SELinux: add boundary support and thread context assignment

The purpose of this patch is to assign per-thread security context
under a constraint. It enables multi-threaded server application
to kick a request handler with its fair security context, and
helps some of userspace object managers to handle user's request.

When we assign a per-thread security context, it must not have wider
permissions than the original one. Because a multi-threaded process
shares a single local memory, an arbitary per-thread security context
also means another thread can easily refer violated information.

The constraint on a per-thread security context requires a new domain
has to be equal or weaker than its original one, when it tries to assign
a per-thread security context.

Bounds relationship between two types is a way to ensure a domain can
never have wider permission than its bounds. We can define it in two
explicit or implicit ways.

The first way is using new TYPEBOUNDS statement. It enables to define
a boundary of types explicitly. The other one expand the concept of
existing named based hierarchy. If we defines a type with "." separated
name like "httpd_t.php", toolchain implicitly set its bounds on "httpd_t".

This feature requires a new policy version.
The 24th version (POLICYDB_VERSION_BOUNDARY) enables to ship them into
kernel space, and the following patch enables to handle it.

Signed-off-by: KaiGai Kohei <kaigai@ak.jp.nec.com>
Acked-by:  Stephen Smalley <sds@tycho.nsa.gov>
Signed-off-by: James Morris <jmorris@namei.org>

1 files changed, 191 insertions, 14 deletions

diff --git a/security/selinux/ss/policydb.c b/security/selinux/ss/policydb.c
index 26646305dc0e..72e4a54973aa 100644
--- a/security/selinux/ss/policydb.c
+++ b/security/selinux/ss/policydb.c
@@ -30,6 +30,7 @@
 #include <linux/slab.h>
 #include <linux/string.h>
 #include <linux/errno.h>
+#include <linux/audit.h>
 #include "security.h"
 
 #include "policydb.h"
@@ -116,7 +117,12 @@ static struct policydb_compat_info policydb_compat[] = {
                 .version        = POLICYDB_VERSION_PERMISSIVE,
                 .sym_num        = SYM_NUM,
                 .ocon_num       = OCON_NUM,
-        }
+        },
+        {
+                .version        = POLICYDB_VERSION_BOUNDARY,
+                .sym_num        = SYM_NUM,
+                .ocon_num       = OCON_NUM,
+        },
 };
 
 static struct policydb_compat_info *policydb_lookup_compat(int version)
@@ -254,7 +260,9 @@ static int role_index(void *key, void *datum, void *datap)
 
         role = datum;
         p = datap;
-        if (!role->value || role->value > p->p_roles.nprim)
+        if (!role->value
+            || role->value > p->p_roles.nprim
+            || role->bounds > p->p_roles.nprim)
                 return -EINVAL;
         p->p_role_val_to_name[role->value - 1] = key;
         p->role_val_to_struct[role->value - 1] = role;
@@ -270,9 +278,12 @@ static int type_index(void *key, void *datum, void *datap)
         p = datap;
 
         if (typdatum->primary) {
-                if (!typdatum->value || typdatum->value > p->p_types.nprim)
+                if (!typdatum->value
+                    || typdatum->value > p->p_types.nprim
+                    || typdatum->bounds > p->p_types.nprim)
                         return -EINVAL;
                 p->p_type_val_to_name[typdatum->value - 1] = key;
+                p->type_val_to_struct[typdatum->value - 1] = typdatum;
         }
 
         return 0;
@@ -285,7 +296,9 @@ static int user_index(void *key, void *datum, void *datap)
 
         usrdatum = datum;
         p = datap;
-        if (!usrdatum->value || usrdatum->value > p->p_users.nprim)
+        if (!usrdatum->value
+            || usrdatum->value > p->p_users.nprim
+            || usrdatum->bounds > p->p_users.nprim)
                 return -EINVAL;
         p->p_user_val_to_name[usrdatum->value - 1] = key;
         p->user_val_to_struct[usrdatum->value - 1] = usrdatum;
@@ -438,6 +451,14 @@ static int policydb_index_others(struct policydb *p)
                 goto out;
         }
 
+        p->type_val_to_struct =
+                kmalloc(p->p_types.nprim * sizeof(*(p->type_val_to_struct)),
+                        GFP_KERNEL);
+        if (!p->type_val_to_struct) {
+                rc = -ENOMEM;
+                goto out;
+        }
+
         if (cond_init_bool_indexes(p)) {
                 rc = -ENOMEM;
                 goto out;
@@ -625,6 +646,7 @@ void policydb_destroy(struct policydb *p)
         kfree(p->class_val_to_struct);
         kfree(p->role_val_to_struct);
         kfree(p->user_val_to_struct);
+        kfree(p->type_val_to_struct);
 
         avtab_destroy(&p->te_avtab);
 
