From patchwork Wed Apr 29 07:39:33 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Roberto Sassu X-Patchwork-Id: 11516315 Return-Path: Received: from mail.kernel.org (pdx-korg-mail-1.web.codeaurora.org [172.30.200.123]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id 0D47281 for ; Wed, 29 Apr 2020 07:42:24 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id EEF8D2087E for ; Wed, 29 Apr 2020 07:42:23 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726636AbgD2HmM (ORCPT ); Wed, 29 Apr 2020 03:42:12 -0400 Received: from lhrrgout.huawei.com ([185.176.76.210]:2125 "EHLO huawei.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1726477AbgD2HmL (ORCPT ); Wed, 29 Apr 2020 03:42:11 -0400 Received: from lhreml709-chm.china.huawei.com (unknown [172.18.7.107]) by Forcepoint Email with ESMTP id B962F5BF6C391C3AAF11; Wed, 29 Apr 2020 08:42:09 +0100 (IST) Received: from fraeml714-chm.china.huawei.com (10.206.15.33) by lhreml709-chm.china.huawei.com (10.201.108.58) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA256_P256) id 15.1.1913.5; Wed, 29 Apr 2020 08:42:09 +0100 Received: from roberto-HP-EliteDesk-800-G2-DM-65W.huawei.com (10.204.65.160) by fraeml714-chm.china.huawei.com (10.206.15.33) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA256) id 15.1.1913.5; Wed, 29 Apr 2020 09:42:08 +0200 From: Roberto Sassu To: , , , CC: , , , , , Roberto Sassu Subject: [RFC][PATCH 1/3] evm: Move hooks outside LSM infrastructure Date: Wed, 29 Apr 2020 09:39:33 +0200 Message-ID: <20200429073935.11913-1-roberto.sassu@huawei.com> X-Mailer: git-send-email 2.17.1 MIME-Version: 1.0 X-Originating-IP: [10.204.65.160] X-ClientProxiedBy: lhreml701-chm.china.huawei.com (10.201.108.50) To fraeml714-chm.china.huawei.com (10.206.15.33) X-CFilter-Loop: Reflected Sender: linux-fsdevel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org EVM is a module for the protection of the integrity of file metadata. It protects security-relevant extended attributes, and some file attributes such as the UID and the GID. It protects their integrity with an HMAC or with a signature. What makes EVM different from other LSMs is that it makes a security decision depending on multiple pieces of information, which cannot be managed atomically by the system. Example: cp -a file.orig file.dest If security.selinux, security.ima and security.evm must be preserved, cp will invoke setxattr() for each xattr, and EVM performs a verification during each operation. The problem is that copying security.evm from file.orig to file.dest will likely break the following EVM verifications if some metadata still have to be copied. EVM has no visibility on the metadata of the source file, so it cannot determine when the copy can be considered complete. On the other hand, EVM has to check metadata during every operation to ensure that there is no transition from corrupted metadata, e.g. after an offline attack, to valid ones after the operation. An HMAC update would prevent the corruption to be detected, as the HMAC on the new values would be correct. Thus, to avoid this issue, EVM has to return an error to the system call so that its execution will be interrupted. A solution that would satisfy both requirements, not breaking user space applications and detecting corrupted metadata is to let metadata operations be completed successfully and to pass the result of the EVM verification from the pre hooks to the post hooks. In this way, the HMAC update can be avoided if the verification wasn't successful. This approach will bring another important benefit: it is no longer required that every file has a valid HMAC or signature. Instead of always