From patchwork Thu Nov 30 10:56:09 2017 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Roberto Sassu X-Patchwork-Id: 10084603 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 8935E60586 for ; Thu, 30 Nov 2017 11:01:37 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 69A9029F39 for ; Thu, 30 Nov 2017 11:01:37 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id 5E95B29F3B; Thu, 30 Nov 2017 11:01:37 +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=unavailable 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 E287D29F3A for ; Thu, 30 Nov 2017 11:01:36 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751497AbdK3LBg (ORCPT ); Thu, 30 Nov 2017 06:01:36 -0500 Received: from lhrrgout.huawei.com ([194.213.3.17]:61900 "EHLO huawei.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1751177AbdK3LBf (ORCPT ); Thu, 30 Nov 2017 06:01:35 -0500 Received: from LHREML713-CAH.china.huawei.com (unknown [172.18.7.107]) by Forcepoint Email with ESMTP id 41DDEA7F87727; Thu, 30 Nov 2017 11:01:32 +0000 (GMT) Received: from localhost.localdomain (10.204.65.254) by smtpsuk.huawei.com (10.201.108.36) with Microsoft SMTP Server (TLS) id 14.3.361.1; Thu, 30 Nov 2017 11:01:28 +0000 From: Roberto Sassu To: CC: , , Roberto Sassu Subject: [RFC][PATCH v2 8/9] ima: introduce policy action try_appraise Date: Thu, 30 Nov 2017 11:56:09 +0100 Message-ID: <20171130105610.15761-9-roberto.sassu@huawei.com> X-Mailer: git-send-email 2.11.0 In-Reply-To: <20171130105610.15761-1-roberto.sassu@huawei.com> References: <20171130105610.15761-1-roberto.sassu@huawei.com> MIME-Version: 1.0 X-Originating-IP: [10.204.65.254] X-CFilter-Loop: Reflected Sender: owner-linux-security-module@vger.kernel.org Precedence: bulk List-ID: X-Virus-Scanned: ClamAV using ClamSMTP According to the Biba integrity models, TCB processes won't be corrupted by writing non-TCB objects. Introduce the new policy action try_appraise, so that TCB processes are allowed to write files regardless of the appraisal status. security.ima will not be updated. An IMA policy for open() that satisfies the requirements of the Biba integrity models could be: appraise uid=0 mask=^MAY_EXEC (check read up) appraise euid=0 mask=^MAY_EXEC (check read up) appraise uid=0 mask=^MAY_READ (check read up) appraise euid=0 mask=^MAY_READ (check read up) try_appraise uid=0 mask=^MAY_WRITE (update security.ima if possible) try_appraise euid=0 mask=^MAY_WRITE (update security.ima if possible) Signed-off-by: Roberto Sassu --- security/integrity/ima/ima_main.c | 4 +++- security/integrity/ima/ima_policy.c | 16 +++++++++++++--- security/integrity/integrity.h | 1 + 3 files changed, 17 insertions(+), 4 deletions(-) diff --git a/security/integrity/ima/ima_main.c b/security/integrity/ima/ima_main.c index ee9897c8d0cc..0f746b8bd965 100644 --- a/security/integrity/ima/ima_main.c +++ b/security/integrity/ima/ima_main.c @@ -178,6 +178,7 @@ static int process_measurement(struct file *file, const struct cred *cred, char *pathbuf = NULL; char filename[NAME_MAX]; const char *pathname = NULL; + int try_appraise; int rc = -ENOMEM, action, must_appraise; int pcr = CONFIG_IMA_MEASURE_PCR_IDX; struct evm_ima_xattr_data *xattr_value = NULL; @@ -199,6 +200,7 @@ static int process_measurement(struct file *file, const struct cred *cred, return 0; must_appraise = action & IMA_APPRAISE; + try_appraise = action & IMA_TRY_APPRAISE; /* Is the appraise rule hook specific? */ if (action & IMA_FILE_APPRAISE) @@ -286,7 +288,7 @@ static int process_measurement(struct file *file, const struct cred *cred, inode_unlock(inode); if (((rc && must_appraise) || (ima_integrity_model && model_violation)) && - (ima_appraise & IMA_APPRAISE_ENFORCE)) + (ima_appraise & IMA_APPRAISE_ENFORCE) && !try_appraise) return -EACCES; return 0; } diff --git a/security/integrity/ima/ima_policy.c b/security/integrity/ima/ima_policy.c index cd2289daacee..dd8e4c226089 100644 --- a/security/integrity/ima/ima_policy.c +++ b/security/integrity/ima/ima_policy.c @@ -532,7 +532,7 @@ enum { Opt_uid_gt, Opt_euid_gt, Opt_fowner_gt, Opt_uid_lt, Opt_euid_lt, Opt_fowner_lt, Opt_appraise_type, Opt_permit_directio, - Opt_pcr + Opt_pcr, Opt_try_appraise }; static match_table_t policy_tokens = { @@ -563,6 +563,7 @@ static match_table_t policy_tokens = { {Opt_appraise_type, "appraise_type=%s"}, {Opt_permit_directio, "permit_directio"}, {Opt_pcr, "pcr=%s"}, + {Opt_try_appraise, "try_appraise"}, {Opt_err, NULL} }; @@ -652,11 +653,16 @@ static int ima_parse_rule(char *rule, struct ima_rule_entry *entry) break; case Opt_appraise: ima_log_string(ab, "action", "appraise"); + case Opt_try_appraise: + if (token == Opt_try_appraise) + ima_log_string(ab, "action", "try_appraise"); if (entry->action != UNKNOWN) result = -EINVAL; entry->action = APPRAISE; + if (token == Opt_try_appraise) + entry->flags |= IMA_TRY_APPRAISE; break; case Opt_dont_appraise: ima_log_string(ab, "action", "dont_appraise"); @@ -1039,8 +1045,12 @@ int ima_policy_show(struct seq_file *m, void *v) seq_puts(m, pt(Opt_measure)); if (entry->action & DONT_MEASURE) seq_puts(m, pt(Opt_dont_measure)); - if (entry->action & APPRAISE) - seq_puts(m, pt(Opt_appraise)); + if (entry->action & APPRAISE) { + if (entry->flags & IMA_TRY_APPRAISE) + seq_puts(m, pt(Opt_try_appraise)); + else + seq_puts(m, pt(Opt_appraise)); + } if (entry->action & DONT_APPRAISE) seq_puts(m, pt(Opt_dont_appraise)); if (entry->action & AUDIT) diff --git a/security/integrity/integrity.h b/security/integrity/integrity.h index d70fd875d62f..86274385f9f4 100644 --- a/security/integrity/integrity.h +++ b/security/integrity/integrity.h @@ -33,6 +33,7 @@ #define IMA_DIGSIG_REQUIRED 0x02000000 #define IMA_PERMIT_DIRECTIO 0x04000000 #define IMA_NEW_FILE 0x08000000 +#define IMA_TRY_APPRAISE 0x10000000 #define IMA_DO_MASK (IMA_MEASURE | IMA_APPRAISE | IMA_AUDIT | \ IMA_APPRAISE_SUBMASK)