@@ -1176,8 +1198,8 @@ static int role_read(struct policydb *p, struct hashtab *h, void *fp)
 {
         char *key = NULL;
         struct role_datum *role;
-        int rc;
-        __le32 buf[2];
+        int rc, to_read = 2;
+        __le32 buf[3];
         u32 len;
 
         role = kzalloc(sizeof(*role), GFP_KERNEL);
@@ -1186,12 +1208,17 @@ static int role_read(struct policydb *p, struct hashtab *h, void *fp)
                 goto out;
         }
 
-        rc = next_entry(buf, fp, sizeof buf);
+        if (p->policyvers >= POLICYDB_VERSION_BOUNDARY)
+                to_read = 3;
+
+        rc = next_entry(buf, fp, sizeof(buf[0]) * to_read);
         if (rc < 0)
                 goto bad;
 
         len = le32_to_cpu(buf[0]);
         role->value = le32_to_cpu(buf[1]);
+        if (p->policyvers >= POLICYDB_VERSION_BOUNDARY)
+                role->bounds = le32_to_cpu(buf[2]);
 
         key = kmalloc(len + 1, GFP_KERNEL);
         if (!key) {
@@ -1236,8 +1263,8 @@ static int type_read(struct policydb *p, struct hashtab *h, void *fp)
 {
         char *key = NULL;
         struct type_datum *typdatum;
-        int rc;
-        __le32 buf[3];
+        int rc, to_read = 3;
+        __le32 buf[4];
         u32 len;
 
         typdatum = kzalloc(sizeof(*typdatum), GFP_KERNEL);
@@ -1246,13 +1273,27 @@ static int type_read(struct policydb *p, struct hashtab *h, void *fp)
                 return rc;
         }
 
-        rc = next_entry(buf, fp, sizeof buf);
+        if (p->policyvers >= POLICYDB_VERSION_BOUNDARY)
+                to_read = 4;
+
+        rc = next_entry(buf, fp, sizeof(buf[0]) * to_read);
         if (rc < 0)
                 goto bad;
 
         len = le32_to_cpu(buf[0]);
         typdatum->value = le32_to_cpu(buf[1]);
-        typdatum->primary = le32_to_cpu(buf[2]);
+        if (p->policyvers >= POLICYDB_VERSION_BOUNDARY) {
+                u32 prop = le32_to_cpu(buf[2]);
+
+                if (prop & TYPEDATUM_PROPERTY_PRIMARY)
+                        typdatum->primary = 1;
+                if (prop & TYPEDATUM_PROPERTY_ATTRIBUTE)
+                        typdatum->attribute = 1;
+
+                typdatum->bounds = le32_to_cpu(buf[3]);
+        } else {
+                typdatum->primary = le32_to_cpu(buf[2]);
+        }
 
         key = kmalloc(len + 1, GFP_KERNEL);
         if (!key) {
@@ -1309,8 +1350,8 @@ static int user_read(struct policydb *p, struct hashtab *h, void *fp)
 {
         char *key = NULL;
         struct user_datum *usrdatum;
-        int rc;
-        __le32 buf[2];
+        int rc, to_read = 2;
+        __le32 buf[3];
         u32 len;
 
         usrdatum = kzalloc(sizeof(*usrdatum), GFP_KERNEL);
@@ -1319,12 +1360,17 @@ static int user_read(struct policydb *p, struct hashtab *h, void *fp)
                 goto out;
         }
 
-        rc = next_entry(buf, fp, sizeof buf);
+        if (p->policyvers >= POLICYDB_VERSION_BOUNDARY)
+                to_read = 3;
+
+        rc = next_entry(buf, fp, sizeof(buf[0]) * to_read);
         if (rc < 0)
                 goto bad;
 
         len = le32_to_cpu(buf[0]);
         usrdatum->value = le32_to_cpu(buf[1]);
+        if (p->policyvers >= POLICYDB_VERSION_BOUNDARY)
+                usrdatum->bounds = le32_to_cpu(buf[2]);
 
         key = kmalloc(len + 1, GFP_KERNEL);
         if (!key) {
@@ -1465,6 +1511,133 @@ static int (*read_f[SYM_NUM]) (struct policydb *p, struct hashtab *h, void *fp)
         cat_read,
 };
 
