From patchwork Wed Sep 23 19:20:10 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Tushar Sugandhi X-Patchwork-Id: 11795551 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 D51B1618 for ; Wed, 23 Sep 2020 19:20:40 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id A931321D92 for ; Wed, 23 Sep 2020 19:20:40 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=linux.microsoft.com header.i=@linux.microsoft.com header.b="jchluQdF" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726802AbgIWTU3 (ORCPT ); Wed, 23 Sep 2020 15:20:29 -0400 Received: from linux.microsoft.com ([13.77.154.182]:47420 "EHLO linux.microsoft.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726763AbgIWTUX (ORCPT ); Wed, 23 Sep 2020 15:20:23 -0400 Received: from tusharsu-Ubuntu.lan (c-71-197-163-6.hsd1.wa.comcast.net [71.197.163.6]) by linux.microsoft.com (Postfix) with ESMTPSA id 602502089E59; Wed, 23 Sep 2020 12:20:21 -0700 (PDT) DKIM-Filter: OpenDKIM Filter v2.11.0 linux.microsoft.com 602502089E59 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.microsoft.com; s=default; t=1600888821; bh=CeqH2fYkLev2SJspNAVR1dakUWyzaHtLEkKWdj02GVY=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=jchluQdFaJAGEDwKfZt61ntxdfJSXObOh535SgxUbztshSKNqeew34hyvMV8qjwLp OJ9lgtx/zOI2sQGzBxW/4wz++B5UZVHTcQAea8dTDwujRdAsbh27WpXdGuS/UO4LwD Zohe/JXbVb5L+mj3rqsC7BDPuL5gQ39Nu1WJWTU8= From: Tushar Sugandhi To: zohar@linux.ibm.com, stephen.smalley.work@gmail.com, casey@schaufler-ca.com, agk@redhat.com, snitzer@redhat.com, gmazyland@gmail.com Cc: tyhicks@linux.microsoft.com, sashal@kernel.org, jmorris@namei.org, nramas@linux.microsoft.com, linux-integrity@vger.kernel.org, selinux@vger.kernel.org, linux-security-module@vger.kernel.org, linux-kernel@vger.kernel.org, dm-devel@redhat.com Subject: [PATCH v4 5/6] IMA: add hook to measure critical data from kernel components Date: Wed, 23 Sep 2020 12:20:10 -0700 Message-Id: <20200923192011.5293-6-tusharsu@linux.microsoft.com> X-Mailer: git-send-email 2.17.1 In-Reply-To: <20200923192011.5293-1-tusharsu@linux.microsoft.com> References: <20200923192011.5293-1-tusharsu@linux.microsoft.com> Precedence: bulk List-ID: X-Mailing-List: linux-integrity@vger.kernel.org Currently, IMA does not provide a generic function for kernel components to measure their data. A generic function provided by IMA would enable various parts of the kernel with easier and faster on-boarding to use IMA infrastructure, would avoid code duplication, and consistent usage of IMA policy option "data_sources:=" across the kernel. Add a new IMA func CRITICAL_DATA and a corresponding IMA hook ima_measure_critical_data() to support measuring various critical kernel components. Limit the measurement to the components that are specified in the IMA policy - CRITICAL_DATA+data_sources. Signed-off-by: Tushar Sugandhi --- Documentation/ABI/testing/ima_policy | 8 ++++++- include/linux/ima.h | 8 +++++++ security/integrity/ima/ima.h | 1 + security/integrity/ima/ima_api.c | 2 +- security/integrity/ima/ima_main.c | 26 +++++++++++++++++++++ security/integrity/ima/ima_policy.c | 34 ++++++++++++++++++++++++---- 6 files changed, 72 insertions(+), 7 deletions(-) diff --git a/Documentation/ABI/testing/ima_policy b/Documentation/ABI/testing/ima_policy index a81cf79fb255..d33bb51309fc 100644 --- a/Documentation/ABI/testing/ima_policy +++ b/Documentation/ABI/testing/ima_policy @@ -29,7 +29,7 @@ Description: base: func:= [BPRM_CHECK][MMAP_CHECK][CREDS_CHECK][FILE_CHECK][MODULE_CHECK] [FIRMWARE_CHECK] [KEXEC_KERNEL_CHECK] [KEXEC_INITRAMFS_CHECK] - [KEXEC_CMDLINE] [KEY_CHECK] + [KEXEC_CMDLINE] [KEY_CHECK] [CRITICAL_DATA] mask:= [[^]MAY_READ] [[^]MAY_WRITE] [[^]MAY_APPEND] [[^]MAY_EXEC] fsmagic:= hex value @@ -51,6 +51,8 @@ Description: data_sources:= list of kernel components (eg, selinux|apparmor|dm-crypt) that contain data critical to the security of the kernel. + Only valid when action is "measure" and func is + CRITICAL_DATA. default policy: # PROC_SUPER_MAGIC @@ -128,3 +130,7 @@ Description: keys added to .builtin_trusted_keys or .ima keyring: measure func=KEY_CHECK keyrings=.builtin_trusted_keys|.ima + + Example of measure rule using CRITICAL_DATA to measure critical data + + measure func=CRITICAL_DATA data_sources=selinux|apparmor|dm-crypt diff --git a/include/linux/ima.h b/include/linux/ima.h index d15100de6cdd..4040f484ac63 100644 --- a/include/linux/ima.h +++ b/include/linux/ima.h @@ -26,6 +26,10 @@ extern int ima_post_read_file(struct file *file, void *buf, loff_t size, 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(int kernel_fd, const void *buf, int