IMA: support for per policy rule template formats

Admins may wish to log different measurements using different IMA
templates. Add support for overriding the default template on a per-rule
basis.

Inspired-by: Roberto Sassu <[e-mail]>
Signed-off-by: Matthew Garrett <[e-mail]>
Signed-off-by: Mimi Zohar <[e-mail]>

Documentation/ABI/testing/ima_policy

···
 				[euid=] [fowner=] [fsname=]]
 			lsm:	[[subj_user=] [subj_role=] [subj_type=]
 				 [obj_user=] [obj_role=] [obj_type=]]
-			option:	[[appraise_type=]] [permit_directio]
-
+			option:	[[appraise_type=]] [template=] [permit_directio]
 		base: 	func:= [BPRM_CHECK][MMAP_CHECK][CREDS_CHECK][FILE_CHECK][MODULE_CHECK]
 				[FIRMWARE_CHECK]
 				[KEXEC_KERNEL_CHECK] [KEXEC_INITRAMFS_CHECK]
···
 			fowner:= decimal value
 		lsm:  	are LSM specific
 		option:	appraise_type:= [imasig]
+			template:= name of a defined IMA template type
+			(eg, ima-ng). Only valid when action is "measure".
 			pcr:= decimal value
 
 		default policy:

security/integrity/ima/ima.h

···
 int ima_init_crypto(void);
 void ima_putc(struct seq_file *m, void *data, int datalen);
 void ima_print_digest(struct seq_file *m, u8 *digest, u32 size);
+int template_desc_init_fields(const char *template_fmt,
+			      const struct ima_template_field ***fields,
+			      int *num_fields);
 struct ima_template_desc *ima_template_desc_current(void);
+struct ima_template_desc *lookup_template_desc(const char *name);
 int ima_restore_measurement_entry(struct ima_template_entry *entry);
 int ima_restore_measurement_list(loff_t bufsize, void *buf);
 int ima_measurements_show(struct seq_file *m, void *v);
···
 
 /* LIM API function definitions */
 int ima_get_action(struct inode *inode, const struct cred *cred, u32 secid,
-		   int mask, enum ima_hooks func, int *pcr);
+		   int mask, enum ima_hooks func, int *pcr,
+		   struct ima_template_desc **template_desc);
 int ima_must_measure(struct inode *inode, int mask, enum ima_hooks func);
 int ima_collect_measurement(struct integrity_iint_cache *iint,
 			    struct file *file, void *buf, loff_t size,
···
 void ima_store_measurement(struct integrity_iint_cache *iint, struct file *file,
 			   const unsigned char *filename,
 			   struct evm_ima_xattr_data *xattr_value,
-			   int xattr_len, int pcr);
+			   int xattr_len, int pcr,
+			   struct ima_template_desc *template_desc);
 void ima_audit_measurement(struct integrity_iint_cache *iint,
 			   const unsigned char *filename);
 int ima_alloc_init_template(struct ima_event_data *event_data,
-			    struct ima_template_entry **entry);
+			    struct ima_template_entry **entry,
+			    struct ima_template_desc *template_desc);
 int ima_store_template(struct ima_template_entry *entry, int violation,
 		       struct inode *inode,
 		       const unsigned char *filename, int pcr);
···
 
 /* IMA policy related functions */
 int ima_match_policy(struct inode *inode, const struct cred *cred, u32 secid,
-		     enum ima_hooks func, int mask, int flags, int *pcr);
+		     enum ima_hooks func, int mask, int flags, int *pcr,
+		     struct ima_template_desc **template_desc);
 void ima_init_policy(void);
 void ima_update_policy(void);
 void ima_update_policy_flag(void);

security/integrity/ima/ima_api.c

···
  * ima_alloc_init_template - create and initialize a new template entry
  */
 int ima_alloc_init_template(struct ima_event_data *event_data,
-			    struct ima_template_entry **entry)
+			    struct ima_template_entry **entry,
+			    struct ima_template_desc *desc)
 {
-	struct ima_template_desc *template_desc = ima_template_desc_current();
+	struct ima_template_desc *template_desc;
 	int i, result = 0;
+
+	if (desc)
+		template_desc = desc;
+	else
+		template_desc = ima_template_desc_current();
 
