From patchwork Thu Jun 6 02:11:45 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Sean Christopherson X-Patchwork-Id: 10978323 Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id C4F6C1398 for ; Thu, 6 Jun 2019 02:12:14 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id B7BAB200E5 for ; Thu, 6 Jun 2019 02:12:14 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id A87532870E; Thu, 6 Jun 2019 02:12:14 +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=-6.9 required=2.0 tests=BAYES_00,RCVD_IN_DNSWL_HI autolearn=unavailable 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 3A55F2870E for ; Thu, 6 Jun 2019 02:12:14 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726835AbfFFCMF (ORCPT ); Wed, 5 Jun 2019 22:12:05 -0400 Received: from mga02.intel.com ([134.134.136.20]:19592 "EHLO mga02.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726541AbfFFCLv (ORCPT ); Wed, 5 Jun 2019 22:11:51 -0400 X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from orsmga004.jf.intel.com ([10.7.209.38]) by orsmga101.jf.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 05 Jun 2019 19:11:50 -0700 X-ExtLoop1: 1 Received: from sjchrist-coffee.jf.intel.com ([10.54.74.36]) by orsmga004.jf.intel.com with ESMTP; 05 Jun 2019 19:11:49 -0700 From: Sean Christopherson To: Jarkko Sakkinen Cc: Andy Lutomirski , Cedric Xing , Stephen Smalley , James Morris , "Serge E . Hallyn" , LSM List , Paul Moore , Eric Paris , selinux@vger.kernel.org, Jethro Beekman , Dave Hansen , Thomas Gleixner , Linus Torvalds , LKML , X86 ML , linux-sgx@vger.kernel.org, Andrew Morton , nhorman@redhat.com, npmccallum@redhat.com, Serge Ayoun , Shay Katz-zamir , Haitao Huang , Andy Shevchenko , Kai Svahn , Borislav Petkov , Josh Triplett , Kai Huang , David Rientjes , William Roberts , Philip Tricca Subject: [RFC PATCH v2 5/5] security/selinux: Add enclave_load() implementation Date: Wed, 5 Jun 2019 19:11:45 -0700 Message-Id: <20190606021145.12604-6-sean.j.christopherson@intel.com> X-Mailer: git-send-email 2.21.0 In-Reply-To: <20190606021145.12604-1-sean.j.christopherson@intel.com> References: <20190606021145.12604-1-sean.j.christopherson@intel.com> MIME-Version: 1.0 Sender: owner-linux-security-module@vger.kernel.org Precedence: bulk List-ID: X-Virus-Scanned: ClamAV using ClamSMTP The goal of selinux_enclave_load() is to provide a facsimile of the existing selinux_file_mprotect() and file_map_prot_check() policies, but tailored to the unique properties of SGX. For example, an enclave page is technically backed by a MAP_SHARED file, but the "file" is essentially shared memory that is never persisted anywhere and also requires execute permissions (for some pages). The basic concept is to require appropriate execute permissions on the source of the enclave for pages that are requesting PROT_EXEC, e.g. if an enclave page is being loaded from a regular file, require FILE__EXECUTE and/or FILE__EXECMOND, and if it's coming from an anonymous/private mapping, require PROCESS__EXECMEM since the process is essentially executing from the mapping, albeit in a roundabout way. Note, FILE__READ and FILE__WRITE are intentionally not required even if the source page is backed by a regular file. Writes to the enclave page are contained to the EPC, i.e. never hit the original file, and read permissions have already been vetted (or the VMA doesn't have PROT_READ, in which case loading the page into the enclave will fail). Signed-off-by: Sean Christopherson --- security/selinux/hooks.c | 69 ++++++++++++++++++++++++++++++++++++++++ 1 file changed, 69 insertions(+) diff --git a/security/selinux/hooks.c b/security/selinux/hooks.c index 3ec702cf46ca..3c5418edf51c 100644 --- a/security/selinux/hooks.c +++ b/security/selinux/hooks.c @@ -6726,6 +6726,71 @@ static void selinux_bpf_prog_free(struct bpf_prog_aux *aux) } #endif +#ifdef CONFIG_INTEL_SGX +int selinux_enclave_load(struct vm_area_struct *vma, unsigned long prot) +{ + const struct cred *cred = current_cred(); + u32 sid = cred_sid(cred); + int ret; + + /* SGX is supported only in 64-bit kernels. */ + WARN_ON_ONCE(!default_noexec); + + /* Only executable enclave pages are restricted in any way. */ + if (!(prot & PROT_EXEC)) + return 0; + + /* + * The source page is exectuable, i.e. has already passed SELinux's + * checks, and userspace is not requesting RW->RX capabilities. + */ + if ((vma->vm_flags & VM_EXEC) && !(prot & PROT_WRITE)) + return 0; + + /* + * The source page is not executable, or userspace is requesting the + * ability to do a RW->RX conversion. Permissions are required as + * follows, in order of increasing privelege: + * + * EXECUTE - Load an executable enclave page without RW->RX intent from + * a non-executable vma that is backed by a shared mapping to + * a regular file that has not undergone COW. + * + * EXECMOD - Load an executable enclave page without RW->RX intent from + * a non-executable vma that is backed by a shared mapping to + * a regular file that *has* undergone COW. + * + * - Load an enclave page *with* RW->RX intent from a shared + * mapping to a regular file. + * + * EXECMEM - Load an exectuable enclave page from an anonymous mapping. + * + * - Load an exectuable enclave page from a private file, e.g. + * from a shared mapping to a hugetlbfs file. + * + * - Load an enclave page *with* RW->RX intent from a private + * mapping to a regular file. + * + * Note, this hybrid EXECMOD and EXECMEM behavior is intentional and + * reflects the nature of enclaves and the EPC, e.g. EPC is effectively + * a non-persistent shared file, but each enclave is a private domain + * within that shared file, so delegate to the source of the enclave. + */ + if (vma->vm_file && !IS_PRIVATE(file_inode(vma->vm_file) && + ((vma->vm_flags & VM_SHARED) || !(prot & PROT_WRITE)))) { + if (!vma->anon_vma && !(prot & PROT_WRITE)) + ret = file_has_perm(cred, vma->vm_file, FILE__EXECUTE); + else + ret = file_has_perm(cred, vma->vm_file, FILE__EXECMOD); + } else { + ret = avc_has_perm(&selinux_state, + sid, sid, SECCLASS_PROCESS, + PROCESS__EXECMEM, NULL); + } + return ret; +} +#endif + struct lsm_blob_sizes selinux_blob_sizes __lsm_ro_after_init = { .lbs_cred = sizeof(struct task_security_struct), .lbs_file = sizeof(struct file_security_struct), @@ -6968,6 +7033,10 @@ static struct security_hook_list selinux_hooks[] __lsm_ro_after_init = { LSM_HOOK_INIT(bpf_map_free_security, selinux_bpf_map_free), LSM_HOOK_INIT(bpf_prog_free_security, selinux_bpf_prog_free), #endif + +#ifdef CONFIG_INTEL_SGX + LSM_HOOK_INIT(enclave_load, selinux_enclave_load), +#endif }; static __init int selinux_init(void)