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 <roberto.sassu@huawei.com>
Signed-off-by: Matthew Garrett <mjg59@google.com>
Signed-off-by: Mimi Zohar <zohar@linux.ibm.com>

1 files changed, 36 insertions, 2 deletions

diff --git a/security/integrity/ima/ima_policy.c b/security/integrity/ima/ima_policy.c
index ec4efa8ea366..98c289559079 100644
--- a/security/integrity/ima/ima_policy.c
+++ b/security/integrity/ima/ima_policy.c
@@ -80,6 +80,7 @@ struct ima_rule_entry {
 		int type;	/* audit type */
 	} lsm[MAX_LSM_RULES];
 	char *fsname;
+	struct ima_template_desc *template;
 };
 
 /*
@@ -473,6 +474,7 @@ static int get_subaction(struct ima_rule_entry *rule, enum ima_hooks func)
  * @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.
@@ -482,7 +484,8 @@ static int get_subaction(struct ima_rule_entry *rule, enum ima_hooks func)
  * 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);
@@ -514,6 +517,11 @@ int ima_match_policy(struct inode *inode, const struct cred *cred, u32 secid,
 		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;
 	}
@@ -752,7 +760,7 @@ 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_err
+	Opt_pcr, Opt_template, Opt_err
 };
 
 static const match_table_t policy_tokens = {
@@ -786,6 +794,7 @@ 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}
 };
 
@@ -839,6 +848,7 @@ static int ima_parse_rule(char *rule, struct ima_rule_entry *entry)
 	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,
@@ -1135,6 +1145,28 @@ static int ima_parse_rule(char *rule, struct ima_rule_entry *entry)
 				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;
@@ -1410,6 +1442,8 @@ int ima_policy_show(struct seq_file *m, void *v)
 			}
 		}
 	}
+	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)