From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-13.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id CAAF2C433E6 for ; Fri, 22 Jan 2021 20:28:51 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 75F0323B00 for ; Fri, 22 Jan 2021 20:28:51 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729227AbhAVU2g (ORCPT ); Fri, 22 Jan 2021 15:28:36 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:44434 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729948AbhAVU0k (ORCPT ); Fri, 22 Jan 2021 15:26:40 -0500 Received: from mail-ej1-x62f.google.com (mail-ej1-x62f.google.com [IPv6:2a00:1450:4864:20::62f]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 227D3C0611C2 for ; Fri, 22 Jan 2021 12:24:15 -0800 (PST) Received: by mail-ej1-x62f.google.com with SMTP id w1so9422017ejf.11 for ; Fri, 22 Jan 2021 12:24:15 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=paul-moore-com.20150623.gappssmtp.com; s=20150623; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=gu7BPVK/5cN33sOPWqBrquGS1TwEUcHxhHvkOIjwjGU=; b=adU78LhZ1G9dqi35N6mj+d+5czdFx/5S6AdvJ6itnyJE7NXSnO0Okd8YIzkEAYe6B3 Ie29TEbdPZgCxaHvrQRTYTbmaArmterVTpTL1ri4q5qahWQ2b1SyApPH87SzF1kupz2X YW4YcuFx7m0UxBzCBcuE6swwvIapERgnMWUBzP8VcluUYGg24dlRJ2krMCCtA7wz2h3O Wrqweu2UQsq/HyoHzqAQ+kVVwt3jFzmWc9iCpZ5fWHfyhmqgssv29z9fIVsvXmF9AlNS rHTQkeh8pSLiExtaGRnOGAOQ3WMkG4OMkcYk32+2O15jAR9Lzop8o/V7xKEiLoBekCVu ktZg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=gu7BPVK/5cN33sOPWqBrquGS1TwEUcHxhHvkOIjwjGU=; b=F7O0V3ZpBFZMWbw1IPg51A+ZM/e291tjYYLqHVA90K3pXeXgqxpGH1vrgnSI3ZZ8T5 5vwZ0gF+hEKG0MQinA8PrbsTVbyYtqo7JE2w2PXg2bAOuNAokT01Lz99kdou57Z4U/LQ n9YrN0RrONCj1ntRdMtCKrBsyU6aGZUPS4nog6pBe4kh6RLrqLtcwD89xPryVOluEnsN odI9RGcLN2aQEFCH9wgXVIkjVnGT1vzGWJ7Kp5VnSdgXJDwuB+QRiUuI+zWDhQBpeF1s ufYE5SZ5JcaqHebKu5pjw95NR066pwEpVWxKuPHLoAOEuOUj7cI6b3UMh/SADZZQikdv JS/g== X-Gm-Message-State: AOAM530GamQa4ln5MwrWFVAHXUVsqWVxPP+QOa2pEVlEurQYeenFWMPf dTVgfrEK67fSlI31YOwSxhx2SKhn8UFPR4tOcqWf X-Google-Smtp-Source: ABdhPJzrnVrcK0ubImcc7+9kEe8T1NGrjhLvqn1GIVJxYuJWJ62Nco/7FgfyJzVo4nbX8Lcbg2yXGRLCJgbdPnzDB0o= X-Received: by 2002:a17:906:95cf:: with SMTP id n15mr80514ejy.178.1611347053529; Fri, 22 Jan 2021 12:24:13 -0800 (PST) MIME-Version: 1.0 References: <20210114191522.4001-1-nramas@linux.microsoft.com> In-Reply-To: <20210114191522.4001-1-nramas@linux.microsoft.com> From: Paul Moore Date: Fri, 22 Jan 2021 15:24:02 -0500 Message-ID: Subject: Re: [PATCH] selinux: include a consumer of the new IMA critical data hook To: zohar@linux.ibm.com Cc: Stephen Smalley , tusharsu@linux.microsoft.com, tyhicks@linux.microsoft.com, casey@schaufler-ca.com, agk@redhat.com, snitzer@redhat.com, gmazyland@gmail.com, sashal@kernel.org, James Morris , linux-integrity@vger.kernel.org, selinux@vger.kernel.org, linux-security-module@vger.kernel.org, linux-kernel@vger.kernel.org, Lakshmi Ramasubramanian Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: On Thu, Jan 14, 2021 at 2:15 PM Lakshmi Ramasubramanian wrote: > > SELinux stores the active policy in memory, so the changes to this data > at runtime would have an impact on the security guarantees provided > by SELinux. Measuring in-memory SELinux policy through IMA subsystem > provides a secure way for the attestation service to remotely validate > the policy contents at runtime. > > Measure the hash of the loaded policy by calling the IMA hook > ima_measure_critical_data(). Since the size of the loaded policy > can be large (several MB), measure the hash of the policy instead of > the entire policy to avoid bloating the IMA log entry. > > To enable SELinux data measurement, the following steps are required: > > 1, Add "ima_policy=critical_data" to the kernel command line arguments > to enable measuring SELinux data at boot time. > For example, > BOOT_IMAGE=/boot/vmlinuz-5.10.0-rc1+ root=UUID=fd643309-a5d2-4ed3-b10d-3c579a5fab2f ro nomodeset security=selinux ima_policy=critical_data > > 2, Add the following rule to /etc/ima/ima-policy > measure func=CRITICAL_DATA label=selinux > > Sample measurement of the hash of