+static int user_bounds_sanity_check(void *key, void *datum, void *datap)
+{
+        struct user_datum *upper, *user;
+        struct policydb *p = datap;
+        int depth = 0;
+
+        upper = user = datum;
+        while (upper->bounds) {
+                struct ebitmap_node *node;
+                unsigned long bit;
+
+                if (++depth == POLICYDB_BOUNDS_MAXDEPTH) {
+                        printk(KERN_ERR "SELinux: user %s: "
+                               "too deep or looped boundary",
+                               (char *) key);
+                        return -EINVAL;
+                }
+
+                upper = p->user_val_to_struct[upper->bounds - 1];
+                ebitmap_for_each_positive_bit(&user->roles, node, bit) {
+                        if (ebitmap_get_bit(&upper->roles, bit))
+                                continue;
+
+                        printk(KERN_ERR
+                               "SELinux: boundary violated policy: "
+                               "user=%s role=%s bounds=%s\n",
+                               p->p_user_val_to_name[user->value - 1],
+                               p->p_role_val_to_name[bit],
+                               p->p_user_val_to_name[upper->value - 1]);
+
+                        return -EINVAL;
+                }
+        }
+
+        return 0;
+}
+
+static int role_bounds_sanity_check(void *key, void *datum, void *datap)
+{
+        struct role_datum *upper, *role;
+        struct policydb *p = datap;
+        int depth = 0;
+
+        upper = role = datum;
+        while (upper->bounds) {
+                struct ebitmap_node *node;
+                unsigned long bit;
+
+                if (++depth == POLICYDB_BOUNDS_MAXDEPTH) {
+                        printk(KERN_ERR "SELinux: role %s: "
+                               "too deep or looped bounds\n",
+                               (char *) key);
+                        return -EINVAL;
+                }
+
+                upper = p->role_val_to_struct[upper->bounds - 1];
+                ebitmap_for_each_positive_bit(&role->types, node, bit) {
+                        if (ebitmap_get_bit(&upper->types, bit))
+                                continue;
+
+                        printk(KERN_ERR
+                               "SELinux: boundary violated policy: "
+                               "role=%s type=%s bounds=%s\n",
+                               p->p_role_val_to_name[role->value - 1],
+                               p->p_type_val_to_name[bit],
+                               p->p_role_val_to_name[upper->value - 1]);
+
+                        return -EINVAL;
+                }
+        }
+
+        return 0;
+}
+
+static int type_bounds_sanity_check(void *key, void *datum, void *datap)
+{
+        struct type_datum *upper, *type;
+        struct policydb *p = datap;
+        int depth = 0;
+
+        upper = type = datum;
+        while (upper->bounds) {
+                if (++depth == POLICYDB_BOUNDS_MAXDEPTH) {
+                        printk(KERN_ERR "SELinux: type %s: "
+                               "too deep or looped boundary\n",
+                               (char *) key);
+                        return -EINVAL;
+                }
+
+                upper = p->type_val_to_struct[upper->bounds - 1];
+                if (upper->attribute) {
+                        printk(KERN_ERR "SELinux: type %s: "
+                               "bounded by attribute %s",
+                               (char *) key,
+                               p->p_type_val_to_name[upper->value - 1]);
+                        return -EINVAL;
+                }
+        }
+
+        return 0;
+}
+
+static int policydb_bounds_sanity_check(struct policydb *p)
+{
+        int rc;
+
+        if (p->policyvers < POLICYDB_VERSION_BOUNDARY)
+                return 0;
+
+        rc = hashtab_map(p->p_users.table,
+                         user_bounds_sanity_check, p);
+        if (rc)
+                return rc;
+
+        rc = hashtab_map(p->p_roles.table,
+                         role_bounds_sanity_check, p);
+        if (rc)
+                return rc;
+
+        rc = hashtab_map(p->p_types.table,
+                         type_bounds_sanity_check, p);
+        if (rc)
+                return rc;
+
+        return 0;
+}
+
 extern int ss_initialized;
 
 /*
@@ -1961,6 +2134,10 @@ int policydb_read(struct policydb *p, void *fp)
                                 goto bad;
         }
 
+        rc = policydb_bounds_sanity_check(p);
+        if (rc)
+                goto bad;
+
         rc = 0;
 out:
         return rc;