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Hallyn" , Lakshmi Ramasubramanian , Prakhar Srivastava , linux-kernel@vger.kernel.org, linux-integrity@vger.kernel.org, linux-security-module@vger.kernel.org Subject: [PATCH v3 04/12] ima: Fail rule parsing when buffer hook functions have an invalid action Date: Thu, 9 Jul 2020 01:19:03 -0500 Message-Id: <20200709061911.954326-5-tyhicks@linux.microsoft.com> X-Mailer: git-send-email 2.25.1 In-Reply-To: <20200709061911.954326-1-tyhicks@linux.microsoft.com> References: <20200709061911.954326-1-tyhicks@linux.microsoft.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Buffer based hook functions, such as KEXEC_CMDLINE and KEY_CHECK, can only measure. The process_buffer_measurement() function quietly ignores all actions except measure so make this behavior clear at the time of policy load. The parsing of the keyrings conditional had a check to ensure that it was only specified with measure actions but the check should be on the hook function and not the keyrings conditional since "appraise func=KEY_CHECK" is not a valid rule. Fixes: b0935123a183 ("IMA: Define a new hook to measure the kexec boot command line arguments") Fixes: 5808611cccb2 ("IMA: Add KEY_CHECK func to measure keys") Signed-off-by: Tyler Hicks --- * v3 - Add comments to ima_validate_rule() to separate/explain the types of validation checks (section for action checks, section for hook function checks, soon to be a section for combination of options checks, etc.) - Removed the "if (entry->flags & IMA_FUNC)" conditional around the switch statement in ima_validate_rule() which reduced the overall indention by a tab. This could be removed because entry->func is NONE when the IMA_FUNC flag is not set. We'll explicitly enforce and then leverage that property in a later patch when we start validating all hook functions in ima_validate_rule(). - Add comment explicitly stating that all hook functions except KEXEC_CMDLINE and KEY_CHECK are still being validated in ima_parse_rule(). * v2 - No change security/integrity/ima/ima_policy.c | 40 +++++++++++++++++++++++++++-- 1 file changed, 38 insertions(+), 2 deletions(-) diff --git a/security/integrity/ima/ima_policy.c b/security/integrity/ima/ima_policy.c index e458cd47c099..40c28f1a6a5a 100644 --- a/security/integrity/ima/ima_policy.c +++ b/security/integrity/ima/ima_policy.c @@ -973,6 +973,43 @@ static void check_template_modsig(const struct ima_template_desc *template) #undef MSG } +static bool ima_validate_rule(struct ima_rule_entry *entry) +{ + /* Ensure that the action is set */ + if (entry->action == UNKNOWN) + return false; + + /* + * Ensure that the hook function is compatible with the other + * components of the rule + */ + switch (entry->func) { + case NONE: + case FILE_CHECK: + case MMAP_CHECK: + case BPRM_CHECK: + case CREDS_CHECK: + case POST_SETATTR: + case MODULE_CHECK: + case FIRMWARE_CHECK: + case KEXEC_KERNEL_CHECK: + case KEXEC_INITRAMFS_CHECK: + case POLICY_CHECK: + /* Validation of these hook functions is in ima_parse_rule() */ + break; + case KEXEC_CMDLINE: + case KEY_CHECK: + if (entry->action & ~(MEASURE | DONT_MEASURE)) + return false; + + break; + default: + return false; + } + + return true; +} + static int ima_parse_rule(char *rule, struct ima_rule_entry *entry) { struct audit_buffer *ab; @@ -1150,7 +1187,6 @@ static int ima_parse_rule(char *rule, struct ima_rule_entry *entry) keyrings_len = strlen(args[0].from) + 1; if ((entry->keyrings) || - (entry->action != MEASURE) || (entry->func != KEY_CHECK) || (keyrings_len < 2)) { result = -EINVAL; @@ -1356,7 +1392,7 @@ static int ima_parse_rule(char *rule, struct ima_rule_entry *entry) break; } } - if (!result && (entry->action == UNKNOWN)) + if (!result && !ima_validate_rule(entry)) result = -EINVAL; else if (entry->action == APPRAISE) temp_ima_appraise |= ima_appraise_flag(entry->func); -- 2.25.1