enforcing metadata integrity, even when it is not relevant for IMA, EVM will let IMA decide for files selected with the appraisal policy, depending on the result of the requested verification. The main problem is that the result of the verification currently cannot be passed from the pre hooks to the post hooks, due to how the LSM API is defined. A possible solution would be to use integrity_iint_cache for this purpose, but it will increase the memory pressure, as new structures will be allocated also for metadata operations, not only for measurement, appraisal and audit. Another solution would be to extend the LSM API, but it seems not worthwhile as EVM would be the only module getting a benefit from this change. Given that pre and post hooks are called from the same system call, a more efficient solution seems to move the hooks outside the LSM infrastructure, so that the return value of the pre hooks can be passed to the post hooks. A predefined error (-EAGAIN) will be used to signal to the system call to continue the execution. Otherwise, if the pre hooks return -EPERM, the system calls will behave as before and will immediately return before metadata are changed. Overview of the changes: evm_inode_init_security() LSM (no change) evm_inode_setxattr() LSM -> vfs_setxattr() evm_inode_post_setxattr() LSM -> vfs_setxattr() evm_inode_removexattr() LSM -> vfs_removexattr() evm_inode_post_removexattr() vfs_removexattr() (no change) evm_inode_setattr() LSM -> vfs_setattr() evm_inode_post_setattr() vfs_setattr() (no change) evm_verifyxattr() outside LSM (no change) Signed-off-by: Roberto Sassu --- fs/attr.c | 5 ++++- fs/xattr.c | 17 +++++++++++++++-- security/security.c | 18 +++--------------- 3 files changed, 22 insertions(+), 18 deletions(-) diff --git a/fs/attr.c b/fs/attr.c index b4bbdbd4c8ca..8f26d7d2e3b4 100644 --- a/fs/attr.c +++ b/fs/attr.c @@ -224,7 +224,7 @@ int notify_change(struct dentry * dentry, struct iattr * attr, struct inode **de { struct inode *inode = dentry->d_inode; umode_t mode = inode->i_mode; - int error; + int error, evm_error; struct timespec64 now; unsigned int ia_valid = attr->ia_valid; @@ -328,6 +328,9 @@ int notify_change(struct dentry * dentry, struct iattr * attr, struct inode **de error = security_inode_setattr(dentry, attr); if (error) return error; + evm_error = evm_inode_setattr(dentry, attr); + if (evm_error) + return evm_error; error = try_break_deleg(inode, delegated_inode); if (error) return error; diff --git a/fs/xattr.c b/fs/xattr.c index e13265e65871..3b323b75b741 100644 --- a/fs/xattr.c +++ b/fs/xattr.c @@ -183,6 +183,7 @@ int __vfs_setxattr_noperm(struct dentry *dentry, const char *name, fsnotify_xattr(dentry); security_inode_post_setxattr(dentry, name, value, size, flags); + evm_inode_post_setxattr(dentry, name, value, size); } } else { if (unlikely(is_bad_inode(inode))) @@ -210,7 +211,7 @@ vfs_setxattr(struct dentry *dentry, const char *name, const void *value, size_t size, int flags) { struct inode *inode = dentry->d_inode; - int error; + int error, evm_error; error = xattr_permission(inode, name, MAY_WRITE); if (error) @@ -221,6 +222,12 @@ vfs_setxattr(struct dentry *dentry, const char *name, const void *value, if (error) goto out; + evm_error = evm_inode_setxattr(dentry, name, value, size); + if (evm_error) { + error = evm_error; + goto out; + } + error = __vfs_setxattr_noperm(dentry, name, value, size, flags); out: @@ -382,7 +389,7 @@ int vfs_removexattr(struct dentry *dentry, const char *name) { struct inode *inode = dentry->d_inode; - int error; + int error, evm_error; error = xattr_permission(inode, name, MAY_WRITE); if (error) @@ -393,6 +400,12 @@ vfs_removexattr(struct dentry *dentry, const char *name) if (error) goto out; + evm_error = evm_inode_removexattr(dentry, name); + if (evm_error) { + error = evm_error; + goto out; + } + error = __vfs_removexattr(dentry, name); if (!error) { diff --git a/security/security.c b/security/security.c index 7fed24b9d57e..e1368ab34cee 100644 --- a/security/security.c +++ b/security/security.c @@ -1255,14 +1255,9 @@ int security_inode_permission(struct inode *inode, int mask) int security_inode_setattr(struct dentry *dentry, struct iattr *attr) { - int ret; - if (unlikely(IS_PRIVATE(d_backing_inode(dentry)))) return 0; - ret = call_int_hook(inode_setattr, 0, dentry, attr); - if (ret) - return ret; - return evm_inode_setattr(dentry, attr); + return call_int_hook(inode_setattr, 0, dentry, attr); } EXPORT_SYMBOL_GPL(security_inode_setattr); @@ -1291,10 +1286,7 @@ int security_inode_setxattr(struct dentry *dentry, const char *name, ret = cap_inode_setxattr(dentry, name, value, size, flags); if (ret) return ret; - ret = ima_inode_setxattr(dentry, name, value, size); - if (ret) - return ret; - return evm_inode_setxattr(dentry, name, value, size); + return ima_inode_setxattr(dentry, name, value, size); } void security_inode_post_setxattr(struct dentry *dentry, const char *name, @@ -1303,7 +1295,6 @@ void security_inode_post_setxattr(struct dentry *dentry, const char *name, if (unlikely(IS_PRIVATE(d_backing_inode(dentry)))) return; call_void_hook(inode_post_setxattr, dentry, name, value, size, flags); - evm_inode_post_setxattr(dentry, name, value, size); } int security_inode_getxattr(struct dentry *dentry, const char *name) @@ -1335,10 +1326,7 @@ int security_inode_removexattr(struct dentry *dentry, const char *name) ret = cap_inode_removexattr(dentry, name); if (ret) return ret; - ret = ima_inode_removexattr(dentry, name); - if (ret) - return ret; - return evm_inode_removexattr(dentry, name); + return ima_inode_removexattr(dentry, name); } int security_inode_need_killpriv(struct dentry *dentry) From patchwork Wed Apr 29 07:39:34 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Roberto Sassu X-Patchwork-Id: 11516311 Return-Path: Received: from mail.kernel.org (pdx-korg-mail-1.web.codeaurora.org [172.30.200.123]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id E43F292A for ; Wed, 29 Apr 2020 07:42:22 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id CDE252085B for ; Wed, 29 Apr 2020 07:42:22 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726681AbgD2HmO (ORCPT ); Wed, 29 Apr 2020 03:42:14 -0400 Received: from lhrrgout.huawei.com ([185.176.76.210]:2126 "EHLO huawei.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1726511AbgD2HmM (ORCPT ); Wed, 29 Apr 2020 03:42:12 -0400 Received: from lhreml708-chm.china.huawei.com (unknown [172.18.7.106]) by Forcepoint Email with ESMTP id 779649403968A3C98473; Wed, 29 Apr 2020 08:42:10 +0100 (IST) Received: from fraeml714-chm.china.huawei.com (10.206.15.33) by lhreml708-chm.china.huawei.com (10.201.108.57) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA256_P256) id 15.1.1913.5; Wed, 29 Apr 2020 08:42:10 +0100 Received: from roberto-HP-EliteDesk-800-G2-DM-65W.huawei.com (10.204.65.160) by fraeml714-chm.china.huawei.com (10.206.15.33) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA256) id 15.1.1913.5; Wed, 29 Apr 2020 09:42:09 +0200 From: Roberto Sassu To: , , , CC: , , , , , Roberto Sassu Subject: [RFC][PATCH 2/3] evm: Extend API of post hooks to pass the result of pre hooks Date: Wed, 29 Apr 2020 09:39:34 +0200 Message-ID: <20200429073935.11913-2-roberto.sassu@huawei.com> X-Mailer: git-send-email 2.17.1 In-Reply-To: <20200429073935.11913-1-roberto.sassu@huawei.com> References: <20200429073935.11913-1-roberto.sassu@huawei.com> MIME-Version: 1.0 X-Originating-IP: [10.204.65.160] X-ClientProxiedBy: lhreml701-chm.china.huawei.com (10.201.108.50) To fraeml714-chm.china.huawei.com (10.206.15.33) X-CFilter-Loop: Reflected Sender: linux-fsdevel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org This patch extends the API of post hooks to pass the result returned by the pre hooks. Given that now this information is available, post hooks can stop before updating the HMAC if the result of the pre hook is not zero. They still reset the result of the last verification, stored in the integrity_iint_cache, to ensure that file metadata are re-evaluated after update. Signed-off-by: Roberto Sassu --- fs/attr.c | 2 +- fs/xattr.c | 49 ++++++++++++++++++------------- include/linux/evm.h | 18 ++++++++---- security/integrity/evm/evm_main.c | 21 +++++++++++-- 4 files changed, 59 insertions(+), 31 deletions(-) diff --git a/fs/attr.c b/fs/attr.c index 8f26d7d2e3b4..6ce60e1eba34 100644 --- a/fs/attr.c +++ b/fs/attr.c @@ -343,7 +343,7 @@ int notify_change(struct dentry * dentry, struct iattr * attr, struct inode **de if (!error) { fsnotify_change(dentry, ia_valid); ima_inode_post_setattr(dentry); - evm_inode_post_setattr(dentry, ia_valid); + evm_inode_post_setattr(dentry, ia_valid, evm_error); } return error; diff --git a/fs/xattr.c b/fs/xattr.c index 3b323b75b741..b1fd2aa481a8 100644 --- a/fs/xattr.c +++ b/fs/xattr.c @@ -151,24 +151,8 @@ __vfs_setxattr(struct dentry *dentry, struct inode *inode, const char *name, } EXPORT_SYMBOL(__vfs_setxattr); -/** - * __vfs_setxattr_noperm - perform setxattr operation without performing - * permission checks. - * - * @dentry - object to perform setxattr on - * @name - xattr name to set - * @value - value to set @name to - * @size - size of @value - * @flags - flags to pass into filesystem operations - * - * returns the result of the internal setxattr or setsecurity operations. - * - * This function requires the caller to lock the inode's i_mutex before it - * is executed. It also assumes that the caller will make the appropriate - * permission checks. - */ -int __vfs_setxattr_noperm(struct dentry *dentry, const char *name, - const void *value, size_t size, int flags) +static int __vfs_setxattr_noperm_evm(struct dentry *dentry, const char *name, + const void *value, size_t size, int flags, int evm_error) { struct inode *inode = dentry->d_inode; int error = -EAGAIN; @@ -183,7 +167,8 @@ int __vfs_setxattr_noperm(struct dentry *dentry, const char *name, fsnotify_xattr(dentry); security_inode_post_setxattr(dentry, name, value, size, flags); - evm_inode_post_setxattr(dentry, name, value, size); + evm_inode_post_setxattr(dentry, name, value, size, + evm_error); } } else { if (unlikely(is_bad_inode(inode))) @@ -205,6 +190,27 @@ int __vfs_setxattr_noperm(struct dentry *dentry, const char *name, return error; } +/** + * __vfs_setxattr_noperm - perform setxattr operation without performing + * permission checks. + * + * @dentry - object to perform setxattr on + * @name - xattr name to set + * @value - value to set @name to + * @size - size of @value + * @flags - flags to pass into filesystem operations + * + * returns the result of the internal setxattr or setsecurity operations. + * + * This function requires the caller to lock the inode's i_mutex before it + * is executed. It also assumes that the caller will make the appropriate + * permission checks. + */ +int __vfs_setxattr_noperm(struct dentry *dentry, const char *name, + const void *value, size_t size, int flags) +{ + return __vfs_setxattr_noperm_evm(dentry, name, value, size, flags, 