SELinux policy: > > To verify the measured data with the current SELinux policy run > the following commands and verify the output hash values match. > > sha256sum /sys/fs/selinux/policy | cut -d' ' -f 1 > > grep "selinux-policy-hash" /sys/kernel/security/integrity/ima/ascii_runtime_measurements | tail -1 | cut -d' ' -f 6 > > Note that the actual verification of SELinux policy would require loading > the expected policy into an identical kernel on a pristine/known-safe > system and run the sha256sum /sys/kernel/selinux/policy there to get > the expected hash. > > Signed-off-by: Lakshmi Ramasubramanian > Suggested-by: Stephen Smalley > Acked-by: Paul Moore > Reviewed-by: Tyler Hicks > --- > Documentation/ABI/testing/ima_policy | 3 +- > security/selinux/Makefile | 2 + > security/selinux/ima.c | 44 +++++++++++++++++++ > security/selinux/include/ima.h | 24 +++++++++++ > security/selinux/include/security.h | 3 +- > security/selinux/ss/services.c | 64 ++++++++++++++++++++++++---- > 6 files changed, 129 insertions(+), 11 deletions(-) > create mode 100644 security/selinux/ima.c > create mode 100644 security/selinux/include/ima.h Hi Mimi, Just checking as I didn't see a reply to this from you in my inbox, you merged this into the IMA linux-next branch, yes? > diff --git a/Documentation/ABI/testing/ima_policy b/Documentation/ABI/testing/ima_policy > index 54fe1c15ed50..8365596cb42b 100644 > --- a/Documentation/ABI/testing/ima_policy > +++ b/Documentation/ABI/testing/ima_policy > @@ -52,8 +52,9 @@ Description: > template:= name of a defined IMA template type > (eg, ima-ng). Only valid when action is "measure". > pcr:= decimal value > - label:= [data_label] > + label:= [selinux]|[data_label] > data_label:= a unique string used for grouping and limiting critical data. > + For example, "selinux" to measure critical data for SELinux. > > default policy: > # PROC_SUPER_MAGIC > diff --git a/security/selinux/Makefile b/security/selinux/Makefile > index 4d8e0e8adf0b..776162444882 100644 > --- a/security/selinux/Makefile > +++ b/security/selinux/Makefile > @@ -16,6 +16,8 @@ selinux-$(CONFIG_NETLABEL) += netlabel.o > > selinux-$(CONFIG_SECURITY_INFINIBAND) += ibpkey.o > > +selinux-$(CONFIG_IMA) += ima.o > + > ccflags-y := -I$(srctree)/security/selinux -I$(srctree)/security/selinux/include > > $(addprefix $(obj)/,$(selinux-y)): $(obj)/flask.h > diff --git a/security/selinux/ima.c b/security/selinux/ima.c > new file mode 100644 > index 000000000000..03715893ff97 > --- /dev/null > +++ b/security/selinux/ima.c > @@ -0,0 +1,44 @@ > +// SPDX-License-Identifier: GPL-2.0+ > +/* > + * Copyright (C) 2021 Microsoft Corporation > + * > + * Author: Lakshmi Ramasubramanian (nramas@linux.microsoft.com) > + * > + * Measure critical data structures maintainted by SELinux > + * using IMA subsystem. > + */ > +#include > +#include > +#include "security.h" > +#include "ima.h" > + > +/* > + * selinux_ima_measure_state - Measure hash of the SELinux policy > + * > + * @state: selinux state struct > + * > + * NOTE: This function must be called with policy_mutex held. > + */ > +void selinux_ima_measure_state(struct selinux_state *state) > +{ > + void *policy = NULL; > + size_t policy_len; > + int rc = 0; > + > + /* > + * Measure SELinux policy only after initialization is completed. > + */ > + if (!selinux_initialized(state)) > + return; > + > + rc = security_read_state_kernel(state, &policy, &policy_len); > + if (rc) { > + pr_err("SELinux: %s: failed to read policy %d.