From patchwork Tue Sep 26 12:44:13 2017 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Steve Grubb X-Patchwork-Id: 9971935 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 37E5460365 for ; Tue, 26 Sep 2017 12:44:21 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 283E027F95 for ; Tue, 26 Sep 2017 12:44:21 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id 1C1DC2897E; Tue, 26 Sep 2017 12:44:21 +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=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 77B9227F95 for ; Tue, 26 Sep 2017 12:44:20 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S965415AbdIZMoS (ORCPT ); Tue, 26 Sep 2017 08:44:18 -0400 Received: from mx1.redhat.com ([209.132.183.28]:25385 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S936444AbdIZMoR (ORCPT ); Tue, 26 Sep 2017 08:44:17 -0400 Received: from smtp.corp.redhat.com (int-mx05.intmail.prod.int.phx2.redhat.com [10.5.11.15]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 1A5FE2CE921; Tue, 26 Sep 2017 12:44:17 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mx1.redhat.com 1A5FE2CE921 Authentication-Results: ext-mx05.extmail.prod.ext.phx2.redhat.com; dmarc=none (p=none dis=none) header.from=redhat.com Authentication-Results: ext-mx05.extmail.prod.ext.phx2.redhat.com; spf=fail smtp.mailfrom=sgrubb@redhat.com Received: from x2.localnet (ovpn-121-181.rdu2.redhat.com [10.10.121.181]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 1F43869AD7; Tue, 26 Sep 2017 12:44:14 +0000 (UTC) From: Steve Grubb To: fsdevel Cc: Linux Audit , linux-api@vger.kernel.org, Jan Kara , Amir Goldstein , Paul Moore Subject: [PATCH v5 1/1] audit: Record fanotify access control decisions Date: Tue, 26 Sep 2017 08:44:13 -0400 Message-ID: <2364937.SQ5dJnrJFp@x2> Organization: Red Hat MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.79 on 10.5.11.15 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.29]); Tue, 26 Sep 2017 12:44:17 +0000 (UTC) Sender: linux-fsdevel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP Hello, The fanotify interface allows user space daemons to make access control decisions. Under common criteria requirements, we need to optionally record decisions based on policy. This patch adds a bit mask, FAN_AUDIT, that a user space daemon can 'or' into the response decision which will tell the kernel that it made a decision and record it. It would be used something like this in user space code: response.response = FAN_DENY | FAN_AUDIT; write(fd, &response, sizeof(struct fanotify_response)); When the syscall ends, the audit system will record the decision as a AUDIT_FANOTIFY auxiliary record to denote that the reason this event occurred is the result of an access control decision from fanotify rather than DAC or MAC policy. A sample event looks like this: type=PATH msg=audit(1504310584.332:290): item=0 name="./evil-ls" inode=1319561 dev=fc:03 mode=0100755 ouid=1000 ogid=1000 rdev=00:00 obj=unconfined_u:object_r:user_home_t:s0 nametype=NORMAL type=CWD msg=audit(1504310584.332:290): cwd="/home/sgrubb" type=SYSCALL msg=audit(1504310584.332:290): arch=c000003e syscall=2 success=no exit=-1 a0=32cb3fca90 a1=0 a2=43 a3=8 items=1 ppid=901 pid=959 auid=1000 uid=1000 gid=1000 euid=1000 suid=1000 fsuid=1000 