0); +} int vfs_setxattr(struct dentry *dentry, const char *name, const void *value, @@ -228,7 +234,8 @@ vfs_setxattr(struct dentry *dentry, const char *name, const void *value, goto out; } - error = __vfs_setxattr_noperm(dentry, name, value, size, flags); + error = __vfs_setxattr_noperm_evm(dentry, name, value, size, flags, + evm_error); out: inode_unlock(inode); @@ -410,7 +417,7 @@ vfs_removexattr(struct dentry *dentry, const char *name) if (!error) { fsnotify_xattr(dentry); - evm_inode_post_removexattr(dentry, name); + evm_inode_post_removexattr(dentry, name, evm_error); } out: diff --git a/include/linux/evm.h b/include/linux/evm.h index 8302bc29bb35..cc23d2248d3e 100644 --- a/include/linux/evm.h +++ b/include/linux/evm.h @@ -22,16 +22,19 @@ extern enum integrity_status evm_verifyxattr(struct dentry *dentry, size_t xattr_value_len, struct integrity_iint_cache *iint); extern int evm_inode_setattr(struct dentry *dentry, struct iattr *attr); -extern void evm_inode_post_setattr(struct dentry *dentry, int ia_valid); +extern void evm_inode_post_setattr(struct dentry *dentry, int ia_valid, + int evm_pre_error); extern int evm_inode_setxattr(struct dentry *dentry, const char *name, const void *value, size_t size); extern void evm_inode_post_setxattr(struct dentry *dentry, const char *xattr_name, const void *xattr_value, - size_t xattr_value_len); + size_t xattr_value_len, + int evm_pre_error); extern int evm_inode_removexattr(struct dentry *dentry, const char *xattr_name); extern void evm_inode_post_removexattr(struct dentry *dentry, - const char *xattr_name); + const char *xattr_name, + int evm_pre_error); extern int evm_inode_init_security(struct inode *inode, const struct xattr *xattr_array, struct xattr *evm); @@ -66,7 +69,8 @@ static inline int evm_inode_setattr(struct dentry *dentry, struct iattr *attr) return 0; } -static inline void evm_inode_post_setattr(struct dentry *dentry, int ia_valid) +static inline void evm_inode_post_setattr(struct dentry *dentry, int ia_valid, + int evm_pre_error) { return; } @@ -80,7 +84,8 @@ static inline int evm_inode_setxattr(struct dentry *dentry, const char *name, static inline void evm_inode_post_setxattr(struct dentry *dentry, const char *xattr_name, const void *xattr_value, - size_t xattr_value_len) + size_t xattr_value_len, + int evm_pre_error) { return; } @@ -92,7 +97,8 @@ static inline int evm_inode_removexattr(struct dentry *dentry, } static inline void evm_inode_post_removexattr(struct dentry *dentry, - const char *xattr_name) + const char *xattr_name, + int evm_pre_error) { return; } diff --git a/security/integrity/evm/evm_main.c b/security/integrity/evm/evm_main.c index d361d7fdafc4..ca9eaef7058b 100644 --- a/security/integrity/evm/evm_main.c +++ b/security/integrity/evm/evm_main.c @@ -422,6 +422,7 @@ static void evm_reset_status(struct inode *inode) * @xattr_name: pointer to the affected extended attribute name * @xattr_value: pointer to the new extended attribute value * @xattr_value_len: pointer to the new extended attribute value length + * @evm_pre_error: error returned by evm_inode_setxattr() * * Update the HMAC stored in 'security.evm' to reflect the change. * @@ -430,7 +431,8 @@ static void evm_reset_status(struct inode *inode) * i_mutex lock. */ void evm_inode_post_setxattr(struct dentry *dentry, const char *xattr_name, - const void *xattr_value, size_t xattr_value_len) + const void *xattr_value, size_t xattr_value_len, + int evm_pre_error) { if (!evm_key_loaded() || (!evm_protected_xattr(xattr_name) && !posix_xattr_acl(xattr_name))) @@ -438,6 +440,9 @@ void evm_inode_post_setxattr(struct dentry *dentry, const