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From: Andreas Gruenbacher <agruenba@redhat.com>
To: Alexander Viro <viro@zeniv.linux.org.uk>,
	"Theodore Ts'o" <tytso@mit.edu>,
	Andreas Dilger <adilger.kernel@dilger.ca>,
	"J. Bruce Fields" <bfields@fieldses.org>,
	Jeff Layton <jlayton@poochiereds.net>,
	Trond Myklebust <trond.myklebust@primarydata.com>,
	Anna Schumaker <anna.schumaker@netapp.com>,
	linux-ext4@vger.kernel.org, linux-kernel@vger.kernel.org,
	linux-fsdevel@vger.kernel.org, linux-nfs@vger.kernel.org,
	linux-api@vger.kernel.org
Subject: [PATCH v8 10/41] richacl: Permission check algorithm
Date: Mon, 28 Sep 2015 00:09:01 +0200	[thread overview]
Message-ID: <1443391772-10171-11-git-send-email-agruenba@redhat.com> (raw)
In-Reply-To: <1443391772-10171-1-git-send-email-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>
Reviewed-by: "J. Bruce Fields" <bfields@fieldses.org>
---
 fs/Makefile             |   2 +-
 fs/richacl_inode.c      | 148 ++++++++++++++++++++++++++++++++++++++++++++++++
 include/linux/richacl.h |   3 +
 3 files changed, 152 insertions(+), 1 deletion(-)
 create mode 100644 fs/richacl_inode.c

diff --git a/fs/Makefile b/fs/Makefile
index fe3e9dd..ec665fd 100644
--- a/fs/Makefile
+++ b/fs/Makefile
@@ -49,7 +49,7 @@ 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..54e899d
--- /dev/null
+++ b/fs/richacl_inode.c
@@ -0,0 +1,148 @@
+/*
+ * 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 ((acl->a_flags & RICHACL_WRITE_THROUGH) &&
+		    uid_eq(current_fsuid(), inode->i_uid)) {
+			denied = requested & ~acl->a_owner_mask;
+			goto out;
+		}
+	} else {
+		/*
+		 * When the acl is not masked, there is no need to determine if
+		 * the process is in the group class and we can break out
+		 * earlier of the loop below.
+		 */
+		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;
+			goto entry_matches_owner;
+		} 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;
+			goto entry_matches_owner;
+		} else if (richace_is_unix_group(ace)) {
+			if (!in_group_p(ace->e_id.gid))
+				continue;
+		} else
+			goto entry_matches_everyone;
+
+		/*
+		 * Apply the group file mask to entries other than owner@ and
+		 * everyone@ or user entries matching the owner.  This ensures
+		 * that we grant the same permissions as the acl computed by
+		 * richacl_apply_masks().
+		 *
+		 * Without this restriction, the following richacl would grant
+		 * rw access to processes which are both the owner and in the
+		 * owning group, but not to other users in the owning group,
+		 * which could not be represented without masks:
+		 *
+		 *  owner:rw::mask
+		 *  group@:rw::allow
+		 */
+		if ((acl->a_flags & RICHACL_MASKED) && richace_is_allow(ace))
+			ace_mask &= acl->a_group_mask;
+
+entry_matches_owner:
+		/* 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 (uid_eq(current_fsuid(), inode->i_uid))
+			denied |= requested & ~acl->a_owner_mask;
+		else if (in_owner_or_group_class)
+			denied |= requested & ~acl->a_group_mask;
+		else {
+			if (acl->a_flags & RICHACL_WRITE_THROUGH)
+				denied = requested & ~acl->a_other_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 e00f313..9768eeb 100644
--- a/include/linux/richacl.h
+++ b/include/linux/richacl.h
@@ -300,4 +300,7 @@ extern unsigned int richacl_want_to_mask(unsigned int);
 extern void richacl_compute_max_masks(struct richacl *);
 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


  parent reply	other threads:[~2015-09-27 22:10 UTC|newest]