 	*entry = kzalloc(sizeof(**entry) + template_desc->num_fields *
 			 sizeof(struct ima_field_data), GFP_NOFS);
···
 	/* can overflow, only indicator */
 	atomic_long_inc(&ima_htable.violations);
 
-	result = ima_alloc_init_template(&event_data, &entry);
+	result = ima_alloc_init_template(&event_data, &entry, NULL);
 	if (result < 0) {
 		result = -ENOMEM;
 		goto err_out;
···
  *        MAY_APPEND)
  * @func: caller identifier
  * @pcr: pointer filled in if matched measure policy sets pcr=
+ * @template_desc: pointer filled in if matched measure policy sets template=
  *
  * The policy is defined in terms of keypairs:
  *		subj=, obj=, type=, func=, mask=, fsmagic=
···
  *
  */
 int ima_get_action(struct inode *inode, const struct cred *cred, u32 secid,
-		   int mask, enum ima_hooks func, int *pcr)
+		   int mask, enum ima_hooks func, int *pcr,
+		   struct ima_template_desc **template_desc)
 {
 	int flags = IMA_MEASURE | IMA_AUDIT | IMA_APPRAISE | IMA_HASH;
 
 	flags &= ima_policy_flag;
 
-	return ima_match_policy(inode, cred, secid, func, mask, flags, pcr);
+	return ima_match_policy(inode, cred, secid, func, mask, flags, pcr,
+				template_desc);
 }
 
 /*
···
 void ima_store_measurement(struct integrity_iint_cache *iint,
 			   struct file *file, const unsigned char *filename,
 			   struct evm_ima_xattr_data *xattr_value,
-			   int xattr_len, int pcr)
+			   int xattr_len, int pcr,
+			   struct ima_template_desc *template_desc)
 {
 	static const char op[] = "add_template_measure";
 	static const char audit_cause[] = "ENOMEM";
···
 	if (iint->measured_pcrs & (0x1 << pcr))
 		return;
 
-	result = ima_alloc_init_template(&event_data, &entry);
+	result = ima_alloc_init_template(&event_data, &entry, template_desc);
 	if (result < 0) {
 		integrity_audit_msg(AUDIT_INTEGRITY_PCR, inode, filename,
 				    op, audit_cause, result, 0);

security/integrity/ima/ima_appraise.c

···
 
 	security_task_getsecid(current, &secid);
 	return ima_match_policy(inode, current_cred(), secid, func, mask,
-				IMA_APPRAISE | IMA_HASH, NULL);
+				IMA_APPRAISE | IMA_HASH, NULL, NULL);
 }
 
 static int ima_fix_xattr(struct dentry *dentry,

security/integrity/ima/ima_init.c

···
 		}
 	}
 
-	result = ima_alloc_init_template(&event_data, &entry);
+	result = ima_alloc_init_template(&event_data, &entry, NULL);
 	if (result < 0) {
 		audit_cause = "alloc_entry";
 		goto err_out;

security/integrity/ima/ima_main.c

···
 {
 	struct inode *inode = file_inode(file);
 	struct integrity_iint_cache *iint = NULL;
-	struct ima_template_desc *template_desc;
+	struct ima_template_desc *template_desc = NULL;
 	char *pathbuf = NULL;
 	char filename[NAME_MAX];
 	const char *pathname = NULL;
···
 	 * bitmask based on the appraise/audit/measurement policy.
 	 * Included is the appraise submask.
 	 */
-	action = ima_get_action(inode, cred, secid, mask, func, &pcr);
+	action = ima_get_action(inode, cred, secid, mask, func, &pcr,
+				&template_desc);
 	violation_check = ((func == FILE_CHECK || func == MMAP_CHECK) &&
 			   (ima_policy_flag & IMA_MEASURE));
 	if (!action && !violation_check)
···
 		goto out_locked;
 	}
 
-	template_desc = ima_template_desc_current();
 	if ((action & IMA_APPRAISE_SUBMASK) ||
 		    strcmp(template_desc->name, IMA_TEMPLATE_IMA_NAME) != 0)
 		/* read 'security.ima' */
···
 
 	if (action & IMA_MEASURE)
 		ima_store_measurement(iint, file, pathname,
-				      xattr_value, xattr_len, pcr);
+				      xattr_value, xattr_len, pcr,
+				      template_desc);
 	if (rc == 0 && (action & IMA_APPRAISE_SUBMASK)) {
 		inode_lock(inode);
 		rc = ima_appraise_measurement(func, iint, file, pathname,

security/integrity/ima/ima_policy.c

···
 		int type;	/* audit type */
 	} lsm[MAX_LSM_RULES];
 	char *fsname;
+	struct ima_template_desc *template;
 };
 
