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[PATCH v5 10/39] richacl: Permission check algorithm

From Andreas Gruenbacher <andreas.gruenbacher@gmail.com>
Newsgroups linux.kernel
Subject [PATCH v5 10/39] richacl: Permission check algorithm
Date 2015-07-22 15:10 +0200
Message-ID <pP1Wy-7Id-29@gated-at.bofh.it> (permalink)
References <pP1Wx-7Id-5@gated-at.bofh.it>
Organization linux.* mail to news gateway

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From: Andreas Gruenbacher <agruenba@redhat.com>

A richacl roughly grants a requested access if the NFSv4 acl in the richacl
grants the requested permissions according to the NFSv4 permission check
algorithm and the file mask that applies to the process includes the requested
permissions.

Signed-off-by: Andreas Gruenbacher <agruenba@redhat.com>
---
 fs/Makefile             |   2 +-
 fs/richacl_inode.c      | 120 ++++++++++++++++++++++++++++++++++++++++++++++++
 include/linux/richacl.h |   3 ++
 3 files changed, 124 insertions(+), 1 deletion(-)
 create mode 100644 fs/richacl_inode.c

diff --git a/fs/Makefile b/fs/Makefile
index ddc43d8..1305047 100644
--- a/fs/Makefile
+++ b/fs/Makefile
@@ -48,7 +48,7 @@ obj-$(CONFIG_SYSCTL)		+= drop_caches.o
 
 obj-$(CONFIG_FHANDLE)		+= fhandle.o
 obj-$(CONFIG_FS_RICHACL)	+= richacl.o
-richacl-y			:= richacl_base.o
+richacl-y			:= richacl_base.o richacl_inode.o
 
 obj-y				+= quota/
 
diff --git a/fs/richacl_inode.c b/fs/richacl_inode.c
new file mode 100644
index 0000000..63f3b87
--- /dev/null
+++ b/fs/richacl_inode.c
@@ -0,0 +1,120 @@
+/*
+ * Copyright (C) 2010  Novell, Inc.
+ * Copyright (C) 2015  Red Hat, Inc.
+ * Written by Andreas Gruenbacher <agruen@kernel.org>
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License as published by the
+ * Free Software Foundation; either version 2, or (at your option) any
+ * later version.
+ *
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * General Public License for more details.
+ */
+
+#include <linux/sched.h>
+#include <linux/module.h>
+#include <linux/fs.h>
+#include <linux/slab.h>
+#include <linux/richacl.h>
+
+/**
+ * richacl_permission  -  richacl permission check algorithm
+ * @inode:	inode to check
+ * @acl:	rich acl of the inode
+ * @want:	requested access (MAY_* flags)
+ *
+ * Checks if the current process is granted @mask flags in @acl.
+ */
+int
+richacl_permission(struct inode *inode, const struct richacl *acl,
+		   int want)
+{
+	const struct richace *ace;
+	unsigned int mask = richacl_want_to_mask(want);
+	unsigned int requested = mask, denied = 0;
+	int in_owning_group = in_group_p(inode->i_gid);
+	int in_owner_or_group_class = in_owning_group;
+
+	/*
+	 * A process is
+	 *   - in the owner file class if it owns the file,
+	 *   - in the group file class if it is in the file's owning group or
+	 *     it matches any of the user or group entries, and
+	 *   - in the other file class otherwise.
+	 * The file class is only relevant for determining which file mask to
+	 * apply, which only happens for masked acls.
+	 */
+	if (acl->a_flags & RICHACL_MASKED) {
+		if (uid_eq(current_fsuid(), inode->i_uid)) {
+			denied = requested & ~acl->a_owner_mask;
+			goto out;
+		}
+	} else {
+		/*
+		 * We don't care which class the process is in when the acl is
+		 * not masked.
+		 */
+		in_owner_or_group_class = 1;
+	}
+
+	/*
+	 * Check if the acl grants the requested access and determine which
+	 * file class the process is in.
+	 */
+	richacl_for_each_entry(ace, acl) {
+		unsigned int ace_mask = ace->e_mask;
+
+		if (richace_is_inherit_only(ace))
+			continue;
+		if (richace_is_owner(ace)) {
+			if (!uid_eq(current_fsuid(), inode->i_uid))
+				continue;
+		} else if (richace_is_group(ace)) {
+			if (!in_owning_group)
+				continue;
+		} else if (richace_is_unix_user(ace)) {
+			if (!uid_eq(current_fsuid(), ace->e_id.uid))
+				continue;
+		} else if (richace_is_unix_group(ace)) {
+			if (!in_group_p(ace->e_id.gid))
+				continue;
+		} else
+			goto entry_matches_everyone;
+
+		/* The process is in the owner or group file class. */
+		in_owner_or_group_class = 1;
+
+entry_matches_everyone:
+		/* Check which mask flags the ACE allows or denies. */
+		if (richace_is_deny(ace))
+			denied |= ace_mask & mask;
+		mask &= ~ace_mask;
+
+		/*
+		 * Keep going until we know which file class
+		 * the process is in.
+		 */
+		if (!mask && in_owner_or_group_class)
+			break;
+	}
+	denied |= mask;
+
+	if (acl->a_flags & RICHACL_MASKED) {
+		/*
+		 * The file class a process is in determines which file mask
+		 * applies.  Check if that file mask also grants the requested
+		 * access.
+		 */
+		if (in_owner_or_group_class)
+			denied |= requested & ~acl->a_group_mask;
+		else
+			denied = requested & ~acl->a_other_mask;
+	}
+
+out:
+	return denied ? -EACCES : 0;
+}
+EXPORT_SYMBOL_GPL(richacl_permission);
diff --git a/include/linux/richacl.h b/include/linux/richacl.h
index e4266dd..1500824 100644
--- a/include/linux/richacl.h
+++ b/include/linux/richacl.h
@@ -304,4 +304,7 @@ extern unsigned int richacl_want_to_mask(unsigned int);
 extern void richacl_compute_max_masks(struct richacl *, kuid_t);
 extern struct richacl *richacl_chmod(struct richacl *, mode_t);
 
