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From:   Tyler Hicks <tyhicks@linux.microsoft.com>
To:     Mimi Zohar <zohar@linux.ibm.com>,
        Dmitry Kasatkin <dmitry.kasatkin@gmail.com>
Cc:     James Morris <jmorris@namei.org>,
        "Serge E . Hallyn" <serge@hallyn.com>,
        Lakshmi Ramasubramanian <nramas@linux.microsoft.com>,
        Prakhar Srivastava <prsriva02@gmail.com>,
        linux-kernel@vger.kernel.org, linux-integrity@vger.kernel.org,
        linux-security-module@vger.kernel.org,
        Eric Biederman <ebiederm@xmission.com>,
        kexec@lists.infradead.org
Subject: [PATCH v3 12/12] ima: Support additional conditionals in the KEXEC_CMDLINE hook function
Date:   Thu,  9 Jul 2020 01:19:11 -0500
Message-Id: <20200709061911.954326-13-tyhicks@linux.microsoft.com>
In-Reply-To: <20200709061911.954326-1-tyhicks@linux.microsoft.com>
References: <20200709061911.954326-1-tyhicks@linux.microsoft.com>
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Sender: linux-kernel-owner@vger.kernel.org
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Take the properties of the kexec kernel's inode and the current task
ownership into consideration when matching a KEXEC_CMDLINE operation to
the rules in the IMA policy. This allows for some uniformity when
writing IMA policy rules for KEXEC_KERNEL_CHECK, KEXEC_INITRAMFS_CHECK,
and KEXEC_CMDLINE operations.

Prior to this patch, it was not possible to write a set of rules like
this:

 dont_measure func=KEXEC_KERNEL_CHECK obj_type=foo_t
 dont_measure func=KEXEC_INITRAMFS_CHECK obj_type=foo_t
 dont_measure func=KEXEC_CMDLINE obj_type=foo_t
 measure func=KEXEC_KERNEL_CHECK
 measure func=KEXEC_INITRAMFS_CHECK
 measure func=KEXEC_CMDLINE

The inode information associated with the kernel being loaded by a
kexec_kernel_load(2) syscall can now be included in the decision to
measure or not

Additonally, the uid, euid, and subj_* conditionals can also now be
used in KEXEC_CMDLINE rules. There was no technical reason as to why
those conditionals weren't being considered previously other than
ima_match_rules() didn't have a valid inode to use so it immediately
bailed out for KEXEC_CMDLINE operations rather than going through the
full list of conditional comparisons.

Signed-off-by: Tyler Hicks <tyhicks@linux.microsoft.com>
Cc: Eric Biederman <ebiederm@xmission.com>
Cc: kexec@lists.infradead.org
Reviewed-by: Lakshmi Ramasubramanian <nramas@linux.microsoft.com>
---

* v3
  - Added Lakshmi's Reviewed-by
  - Adjust for the indentation change introduced in patch #4
* v2
  - Moved the inode parameter of process_buffer_measurement() to be the
    first parameter so that it more closely matches process_masurement()

 include/linux/ima.h                          |  4 ++--
 kernel/kexec_file.c                          |  2 +-
 security/integrity/ima/ima.h                 |  2 +-
 security/integrity/ima/ima_api.c             |  2 +-
 security/integrity/ima/ima_appraise.c        |  2 +-
 security/integrity/ima/ima_asymmetric_keys.c |  2 +-
 security/integrity/ima/ima_main.c            | 23 +++++++++++++++-----
 security/integrity/ima/ima_policy.c          | 17 +++++----------
 security/integrity/ima/ima_queue_keys.c      |  2 +-
 9 files changed, 31 insertions(+), 25 deletions(-)

diff --git a/include/linux/ima.h b/include/linux/ima.h
index 9164e1534ec9..d15100de6cdd 100644
--- a/include/linux/ima.h
+++ b/include/linux/ima.h
@@ -25,7 +25,7 @@ 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);
+extern void ima_kexec_cmdline(int kernel_fd, const void *buf, int size);
 
 #ifdef CONFIG_IMA_KEXEC
 extern void ima_add_kexec_buffer(struct kimage *image);
@@ -103,7 +103,7 @@ 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) {}
+static inline void ima_kexec_cmdline(int kernel_fd, const void *buf, int size) {}
 #endif /* CONFIG_IMA */
 