char *xattr_name, evm_reset_status(dentry->d_inode); + if (evm_pre_error) + return; + evm_update_evmxattr(dentry, xattr_name, xattr_value, xattr_value_len); } @@ -445,19 +450,24 @@ void evm_inode_post_setxattr(struct dentry *dentry, const char *xattr_name, * evm_inode_post_removexattr - update 'security.evm' after removing the xattr * @dentry: pointer to the affected dentry * @xattr_name: pointer to the affected extended attribute name + * @evm_pre_error: error returned by evm_inode_removexattr() * * Update the HMAC stored in 'security.evm' to reflect removal of the xattr. * * No need to take the i_mutex lock here, as this function is called from * vfs_removexattr() which takes the i_mutex. */ -void evm_inode_post_removexattr(struct dentry *dentry, const char *xattr_name) +void evm_inode_post_removexattr(struct dentry *dentry, const char *xattr_name, + int evm_pre_error) { if (!evm_key_loaded() || !evm_protected_xattr(xattr_name)) return; evm_reset_status(dentry->d_inode); + if (evm_pre_error) + return; + evm_update_evmxattr(dentry, xattr_name, NULL, 0); } @@ -495,6 +505,7 @@ int evm_inode_setattr(struct dentry *dentry, struct iattr *attr) * evm_inode_post_setattr - update 'security.evm' after modifying metadata * @dentry: pointer to the affected dentry * @ia_valid: for the UID and GID status + * @evm_pre_error: error returned by evm_inode_setattr() * * For now, update the HMAC stored in 'security.evm' to reflect UID/GID * changes. @@ -502,11 +513,15 @@ int evm_inode_setattr(struct dentry *dentry, struct iattr *attr) * This function is called from notify_change(), which expects the caller * to lock the inode's i_mutex. */ -void evm_inode_post_setattr(struct dentry *dentry, int ia_valid) +void evm_inode_post_setattr(struct dentry *dentry, int ia_valid, + int evm_pre_error) { if (!evm_key_loaded()) return; + if (evm_pre_error) + return; + if (ia_valid & (ATTR_MODE | ATTR_UID | ATTR_GID)) evm_update_evmxattr(dentry, NULL, NULL, 0); } From patchwork Wed Apr 29 07:39:35 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Roberto Sassu X-Patchwork-Id: 11516307 Return-Path: Received: from mail.kernel.org (pdx-korg-mail-1.web.codeaurora.org [172.30.200.123]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id 65AB381 for ; 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Wed, 29 Apr 2020 09:42:10 +0200 From: Roberto Sassu To: , , , CC: , , , , , Roberto Sassu Subject: [RFC][PATCH 3/3] evm: Return -EAGAIN to ignore verification failures Date: Wed, 29 Apr 2020 09:39:35 +0200 Message-ID: <20200429073935.11913-3-roberto.sassu@huawei.com> X-Mailer: git-send-email 2.17.1 In-Reply-To: <20200429073935.11913-1-roberto.sassu@huawei.com> References: <20200429073935.11913-1-roberto.sassu@huawei.com> MIME-Version: 1.0 X-Originating-IP: [10.204.65.160] X-ClientProxiedBy: lhreml701-chm.china.huawei.com (10.201.108.50) To fraeml714-chm.china.huawei.com (10.206.15.33) X-CFilter-Loop: Reflected Sender: linux-fsdevel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org By default, EVM maintains the same behavior as before hooks were moved outside the LSM infrastructure. When EVM returns -EPERM, callers stop their execution and return the error to user space. This patch introduces a new mode, called ignore, that changes the return value of the pre hooks from -EPERM to -EAGAIN. It also modifies the callers of pre and post hooks to continue the execution if -EAGAIN is returned. The error is then handled by the post hooks. The only error that is not ignored is when user space is trying to modify a portable signature. Once that signature has been validated with the current values of metadata, there is no valid reason