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[209.132.180.67]) by mx.google.com with ESMTP id h8si1120766plr.291.2019.06.20.18.24.24; Thu, 20 Jun 2019 18:24:40 -0700 (PDT) Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67; Authentication-Results: mx.google.com; dkim=pass header.i=@google.com header.s=20161025 header.b="B/tZc+vn"; spf=pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org; dmarc=pass (p=REJECT sp=REJECT dis=NONE) header.from=google.com Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727072AbfFUBWT (ORCPT + 99 others); Thu, 20 Jun 2019 21:22:19 -0400 Received: from mail-pf1-f202.google.com ([209.85.210.202]:40485 "EHLO mail-pf1-f202.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726373AbfFUBT5 (ORCPT ); Thu, 20 Jun 2019 21:19:57 -0400 Received: by mail-pf1-f202.google.com with SMTP id z1so3256606pfb.7 for ; Thu, 20 Jun 2019 18:19:57 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20161025; h=date:in-reply-to:message-id:mime-version:references:subject:from:to :cc; bh=oTJZhc67YgKisP9p9JrVMJPjUu1Ev+S7xJTrYSbTZx4=; b=B/tZc+vn3WaktKNK9T4k1XUjU+a/eU0uQ08kmrDc1+bigYos9FB2WWsluAGeB/G36t YfAi0QjD4sjtPxtMnKY6HzjB3jTO7vK2JNYab6BtyV5526LbxUvgwZPU16Y9DmMfjK4z PQ9+5uZQxgsE+fsDixETFuS8E05F8v1i/abMsI5HQdBgKOMJtdKMQgAx5Pe5e2c/C8ml gdAMxEOcKnAU+r0v6LKNDPeTkZYEtmhHO99KvvbB57QlAyqICjo623Oiw4CezwS5sEuD cjmdF2SlV+e5wr/yTJ4vkNPAiCUGAy0Vu6pDAhDhbwTMEFwf3GRrdiUDbbutIw6NbH2o d0vQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:in-reply-to:message-id:mime-version :references:subject:from:to:cc; bh=oTJZhc67YgKisP9p9JrVMJPjUu1Ev+S7xJTrYSbTZx4=; b=N/8mBYTyBF885AZFer3ZskTcuHx3RfZCeYvOGFOLSERDrAkJ+Vb0dEsU3iTRD1/3wP /cpbB0x7ORKPd1jMkpjHQFBo9r4wlwNXgIL6FGAVYYlrfe7nVlMLvUjssPNYspe7aOs5 3+5JxJvgL9IRdGRV9FUBnOubp/An7flEwczHh/Od+cjLbG5eioX/CmUjceEaSVzBXe76 yoyNePQMG558sAEL1PuBy0HJrzm9uDebnJ5YVoRS5RlgfrNrMkRlhakQoC7f104UecMh uIoAMRmnCmm/rVNGJC1KwMJ6QTFrPOkqt/obbuXjq1SFb9eLmf3ehWvRfw9s+zQAACxd cVBA== X-Gm-Message-State: APjAAAUv+bsrWA+lVISAbmZ7u/ttJDXgm9/+D1OvNvEMLU43GG4y38IG f0G/SP5uCZYkiNWTWpZcXX+obAQh5zwZ2ZCkwlgMSw== X-Received: by 2002:a63:490a:: with SMTP id w10mr15275691pga.6.1561079996688; Thu, 20 Jun 2019 18:19:56 -0700 (PDT) Date: Thu, 20 Jun 2019 18:19:15 -0700 In-Reply-To: <20190621011941.186255-1-matthewgarrett@google.com> Message-Id: <20190621011941.186255-5-matthewgarrett@google.com> Mime-Version: 1.0 References: <20190621011941.186255-1-matthewgarrett@google.com> X-Mailer: git-send-email 2.22.0.410.gd8fdbe21b5-goog Subject: [PATCH V33 04/30] Enforce module signatures if the kernel is locked down From: Matthew Garrett To: jmorris@namei.org Cc: linux-security@vger.kernel.org, linux-kernel@vger.kernel.org, linux-api@vger.kernel.org, David Howells , Matthew Garrett , Jessica Yu Content-Type: text/plain; charset="UTF-8" Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: David Howells If the kernel is locked down, require that all modules have valid signatures that we can verify. I have adjusted the errors generated: (1) If there's no signature (ENODATA) or we can't check it (ENOPKG, ENOKEY), then: (a) If signatures are enforced then EKEYREJECTED is returned. (b) If there's no signature or we can't check it, but the kernel is locked down then EPERM is returned (this is then consistent with