\n", __func__, rc); > + return; > + } > + > + ima_measure_critical_data("selinux", "selinux-policy-hash", > + policy, policy_len, true); > + > + vfree(policy); > +} > diff --git a/security/selinux/include/ima.h b/security/selinux/include/ima.h > new file mode 100644 > index 000000000000..d69c36611423 > --- /dev/null > +++ b/security/selinux/include/ima.h > @@ -0,0 +1,24 @@ > +/* SPDX-License-Identifier: GPL-2.0+ */ > +/* > + * Copyright (C) 2021 Microsoft Corporation > + * > + * Author: Lakshmi Ramasubramanian (nramas@linux.microsoft.com) > + * > + * Measure critical data structures maintainted by SELinux > + * using IMA subsystem. > + */ > + > +#ifndef _SELINUX_IMA_H_ > +#define _SELINUX_IMA_H_ > + > +#include "security.h" > + > +#ifdef CONFIG_IMA > +extern void selinux_ima_measure_state(struct selinux_state *selinux_state); > +#else > +static inline void selinux_ima_measure_state(struct selinux_state *selinux_state) > +{ > +} > +#endif > + > +#endif /* _SELINUX_IMA_H_ */ > diff --git a/security/selinux/include/security.h b/security/selinux/include/security.h > index 3cc8bab31ea8..29cae32d3fc5 100644 > --- a/security/selinux/include/security.h > +++ b/security/selinux/include/security.h > @@ -229,7 +229,8 @@ void selinux_policy_cancel(struct selinux_state *state, > struct selinux_policy *policy); > int security_read_policy(struct selinux_state *state, > void **data, size_t *len); > - > +int security_read_state_kernel(struct selinux_state *state, > + void **data, size_t *len); > int security_policycap_supported(struct selinux_state *state, > unsigned int req_cap); > > diff --git a/security/selinux/ss/services.c b/security/selinux/ss/services.c > index 9704c8a32303..cc8dbc4ed8db 100644 > --- a/security/selinux/ss/services.c > +++ b/security/selinux/ss/services.c > @@ -65,6 +65,7 @@ > #include "ebitmap.h" > #include "audit.h" > #include "policycap_names.h" > +#include "ima.h" > > /* Forward declaration. */ > static int context_struct_to_string(struct policydb *policydb, > @@ -2180,6 +2181,7 @@ static void selinux_notify_policy_change(struct selinux_state *state, > selinux_status_update_policyload(state, seqno); > selinux_netlbl_cache_invalidate(); > selinux_xfrm_notify_policyload(); > + selinux_ima_measure_state(state); > } > > void selinux_policy_commit(struct selinux_state *state, > @@ -3875,8 +3877,33 @@ int security_netlbl_sid_to_secattr(struct selinux_state *state, > } > #endif /* CONFIG_NETLABEL */ > > +/** > + * __security_read_policy - read the policy. > + * @policy: SELinux policy > + * @data: binary policy data > + * @len: length of data in bytes > + * > + */ > +static int __security_read_policy(struct selinux_policy *policy, > + void *data, size_t *len) > +{ > + int rc; > + struct policy_file fp; > + > + fp.data = data; > + fp.len = *len; > + > + rc = policydb_write(&policy->policydb, &fp); > + if (rc) > + return rc; > + > + *len = (unsigned long)fp.data - (unsigned long)data; > + return 0; > +} > + > /** > * security_read_policy - read the policy. > + * @state: selinux_state > * @data: binary policy data > * @len: length of data in bytes > * > @@ -3885,8 +3912,6 @@ int security_read_policy(struct selinux_state *state, > void **data, size_t *len) > { > struct selinux_policy *policy; > - int rc; > - struct policy_file fp; > > policy = rcu_dereference_protected( > state->policy, lockdep_is_held(&state->policy_mutex)); > @@ -3898,14 +3923,35 @@ int security_read_policy(struct selinux_state *state, > if (!*data) > return -ENOMEM; > > - fp.data = *data; > - fp.len = *len; > + return __security_read_policy(policy, *data, len); > +} > > - rc = policydb_write(&policy->policydb, &fp); > - if (rc) > - return rc; > +/** > + * security_read_state_kernel - read the policy. > + * @state: selinux_state > + * @data: binary policy data > + * @len: length of data in bytes > + * > + * Allocates kernel memory for reading SELinux policy. > + * This function is for internal use only and should not > + * be used for returning data to user space. > + * > + * This function must be called with policy_mutex held. > + */ > +int security_read_state_kernel(struct selinux_state *state, > + void **data, size_t *len) > +{ > + struct selinux_policy *policy; > > - *len = (unsigned long)fp.data - (unsigned long)*data; > - return 0; > + policy = rcu_dereference_protected( > + state->policy, lockdep_is_held(&state->policy_mutex)); > + if (!policy) > + return -EINVAL; > + > + *len = policy->policydb.len; > + *data = vmalloc(*len); > + if (!*data) > + return -ENOMEM; > > + return __security_read_policy(policy, *data, len); > } > -- > 2.30.0 -- paul moore www.paul-moore.com