+/* richacl_inode.c */
+extern int richacl_permission(struct inode *, const struct richacl *, int);
+
 #endif /* __RICHACL_H */
-- 
2.4.3

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[PATCH v5 00/39] Richacls Andreas Gruenbacher <andreas.gruenbacher@gmail.com> - 2015-07-22 15:10 +0200
  [PATCH v5 34/39] sunrpc: Allow to demand-allocate pages to encode into Andreas Gruenbacher <andreas.gruenbacher@gmail.com> - 2015-07-22 15:10 +0200
  [PATCH v5 10/39] richacl: Permission check algorithm Andreas Gruenbacher <andreas.gruenbacher@gmail.com> - 2015-07-22 15:10 +0200
  [PATCH v5 28/39] nfsd: Keep list of acls to dispose of in compoundargs Andreas Gruenbacher <andreas.gruenbacher@gmail.com> - 2015-07-22 15:10 +0200
  [PATCH v5 30/39] nfsd: Add richacl support Andreas Gruenbacher <andreas.gruenbacher@gmail.com> - 2015-07-22 15:10 +0200
  [PATCH v5 35/39] sunrpc: Add xdr_init_encode_pages Andreas Gruenbacher <andreas.gruenbacher@gmail.com> - 2015-07-22 15:10 +0200
  [PATCH v5 14/39] richacl: Create-time inheritance Andreas Gruenbacher <andreas.gruenbacher@gmail.com> - 2015-07-22 15:10 +0200
  [PATCH v5 33/39] ext4: Don't allow unmapped identifiers in richacls Andreas Gruenbacher <andreas.gruenbacher@gmail.com> - 2015-07-22 15:10 +0200
  [PATCH v5 36/39] nfs: Fix GETATTR bitmap verification Andreas Gruenbacher <andreas.gruenbacher@gmail.com> - 2015-07-22 15:10 +0200
  [PATCH v5 13/39] richacl: Check if an acl is equivalent to a file mode Andreas Gruenbacher <andreas.gruenbacher@gmail.com> - 2015-07-22 15:10 +0200
  [PATCH v5 15/39] richacl: Automatic Inheritance Andreas Gruenbacher <andreas.gruenbacher@gmail.com> - 2015-07-22 15:20 +0200
  [PATCH v5 18/39] ext4: Add richacl support Andreas Gruenbacher <andreas.gruenbacher@gmail.com> - 2015-07-22 15:20 +0200
  [PATCH v5 24/39] richacl: Set the other permissions to the other mask Andreas Gruenbacher <andreas.gruenbacher@gmail.com> - 2015-07-22 15:20 +0200
  [PATCH v5 21/39] richacl: Move everyone@ aces down the acl Andreas Gruenbacher <andreas.gruenbacher@gmail.com> - 2015-07-22 15:20 +0200
  [PATCH v5 19/39] ext4: Add richacl feature flag Andreas Gruenbacher <andreas.gruenbacher@gmail.com> - 2015-07-22 15:20 +0200
  [PATCH v5 27/39] richacl: Create richacl from mode values Andreas Gruenbacher <andreas.gruenbacher@gmail.com> - 2015-07-22 15:20 +0200
  [PATCH v5 31/39] nfsd: Add support for the v4.1 dacl attribute Andreas Gruenbacher <andreas.gruenbacher@gmail.com> - 2015-07-22 15:20 +0200