 #ifndef CONFIG_IMA_KEXEC
diff --git a/kernel/kexec_file.c b/kernel/kexec_file.c
index bb05fd52de85..07df431c1f21 100644
--- a/kernel/kexec_file.c
+++ b/kernel/kexec_file.c
@@ -287,7 +287,7 @@ kimage_file_prepare_segments(struct kimage *image, int kernel_fd, int initrd_fd,
 			goto out;
 		}
 
-		ima_kexec_cmdline(image->cmdline_buf,
+		ima_kexec_cmdline(kernel_fd, image->cmdline_buf,
 				  image->cmdline_buf_len - 1);
 	}
 
diff --git a/security/integrity/ima/ima.h b/security/integrity/ima/ima.h
index ea7e77536f3c..576ae2c6d418 100644
--- a/security/integrity/ima/ima.h
+++ b/security/integrity/ima/ima.h
@@ -265,7 +265,7 @@ void ima_store_measurement(struct integrity_iint_cache *iint, struct file *file,
 			   struct evm_ima_xattr_data *xattr_value,
 			   int xattr_len, const struct modsig *modsig, int pcr,
 			   struct ima_template_desc *template_desc);
-void process_buffer_measurement(const void *buf, int size,
+void process_buffer_measurement(struct inode *inode, const void *buf, int size,
 				const char *eventname, enum ima_hooks func,
 				int pcr, const char *keyring);
 void ima_audit_measurement(struct integrity_iint_cache *iint,
diff --git a/security/integrity/ima/ima_api.c b/security/integrity/ima/ima_api.c
index bf22de8b7ce0..4f39fb93f278 100644
--- a/security/integrity/ima/ima_api.c
+++ b/security/integrity/ima/ima_api.c
@@ -162,7 +162,7 @@ void ima_add_violation(struct file *file, const unsigned char *filename,
 
 /**
  * ima_get_action - appraise & measure decision based on policy.
- * @inode: pointer to inode to measure
+ * @inode: pointer to the inode associated with the object being validated
  * @cred: pointer to credentials structure to validate
  * @secid: secid of the task being validated
  * @mask: contains the permission mask (MAY_READ, MAY_WRITE, MAY_EXEC,
diff --git a/security/integrity/ima/ima_appraise.c b/security/integrity/ima/ima_appraise.c
index a9649b04b9f1..6c52bf7ea7f0 100644
--- a/security/integrity/ima/ima_appraise.c
+++ b/security/integrity/ima/ima_appraise.c
@@ -328,7 +328,7 @@ int ima_check_blacklist(struct integrity_iint_cache *iint,
 
 		rc = is_binary_blacklisted(digest, digestsize);
 		if ((rc == -EPERM) && (iint->flags & IMA_MEASURE))
-			process_buffer_measurement(digest, digestsize,
+			process_buffer_measurement(NULL, digest, digestsize,
 						   "blacklisted-hash", NONE,
 						   pcr, NULL);
 	}
diff --git a/security/integrity/ima/ima_asymmetric_keys.c b/security/integrity/ima/ima_asymmetric_keys.c
index aaae80c4e376..1c68c500c26f 100644
--- a/security/integrity/ima/ima_asymmetric_keys.c
+++ b/security/integrity/ima/ima_asymmetric_keys.c
@@ -58,7 +58,7 @@ void ima_post_key_create_or_update(struct key *keyring, struct key *key,
 	 * if the IMA policy is configured to measure a key linked
 	 * to the given keyring.
 	 */
-	process_buffer_measurement(payload, payload_len,
+	process_buffer_measurement(NULL, payload, payload_len,
 				   keyring->description, KEY_CHECK, 0,
 				   keyring->description);
 }
diff --git a/security/integrity/ima/ima_main.c b/security/integrity/ima/ima_main.c
index 8351b2fd48e0..8a91711ca79b 100644
--- a/security/integrity/ima/ima_main.c
+++ b/security/integrity/ima/ima_main.c
@@ -726,6 +726,7 @@ int ima_load_data(enum kernel_load_data_id id)
 
