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=-8.4 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=unavailable 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 46BDAC33CAD for ; Mon, 13 Jan 2020 10:51:09 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 1CE8220661 for ; Mon, 13 Jan 2020 10:51:09 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=chromium.org header.i=@chromium.org header.b="oKkpYKtv" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726109AbgAMKvI (ORCPT ); Mon, 13 Jan 2020 05:51:08 -0500 Received: from mail-wr1-f66.google.com ([209.85.221.66]:44374 "EHLO mail-wr1-f66.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726133AbgAMKvE (ORCPT ); Mon, 13 Jan 2020 05:51:04 -0500 Received: by mail-wr1-f66.google.com with SMTP id q10so8025885wrm.11 for ; Mon, 13 Jan 2020 02:51:03 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=chromium.org; s=google; h=from:date:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to:user-agent; bh=rX6hYkQTcPkxFSQTp22iI/GTbRzDTSn2mT2N78MPltg=; b=oKkpYKtvG22DswPrnQPe4mDphOZzPeWS9Fm/gBtPFXIi/eh1IzHY8X22AlrD5VKaYE s+qOTZJe21UPh7e2M2/VVXjI1lW86ypWRIgklVRlnZXV2m3TNbBYjdeCk1bOikndC3V+ aTL2Zqv9kyPeC8epB3SLemTlwjlE2X2XmGN7A= X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:from:date:to:cc:subject:message-id:references :mime-version:content-disposition:in-reply-to:user-agent; bh=rX6hYkQTcPkxFSQTp22iI/GTbRzDTSn2mT2N78MPltg=; b=KkbsZzoY1gQ6VWPi/DsBs7t7XQg4MpJGnAzs9S+flNyZup+tyEnOwr3LP+c+/oACZw bLut1gGxmEN67ed/NL5zraKlfEF/SKxPmM2txSWQO+Z2l8oKwKLReEh6jNL+w2EjVl+i mpjIcvyUL3gIt76FswmTlpG4OP1Id+V2n2mLEweUaH4WU1zEC2HGrbdDz/uTl9ZOv1wH AnSrs22vLMYuslMNFk5+bSgpsyO3HMlqzVtFJd623s7jypWE2OnJtMMq93zxejpVsbRy ypYIOsidpXxe/y/Z3pNHeAcHqqUAffyTMkB0QerLWtyROKAubq9880bdISWCVDhhARtu A1zA== X-Gm-Message-State: APjAAAWWmpJ5Kh6F5VbSgB/VH+scjU+czbMcqamQRDf+Ffcs1jJnEf9w Hfbm9Fafr0VAbVnFqm6FmyOHuQ== X-Google-Smtp-Source: APXvYqzk/HkmF6+cavSIKEIJ+Fq8mnrnSFzOKUU4OvMZdAPLWjQsZPS2kwS1LaOaiSPQQo0ar0Br5A== X-Received: by 2002:adf:ef8b:: with SMTP id d11mr12548851wro.45.1578912662627; Mon, 13 Jan 2020 02:51:02 -0800 (PST) Received: from google.com ([2a00:79e0:42:204:8a21:ba0c:bb42:75ec]) by smtp.gmail.com with ESMTPSA id s3sm13791867wmh.25.2020.01.13.02.51.01 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 13 Jan 2020 02:51:02 -0800 (PST) From: KP Singh X-Google-Original-From: KP Singh Date: Mon, 13 Jan 2020 11:51:00 +0100 To: Florent Revest Cc: linux-integrity@vger.kernel.org, kpsingh@chromium.org, mjg59@google.com, zohar@linux.ibm.com, nramas@linux.microsoft.com, linux-kernel@vger.kernel.org, linux-security-module@vger.kernel.org, Florent Revest Subject: Re: [PATCH v3] ima: add the ability to query the cached hash of a given file Message-ID: <20200113105100.GA31000@google.com> References: <20200113094244.26678-1-revest@chromium.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200113094244.26678-1-revest@chromium.org> User-Agent: Mutt/1.10.1 (2018-07-13) Sender: owner-linux-security-module@vger.kernel.org Precedence: bulk List-ID: On 13-Jan 10:42, Florent Revest wrote: > From: Florent Revest > > This allows other parts of the kernel (perhaps a stacked LSM allowing > system monitoring, eg. the proposed KRSI LSM [1]) to retrieve the hash > of a given file from IMA if it's present in the iint cache. > > It's true that the existence of the hash means that it's also in the > audit logs or in /sys/kernel/security/ima/ascii_runtime_measurements, > but it can be difficult to pull that information out for every > subsequent