From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from ffbox0-bg.mplayerhq.hu (ffbox0-bg.ffmpeg.org [79.124.17.100]) by master.gitmailbox.com (Postfix) with ESMTP id 010D145D0D for ; Tue, 4 Jul 2023 15:31:19 +0000 (UTC) Received: from [127.0.1.1] (localhost [127.0.0.1]) by ffbox0-bg.mplayerhq.hu (Postfix) with ESMTP id 8297F68C5E2; Tue, 4 Jul 2023 18:31:16 +0300 (EEST) Received: from mail0.khirnov.net (red.khirnov.net [176.97.15.12]) by ffbox0-bg.mplayerhq.hu (Postfix) with ESMTPS id 45D9268C5DC for ; Tue, 4 Jul 2023 18:31:10 +0300 (EEST) Received: from localhost (localhost [IPv6:::1]) by mail0.khirnov.net (Postfix) with ESMTP id 9B1A02404EC for ; Tue, 4 Jul 2023 17:31:09 +0200 (CEST) Received: from mail0.khirnov.net ([IPv6:::1]) by localhost (mail0.khirnov.net [IPv6:::1]) (amavisd-new, port 10024) with ESMTP id hi7ayuTeKi-6 for ; Tue, 4 Jul 2023 17:31:04 +0200 (CEST) Received: from lain.khirnov.net (lain.khirnov.net [IPv6:2001:67c:1138:4306::3]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256 client-signature RSA-PSS (2048 bits) client-digest SHA256) (Client CN "lain.khirnov.net", Issuer "smtp.khirnov.net SMTP CA" (verified OK)) by mail0.khirnov.net (Postfix) with ESMTPS id 7E8502404EA for ; Tue, 4 Jul 2023 17:31:04 +0200 (CEST) Received: by lain.khirnov.net (Postfix, from userid 1000) id 60F5B1601B2; Tue, 4 Jul 2023 17:31:04 +0200 (CEST) From: Anton Khirnov To: FFmpeg development discussions and patches In-Reply-To: <4cc08bc5-82a4-d7d1-4183-710676cb36c3@gmail.com> References: <20230702193010.11654-1-cus@passwd.hu> <54fe8899-d250-8d62-1157-621deb546040@gmail.com> <168841533190.542.8113031316523716543@lain.khirnov.net> <4b0740-7b32-415b-47af-3199463854b@passwd.hu> <168841859463.9711.12513000520212201640@lain.khirnov.net> <20230703235057.GQ1093384@pb2> <168845004614.542.18132678959456829324@lain.khirnov.net> <4cc08bc5-82a4-d7d1-4183-710676cb36c3@gmail.com> Mail-Followup-To: FFmpeg development discussions and patches Date: Tue, 04 Jul 2023 17:31:04 +0200 Message-ID: <168848466435.9711.13206835239340503825@lain.khirnov.net> User-Agent: alot/0.8.1 MIME-Version: 1.0 Subject: Re: [FFmpeg-devel] [PATCH 1/2] avformat/hlsenc: fall back to av_get_random_seed() when generating AES128 key X-BeenThere: ffmpeg-devel@ffmpeg.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: FFmpeg development discussions and patches List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Reply-To: FFmpeg development discussions and patches Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Errors-To: ffmpeg-devel-bounces@ffmpeg.org Sender: "ffmpeg-devel" Archived-At: List-Archive: List-Post: Quoting James Almer (2023-07-04 16:37:03) > On 7/4/2023 2:54 AM, Anton Khirnov wrote: > > Quoting Michael Niedermayer (2023-07-04 01:50:57) > >> On Mon, Jul 03, 2023 at 11:09:54PM +0200, Anton Khirnov wrote: > >>> Quoting Marton Balint (2023-07-03 22:54:41) > >>>> On Mon, 3 Jul 2023, Anton Khirnov wrote: > >>>> My patch use av_get_random_seed() which uses what the underlying OS > >>>> provides, BCrypt for Windows, /dev/urandom for Linux, arc4random() for > >>>> BSD/Mac. > >>> > >>> IOW it's a jungle of various paths, some of which are not guaranteed to > >>> be cryptographically secure. I see no such guarantees for arc4random() > >>> from a brief web search, and the fallback get_generic_seed() certainly > >>> is not either. Granted it's only used on obscure architectures, but > >>> still. > >>> > >>> The doxy even says > >>>> This function tries to provide a good seed at a best effort bases. > >>> > >>>> You really think that these are significantly worse than > >>>> OpenSSL/GCrypt, so it should not be allowed to fallback to? > >>> > >>> I think we should be using cryptographically secure PRNG for generating > >>> encryption keys, or fail when they are not available. If you want to get > >>> rid of the openssl dependency, IMO the best solution is a new > >>> int av_random(uint8_t* buf, size_t len); > >>> that guarantees either cryptographically secure randomness or an error. > >> > >> "guarantees cryptographically secure randomness" ? > >> If one defined "cryptographically secure" as "not broken publically as of today" > >> > >> Iam saying that as i think "guarantees" can be misleading in what it means > > > > I feel your snark is very much misplaced. > > > > I recall way more instances of broken crypto caused by overconfident > > non-experts with an attitude like yours ("those silly crypto libraries, > > broken all the time, how hard can it be really") than by actual > > vulnerabilities in actual crypto libraries. > > > > In fact the highest-profile break I remember (Debian key entropy bug) > > was caused precisely by non-experts fiddling with code they did not > > understand. > > Maybe the gcrypt and openssl API calls used here can instead be moved to > av_get_random_seed(), which would reduce (or outright remove) the cases > /dev/random or get_generic_seed() are called and result in essentially I see nothing wrong with using /dev/random, it's probably the most trustworthy source on most machines. Though on linux it's probably even better to use getrandom() where available. -- Anton Khirnov _______________________________________________ ffmpeg-devel mailing list ffmpeg-devel@ffmpeg.org https://ffmpeg.org/mailman/listinfo/ffmpeg-devel To unsubscribe, visit link above, or email ffmpeg-devel-request@ffmpeg.org with subject "unsubscribe".