Thread overview: 68+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2015-09-27 22:08 [PATCH v8 00/41] Richacls Andreas Gruenbacher
2015-09-27 22:08 ` [PATCH v8 01/41] vfs: Add IS_ACL() and IS_RICHACL() tests Andreas Gruenbacher
2015-09-27 22:08 ` [PATCH v8 02/41] vfs: Add MAY_CREATE_FILE and MAY_CREATE_DIR permission flags Andreas Gruenbacher
2015-09-27 22:08 ` [PATCH v8 03/41] vfs: Add MAY_DELETE_SELF and MAY_DELETE_CHILD " Andreas Gruenbacher
2015-09-27 22:08 ` [PATCH v8 04/41] vfs: Make the inode passed to inode_change_ok non-const Andreas Gruenbacher
2015-09-27 22:08 ` [PATCH v8 05/41] vfs: Add permission flags for setting file attributes Andreas Gruenbacher
2015-09-27 22:08 ` [PATCH v8 06/41] richacl: In-memory representation and helper functions Andreas Gruenbacher
2015-09-27 22:08 ` [PATCH v8 07/41] richacl: Permission mapping functions Andreas Gruenbacher
2015-09-27 22:08 ` [PATCH v8 08/41] richacl: Compute maximum file masks from an acl Andreas Gruenbacher
2015-09-27 22:09 ` [PATCH v8 09/41] richacl: Update the file masks in chmod() Andreas Gruenbacher
2015-09-28 15:28   ` J. Bruce Fields
2015-09-28 23:42     ` Andreas Gruenbacher
2015-09-27 22:09 ` Andreas Gruenbacher [this message]
2015-09-28 16:08   ` [PATCH v8 10/41] richacl: Permission check algorithm J. Bruce Fields
2015-09-28 16:25     ` Andreas Grünbacher
2015-09-28 16:29       ` J. Bruce Fields
2015-09-28 16:51         ` Andreas Grünbacher
2015-09-27 22:09 ` [PATCH v8 11/41] vfs: Cache base_acl objects in inodes Andreas Gruenbacher
2015-09-27 22:09 ` [PATCH v8 12/41] vfs: Cache richacl in struct inode Andreas Gruenbacher
2015-09-27 22:09 ` [PATCH v8 13/41] richacl: Check if an acl is equivalent to a file mode Andreas Gruenbacher
2015-09-27 22:09 ` [PATCH v8 14/41] richacl: Create-time inheritance Andreas Gruenbacher
2015-09-27 22:09 ` [PATCH v8 15/41] richacl: Automatic Inheritance Andreas Gruenbacher
2015-09-27 22:09 ` [PATCH v8 16/41] richacl: xattr mapping functions Andreas Gruenbacher
2015-09-27 22:09 ` [PATCH v8 17/41] vfs: Add richacl permission checking Andreas Gruenbacher
2015-09-27 22:09 ` [PATCH v8 18/41] ext4: Add richacl support Andreas Gruenbacher
2015-09-27 22:09 ` [PATCH v8 19/41] ext4: Add richacl feature flag Andreas Gruenbacher
2015-09-27 22:09 ` [PATCH v8 20/41] richacl: acl editing helper functions Andreas Gruenbacher
2015-09-27 22:09 ` [PATCH v8 21/41] richacl: Move everyone@ aces down the acl Andreas Gruenbacher
2015-09-27 22:09 ` [PATCH v8 22/41] richacl: Propagate everyone@ permissions to other aces Andreas Gruenbacher
2015-09-27 22:09 ` [PATCH v8 23/41] richacl: Set the owner permissions to the owner mask Andreas Gruenbacher
2015-09-27 22:09 ` [PATCH v8 24/41] richacl: Set the other permissions to the other mask Andreas Gruenbacher
2015-09-27 22:09 ` [PATCH v8 25/41] richacl: Isolate the owner and group classes Andreas Gruenbacher
2015-09-27 22:09 ` [PATCH v8 26/41] richacl: Apply the file masks to a richacl Andreas Gruenbacher
2015-09-27 22:09 ` [PATCH v8 27/41] richacl: Create richacl from mode values Andreas Gruenbacher
2015-09-27 22:09 ` [PATCH v8 28/41] nfsd: Keep list of acls to dispose of in compoundargs Andreas Gruenbacher
2015-09-27 22:09 ` [PATCH v8 29/41] nfsd: Use richacls as internal acl representation Andreas Gruenbacher
2015-09-27 22:09 ` [PATCH v8 30/41] nfsd: Add richacl support Andreas Gruenbacher
2015-09-27 22:09 ` [PATCH v8 31/41] nfsd: Add support for the v4.1 dacl attribute Andreas Gruenbacher
2015-09-27 22:09 ` [PATCH v8 32/41] nfsd: Add support for the MAY_CREATE_{FILE,DIR} permissions Andreas Gruenbacher
2015-09-27 22:09 ` [PATCH v8 33/41] richacl: Add support for unmapped identifiers Andreas Gruenbacher
2015-09-27 22:09 ` [PATCH v8 34/41] ext4: Don't allow unmapped identifiers in richacls Andreas Gruenbacher
2015-09-27 22:09 ` [PATCH v8 35/41] sunrpc: Allow to demand-allocate pages to encode into Andreas Gruenbacher
2015-09-27 22:09 ` [PATCH v8 36/41] sunrpc: Add xdr_init_encode_pages Andreas Gruenbacher
2015-09-27 22:09 ` [PATCH v8 37/41] nfs: Fix GETATTR bitmap verification Andreas Gruenbacher
2015-09-27 22:09 ` [PATCH v8 38/41] nfs: Remove unused xdr page offsets in getacl/setacl arguments Andreas Gruenbacher
2015-09-27 22:09 ` [PATCH v8 39/41] nfs: Add richacl support Andreas Gruenbacher
2015-09-27 22:09 ` [PATCH v8 40/41] nfs: Add support for the v4.1 dacl attribute Andreas Gruenbacher
2015-09-27 22:09 ` [PATCH v8 41/41] richacl: uapi header split Andreas Gruenbacher
2015-09-28 16:35 ` [PATCH v8 00/41] Richacls J. Bruce Fields
2015-09-28 17:10   ` Andreas Grünbacher
2015-09-28 17:46     ` J. Bruce Fields
2015-09-29 14:54       ` Andreas Grünbacher
2015-10-16 18:12         ` Andreas Gruenbacher
2015-10-04  6:23 ` Christoph Hellwig
2015-10-05 18:45   ` Andreas Gruenbacher
2015-10-05 18:58     ` Austin S Hemmelgarn
2015-10-06  9:49       ` Christoph Hellwig
2015-10-06 13:12         ` Andreas Gruenbacher
2015-10-06 20:26           ` Andreas Dilger
2015-10-06 20:55             ` Steve French
2015-10-07  7:50             ` Christoph Hellwig
2015-10-07 13:38               ` Andreas Gruenbacher
2015-10-07 15:15                 ` Steve French
2015-10-05 21:17     ` Dave Chinner
2015-10-05 22:01       ` Andreas Gruenbacher
2015-10-06  1:20         ` Dave Chinner
2015-10-06  9:49   ` James Morris
2015-10-06 12:24     ` Andreas Grünbacher

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