From patchwork Mon Jun 5 03:47:52 2017 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: "Jason A. Donenfeld" X-Patchwork-Id: 9765385 X-Patchwork-Delegate: herbert@gondor.apana.org.au Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork.web.codeaurora.org (Postfix) with ESMTP id 3850660353 for ; Mon, 5 Jun 2017 03:48:50 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 2833526E69 for ; Mon, 5 Jun 2017 03:48:50 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id 1CBB927FA3; Mon, 5 Jun 2017 03:48:50 +0000 (UTC) X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on pdx-wl-mail.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-7.0 required=2.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID, DKIM_VALID_AU, RCVD_IN_DNSWL_HI autolearn=ham version=3.3.1 Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id B6D0726E69 for ; Mon, 5 Jun 2017 03:48:49 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751305AbdFEDsh (ORCPT ); Sun, 4 Jun 2017 23:48:37 -0400 Received: from frisell.zx2c4.com ([192.95.5.64]:36893 "EHLO frisell.zx2c4.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751293AbdFEDse (ORCPT ); Sun, 4 Jun 2017 23:48:34 -0400 Received: by frisell.zx2c4.com (ZX2C4 Mail Server) with ESMTP id b966bdad; Mon, 5 Jun 2017 03:48:24 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha1; c=relaxed; d=zx2c4.com; h=from:to:cc :subject:date:message-id:in-reply-to:references; s=mail; bh=GRxA CeWe262M0gxylkDfHHdzKxs=; b=EyzMdIFD6941N78uGt9Wta7s+FX015j1mGBx e0GLynjLtSxwGo6Bpn9t+6NA1E+KbkRMGeITEnKcFLRIglfKbpSa2fZHJaq2qCBs aBOmi/RqEt3bjQ192oW570bHiUL/9zlYZtGmBid3QQAy+N0M+YHJ8AuB8/j6cbIl +RuOx0rT4laWkSceuKMcnssDRZTdvBjbXIOiuPXZ02XW91y8UCaWOZulJGeQcwzS Ea1hP/Dc2XdbmySeDuYXuZGs6rVYdBGyO7dMkmmPcSDWXZNu36XyKjWWOwQ8RnP4 UcnFQU2Pdk8rethhHPM3x6QcqWYuwKpNUAqHW4Zinc0i+aYl9A== Received: by frisell.zx2c4.com (ZX2C4 Mail Server) with ESMTPSA id bbcedbbd (TLSv1.2:ECDHE-RSA-AES256-GCM-SHA384:256:NO); Mon, 5 Jun 2017 03:48:24 +0000 (UTC) From: "Jason A. Donenfeld" To: Theodore Ts'o , Linux Crypto Mailing List , LKML , kernel-hardening@lists.openwall.com, Greg Kroah-Hartman Cc: "Jason A. Donenfeld" Subject: [PATCH RFC v2 3/8] random: warn when kernel uses unseeded randomness Date: Mon, 5 Jun 2017 05:47:52 +0200 Message-Id: <20170605034757.4803-4-Jason@zx2c4.com> X-Mailer: git-send-email 2.13.0 In-Reply-To: <20170605034757.4803-1-Jason@zx2c4.com> References: <20170605034757.4803-1-Jason@zx2c4.com> Sender: linux-crypto-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-crypto@vger.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP This enables an important dmesg notification about when drivers have used the crng without it being seeded first. Prior, these errors would occur silently, and so there hasn't been a great way of diagnosing these types of bugs for obscure setups. By adding this as a config option, we can leave it on by default, so that we learn where these issues happen, in the field, will still allowing some people to turn it off, if they really know what they're doing and do not want the log entries. Signed-off-by: Jason A. Donenfeld --- drivers/char/random.c | 3 +-- lib/Kconfig.debug | 15 +++++++++++++++ 2 files changed, 16 insertions(+), 2 deletions(-) diff --git a/drivers/char/random.c b/drivers/char/random.c index 035a5d7c06bd..9320b04235ae 100644 --- a/drivers/char/random.c +++ b/drivers/char/random.c @@ -285,7 +285,6 @@ #define SEC_XFER_SIZE 512 #define EXTRACT_SIZE 10 -#define DEBUG_RANDOM_BOOT 0 #define LONGS(x) (((x) + sizeof(unsigned long) - 1)/sizeof(unsigned long)) @@ -1470,7 +1469,7 @@ void get_random_bytes(void *buf, int nbytes) { __u8 tmp[CHACHA20_BLOCK_SIZE]; -#if DEBUG_RANDOM_BOOT > 0 +#ifdef CONFIG_WARN_UNSEEDED_RANDOM if (!crng_ready()) printk(KERN_NOTICE "random: %pF get_random_bytes called " "with crng_init = %d\n", (void *) _RET_IP_, crng_init); diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug index e4587ebe52c7..fd5e67bcd46c 100644 --- a/lib/Kconfig.debug +++ b/lib/Kconfig.debug @@ -1209,6 +1209,21 @@ config STACKTRACE It is also used by various kernel debugging features that require stack trace generation. +config WARN_UNSEEDED_RANDOM + bool "Warn when kernel uses unseeded randomness" + default y + help + Some parts of the kernel contain bugs relating to their use of + cryptographically secure random numbers before it's actually possible + to generate those numbers securely. This setting ensures that these + flaws don't go unnoticed, by enabling a message, should this ever + occur. This will allow people with obscure setups to know when things + are going wrong, so that they might contact developers about fixing + it. + + Say Y here, unless you simply do not care about using unseeded + randomness and do not want a potential warning message in your logs. + config DEBUG_KOBJECT bool "kobject debugging" depends on DEBUG_KERNEL