to change them. From user space perspective, operations on corrupted metadata are successfully performed but post hooks didn't update the HMAC. At the next IMA verification, when evm_verifyxattr() is called, corruption will be detected and access will be denied. Signed-off-by: Roberto Sassu --- fs/attr.c | 2 +- fs/xattr.c | 4 ++-- security/integrity/evm/evm_main.c | 23 +++++++++++++++++------ 3 files changed, 20 insertions(+), 9 deletions(-) diff --git a/fs/attr.c b/fs/attr.c index 6ce60e1eba34..6370e2f3704d 100644 --- a/fs/attr.c +++ b/fs/attr.c @@ -329,7 +329,7 @@ int notify_change(struct dentry * dentry, struct iattr * attr, struct inode **de if (error) return error; evm_error = evm_inode_setattr(dentry, attr); - if (evm_error) + if (evm_error && evm_error != -EAGAIN) return evm_error; error = try_break_deleg(inode, delegated_inode); if (error) diff --git a/fs/xattr.c b/fs/xattr.c index b1fd2aa481a8..73f0f3cd6c45 100644 --- a/fs/xattr.c +++ b/fs/xattr.c @@ -229,7 +229,7 @@ vfs_setxattr(struct dentry *dentry, const char *name, const void *value, goto out; evm_error = evm_inode_setxattr(dentry, name, value, size); - if (evm_error) { + if (evm_error && evm_error != -EAGAIN) { error = evm_error; goto out; } @@ -408,7 +408,7 @@ vfs_removexattr(struct dentry *dentry, const char *name) goto out; evm_error = evm_inode_removexattr(dentry, name); - if (evm_error) { + if (evm_error && evm_error != -EAGAIN) { error = evm_error; goto out; } diff --git a/security/integrity/evm/evm_main.c b/security/integrity/evm/evm_main.c index ca9eaef7058b..ef09caa3bbcf 100644 --- a/security/integrity/evm/evm_main.c +++ b/security/integrity/evm/evm_main.c @@ -54,11 +54,13 @@ static struct xattr_list evm_config_default_xattrnames[] = { LIST_HEAD(evm_config_xattrnames); -static int evm_fixmode; +static int evm_fixmode, evm_ignoremode __ro_after_init; static int __init evm_set_fixmode(char *str) { if (strncmp(str, "fix", 3) == 0) evm_fixmode = 1; + if (strncmp(str, "ignore", 6) == 0) + evm_ignoremode = 1; return 0; } __setup("evm=", evm_set_fixmode); @@ -311,6 +313,7 @@ static int evm_protect_xattr(struct dentry *dentry, const char *xattr_name, const void *xattr_value, size_t xattr_value_len) { enum integrity_status evm_status; + int rc = -EPERM; if (strcmp(xattr_name, XATTR_NAME_EVM) == 0) { if (!capable(CAP_SYS_ADMIN)) @@ -345,12 +348,17 @@ static int evm_protect_xattr(struct dentry *dentry, const char *xattr_name, -EPERM, 0); } out: - if (evm_status != INTEGRITY_PASS) + if (evm_status != INTEGRITY_PASS) { + if (evm_ignoremode && evm_status != INTEGRITY_PASS_IMMUTABLE) + rc = -EAGAIN; + integrity_audit_msg(AUDIT_INTEGRITY_METADATA, d_backing_inode(dentry), dentry->d_name.name, "appraise_metadata", integrity_status_msg[evm_status], - -EPERM, 0); - return evm_status == INTEGRITY_PASS ? 0 : -EPERM; + rc, 0); + } + + return evm_status == INTEGRITY_PASS ? 0 : rc; } /** @@ -482,6 +490,7 @@ int evm_inode_setattr(struct dentry *dentry, struct iattr *attr) { unsigned int ia_valid = attr->ia_valid; enum integrity_status evm_status; + int rc = -EPERM; /* Policy permits modification of the protected attrs even though * there's no HMAC key loaded @@ -495,10 +504,12 @@ int evm_inode_setattr(struct dentry *dentry, struct iattr *attr) if ((evm_status == INTEGRITY_PASS) || (evm_status == INTEGRITY_NOXATTRS)) return 0; + if (evm_ignoremode && evm_status != INTEGRITY_PASS_IMMUTABLE) + rc = -EAGAIN; integrity_audit_msg(AUDIT_INTEGRITY_METADATA, d_backing_inode(dentry), dentry->d_name.name, "appraise_metadata", - integrity_status_msg[evm_status], -EPERM, 0); - return -EPERM; + integrity_status_msg[evm_status], rc, 0); + return rc; } /**