 /*
···
  * @func: IMA hook identifier
  * @mask: requested action (MAY_READ | MAY_WRITE | MAY_APPEND | MAY_EXEC)
  * @pcr: set the pcr to extend
+ * @template_desc: the template that should be used for this rule
  *
  * Measure decision based on func/mask/fsmagic and LSM(subj/obj/type)
  * conditions.
···
  * than writes so ima_match_policy() is classical RCU candidate.
  */
 int ima_match_policy(struct inode *inode, const struct cred *cred, u32 secid,
-		     enum ima_hooks func, int mask, int flags, int *pcr)
+		     enum ima_hooks func, int mask, int flags, int *pcr,
+		     struct ima_template_desc **template_desc)
 {
 	struct ima_rule_entry *entry;
 	int action = 0, actmask = flags | (flags << 1);
···
 
 		if ((pcr) && (entry->flags & IMA_PCR))
 			*pcr = entry->pcr;
+
+		if (template_desc && entry->template)
+			*template_desc = entry->template;
+		else if (template_desc)
+			*template_desc = ima_template_desc_current();
 
 		if (!actmask)
 			break;
···
 	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_err
+	Opt_pcr, Opt_template, Opt_err
 };
 
 static const match_table_t policy_tokens = {
···
 	{Opt_appraise_type, "appraise_type=%s"},
 	{Opt_permit_directio, "permit_directio"},
 	{Opt_pcr, "pcr=%s"},
+	{Opt_template, "template=%s"},
 	{Opt_err, NULL}
 };
 
···
 	char *from;
 	char *p;
 	bool uid_token;
+	struct ima_template_desc *template_desc;
 	int result = 0;
 
 	ab = integrity_audit_log_start(audit_context(), GFP_KERNEL,
···
 				entry->flags |= IMA_PCR;
 
 			break;
+		case Opt_template:
+			ima_log_string(ab, "template", args[0].from);
+			if (entry->action != MEASURE) {
+				result = -EINVAL;
+				break;
+			}
+			template_desc = lookup_template_desc(args[0].from);
+			if (!template_desc || entry->template) {
+				result = -EINVAL;
+				break;
+			}
+
+			/*
+			 * template_desc_init_fields() does nothing if
+			 * the template is already initialised, so
+			 * it's safe to do this unconditionally
+			 */
+			template_desc_init_fields(template_desc->fmt,
+						 &(template_desc->fields),
+						 &(template_desc->num_fields));
+			entry->template = template_desc;
+			break;
 		case Opt_err:
 			ima_log_string(ab, "UNKNOWN", p);
 			result = -EINVAL;
···
 			}
 		}
 	}
+	if (entry->template)
+		seq_printf(m, "template=%s ", entry->template->name);
 	if (entry->flags & IMA_DIGSIG_REQUIRED)
 		seq_puts(m, "appraise_type=imasig ");
 	if (entry->flags & IMA_PERMIT_DIRECTIO)

security/integrity/ima/ima_template.c

···
 #define MAX_TEMPLATE_NAME_LEN 15
 
 static struct ima_template_desc *ima_template;
-static struct ima_template_desc *lookup_template_desc(const char *name);
-static int template_desc_init_fields(const char *template_fmt,
-				     const struct ima_template_field ***fields,
-				     int *num_fields);
 
 static int __init ima_template_setup(char *str)
 {
···
 }
 __setup("ima_template_fmt=", ima_template_fmt_setup);
 
-static struct ima_template_desc *lookup_template_desc(const char *name)
+struct ima_template_desc *lookup_template_desc(const char *name)
 {
 	struct ima_template_desc *template_desc;
 	int found = 0;
···
 	return j + 1;
 }
 
-static int template_desc_init_fields(const char *template_fmt,
-				     const struct ima_template_field ***fields,
-				     int *num_fields)
+int template_desc_init_fields(const char *template_fmt,
+			      const struct ima_template_field ***fields,
+			      int *num_fields)
 {
 	const char *template_fmt_ptr;
 	const struct ima_template_field *found_fields[IMA_TEMPLATE_NUM_FIELDS_MAX];