[TOMOYO #6 retry 16/21] Signal control functions.

[Kentaro Takeda]

TOMOYO Linux checks sending signal by signal number and
the domain of target process. In order to check signal
permission, modification against kernel/signal.c is needed.

Each permission can be automatically accumulated into
the policy of each domain using 'learning mode'.

Signed-off-by: Kentaro Takeda <takedakn@xxxxxxxxxxxxx>
Signed-off-by: Tetsuo Handa <penguin-kernel@xxxxxxxxxxxxxxxxxxx>
---
 security/tomoyo/signal.c |  226 +++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 226 insertions(+)

--- /dev/null
+++ linux-2.6-mm/security/tomoyo/signal.c
@@ -0,0 +1,226 @@
+/*
+ * security/tomoyo/signal.c
+ *
+ * Signal access contol functions for TOMOYO Linux.
+ */
+
+#include "tomoyo.h"
+#include "realpath.h"
+
+/*************************  AUDIT FUNCTIONS  *************************/
+
+static int tmy_audit_signal_log(const int signal,
+				const struct path_info *dest_domain,
+				const bool is_granted,
+				const u8 profile,
+				const unsigned int mode)
+{
+	char *buf;
+	int len;
+
+	if (is_granted) {
+		if (!tmy_audit_grant())
+			return 0;
+	} else {
+		if (!tmy_audit_reject())
+			return 0;
+	}
+
+	len = dest_domain->total_len;
+	buf = tmy_init_audit_log(&len, profile, mode);
+
+	if (!buf)
+		return -ENOMEM;
+
+	tmy_sncatprintf(buf, len - 1, "%s%d %s\n",
+			TMY_ALLOW_SIGNAL, signal, dest_domain->name);
+
+	return tmy_write_audit_log(buf, is_granted);
+}
+
+/*************************  SIGNAL ACL HANDLER  *************************/
+
+static int tmy_add_signal_entry(const u16 sig, const char *dest_pattern,
+				struct domain_info *domain,
+				const struct condition_list *cond,
+				const bool is_delete)
+{
+	struct acl_info *ptr;
+	struct signal_acl *acl;
+	const struct path_info *saved_dest_pattern;
+	int error = -ENOMEM;
+
+	if (!domain)
+		return -EINVAL;
+	if (!dest_pattern ||
+	    !tmy_is_correct_domain(dest_pattern, __FUNCTION__))
+		return -EINVAL;
+
+	saved_dest_pattern = tmy_save_name(dest_pattern);
+	if (!saved_dest_pattern)
+		return -ENOMEM;
+
+	mutex_lock(&domain_acl_lock);
+
+	if (is_delete)
+		goto remove;
+
+	list_for_each_entry(ptr, &domain->acl_info_list, list) {
+		acl = container_of(ptr, struct signal_acl, head);
+
+		if (ptr->type == TMY_TYPE_SIGNAL_ACL && acl->sig == sig
+		    && ptr->cond == cond
+		    && !tmy_pathcmp(acl->domainname, saved_dest_pattern)) {
+			ptr->is_deleted = 0;
+			/* Found. Nothing to do. */
+			error = 0;
+			goto ok;
+		}
+	}
+	/* Not found. Append it to the tail. */
+	acl = tmy_alloc_element(sizeof(*acl));
+	if (!acl)
+		goto ok;
+
+	acl->head.type = TMY_TYPE_SIGNAL_ACL;
+	acl->head.cond = cond;
+	acl->sig = sig;
+	acl->domainname = saved_dest_pattern;
+	error = tmy_add_acl(domain, &acl->head);
+	goto ok;
+remove: ;
+	error = -ENOENT;
+	list_for_each_entry(ptr, &domain->acl_info_list, list) {
+		acl = container_of(ptr, struct signal_acl, head);
+		if (ptr->type != TMY_TYPE_SIGNAL_ACL || ptr->cond != cond ||
+		    ptr->is_deleted || acl->sig != sig ||
+		    tmy_pathcmp(acl->domainname, saved_dest_pattern))
+			continue;
+		error = tmy_del_acl(ptr);
+		break;
+	}
+
+ok: ;
+	mutex_unlock(&domain_acl_lock);
+
+	return error;
+}
+
+/**
+ * tmy_signal_acl - check permission for kill(2)/tkill(2)/tgkill(2).