egid=1000 sgid=1000 fsgid=1000 tty=pts1 ses=3 comm="bash" exe="/usr/bin/bash" subj=unconfined_u:unconfined_r:unconfined_t: s0-s0:c0.c1023 key=(null) type=FANOTIFY msg=audit(1504310584.332:290): resp=2 Prior to using the audit flag, the developer needs to call fanotify_init or'ing in FAN_ENABLE_AUDIT to ensure that the kernel supports auditing. The calling process must also have the CAP_AUDIT_WRITE capability. Signed-off-by: sgrubb Reviewed-by: Amir Goldstein --- fs/notify/fanotify/fanotify.c | 8 +++++++- fs/notify/fanotify/fanotify_user.c | 16 +++++++++++++++- fs/notify/fdinfo.c | 3 +++ include/linux/audit.h | 7 +++++++ include/linux/fsnotify_backend.h | 1 + include/uapi/linux/audit.h | 1 + include/uapi/linux/fanotify.h | 3 +++ kernel/auditsc.c | 6 ++++++ 8 files changed, 43 insertions(+), 2 deletions(-) diff --git a/fs/notify/fanotify/fanotify.c b/fs/notify/fanotify/fanotify.c index 2fa99ae..1968d21 100644 --- a/fs/notify/fanotify/fanotify.c +++ b/fs/notify/fanotify/fanotify.c @@ -9,6 +9,7 @@ #include #include #include +#include #include "fanotify.h" @@ -78,7 +79,7 @@ static int fanotify_get_response(struct fsnotify_group *group, fsnotify_finish_user_wait(iter_info); out: /* userspace responded, convert to something usable */ - switch (event->response) { + switch (event->response & ~FAN_AUDIT) { case FAN_ALLOW: ret = 0; break; @@ -86,6 +87,11 @@ static int fanotify_get_response(struct fsnotify_group *group, default: ret = -EPERM; } + + /* Check if the response should be audited */ + if (event->response & FAN_AUDIT) + audit_fanotify(event->response & ~FAN_AUDIT); + event->response = 0; pr_debug("%s: group=%p event=%p about to return ret=%d\n", __func__, diff --git a/fs/notify/fanotify/fanotify_user.c b/fs/notify/fanotify/fanotify_user.c index 907a481..ea3c458 100644 --- a/fs/notify/fanotify/fanotify_user.c +++ b/fs/notify/fanotify/fanotify_user.c @@ -179,7 +179,7 @@ static int process_access_response(struct fsnotify_group *group, * userspace can send a valid response or we will clean it up after the * timeout */ - switch (response) { + switch (response & ~FAN_AUDIT) { case FAN_ALLOW: case FAN_DENY: break; @@ -190,6 +190,9 @@ static int process_access_response(struct fsnotify_group *group, if (fd < 0) return -EINVAL; + if ((response & FAN_AUDIT) && !group->fanotify_data.audit_enabled) + return -EINVAL; + event = dequeue_event(group, fd); if (!event) return -ENOENT; @@ -721,7 +724,11 @@ SYSCALL_DEFINE2(fanotify_init, unsigned int, flags, unsigned int, event_f_flags) if (!capable(CAP_SYS_ADMIN)) return -EPERM; +#ifdef CONFIG_AUDITSYSCALL + if (flags & ~(FAN_ALL_INIT_FLAGS | FAN_ENABLE_AUDIT)) +#else if (flags & ~FAN_ALL_INIT_FLAGS) +#endif return -EINVAL; if (event_f_flags & ~FANOTIFY_INIT_ALL_EVENT_F_BITS) @@ -805,6 +812,13 @@ SYSCALL_DEFINE2(fanotify_init, unsigned int, flags, unsigned int, event_f_flags) group->fanotify_data.max_marks = FANOTIFY_DEFAULT_MAX_MARKS; } + if (flags & FAN_ENABLE_AUDIT) { + fd = -EPERM; + if (!capable(CAP_AUDIT_WRITE)) + goto out_destroy_group; + group->fanotify_data.audit_enabled = true; + } + fd = anon_inode_getfd("[fanotify]", &fanotify_fops, group, f_flags); if (fd < 0) goto out_destroy_group; diff --git a/fs/notify/fdinfo.c b/fs/notify/fdinfo.c index dd63aa9..ed311e3 100644 --- a/fs/notify/fdinfo.c +++ b/fs/notify/fdinfo.c @@ -156,6 +156,9 @@ void fanotify_show_fdinfo(struct seq_file *m, struct file *f) if (group->fanotify_data.max_marks == UINT_MAX) flags |= FAN_UNLIMITED_MARKS; + if (group->fanotify_data.audit_enabled) + flags |= FAN_ENABLE_AUDIT; + seq_printf(m, "fanotify flags:%x event-flags:%x\n", flags, group->fanotify_data.f_flags); diff --git a/include/linux/audit.h b/include/linux/audit.h index 2150bdc..bf55732 100644 --- a/include/linux/audit.h +++ b/include/linux/audit.h @@ -360,6 +360,7 @@ extern int __audit_log_bprm_fcaps(struct linux_binprm *bprm, extern void __audit_log_capset(const struct cred *new, const struct cred *old); extern void __audit_mmap_fd(int fd, int flags); extern void __audit_log_kern_module(char *name); +extern void __audit_fanotify(unsigned int response); static inline void audit_ipc_obj(struct kern_ipc_perm *ipcp) { @@ -456,6 +457,12 @@ static inline void audit_log_kern_module(char *name) __audit_log_kern_module(name); } +static inline void audit_fanotify(unsigned int response) +{ + if (!audit_dummy_context()) + __audit_fanotify(response); +} + extern int audit_n_rules; extern int audit_signals; #else /* CONFIG_AUDITSYSCALL */ diff --git a/include/linux/fsnotify_backend.h b/include/linux/fsnotify_backend.h index c6c6931..f4131f2 100644 --- a/include/linux/fsnotify_backend.h +++ b/include/linux/fsnotify_backend.h @@ -190,6 +190,7 @@ struct fsnotify_group { int f_flags; unsigned int max_marks; struct user_struct *user; + bool audit_enabled; } fanotify_data; #endif /* CONFIG_FANOTIFY */ }; diff --git a/include/uapi/linux/audit.h b/include/uapi/linux/audit.h index 0714a66..221f8b7 100644 --- a/include/uapi/linux/audit.h +++ b/include/uapi/linux/audit.h @@ -112,6 +112,7 @@ #define AUDIT_FEATURE_CHANGE 1328 /* audit log listing feature changes */ #define AUDIT_REPLACE 1329 /* Replace auditd if this packet unanswerd */ #define AUDIT_KERN_MODULE 1330 /* Kernel Module events */ +#define AUDIT_FANOTIFY 1331 /* Fanotify access decision */ #define AUDIT_AVC 1400 /* SE Linux avc denial or grant */ #define AUDIT_SELINUX_ERR 1401 /* Internal SE Linux Errors */ diff --git a/include/uapi/linux/fanotify.h b/include/uapi/linux/fanotify.h index 030508d..5dda19a 100644 --- a/include/uapi/linux/fanotify.h +++ b/include/uapi/linux/fanotify.h @@ -35,6 +35,7 @@ #define FAN_UNLIMITED_QUEUE 0x00000010 #define FAN_UNLIMITED_MARKS 0x00000020 +#define FAN_ENABLE_AUDIT 0x00000040 #define FAN_ALL_INIT_FLAGS (FAN_CLOEXEC | FAN_NONBLOCK | \ FAN_ALL_CLASS_BITS | FAN_UNLIMITED_QUEUE |\ @@ -99,6 +100,8 @@ struct fanotify_response { /* Legit userspace responses to a _PERM event */ #define FAN_ALLOW 0x01 #define FAN_DENY 0x02 +#define FAN_AUDIT 0x10 /* Bit mask to create audit record for result */ + /* No fd set in event */ #define FAN_NOFD -1 diff --git a/kernel/auditsc.c b/kernel/auditsc.c index 3260ba2..e046de8 100644 --- a/kernel/auditsc.c +++ b/kernel/auditsc.c @@ -2390,6 +2390,12 @@ void __audit_log_kern_module(char *name) context->type = AUDIT_KERN_MODULE; } +void __audit_fanotify(unsigned int response) +{ + audit_log(current->audit_context, GFP_KERNEL, + AUDIT_FANOTIFY, "resp=%u", response); +} + static void audit_log_task(struct audit_buffer *ab) { kuid_t auid, uid;