From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: by sourceware.org (Postfix, from userid 48) id 4CA243858027; Mon, 8 Aug 2022 12:38:40 +0000 (GMT) DKIM-Filter: OpenDKIM Filter v2.11.0 sourceware.org 4CA243858027 From: "adhemerval.zanella at linaro dot org" To: glibc-bugs@sourceware.org Subject: [Bug libc/29437] arc4random is too slow Date: Mon, 08 Aug 2022 12:38:40 +0000 X-Bugzilla-Reason: CC X-Bugzilla-Type: changed X-Bugzilla-Watch-Reason: None X-Bugzilla-Product: glibc X-Bugzilla-Component: libc X-Bugzilla-Version: 2.36 X-Bugzilla-Keywords: X-Bugzilla-Severity: normal X-Bugzilla-Who: adhemerval.zanella at linaro dot org X-Bugzilla-Status: NEW X-Bugzilla-Resolution: X-Bugzilla-Priority: P2 X-Bugzilla-Assigned-To: unassigned at sourceware dot org X-Bugzilla-Target-Milestone: --- X-Bugzilla-Flags: security- X-Bugzilla-Changed-Fields: Message-ID: In-Reply-To: References: Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Bugzilla-URL: http://sourceware.org/bugzilla/ Auto-Submitted: auto-generated MIME-Version: 1.0 X-BeenThere: glibc-bugs@sourceware.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Glibc-bugs mailing list List-Unsubscribe: , List-Archive: List-Help: List-Subscribe: , X-List-Received-Date: Mon, 08 Aug 2022 12:38:40 -0000 https://sourceware.org/bugzilla/show_bug.cgi?id=3D29437 --- Comment #9 from Adhemerval Zanella --- (In reply to Florian Weimer from comment #7) > (In reply to Adhemerval Zanella from comment #6) > > For example, when a virtual machine is forked, restored, or duplicated,= it's > > imperative that the RNG doesn't generate the same outputs. For this rea= son, > > there's a small protocol between hypervisors and the kernel that indica= tes > > this has happened, alongside some ID, which the RNG uses to reseed > > immediately, so as not to return the same numbers. >=20 > Except that this doesn't work because if the suspend/resume happens a lit= tle > bit later, the unprotected application buffer to which the random data has > been written is restore multiple times. So clearly the actual rules around > this are different and much more complicated. I am not following, which buffer are you referring? The kernel one applicat= ion will be poll with arc4random/getrandom or the possible one maintained by application itself with a previous arc4random call? For the latter, it is an application vulnerability where it is caching CSRNG state. --=20 You are receiving this mail because: You are on the CC list for the bug.=