size); +extern void ima_measure_critical_data(const char *event_name, + const char *event_data_source, + const void *buf, int buf_len, + bool measure_buf_hash); #ifdef CONFIG_IMA_KEXEC extern void ima_add_kexec_buffer(struct kimage *image); @@ -104,6 +108,10 @@ static inline int ima_file_hash(struct file *file, char *buf, size_t buf_size) } static inline void ima_kexec_cmdline(int kernel_fd, const void *buf, int size) {} +static inline void ima_measure_critical_data(const char *event_name, + const char *event_data_source, + const void *buf, int buf_len, + bool measure_buf_hash) {} #endif /* CONFIG_IMA */ #ifndef CONFIG_IMA_KEXEC diff --git a/security/integrity/ima/ima.h b/security/integrity/ima/ima.h index 0f77e0b697a3..c1acf88e1b5d 100644 --- a/security/integrity/ima/ima.h +++ b/security/integrity/ima/ima.h @@ -200,6 +200,7 @@ static inline unsigned int ima_hash_key(u8 *digest) hook(POLICY_CHECK, policy) \ hook(KEXEC_CMDLINE, kexec_cmdline) \ hook(KEY_CHECK, key) \ + hook(CRITICAL_DATA, critical_data) \ hook(MAX_CHECK, none) #define __ima_hook_enumify(ENUM, str) ENUM, diff --git a/security/integrity/ima/ima_api.c b/security/integrity/ima/ima_api.c index af218babd198..9917e1730cb6 100644 --- a/security/integrity/ima/ima_api.c +++ b/security/integrity/ima/ima_api.c @@ -176,7 +176,7 @@ void ima_add_violation(struct file *file, const unsigned char *filename, * subj=, obj=, type=, func=, mask=, fsmagic= * subj,obj, and type: are LSM specific. * func: FILE_CHECK | BPRM_CHECK | CREDS_CHECK | MMAP_CHECK | MODULE_CHECK - * | KEXEC_CMDLINE | KEY_CHECK + * | KEXEC_CMDLINE | KEY_CHECK | CRITICAL_DATA * mask: contains the permission mask * fsmagic: hex value * diff --git a/security/integrity/ima/ima_main.c b/security/integrity/ima/ima_main.c index 6888fc372abf..d55896f28790 100644 --- a/security/integrity/ima/ima_main.c +++ b/security/integrity/ima/ima_main.c @@ -867,6 +867,32 @@ void ima_kexec_cmdline(int kernel_fd, const void *buf, int size) fdput(f); } +/** + * ima_measure_critical_data - measure critical data + * @event_name: name for the given data + * @event_data_source: name of the event data source + * @buf: pointer to buffer containing data to measure + * @buf_len: length of buffer(in bytes) + * @measure_buf_hash: if set to true - will measure hash of the buf, + * instead of buf + * + * Buffers can only be measured, not appraised. + */ +void ima_measure_critical_data(const char *event_name, + const char *event_data_source, + const void *buf, int buf_len, + bool measure_buf_hash) +{ + if (!event_name || !event_data_source || !buf || !buf_len) { + pr_err("Invalid arguments passed to %s().\n", __func__); + return; + } + + process_buffer_measurement(NULL, buf, buf_len, event_name, + CRITICAL_DATA, 0, event_data_source, + measure_buf_hash); +} + static int __init init_ima(void) { int error; diff --git a/security/integrity/ima/ima_policy.c b/security/integrity/ima/ima_policy.c index 89452245f54a..491017df7589 100644 --- a/security/integrity/ima/ima_policy.c +++ b/security/integrity/ima/ima_policy.c @@ -510,14 +510,23 @@ static bool ima_match_rules(struct ima_rule_entry *rule, struct inode *inode, { int i; - if (func == KEY_CHECK) { - return (rule->flags & IMA_FUNC) && (rule->func == func) && - ima_match_rule_data(rule, rule->keyrings, func_data, - true, cred); - } if ((rule->flags & IMA_FUNC) && (rule->func != func && func != POST_SETATTR)) return false; + + switch (func) { + case KEY_CHECK: + return ((rule->func == func) && + ima_match_rule_data(rule, rule->keyrings, + func_data, true, cred)); + case CRITICAL_DATA: + return ((rule->func == func) && + ima_match_rule_data(rule, rule->data_sources, + func_data, false, cred)); + default: + break; + } + if ((rule->flags & IMA_MASK) && (rule->mask != mask && func != POST_SETATTR)) return false; @@ -1113,6 +1122,19 @@ static bool ima_validate_rule(struct ima_rule_entry *entry) if (ima_rule_contains_lsm_cond(entry)) return false; + break; + case CRITICAL_DATA: + if (entry->action & ~(MEASURE | DONT_MEASURE)) + return false; + + if (!(entry->flags & IMA_DATA_SOURCES) || + (entry->flags & ~(IMA_FUNC | IMA_UID | IMA_PCR | + IMA_DATA_SOURCES))) + return false; + + if (ima_rule_contains_lsm_cond(entry)) + return false; + break; default: return false; @@ -1245,6 +1267,8 @@ static int ima_parse_rule(char *rule, struct ima_rule_entry *entry) else if (IS_ENABLED(CONFIG_IMA_MEASURE_ASYMMETRIC_KEYS) && strcmp(args[0].from, "KEY_CHECK") == 0) entry->func = KEY_CHECK; + else if (strcmp(args[0].from, "CRITICAL_DATA") == 0) + entry->func = CRITICAL_DATA; else result = -EINVAL; if (!result)