apparmor: add the ability for policy to specify a permission table

Currently permissions are encoded in the dfa accept entries that are
then mapped to an internal permission structure. This limits the
permissions that userspace can specify, so allow userspace to directly
specify the permission table.

Signed-off-by: John Johansen <[e-mail]>

security/apparmor/include/policy.h

···
  */
 struct aa_policydb {
 	struct aa_dfa *dfa;
-	struct aa_perms *perms;
+	struct {
+		struct aa_perms *perms;
+		u32 size;
+	};
 	struct aa_str_table trans;
 	aa_state_t start[AA_CLASS_LAST + 1];
 };

security/apparmor/policy_unpack.c

···
 /**
  * unpack_dfa - unpack a file rule dfa
  * @e: serialized data extent information (NOT NULL)
+ * @flags: dfa flags to check
  *
  * returns dfa or ERR_PTR or NULL if no dfa
  */
-static struct aa_dfa *unpack_dfa(struct aa_ext *e)
+static struct aa_dfa *unpack_dfa(struct aa_ext *e, int flags)
 {
 	char *blob = NULL;
 	size_t size;
···
 		size_t sz = blob - (char *) e->start -
 			((e->pos - e->start) & 7);
 		size_t pad = ALIGN(sz, 8) - sz;
-		int flags = TO_ACCEPT1_FLAG(YYTD_DATA32) |
-			TO_ACCEPT2_FLAG(YYTD_DATA32);
 		if (aa_g_paranoid_load)
 			flags |= DFA_FLAG_VERIFY_STATES;
 		dfa = aa_dfa_unpack(blob + pad, size - pad, flags);
···
 	return false;
 }
 
+static bool unpack_perm(struct aa_ext *e, u32 version, struct aa_perms *perm)
+{
+	bool res;
+
+	if (version != 1)
+		return false;
+
+	res = unpack_u32(e, &perm->allow, NULL);
+	res = res && unpack_u32(e, &perm->allow, NULL);
+	res = res && unpack_u32(e, &perm->deny, NULL);
+	res = res && unpack_u32(e, &perm->subtree, NULL);
+	res = res && unpack_u32(e, &perm->cond, NULL);
+	res = res && unpack_u32(e, &perm->kill, NULL);
+	res = res && unpack_u32(e, &perm->complain, NULL);
+	res = res && unpack_u32(e, &perm->prompt, NULL);
+	res = res && unpack_u32(e, &perm->audit, NULL);
+	res = res && unpack_u32(e, &perm->quiet, NULL);
+	res = res && unpack_u32(e, &perm->hide, NULL);
+	res = res && unpack_u32(e, &perm->xindex, NULL);
+	res = res && unpack_u32(e, &perm->tag, NULL);
+	res = res && unpack_u32(e, &perm->label, NULL);
+
+	return res;
+}
+
+static ssize_t unpack_perms_table(struct aa_ext *e, struct aa_perms **perms)
+{
+	void *pos = e->pos;
+	u16 size = 0;
+
+	AA_BUG(!perms);
+	/*
+	 * policy perms are optional, in which case perms are embedded
+	 * in the dfa accept table
+	 */
+	if (unpack_nameX(e, AA_STRUCT, "perms")) {
+		int i;
+		u32 version;
+
+		if (!unpack_u32(e, &version, "version"))
+			goto fail_reset;
+		if (unpack_array(e, NULL, &size) != TRI_TRUE)
+			goto fail_reset;
+		*perms = kcalloc(size, sizeof(struct aa_perms), GFP_KERNEL);
+		if (!*perms)
+			goto fail_reset;
+		for (i = 0; i < size; i++) {
+			if (!unpack_perm(e, version, &(*perms)[i]))
+				goto fail;
+		}
+		if (!unpack_nameX(e, AA_ARRAYEND, NULL))
+			goto fail;
+		if (!unpack_nameX(e, AA_STRUCTEND, NULL))
+			goto fail;
+	} else
+		*perms = NULL;
+
+	return size;
+
+fail:
+	kfree(*perms);
+fail_reset:
+	e->pos = pos;
+	return -EPROTO;
+}
+
 static int unpack_pdb(struct aa_ext *e, struct aa_policydb *policy,
 		      bool required_dfa, bool required_trans,
 		      const char **info)
 {
-	int i;
+	void *pos = e->pos;
+	int i, flags, error = -EPROTO;
 
-	policy->dfa = unpack_dfa(e);
+	policy->size = unpack_perms_table(e, &policy->perms);
+	if (policy->size < 0) {
+		error = policy->size;
+		policy->perms = NULL;
+		*info = "failed to unpack - perms";
+		goto fail;
+	} else if (policy->perms) {
+		/* perms table present accept is index */
+		flags = TO_ACCEPT1_FLAG(YYTD_DATA32);
+	} else {
+		/* packed perms in accept1 and accept2 */
+		flags = TO_ACCEPT1_FLAG(YYTD_DATA32) |
+			TO_ACCEPT2_FLAG(YYTD_DATA32);
+	}
+
+	policy->dfa = unpack_dfa(e, flags);
 	if (IS_ERR(policy->dfa)) {
-		int error = PTR_ERR(policy->dfa);
-
+		error = PTR_ERR(policy->dfa);
 		policy->dfa = NULL;
 		*info = "failed to unpack - dfa";
-		return error;
+		goto fail;
 	} else if (!policy->dfa) {
 		if (required_dfa) {
 			*info = "missing required dfa";
-			return -EPROTO;
+			goto fail;
 		}
 		goto out;
 	}
···
 	}
 	if (!unpack_trans_table(e, &policy->trans) && required_trans) {
 		*info = "failed to unpack profile transition table";
-		return -EPROTO;
+		goto fail;
 	}
 	/* TODO: move compat mapping here, requires dfa merging first */
 
 out:
 	return 0;
+
+fail:
+	e->pos = pos;
+	return error;
 }
 
 static u32 strhash(const void *data, u32 len, u32 seed)