  [PATCH v5 22/39] richacl: Propagate everyone@ permissions to other aces Andreas Gruenbacher <andreas.gruenbacher@gmail.com> - 2015-07-22 15:20 +0200
  [PATCH v5 17/39] vfs: Add richacl permission checking Andreas Gruenbacher <andreas.gruenbacher@gmail.com> - 2015-07-22 15:20 +0200
  [PATCH v5 26/39] richacl: Apply the file masks to a richacl Andreas Gruenbacher <andreas.gruenbacher@gmail.com> - 2015-07-22 15:20 +0200
  [PATCH v5 32/39] richacl: Add support for unmapped identifiers Andreas Gruenbacher <andreas.gruenbacher@gmail.com> - 2015-07-22 15:20 +0200
  [PATCH v5 20/39] richacl: acl editing helper functions Andreas Gruenbacher <andreas.gruenbacher@gmail.com> - 2015-07-22 15:20 +0200
  [PATCH v5 23/39] richacl: Set the owner permissions to the owner mask Andreas Gruenbacher <andreas.gruenbacher@gmail.com> - 2015-07-22 15:20 +0200
  [PATCH v5 25/39] richacl: Isolate the owner and group classes Andreas Gruenbacher <andreas.gruenbacher@gmail.com> - 2015-07-22 15:20 +0200
  [PATCH v5 08/39] richacl: Compute maximum file masks from an acl Andreas Gruenbacher <andreas.gruenbacher@gmail.com> - 2015-07-22 15:30 +0200
  [PATCH v5 02/39] vfs: Add MAY_CREATE_FILE and MAY_CREATE_DIR permission flags Andreas Gruenbacher <andreas.gruenbacher@gmail.com> - 2015-07-22 15:30 +0200
  [PATCH v5 03/39] vfs: Add MAY_DELETE_SELF and MAY_DELETE_CHILD permission flags Andreas Gruenbacher <andreas.gruenbacher@gmail.com> - 2015-07-22 15:30 +0200
  [PATCH v5 01/39] vfs: Add IS_ACL() and IS_RICHACL() tests Andreas Gruenbacher <andreas.gruenbacher@gmail.com> - 2015-07-22 15:30 +0200
  [PATCH v5 11/39] vfs: Cache base_acl objects in inodes Andreas Gruenbacher <andreas.gruenbacher@gmail.com> - 2015-07-22 15:30 +0200
  [PATCH v5 05/39] vfs: Add permission flags for setting file attributes Andreas Gruenbacher <andreas.gruenbacher@gmail.com> - 2015-07-22 15:30 +0200
  [PATCH v5 12/39] vfs: Cache richacl in struct inode Andreas Gruenbacher <andreas.gruenbacher@gmail.com> - 2015-07-22 15:30 +0200
  [PATCH v5 07/39] richacl: Permission mapping functions Andreas Gruenbacher <andreas.gruenbacher@gmail.com> - 2015-07-22 15:30 +0200
  [PATCH v5 04/39] vfs: Make the inode passed to inode_change_ok non-const Andreas Gruenbacher <andreas.gruenbacher@gmail.com> - 2015-07-22 15:30 +0200
  [PATCH v5 16/39] richacl: xattr mapping functions Andreas Gruenbacher <andreas.gruenbacher@gmail.com> - 2015-07-22 15:30 +0200
  [PATCH v5 09/39] richacl: Update the file masks in chmod() Andreas Gruenbacher <andreas.gruenbacher@gmail.com> - 2015-07-22 15:30 +0200

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