3:36 PM, Ian Lepore wrote: > On Tue, 2020-03-17 at 22:27 +0000, Conrad Meyer wrote: >> Author: cem >> Date: Tue Mar 17 22:27:16 2020 >> New Revision: 359053 >> URL: https://svnweb.freebsd.org/changeset/base/359053 >> >> Log: >> Implement sysctl kern.boot_id >> >> Boot IDs are random, opaque 128-bit identifiers that distinguish distinct >> system boots. A new ID is generated each time the system boots. Unlike >> kern.boottime, the value is not modified by NTP adjustments. It remains fixed >> until the machine is restarted. >> >> PR: 244867 >> Reported by: Ricardo Fraile <rfraile AT rfraile.eu> >> MFC after: I do not intend to, but feel free >> >> Modified: >> head/sys/kern/kern_mib.c >> >> Modified: head/sys/kern/kern_mib.c >> ============================================================================== >> --- head/sys/kern/kern_mib.c Tue Mar 17 21:29:03 2020 (r359052) >> +++ head/sys/kern/kern_mib.c Tue Mar 17 22:27:16 2020 (r359053) >> @@ -448,6 +448,32 @@ SYSCTL_PROC(_kern, KERN_HOSTID, hostid, >> CTLTYPE_ULONG | CTLFLAG_RW | CTLFLAG_PRISON | CTLFLAG_MPSAFE | CTLFLAG_CAPRD, >> NULL, 0, sysctl_hostid, "LU", "Host ID"); >> >> +static struct mtx bootid_lk; >> +MTX_SYSINIT(bootid_lock, &bootid_lk, "bootid generator lock", MTX_DEF); >> + >> +static int >> +sysctl_bootid(SYSCTL_HANDLER_ARGS) >> +{ >> + static uint8_t boot_id[16]; >> + static bool initialized = false; >> + >> + mtx_lock(&bootid_lk); >> + if (!initialized) { >> + if (!is_random_seeded()) { >> + mtx_unlock(&bootid_lk); >> + return (ENXIO); >> + } >> + arc4random_buf(boot_id, sizeof(boot_id)); >> + initialized = true; >> + } >> + mtx_unlock(&bootid_lk); >> + >> + return (SYSCTL_OUT(req, boot_id, sizeof(boot_id))); >> +} >> +SYSCTL_PROC(_kern, OID_AUTO, boot_id, >> + CTLTYPE_STRUCT | CTLFLAG_RD | CTLFLAG_MPSAFE | CTLFLAG_CAPRD, >> + NULL, 0, sysctl_bootid, "", "Random boot ID"); >> + >> /* >> * The osrelease string is copied from the global (osrelease in vers.c) into >> * prison0 by a sysinit and is inherited by child jails if not changed at jail > > This seems a bit complex. Why run a sysinit to init a mutex so that > you can safely do a lazy init of boot_id? Seems like it would be much > easier to just use a sysinit at SI_SUB_LAST to init boot_id before > sysctl can reference it. Presumably you may not have enough entropy by SI_SUB_LAST to generate it? -- John Baldwin
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