+ * @sig:  signal number.
+ * @pid:  pid of destination process.
+ *
+ * Returns zero if permission granted.
+ * Returns nonzero if permission denied.
+ */
+int tmy_signal_acl(const int sig, const int pid)
+{
+	struct domain_info *domain = TMY_SECURITY->domain;
+	struct domain_info *dest = NULL;
+	const char *dest_pattern;
+	struct acl_info *ptr;
+	const u16 hash = sig;
+	const u8 profile = domain->profile;
+	const unsigned int mode = tmy_flags(TMY_MAC_FOR_SIGNAL);
+	const bool is_enforce = (mode == 3);
+	bool found = 0;
+
+	if (!mode)
+		return 0;
+	if (!sig)
+		return 0; /* No check for NULL signal. */
+	if (current->pid == pid) {
+		tmy_audit_signal_log(sig, domain->domainname, 1, profile, mode);
+		return 0; /* No check for self. */
+	}
+
+	{ /* Simplified checking. */
+		struct task_struct *p = NULL;
+		read_lock(&tasklist_lock);
+		if (pid > 0)
+			p = find_task_by_pid((pid_t) pid);
+		else if (pid == 0)
+			p = current;
+		else if (pid == -1)
+			dest = &KERNEL_DOMAIN;
+		else
+			p = find_task_by_pid((pid_t) -pid);
+		if (p)
+			/* "struct task_struct"->security is not NULL. */
+			dest = ((struct tmy_security *) p->security)->domain;
+		read_unlock(&tasklist_lock);
+		if (!dest)
+			return 0; /* I can't find destinatioin. */
+	}
+
+	if (domain == dest) {
+		tmy_audit_signal_log(sig, dest->domainname, 1, profile, mode);
+		return 0;
+	}
+
+	dest_pattern = dest->domainname->name;
+	list_for_each_entry(ptr, &domain->acl_info_list, list) {
+		struct signal_acl *acl;
+		acl = container_of(ptr, struct signal_acl, head);
+
+		if (ptr->type == TMY_TYPE_SIGNAL_ACL && ptr->is_deleted == 0
+		    && acl->sig == hash &&
+		    tmy_check_condition(ptr->cond, NULL) == 0) {
+			const int len = acl->domainname->total_len;
+
+			if (strncmp(acl->domainname->name,
+				    dest_pattern, len) == 0
+			    && (dest_pattern[len] == ' ' ||
+				dest_pattern[len] == '\0')) {
+				found = 1;
+				break;
+			}
+		}
+	}
+
+	tmy_audit_signal_log(sig, dest->domainname, found, profile, mode);
+
+	if (found)
+		return 0;
+
+	if (tmy_flags(TMY_VERBOSE))
+		tmy_audit("TOMOYO-%s: Signal %d to %s denied for %s\n",
+			  tmy_getmsg(is_enforce), sig,
+			  tmy_lastname(dest), tmy_lastname(domain));
+
+	if (is_enforce)
+		return tmy_supervisor("%s\n" TMY_ALLOW_SIGNAL "%d %s\n",
+				      domain->domainname->name,
+				      sig, dest_pattern);
+	if (mode == 1 && tmy_quota())
+		tmy_add_signal_entry(sig, dest_pattern, domain, NULL, 0);
+
+	return 0;
+}
+
+/**
+ * tmy_add_signal_policy - add or delete signal policy.
+ * @data:      a line to parse.
+ * @domain:    pointer to "struct domain_info".
+ * @cond:      pointer to "struct condition_list". May be NULL.
+ * @is_delete: is this delete request?
+ *
+ * Returns zero on success.
+ * Returns nonzero on failure.
+ */
+int tmy_add_signal_policy(char *data,
+			  struct domain_info *domain,
+			  const struct condition_list *cond,
+			  const bool is_delete)
+{
+	int sig;
+	char *domainname = strchr(data, ' ');
+
+	if (sscanf(data, "%d", &sig) == 1 && domainname &&
+	    tmy_is_domain_def(domainname + 1))
+		return tmy_add_signal_entry(sig, domainname + 1, domain,
+					    cond, is_delete);
+
+	return -EINVAL;
+}

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