 /*
  * process_buffer_measurement - Measure the buffer to ima log.
+ * @inode: inode associated with the object being measured (NULL for KEY_CHECK)
  * @buf: pointer to the buffer that needs to be added to the log.
  * @size: size of buffer(in bytes).
  * @eventname: event name to be used for the buffer entry.
@@ -735,7 +736,7 @@ int ima_load_data(enum kernel_load_data_id id)
  *
  * Based on policy, the buffer is measured into the ima log.
  */
-void process_buffer_measurement(const void *buf, int size,
+void process_buffer_measurement(struct inode *inode, const void *buf, int size,
 				const char *eventname, enum ima_hooks func,
 				int pcr, const char *keyring)
 {
@@ -768,7 +769,7 @@ void process_buffer_measurement(const void *buf, int size,
 	 */
 	if (func) {
 		security_task_getsecid(current, &secid);
-		action = ima_get_action(NULL, current_cred(), secid, 0, func,
+		action = ima_get_action(inode, current_cred(), secid, 0, func,
 					&pcr, &template, keyring);
 		if (!(action & IMA_MEASURE))
 			return;
@@ -823,16 +824,26 @@ void process_buffer_measurement(const void *buf, int size,
 
 /**
  * ima_kexec_cmdline - measure kexec cmdline boot args
+ * @kernel_fd: file descriptor of the kexec kernel being loaded
  * @buf: pointer to buffer
  * @size: size of buffer
  *
  * Buffers can only be measured, not appraised.
  */
-void ima_kexec_cmdline(const void *buf, int size)
+void ima_kexec_cmdline(int kernel_fd, const void *buf, int size)
 {
-	if (buf && size != 0)
-		process_buffer_measurement(buf, size, "kexec-cmdline",
-					   KEXEC_CMDLINE, 0, NULL);
+	struct fd f;
+
+	if (!buf || !size)
+		return;
+
+	f = fdget(kernel_fd);
+	if (!f.file)
+		return;
+
+	process_buffer_measurement(file_inode(f.file), buf, size,
+				   "kexec-cmdline", KEXEC_CMDLINE, 0, NULL);
+	fdput(f);
 }
 
 static int __init init_ima(void)
diff --git a/security/integrity/ima/ima_policy.c b/security/integrity/ima/ima_policy.c
index 81ee8fd1d83a..2e87154c9296 100644
--- a/security/integrity/ima/ima_policy.c
+++ b/security/integrity/ima/ima_policy.c
@@ -443,13 +443,9 @@ static bool ima_match_rules(struct ima_rule_entry *rule, struct inode *inode,
 {
 	int i;
 
-	if ((func == KEXEC_CMDLINE) || (func == KEY_CHECK)) {
-		if ((rule->flags & IMA_FUNC) && (rule->func == func)) {
-			if (func == KEY_CHECK)
-				return ima_match_keyring(rule, keyring, cred);
-			return true;
-		}
-		return false;
+	if (func == KEY_CHECK) {
+		return (rule->flags & IMA_FUNC) && (rule->func == func) &&
+		       ima_match_keyring(rule, keyring, cred);
 	}
 	if ((rule->flags & IMA_FUNC) &&
 	    (rule->func != func && func != POST_SETATTR))
@@ -1035,10 +1031,9 @@ static bool ima_validate_rule(struct ima_rule_entry *entry)
 		if (entry->action & ~(MEASURE | DONT_MEASURE))
 			return false;
 
-		if (entry->flags & ~(IMA_FUNC | IMA_PCR))
-			return false;
-
-		if (ima_rule_contains_lsm_cond(entry))
+		if (entry->flags & ~(IMA_FUNC | IMA_FSMAGIC | IMA_UID |
+				     IMA_FOWNER | IMA_FSUUID | IMA_EUID |
+				     IMA_PCR | IMA_FSNAME))
 			return false;
 
 		break;
diff --git a/security/integrity/ima/ima_queue_keys.c b/security/integrity/ima/ima_queue_keys.c
index 56ce24a18b66..69a8626a35c0 100644
--- a/security/integrity/ima/ima_queue_keys.c
+++ b/security/integrity/ima/ima_queue_keys.c
@@ -158,7 +158,7 @@ void ima_process_queued_keys(void)
 
 	list_for_each_entry_safe(entry, tmp, &ima_keys, list) {
 		if (!timer_expired)
-			process_buffer_measurement(entry->payload,
+			process_buffer_measurement(NULL, entry->payload,
 						   entry->payload_len,
 						   entry->keyring_name,
 						   KEY_CHECK, 0,
-- 
2.25.1