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=-6.9 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 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 B171FC33CAC for ; Mon, 13 Jan 2020 09:42:26 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 7EE542084D for ; Mon, 13 Jan 2020 09:42:26 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=chromium.org header.i=@chromium.org header.b="LONkt8qU" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728746AbgAMJm0 (ORCPT ); Mon, 13 Jan 2020 04:42:26 -0500 Received: from mail-wr1-f67.google.com ([209.85.221.67]:46503 "EHLO mail-wr1-f67.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728682AbgAMJmW (ORCPT ); Mon, 13 Jan 2020 04:42:22 -0500 Received: by mail-wr1-f67.google.com with SMTP id z7so7756611wrl.13 for ; Mon, 13 Jan 2020 01:42:20 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=chromium.org; s=google; h=message-id:subject:from:to:cc:date:in-reply-to:references :user-agent:mime-version:content-transfer-encoding; bh=/AnYXrXWYvNhwGCXjTJAreL3RYx7ZKU0okhiknvPq1k=; b=LONkt8qUSVzgSpJ3vYRz5tdEdUTiIp7lBSpk8CgEbr+mU66cFuYcwYwY0Gt33ed63d Za4k2QokkwkSZrYzZ458SxLbyR6U5j4nYTd1ZGpkw/SI17H4TkFXcEXQ4D3KzgxNTSn+ bxLdeS1EG1MKd28ac5FKeVtvQ/x1eACkxMXNg= X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:message-id:subject:from:to:cc:date:in-reply-to :references:user-agent:mime-version:content-transfer-encoding; bh=/AnYXrXWYvNhwGCXjTJAreL3RYx7ZKU0okhiknvPq1k=; b=l5y5lhN/GHx1IT3Uf1m/X6UACOqcLrrPYaBg3veZ3xa77ySyvwc1fSOuLx9KzJEK8M eYLm0Wxc0167gq8mtIzZn1j4Y5oKc5CMB4yxFIzhkc7BAGtdgaeGQ7p76RqQXmkv6+ek 1/OQATi+8ofKryFzsYI5uj9boE4Ay32GMF3xitlFo7jUmk3IzRR1/GJNYOm+3nMUWDfF T34QAM/zqPgpay2jRq5YWMVvC+TKiM9g6KkfO//aiUyvUoVl/NqkhW1bn6tY2VYzgx9W DlquLs6VVcF3pnMdVKrLKSHD2ER7aYJ4++OH8ch4KY11BZAaCmNYNpOuxwpqQYEchxtm SFew== X-Gm-Message-State: APjAAAXgKgz7FfJGLtV48DEQdudUA1Pmn+NXuz2zCNm5apsVDPdU+tfS 7jztrrqywI63Vmd5O94nukn7bQ== X-Google-Smtp-Source: APXvYqxxI6qdgEBxTJuEUk3JhYcPPt1IsOdKJoSHupf9NxOVFJcQPh2xufJhPakK9fflGvmxnk0P3g== X-Received: by 2002:a5d:608a:: with SMTP id w10mr16362892wrt.136.1578908539527; Mon, 13 Jan 2020 01:42:19 -0800 (PST) Received: from ?IPv6:2a00:79e0:42:204:51d1:d96e:f72e:c8c0? ([2a00:79e0:42:204:51d1:d96e:f72e:c8c0]) by smtp.gmail.com with ESMTPSA id e18sm14474206wrr.95.2020.01.13.01.42.18 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 13 Jan 2020 01:42:19 -0800 (PST) Message-ID: Subject: Re: [PATCH v2] ima: add the ability to query the hash of a given file. From: Florent Revest To: Mimi Zohar , linux-integrity@vger.kernel.org Cc: kpsingh@chromium.org, mjg59@google.com, nramas@linux.microsoft.com, linux-kernel@vger.kernel.org, linux-security-module@vger.kernel.org, Florent Revest Date: Mon, 13 Jan 2020 10:42:18 +0100 In-Reply-To: <1578499556.5222.157.camel@linux.ibm.com> References: <20200106162524.164650-1-revest@chromium.org> <1578499556.5222.157.camel@linux.ibm.com> Content-Type: text/plain; charset="UTF-8" User-Agent: Evolution 3.30.5-1.1 MIME-Version: 1.0 Content-Transfer-Encoding: 7bit Sender: owner-linux-security-module@vger.kernel.org Precedence: bulk List-ID: On Wed, 2020-01-08 at 11:05 -0500, Mimi Zohar wrote: > On Mon, 2020-01-06 at 17:25 +0100, 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. > > > > This is based on Peter Moody's patch: > > https://sourceforge.net/p/linux-ima/mailman/message/33036180/ > > FYI, but unlike the audit log/IMA measurement list, the iint cache > entries can be removed. Refer to security_inode_free(). Perhaps > mention of this difference should be included, here, in the patch > description. Sure, I added a comment about this in a v3. > > [1] https://lkml.org/lkml/2019/9/10/393 > > > > Signed-off-by: Florent Revest > > Assuming, with the above difference, you're still interested in > having this feature upstreamed and addressing the comments above and > below: > > Reviewed-by: Mimi Zohar Thank you. Yes we are still interested in this feature! > > --- > > include/linux/ima.h | 6 ++++ > > security/integrity/ima/ima_main.c | 46 > > +++++++++++++++++++++++++++++++ > > 2 files changed, 52 insertions(+) > > > > diff --git a/include/linux/ima.h b/include/linux/ima.h > > index 6d904754d858..d621c65ba9a5 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 d7e987baf127..3799b6c6c3b8 100644 > > --- a/security/integrity/ima/ima_main.c > > +++ b/security/integrity/ima/ima_main.c > > @@ -445,6 +445,52 @@ 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. > > + * @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. > > As of Linux 5.4.y, IMA support for appended file signatures was > added. Should we indicate that the file hash returned is based on the > entire file, including the appended signature? > > Mimi Of course it never hurts to add a comment. :) I'll send a v3 with this added. > > > + * 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 > > + * > > + * 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