other lockdown cases). (2) If the signature is unparseable (EBADMSG, EINVAL), the signature fails the check (EKEYREJECTED) or a system error occurs (eg. ENOMEM), we return the error we got. Note that the X.509 code doesn't check for key expiry as the RTC might not be valid or might not have been transferred to the kernel's clock yet. [Modified by Matthew Garrett to remove the IMA integration. This will be replaced with integration with the IMA architecture policy patchset.] Signed-off-by: David Howells Signed-off-by: Matthew Garrett Cc: Jessica Yu --- include/linux/security.h | 1 + kernel/module.c | 39 +++++++++++++++++++++++++++++------- security/lockdown/lockdown.c | 1 + 3 files changed, 34 insertions(+), 7 deletions(-) diff --git a/include/linux/security.h b/include/linux/security.h index a86a7739ca24..a7612b03b42a 100644 --- a/include/linux/security.h +++ b/include/linux/security.h @@ -82,6 +82,7 @@ enum lsm_event { */ enum lockdown_reason { LOCKDOWN_NONE, + LOCKDOWN_MODULE_SIGNATURE, LOCKDOWN_INTEGRITY_MAX, LOCKDOWN_CONFIDENTIALITY_MAX, }; diff --git a/kernel/module.c b/kernel/module.c index 0b9aa8ab89f0..780e9605ff88 100644 --- a/kernel/module.c +++ b/kernel/module.c @@ -2763,8 +2763,9 @@ static inline void kmemleak_load_module(const struct module *mod, #ifdef CONFIG_MODULE_SIG static int module_sig_check(struct load_info *info, int flags) { - int err = -ENOKEY; + int err = -ENODATA; const unsigned long markerlen = sizeof(MODULE_SIG_STRING) - 1; + const char *reason; const void *mod = info->hdr; /* @@ -2779,16 +2780,40 @@ static int module_sig_check(struct load_info *info, int flags) err = mod_verify_sig(mod, info); } - if (!err) { + switch (err) { + case 0: info->sig_ok = true; return 0; - } - /* Not having a signature is only an error if we're strict. */ - if (err == -ENOKEY && !is_module_sig_enforced()) - err = 0; + /* We don't permit modules to be loaded into trusted kernels + * without a valid signature on them, but if we're not + * enforcing, certain errors are non-fatal. + */ + case -ENODATA: + reason = "Loading of unsigned module"; + goto decide; + case -ENOPKG: + reason = "Loading of module with unsupported crypto"; + goto decide; + case -ENOKEY: + reason = "Loading of module with unavailable key"; + decide: + if (is_module_sig_enforced()) { + pr_notice("%s is rejected\n", reason); + return -EKEYREJECTED; + } - return err; + if (security_is_locked_down(LOCKDOWN_MODULE_SIGNATURE)) + return -EPERM; + return 0; + + /* All other errors are fatal, including nomem, unparseable + * signatures and signature check failures - even if signatures + * aren't required. + */ + default: + return err; + } } #else /* !CONFIG_MODULE_SIG */ static int module_sig_check(struct load_info *info, int flags) diff --git a/security/lockdown/lockdown.c b/security/lockdown/lockdown.c index 1ecb2eecb245..08abd7e6609b 100644 --- a/security/lockdown/lockdown.c +++ b/security/lockdown/lockdown.c @@ -18,6 +18,7 @@ static enum lockdown_reason kernel_locked_down; static char *lockdown_reasons[LOCKDOWN_CONFIDENTIALITY_MAX+1] = { [LOCKDOWN_NONE] = "none", + [LOCKDOWN_MODULE_SIGNATURE] = "unsigned module loading", [LOCKDOWN_INTEGRITY_MAX] = "integrity", [LOCKDOWN_CONFIDENTIALITY_MAX] = "confidentiality", }; -- 2.22.0.410.gd8fdbe21b5-goog