exec. This is especially true if a given host has been up > for a long time and the file was first measured a long time ago. > > It should be kept in mind that this function gives access to cached > entries which can be removed, for instance on security_inode_free(). > > This is based on Peter Moody's patch: > https://sourceforge.net/p/linux-ima/mailman/message/33036180/ > > [1] https://lkml.org/lkml/2019/9/10/393 > > Signed-off-by: Florent Revest Reviewed-by: KP Singh > --- > include/linux/ima.h | 6 ++++ > security/integrity/ima/ima_main.c | 49 +++++++++++++++++++++++++++++++ > 2 files changed, 55 insertions(+) > > diff --git a/include/linux/ima.h b/include/linux/ima.h > index f4644c54f648..1659217e9b60 100644 > --- a/include/linux/ima.h > +++ b/include/linux/ima.h > @@ -23,6 +23,7 @@ extern int ima_read_file(struct file *file, enum kernel_read_file_id id); > extern int ima_post_read_file(struct file *file, void *buf, loff_t size, > enum kernel_read_file_id id); > extern void ima_post_path_mknod(struct dentry *dentry); > +extern int ima_file_hash(struct file *file, char *buf, size_t buf_size); > extern void ima_kexec_cmdline(const void *buf, int size); > > #ifdef CONFIG_IMA_KEXEC > @@ -91,6 +92,11 @@ static inline void ima_post_path_mknod(struct dentry *dentry) > return; > } > > +static inline int ima_file_hash(struct file *file, char *buf, size_t buf_size) > +{ > + return -EOPNOTSUPP; > +} > + > static inline void ima_kexec_cmdline(const void *buf, int size) {} > #endif /* CONFIG_IMA */ > > diff --git a/security/integrity/ima/ima_main.c b/security/integrity/ima/ima_main.c > index 2272c3255c7d..9fe949c6a530 100644 > --- a/security/integrity/ima/ima_main.c > +++ b/security/integrity/ima/ima_main.c > @@ -445,6 +445,55 @@ int ima_file_check(struct file *file, int mask) > } > EXPORT_SYMBOL_GPL(ima_file_check); > > +/** > + * ima_file_hash - return the stored measurement if a file has been hashed and > + * is in the iint cache. > + * @file: pointer to the file > + * @buf: buffer in which to store the hash > + * @buf_size: length of the buffer > + * > + * On success, return the hash algorithm (as defined in the enum hash_algo). > + * If buf is not NULL, this function also outputs the hash into buf. > + * If the hash is larger than buf_size, then only buf_size bytes will be copied. > + * It generally just makes sense to pass a buffer capable of holding the largest > + * possible hash: IMA_MAX_DIGEST_SIZE. > + * The file hash returned is based on the entire file, including the appended > + * signature. > + * > + * If IMA is disabled or if no measurement is available, return -EOPNOTSUPP. > + * If the parameters are incorrect, return -EINVAL. > + */ > +int ima_file_hash(struct file *file, char *buf, size_t buf_size) > +{ > + struct inode *inode; > + struct integrity_iint_cache *iint; > + int hash_algo; > + > + if (!file) > + return -EINVAL; > + > + if (!ima_policy_flag) > + return -EOPNOTSUPP; > + > + inode = file_inode(file); > + iint = integrity_iint_find(inode); > + if (!iint) > + return -EOPNOTSUPP; > + > + mutex_lock(&iint->mutex); > + if (buf) { > + size_t copied_size; > + > + copied_size = min_t(size_t, iint->ima_hash->length, buf_size); > + memcpy(buf, iint->ima_hash->digest, copied_size); > + } > + hash_algo = iint->ima_hash->algo; > + mutex_unlock(&iint->mutex); > + > + return hash_algo; > +} > +EXPORT_SYMBOL_GPL(ima_file_hash); > + > /** > * ima_post_create_tmpfile - mark newly created tmpfile as new > * @file : newly created tmpfile > -- > 2.25.0.rc1.283.g88dfdc4193-goog >