From patchwork Mon Sep 11 19:50:27 2017 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Salvatore Mesoraca X-Patchwork-Id: 9948021 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 A8546602C9 for ; Mon, 11 Sep 2017 19:53:26 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id A161A28D31 for ; Mon, 11 Sep 2017 19:53:26 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id 95E6128D34; Mon, 11 Sep 2017 19:53:26 +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=-2.1 required=2.0 tests=BAYES_00, DKIM_ADSP_CUSTOM_MED, DKIM_SIGNED, FREEMAIL_FROM, GAPPY_SUBJECT, RCVD_IN_DNSWL_MED, T_DKIM_INVALID autolearn=ham version=3.3.1 Received: from mother.openwall.net (mother.openwall.net [195.42.179.200]) by mail.wl.linuxfoundation.org (Postfix) with SMTP id 3D80928D31 for ; Mon, 11 Sep 2017 19:53:25 +0000 (UTC) Received: (qmail 3401 invoked by uid 550); 11 Sep 2017 19:52:07 -0000 Mailing-List: contact kernel-hardening-help@lists.openwall.com; run by ezmlm Precedence: bulk List-Post: List-Help: List-Unsubscribe: List-Subscribe: List-ID: Delivered-To: mailing list kernel-hardening@lists.openwall.com Received: (qmail 3168 invoked from network); 11 Sep 2017 19:52:02 -0000 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=from:to:cc:subject:date:message-id:in-reply-to:references; bh=skf8WPbB1GWDV/gzvs4Z/BCaReKXVJlnD0B/SSmuI7g=; b=YuVHhmmXgEaR6LoI62ZFhVFfnim/DLTT5NC0BtrJ6H5noPcfMimtltgvaNSsyZy2eb 9shimXTFIdtqqgcI9tlEpirUmNaaV9RdR6ZTA3J76XfXJlhGor9l6sz1ywclCljeSwj6 U0XzW+4T4eD+kX5Cl8Yhks30RkP9kpRVxuGdTl0kTzfriPs75RobZDbtm35i+Q8EOD3p 6g/uoTR3GEBI0Sz29ay4wZOJlcC0kDUgfUXPKL9pNnMZbvTV23Blw7JfEnKsbSeVch6I hzE5o3knzS7ek9Ajyz1qGJzertSuIRD/veNsILbiUHVkIUkvbOuxR/pfLFFymUoWulp+ /SuQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:from:to:cc:subject:date:message-id:in-reply-to :references; bh=skf8WPbB1GWDV/gzvs4Z/BCaReKXVJlnD0B/SSmuI7g=; b=ep1tLR6X71AqNWxLvR0In1gylT7KOj13EF7J2bEhZ+A838O0tPh+Q1ZchFP9H2MR1M mVWm87AwMsoW46HzIKgdkeD6Vj8sgNYSTHU6NjxjNItUaLTTp8zU2Beum1BPXCU2Du5r qJlFA6tuUDstium3r1Spxgf74OAfZEJqNc37AaPiAi3vOYJdoe1/GxTcEfbGc6uWw6lV hOXIbvmShSzmqkLDwURGDpddlpOl0hv59Kl89R+bwSIu2ZHeEaPeB9FZmsFVST4zO7RP lA/fJL8y/BHr0QJKqhkBGFAt1U2CkClftMmuY2z4fDjmwgVwSSTbSuI9XYeHQhCYE4Hn b3gw== X-Gm-Message-State: AHPjjUgf2caZVI99Kvl5IXnPaVFsdT6A0gveU72y+hYTYif3IwC9Kdws 3zrQqgQgFQ5Gw91hdxTQ7p4= X-Google-Smtp-Source: AOwi7QDMu7k5izHA7+2J/ZWnityiljW8dw1Meik+oCPacFvocukknANY0RVODP0f9kCVfoVgBiCLUg== X-Received: by 10.28.128.197 with SMTP id b188mr8962511wmd.121.1505159511438; Mon, 11 Sep 2017 12:51:51 -0700 (PDT) From: Salvatore Mesoraca To: linux-kernel@vger.kernel.org Cc: linux-security-module@vger.kernel.org, kernel-hardening@lists.openwall.com, Salvatore Mesoraca , Brad Spengler , PaX Team , Casey Schaufler , Kees Cook , James Morris , "Serge E. Hallyn" Date: Mon, 11 Sep 2017 21:50:27 +0200 Message-Id: <1505159427-11747-10-git-send-email-s.mesoraca16@gmail.com> X-Mailer: git-send-email 1.9.1 In-Reply-To: <1505159427-11747-1-git-send-email-s.mesoraca16@gmail.com> References: <1505159427-11747-1-git-send-email-s.mesoraca16@gmail.com> Subject: [kernel-hardening] [RFC v3 9/9] S.A.R.A. WX Protection procattr interface X-Virus-Scanned: ClamAV using ClamSMTP This allow threads to get current WX Protection flags for themselves or for other threads (if they have CAP_MAC_ADMIN). It also allow a thread to set itself flags to a stricter set of rules than the current one. Via a new wxprot flag (SARA_WXP_FORCE_WXORX) is it possible to ask the kernel to rescan the memory and remove the VM_WRITE flag from any area that is marked both writable and executable. Protections that prevent the runtime creation of executable code can be troublesome for all those programs that actually need to do it e.g. programs shipping with a JIT compiler built-in. This feature can be use to run the JIT compiler with few restrictions while enforcing full WX Protection in the rest of the program. To simplify access to this interface a CC0 licensed library is available here: https://github.com/smeso/libsara Signed-off-by: Salvatore Mesoraca --- security/sara/wxprot.c | 150 +++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 150 insertions(+) diff --git a/security/sara/wxprot.c b/security/sara/wxprot.c index d360833..afc4e13 100644 --- a/security/sara/wxprot.c +++ b/security/sara/wxprot.c @@ -12,6 +12,7 @@ #ifdef CONFIG_SECURITY_SARA_WXPROT #include +#include #include #include #include @@ -43,6 +44,7 @@ #define SARA_WXP_COMPLAIN 0x0010 #define SARA_WXP_VERBOSE 0x0020 #define SARA_WXP_MMAP 0x0040 +#define SARA_WXP_FORCE_WXORX 0x0080 #define SARA_WXP_EMUTRAMP 0x0100 #define SARA_WXP_TRANSFER 0x0200 #define SARA_WXP_NONE 0x0000 @@ -540,6 +542,152 @@ static inline int sara_pagefault_handler_x86_64(struct pt_regs *regs) #endif /* CONFIG_SECURITY_SARA_WXPROT_EMUTRAMP */ +static int sara_getprocattr(struct task_struct *p, char *name, char **value) +{ + int ret; + u16 flags; + char *buf; + + ret = -EINVAL; + if (strcmp(name, "wxprot") != 0) + goto out; + + ret = -EACCES; + if (unlikely(current != p && + !capable(CAP_MAC_ADMIN))) + goto out; + + ret = -ENOMEM; + buf = kzalloc(8, GFP_KERNEL); + if (unlikely(buf == NULL)) + goto out; + + if (!sara_enabled || !wxprot_enabled) { + flags = 0x0; + } else { + rcu_read_lock(); + flags = get_sara_wxp_flags(__task_cred(p)); + rcu_read_unlock(); + } + + snprintf(buf, 8, "0x%04x\n", flags); + ret = strlen(buf); + *value = buf; + +out: + return ret; +} + +static int sara_setprocattr(const char *name, void *value, size_t size) +{ + int ret; + struct vm_area_struct *vma; + struct cred *new = prepare_creds(); + u16 cur_flags; + u16 req_flags; + char *buf = NULL; + + ret = -EINVAL; + if (!sara_enabled || !wxprot_enabled) + goto error; + if (unlikely(new == NULL)) + return -ENOMEM; + if (strcmp(name, "wxprot") != 0) + goto error; + if (unlikely(value == NULL || size == 0 || size > 7)) + goto error; + ret = -ENOMEM; + buf = kmalloc(size+1, GFP_KERNEL); + if (unlikely(buf == NULL)) + goto error; + buf[size] = '\0'; + memcpy(buf, value, size); + ret = -EINVAL; + if (unlikely(strlen(buf) != size)) + goto error; + if (unlikely(kstrtou16(buf, 16, &req_flags) != 0)) + goto error; + /* + * SARA_WXP_FORCE_WXORX is a procattr only flag with a special + * meaning and it isn't recognized by are_flags_valid + */ + if (unlikely(!are_flags_valid(req_flags & ~SARA_WXP_FORCE_WXORX))) + goto error; + /* + * Extra checks on requested flags: + * - SARA_WXP_FORCE_WXORX requires SARA_WXP_WXORX + * - SARA_WXP_MMAP can only be activated if the program + * has a relro section + * - COMPLAIN mode can only be requested if it was already + * on (procattr can only be used to make protection stricter) + * - EMUTRAMP can only be activated if it was already on or + * if MPROTECT and WXORX weren't already on (procattr can + * only be used to make protection stricter) + * - VERBOSITY request is ignored + */ + if (unlikely(req_flags & SARA_WXP_FORCE_WXORX && + !(req_flags & SARA_WXP_WXORX))) + goto error; + if (unlikely(!get_current_sara_relro_page_found() && + req_flags & SARA_WXP_MMAP)) + goto error; + cur_flags = get_current_sara_wxp_flags(); + if (unlikely((req_flags & SARA_WXP_COMPLAIN) && + !(cur_flags & SARA_WXP_COMPLAIN))) + goto error; + if (unlikely((req_flags & SARA_WXP_EMUTRAMP) && + !(cur_flags & SARA_WXP_EMUTRAMP) && + (cur_flags & (SARA_WXP_MPROTECT | + SARA_WXP_WXORX)))) + goto error; + if (cur_flags & SARA_WXP_VERBOSE) + req_flags |= SARA_WXP_VERBOSE; + else + req_flags &= ~SARA_WXP_VERBOSE; + /* + * Except SARA_WXP_COMPLAIN and SARA_WXP_EMUTRAMP, + * any other flag can't be removed (procattr can + * only be used to make protection stricter). + */ + if (unlikely(cur_flags & (req_flags ^ cur_flags) & + ~(SARA_WXP_COMPLAIN|SARA_WXP_EMUTRAMP))) + goto error; + ret = -EINTR; + /* + * When SARA_WXP_FORCE_WXORX is on we traverse all the + * memory and remove the write permission from any area + * that is both writable and executable. + */ + if (req_flags & SARA_WXP_FORCE_WXORX) { + if (down_write_killable(¤t->mm->mmap_sem)) + goto error; + for (vma = current->mm->mmap; vma; vma = vma->vm_next) { + if (vma->vm_flags & VM_EXEC && + vma->vm_flags & VM_WRITE) { + vma->vm_flags &= ~VM_WRITE; + vma_set_page_prot(vma); + change_protection(vma, + vma->vm_start, + vma->vm_end, + vma->vm_page_prot, + 0, + 0); + } + } + up_write(¤t->mm->mmap_sem); + } + get_sara_wxp_flags(new) = req_flags & ~SARA_WXP_FORCE_WXORX; + commit_creds(new); + ret = size; + goto out; + +error: + abort_creds(new); +out: + kfree(buf); + return ret; +} + static struct security_hook_list wxprot_hooks[] __ro_after_init = { LSM_HOOK_INIT(bprm_set_creds, sara_bprm_set_creds), LSM_HOOK_INIT(check_vmflags, sara_check_vmflags), @@ -547,6 +695,8 @@ static inline int sara_pagefault_handler_x86_64(struct pt_regs *regs) #ifdef CONFIG_SECURITY_SARA_WXPROT_EMUTRAMP LSM_HOOK_INIT(pagefault_handler, sara_pagefault_handler_x86), #endif + LSM_HOOK_INIT(getprocattr, sara_getprocattr), + LSM_HOOK_INIT(setprocattr, sara_setprocattr), }; struct binary_config_header {